| Adult type 2 alveolar epithelial(AT2)cells are stem/progenitor cells of alveolar epithelial cells that have the ability to self-renew and differentiate into alveolar type 1(AT1)cells after lung injury.Under normal physiological conditions,the alveoli can quickly repair and regenerate new alveolar epithelial cells to restore the intact epithelial barrier after acute injury to the lung tissue.The protective function of this lung tissue barrier gradually is impaired with aging,leading to the development of chronic lung diseases.However,the effects of aging on the regeneration of alveolar AT2 stem cells during physiological conditions or tissue repair after injury were not very clear.Here,we investigated the effect of aging on regeneration of AT2 cells via bleomycin(BLM)induced lung injury mouse model,AT2 cells were separated for single-cell RNA sequencing(scRNA-seq)analysis to the differential gene expression of aging on AT2 stem cells under physiological conditions and after BLM injury,providing new clues for the mechanism of aging on regeneration of AT2 cells.In this study,a lung injury model was established in 3-month old mice and 12-month old mice by BLM treatment.Interestingly,we found that the 12-month old mice have already show impaired physiological function of AT2 cells.The tissue repair capacity of 12-month old mice after lung injury has begun to decline.In order to observe the difference between aged mice and young mice after BLM lung injury,it was found that the difference of severity of lung injury post BLM in aged and young mice at day 30 was not obvious.The lung injury of 3-month old mice could be completely recovered in the late phase(day 42 and 63)after BLM treatment,while the recovery of lung injury in 12-month old mice was slower or even cannot fully recover.The subsequent study on regeneration of AT2 cells has shown the abnormal regeneration of AT2 cells in 12-month old mice,especially the impaired differentiation capacity of AT2 cells.To further analyze differences in transcriptome levels of AT2 cells during repair of lung injury in aged and young mice,we used scRNA-seq to analyze the distinct AT2 cells clusters and differential gene expression from vehicle and BLM treated lungs.Firstly,we analyzed the difference of AT2 cell clusters between control and BLM injured mice lung.It was found that the AT2 cell clusters of vehicle and BLM treatment were distinctly separated into two cell clusters,indicating that the differential gene expression of AT2 cells between vehicle and BLM treatment.Next,the difference between AT2 cells in aged and young mice under physiological conditions was analyzed.The tSNE plot showed that the difference between 3-month and 12-month old AT2 cells after vehicle treatment were not very obvious.The genes highly expressed in AT2 cells of 3-month old mice was found to be related with protein folding,and the genes highly expressed in AT2 cells of 12-month old mice are mainly related to immune responses.In addition,the AT2 cell clusters of 12-month old mice were different from that of 3-month old mice,indicating that aging has a greater effect on the response of AT2 cells to bleomycin-induced lung injury.We found that the gene expression of the two AT2 cell clusters is quite different via analyzing the gene expression of 12-month and 3-month old AT2 cells after injury.The genes highly expressed in 3-month old mice are mainly involved in lipid and cholesterol metabolism,while the genes highly expressed in 12-month old mice are mainly related to immune response.The experimental results show that the abnormal AT2 cell regeneration caused by aging may be one of the important reasons for the repair of lung injury in 12-month old mice.The expression of genes related to lipid and sterol metabolism was decreased in 12-month old mice after BLM treatment,and the immune-related genes of AT2 cell was highly expressed in 12-month old mice under physiological and injury conditions,which looking forword to finding out possible genes or signaling pathways related with aging,lipid metabolism,and immune response to provide clues for mechanism of abnormal AT2 cell regeneration induced by aging. |
PDF Full Text Request