Objective(s): َAutologous bone transplantation known as the “gold standard” to reconstruction of osseous defects has known disadvantages. This study was designed to explore the effect s of hydroxy-apatite/tricalcium-phosphate (HA/TCP) and platelet -rich plasma (PRP) on the osteogenesis ability of human adipose-derived mesenchymal stem cells (hAdMSCs) in vitro and in vivo. Materials and Methods: hAdMSCs were incubated with HA/TCP granules and/or PRP in vitro and then, cell proliferation and differentiation was assessed by MTT assay, AZR S staining and SEM examination. In vivo, four cylindrical defects were drilled in the mandibular bones of 5 mongrel dogs and divided randomly into the following groups: I-autologous crushed bone, II-no filling material, III-HA/TCP and PRP, IV-PRP-enriched hAdMSCs seeded on HA/TCP granules. Inserted hAdMSCs were labeled to trace their contribution to bone tissue regeneration. Finally, cell tracing and tissue regeneration were evaluated by immunohistochemistry and histomorphometry methods, respectively. Results: In vitro, co-incubation with HA/TCP granules significantly reduced proliferation and osteogenic differentiation ability of hAdMSCs; while PRP application promoted these capacities (P<0.05). In vivo, PRP-enriched hAdMSCs seeded on HA/TCP granules induced considerable bone formation in osseous defects (P<0.05). It was obviously shown that hAdMSCs were incorporated into the newly -formed bone. Conclusion: Based on this study, application of stem cells could offer a helpful therapeutic tool in bone tissue regeneration. Although inserted hAdMSCs were identifia ble throughout the newly formed bone tissue, their few number could be an indicator of indirect role of hAdMSCs in tissue regeneration.

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