Understanding vascular Ehlers-Danlos syndrome

Abstract

The discovery of experimentally derived induced pluripotent stem cells (iPSCs) has fostered prospects of patient-specific cell replacement therapies, novel toxicology and drug screening assays, and informative cell models for understanding disease pathogenesis. The latter is particularly valuable to the study of human syndromes caused by gene defects where animal models are lacking or inadequately mimic the human condition. One such vascular variant is Ehlers-Danlos Syndrome (EDS), a heritable disease of connective tissues involving collagen types COL5A, COL3A, tenascin-X, and to a lesser extent COL1A, lysyl hydroxlase and ADAM metallopeptidase. Among the six major types, the vascular form of EDS (vEDS) is the most severe. It results principally from mutations in the collagen III, alpha 1 (COL3A1) gene and is thought to cause aberrant collagen fibrillogenesis. These mutations contribute to catastrophic ruptures of large arteries, strokes, pregnancy-related mortalities, and pre-mature death among young adults. The presentation of this disease is heterogeneous, even among patients with the same gene mutation, and it remains unclear why some individuals exhibit severe phenotypes while others do not. In mouse models, COL3A1 deficiency mostly produces a weak disease variant without vascular ruptures, while a spontaneous COL3A1 mutation that leads to vascular defects lacks important disease features found in humans. Currently, there are no adequate therapeutic treatments. To determine how COL3A1 mutations lead to vEDS, we propose to examine and exploit a human cell model of this disease using iPSC lines derived from fibroblasts obtained from two probands. We will correct the Col3A1 gene mutations with TALENs to ensure against phenotypic iPSC variability and determine the principal source of COL3A1 secretion from iPSC-derived vascular progeny. We will examine basic growth characteristics and functional properties of these cells as well as determine the effects of doxycycline on collagen and matrix metalloproteinase synthesis (RNA and protein), stability or activity. By establishing high quality, experimentally confirmed iPSC vascular progeny, this study should lead directly to the development of reliable human tissue models of vEDS suitable for examining the effects of COL3A1 mutations on vasculogenesis and vascular integrity as well as establish a reliable system to test for possible therapeutic (pharmacological or regenerative) interventions.