Development of temporomandibular joint ankylosis in rats using stem cells and bone graft.

64 male Wistar rats were used: 24 for the removal of stem cells, 4 as a control group, and 36 for the experiment, in which either stem cells or bone graft was used. The rats were divided into groups according to the type of procedure and time span (15, 30 or 60 days). The joints were submitted to histological study in order to score the ankylosis. The mean differences between initial and final maximal mouth opening (MMO) were gradually increased from 15 to 60 days, for all times of evaluation for both groups, being statistically significant at 15 days (p=0.045) in the bone-graft group. When both groups were compared, the mean differences between initial and final MMO were statistically significant at 15 days (p=0.018) and 30 days (p=0.029). In relation to the histological scores, in the bone-graft group almost all animals had intra-articular fibrosis at all times of evaluation (n=17). In the stem-cell group, there was new bone at 15 days (n=4), 30 days (n=3) and 60 days (n=4). The study model permitted the development of fibrous ankylosis in the majority of animals for both groups and no bony bridge was observed.

Hyperplasia of myoepithelial cells expressing calponin during atrophy of the rat parotid gland induced by duct ligation.

The number and location of myoepithelial cells in the rat parotid gland submitted to surgical ligation of its main excretory duct were studied through immunohistochemical labelling for calponin. These cells were labelled by the streptavidin-biotin method using anti-calponin primary antibody, and their number was determined during each step of glandular atrophy, i.e., at time zero (control) and 1, 7, 15, 21, 30 and 60 days after ligation. Morphological analysis showed a gradual decrease and fibrosis of the glandular lobules accompanied by disappearance of the acini and the occurrence of duct-like structures. The expression of calponin was observed in all specimens analysed, being restricted to myoepithelial cells. Labelling revealed the distribution of myoepithelial cells around the acini and intercalated ducts in the control group and around duct-like structures later during the course of atrophy. Quantitative analysis demonstrated significant increase in the number of myoepithelial cells up to day 7 post-ligation, followed by gradual increases which, however, were not statistically significant. These results suggest that myoepithelial cells proliferate intensely up to day 7 post-ligation, an event that coincides with a higher rate of disappearance of acinar cells. After this period, the elevatednumber of cells observed at the end of the previous period is maintained.