ABSTRACT 

Objective: To elucidate the possible outcome of mesenchymal stem cells extracted from the bone marrow (BMMSCs) on the altered histological structure of the parotid gland of male rats with induced hypothyroidism. 

Design: 24 adult male Wistar rats were used. The rats were divided into 3 groups, each containing 8 animals. The control group contained the sham-operated animals. The hypothyroid rat group (HT group) contained animals receiving carbimazole at a dose of 20 mg/kg per day up to 6 weeks to induce hypothyroidism. The third group contained rats with induced hypothyroidism and were administered BM-MSCs via the tail vein (HT-MSC) group. BM-MSCs were extracted from 3-week-old rats and were immunophenotyped prior to injection to the HT-MSC group. The parotid glands were dissected 6 weeks post injection and processed to assess PKH67-labelled cells, histomorphometry and staining with Haematoxylin and Eosin (H and E).

 Results: Rats with induced hypothyroidism depicted a significant decrease in the thyroid hormones´serum levels. Extracted BM-MSCs were CD105 + , CD90 + and CD45- . The parotid gland of HT group depicted an abnormal structure of the acini, intercalated, striated and excretory ducts including nuclear alterations, vacuolization and indistinct boundaries compared to their controls. In addition, the area and perimeter of the acini were diminished. The HT-MSCs group depicted green PKH67+-labelled MSCs, restoration of the normal acinar and ductal configuration, and regular area and perimeter of the acini. 

Conclusion: Transplanted BM-MSCs resumed the normal parotid gland acinar, intercalated, striated and excretory duct structure in the hypothyroid male rats, suggesting restored tissue function.