A Comprehensive Review of Applications of Stem Cell Therapy

Stem cells are those cells which have the capability to develop into other different types of cells of our body like RBC, WBC etc. Most of the cells which are present in the human body are differentiated cells. Differentiated cells are those cells which pe specific function only. Recently, stem cells have been used with the therapeutic intention of regenerating damaged tissues. In the present paper we have reviewed current fundamental concepts regarding applications of stem cells in different parts o body. We have also discussed various studies which have already been conducted by different researchers on the latest applications and dimensions of stem cell therapy.


INTRODUCTION
Stem cells are those cells that haven't differentiated yet. They have the ability to divide themselves and make infinity copies of themselves. Though cells present in the human body also have replication ability but this repletion ability is only for a limited number before they begin to break down. hand, stem cell divide and they can remain as a stem cell or they can develop into other differentiated cells like liver cell muscle cell.
According to Jacquelyn Cafasso (  ific function only. For example, as we know that all human beings start out as only one cell. This cell is known as the zygote. The zygote divides by mitosis process. Then the cells begin to differentiate and perform specific functions of the ocess is known as differentiation.
Generally, there are three types of stem cells:

Induced pluripotent stem cells
Adult stem cells are basically undifferentiated cells present in our bodies. These cells renew themselves or generate new cells. Adult stem cells are also called as somatic stem cells. These cells can also repair other cells of our bodies. Hematopoietic stem cells, mesenchymal stem cells, neural stem cells, skin stem cells are the types of Embryonic stem cells are derived from the inner cell mass of an embryo at the blastocyst stage. These cells are also called as pluripotent stem cells. These cells develop into any type of cell that found during the first stage of development but not the placenta and umbilical cord. These cells are very precious because they provide renewable resources for normal development, cure diseases and for other Induced pluripotent stem cells are artificial stem cells which are created in a laboratory. These are the medium between embryonic stem cells and adult stem cell. These cells are like embryonic stem cells. Generally, these cells are tools, to learn about normal development and diseases. They are also helpful for developing and testing new drugs and therapies. The characteristics of these cells are similar to embryonic stem cells as mentioned above so that they can ultimately be used as the source of cells or tissues for medical treatment.

Background of study
In 1800, it was discovered by Robert hooke that cells are the basic unit of life and in animals and humans, some cells are present which have the ability to produce other cells (Nurse 2003). In early 1900, it was discovered that in human body some cells are present which have the ability to generate blood cell. This statement is proofed by an attempt of the fertilized mammalian egg outside the human body (Elgert 2009). In 1968, first bone marrow transplant was performed successfully (Bach, Albertini et al. 1968). In 1978, human cord blood stem cells were discovered by Dr Gregor Pindul. Human cord blood stem cells are also used as alternative source of embryonic stem cell. According to the present researchers, these are used in human stem cell therapy (Prindull and Prindull 1978).
In 1981, embryonic stem cell was identified in mice by Martin Events and first in-vitro stem cell line was developed in mice (Thomson, Itskovitz-Eldor et al. 1998). In 1988, embryonic stem cell line was discovered in a hamster (Doetschman, Williams et al. 1988). In 1995, first embryonic stem cell line was developed from a primate. In 1997, at Roslin Institute, Wilmut and his colleagues discovered dolly, the sheep which is the first artificial animal clone. To discover this animal clone, they fused a sheep egg with an udder cell (it is an organ which is formed in the mammary gland of a female having four-legged mammals) and then implanted the resulting hybrid egg into a surrogate mother sheep. Through this process, the researcher found that the similar hybrids which are made by fusing human embryonic stem cell with an adult cell from a human being can be used to develop genetically matched tissue and organs. (Nerlich, Clarke et al. 2001) In 1998, James Thomson, from early embryos isolated the cells and developed the first embryonic stem cell lines (Thomson, Itskovitz-Eldor et al. 1998). After this, John Gearhart derived the germs cells from foetal gonad tissue and from both the resources, pluripotent stem cell lines were discovered. In 1999 and 2000 it was discovered that adult stem cells can produce different types of cells like red blood cells, white blood cells etc. ( Stem cells which are collected from the umbilical cord are special. These are young, potent, and viable. A large number of clinical studies are conducted by researchers that stem cells are suitable for regeneration of damaged tissue after accidents, degenerative diseases like e.g. slipped intervertebral discs or cancer treatment. Umbilical cord blood and tissue are rich in the stem cell. These are used as an important therapeutic option in future medicine. Stem cells are used in the treatment of some serious diseases from last 55 years. These are used especially in the treatment of cancer which require the high dose of chemotherapy. The patient's own stem cells are extracted from their bone marrow or peripheral blood which are stored temporarily and transplanted into the patient after chemotherapy to reduce the side effects of chemotherapy and it also helps to regenerate the destroyed cells of patients.

Placental tissue
Placental tissues have the remarkable potential to develop into different types of cells which are present in our body during early life and growth. These tissues are used in regenerative medicines. Generally, it is observed that placental tissues have a three-layer structure. These three layers of tissues are originated from the fetus and the mother which contains a large number of cells. Donors of placental tissue are free from any physical dangers. It is necessary to match a variety of HLA types of patients and donors. Mesenchymal cells are derived from decidua i.e.DMCs (it is a uterine thick layer of the modified mucous membrane), as well as Mesenchymal cells, are also derived from bone marrow i.e. BM-MSCs. Mesenchymal cells which are derived from decidua having high proliferative fibroblast than mesenchymal cells which are derived from bone marrow. With the help of retroviral transfer of factor genes, DMCs generates the induced pluripotent stem. As we have discussed above DMCs are derived from the mother or we can say that it is derived from the maternal portion of the placenta, so these have the ethical advantages for cell banking because they can be collected with the full consent of the adult donor. They are also useful for generation of human iPS for regenerative applications. (Doucet, Ernou et al. 2005)

Therapy Targeting Stem Cell in Patients with Decompensated Cirrhosis of Liver in a Tertiary Treatment
Hepatic failure has only a curative treatment and that is liver transplantation but this curative treatment has high cost and is limited by less chances of survival. Recently, regenerative medicines have emerged with the medical sciences which deal with the functional restoration of tissues or cells or organs for the patients which suffering from severe injuries or chronic disease. In the field of stem cell research, it is found that the diseases which cannot be cured by conventional medicines these types of diseases can be cured by cell-based therapies. The special character of stem cell i.e. indefinite self-renewal and potential to differentiate into another cell, this special character represent stem cell as frontiers of regenerative medicine. The ex-vivo remodelling of stem cells grown into 3D organoids and tissue structure for personalized application due to the advancement of gene editing and tissue engineering technology. In regenerative medicines, the most recent advancements are in transplantation and tissue engineering technologies of ESCs, TSPSCs, MSCs, UCSC's, BMSCs andiPSCs. (Mahla 2016)

Adult stem cell therapy and heart failure
Heart failure is very common and highly destructive disease that causes significant morbidity and mortality. Coronary artery disease (CAD), valvular heart disease, and other cardiac disorder can cause heart failure. Stem cell regenerative medicines are the therapeutic strategy to repair or replace injured and nonviable myocardium. With the results of the inconclusive study, it is proofed that stem cell regenerative capacity and ability can improve cardiac International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470 @ IJTSRD | Available Online @ www.ijtsrd.com | Volume -2 | Issue -3 | Mar-Apr 2018 Page: 1250 functions. There are three basics mechanisms which show that stem cell therapy can be used as an effective treatment for heart failure.
1. As we have discussed above that stem cell have the ability to generate new cells, adult stem cells could generate new cardiac cells or tissues, and this process is called as cardiogenesis.
2. The second proposed mechanism is that by activating endogenous endothelial progenitor cells, (EPC) the stem cells generate vascularate via angiogenesis or vasculogenesis.
3. Only a subset of EPCs is true endothelial lineage which is capable of neovasculogenesis. Mounting evidence suggests that adult stem cells have cardioprotective factor. This secreted factor may stimulate the vascular growth and remodelling, modulate inflammation, and regulate cell differentiation and survival. According to recent studies, it is concluded that these factors form clusters of extracellular membrane vesicles which includes exosomes and microsomes than these aretransferred into proteins, lipids, RNA and micro RNA to mediate cardio protection. ( According to recent article of Times of India i.e,'functional mini-kidney' grown from stem cells."mini-kidney"-these are capable of filtering blood to produce urine. They have been grown in a living organism. This is the major steps towards treatment of kidney disease. Reaserchers have been able to develop human stem cells into mini-kidney. It is complete with functioning human blood vessels and able to filter the blood.
As biological discoveries identify key factors for stem cells survival and technological advances provide new biomatiarels, the potential for improved treatment is dramatic. In conclusion, stem cells therpy can be utilized greatly to treat and manage diseases. More studies are needed in human stem cells to understand its significance.