الفهرس 
Male InfertilityOnly 14 pages are availabe for public view
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Abstract
Stem cells are body’s undifferentiated cells which having the capacity of self renewal and differentiating into various cell types depending on the stimuli that they are received. Stem cells are classified into embryonic stem cells (ESCs) and adult stem cells (ASCs).
ESCs originate from inner cell mass of blastocyst. They are clonogenic, capable of undergoing an unlimited number of symmetrical divisions without differentiating, can give rise to differentiated cell types that are derived from all three primary germ layers of the embryo (endoderm, mesoderm and ectoderm) and capable of colonizing the germ line and giving rise to egg or sperm cells.
ASC is an undifferentiated (unspecialized) cell that occurs in a differentiated (specialized) tissue, renews itself, and becomes specialized to yield all of the specialized cell types of the tissue from which it originated. Their primarily functions are to maintain the steady state functioning of a cell-called homeostasis and, with limitations, to replace cells that die because of injury of diseases.
The use of adult stem cells is somewhat limited, this is due to that adult stem cells cannot be induced to develop into any cell type, difficulty to identify, isolate, purify, and grow, they may not exist for some tissues, including insulin-producing cells. Also, cell- replacement therapies such as islet transplantation require an unlimited source of donor cells to have widespread success.
Stem cells are, indeed, capable of becoming almost all of the specialized cells of the body and thus may have the potential to generate replacement cells for a broad array of tissues and organs, such as heart, pancreas and the nervous system. Thus, this class of human stem cell holds the promise of being able to repair or replace cells or tissues that are damaged or destroyed by many of our most devastating diseases and disabilities. We can use stem cells by transplantation of differentiated cells derived from stem cells or by direct administration of stem cells and they would colonise the correct site of the body and continuously differentiate into the desired cell type or by stimulation of endogenous stem cells.
Stem cells are a source for the generation of normal human cell types that can be genetically or pharmacologically manipulated and used for drug discovery. They could be used as vehicles i.e. bearers of genetic information for the therapeutic delivery of genes. A problem for research on gene therapy has been to find safe delivery systems and stem cells may provide a solution here. Human ES cells should offer insights into developmental events that cannot be studied directly in the intact human embryo but that have important consequences in clinical areas, including birth defects, infertility, and pregnancy loss.
The study of stem cells has been very useful in the area of reproduction. An interesting study of transferring stem cell spermatogonia from fertile mice into the testis of infertile mice has shown that the process of spermatogenesis could be activated in the infertile mice’s testis by the donor stem cells. This could be a huge step forward in solving the problem of infertility in humans and animals.
Stem cells may be useful in the treatment of different types of male infertility like primary spermatogenic failure for example, germ cell aplasia and severe cases of spermatogenic maturation arrest. The ability of culture the spermatogonial stem cells indefinitely makes it possible to create sperm in vitro without implanting them in a recipient male. This technology could be useful for correcting some types of infertility in which there is a defect in the testicular environment. Numerous studies on the molecular genetics of some of endocrine diseases and metabolic disorders which associated with infertility have identified germline gene mutations, to prevent those lethal or life threatening diseases caused by inborn errors, germline gene therapy using SSCs will become a promising and feasible approach.
Another problem which facing patients whose have cancer and taking oncological therapy which possibly leaves patient with no germ cells are observed and the seminiferous epithelium consist of sertoli cells only, these patient show a reduction of testicular volume with sever oligo or azoospermia.
These problems can be solved by removing germ cells from the gonads before chemo- or radiotherapy and re-introduce them into male gonads after finishing the treatment and recovery of the patient, this protect and conserve the germ cell line of the patient . Also, pre-pubertal boys with no options of fertility preservation by cryoperservaion of semen sample this approach has a potential to preserve their fertility.
Natural killer cells taken from human embryonic stem cells are very effective at killing tumors especially prostate cancer and testicular carcinoma and preventing the cancer from metastasizing in any of the animal’s organs.
An immunocytological method targeting nuclear stem cell/GCT markers has proven useful for detection of carcinoma in situ (CIS) cells in semen in some patients and may become applicable for screening or as an auxiliary test in andrology centers that allow a careful follow-up.