Cooperative effects in differentiation and proliferation between PDGF-BB and matrix derived synthetic peptides in human osteoblasts.

BACKGROUND: Enhancing osteogenic capabilities of bone matrix for the treatment of fractures and segmental defects using growth factors is an active area of research. Recently, synthetic peptides like AC- 100, TP508 or p-15 corresponding to biologically active sequences of matrix proteins have been proven to stimulate bone formation. The platelet-derived growth factor (PDGF) BB has been identified as an important paracrine factor in early bone healing. We hypothesized that the combined use of PDGF-BB with synthetic peptides could result in an increase in proliferation and calcification of osteoblast-like cells. METHODS: Osteoblast-like cell cultures were treated with PDGF and synthetic peptides, singly and as combinations, and compared to non-treated control cell cultures. The cultures were evaluated at days 2, 5, and 10 in terms of cell proliferation, calcification and gene expression of alkaline phosphate, collagen I and osteocalcin. RESULTS: Experimental findings revealed that the addition of PDGF, p-15 and TP508 and combinations of PDGF/AC-100, PDGF/p-15 and PDGF/TP508 resulted in an increase in proliferating osteoblasts, especially in the first 5 days of cultivation. Proliferation did not significantly differ between single factors and factor combinations (p > 0.05). The onset of calcification in osteoblasts occurred earlier and was more distinct compared to the corresponding control or PDGF stimulation alone. Significant difference was found for the combined use of PDGF/p-15 and PDGF/AC-100 (p < 0.05). CONCLUSIONS: Our findings indicate that PDGF exhibits cooperative effects with synthetic peptides in differentiation and proliferation. These cooperative effects cause a significant early calcification of osteoblast-like cells (p < 0.05). We suggest the combination of synthetic peptides and PDGF as a potential clinical approach for accelerating bone healing or coating osteosynthesis materials.

Evaluation of platelet gel characteristics using thrombin produced by the thrombin processing device: a comparative study.

PURPOSE: Autologous platelet gels can be prepared using the patient's own platelet-rich plasma and thrombin produced by the Thrombin Processing Device (Thermogenesis Corp, Rancho Cordova, CA). As the Thrombin Processing Device thrombin contains a residual amount of ethanol, the purpose of this study was to investigate the effect of the Thrombin Processing Device thrombin on growth factor release from platelet gels, and the effect on cell viability and cell proliferation. MATERIALS AND METHODS: Platelet gels were prepared using Thrombin Processing Device-produced human thrombin at platelet-rich plasma to thrombin ratios of 3.3 to 1 and 7 to 1. Commercially available bovine thrombin was used as control. The content of the growth factors, platelet-derived growth factor beta polypeptide, and transforming growth factor beta, were assessed in both the clot and supernatant. The influence of different concentrations of ethanol on cell viability was assessed by flow cytometry and cell proliferation was assessed by (3)H-thymidine incorporation. RESULTS: Using a ratio of 3.3 to 1, the supernatant of the platelet gel produced with Thrombin Processing Device thrombin had a lower growth factor content compared with bovine thrombin but was similar when prepared using a ratio of platelet-rich plasma to thrombin of 7 to 1. Supernatants from the platelet gels did not affect the viability of human macrophage line cells or a fibroblast cell line. When the different platelet gels or their supernatants were tested for their ability to stimulate cell proliferation, similar rates of proliferation were observed. CONCLUSIONS: These data suggest that residual ethanol in the Thrombin Processing Device-produced thrombin does not affect any of the tested parameters and has similar characteristics as commercially available bovine thrombin.