NONCOLLAGENOUS PROTEINS IN HETEROTOPIC OSSIFICATION - IMMUNOHISTOCHEMICAL ANALYSIS IN 15 PARAPLEGIES

We used immunohistochemical techniques to investigate the distribution pattern of osteonectin, osteocalcin, bone sialoprotein II and the sma ll proteoglycans decorin and PG 100 during different stages of heterot opic ossification (HO) in pressure sores of paraplegic patients. All t hese noncollagenous proteins (NCPs) accumulated in fibroblasts and pre osteoblasts, predominantly in the activity centers of early osteogenet ic areas. Mature types of HO showed a more discrete expression pattern for this protein group, with weaker reactions in the narrow osteoblas tic rims. Decorin was detected predominantly in the stroma of HO. Our results indicate that the NCPs are important components during the pat hogenesis of HO and that fibroblasts may serve as osteoprogenitor cell s.