Expression of Alpha-smooth Muscle Action in Goat Temporomandibular Joint Disc and Its Effect on Self-Assembled Engineered Constructs

Purpose of this study was to investigate the expression of smooth muscle action-alpha (α-SMA) in native goat temporomandibular joint (TMJ) disc and in self-assembled construct of TMJ disc. Expression of a-SMA in native one-month-aged goat TMJ disc was examined by immunohistochemistry (IHC) method. TMJ disc cells were isolated from one-month-aged goat TMJ discs with 0.1% type I collagenase and passaged to P3 for tissue engineering. 5.5×10(6) cells were seeded into 5 mm diameter wells filled with 2% agarose gels in which 10μg/L IGF-I growth factor was added to stimulate mature process of self-assembled constructs of TMJ disc. Dimensions, forms and weights of constructs were measured respectively at the second, fourth, sixth and eighth week. IHC staining was used to examine the distribution of α-SMA in self-assembled constructs. The IHC staining for α-SMA was globally uniformly distributed in all four groups of self-assembled constructs and expressed the strongest in the second group. This experiment also confirmed that much more significant expression of α-SMA in self-assembled constructs than in the native TMJ disc tissue. Conclusively, α-SMA could take part in the regulating developmental process of engineered construct and may be used partially to explain the reason why TMJ disc self-assembled constructs become much smaller and denser during its growth and development due to its volume shrinkage.