1. INTRODUCTION:

1.1 Regenerative medicine:

Regenerative medicine is a new field of medicine that involves different techniques to develop, restore or replacement of injured or diseased organs and their tissues. Regenerative medicine involves the production and use of stem cells having therapeutic importance including tissue engineering process for the generation of artificial organs [1]. It deals with the translational research by replacing or restoring human tissues or organs to establish their normal functions. It stimulates the internal healing pathways of body to repair the irrepairable tissues or organs.

It is relatively a new field that bring the experts of various fields including biology, chemistry, computer science, engineering, genetics, medicines, robotics for the purpose of making a decisions on most challenging medicinal problems faced by the humans. The main aim of this technique is to get a solution to treat the not curable pathological conditions. simply states “life is regenerative”. [1] It focus on the pathological targets to treat human diseases by replace the damaged and worn out tissues or cells generated from stem cells or engineered biological materials [2]. Regenerative medicine tends to provide: renewable source of cells, alternative to organ transplantation, tissue patches that can restore organ function when transplanted back into body and establish normal functioning of body.

2. Stem Cells ‘A New Medical Invention’:

Stem cell biology is a relatively new branch that traverses the individual characteristic features and medical outcomes of the different types of pluripotent cells that serves as the originator of more differentiated cell types as shown in fig. 1.

Fig. 1: Stem cell differentiation into different types of cells

They are basic building blocks of any living being. There are about 220 types of cells in our body [3]. Alongwith possible curative properties of patient’s stem cells can also provide disease models and a means to test drug effectiveness. The natural lifecycle process of a being starts from just one cell-the fused ova and generally referred as ‘mother cell” of all the available cells that developed inside the body. All the eukaryotic organisms have stem cells (SC) and these cells undergo regular division and differentiation into variety of important cell types that have a capability of self renewing for regenerate into new cells for body’s growth. In many of the tissues these cells serving as a body’s internal healing system by undergoes division and proliferation to nourish other cells. During the division of stem cell, it may either remain as a stem cell or divide into different type of cell having specialized function in the body, such as myocytes, erythrocytes, or a cell of nervous system. Stem cells have also long-term self-rejuvenation property and capacity to give rise to different cell types of differentiated progeny. Advancements in the field of stem cell have been a key to treatment of patients. The ideal scientific outcome is to eradicate cancer at the level of stem cells [4]. Stem cells possess special characterized features of self regenerating, unspecialized nature and differentiation for long period of time. They can replicate many times, or proliferate. Stem cells are lacking with cell specific structures and regarded as unspecialized cells but they undergo the differentiation process in which they give rise to specialized cells having tissue sensitive properties [5, 6]. During the differentiation process, cells usually undergo through variety of pathways to become more specific at every step. Stem cell undergo asymmetric division to produce the different types of cell that develop into an adult organisms. Asymmetric division occurs in all developing systems where stem cells need to proliferate and produce different cell types simultaneously [7]. Stem cells are rare in some tissues, because of which their identification and purification has to be done carefully by knowing their properties. Clinical stem cell advancement requires an enormous potential to contribute the understanding of fundamental human biology. Because of their differentiation property, they have wide applications in the prophylaxis and treatment of different pathological conditions. Research in the field of Stem cell gives an idea about the growth and development of an organism throughout the whole life cycle. Human keratinocytes are used in tissue engineering to repair skin tissue have wide range of clinical applications [8]. Recent studies show that embryonic and adult stem cells have a potential in the characterization of markers to originate of human cancer cells [9]. The promise of stem cell-based therapy for advancement of research in regenerative medicine has stimulated a real number of clinical trials, particularly for previously untreatable diseases [10]. Transplantation of stem cells using a cell replacement techniques or gene delivery through vector having a wide potential in the treatment of Alzheimer’s disease in which neurodegeneration occurs [11], Parkinson’s disease, Huntington’s chorea, HIV-associated dementia, multiple sclerosis, amyotrophic lateral sclerosis, and glaucoma caused by different mechanisms [12,13,14]. Bone marrow derived pluripotent stem cells hold a great promise for therapeutic repair of injured central nervous system. Nowadays various nutraceuticals are used that enhances the growth and proliferation of endogeneous stem cells. Stem cells are pluripotent, self-regenerating and colony forming cells having an ability to replace necrotic or damaged cardiac muscle cells, fibroblasts and cells of endothelium by translineage commitment or cell fusion [15]. Stem cell therapy holds a great promise for the repair of injured tissues and organsand organs. Stem cells undergo self-renewal and differentiation process into one or more cell types, & are found in adult and embryonic tissues and have potential uses in therapies designed to repair and regenerate organs. Recently, human adult stem cells have been developed as important tools for several cell-based therapies, some of which include tissue engineering approaches. The branch of stem cell biology is rapidly integrating with the aid of clinical trials. Distribution of stem cell is orientated and directed movement of cells toward specific stimuli. Adult stem cells have importance in pre-clinical models of ischemic conditions and myocardial infarction [16]. Stem cell therapy is an amazing modern medical advancement that goes straight to the source of the problem and treats various disorders [17].

3. Potency of Stem Cells:

Potency is referred as a capacity to differentiate and producing a mature cell type [18]. Stem cell potency signifies its differentiation potential i.e., potential to differentiate into different cell types.

3.1 Totipotent stem cells have an ability to differentiate into embryonic and extraembryonic cell types. They can build a whole and viable organism. These cells are produced from the fertilization process between ova and sperm cell. The fertilized egg undergoes first few divisions and form totipotent cells. Totipotent stem cells may produce somatic stem/progenitor cells and primitive germ- line stem cells [19].

3.2 Pluripotent stem cells:

are the offspring of Totipotent cells and they have an ability to differentiate into almost all cells, such as cells obtained from any of the three germ layers. These pluripotent cells having a characteristic features like self-renewal and a dividing into all cell types of an adult individual [20]. They are known as true stem cells, with the potency to regenerate into different cell in the body. Embryonic Stem Cells come under this category. Human pluripotent stem cells are having a wide importance in the in-vitro embryogenesis studies.

3.3 Multipotent stem cells:

Are true stem cells that can differentiate into more than one cell type, but differentiation is restricted to only closely related family of cells types. For example, multipotent stem present in the bone marrow cells can only give rise to all blood cells. Adult Haematopoeitic stem cells are an example of multipotent stem cells and they can form multiple blood cell lineages. Adipose tissue is a source of multipotent stem cells [21].

3.4 Oligopotent stem cells:

Can converted into limited cells types, such as lymphoid or myeloid stem cells. The corneal epithelium present in these types of cells is a squamous epithelium [22] that is persistently renewing and is oligopotent.

3.5 Unipotent cells:

can generate only one type of cell but have a potency of self-regeneration that makes them different from non-stem cells. Such Unipotent cells include muscle stem cells. Because of the presence of unipotent progenitor cells, most of the cells of epithelial tissues undergoing self-renewal process throughout the life of an adult [23].

4. Identification, Isolation, and Derivation of stem cells

4.1 Resident Stem Cells:

The resident stem cells remains indefinable. Initially stem cells were regarded as non specific cells with an ability of nondividing that provide a regeneration source for skin, intestine, and blood cells throughout the entire life cycle. Nowadays, these resident stem cells are recognized in different types of organs including epithelia of the skin and digestive tract, bone marrow, blood vessels, central nervous system, skeletal muscles, liver, testes, and pancreas, based upon their specific locations, morphology, and biochemical markers [24].

4.2 Isolated Stem Cells-:

Unambiguous recognition of stem cells greatly requires the isolation and refinement of cells, generally done on a basis of a combination techniques involves in the specific markers present on the surface of the cell. These separated stem cells for example hematopoietic stem (HSC) cells used in bone marrow transplantation process. However, isolation in the large quantities gets difficult because of the absence of specific markers on the surface of other types of cell. [25]. This confront has been moderately seen in the preclinical studies by marking the different cell types using genetic engineering techniques with a dye known as green fluorescence protein driven by the cell specific promoters. On the other hand, recognized stem cells have been isolated as a side population (SPC) cells using different tissues with the help of Hoechst 33342 staining dye that involves the principle of fluorescence-activated cell organization. Though, the SPC phenotype should be used with caution as it may not be function for stem cells [26].

4.3 Cultured Stem Cell:

In vitro culturing and expansion of stem cell is required to obtain a sufficient mass for the purpose of examination of potential therapeutic use [27]. Whereas in the in -vitro derivation of the stem cell has been a major barrier in the field of stem cell biology. The number of cultured stem cells and their type has elevated gradually. The cultured stem cells which are obtained from resident stem cells are known as adult stem cells and this distinguishes them from embryonic stem (ES) and embryonic germ (EG) cells [28]. However, the stem cells which are derived from embryo are the trophoblast stem (TS) cells and these includes neural stem cells, it is more appropriate to use the term tissue stem cells. Cultured stem cells can be obtained successfully by identifying the essential growth factors and culture conditions that mimics the microenvironment around the cultured stem cell types [29]. For example the derivation of mouse TS cells, once considered impossible, became possible by using FGF4 a ligand recognized to be expressed by the cells adjacent to the developing trophoblast in vivo. Therefore, it may be possible to culture other resident or isolated stem cells [30].

4.4 Self –Renewal and Proliferation of stem cells:

4.4.1 Symmetric and Asymmetric Cell Division:

Stem cell having a unique property to generate unchanged specialized daughter cell types is the highly accepted definition for them [31]. Self renewal can be obtained by one of these two mechanisms: Asymmetric cell division produces one daughter cell that is identical to the parental cells and one daughter cell that is different from the parental cell and is a progenitor or differentiated cell. Asymmetric cell division does not helpful in elevation of stem cell number. Stem cells should be dividing symmetrically to proliferate in vitro. Self renewal alone cannot define stem cells, because any established cell line, for example HeLa cells or NIH3T3 cells, proliferate by symmetrical cell division [32]. Resident stem cells are frequently dormant cells and having a capacity to divide uncommonly. Once the successful culturing of stem cells done in vitro, then they are able to divide continuously and proliferate greater than their normal range of proliferation throughout the adult life cycle. These features are primarily seen in the ES cells [33].

4.4.2 Stability of genotype and phenotype:

Proliferate capacity of stem cell is directly related to the abnormalities and mutations in their chromosomes. Mouse ES cells are highly susceptible to undergo mutation when they are cultured for a long period of time, although have been extensively used to produce the gene targeted animals and are considered in contrast to human ES cells, as they are able to retain the euploid karyotype and integrity in their genome. Formation of the tumors after transplantation process is another hurdle in this process. Mouse ES cells have an ability to form can form teratomas tumor when injected to an immunosuppressed animals [34].

4.5 Potency and Differentiation of Stem Cells:

4.5.1 Developmental Potency:

Potency of stem cell is to divide into specialized cell types. The current lack of knowledge about the molecular nature of potency requires the experimental manipulations of stem cells to demonstrate their potency. Stem cells injected in vivo into blastocysts or immunocompromised adult mice are useful in detecting the total number of formed cell types from the injected cells. The in vivo assays are not applicable to human stem cells [35].

4.5.2 From Totipotency to Unipotency:

Totipotent cells with fertilized egg alone may have an ability to produce the whole organism. Multipotent cells can produce multiple cell lineages but almost all body’s cells lines including the gem cells can be generated by pluripotent stem cells. Oligopotent cells in some cases are known as precursor cells and can form more than one cell lineage [36]. Unipotent or monopotent cells that include spermatogonial stem cells can form a single differentiated cell lineage. Terminally differentiated cell, such as fibroblast cells, also have a capacity to proliferate but maintain the same cell type and are not, therefore, considered unipotent cells.

4.5.3 Stem cell Plasticity or Transdifferentiation:

The prototype of branch of science deals with the development process of body is that cells having with the dividing property are not stable in nature. However, data from the number of study reports tell about multipotent stem cell lines that are bounded to their lineage, having a capacity to divide outside their restriction bounded lineage and the whole process is known as transdifferentiation [37]. For example HS cells may be converted into neurons and also into germ cells. This mechanism defines the importance of patient derived somatic stem cell directly for the therapeutic indication by removing the requirement of stem cell of embryonic origin [38].

4.5.4 Directed differentiation of stem cells:

Pluripotent stem cells having ability to convert into multiple cell types, but in culture they normally differentiate into heterogeneous cell population in a random manner. On the other hand, for therapeutic indication it is advantageous to directed stem cells into specialized cell types that include insulin-secreting beta cells. This area is considered as active research for stem cells with developed protocols. Phenotypic characteristics of cell should be critically evaluated to undergo the differentiation process. Interestingly, it has been stated that mouse ES cells can divide in vitro into oocytes and sperm, with a capacity of fertilizing an oocytes to produce live offspring [39].

6.2 Mesenchymal Stem Cells (MSC):

These cells support tissue repair, immune stimulation, and hematopoietic stem cells engraftment. These cells also have the capacity to treat heart attack, stroke and cartilage repair. MSCs are known as mesenchymal stromal cells, are a subset of non-hematopoietic adult stem cells that originate from the mesoderm. They are having an ability of self regeneration, renewal and undergo division into multicellular cell lines including mesoderm, ectodermic and endodermic. Bone marrow, adipose tissue, umbilical cord, fetal liver are the rich source of their isolation. The large number of clinical trials on MSCs has been carried out in 2004 and many countries involves in the usage of these type of cells that leading the way numerous scientific issues remain to be resolved before the establishment of clinical standards and governmental regulations [51].

6.3 Epithelial Stem Cells (ESC):

These cells support wound healing and soft tissue repair. They also have the potential to treat diabetes, burns, ulcers and radiation wounds. Damaged cells of animals are regularly replaced by ESC throughout the life cycle. The process of homeostasis is maintained by stem cells and is required for the development and growth of adult tissues. In their normal environment, transiently amplifying (TA) progeny of stem cells will divide actively for a restricted period of time to make the tissue [52].

6.4 Non hematopoietic Multipotent Stem Cells (NHMSC):

They can differentiate into many types of cell lines which have specific function such as cells of heart, lungs, liver, brain etc [53].

6.5 Umbilical cord Matrix Stem Cells (UCMSC): They are derived from Wharton’s Jelly umbilical cord of human. These cells have survival properties, they are capable of making ectoderm and mesoderm derived cells, they help in prevention of neurodegeneration in Parkinson’s disease. These can be induced in- vitro that showing biological, chemical and neuronal morphological features [54]. Umbilical cord consists of cord blood and tissues that are differentiated in Table.2

Table 2- Umbilical Cord blood stem cells (UCBSC) versus Umbilical cord blood tissue stem cells (UCBTSC)

Cord Blood	Cord Tissue
Cord blood is a very rich source of stem cells. This blood is in the placenta and UC blood vessels after the child birth.	Cord tissue is the jelly like substance that fills UC around the blood vessels, protects the baby before birth.
Cord blood is taken immediately after birth from the UC. It is fast and painless process for both the mother and the baby. After collecting, it is send to storage facilities.	A segment of UC approximately 4-6 inch in length is cut after taking out the blood from the detected UC. This process is also fast and painless. After taking the cord segment, it is send to storage facilities.
Cord blood contains HSC and forms blood related cells in the body.	Cord tissues contain MHC and develop into structural and connective tissue.
Cord blood stem cells having a capability to treat blood related diseases and cancers such as leukemia, anemia and autoimmune diseases.	Cord tissue stem cells are used to repair bone, cartilage tissues and help in repairing damaged connective tissue. In future it may used in the treat injury of spiral cord and stroke conditions.
The first clinical trial of cord blood was in 1988. It has now been used to treat 80 blood related diseases.	The first clinical trial of cord tissue was carried out in 1995.

7. Disease- Specific Stem Cell Approaches:

7.1 Ischemic Heart Disease and Cardiomyocytes Regeneration :

Because of the high prevalence of ischemic disease extensive efforts have been devoted to cell replacement of cardiomyocytes. Previously, heart of an adult has been considered as a terminally differentiated organ without the capacity for regeneration. However heart has the ability to achieve low levels of cardiomyocytes regeneration alongwith revascularization. This regeneration is likely accomplished by cardiac stem cell resident in the heart and possibly by cells originating the bone marrow. If such cells could be characterized, isolated and amplified ex vivo, they might provide an ideal source of stem cells for therapeutic use. For effective myocardial repair, cell must be delivered either systematically or locally, and the cell must survive engraft and divided into functional cardiomyocytes [55]. That couple automatically and electrically with the recipient myocardial. An optimal cell delivery method is still unclear, and different in vitro-in vivo studies have employed intramyocardial, transendocardial, intravenous, and intracoronary injections. In experimental myocardial infarction, functional improvements have been achieved after transplantation of different types of cells including ES cells, bone marrow stem cell, endothelial stem cells and adipose stem cells. Bone marrow stem cells particular have been examined in clinical trials of human ischemic heart disease. These have largely been small, nonrandomized studies that typically combined cell treatment with conventional therapies. Although the fate of the cells and mechanisms by which they altered cardiac functions are open questions, these studies have shown small but measurable improvements in cardiac functions and, in some cases, reduction in infarct size. The preponderance of evident suggests that functional benefits are not derived from direct generation of cardiomyocytes but rather from indirect effects of stem cells on resident cells [56]. This may reflect the release of soluble growth factors, induction of angiogenesis, or some other mechanisms.

7.2 Diabetes Mellitus:

The success of islet cells and pancreas transplantation provide proof of concept for a cell based approach for type 1 diabetes. Although, the requirement for donor pancreata are at great distant from the available number, and preservation of long-term survival of graft is also a great hurdle. The search for a renewable source of stem cells capable of regenerating pancreatic islets has therefore been extensive.

Pancreatic beta cells turnover occur in the normal pancreas, although the source of the new beta cells are controversial. Attempts to enhance endogenous regenerative processes have not been yet successful, but this remains a potentially viable approach [57]. Different cell types are used as a candidate for stem cell replacement, including ES cells, hepatic progenitor cells, pancreatic ductal cells, and bone marrow stem cells. Successful therapy will develop on developing a source of cells that can be amplified and have the capability to synthesize, store and release the insulin when it is required, primarily, in regard to changes in glucose level. Stem cells that have been replaced, their proliferative capacity is highly regulated to circumvent excessive expansion of beta cells numbers with the consequent development of hyperinsulinemia, and the cells must avoid immune rejection. Although the ES cells are divided into cells that produce insulin, these cells have relatively low content of insulin, and a high rate of apoptosis, and they generally lack the capacity to normalize blood glucose in diabetic animals. Thus, ES cells have not been yet useful for the large scale production of differentiated islet cells [58].

During the process of embryo formation, the pancreas, liver and gastrointestinal track cells are derived from the anterior endoderm and in certain pathological conditions, transdifferentiation phenomenon of the pancreas to liver and vice versa have been observed. Multipotential stem cells stored within the gastric glands and intestinal crypts. Thus, hepatic, pancreatic, and gastrointestinal precursor cells may be candidates for cell-based therapy diabetes.

7.3 Liver:

Currently, the only successful treatment for end stage liver diseases is transplantation process, but this approach is limited by the shortage of liver grafts. Clinical trials of hepatocyte transplantation demonstrate that it can potentially substitute for organ transplantation, but lack of available cells also limits this strategy. Potential sources of stem cells include endogenous liver stem cell such as oval cells, ES cells, bone marrow cells, and umbilical cord blood cells [59]. However, in vitro and in vivo studies suggested that bone marrow stem cell that are transplanted can generate hepatocytes, this phenomenon largely reflects the fusion of the transplanted cells with endogenous liver cells, giving the erroneous appearance of new hepatocytes. ES cells have been divided into hepatocytes and transplanted in animal models of hepatic failure without formation of teratomas.

7.4 Nervous System:

Neural cells have been differentiated from a variety of stem cell populations [60]. Human ES cells are injected to generate neural stem cells, and these cells give rise to neurons, oligodendroglia, and astrocytes [61]. Transplantation of the neural stem cells into the rodent brain is carried out with the formation of appropriate cell types and no tumor formation. Multipotent stem cell present in the adult brain can also generate all of the major neural cell types, but highly invasive procedures would be necessary to obtain autologous cells. An alternative is the neural stem cells of fetus obtained from miscarriages. Bone marrow and adipose stem transdifferentiation into neural stem cells and vice versa, have been reported, and clinical trials of such cells have begun for different types of neuronal disorders. Clinical trials of a conditionally immortalized human cells use and of human umbilical cord blood cells in stroke are also planned. Neurologic disorders that have already been targeted for cell therapies include spinal cord injury, amyotrophic lateral sclerosis, stroke, traumatic brain injury, Batten and Parkinson’s disease [62]. In Parkinson disease, motor disfunctioning results in the loss of single cell population, neurons having dopamine in the substantia nigra. Transplantation of stem cell derived dopamine producing cells offers a number of potential advantages over fetal transplants, including the ability to engineer cells to produce factors that will enhance cell survival. Neurological dysfunctions after damage to spinal cord reflect demyelination, and both ES cells and bone marrow resulting stem cells are able to facilitate remyelination after in vitro injury to spinal cord. Clinical trials of marrow – derived stem cells have already begun, and this may be the first disease targeted for the clinical use of ES cells. Marrow derived stem cells have role in the treatment of different neurologic disorders such as stroke, amyotrophic lateral sclerosis and traumatic brain injury. At present, no population of transplanted stem cells has been shown to generate neurons that extends axons over long distances to forms synaptic connections such as would be necessary for replacement of upper motor neurons in ALS, stroke, or other disorders. Stem cell therapy involves treatment of various diseases that are shown in Table: 3 [63]

Table 3 - Diseases Treated with Stem Cell Therapy

Sr.No.

Disease

Types

Haematological Disorders

· Aplastic Anaemia (Severe)

· Fanconi Anaemia

· Paroxysmal nocturnal haemoglobinuria (PNH)

Acute Leukaemias

· Acute Lymphoblastic Leukaemia (ALL)

· Acute Myelogenous Leukaemia (AML)

· Acute Biphenotypic Leukaemia

· Acute undifferentiated Leukaemia

· Acute Myelo-monocytic Leukaemia

Chronic Leukaemia

· Chronic Myelogenous Leukaemia

· Chronic Lymphocytic Leukaemia

· Juvenile chronic Myelogenous Leukaemia

· Juvenile Myelomonocytic Leukaemia

Myeloproliferative disorders

· Acute myelofibrosis

· Agnogenic myeloid metaplasia

· Polycythaemia Vera

Lymphoproliferative disorders

· Non-Hodgkin’s lymphoma

· Hodgkin’s disease

· Prolymphocytic leukaemia

· Chronic Granulomatous disease

· Neutrophil actin deficiency

· Reticular dysgenesis

Myelodysplastic Syndromes

· Refractory Anaemia

· Refractory Anaemia with ring sideroblasts

· Refractory Anaemia with excess blasts

· Refractory anaemia with excess blasts in transformation

· Chronic myelo-monocytic leukaemia

· Beta Thalassaemia Major

· HbE Beta Thalassaemia

· Pure Red Cell Aplasia

Inherited Platelet abnormalities

· Amegakaryocytosis – I

· Congenital thrombocytopenia

· Glanzmann thromboasthenia

· Essential Thrombocythaemias

Histiocytic disorders

· Familial erythrophagocytic Lymphohistiocytosis

· Histiocytosis X

· Haemophagocytosis

Liposomal Storage Disease

· Mucopolysaccharidosis

· Hurlers Syndrome

· Hunters Syndrome

· Scheie syndrome

· Sanfillipo syndrome

· Morquio syndrome

· Macroteaux-Lamy syndrome

· Sly syndrome

· Beta Glucuronidase deficiency

· Adrenoleukodystrophy

· Mucolipidosis II

· Krabbe disease

· Gauchers disease

10.

Plasma cell disorders

· Multiple Myeloma

· Plasma cell leukaemia

· Waldenstorm’s macroglobulinemia

11.

Other Inherited disorders

· Lesch-Nyhan syndrome

· Cartilage-hair hypoplasia

· Osteopetrosis

8. Stem cells in organ system and their future:

Regenerative medicine involves the use of stem cells for the study of different organ systems and cell, including skin, eye, cartilage, bone, kidney, lung, endometrium, smooth muscles and others. In fact, the potential for stem cells regeneration of damaged organs and tissues is virtually limitless. HSCs are the only stem cells that are characterized by available specific surface markers to identification, a prerequisite for reliable clinical applications. The pathways for differentiating stem cells into specific cellular phenotypes are still unknown, the migration of transplanted cells is uncontrolled, and the response of the cells to the environment of diseased organ is unpredictable. Imaging techniques are needed to visualize stem cells in vivo after transplantation in humans. Fortunately, stem cells can be engineered before transplantation to contain contrast agents that make this feasible. The potential for tumor formation and the problems associated with immune rejections are significant impediments. Most of the available cell replacement techniques are already include vasoactive endothelial growth factors coadministration to foster vascularization, which is required for viability and functioning of the transplant. Some stem cells have been engineered to have an inducible suicide gene so that the cells can be eradicated in the event of tumor formation or some other complications [64]. The prospective for stem cell treatment to revolutionized medical care is extraordinary, and disorders such as myocardial infarction, diabetes, Parkinson’s disease and many other are attractive targets. Although, therapies based on stem cell are at a developmental stage and excellence for clinical transplantation of expected well characterized cell will be a difficult and lengthy undertaking. Recent experimental discoveries have shown that umbilical cord stem cells are useful for new therapies in treating diseases that were not curable till now and were difficult to cure. An in vitro study showed the development of new bone formation in beagle dogs with intra bone marrow injection of umbilical cord mesenchymal stem cells [65]. These cells have shown excellent results to repair the large defect peri-implant after immediate implant. Cord blood hematopoietic progenitor cell therapy have potential life saving treatments for patient suffering from inherited metabolic disorder, immune system disorder, beta-Thalassemia and certain blood cancers. Progenitors are like stem cells but less specialized cell types with capacity to differentiate into different types of blood cells when infused into patients. Hematopoietic progenitor cells can partially or fully restore blood cells and immune functions. The United States Food and Drug Administration have approved the umbilical cord blood for stem cell transplantation. One of the best treatments known today for leukemia patient is the transplantation of hematopoietic stem cell in which stem cells once transformed get multiplied but the main complication of this transplantation is graft versus host disease for patients who have only partially matched donors of stem cells and moreover this is the only hope of cure for them. For this the donated stem cells is treated before they are transplanted into the patient. Early infusion of donor T- regulatory cells prevents graft versus host diseases and enhances immune recovery in high risk blood cancer patients. Hematopoietic stem cells are mainly derived from umbilical cord stem cells and can be a potential donor for this purpose. Umbilical cord mesenchymal stem cells when harvested properly possess properties such as anti inflammatory and stimulation of immune system. These cells are not rejected by the immune system of the patients receiving it due to its unique properties. They have potential to treat multiple sclerosis and other auto immune diseases. Clinical trial for multiple sclerosis using umbilical cord stem cell therapy is performed at Transational Biosciences, a subsidiary of Medistem Panama. Wharton’s jelly of human umbilical cord is a source for Mesenchymal stem cells have great capabilities of self renewal and can differentiate into various tissues [66]. It also has immunosuppressive properties. It is therefore an excellent input product for tissue engineering process and regenerative medicine. Under feasible condition the Wharton jelly mesenchymal stem cells can differentiate into adipocytes, bone, cartilage and skeleton muscles. Now research evidence shows that stem cells differentiate into ectoderm by multi-lineage differentiation. Ectoderm can differentiate into parts of nervous system components spine, peripheral nerves, brain and exocrine glands that includes mammary, salivary, sweat and lachrymal glands [67]. Research and experimentation are being carried out for ectodermal differentiation of Wharton’s jelly mesenchymal stem cells for tissue engineering and regenerative medicine. Part of ongoing clinical trials in the U.S is shown in Table: 4

Table 4 - Part of ongoing clinical trials in the U.S

S No.

Disease under different phases of clinical trial [68, 69]

Types

Malignant Diseases

· Griscelli Syndrome

· Hodgkin's Disease

· Hemophagocytic Lymphohistiocytosis

· Hurler Disease

· Hurler-Scheie Disease

· Hypoplastic Leukemia

· I-cell Disease

Non-malignant diseases

· Congenital Cytopenia

· Polycythemia Vera

· Gaucher’s Disease

· Sandhoff Disease

· Multiple Sclerosis

· Rheumatoid Arthritis

· Cerebral palsy

I. Stem Cell Banking:

Blood from the umbilical cord of newborn and through the placenta is collected and stored for the purpose medical use through the Cord blood banking. Cord blood consists of lifesaving stem cells which are different from embryonic stem cells [70]. Umbilical cord blood is a source of hematopoietic stem and progenitor cells which are having clinical application to reconstitute the hematopoietic system and/or restore immunological function in affected individuals requiring treatment. First transplantation of cord blood was done in 1988 and till date more than 25,000 allogeneic cord blood transplantations have been performed worldwide [71]. There are two types of cord blood banking is available that include private and public banking. a) By donating baby's cord blood to a public cord blood bank for anyone who needs it. b) By paying to store the cord blood of baby in a private cord blood bank for your family's use. Cord blood stored in private banks is used for allogeneic transplantation. More than 780,000 cord blood units uses 130 private cord blood banks, worldwide, and over 400,000 units uses 100 public cord blood banks [72, 73]. All types of donors are involved in the public cord blood banks that are approved and informed consent from the parents must be needed for receiving the umbilical cord blood. After that this cord blood units would belong to the public bank use. Registration of the inventory is carried out and later on find by the public and healthcare professionals to access that information for the transplantation purposes. Private cord blood banks get blood samples from the public cord banks and then store the cord blood for usage of individual by specific families and become the child property under the guardianship of the parents. In private banks, collection and maintenance of samples are more costly [74]. Currently, greater than 780,000 units worldwide are known to store in 134 private cord blood banks [75]. According to the ‘BabyCenter Cord Blood Banking Survey’, these are parents' top five private cord blood bank choices. Statistical data shows the percentage rate of parents taking in survey who chose each bank as shown in fig. 4 [75].

9.1 Indian Scenario:

Because of high birth rate and genetic diversity in India, it has wide potential for umbilical cord blood (UCB) banking [76]. Improvement in the UCB banking has carried out with time largely due to involvement of professional organization and their publication standards. However, accreditation of these organizations remains voluntary, and in India the number of public cord band is three out of ten while the remaining are private cord banks. In India, one public and one private bank named as American Association of Blood Banks (AABB) are accredited. In 2009, the first Indian biotechnology named as ‘BabyCell’ introduced a platform of regenerative medicine in India [77]. It has achieved ISO 13485 in the very first year of operations and certified with good manufacturing practices (GMP), good laboratory practices (GLP) and good clinical practices (GCP) in its 2nd year of operations. Government agencies need to provide regulatory and safety guidelines, which is lacking in several countries. Seventy percent of total population patients in India who needed a transplantation of bone marrow do not find a match within their own family. That is why; an unrelated UCB is a greatly acceptable source of progenitors for transplantation of hematopoietic stem cell. However, till now UCB total transplantation carried in India has been very less mainly due to greater cost and restricted sources available for UCB units [78]. But with the existence of three public UCB banks these figures are estimated to improve in the nearby coming years. This will provide a better quality grafts for patients population in India [79]. To fulfill the future transplantation requirement of the country, participation from the government and establishing foundation, financial investment is the prime most things and that will ultimately enhance the cord banking in India [80].

Fig. 4: Statistical data shows the percentage rate of parents taking in survey choosing different blood bank

10. CONCLUSION:

SC therapies are the treatments of health care in the future. The best easily available stem cells known today to medical science are umbilical cord stem cells. Umbilical cord stem cells have capacity to treat multiple diseases. It is for India that advancements in the research and development of this field need to be carried out to utilize the rich sources of umbilical cord stem cells available in this country. For this capacity and capability of stem cell banking in India need to be enhanced.

11. FUTURE PERSPECTIVES:

Stem cell banking is the most important part of regenerative medicine. New private and public cord bank must be established all over India with an available knowledge research and storage facilities for the benefit of Indian population and worldwide. Indian government needs to form policy and procedure to motivate this industry. Currently, there are 30 clinical trials that use umbilical cord stem cell therapy. These trials are approved based on the positive outcomes of the previous phases. Among that clinical trials, some of them are focused on neurological conditions including spinal cord injury, hearing loss and hypoxic ischemic encephalopathy, Graft versus Host disease, rheumatoid arthritis etc., cardio vascular diseases like congenital heart disease, ischemic stroke, cardiac repair, myocardial infarction etc., inherited pathological conditions that involves HIV, Thalassemia, sickle cell etc., that require gene therapies and orthopaedic disorders. Most of these clinical trials are in Phase I and II, so the results of these various stages are not available. Most patients who underwent stem cell transplants, followed by regular health checkups and medications are found to be healthy and leading a normal life. They have witnessed an improvement in the quality of life because of the stem cell healing power. Due to all these properties stem cells are called as miracle cells and parents choose to preserve these precious stem cells of their baby through cord blood banking.

12. CONFLICT OF INTERESTS:

There are no conflicts of interest.

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Received on 29.08.2018 Modified on 12.10.2018

Research J. Pharm. and Tech 2018; 11(8): 3667-3678.

DOI: 10.5958/0974-360X.2018.00674.1

Different types of stem cells	Source/ Derivation	Maintenance and Properties
Embryonic (ES) stem cells	ES cells can be derived by culturing blastocysts or immunosurgically isolated inner cell mass from blastocysts on a feeder layer of mouse embryonic fibroblast (MEF) with leukemia inhibitory factor (LIF) or without LIF. These cells are to originate from the epiblast and grow as tightly adherent colonies multicellular features with a population doubling time of 12 hours.	They maintain a stable euploid karyotype even after extensive culture and manipulation, can differentiate into a variety of cell types in vitro, and can contribute to all cell types. They form relatively flat, compact colonies with the population doubling time of 30-40 hours.
Embryonic germ(EG) cells	They are derived by culturing the primitive germ cells from embryos at E8.5-E12.5 on a feeder layer of mouse embryonic fibroblast with leukemia inhibitory factor (LIF) and also developed by culturing the gonadal tissues from 5-11 weeks post fertilization embryo on a feeder layer of forskolin.	They have same pluripotency as ES cells but having imprinting differences in some genes.
Trophoblast (TS) stem cell	They can be derived by culturing the trophectoderm cells of E3.5 of blastocysts, extra embryonic ectoderm of E6.5 of embryo, chorionic ectoderm of E7.5 embryo on a feeder layer of MEF with FGF4.	TS cells in vitro can differentiate into trophoblast giant cells and give rise to all trophoblast subtypes when injected into the blastocysts.
Extraembryonic ectoderm cells (XEN)	XEN cells can be derived by culturing the ICM in non-ES cell culture condition.	They only form parietal endoderm lineage when inject into a blastocysts.
Embryonic carcinoma (EC) cells	They can be derived from teratocarcinoma – a type of cancer that most commonly developed into the testes.	They rarely show pluripotency in vitro, but can develop into all cell types when injected to blastocysts. They often have an aneuploid karyotype and other genome alterations.
Mesenchymal stem cells (MSC)	They are obtained from bone marrow, muscle, adipose tissues, peripheral blood, and umbilical cord.	They can divide into Mesenchymal cell types, including adipocytes, osteocytes, chondrocytes, and myocytes.
Multipotent adult stem cells (MAPC’s)	They are cultured by using the bone marrow mononuclear cells, after depleting CD45 and GlyA cells. They are very rare cells that are present within MSC cultures from postnatal bone marrow.	They can also be isolated from postnatal muscle and brain. They can be cultured for more than 120 population doublings. They can be differentiated into all tissues in vivo when injected into mouse blastocysts, and can separate into various cell lineage of mesodermal, ectodermal, and endodermal origin in vitro.
Spermatogonial stem cells (SSC)	They are derived by culturing newborn testes on STS-feeder cells with glial cell derived neurotrophic factor (GNDF).	They can reconstitute long-term spermatogenesis after transplantation into recipient testes and restore fertility.
Germline stem cells (GSS)	They can be derived from neonatal testes	They can differentiate into three germlayers in vitro and contribute to a variety of tissues, including Germline, when injected into blastocysts.
Multipotent adult Germline stem cells (maGSC)	They can be derived from adult testes.	In vitro they can differentiate into three germlayers and can give rise to the variety of tissues, including germline, which injected into blastocysts.
Neural stem cells (NSC)	They can be derived from fetal and adult brain and cultured as a heterogeneous cell population of monolayer or floating cell clusters called neurospheres.	They can divide into neuron and glia in vivo and in vitro. Recently, the culture of pure population of symmetrically dividing adherent. They require the presence of Fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF).
Unrestricted somatic stem cells (USSC)	They are the rare cells developed from newborn cord blood and from cultured single nuclear fraction of cord blood in the presence of 30% fetal calf serum (FCS) and10^-7dexamethasone.	They are having a capacity to develop into different cell types in vitro and in vivo transplantation experiments in rats, mouse, and sheep. They are CD45^- adherent cells and can be expanded to the 10^-15 cells without losing pluripotency.