Fig 1.
Type XVIII collagen location and structure.
(A) Structure of the vascular basement membrane (BM). The capillary subendothelial layer is composed of a BM and an interstitial matrix (IM). The main components of vascular basement membranes include type IV collagen, laminin and nidogen. Minor components include type XV collagen and type XVIII collagen. The components of the BM self-assemble into sheet-like structures. The BM is tightly connected to the IM through interactions between collagen type I and VI and collagen type IV and XV. (B) Isoforms of Type XVIII collagen. Collagen type XVIII exists in three isoforms, which differ in their N-terminus. The COL18A1 gene encodes these variants by the use of two promoters and alternative splicing. The short isoform has a different signal peptide from the other two, and coded by promoter 1, while the others have the same signal peptide and both coded by promoter 2. All isoforms include a thrombospondin-like domain, heparin sulphate chains and a globular C-terminal containing the type XVIII collagen fragment, endostatin.
Table 1.
Technical performance of COL-18N ELISA.
Table 2.
Dilution recovery of COL-18N assay.
Table 3.
Spiking recovery.
Table 4.
1:1 spike recovery measured in two human serum samples.
Table 5.
Freeze-thaw stability.
Table 6.
Analyte stability measured at different time points and temperatures.
Fig 2.
COL-18N antibody specific reactivity against type XVIII collagen.
Monoclonal NB632-13H11/G5 antibody reaction towards standard peptide, truncated, elongated and de-selection peptides. The antibody has high reactivity towards standard peptide and no or minimal cross-reactivity with the other peptides.
Fig 3.
Biomarker COL-18N correlate with ABR.
Serum from 35 male HF patients aged 26 and over was measured with the COL-18N ELISA. Correlations between vascular endothelial type XVIII collagen concentration and ABR were analyzed using Spearman rank correlation coefficient and shown r = 0.45, p<0.006. Differences between ABR and COL-18N levels were considered statistically significant if p<0.05 and significant levels are displayed as: * = p<0.05; ** = p<0.01, and *** = p<0.001.