Stem Cell

Stem Cell partially differentiated or undifferentiated cells in multicellular organisms that can differentiate into various types of cells. During the blastocyst stage of embryonic development in mammals, around days 5–14, roughly 50–150 cells make up the inner cell mass, eventually differentiating into all body cell types. However, cultured and isolated in vitro, they can be kept in the stem-cell stage as embryonic stem cells (ESCs).

In mammals, adult stem cells found in a few selected locations in the body can replenish rapidly lost cell types such as hematopoietic stem cells (HSC) to replenish blood and immune cells and mesenchymal stem cells to maintain bone, cartilage, muscle, and fat cells.

With respect to differentiation potential, stem cells could be-

• Totipotent stem cells, which differentiate into embryonic (ectoderm, endoderm & mesoderm) and extra-embryonic cell types, i.e., placenta, constructing a complete, viable organism.

• The descendants of totipotent cells, the pluripotent stem cells, can differentiate into almost all cells, ie, cells resulting from any of the three germ layers but not the organism.

• Multipotent stem cells, which differentiate into several closely related families of the cell.

• Oligopotent stem cells, which differentiate into only some cell types, such as myeloid or lymphoid stem cells.

Multipotentmesenchymal stem cells (MSCs) found in the bone marrow are used in regenerative medicine to assist in repairing bone and cartilage, such as injuries to the knee meniscus or long-term accumulated damage leading to osteoarthritis. Reports of MSCs supporting new blood vessel formation in damaged tissue have major implications for fixing tissue damaged by heart attacks in strengthening the left ventricle. Reducing inflammation by stem cells plays a role in preventing transplant rejection and slows the progression of autoimmune diseases. Stem cell therapies might assist people in treating type 1 diabetes, heart disease, stroke,burns, osteoarthritis,Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, cancer, spinal cord injuries, etc. Stem cell therapy has been used in bone marrow transplants for many years because of its effectiveness in clinical trials. [Mamun Rashid Chowdhury]