title: Age-related changes in rat dermal extracellular matrix composition affect the distribution of plasma proteins as a function of size and charge.
abstract: Collagen and glycosaminoglycans (GAGs) constituting the ECM may limit the space available and thus exclude macromolecules from a fraction of the interstitial fluid (IF) phase. This exclusion phenomenon is of importance for transcapillary fluid and solute exchange. The purpose of the study was to examine the range of interstitial exclusion in rat skin by using probes within a span of molecular weights and electrical charge and also to test if a change in interstitial composition, occurring as a consequence of aging, affected exclusion. To this end, we used a novel approach, involving the exact determination of albumin concentration and mass in IF and tissue eluate by HPLC and thereafter, expressing the corresponding numbers relative to albumin for a set of probe proteins assessed by quantitative proteomics. Albumin was excluded from 55±4% (n=8) of the extracellular fluid phase. There was a highly significant, positive correlation between probe Stokes-Einstein (SE) radius and fractional excluded volume (VEF), described by VEF=0.078·SE radius+0.269 (P<0.001), and oppositely, a negative correlation between probe isoelectric point (pI) and exclusion for proteins with comparable size, VEF=-0.036·pI+0.719 (P=0.04). Aging resulted in a significant reduction in skin hydration and sulfated GAGs, a moderate increase in hyaluronan, and a corresponding, reduced VEF for albumin and the other macromolecular probes. Our findings suggest that the changes in the ECM in aged skin may result in delayed adjustments of fluid perturbations and reduced ability for salt storage.
authors.affiliation: Department of Biomedicine, University of Bergen, Bergen, Norway.
authors.forename: Solfrid J
authors.initials: SJ
authors.lastname: Sagstad
authors.affiliation: Department of Biomedicine, University of Bergen, Bergen, Norway.
authors.forename: Eystein
authors.initials: E
authors.lastname: Oveland
authors.affiliation: Department of Biomedicine, University of Bergen, Bergen, Norway.
authors.forename: Tine V
authors.initials: TV
authors.lastname: Karlsen
authors.affiliation: Department of Biomedicine, University of Bergen, Bergen, Norway.
authors.forename: Hanne
authors.initials: H
authors.lastname: Haslene-Hox
authors.affiliation: Department of Biomedicine, University of Bergen, Bergen, Norway.
authors.forename: Olav
authors.initials: O
authors.lastname: Tenstad
authors.affiliation: Department of Biomedicine, University of Bergen, Bergen, Norway helge.wiig@biomed.uib.no.
authors.forename: Helge
authors.identifier: http://orcid.org/0000-0002-7740-8210
authors.initials: H
authors.lastname: Wiig
mesh_terms: D000367:Age Factors; D000375:Aging / Q000097:blood / Q000378:metabolism*; D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000378:metabolism; D004553:Electric Conductivity; D045604:Extracellular Fluid / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D005260:Female; D006025:Glycosaminoglycans / Q000378:metabolism; D006820:Hyaluronic Acid / Q000378:metabolism; D008954:Models, Biological; D008970:Molecular Weight; D017207:Rats, Sprague-Dawley; D012709:Serum Albumin / Q000378:metabolism; D012867:Skin / Q000378:metabolism*; D014867:Water / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D006025:Glycosaminoglycans; D012709:Serum Albumin; D014867:Water; D006820:Hyaluronic Acid; D003094:Collagen
keywords: extracellular matrix; interstitial fluid; plasma protein exclusion