ADULT STEM CELL

History on Adult Stem Cell

History on Adult Stem Cell

Introduction

Adult Stem Cells are cells found in all multicellular organisms. They can continuously produce unaltered daughter cells and have the ability to produce daughter cells that have more restricted properties. Stem cells thus exhibit the two unique features of being able to self-renew and being able to differentiate into multiple cell types in the body—a quality also known as potency. This range of ability is in contrast to most other cells in the body, which are terminally differentiated, in that they can only divide to form the same specific cell type. The properties of self-renewal and totipotency allow stem cells to generate tissues in the body during development and to regenerate these same tissues after injury or degeneration. The unique properties of stem cells offer much promise in terms of understanding embryonic development, cancer biology, and biomedical applications. However, the extrinsic and intrinsic signals that govern the fate of stem cells remain poorly understood and are active areas of investigation (Thomas, 2006).

Stem cells are often characterized as either adult stem cells or embryonic stem cells. Embryonic stem cells are defined as the inner cell mass of the blastocyst, or 3-5-day-old embryo, and form all the cell types of the developing embryo. Adult stem cells allow the body to replace dead or dying cells, as in the case of skin, or to recover from injuries and other forms of tissue damage. Adult stem cells have been identified in the skin and continue to be identified in many different parts of the body, including the breast and pancreas. Plasticity or potency refers to the ability of a stem cell to differentiate into other cell types. Totipotency refers to the ability of the cells to differentiate into any cell of the body, either embryonic or extraembryonic, such as the cells that make up the placenta (Margaret, 2007).

Discussion and Analysis

Pluripotent adult stem cells form the three main germ layers of the developing embryo, the endoderm, mesoderm, and ectoderm. The endodermal cells comprise the cells of the blood vessels and most internal organs; the mesodermal cells comprise the cells of the musculature and skeleton; and the ectodermal cells develop into the cells lining the outer and inner cavities of the body, such as skin cells and cells lining the digestive tract. Multipotent stem cells are cells that can develop into closely related cell types. For example, hematopoietic stem cells are the stem cells that can differentiate into all the cell types present in blood, such as white blood cells, red blood cells, and platelets. Unipotent stem cells maintain the unique stem cell property of self renewal but can only reproduce on cell type. For example, a terminally differentiated unipotent skin stem cell, or keratinocyte, can only ever be a skin cell and can only rarely divide to form more cells. However, as we constantly slough off dead skin cells, their number must be replenished to maintain the integrity of our skin ...