STEM CELLS

INTRODUCTION: Stem cells are characterized by their ability of possessing self-renewal capability and capacity to generate differentiated cell lineages. These cells in short terms are broad in perspective that later in their life span, can give rise to different cell types.

PROPERTIES OF STEM CELLS: There are different cellular properties that would otherwise be absent in other cell types and let us briefly look at them.

1. Self-renewal capacity and capacity to generate differentiated cell lineages. Here, a stem cell will be able to regain it’s ability to carry out cellular activities following damage or destruction, and then be able to divide and even produce other cell types.

2. Asymmetric replication: This is characterized by division of stem cell into two cells: One daughter cell which gives rise to mature cells, and then the other cell remains as undifferentiated stem cell which retains the self-renewal capacity.

TYPES OF STEM CELLS: Stem cells are of different types and located in different parts of the body.

1. Embryonic stem cells: During development of embryo, the blastocysts contain undifferentiated pluripotent stem cells, which are called as embryonic stem cells or ES cells. These cells can form cells of all three germ cell layers. Their normal function is to give rise to all cells of the human body.

2. Adult or sometimes known as somatic stem cells: Adult stem cells are less undifferentiated than ES cells found in adults. They are found among differentiated cells within a tissue. They have more limited capacity to generate different cell types than ES cells. They usually differentiate into particular tissue. Their normal function is tissue homeostasis.

3. Induced pluripotent stem cells (iPS cells): This is achieved by transferring the nucleus of adult cells to an enucleated oocyte. These are used for therapeutic cloning in the treatment of human diseases.

SITES OF STEM CELLS

1. Bone marrow: This contains two types of stem cells; The Hematopoietic stem cells (HSCs), and these can generate all of the blood cell lineages, and are used for the treatment of hematologic diseases. They can also be collected directly from the bone marrow, from umbilical cord blood, and from the peripheral blood. The other type are the Marrow stromal cells (MSCs): They can generate chondrocytes, osteoblasts, adipocytes, myoblasts, and endothelial cell precursors depending on the tissue to which they migrate.

2. Intestinal epithelium: Stem cells may be located immediately above Paneth cells in the small intestine or at the base of the crypt in the colon.

3. Liver: The liver contains stem cell in the canals of Hering, which are capable of differentiating into hepatocytes and biliary cells.

4. Cornea: Located in the limbus region between the conjunctiva and the cornea.

5. Skin: Located in the bulge area of the hair follicle, in the sebaceous glands, and in the lower layer of the epidermis.

RELATED;

1.  FORMED ELEMENTS FROM STEM CELLS

2.  THE ORIGIN OF CANCER

3.  HEMOGLOBIN AND RED BLOOD CELLS

4.  FETAL CIRCULATION

REFERENCES