Article
Treatment of critical-size femoral bone defects with a novel selective EP4 prostaglandin receptor agonist
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Authors
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Stefan Zwingenberger
- UniversitätsCentrum für Orthopädie und Unfallchirurgie an der Technischen Universität Dresden, Dresden, Germany
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Elisabeth Mehnert
- UniversitätsCentrum für Orthopädie und Unfallchirurgie an der Technischen Universität Dresden, Dresden, Germany
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Henriette Bretschneider
- UniversitätsCentrum für Orthopädie und Unfallchirurgie an der Technischen Universität Dresden, Dresden, Germany
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Julia Bolte
- UniversitätsCentrum für Orthopädie und Unfallchirurgie an der Technischen Universität Dresden, an der Technischen Universität Dresden, Dresden, Germany
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Corina Vater
- UniversitätsCentrum für Orthopädie und Unfallchirurgie, Zentrum für Translationale Knochen-, Gelenk- & Weichgewebeforschung, Dresden, Germany
| Published: | October 22, 2019 |
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Outline
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Objectives: Bone regeneration can be stimulated by recombinant growth factors like bone morphogenetic protein-2 (BMP-2). Small molecule agents offer a combination of much lower cost of goods together with good chemical stability, longer anticipated shelf lives, and lack of morphogenic activity. Prostaglandins E1 and E2 both interact with the G-protein coupled receptor EP4 and signal through increased intracellular cAMP levels resulting in bone anabolism. Bone anabolic effects of EP4 have been clearly demonstrated using selective EP4 agonists. Aim of the present study was to evaluate the osteogenic and bone regenerative potential of the novel selective EP4 prostaglandin receptor agonist KMN-159 in vitro and in vivo.
Methods: The osteogenic differentiation capacity of rat bone marrow-derived mesenchymal stromal cells (rBM-MSCs) was investigated in vitro by alizarin red staining after continuous and bolus administration (0-100µg/mL) of KMN-159 (provided by Cayman Chemical) and compared to BMP-2 (Medtronic). Therefore, rBM-MSCs of 3 donors were cultured with and without osteogenic supplements. The in-vivo study was performed on 44 10-week old male Wistar rats, randomized into 4 groups: 1) 15µg BMP-2 (control, n=12), 2) 15µg KMN-159 (n=12), 3) 200µg KMN-159 (n=10) and 4) 2000µg KMN-159 (n=10). Therefore, mineralized collagen matrix scaffolds were functionalized with the different compounds and implanted into 5mm bone defects at the right femur of each rat following stabilization with a plate. After 12 weeks, animals were euthanized and µCT-scans and histological investigations were done on each femur. All experiments were approved by the Local Animal Care Committee (DD24-5131/354/10).
Results and conclusion: For all in vitro experiments mineralization was observed only in combination with osteogenic supplements. Higher concentrations of KMN-159 seemed to decrease mineralization. 42 rats survived the 12 week observation period, 2 animals died intraoperatively. µCT evaluation showed significantly higher bone volume when the scaffolds were functionalized with 2000µg KMN-159 (15µg BMP: 48.64±14.62, 15µg KMN-159: 50.70±15.00, 200µg KMN-159: 58.06±24.56, 2000µg KMN-159: 76.11±37.14; [mm³], mean±SD). On the other hand, bone mineral density was significantly higher in the BMP-2 group as compared to 200µg and 2000µg KMN-159 (15µg BMP: 1071±36, 15µg KMN-159: 1072±21, 200µg KMN-159: 1031±27, 2000µg KMN-159: 1006±43; [mg HA/cm3], mean±SD). Histological analysis showed a significantly higher grade of bone healing for 200µg as well as 2000µg KMN-159 as compared to 15µg KMN-159 and BMP-2, respectively (15µg BMP-2: 5.3±1.3, 15µg KMN-159: 5.2±0.7, 200µg KMN-159: 6.6±1.2, 2000µg KMN-159: 7.2±1.4; mean±SD).
KMN-159 was able to improve dose dependent bone regeneration in a critical-size defect rat model whereas bone mineral density was decreased as compared to BMP-2. The bone regenerative potential in vivo seems to be superior to the potential in vitro maybe due to the influence of different other cell types.
