Association of MMP-2 and MMP-9 expression with recurrences in primary spontaneous pneumothorax

Primary spontaneous pneumothorax (PSP) is a common benign problem. However, PSP recurrence is still a troublesome complication for most patients. This study intended to determine the role of matrix metalloproteinase-2 (MMP-2) and MMP-9 in type II pneumocytes of patients with PSP and its relation with recurrence. Ninety-one patients who had undergone needlescopic video-assisted thoracoscopic surgery wedge resection of lung with identifiable blebs for PSP were included in this study. Immunohistochemical (IHC) staining was used to measure the expression of MMP-2 and MMP-9 in lung tissues of PSP patients. The results were further correlated with clinicopathological parameters and recurrence rates using chi-square or Fisher's exact test. The value of MMP-2 and MMP-9 for overall recurrence was analyzed by univariate and multivariable Cox regression model. IHC data revealed that MMP-2 and MMP-9 staining was predominantly observed in type II pneumocytes of patients with PSP. We found that MMP-2 and MMP-9 expression in PSP, especially male PSP patients, was significantly correlated with recurrence. In the univariate and multivariate analyses, MMP-2 and MMP-9 were statistically significant risk factors for overall recurrence in PSP patients. Therefore, high expression levels of MMP-2 and MMP-9 in type II pneumocytes show a positive correlation with PSP recurrence risk. Further studies are needed to validate whether reduction of MMP-2 and MMP-9 expression may be a promising way for decreasing the risk of PSP recurrence in the future.