Augmentation of bone morphogenetic protein-induced bone mass by local delivery of a prostaglandin E EP4 receptor agonist.
Recombinant human bone morphogenetic protein (rhBMP) is viewed as a therapeutic cytokine because of its ability to induce bone. However, the high doses of rhBMP required for bone induction in humans remain a major hurdle for the therapeutic application of this protein. The development of a methodology that would effectively overcome the weak responsiveness to human BMP is highly desired. In the present study, we investigate the ability of a prostaglandin E EP4 receptor selective agonist (EP4A) to augment the bone-inducing ability of BMP in a biodegradable delivery system. A block copolymer composed of poly-D,L-lactic acid with random insertion of p-dioxanone and polyethylene glycol (PLA-DX-PEG, polymer) was used as the delivery system. Polymer discs containing rhBMP-2 and EP4A were implanted into the left dorsal muscle pouch of mice to examine the dose-dependent effects of EP4A. Fifty mice were divided into 5 groups based on the contents of rhBMP and EP4 in the polymer (group 1; BMP 5 microg EP4A 0 microg, group 2; BMP 5 microg EP4 3 microg, group 3; BMP 5 microg EP4 30 microg, group 4; BMP 5 microg EP4 300 microg, group 5; BMP 0 microg EP4 30 microg, n=10 each). All implants were harvested, examined radiologically, and processed for histological analysis 3 weeks after surgery. On dual-energy X-ray absorptiometry (DXA) analysis, the bone mineral content (BMC) of the ossicles was 6.52+/-0.80 (mg), 9.36+/-1.89, 14.21+/-1.27, and 18.75+/-2.31 in groups 1, 2, 3, and 4 respectively. In terms of BMC, the values of groups 3 and 4 were significantly higher than those of group 1. The mean BMC value of group 4 was approximately 3 times higher than that of group 1. No significant difference in body weight was noted among the groups during the experimental period. In summary, the presence of a prostaglandin E EP4 receptor selective agonist in the carrier polymer enhanced the bone-inducing capacity of rhBMP-2 with no apparent systemic adverse effects.
Toyoda
Hiromitsu
H
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, 4-3 Asahi-machi, 1-chome, Abeno-ku, Osaka 545-8585, Japan.
Terai
Hidetomi
H
Sasaoka
Ryuichi
R
Oda
Kazunori
K
Takaoka
Kunio
K
D000469:Alkaline Phosphatase / Q000097:blood; D000818:Animals; D001835:Body Weight; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D006801:Humans; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D015675:Osteocalcin / Q000097:blood; D018078:Receptors, Prostaglandin E / Q000819:agonists*; D058309:Receptors, Prostaglandin E, EP4 Subtype; D011994:Recombinant Proteins / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000008:administration & dosage* / Q000494:pharmacology; D013876:Thiophenes / Q000008:administration & dosage* / Q000494:pharmacology
C429966:APS-999 Na; D019485:Bone Morphogenetic Proteins; C545650:PTGER4 protein, human; C545651:Ptger4 protein, mouse; D018078:Receptors, Prostaglandin E; D058309:Receptors, Prostaglandin E, EP4 Subtype; D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds; D013876:Thiophenes; D015675:Osteocalcin; D000469:Alkaline Phosphatase