An experimental study of menopause induced by bilateral ovariectomy and mechanistic effects of mesenchymal stromal cell therapy on the parotid gland of a rat model

The current study was conducted on a menopause rat model induced by ovariectomy to assess the histological and immunohistochemical alterations in the parotid glands and to verify the efficiency of human umbilical cord derived-mesenchymal stromal cell (hUCB-MSCs) in treating this condition. Eighteen adult female rats were equally divided into three groups: sham-operated (SHAM), ovariectomized (OVX) and OVX injected with hUCB-MSCs (OVX + hUCB-MSCs). At 3 months post-ovariectomy, the salivary flow rate and size of the parotid glands were measured. The parotid glands were histologically investigated via H&E stained sections. Furthermore, immunohistochemical analysis for human CD105, human CD34, proliferating cell nuclear antigen (PCNA), single strand DNA (ssDNA), caspase 3, aquaporin (AQP)1, α-smooth muscle actin (α-SMA) and mouse CD34 were performed. The OVX group showed interstitial hemorrhage, dispersed acini and intracytoplasmic vacuoles in the acinar cells. Furthermore, immunohistochemical staining revealed a significant decrement in the number of ssDNA positive apoptotic cells, but a significant increment of PCNA positive proliferating cells, AQP1 positive blood capillaries, α-SMA positive myoepithelial cells and endogenous CD34 positive hematopoietic progenitor cells in the OVX + hUCB-MSCs group as compared with the OVX group. These findings suggest a potential regenerative therapy of MSCs to injured parotid gland structures. However, further investigations are required to illustrate the mechanism of hUCB-MSCs mediated parotid gland regeneration.