Potentiation of Osteogenesis and Angiogenesis In Vivo after Implantation of Hydroxyapatite Combined with Autogenous Growth Factors

Abstract

Objective: Growth factors accelerate healing by stimulating matrix production and potentiating angiogenesis. In order to determine whether analogous effects of growth factors can be observed during the early phase of fracture healing, the use of hydroxyapatite (HA) combined with autogenous growth factors was investigated in the present study. For the acquisition of autogenous growth factors the platelet-rich plasma fraction was separated from blood by means of centrifugation.
Design: For the experimental procedure two cylindrical defects were created within the intercondylar region of pig femoral condyles. The proximal defect was filled with HA, the distal with HA enriched with growth factors. Ten and twenty days after surgery the specimens were examined immunohistochemically and ultrastructurally. In order to study angio- and osteogenesis, antibodies to factor VIII, ED-A and, ED-B fibronectin, and to α smooth muscle actin were used.
Results: Even after ten days there was a distinct increase of neovascularisation due to the application of growth factors as demonstrated with factor VIII and ED-B fibronectin antibodies. Moreover, granulation tissue formation was accelerated. After ten days intense labelling for α smooth muscle actin and ED-A fibronectin was observed only in combination with growth factors. Due to the effects of growth factors there is activation of fibroblasts to synthesise the ED-A fibronectin necessary for the induction of myofibroblasts by growth factors. Additionally, a few ED-B positive areas of woven bone including osteoblasts were identified ultrastructurally within the defect area after ten days of local treatment with growth factors. Moreover, the cells responsible for the accelerated degradation of the implant enriched with growth factors were identified ultrastructurally.
Conclusion: Platelet growth factors added to biodegradable hydroxyapatite stimulate angio- and osteogenesis during bone defect healing.

Key words

Osteogenesis - angiogenesis - hydroxyapatite - platelet growth factors

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