Role of Mesenchymal Stem Cell Exosomes and Injectable Platelet Rich Fibrin on Structure and Function of Submandibular Salivary Gland of Aged Albino Rats

Abstract
To compare the efficacy of using bone marrow mesenchymal stem cell (BM-MSC) exosomes and injectable platelet rich fibrin (i-PRF) on the submandibular salivary glands (SMGs) of aged albino rats in restoring salivary gland structure and function. A total of 40 healthy male albino rats were used, two for obtaining the BM-MSCs, 10 for i-PRF preparation and seven adult rats (6-8 months old) represented the control group (Group 1). The remaining 21 rats were aged (18-20 months old) and divided into three groups of seven rats each; (Group 2): received no treatment, (Group 3): each rat received a single intraglandular injection of BM-MSC exosomes (50 μg/kg/dose suspended in 0.2 ml PBS), and (Group 4): each rat received a single intraglandular injection of i-PRF (0.2 mL). One month later, glands were dissected and examined histologically for structural changes. Function was assessed via immunohistochemical examination using aquaporin-5 (AQP5) and enzyme linked immunosorbent assay (ELISA) for nerve growth factor (NGF) then analyzed statistically. Histologically, Group 1 showed normal acini and duct histology. Group 2 showed structural degeneration in acini and different duct systems. Treated groups represented signs of regeneration in the form of uniform duct systems and acini similar to Group 1. Immunohistochemical examination revealed increased immuno-expression of AQP5, while ELISA showed decreased NGF in all treated groups in relation to the aged group, and this was proven statistically. Aging causes deterioration in structure and function of the SMGs. BM-MSC exosomes and i-PRF can alleviate the damaging effect of aged SMGs.