3D in vitro Model of Vascular Medial Thickening in Pulmonary Arterial Hypertension.

In pulmonary arterial hypertension (PAH), excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) causes vascular medial thickening. Medial thickening is a histopathological hallmark of pulmonary vascular remodeling, the central disease process driving PAH progression. Pulmonary vascular remodeling causes stenosis and/or obstruction of small pulmonary arteries. This leads to increased pulmonary vascular resistance, elevated pulmonary arterial pressure, and ultimately right heart failure. To improve the survival of PAH patients, which remains at approximately 60% at 3 years after diagnosis, the development of novel PAH-targeted drugs is desired. To this end, a detailed understanding of the mechanisms underlying excessive PASMC proliferation and the medial thickening that ensues is necessary. However, a lack of in vitro models that recapitulate medial thickening impedes our deeper understanding of the pathogenetic mechanisms involved. In the present study, we applied 3-dimensional (3D) cell culture technology to develop a novel in vitro model of the pulmonary artery medial layer using human PAH patient-derived PASMCs. The addition of platelet-derived growth factor (PDGF)-BB, a mitogen known to promote excessive PASMC proliferation in PAH, resulted in increased thickness of the 3D-PAH media tissues. Conversely, administration of the PDGF receptor inhibitor imatinib or other clinical PAH drugs inhibited this medial thickening-inducing effect of PDGF-BB. Altogether, by using 3D cell culture technology, we report the generation of an in vitro model of medial thickening in PAH, which had hitherto not been successfully modeled in vitro. This model is potentially useful for assessing the ability of candidate PAH drugs to suppress medial thickening.

Pancreatic stellate cells derived from human pancreatic cancer demonstrate aberrant SPARC-dependent ECM remodeling in 3D engineered fibrotic tissue of clinically relevant thickness.

Desmoplasia is a hallmark of pancreatic cancer and consists of fibrotic cells and secreted extracellular matrix (ECM) components. Various in vitro three-dimensional (3D) models of desmoplasia have been reported, but little is known about the relevant thickness of the engineered fibrotic tissue. We thus measured the thickness of fibrotic tissue in human pancreatic cancer, as defined by the distance from the blood vessel wall to tumor cells. We then generated a 3D fibrosis model with a thickness reaching the clinically observed range using pancreatic stellate cells (PSCs), the main cellular constituent of pancreatic cancer desmoplasia. Using this model, we found that Collagen fiber deposition was increased and Fibronectin fibril orientation drastically remodeled by PSCs, but not normal fibroblasts, in a manner dependent on Transforming Growth Factor (TGF)-ß/Rho-Associated Kinase (ROCK) signaling and Matrix Metalloproteinase (MMP) activity. Finally, by targeting Secreted Protein, Acidic and Rich in Cysteine (SPARC) by siRNA, we found that SPARC expression in PSCs was necessary for ECM remodeling. Taken together, we developed a 3D fibrosis model of pancreatic cancer with a clinically relevant thickness and observed aberrant SPARC-dependent ECM remodeling in cancer-derived PSCs.