Study Of Osteoblast Adhesion And Proliferation And Carcinogenisis Based On Polyhydroxyalkanoates Matrices

Polyhydroxyalkanoates (PHA) have been developed for applications as medical implants, because of their flexible mechanical strengths, biodegradability and biocompatibility. Lots of studies showed that PHA matrices improved cell proliferation and tissue regeneration.Here, integrin regulation of cell behaviour using rat osteoblasts on PHA matrices was investigated. PHA (PHB / PHBV / P3HB4HB (P34HB) / PHBHHx / PHBVHHx) films could support cell adhesion and growth in the same way as TCP and PLA did. However, cells on PHBHHx and PHBVHHx films presented less cell proliferation and more apoptotic and necrotic cell death compared with other tested films. Furthermore, cells had a higher expression level of integrin subunitα2 on PHBHHx film, and a higher expression level of integrin subunitβ3 on PHBHHx and PHBVHHx films among the films studied. Nevertheless, cells on all films showed similar expression of focal adhesive protein paxillin and vinculin, focal adhesion kinase (FAK) and phosphorylated FAK (pY397), and FAK activation (the ratio of pFAK to FAK). In addition, cells on PHBHHx and PHBVHHx films revealed less Cyclin D1 mRNA transcript levels compared with TCP although the difference was not obvious. Considering the important role of integrin-mediated focal adhesion and intracellular signaling in anchorage-dependent cell function, the results indicated that PHA as extracellular matrix (ECM) affected cell adhesion and proliferation; they may be regulated by integrinα2 andβ3 expression.However, the possibility of whether rapid cell proliferation on PHA matrices will induce tumor formation is unclear. Here we confirmed that proliferating rat osteoblasts grown on PHA films did not lead to cancer induction at least for p8th. Cell proliferation was evaluated by the incorporation of 5-bromodeoxyuridine (BrdU), the transcript expression of cancer related genes Ki67, p53 and c-Fos were monitored by quantitative Real-time PCR, the results showed the cells proliferating on the PHA films were under normal cell cycle regulation. Moreover, DNA aneuploid and telomerase activity were only detected in the positive control UMR-108 cells; compared with cells grown on films, UMR-108 cells had longer telomeres, further demonstrated the normal status of cells proliferating on the PHA films. It indicated that the above PHA family members could be used to support cell growth without indication of susceptibility to tumor induction.These results will be important for promoting the application of PHA as new implant biomaterials.