TFPI is expressed in BM endothelial cells. (A) Murine BM cells were isolated by first flushing the long bones from the hind limbs, crushing the bones treated with collagenase I. Lin⁺CD45⁺ cells were depleted by magnetic-activated cell sorter columns and cells subsequently stained with antibodies against lineage, CD45, CD31, CD51, and Sca-1 antigens. ECs (lin⁻CD45⁻CD31⁺), OBs (lin⁻CD45⁻CD31⁻CD51⁺Sca-1⁻), MSCs (lin⁻CD45⁻CD31⁻CD51⁺Sca-1⁺), and HCs (lin⁺) were FACS sorted and qRT-PCR was performed for Tfpi, Cxcl12, and Nestin. HC, hematopoietic cell. (B) Resulting cDNAs were also identified by DNA gel electrophoresis. (C) Expression of TFPI protein in the BM was assessed by immunostaining decalcified long bones with antibodies against CD31 and TFPI. (D) Effect of lethal radiation on Tfpi expression was examined by comparing its expression in lin⁻CD45⁻ cells from control and irradiated long bones.