الفهرس 
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Abstract
The present work aimed to assess the possible regenerative potential of Microvesicles versus Bone marrow mesenchymal stem cells on parotid glands of irradiated albino rats. The study was carried out on forty eight adult healthy male albino rats weighing about 200-250 grams. The animals were classified into three main equal groups of 16 rats. All the rats were subjected to a dose of radiation of 10 Gy. The rats of group A received no treatment after irradiation. Rats of group B recieved a single dose of 1×106 cells/mL of BMSCs injected intravenously, immediately after irradiation. Whereas, the rats of group C received a single intravenous injection of 30 μg of BMSCs derived MVs immediately after irradiation. The animals were fed the normal laboratory diet ad libitum throughout the experimental period. At the end of the experiment, the animals were sacrificed and the parotid glands were dissected out and processed to be embedded in paraffin wax. Sections of five microns were cut and mounted on glass slides to be stained with H&E for histopathological study. For immunohistochemical examination, the paraffin sections were mounted on positively charged microscopic glass slides for evaluation of expression of epidermal growth factor receptor (EGFr).
Single total body irradiation dose of 10 Gy was found to induce marked degenerative changes within rat parotid glands. group A (irradiated only) showed obvious increase in the immuno expression of epidermal growth factor receptor (EGFr) as well as levels of secretory immunoglobulin A (sIgA). Degenerative changes induced by irradiation decreased by immediate injection of either bone marrow stem cells (BMSCs) or microvesicles (MVs) derived from BMSCs. These changes were less obvious on day 7 and the parotid gland seemed close to normal especially in the MVs group. BMSCs and MVs were also found to decrease the immuno expression of epidermal growth factor receptor (EGFr) caused by irradiation as well as levels of secretory immunoglobulin A (sIgA).