Telopeptide-depleted bovine skin collagen as a carrier for bone morphogenetic protein

The telopeptide of type I collagen is thought to be responsible for causing immunogenic response when introduced into xenogenic hosts. To eliminate this problem, solubilized bovine skin collagen was filtered through a millipore membrane, digested repeatedly with pepsin to remove telopeptides, and used as a carrier for a water-soluble, partially-purified fraction of bone morphogenetic protein (BMP) in mice. Composite implants of this telopeptide-depleted collagen and the partially-purified BMP fraction consistently elicited ectopic bone formation in mice 3 weeks postimplantation. When implanted alone, collagen or BMP failed to show this response. Collagens, prepared by use of conventional methods (acid-solubilized collagen, or collagen-digested once with pepsin) were also assessed as carriers for BMP, but were found to be inferior in terms of consistency of bone formation and amount of induced bone mass. The results suggest that telopeptide-depleted collagen permitted a gradual release of purified BMP for induction of bone, with minimal immunogenic interference. Consequently, this collagen carrier represents an important development for future clinical application of BMP.