Abstract (hsc full form)

 

Abstract (hsc full form)

It is the mammalian blood network comprises more than ten different types of mature cells, is based on a single cell type: hematopoietic stem cells (HSC). Within the system there are only HSC have the capacity of self-renewal and multi-potency. Multi-potency refers to the capacity to differentiate into functional blood cells of all kinds. Self-renewal can create HSC self-renewal without differentiation. Because mature blood cells tend to be shorter-lived, HSC continuously provide more differentiated progenitors, while also ensuring that the HSC pool size in a balanced manner throughout their lives by precisely maintaining a balance between self-renewal and differentiation. Therefore, understanding the mechanism of self-renewal and differentiation HSC is a major problem. In this review, we concentrate on the hierarchy of the hematopoietic organ system, our current understanding of the molecular and microenvironmental cues that regulate self-renewal and differentiation in adult HSC and the developing systems-based approaches to understanding HSC biological function. Go to:

Introduction

Although maturing blood cells can be created at a rate of greater 1 million cell every second in adult humans ([1] 11 the majority of hematopoietic stem cells (hscs) from the source of which they originate are not very often cycled and are located within the G 0 phase of the cell cycle in the conditions of homeostasis [2]. This is an intriguing dilemma: how can the body achieve an equilibrium where a sufficient supply of hscs remains throughout the lifespan of the organism, and simultaneously, HSCs always meet the body's huge need for constant replenishment of maturing blood cells the majority of which have a short lifespan. This balance is illustrated by the many instances where abnormal HSC development can cause severe diseases e.g. when HSC differentiation into committed progenitors are not accompanied by the normal loss of self-renewal capacity or progenitors derived from HSCs do not fully transform to mature blood cells [ 3and could develop into a preleukemic process 44. The intriguing aspects of mammalian hemopoiesis have led to a vast study of the system over the past few decades. In this article we will focus on the problem we have identified, and then discuss what is available about the regulatory processes that regulate the capacity of HSCs to produce millions of blood-forming mature cells, while simultaneously maintaining the HSC pool to be adequate throughout the life span of the animal. Go to:

The Concept of Stem Cells

The "stem cell" concept was first suggested in the late 1970s by Till and McCulloch after their pioneering research of the regeneration of the blood system in live. After transplanting a limiting the number of syngenic bone marrow (BM) cells to mice that were receiving them They observed cells that had formed in the spleens of recipients mice. Analyzing these colonies revealed that a small portion of the donors BM cells had two unique characteristics: (1) the ability to produce multiple kinds of myeloerythroid cells as well as (2) the capacity to self-replicate [ 58]. 88 1. These results revealed the two main characteristics of stem cells i.e. multi-potency and self-renewal. Hematopoietic Stem Cells (HSCs) constitute the only cells in the hematopoietic system with the capacity for multi-potency and self-renewal. For HSC multi-potency, it is the capacity to differentiate into the various functional blood cells and self-renewal is the capacity to produce identical daughters HSCs with no differentiation.

The field of research into stem cells has grown significantly from the early studies of Till as well as McCulloch and includes stem cells that can give rise to specific tissues or organs (collectively called tissue-specific stem cells) as well as embryonic stem (ES) cells that can produce every kind of cell in the adult body. The system of nomenclature has been developed to describe the potential for differentiation of various types of stem cells (summarized as Table 1). It is not within our scope to address the non-hematopoietic stem cells; great reviews of these cells can be found within this article.

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