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Abstract Stem cell biology has attracted tremendous interest recently. It is hoped that it will play a major role in the treatment of a number of incurable diseases via transplantation therapy. Several varieties of stem cells have been isolated and identified in vivo and in vitro. Very broadly they comprise of two major classes: embryonic/fetal stem cells and adult stem cells. Stem cells are important for living organisms. In the 3- to 5-day-old embryo, the so called blastocyst, stem cells give rise to the multiple specialized cell types that make up the heart, bone, lung, skin, and other tissues. In some adult tissues, such as bone marrow, liver, muscle, and brain, small populations of adult (or somatic) stem cells control replacement of cells which are lost through age, injury, or disease. There are three important characteristics that distinguish stem cells from other cell types. Stem cells are unspecialized but pluripotent (can differentiate into all three major tissue types) cells, which have the ability to indefinitely renew themselves. Scientists put great effort in the understanding, identification, and characterization of the various differentiation processes stem cells may undergo. This leads to an increasing knowledge about how an organism develops from a single cell and how damaged cells are replaced in adult organisms. This opens doors for scientists to investigate the possibility of cell-based therapies to treat disease, which is often referred to as “regenerative” or “reparative” medicine. Summary 87 Cell therapy, including the disciplines of regenerative medicine, tissue, and bio-engineering, is dependent on cell and tissue culture methodologies to generate and expand specific cells in order to replace important differentiated functions lost or altered in various disease states. Therapies aiming to promote renal regeneration need first to discriminate between the disease states of acute kidney injury (AKI) and chronic kidney disease (CKD). AKI is a common disease with disparate etiologies that involve reduced total or partial renal blood flow with resultant ischemic injury. An ischemic/reperfusion model has therefore been commonly used as an experimental model of AKI. (CKD) characterized by a progressive course with ongoing loss of kidney function. Once (GFR) falls below about half of normal, kidney function tends to decline even if the initial insult to the kidney has been eliminated. End-stage kidney disease (ESKD), defined as the need for dialysis, receipt of a transplant, or death from chronic kidney failure, generally affects less than 1% of the population. However ESKD is the end result (CKD), a widely prevalent but often silent condition with elevated risks of cardiovascular morbidity and mortality and a range of metabolic complications. A recently devised classification of CKD has facilitated prevalence estimates that reveal an “iceberg” of CKD in the community, of which dialysis and transplant patients are the tip. In the kidney, tubules and glomeruli show a totally different plasticity. It is widely known from the clinical practice that, in most cases, tubules are able to regenerate even after major damage, although Summary 88 postnatal glomerulogenesis has not been described in human. Probably for this reason, major acute or chronic glomerular damage invariably leads to ESRD. The recent identification of renal progenitor cells both inside the kidney and in the bone marrow may pave the way toward the future regeneration of the damaged kidney. Recent progress in stem cell biology has demonstrated that renal stem cells, with the capability to differentiate into mature renal cells, do exist in adult individual; however, the debate is ongoing regarding their major location. Suggestions include the interstitium of the cortex,and papilla, tubules and bone marrow. We need to be innovative in our therapy for AKI, CKD and provide a substitute for dialysis as soon as possible. Regenerative medicine is the great hope for realizing this goal. Here, we have listed the minimum requirements for artificial kidney formation de novo and reviewed step by step the challenges in satisfying them. |