Exogenous recombinant human BMP-2 has little initial effects on human osteoblastic cells cultured on collagen type I coated/noncoated hydroxyapatite ceramic granules.
OBJECTIVE
Tissue engineering of bone entails the successful interplay between osteoinductive factors, osteogenic cells, their extracellular environment, and an osteoconductive biomaterial scaffold. Naturally produced ceramics, like hydroxyapatite (HA) calcified from red algae, are the most promising materials for use as scaffolds in this field. We hypothesized that extracellular matrix compartments and osteoinductive factors could further ameliorate the bioactivity of the scaffold.


METHODS
Osteosarcoma cells with proven osteogenic phenotype (SaOS-2) were cultured onto type I collagen coated (Coll I/HA) and noncollagen coated HA granules (NC/HA) gained from red algae (C GRAFT/Algipore). Cells grown on tissue culture polystyrene dishes (TCPS) were used as controls. Second, SaOS-2 cells cultured on Coll I/HA, NC/HA, and TCPS were treated with recombinant human bone morphogenetic protein-2 (rhBMP-2) in different concentrations (10, 100, and 500 ng/mL). Non rhBMP-2-treated cultures were used as controls. Cultures of both experiments were grown under osteogenic differentiation conditions and after 24, 48, and 72 hours assays for cell viability, apoptosis, alkaline phosphatase activity (ALP), and osteocalcin (OC) secretion were done.


RESULTS
Coating of HA granules with type I collagen showed higher cell viability in rhBMP-2-treated and nontreated cells. Supplementation of cultured cells with exogenous rhBMP-2 showed a dose-dependent effect only in the TCPS group. No alterations of the apoptotic rate within 1 investigation group were found. Addition of rhBMP-2 did not significantly alter the specific OC secretion of cells grown on Coll I/HA and TCPS.


CONCLUSIONS
These in vitro findings show that in the initial period of cultivation and up to 72 hours, the coating of HA granules with collagen type I had positive effects on cell viability and osteoblastic characteristics of osteoblastic cells. In contrast, the supplementation with exogenous rhBMP-2 shows no dose-dependent effects. The combination of collagen type I and exogenous rhBMP-2 did not ameliorate the bioactivity of hydroxyapatite calcified from red algae in the initial period of cultivation.
Turhani
Dritan
D
Department of Cranio-Maxillofacial and Oral Surgery, Medical University of Vienna, Vienna, Austria. dritan.turhani@meduniwien.ac.at
Weissenböck
Martina
M
Stein
Elisabeth
E
Wanschitz
Felix
F
Ewers
Rolf
R
D000469:Alkaline Phosphatase / Q000096:biosynthesis; D017209:Apoptosis / Q000187:drug effects; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D018786:Bone Substitutes; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D020099:Coated Materials, Biocompatible; D024042:Collagen Type I; D004305:Dose-Response Relationship, Drug; D017886:Durapatite; D006801:Humans; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000494:pharmacology*; D023822:Tissue Engineering / Q000379:methods*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
C483718:Algipore; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D018786:Bone Substitutes; D020099:Coated Materials, Biocompatible; D024042:Collagen Type I; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D015675:Osteocalcin; D017886:Durapatite; D000469:Alkaline Phosphatase