Complications associated with the use of autogenous bone in the repair or replacement of tissue lost through injury or disease have driven the search for alternative sources of graft material. Bioceramics containing hydroxyapatite (HA), tricalcium phosphate (TCP), or composites that combine the best properties of both of these materials are among the principal candidates. In this study, we have investigated the in vitro proliferation, morphology, and viability of an immortalized rat osteoblast cell line cultured on HA, TCP, and composites of the two in the ratios 75:25 (H75), 50:50 (H50), and 25:75 (H25) for 28 days. The biocompatibility of each material was examined in the presence and absence of a collagen coating. With the exception of H50, cell proliferation, quantified by carboxyfluorescein fluorescence, was enhanced by collagen coating of all materials for the first 14 days, although at later time points cell numbers were unaffected. It is notable that the collagen coating was least stable on H50, the only material not to show enhancement of cell growth on coating. Confocal laser scanning microscopy confirmed that cell growth was more extensive on coated materials over the first 7-14 days in culture, and the development of cell extensions and bridges across the pores in the materials was observed. Results indicate that collagen coating of calcium phosphate ceramics may also increase their compatibility and osseointegration in vivo.
Metabolic activity is unstable in primary hepatocyte cultures and is influenced by the matrix composition.The effect of incorporating 20% chondroitin-6-sulphate(Ch6SO4), a glycosaminoglycan, into collagen films and gels(0.3%w/v), and crosslinking the films and gels with 1,6-diaminohexane(DAH)on the glucuronidation of kaempferol by primary rat hepatocytes cultured for 48h and 7 days was investigated. Hepatocytes isolated from male Sprague-Dawley rats by collagenase perfusion were cultured(3x106/60mm Petri dish)in Chee's medium with 5% v/v foetal calf serum. Cells were incubated with 100pM kaempferol for Ih at 37°C and the glucuronides(K1 and K2)were measured by HPLC. Cells cultured on collagen films formed only the K2 metabolite after 48h in culture. The addition of Ch6SO4 or D A H significantly increased the formation of this glucuronide. However, cells seeded on gels showed no metabolism after 48h in culture. By 7 days in culture, both K1 and K2 glucuronides were formed in cells on all the different films and gels. The formation of K1 glucuronide was significantly higher with the addition of Ch6S04 to the films. K2 glucuronide was significantly higher in all of the crosslinked films compared to the plain films. Modification of collagen based substrates may improve cultured hepatocyte phenotype.
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