Stem Cell
An undifferentiated cell capable of self-renewal and differentiation into specialised cell types. Stem cells play roles in tissue repair and regeneration. Motixafortide (a CXCR4 antagonist) is approved for mobilising stem cells from bone marrow into the bloodstream for collection and transplantation.
Technical Context
Stem cell types: embryonic stem cells (pluripotent — can differentiate into any cell type, ethically complex), adult/tissue stem cells (multipotent — restricted to cell types within their tissue: haematopoietic stem cells → blood cells, mesenchymal stem cells → bone/cartilage/fat/muscle, neural stem cells → neurons/glia), and induced pluripotent stem cells (iPSCs — adult cells reprogrammed to pluripotency). Motixafortide's mechanism: CXCR4 antagonism. The CXCL12/CXCR4 axis is the primary retention mechanism for haematopoietic stem cells (HSCs) in bone marrow niches — CXCL12 (stromal cell-derived factor 1, SDF-1) expressed by bone marrow stromal cells binds CXCR4 on HSCs, anchoring them in the marrow. Motixafortide blocks this interaction, releasing HSCs into the peripheral blood for collection by apheresis. It is used with G-CSF for stem cell mobilisation prior to autologous transplantation in multiple myeloma patients.