Original Article

The Anaphylatoxin Receptor C5aR Is Present During Fracture Healing in Rats and Mediates Osteoblast Migration In Vitro

Ignatius, Anita MD; Ehrnthaller, Christian MD; Brenner, Rolf E. PhD; Kreja, Ludwika PhD; Schoengraf, Philipp; Lisson, Patricia; Blakytny, Robert PhD; Recknagel, Stefan; Claes, Lutz PhD; Gebhard, Florian MD; Lambris, John D. PhD; Huber-Lang, Markus MD

Author Information

From the Institute of Orthopaedic Research and Biomechanics (A.I., L.K., P.S., R.B., S.R., L.C.); Department of Traumatology, Hand-, Plastic-, and Reconstructive Surgery (C.E., P.L., F.G., M.H.-L.), Center of Surgery; Department of Orthopaedics (R.E.B.), Division for Biochemistry of Joint and Connective Tissue Diseases, Center of Musculoskeletal Research, University of Ulm, Ulm, Germany; and Department of Pathology and Laboratory Medicine (J.D.L.), University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.

Submitted for publication June 16, 2010.

Accepted for publication August 22, 2010.

Supported by the German Research Foundation (DFG, No. KFO200) and National Institutes of Health grants (AI-068730).

The authors disclose that they received funding from any other sources except the German Research Foundation and National Institutes of Health.

Paper presented at the meetings of the ORS Annual Meeting 2010, New Orleans, LA.

Address for reprints: Prof. Dr. Anita Ignatius, Institute of Orthopaedic Research and Biomechanics, University of Ulm, Helmholtzstrasse 14, 89081 Ulm, Germany; email: [email protected].

The Journal of Trauma: Injury, Infection, and Critical Care 71(4):p 952-960, October 2011. | DOI: 10.1097/TA.0b013e3181f8aa2d

Abstract

Background: 

There is evidence that complement components regulate cytokine production in osteoblastic cells, induce cell migration in mesenchymal stem cells, and play a regulatory role in normal enchondral bone formation. We proved the hypothesis that complement might be involved in bone healing after fracture.

Methods: 

We investigated the expression of the key anaphylatoxin receptor C5aR during fracture healing in rats by immunostaining after 1, 3, 7, 14, and 28 days. C5aR expression was additionally analyzed in human mesenchymal stem cells (hMSC) during osteogenic differentiation, in human primary osteoblasts, and osteoclasts by reverse transcriptase polymerase chain reaction and immunostaining. Receptor functionality was proven by the migratory response of cells to C5a in a Boyden chamber.

Results: 

C5aR was expressed in a distinct spatial and temporal pattern in the fracture callus by differentiated osteoblast, chondroblast-like cells in cartilaginous regions, and osteoclasts. In vitro C5aR was expressed by osteoblasts, osteoclasts, and hMSC undergoing osteogenic differentiation. C5aR was barely expressed by undifferentiated hMSC but was significantly induced after osteogenic differentiation. C5aR activation by C5a induced strong chemotactic activity in osteoblasts, and in hMSC, which had undergone osteogenic differentiation, being abolished by a specific C5aR antagonist. In hMSC, C5a induced less migration reflecting their low level of C5aR expression.

Conclusions: 

Our in vitro and in vivo results demonstrated the presence of C5aR in bone forming osteoblasts and bone resorbing osteoclasts. It is suggested that C5aR might play a regulatory role in fracture healing in intramembranous and in enchondral ossification, one possible function being the regulation of cell recruitment.

© 2011 Lippincott Williams & Wilkins, Inc.

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