CXCR4, also known as C-X-C motif chemokine receptor 4, is a G-protein coupled receptor that plays a crucial role in various biological processes. It is widely expressed in numerous tissues, including peripheral blood leukocytes, spleen, thymus, bone marrow, heart, placenta, lung, liver, skeletal muscle, kidney, pancreas, cerebellum, cerebral cortex and medulla (microglia and astrocytes), brain microvasculature, coronary arteries, and umbilical cord endothelial cells.