Conclusions
Two assays measuring C4M12a1 and C4M12a3 enabled quantification of MMP mediated degradation of type IV collagen in serum. C4M12a1 was elevated in a pre-clinical model of liver fibrosis, and C4M12a3 was elevated in IPF and COPD patients. This suggests the use of these assays to investigate pathological remodeling of the basement membrane in different organs. However, validations in larger clinical settings are needed.
Methods
Fragments of type IV collagen cleaved in vitro by MMP-12 were identified by mass spectrometry, and two were chosen for ELISA development due to their unique sequences. The assays were evaluated using samples from a carbon tetrachloride (CCl&sub4;) rat model of liver fibrosis and from patients with idiopathic pulmonary fibrosis (IPF) or chronic obstructive pulmonary disease (COPD).
Results
Two technically robust ELISAs were produced using neo-epitope specific monoclonal antibodies. Mean serum C4M12a1 levels were significantly elevated in CCl&sub4;-treated rats compared with controls in weeks 12, 16, and 20, with a maximum increase of 102% at week 16 (p < 0.0001). Further, C4M12a1 levels correlated with the total collagen content of the liver in CCl&sub4;-treated rats (r = 0.43, p = 0.003). Mean serum C4M12a3 levels were significantly elevated in patients with mild, moderate, and severe IPF, and COPD relative to healthy controls, with a maximum increase of 321% in COPD (p < 0.0001). Conclusions: Two assays measuring C4M12a1 and C4M12a3 enabled quantification of MMP mediated degradation of type IV collagen in serum. C4M12a1 was elevated in a pre-clinical model of liver fibrosis, and C4M12a3 was elevated in IPF and COPD patients. This suggests the use of these assays to investigate pathological remodeling of the basement membrane in different organs. However, validations in larger clinical settings are needed.