Bone marrow endothelial cells secrete thymosin β4 and AcSDKP

The tetrapeptide AcSDKP, an inhibitor of primitive hematopoietic cell proliferation, induces angiogenesis in vitro and in vivo

“…The intracellular concentration of AcSDKP increases at the beginning of culture and decreases progressively as the cells approach confluence. These data are consistent with the recently reported presence of AcSDKP in extracts of bone marrow endothelial cells 39,40 and suggest that AcSDKP produced constitutively by the endothelium may act in an autocrine manner to induce angiogenesis. Here we report that AcSDKP indeed acts in vitro as a positive regulator of endothelial cell motility and differentiation, 2 essential components for new vessel formation.…”

In vitro assessment of bone marrow endothelial colonies (CFU-En) in non-Hodgkin's lymphoma patients undergoing peripheral blood stem cell transplantation

“…29,30 Furthermore, it must be said that some of these patients received radiotherapy, which can induce an upregulation of the E-9 protein (CD105) in human vascular endothelial cells. 31 Human bone marrow endothelial cells present in remission phase may also have the effect of protecting and maintaining the hematopoietic stem cell compartment from extensive differentiation through the production of differentiation inhibitors such as thymosin b4 and AcSDKP 32,33 that has been shown to induce angiogenesis in vitro and in vivo. 34 On the other hand, other reports have shown that the existence of circulating BM endothelial progenitor cells can restore blood flow to ischemic animals leading to the concept of 'therapeutic adult vasculogenesis' that may explain the recruitment of ECs to various target organs such as BM, where they might contribute to the in situ neo-vascularization.…”

The peptide network regulated by angiotensin converting enzyme (ACE) in hematopoiesis

“…51 Murine BM endothelial cells, a component of BM stroma, secrete thymosin β4 and Ac-SDKP into the culture media. 52 Ac-SDKP has inhibitory activity on the proliferation of primitive hematopoietic progenitors. For example, Ac-SDKP prevented murine HSC [defined then as spleen colony forming units (CFU-S)] from entering cell cycle.…”