Wozney and colleagues set out to identify the proteins behind the bone‑inducing activity of BMP by cloning human genes for the polypeptides in purified bovine BMP and testing the recombinant proteins in vivo.
Methods
Model
Rat ectopic implant assay
Intervention
Recombinant human BMP‑1
Recombinant human BMP‑2A
Recombinant human BMP‑3
Recombinant proteins expressed in COS and CHO cells (BMP‑1 also in E. coli)
Assays
Amino acid sequencing of purified bovine BMP
Human cDNA cloning
Sequence comparison with the TGF-β family
Cartilage formation in implants
Key Findings
All three recombinant human proteins (BMP‑1, BMP‑2A and BMP‑3) appeared to induce cartilage in vivo, each acting alone.
The authors noted that no other known growth factor had shown this cartilage‑inducing activity in their in vivo assay.
Earlier studies cited by the authors had found that TGF-β1 and TGF-β2 do not induce cartilage or bone in vivo, unlike the BMPs.
Purified BMP was scarce: the preparation represented about 300,000‑fold purification, and 40 kg of bovine bone powder yielded only 40 µg.
BMP‑2A and BMP‑2B were 92% identical in the conserved C‑terminal region, a closer match than between TGF-β1 and TGF-β2.
Board pearl
Unlike BMP‑2A and BMP‑3, BMP‑1 is not a TGF-β family member, and its protease‑like region suggests it may work by binding or activating the other BMPs.
Authors' conclusion
Two of the encoded proteins (BMP-2A and BMP-3) are new members of the TGF-beta supergene family, while the third, BMP-1, appears to be a novel regulatory molecule.
Wozney and colleagues set out to identify the proteins behind the bone‑inducing activity of BMP by cloning human genes for the polypeptides in purified bovine BMP and testing the recombinant proteins in vivo.
Methods
Model
Rat ectopic implant assay
Intervention
Recombinant human BMP‑1
Recombinant human BMP‑2A
Recombinant human BMP‑3
Recombinant proteins expressed in COS and CHO cells (BMP‑1 also in E. coli)
Assays
Amino acid sequencing of purified bovine BMP
Human cDNA cloning
Sequence comparison with the TGF-β family
Cartilage formation in implants
Key Findings
All three recombinant human proteins (BMP‑1, BMP‑2A and BMP‑3) appeared to induce cartilage in vivo, each acting alone.
The authors noted that no other known growth factor had shown this cartilage‑inducing activity in their in vivo assay.
Earlier studies cited by the authors had found that TGF-β1 and TGF-β2 do not induce cartilage or bone in vivo, unlike the BMPs.
Purified BMP was scarce: the preparation represented about 300,000‑fold purification, and 40 kg of bovine bone powder yielded only 40 µg.
BMP‑2A and BMP‑2B were 92% identical in the conserved C‑terminal region, a closer match than between TGF-β1 and TGF-β2.
Board pearl
Unlike BMP‑2A and BMP‑3, BMP‑1 is not a TGF-β family member, and its protease‑like region suggests it may work by binding or activating the other BMPs.
Authors' conclusion
Two of the encoded proteins (BMP-2A and BMP-3) are new members of the TGF-beta supergene family, while the third, BMP-1, appears to be a novel regulatory molecule.