BMP binding peptide: A BMP‐2 enhancing factor deduced from the sequence of native bovine bone morphogenetic protein/non‐collagenous protein

Abstract

Forty years ago, Marshall Urist described a partially purified extract of demineralized bone matrix which induced the formation of ectopic bone. This substance, bone morphogenetic proteinhon-collagenous protein (BMPINCP), was never purified to honiogeneity but other investigators used similar starting materials to clone a number of recombinant BMPs. Urist recognized that his material probably contained the BMPs which had been cloned by others but always contended that it contained another, more potent, bone inducing material which differed significantly in its physical and chemical properties from the known BMPs. We have used Urist's protocol to isolate a protein that has the chemical and physical properties of Urist's "BMP". It is an 18.5 k D fragment of the bone matrix protein, SPP-24. This fragment contains the cystatin-like domain of SPP-24. We have located a 19 amino acid region which is similar to the TGF-P/BMP-binding region of fetuin, a member of the cystatin family of protease inhibitors. A cyclic peptide, which we call BMP binding peptide (BBP) was generated using this sequence. The peptide avidly bound rhBMP-2 with a K D of 3 x M. When implanted alone in mouse muscle, the peptide frequently induced dystrophic calcification. When implanted with rhBMP-2, the peptide enhanced the osteogenic activity of the recombinant molecule. We hypothesize that Urist's "BMP" was a fragment of SPP-24 which influenced bone induction by binding to bone morphogenetic proteins. BBP may be clinically useful because of its effects on other bone-inducing substances.

Enhancement of recombinant human BMP‐7 bone formation with bmp binding peptide in a rodent femoral defect model

“…The estimated dissociation constant (K D ) between BBP and rhBMP-2 was 3 Â 10 À5 M, which was similar to that between BBP and TGF-B receptor II. 10 Our results suggest that BBP can bind to rhBMP-7 and enhance its osteogenic activity. Furthermore, this enhancement appears to be dose-dependent.…”

“…This peptide contains a cystatin-like domain that is a fragment of secreted phosphoprotein-24 (SPP-24), which belongs to cystatin family. 10 The N-terminal 107 residues of SPP-24 are related to the cystatine family of thiol protease inhibitors, which are known to be involved in bone turnover. 19 Other members of the cystatin family, such as fetuin, have an affinity to TGF-B and BMPs because the cystatin domain contains a region similar to the TGF-B receptor II homology 1 domain (TRH1).…”

“…Similar results were reported by previous studies. 9,10 However, when 1000 mg of BBP was combined with either 2 mg rhBMP-7 or 5 mg rhBMP-7, significant differences were seen in radiographic scores, manual palpation, and bone volume compared to 2 mg rhBMP-7 or 5 mg rhBMP-7 alone, suggesting that BBP itself does not have osteoinductive potential but can enhance the osteogenic activity of rhBMP-7. The estimated dissociation constant (K D ) between BBP and rhBMP-2 was 3 Â 10 À5 M, which was similar to that between BBP and TGF-B receptor II.…”

“…BBP enhanced rhBMP-2 induced ectopic bone formation in a mouse muscle pouch implantation model. 10 Furthermore, this peptide also accelerated rhBMP-2 induced radiographic fusion in a rat spine model. 9 We hypothesized that BBP can be used to enhance bone healing of rhBMP-7 and that the effect is dose related.…”

“…These strategies include the use of delivery devices that allow better application of rhBMP-7 and obtain better retention at the surgery site, 7 the use of carriers that control the release of rhBMP-7, 8 and the use of a specific binding peptide that enhances the effect of rhBMP-2 in bone healing. 9 BMP binding peptide (BBP) was developed by Behnam et al 10 They isolated an 18.5 kDa fragment of the human bone matrix protein that has the chemical and physical properties of Urist's ''BMP.'' BBP enhanced rhBMP-2 induced ectopic bone formation in a mouse muscle pouch implantation model.…”