Membrane Microparticles from Patients with Steroid-Induced Avascular Necrosis of Femoral Head Increase the Expression of Fas in Endothelial Cells In Vitro.

High-dose or long-term usage of steroid have been suggested to be at great risk of developing avascular necrosis of femoral head (ANFH). A theory proposed to decipher the mechanism behind the development of steroid-induced ANFH involves vascular compromise and cell death. Membrane microparticles (MMPs) are fragments shed from plasma membrane blebs of virtually all cell types when submitted to a number of stress conditions, including apoptosis. It has been reported that high-dose dexamethasone cause dysfunction and apoptosis of endothelial cells; and MMPs isolated from the plasma of patients with myocardial infarction of preclampsia were found to cause damage in isolated arteries in vitro. We hypothesize that MMPs generated after high-dose or long-term administration of steroid facilitates the apoptosis of endothelial cells initiated by steroid, which contributes to the development of ANFH. MMPs were isolated from the blood of 4 healthy individuals, and 5 patients demonstrated to have ANFH by magnetic resonance imaging (MRI) and X-ray. The mean duration and accumulated dose of steroid administration were 8 months and 2000 mg respectively. The 3rd generation of human umbilical vein endothelial cells (HUVEC) was exposed to MMPs (corresponding to 0.2-fold circulating plasma level) prepared above. After 48 hours, part of cells was lysed to make total cell lysate. And the rest were used to prepare mRNA. The expression level of Fas was detected with reverse-transcript PCR and Western Blot. Our results shown that treatment of HUVEC with MMPs from ANFH patient’s blood significantly increases the transcription and expression of Fas, indicating that MMPs derived from patients with steroid-induced ANFH exacerbates high-dose steroid-induced apoptosis of endothelial cells by enhancing the expression of Fas.