Gingival mesenchymal stem cells inhibited senescence of type Ⅱ alveolar epithelial cells and prevented radiation-induced pulmonary fibrosis / 中华放射医学与防护杂志

ABSTRACT

Objective:To investigate whether transplantation of gingival mesenchymal stem cells (GMSCs) can inhibit radiation-induced senescence of alveolar epithelial cells type Ⅱ (AECⅡ) and its role in the prevention of radiation-induced pulmonary fibrosis (RIPF).Methods:Mouse type Ⅱ alveolar epithelial cells (MLE12) were irradiated with 6 Gy X-rays and then co-cultured with GMSCs. The extent of cellular senescence of MLE12 cells was assessed by cell morphology, β-Gal staining, and senescence secretion-associated phenotype (SASP) assay. RIPF model was constructed by unilaterally irradiating the right chest of C57BL/6 mice with 17 Gy X-rays. GMSCs were transplanted 1 d after irradiation. At 180 d after irradiation, the pulmonary organ ratio, HE staining, and Masson staining were used to assess intra-pulmonary structure and interstitial collagen deposition in the lung. β-Gal immunohistochemistry and immunofluorescence co-localization with AECⅡ were measured to assess the degree of cellular senescence in the lung. The SASP expression changes in lung tissue were detected by qRT-PCR. The protein expressions in P53-P21 and P16 pathways were detected by Western blot assay. P21 expression in AECⅡ was detected by immunofluorescence co-localization assay.Results:GMSCs effectively inhibited radiation-induced senescence of MLE12 cells, reduced the ratio of radiation-elevated β-Gal positive cells by 11.8% ( t=6.72, P<0.05), and decreased the expressions of SASP (IL-6, IL-8, IL-1β) ( t=28.43, 28.43, 4.82, P<0.05). GMSCs transplantation improved the survival rate of irradiated mice, prevented radiation-induced alveolar structural collapse thickening and collagen deposition, reduced the number of senescent cells in the irradiated lung tissues by 23.9% ( t=21.83, P<0.05), and inhibited the expressions of SASP ( t=8.86, 20.63, P<0.05). GMSCs also inhibited the expression of P53-P21, P16-related proteins in MLE12 cells and lung tissues of mice after irradiation. Conclusions:GMSCs inhibit senescence-related P53-P21 and P16 pathways, prevent radiation-induced AECⅡ senescence, as well as the development of RIPF.