Stem cells are a population of unspecialized cells that give rise to specialized cells. They posses two important property- Ability to self replicate and self renewal which make them potentially useful in production or replacement of cells in the body. Cell regeneration therapy refers to the incorporation of these potent stem cells in treating patients with diseases or defects. Stem cell therapy is now being used to treat 76 disease conditions occurring in different parts of the body. Stem cells may be categorized into different types depending on their origin, they may be Embryonic stem cells (cells obtained from the blastocyst of the embryo) and adult stem cells (a group of undifferentiated cells present within the adult tissues). The use of embryonic stem cell has many ethical concerns. In the current scenario the best treatment option is to use autologous (stem cells derived from the patients own tissues) stem cells. The primary purpose of this project is to study the use of autologous adult stem cells in curing defective conditions of the heart.
The most important property of stem cell is their ability to self renew: The stem cells can undergo numerous cycles of cell division while maintaining their undifferentiated state. If the cells can replicate many times over then the process is termed as proliferation. A starting population of stem cells that proliferates for many months in the laboratory can yield millions of cells. If the resulting cells continue to be unspecialized, like the parent stem cells, the cells are said to be capable of longterm selfrenewal. Scientist are carrying out studies to determine as to how these stem cells remain unspecialized and self renewing for many years. The third property is their potency: They are capable of retaining the ability to reinvigorate themselves through mitotic cell division and can differentiate into a diverse range of specialized cell types.
Scientists are just beginning to understand the signals inside and outside cells that trigger stem cell differentiation. The internal signals are controlled by a cell's genes which are interspersed across long strands of DNA, and carry coded instructions for all the structures and functions of a cell. The external signals for cell differentiation include chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the microenvironment.
Types of Stem Cells
Stem cell may be classified in two ways, the first classification of stem cell is based on their potency, the second classification of stem cell is based on their origin.
Based on their potency:
Totipotent stem cell:
It is derived from the Latin work “totus” which means entire. They posses total potential. A totipotent stem cell can generate cells of all the three germ layers. It is formed by the fertilization of egg and a sperm. The embryo can give rise to all the 200 cell types that make up the human body, some of the cell types include nerve cells (neurons), muscle cells (myocytes), skin (epithelial cells), bone cells, cartilage cells etc. apart from giving rise to embryonic tissues, a totipotent cell can also give rise to extra embryonic tissues, the extra embryonic tissue are essential for the development of the embryo but are not incorporated into the body of the embryo example placenta and umbilical cord.
Pluripotent stem cell:
Pluri derived from latin word “plures” which means several. A pluripotent stem cell can give rise to cells of the three germ layers- the ectoderm, the endoderm and the mesoderm, these three germ layers are the embryonic sources of all the cells that make up the human body. A pluripotent stem cell is obtained after the totipotent stem cell has undergone cell division. A pluripotent stem cell cannot give rise to extra embryonic tissues like the placenta and umbilical cord. Thus a pluripotent stem cell can give rise to any cell type, a property that is observed in the natural course of embryonic development and under certain laboratory conditions.
Multipotent stem cell:
Multi means many. The multipotent stem cells can give rise to many cells. Haemopoietic stem cells are multipotent in nature; they can give rise to red blood cells, white blood cells, platelets etc. The multipotent stem cells have recently been found to exhibit plasticity, That is they can give rise to non haemopoietic tissues like the brain cells and the heart muscles.
Unipotent stem cell:
Uni is derived from latin word “unus” which means one. These cells are capable of giving rise to cells of a particular lineage. The adult stem cell in many differentiated, undamaged tissues are typically unipotent and give rise to just one cell type and are capable of long term renewal for that tissue. However if the tissue becomes damaged and multiple cell type is required then pluripotent cells must be activated. Example for unipotent stem cell is the skeletal myoblast cell, these cells can only give rise to myoblasts.
Embryonic Stem Cell
Embryonic stem cell: Embryonic stem cells are how we all begin. They are the most primitive of all stem cell population. As their name suggest they are obtained from an embryo. They are derived from the inner cell mass of 4 to 5 days old embryo. The embryo is obtained by invitro fertilization of egg and a sperm and donated for the purpose of research. ESC capture the imagination because they are immortal and have unlimited developmental potential. They can potentially give rise to all the cells that make up the human body. They are the richest source of stem cell. When cultured in the appropriate medium ESCs undergo unlimited number of cell doubling and retain the capacity to differentiate into different cells including the cardiomyocyte. The Human embryonic stem cell promises an unlimited supply of specific cell types for basic research and for transplantation therapies ranging from heart disease to Parkinson disease to various forms of cancer.
In 1981, researchers reported methods for growing mouse embryonic stem cells in the laboratory and it took nearly 20 years before similar achievements could be made with human embryonic stem cells. Though ESCs has many properties for application in cell regeneration, its use is hampered due to a combination of reasons. One of the complex technical issues surrounding the isolation and propagation of embryonic stem cell in vitro is the identification of the proper culture conditions, which can keep the cells in an undifferentiated state or induce differentiation into a particular type of the cell. It is unknown that stem cell cultured in vitro (apart from the embryo)will function as the cells do when they are part of the developing embryo. In addition culturing of embryonic stem cell leads to recruitment of cancer cells, which undergoes proliferation along with the ESC in the culture dish. Many conflicting ethical, moral and political debates exist that limit the use of human ESCs in cell regeneration therapy. Deriving cells from inner cell mass of an embryo is tantamount to destroying a human life. It is unknown if embryonic stem cell lines will continue to proliferate indefinitely or will undergo genetic mutation and fail to be useful. Further the use of embryonic stem cell in transplantation has problems of immune rejection; it requires the use of immunosuppressive drugs to avoid rejection of transplanted cells. Therefore obtaining long term effective results with embryonic stem cell is not feasible. Animal studies have indicated that the transplanted ESCs may result in formation of tumors and teratomas. Recently abnormalities in chromosome numbers and structures were found in three human ESCs line. These disadvantages of ESCs led scientist to seek for an alternate source of stem cells.
Dilated cardiomyopathy (DCM) is a most common form of cardiomyopathy. It is also known as congestive cardiomyopathy. In dilated cardiomyopathy (DCM) the muscle mass is increased, ventricular wall thickness is reduced. The heart assumes globular shape, and there is pronounced ventricular chamber dilation and decreased endocardial thickening, and atrial enlargement. Dilated cardiomyopathy damages the muscle tissue that makes up the hearts pumping chambers. If the chamber wall become week enough, the heart can no longer perform its normal pumping function. The decreased heart function will affect the lungs, liver and other body systems. In the beginning the parts of the body will try to put up for the hearts pumping power by increasing the amount of fluid they hold and by making more blood than usual. The heart chambers dilate to make room for greater blood volume. This expansion can initially restore some of the hearts pumping strength because the more a muscle is stretched, the more forcefully it can contract. The long term effects of an enlarged heart is not good, the heart increases its rate to pump more blood to the body and when the heart is not able to contract, then circulation gets affected, fluid build up occurs in the lungs and the abdomen. This fluid build up make breathing difficult and causes swelling. An enlarged heart sometimes leads to abnormal heart rhythms called arrhythmia..
The primary objective of this project work is as follows:
To stimulate and isolate Peripheral Blood derived Stromal Cells (PBSCs).
To study the mode of instillation of these Peripheral Blood derived Stromal cells in treating patients with heart failure.
To study whether the installed cell serves as potential source for cell therapy for curing Cardiomyopathy.
The age group of the patients in the study group was 48 ± 6 years. Their Ejection Fraction (EF%) was in the range of 32 ± 7%. The Ejection Fraction of a normal person is 70-80%. Hence it was decided to treat these patients with Autologous peripheral blood derived Stem cell therapy. This project work is a preliminary pilot study conducted to asses the long term prospects of the patients with Cardiomyopathy who are treated with peripheral blood derived stromal cells. A complete blood count and differential count was taken for all the patients in the study group. All the six patients were then treated with Neupogen - a human Granulocyte colony stimulating factor. The dosage was 30μg once a day for 3 days. Once again a complete blood count was taken. There was a five fold increase in the Total count (TC) of the patients after treatment with Granulocyte colony stimulating factor. The Total WBC count is increased in order to obtain an optimum yield of stem cells.