Biologically active FVIII is present in cell lysates or culture supernatants of purified LECs and LSECs, but not in those of conventional capECs. FVIII activity was measured by using a Biophen FVIII:C Kit and was normalized to equal cell numbers. (A) Biological activity of FVIII in cell lysates of purified LECs and LSECs. Mean ± standard deviation of 3 biological replicates except lung LECs and lung capECs that were the average of 2 experiments. (B) FVIII activity in supernatants (24 hours of cell culture) was detected from primary cultured LSECs and human dermal LECs (HDLECs), but not from primary brain microvascular ECs (BMECs) and human umbilical vein ECs (HUVECs). The activity was normalized for cell number. The data are from 3 biological replicates.