Effects of human adipose-derived stem cells on the regeneration of damaged visceral pleural mesothelial cells: a morphological study in a rabbit model.

OBJECTIVES Although an alveolar air leak (AAL) after pulmonary resection is a troublesome complication that diminishes a patient's quality of life and increases medical costs, current treatment and preventive methods for AAL are not effective. Therefore, we transplanted adipose-derived stem cells (ASCs) to the damaged visceral pleura to facilitate the regeneration of mesothelial cells and investigated the possibility of cell therapy as a treatment option for AAL. METHODS Stem cells were isolated and cultured from discarded fat tissues that were collected after liposuction procedures. Flow cytometry analysis was performed to evaluate their suitability as mesenchymal stem cells. Cultured stem cells were seeded onto polyglycolic acid (PGA) sheets and incubated for 5 days. Under general anaesthesia, 10 New Zealand rabbits underwent thoracotomies. After the visceral pleura was damaged, PGA sheets containing ASCs were transplanted into 5 rabbits (ASC group) and PGA sheets without cells were transplanted into the other 5 rabbits (control group). Rethoracotomies were performed after 4 weeks, and the transplanted areas in the visceral pleura were excised for analysis. Haematoxylin and eosin and Azan staining were performed. In addition, electron microscopic examinations were performed to investigate the ultrastructure of the regenerating mesothelium. RESULTS Cultured stem cells were positive for the surface proteins CD13, CD29, CD49d, CD90 and CD105, whereas they were negative for CD34, CD45 and human leukocyte antigen (HLA)-DR. The adhesions between the transplanted visceral pleura and parietal pleura were weaker in the ASC group than in the control group. On histological examination, the mesothelial cell monolayer of the visceral pleura was well preserved in the ASC group, whereas it was frequently lost in the control group. Electron microscopy demonstrated that the mesothelial cell monolayer and its abundant microvilli were well preserved in the ASC group, but were absent or disintegrated in the control group. CONCLUSIONS Transplantation of ASCs to the damaged visceral pleura can contribute to the treatment and prevention of AAL by improving the regeneration of mesothelial cells.