A procollagen C-proteinase inhibitor diminishes collagen and lysyl oxidase processing but not collagen cross-linking in osteoblastic cultures

The deposition of insoluble functional collagen occurs following extracellular proteolytic processing of procollagens by procollagen N‐ and C‐proteinases, fibril formation, and lysyl oxidase dependent cross‐linking. Procollagen C‐proteinases in addition process and activate lysyl oxidase. The present study evaluates a possible role for procollagen C‐proteinases in controlling different aspects of collagen deposition in vitro. Studies determine whether inhibition of procollagen C‐proteinase activity with a specific BMP‐1 inhibitor results in perturbations in lysyl oxidase activation, and in collagen processing, deposition, and cross‐linking in phenotypically normal cultured murine MC3T3‐E1 cells. Data show that BMP‐1 Inhibitor dose dependently inhibits lysyl oxidase activation by up to 50% in undifferentiated proliferating cells. In differentiating cultures, BMP‐1 inhibitor decreased collagen processing but did not inhibit the accumulation of mature collagen cross‐links. Finally, electron microscopy studies show that collagen fibril diameter increased. Thus, inhibition of procollagen C‐proteinases results in perturbed collagen deposition primarily via decreased collagen processing. © 2004 Wiley‐Liss, Inc.