Early Regeneration Occuring in Rat Submandibular Gland after Ligation-Induced Atrophy

Rat submandibular gland can recover from atrophy by regenerating new salivary gland tissue, regaining normal size and function. However, how this process takes place is still not clear. Objectives: to look for early markers of regeneration in rat submandibular gland. Methods: 12 rats (250-350g) have been used. Atrophy was induced by applying a metal clip, under recovery anaesthesia, on the main duct of the submandibular gland through a hole in the floor of the mouth. Ligation did not include the chorda lingual nerve. After 2 weeks the glands of 5 rats were removed and weighed, the other 5 rats were deligated for 3 days, and then the glands were collected. Tissue was fixed for histological analysis and some digested with collagenase for immunocytochemistry and examined by confocal laser microscopy. Tissue from 2 non operated rats was used as control. Results: with 2 weeks ligation submandibular glands show a 50% weight reduction and almost complete loss of secretory granules from acini and ducts, with an apparent increase in the proportion of the ducts. H&E staining of 3 days deligated glands shows some acini have increased in size, and the loss of Alcian blue/PAS staining in the lumen of the ducts suggests the presence of salivary flow, even though the glands weight did not change significantly. As myoepithelial cells surround the acini changes in their morphology might reflect changes in acini morphology, therefore an Actin staining was performed. Surprisingly Actin revealed the presence of acini groups, although shrunken, in the ligated only tissue. In the recovered tissue the myoepithelial cells regained some of their normal morphology suggesting the acini had recovered. Conclusion: this study suggests that some evidence of glandular regeneration can be seen after only 3 days following removal of the ligation. The authors acknowledge the support of the Wellcome Trust.