Intravenous administration of adipose-derived stromal cells does not ameliorate bleomycin-induced lung injury in rats

Background: Mesenchymal stromal cells (MSCs) have been studied intensively in regenerative medicine. Among MSCs, adipose tissue-derived stromal cells (ASCs) are relatively easy to obtain from a patient. Since ASCs are ideal candidates for use in the treatment of disease states including pulmonary fibrosis, we investigated whether intravenous injection of ASCs could exert a therapeutic effect against bleomycin-induced lung injury in rats. Methods: Rats were intratracheally administered bleomycin, and one week later ASCs were isolated and cultured. Two weeks after bleomycin treatment ASCs or PBS (phosphate-buffered saline) were injected to the rats. Three or six weeks after bleomycin instillation, the total cell counts and their profile in bronchoalveolar lavage fluid (BALF) were measured, and a histological evaluation was semi-quantitatively assessed for the injured lungs, followed by cell tracing. Results: The BALF cell counts and its profiles were not significantly different in the ASCs and PBS groups. Furthermore, ASC treatment led to no significant histological effect compared with the PBS treatment. Using a fluorescent cell tracer, it was noted that the ASCs homed to the injured lung areas, but some ASCs accumulated around scars, and scarcely migrated into the fibrotic areas. Conclusions: In the present study, the intravenous administration of ASCs could not reduce the severity of bleomycin-induced lung injury in a rat model. Although the ASC counts and passage numbers were suitable, the older age and fibrotic disease stage of the rats were likely responsible for the treatment failure.