Growth factor effects on passaged TMJ disk cells in monolayer and pellet cultures

Previously, we demonstrated rapid changes in temporomandibular joint (TMJ) disk gene expression during monolayer expansion. This study's objective was to investigate the ability of pellet culture and growth factors to rescue TMJ disk gene expression changes.

Temporomandibular joint disk cells were isolated from mature porcine tissue and passaged up to five times. At each passage, 300 000 cells were placed in a monolayer or pellet culture environment before being exposed to transforming growth factor-beta 3 (TGF-beta3) (5 ng/ml), TGF-beta1 (5 ng/ml), and insulin-like growth factor I (IGF-I) (10 ng/ml).

After 24 h, gene expression was analyzed via reverse transcriptase-polymerase chain reaction (RT-PCR).

Pelleting was detrimental to TMJ disk gene expression, marked by gene expression decreases in collagen type I (5.5-fold), aggrecan (1.4-fold), decorin (0.73-fold), and biglycan (0.73-fold) relative to monolayer cultures. IGF-I, TGF-beta1, and TGF-beta3 demonstrated limited ability to rescue TMJ disk gene expression in the pellet culture. In monolayer, TGF-beta3 and TGF-beta1 increased decorin and biglycan gene expression relative to passaged controls. Collagen type I expression, the TMJ disk's primary matrix constituent, was highest in TGF-beta3 cultures; however, differences were not statistically significant.

These results indicate that pellet cultures are a poor choice for TMJ disk tissue engineering, and the effects of TGF-beta1, TGF-beta3, and IGF-I on TMJ disk gene expression are minimal relative to passaging and pelleting effects.