[The growth plate in chronic renal insufficiency]

Several alterations have been reported in the growth plate of young rats rendered uremic by subtotal nephrectomy, a widely used experimental model of growth failure secondary to renal insufficiency. In our lab's experience, uremia is associated with a markedly increased growth plate height which results from an elongation of the hypertrophic zone. These findings are not consistently observed in all studies, likely because of the different experimental conditions. Regardless of growth plate size, growth retardation induced by chronic renal failure is accompanied by an alteration of the dynamics of the growth plate with a decreased bone apposition rate at the metaphyseal end of growth cartilage and slower production and progression of chondrocytes from the resting zone up to the most distal hypertrophic zone adjacent to bone. These abnormal dynamics are associated with an irregular bone-cartilage interface and a disturbed process of chondrocyte maturation which becomes evident by a morphological criteria and by depressed expression of markers of chondrocyte maturation such as collagen X. The microscopic findings also suggest a disturbed process of capillary invasion, which precedes formation of new osseous tissue in the primary spongiosa, although the levels of vascular endothelial growth factor, as measured by immunohistochemistry, have been reported to be similar in the growth plate of uremic and control rats. The meaning of these findings in the pathogenesis of growth impairment secondary to chronic renal failure remains to be determined.