Increased osteocyte apoptosis during the development of femoral head osteonecrosis in spontaneously hypertensive rats

We investigated the presence of osteocyte apoptosis in the necrotic trabecu lae of the femoral head of spontaneously hypertensive rat (SHR) using the i n situ nick end labeling (TUNEL) method and transmission electron microscop y. The occurrence of osteonecrosis and ossification disturbance was signifi cantly higher in SHR compared with Wistar Kyoto (WKY) rats, and Wistar (WT) rats used as control animals (P < 0.01). A high population of TUNEL positi ve osteocytes was detected mainly in 10- and 15-week-old SHRs. Sectioned ex amination of the femoral head of SHRs and WKY rats by electron microscopy r evealed apoptotic cell appearances such as aggregation of chromatin particl es and lipid formation. In contrast, a positive reaction was significantly lower in osteocytes in the femoral heads of WT rats (P < 0.01). Our results indicate that apoptosis forms an important component of the global patholo gic process affecting the femoral head of SHR, which leads to osteonecrosis in this region.