CXCL12 and autoimmune thrombocytopenic purpura: Furthermore, Nestin+ MSCs are the most important source of CXCL12 in the bone marrow; the nestin+ MSCs in ITP showed increased apoptosis, decreased populations, and reduced CXCL12 secretion, ultimately leading to impaired megakaryocyte distribution through CXCR4 and VEGFR1-mediated pathways [11].