Bone Turnover in an Organotypic In Vitro Model of Ameloblastoma

Objectives: Ameloblastoma is a benign odontogenic tumour with extensive, local recurrence, even after surgical resection. While the mechanisms of tumour invasion and bone absorption are largely unknown, recent investigations have indicated a role of the osteoprotegerin (OPG) / receptor activator of NF-κB ligand (RANKL) regulatory mechanisms in bone absorption in these tumours. Three-dimensional in vitro organotypic scaffolds can be used for modelling this bone-destructive neoplasm. In this study, tissue-engineering techniques were used to develop a three-dimensional organotypic model to study the behaviour of the tumour cells and gene expression relating to bone turnover. This will allow for characterisation of the tumour and for future treatments to prevent tumour growth and invasion to be developed and applied in a relevant in vitro setting.
Methods: Co-culture scaffolds were created by incorporating ameloblastoma cells (AM-1 cell line) into cellularised, pre-mineralised bone-like constructs. These were then incubated up to 14 days to allow for tumour cell expansion. Cell behaviour and interactions in the scaffolds was analysed using confocal microscopy. Expression of genes involved in bone turnover was quantified at different time points. Anti-infiltrative agents acting on specific, dysregulated pathways were then applied to test for therapeutic effect.
Results: Ameloblastoma cells in the scaffolds provided an organotypic model for the tumour in an in vitro setting and exhibited characteristics typical of this tumour type. Preliminary gene expression analysis revealed an increase in the expression of RANKL in the ameloblastoma co-culture models when compared with single cell type cultures, indicating aberrant bone turnover in the ameloblastoma tumour.
Conclusions: An in vitro cellularised, organotypic model of ameloblastoma enables close characterisation of the tumour pathogenesis, as presented here. These results provide indications towards the bone absorption caused by the ameloblastoma tumour. This model can also be used as a supplementary method for high-throughput screening of anti-infiltrative agents prior to clinical studies.