An EP2 receptor-selective prostaglandin E2 agonist induces bone healing - PubMed (original) (raw)

. 2003 May 27;100(11):6736-40.

doi: 10.1073/pnas.1037343100. Epub 2003 May 14.

F Borovecki, H Z Ke, K O Cameron, B Lefker, W A Grasser, T A Owen, M Li, P DaSilva-Jardine, M Zhou, R L Dunn, F Dumont, R Korsmeyer, P Krasney, T A Brown, D Plowchalk, S Vukicevic, D D Thompson

Affiliations

An EP2 receptor-selective prostaglandin E2 agonist induces bone healing

V M Paralkar et al. Proc Natl Acad Sci U S A. 2003.

Abstract

The morbidity and mortality associated with impaired/delayed fracture healing remain high. Our objective was to identify a small nonpeptidyl molecule with the ability to promote fracture healing and prevent malunions. Prostaglandin E2 (PGE2) causes significant increases in bone mass and bone strength when administered systemically or locally to the skeleton. However, due to side effects, PGE2 is an unacceptable therapeutic option for fracture healing. PGE2 mediates its tissue-specific pharmacological activity via four different G protein-coupled receptor subtypes, EP1, -2, -3, and -4. The anabolic action of PGE2 in bone has been linked to an elevated level of cAMP, thereby implicating the EP2 and/or EP4 receptor subtypes in bone formation. We identified an EP2 selective agonist, CP-533,536, which has the ability to heal canine long bone segmental and fracture model defects without the objectionable side effects of PGE2, suggesting that the EP2 receptor subtype is a major contributor to PGE2's local bone anabolic activity. The potent bone anabolic activity of CP-533,536 offers a therapeutic alternative for the treatment of fractures and bone defects in patients.

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Figures

Fig. 1.

Fig. 1.

(A) Chemical structure of CP-533,536. (B) Analysis of intracellular cAMP levels on treatment of cells with CP-533,536. HEK-293 cells stably transfected with the EP2 receptor were treated with increasing concentrations of CP-533,536, and intracellular cAMP levels were measured.

Fig. 2.

Fig. 2.

Peripheral quantitative computerized tomography images of proximal tibial cross sections from rats injected with vehicle or CP-533,536 directly into the bone marrow. White area, within the bone circumference, represents areas of high bone mass, whereas other colors represent areas of lower-density tissues including bone marrow (red).

Fig. 3.

Fig. 3.

X-rays of canine ulnar critical defect treated with 1.0 ml of PLGH matrix show no healing/rebridging sequence at 2 (A), 12 (B), and 24 (C) weeks after surgery. Critical defects treated with 10 mg of CP-533,536 dissolved in 1.0 ml of matrix showed a time-dependent healing/rebridging sequence at 2 (D), 12 (E), and 24 (F) weeks after surgery.

Fig. 4.

Fig. 4.

A toluidine blue-stained section of the midulnar region from the canine critical defect model after treatment with 1.0 ml of PLGH matrix alone shows no rebridgement at 24 weeks after surgery (A), whereas full rebridgement was observed after treatment with 10 mg of CP-533,536 (B). Intense remodeling of the newly formed cortical bone was observed and consisted of osteons (C, arrow-head), active vascular channels with hematopoietic marrow, rows of osteoblasts, and newly deposited osteoid (O) on the surface of mineralized lamellar bone (D, arrow). Final magnification: A and B = ×25; C and D = ×125.

Fig. 5.

Fig. 5.

X-rays of a canine tibial osteotomy treated with 0.5 ml of PLGH matrix alone show no healing/rebridging sequence at 2 (A), 4 (B), and 8 (C) weeks after surgery. Defects treated with 5 mg of CP-533,536 dissolved in 0.5 ml of matrix showed healing/rebridging sequence at 2 (D), 4 (E), and 8 (F) weeks after surgery.

Fig. 6.

Fig. 6.

Plasma concentrations of CP-533,536 in dogs after administration in a PLGH matrix formulation to the site of a tibial osteotomy (•, 25 mg) or ulnar critical defect [▴, 10mg;♦,50mg;▪, 10 mg (0.2 ml of 50 mg/ml)]. Each point represents drug blood values from 4–10 dogs.

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