AGE-RELATED AND GENDER-RELATED CHANGES IN THE DISTRIBUTION OF OSTEOCALCIN IN THE EXTRACELLULAR-MATRIX OF NORMAL-MALE AND FEMALE BONE - POSSIBLE INVOLVEMENT OF OSTEOCALCIN IN BONE REMODELING

With increasing age, bone undergoes changes in remodeling that ultimat ely compromise the structural integrity of the skeleton. The presence of osteocalcin in bone matrix may alter bone remodeling by promoting o steoclast activity. Whether age and/or gender-related differences exis t in the distribution of osteocalcin within individual bone remodeling units is not known. In this study, we determined the immunohistochemi cal distribution of osteocalcin in the extracellular matrix of iliac c rest bone biopsies obtained from normal male and female volunteers, 20 -80 yr old. Four different distribution patterns of osteocalcin within individual osteons were arbitrarily defined as types I, II, III, or I V. The frequency of appearance of each osteon type was determined as a percent of the total osteons per histologic section. The proportion o f osteons that stained homogeneously throughout the concentric lamella e (type I) decreased in females and males with increasing age. The pro portion of osteons that lack osteocalcin in the matrix immediately adj acent to Haversian canals (type III) increased in females and males wi th age. Osteons staining intensely in the matrix adjacent to Haversian canals(type II) increased in females and was unchanged in aging males . Osteons that contained osteocalcin-positive resting lines (type IV) increased in bone obtained from males with increasing age but were unc hanged in females. Sections of bone immunostained for osteopontin (SPP -I), osteonectin, and decorin did not reveal multiple patterns or alte rations in staining with gender or increasing age. We suggest that the morphology of individual bone remodeling units is heterogeneous and t he particular morphologic pattern of osteocalcin distribution changes with age and gender. These results suggest that differences in the dis tribution of osteocalcin in bone matrix may be responsible, in part, f or the altered remodeling of bone associated with gender and aging.