Diabetes-related ultrastructural and immunohistochemical changes in human salivary gland parenchyma and a study on a native scaffold obtained from salivary gland stroma

Systemic pathologies such as diabetes and Sjögren’s syndrome, medications, and radiation therapy often affect salivary gland morphology and functionality, giving rise to changes in quantity and composition of saliva and to numerous oral complications that severely compromise the patient’s life quality. The aim of this thesis, articulated into two sections, was to evaluate: 1) if salivary gland morphology and functionality are affected by type 2 diabetes mellitus even when there are not evident signs of oral injuries; 2) the possibility to use a native scaffold derived from human salivary glands as a substrate in which salivary cells can be host to restore damaged salivary glands. The first part of the investigations was carried out with surgical samples of salivary glands obtained from subjects, half diabetics and half non-diabetics, all without evident oral diseases. The samples were processed for light and electron microscopy and random images were subjected to morphometrical evaluation. The calculations revealed diabetes-related alterations such as acinar swelling and remarkable changes in serous cells, where secretory granules appeared enlarged but reduced in their total number. On the other hand, an increased number of granules anchored to the apical membrane was found, as well as an altered number of apical vesicles and microvilli (both involved in the mechanisms of membrane recycle). Taken together these findings suggest the occurrence of difficulties in the last step of exocytosis, and demonstrate that the structures involved in the secretory process are altered by diabetes per se. Other samples were analyzed by means of immunogold staining method to reveal the ultrastructural localization of melatonin and its receptors MT1 and MT2, until now never reported. Both melatonin and receptors were reactive in the secretory granules, in cytoplasmic vesicles and on cell surfaces, suggesting that their interaction could allow melatonin storage within specific cell compartments. Melatonin staining when performed on diabetic major salivary glands highlighted changes in the labeling intensity related with the diabetic condition. 4 The second part is focused on the characterization of a native salivary gland scaffold in view of its use in gland reconstruction. As well as diabetes, radiation therapy, Sjögren’s syndrome, and several medications also give rise to salivary gland degeneration and xerostomia, but the therapies commonly used are not satisfactory so far. An emerging alternative approach to ameliorate the life quality of xerostomic patients is the regeneration of salivary parenchyma. A “Native Human Submandibular Gland Scaffold” (nHSMGS) was isolated from healthy submandibular glands, and was analyzed by light and electron microscopy and by histochemistry. Morphological examinations showed a fiber arrangement similar to that of the intact glands, while histochemistry revealed the presence of collagen type I, III, and IV. Then, a human salivary gland cell line and human fibroblasts were seeded and cultured on the scaffold in order to verify its reliability as autologous substrate for cells expansion. Results showed that a high cell percentage was proliferating after 4 days of culture, and that most cells were still alive after 8 days. All these data encourage the use of the nHSMGS as autologous scaffold in which expand salivary cells for the restoring of damaged salivary glands.