Skin Disease Investigation
Vascular Ehlers-Danlos Syndrome & Type III Collagen
Vascular Ehlers-Danlos syndrome (EDS) is an inherited connective tissue disorder known as the most severe form of EDS. Vascular EDS is the result of a heterozygous mutation, typically a point mutation of glycine, in the type III collagen produced by the COL3A1 gene (Mizuno). Mutations in the gene lead to defects in the collagen it produces or leads to reduced amounts of collagen created. The disease is genetically inherited as an autosomal dominant trait. Vascular, or type IV, EDS is phenotypically characterized with patient symptoms including translucent and fragile skin that is hyper-extensible and marked with atrophic cutaneous scars. Individuals with vascular EDS are likely to have complications involving arterial, digestive and urinary facets. They have bowels and arteries that are prone to rupture spontaneously and bruise easily. Further, these individuals have severely fragile internal organs and arteries and often suffer from receding gums and varicose veins. The major cause of death within vascular EDS is arterial ruptures. The median age of death of individuals with this disease is fifty years. (GARD)
Collagens are a protein family that serve as strength and support systems for many bodily tissues. They are the most abundant protein in mammals and account for nearly 30% of their protein content. Collagen molecules have a rigid, rod-like structure that resists stretching. Type III collagen is a critical fibrillar collagen comprised of three ?1(III) chains supercoiled around each other, forming a right-handed triple helix with about three amino acids per turn (Xin). The helix is stabilized by the presence of glycine as every third residue. Mutations of type III collagen include sing-base substitutions of glycine to another amino acid and mRNA splicing defects (Kuiv). Type III collagen is discharged by fibroblasts and other types of mesenchymal cells. The protein provides structure and strength to connective tissues throughout the body. Type III collagen is found in tissues exhibiting elastic properties such as skin, lungs, intestinal walls, and the walls of the blood vessels and is the second most abundant collagen of soft tissues to type I collagen. Type III collagen is vital for the development of the skin and the cardiovascular system. The protein is crucial for maintaining the healthy and stable physiological functions of organs in adults.
Type III collagen is a major constituent of the extracellular matrix. The protein, along with type I collagen, provides tissues with tensile strength and influence cell attachment and migration. Within the dermis layer, 90% of found collagen is type I and 10% is type III collagen. When compared to type I collagen fibers, those of type III have a smaller diameter and are better able to withstand deformation. Strands of type III collagen compose reticular fibers that build a highly ordered cellular network and provide a supporting network. Reticular fibers form reticular connective tissue and provide a stroma to support the liver, lymphoid organs, capillary endothelia, and muscle fibers. These fibers are mainly found in the basement membrane. The formed connective tissue act as capsules for organs and joints.