幹細胞の供給源と効力

Potency is the property of stem cells that determines their ability to self-renew and differentiate into diverse cell types. It defines how many different cell types a stem cell can become, ranging from totipotent cells that form complete organisms to unipotent cells that produce only one cell type. Understanding potency is essential for predicting stem cell therapeutic potential.

Totipotent stem cells, such as zygotes and plant meristem cells, can develop into all cell types and form a complete organism. Pluripotent stem cells, including embryonic stem cells, can form most but not all body cell types and cannot form an entire organism independently. This distinction makes pluripotent cells valuable for regenerative medicine applications.

Multipotent stem cells, such as adult stem cells, can only produce all cells of a specific tissue type. For example, mesenchymal stem cells generate osteoblasts, myocytes, adipocytes, and chondrocytes, but not neurons or blood cells. Hematopoietic stem cells in bone marrow differentiate into all blood cells but not gut or muscle cells.

Induced pluripotent stem cells are genetically engineered somatic cells, such as fibroblasts, that can differentiate into any desired cell type. Unlike embryonic stem cells derived from early development, induced pluripotent stem cells offer a non-embryonic source for regenerative medicine. Both types share pluripotency but differ in their origin and ethical considerations.

Oligopotent and unipotent stem cells result from further restriction of multipotent stem cells. Oligopotent cells like myeloid progenitors give rise to erythrocytes, phagocytes, or granulocytes. Unipotent cells, such as colony-forming unit-erythroid, can only form one cell type, like erythrocytes, and undergo fewer self-renewals than more potent stem cells.

The inner cell mass produces embryonic stem cells that can differentiate into any embryonic tissue, including blood, muscle, neurons, skin, and intestinal cells, but not extraembryonic tissues. Trophectoderm cells form only the placenta, amnion, and chorion. Embryonic stem cells are routinely used in regenerative medicine to treat stroke and neurodegenerative diseases.

Bronchoalveolar stem cells are oligopotent cells of the lungs with restricted tissue lineage. They can differentiate into only the bronchiolar epithelium or alveolar epithelium, unlike multipotent adult stem cells that produce multiple cell types. This restricted potency reflects their specialized role in maintaining lung tissue.