Identification of MMP-7 as a prognostic biomarker of post-COVID persistent lung abnormalities.

<bold>Background:</bold> A subset of patients with severe COVID-19 infection may present persistent lung damage. However, there are few studies on biomarkers that can predict it. Matrix metalloprotease (MMP)-7 is considered profibrotic. The aim of this study was to evaluate the serum levels of MMP-7, and the presence of post-COVID residual lung abnormalities at 1 year of follow-up. We also examined the levels of osteopontin (OPN) which have a bidirectional profibrotic effect with MMP-7. <bold>Methods:</bold> We obtained blood samples from COVID-19 patients during hospitalization at 1-year post-COVID-19 in two cohorts (derivation (n=42) and verification (n=22). We evaluated pulmonary function tests, HRCT and serum levels of MMP-7 and OPN by ELISA. <bold>Results:</bold> Patients during acute COVID-19 showed increased levels of MMP-7 compared with healthy donors [(n=22), 6.7 ng/ml versus 3.9, p<0.0001]. After 1-year patients with higher levels of MMP-7 exhibited a lower DLCO (75±15 versus 85±20%, p=0.002) and higher COVID CT score (7.6±5.2 versus 4.4±3.9; p=0.02). Similar results were observed in the verification cohort. The cut-off predictive value for MMP-7 was 7.57ng/ml, AUC 0.70. OPN shows higher levels in acute phase but reached normal values at 1-year follow-up. <bold>Conclusion:</bold> MMP-7 is increased in patients with postCOVID-19 and is associated with the presence of residual lung abnormalities after long-term follow-up.