SHH and acute respiratory distress syndrome: Therefore, the transplantation of BMSCs inhibited by the Shh pathway in mice with ALI failed to alleviate lung injury; conversely, the regeneration of AT2 cells was impaired by reducing the efficiency of BMSC differentiation into AT2 cells and inhibiting AT2 cells proliferation (due to damage to BMSC paracrine function), ultimately weakening the therapeutic potential of BMSCs in the treatment of ALI/ARDS.