Biology subjects

Doherty, E. L.

Publications and source records attributed to Doherty, E. L..

3 recordsLinked to original sources

bioRxiv2024

Dysfunctional mechanotransduction regulates the progression of PIK3CA-driven vascular malformations

Somatic activating mutations in PIK3CA are common drivers of vascular and lymphatic malformations. Despite common biophysical signatures of tissues susceptible to lesion formation, including compliant extracellular matrix and low rates of perfusion, lesions vary in clinical presentation from localized cystic dilatation to diffuse and infiltrative vascular dysplasia. The mechanisms driving the differences in disease severity and variability in clinical presentation and the role of the biophysical microenvironment in potentiating progression are poorly understood. Here, we investigate the role of hemodynamic forces and the biophysical microenvironment in the pathophysiology of vascular malformations, and we identify hemodynamic shear stress and defective endothelial cell mechanotransduction as key regulators of lesion progression. We found that constitutive PI3K activation impaired flow-mediated endothelial cell alignment and barrier function. We show that defective shear stress sensing in PIK3CAE542Kendothelial cells is associated with reduced myosin light chain phosphorylation, junctional instability, and defective recruitment of vinculin to cell-cell junctions. Using 3D microfluidic models of the vasculature, we demonstrate that PIK3CAE542Kmicrovessels apply reduced traction forces and are unaffected by flow interruption. We further found that draining transmural flow resulted in increased sprouting and invasion responses in PIK3CAE542K microvessels. Mechanistically, constitutive PI3K activation decreased cellular and nuclear elasticity resulting in defective cellular tensional homeostasis in endothelial cells which may underlie vascular dilation, tissue hyperplasia, and hypersprouting in PIK3CA-driven venous and lymphatic malformations. Together, these results suggest that defective nuclear mechanics, impaired cellular mechanotransduction, and maladaptive hemodynamic responses contribute to the development and progression of PIK3CA-driven vascular malformations.

bioengineering↗

bioRxiv2022

Patient-derived extracellular matrix demonstrates role of COL3A1 in blood vessel mechanics

Vascular Ehlers-Danlos Syndrome (vEDS) is a rare autosomal dominant disease caused by mutations in the COL3A1 gene, which renders patients susceptible to aneurysm and arterial dissection and rupture. To determine the role of COL3A1 variants in the biochemical and biophysical properties of human arterial ECM, we developed a method for synthesizing ECM directly from vEDS donor fibroblasts. We found that the protein content of the ECM generated from vEDS donor fibroblasts differed significantly from ECM from healthy donors, including upregulation of collagen subtypes and other proteins related to ECM structural integrity. We further found that ECM generated from a donor with a glycine substitution mutation was characterized by increased glycosaminoglycan content and unique viscoelastic mechanical properties, including increased time constant for stress relaxation, resulting in a decrease in migratory speed of human aortic endothelial cells when seeded on the ECM. Collectively, these results demonstrate that causal COL3A1 mutations lead to the synthesis of ECM that differs in composition, structure, and mechanical properties from healthy donors. These results further suggest that ECM mechanical properties could serve as a prognostic indicator for patients with vEDS, and the insights provided by the approach demonstrate the broader utility of cell-derived ECM in disease modeling.

bioengineering↗

bioRxiv2022

Microphysiological vascular malformation model reveals a role of dysregulated Rac1 and mTORC1/2 in lesion formation.

Somatic activating mutations of PIK3CA are associated with the development of vascular malformations (VMs). Here, we describe a microfluidic model of PIK3CA-driven VMs consisting of human umbilical vein endothelial cells (HUVECs) expressing PIK3CA activating mutations embedded in 3D hydrogels. We observed enlarged and irregular vessel phenotypes, consistent with clinical signatures and concomitant with PI3K-driven upregulation of Rac1/PAK, MEK/ERK, and mTORC1/2 signaling. We observed differential effects between Alpelisib, a PIK3CA inhibitor, and Rapamycin, an mTORC1 inhibitor, in mitigating matrix degradation and vascular network topology. While both drugs are effective in preventing vessel enlargement, Alpelisib suppressed mTORC2-dependent AKT1 phosphorylation and MEK/ERK signaling. Rapamycin failed to reduce MEK/ERK and mTORC2 activity and resulted in vascular hyperbranching, while inhibiting PAK, MEK1/2, and mTORC1/2 signaling mitigates abnormal growth and vascular dilation. Collectively, these findings establish an in vitro platform for modeling VMs and confirm a role of dysregulated Rac1/PAK and mTORC1/2 signaling in PIK3CA-driven VMs.

bioengineering↗