Effects of caloric restriction on development of the proximal growth plate and metaphysis of the caput femoris in spontaneously hypertensive rats: microscopic and computer-assisted image analyses.

We previously demonstrated that caloric restriction (CR) reduced the prevalence of osteonecrosis in caput femoris of spontaneously hypertensive rats (SHR), a model of human Perthes' disease. The effects of CR on the development and pathology in the proximal femoral growth plate (GP) and adjacent structures in SHR were investigated by morphometric and computer-assisted image analyses. From 6 weeks of age, the food intake of SHR was restricted to 65% of the mean intake of ad libitum fed control SHR (SHR-AL). Wistar Kyoto rats (WKY), from which the SHR strain was isolated, fed ad libitum were also included as controls. CR reduced prevalence of chondromucinous degeneration and dysarray of cartilage cell columns in the GP, becoming prevalent between 10 and 20 weeks in the SHR-AL group, attaining the same levels of the WKY group. Thicknesses of non-calcifying cell columns in the GP were greater in the SHR-AL than WKY group; CR slightly reduced the thickness, but incompletely. Thicknesses of calcifying cell columns did not significantly differ among the three groups. CR decreased volume density and mean thicknesses of the trabecular bone in areas adjacent to GPs, and was greater in the SHR-AL than the WKY group. The present morphologic analysis suggested that CR ameliorates dysplastic changes of trabecular bones in areas adjacent to the GP, rather than modulating the ossification process in the GP. The CR paradigm might give insight into the pathogenesis of, and a therapeutic strategy for, human Perthes' disease. Copyright 2002 Wiley-Liss, Inc.