Picrosirius red staining and polarization microscopy can reveal changes in the properties of collagen fibrils. Indeed, a reduced birefringence was observed at day 7 in wounds of Col6a1 null mice. This reduction was not apparent anymore at day 10 of wound healing. Confirming this result, analysis of the collagen I fibril architecture by electron microscopy revealed changes in the extracellular matrix between the fibrils in wounds of the Col6a1 null mice at day 7. At central areas of the wound, the amount of fine microfibrillar structures interwoven between the collagen I fibrils was reduced and the collagen I fibrils were more densely packed. In contrast, the differences in fibril diameter distribution were marginal. In addition, in more peripheral areas of the wound where the collagen I fibrils had larger diameters, an irregular fusion of fibrils was often seen. No obvious changes in collagen fibril architecture were GDC-0879 detected in unwounded skin from mice of the two genotypes. However, to investigate if the lack of collagen VI alters the tensile strength of unwounded skin, we performed mechanical tests on skin of wild type and collagen VI null mice. When the skin was stretched, the ultimate load and stress were significantly lower in collagen VI null mice in indicating that their skin is less strong. Collagen VI is thought to contribute to tissue remodelling and in addition to the obvious muscular pathologies, mutations in human collagen VI genes also often lead to keloid formation and other skin related phenotypes. Col6a1 null mice serve as a well-established model for the muscle phenotypes, but have not been studied with regard to skin changes. In a first step we characterized the expression of collagen VI chains in mouse skin. We then performed wound healing experiments in skin of wild type and Col6a1 null mice to assess whether this mouse model is also useful to assess the relevance of the classical collagen VI for skin development and for tissue reconstitution following injury. Since absence of the collagen VI a1 chain results in the failure to form the classical a1a2a3 Temozolomide side effects trimer of collagen VI, we moreover sought to assess compensatory expression of the recently identified a4, a5 and a6 chains of collagen VI.