Dietary restriction reduces the prevalence of osteonecrosis of the caput femoris in spontaneously hypertensive rats

We investigated the effects of dietary restriction (DR), an experimental in tervention known to suppress several strain-specific diseases, on the preva lence of osteonecrosis of the caput femoris in spontaneously hypertensive r ats (SHR). At 6 weeks of age, the food intake of DR rats was restricted to 65% of the mean intake of control rats fed ad libitum (AL), Acute osteonecr osis of the caput femoris without reparative tissue response (RTR) was obse rved at 10 and 15 weeks in both DR and AL groups; no such acute lesion was seen at 20 and 30 weeks. The prevalence of osteonecrosis, osteonecrosis wit h/without reparative tissue response was significantly reduced in DR rats a t 15 and 20 weeks, but not at 10 weeks. DR reduced the body weight by 30% a nd the length of the femur by 10%. Ossification of the caput femoris, known to be delayed in AL rats compared with Wister Kyoto rats, was also restore d by DR. Our results showed that dietary restriction reduced the prevalence of osteonecrosis and modulated the mechanical factors involved in the lesi on. They also indicate that utilization of dietary restriction is a useful research tool for investigating the underlying mechanisms of osteonecrosis of the caput femoris in SHR.