| Summary: | Periodontal disease is characterised by progressive gingival inflammation and degradation of the periodontal ligament (PDL) and alveolar bone. Recently, a limited number of studies have started to consider the use of tissue engineering approaches to facilitate periodontal tissue regeneration. Within the wider field of the skeletal bioengineering, research has been directed towards fabrication of aligned-fibre scaffolds and devices for reconstruction of larger ligaments and tendons for use in orthopaedic indications. Mechanical loading and growth factors are also known to influence the quality of engineered load-bearing musculoskeletal tissues; and it is increasingly being acknowledged that appropriate biomechanical cues are essential for appropriate organisation of the extracellular matrix (ECM). The aims of this study were to evalute the effect of fibre-alignment on cell behaviour and investigate the effect of either mechanical loads or growth factors on the quality of the resultant tissue engineered PDL tissue. Synthetic and natural scaffolds were prepared in aligned and random-fibre forms, and human periodontal ligament fibroblasts (HPDLFs) were cultured on these scaffolds and their biological responses were investigated. In aligned-fibre constructs, histochemical and immunochemical staining showed that HPDLFs were elongated in shape and oriented along the long-axis of the fibres and showed evidence of increased ECM deposition. Gene expression data showed that HPDLFs on aligned-fibre scaffolds expressed a more ligament-like phenotype, indicated by an increased expression of collagen type I (COL1A1) and periostin (POSTN) genes over the 20 days culture period. The results showed that static mechanical strain up-regulated the ligamentous genes namely; collagen type I, periostin and scleraxis (SCXA) with greater expression observed in aligned-fibre constructs. These effects were more marked in the aligned-fibre scaffolds. In contrast, Emdogain® (EMD) was found to promote the osteoblastic phenotype of HPDLFs as indicated by the up-regulation of alkaline phosphatase (ALPL) gene expression in the engineered tissue, while transforming growth factor beta 1 (TGF-β1) had more effect on the ligamentous genes (COL1A1, POSTN). This effect of EMD was also potentiated by the fibre-alignment of the scaffolds. EMD and TGF-β1 were observed to have a limited effect on HPDLF proliferation in the aligned-fibre constructs by day 14 of incubation regardless of whether EMD and TGF-β1 were added alone or in combination with each other. Although the exact mechanism by which EMD and TGF-β1 affected cell behaviour is unknown, the data suggested that their effects were heavily dependent on the cell phenotype and stage of differentiation which, in turn was greatly influenced by the alignment of the scaffold fibres. In conclusion, 3D tissue engineered PDL constructs, with good biological quality, can be developed using aligned-fibre scaffolds. These constructs have great potential for us as an in vitro model to study PDL regeneration and repair processes and ultimately, may inform research directed at new clinical applications.
|
|---|
