Familial high serum PICP: high even in skin interstitial fluid, suppressible by topical corticosteroid treatment

Abstract

Circulating C-terminal propeptide of type I procollagen (PICP), mostly originating from bone, is mainly cleared by mannose receptors (MRs) in liver endothelial cells (LECs). We hypothesized that skin macrophage MRs could also play a role in local (in situ) clearance of PICP originating from skin type I procollagen synthesis. We tested this hypothesis in a male subject with a genetic systemic clearance defect, apparently due to an abnormality in MR function in LECs (or in PICP structure). Since skin macrophages may express the same MRs as LECs do, the genetic defect could affect them as well; hence, if elevated PICP concentrations even in skin interstitial fluid (IF) were found in our subject, it would suggest a role for local MR-mediated PICP clearance in skin. Since glucocorticoids (GCs) upregulate MRs in vitro, we measured the effect of topical GC on suction blister fluid (SBF)-PICP of the test person as compared with normal subjects. SBF-PICP was elevated in the case, which was consistent with the hypothesis. Furthermore, the GC-induced decrease was accentuated. The results suggest that skin macrophage MRs can have a role in skin PICP clearance in situ.