Self-rolled biomimetic artery on a chip

Introduction:: Pulmonary hypertension is a burgeoning public health challenge. Notably, the dysregulation of vasomotor tone in microvasculature with diameter 50-300 µm accounts for the increased peripheral resistance in cardiovascular diseases. Currently, available in vitro models do not adequately recapitulate the complex structure, microenvironment, and physiological functionality of the smallest human arteries – arterioles. Despite substantial contributions, animal models also have limitations due to fundamental differences from human vascular infrastructure. Here, we present an integrated microfabricated biomimetic human small muscular pulmonary arteries (hSMPAs) on a chip platform that recapitulates the pulmonary microvasculature's morphological, biochemical, and flow environment.

Materials and Methods::
We utilized cell engineering and microfluidics to design this platform. The tubular constructs were fabricated by photolithography strain-engineered self-folding. In 2D, fibronectin was patterned to provide biochemical cues to align the cells; various cell types and adhesive proteins were deposited in sequence, including human pulmonary arterial smooth muscle cells (HPASMC), intercellular adhesive protein laminin, and human pulmonary microvascular endothelial cells (HPMEC). The 2D films were then released by dissolving the sacrificial layer, thus forming 3D tubular constructs. These tubes could be inserted into microfluidic channels designed to accurately mimic the physiological structure of the pulmonary vasculature both in healthy and diseased states with regard to blood flow and shear stress within the channels. The latter state was designed and characterized by the presence of plexiform lesions. The production of nitric oxide from HPMECs was monitored in real-time by fluorescence microscopy, using DAF-2 DA as a nitric oxide indicator.




Results, Conclusions, and Discussions:: We demonstrated an integrated biomimetic platform that includes anatomically accurate human small muscular pulmonary arteries hSMPAs, including (a) Layering of ECM, HPMECs, HPASMCs in circular cross-section tubes, (b) alignment of HPASMCs with tunable diameter and microfabricated engineered precision. We observed that HPMEC actively produced nitric oxide at a rate three times higher when cultured in tubes compared to those cultured on flat surfaces.¹ We observed that the protein endothelial nitric oxide synthase was more phosphorylated in cells cultured in tubes compared to on flat surfaces. The data demonstrated that our biomimetic arterioles provide a beneficial environment for regulating vasomotor tone. We developed a microfluidic platform for these vessels.²At physiological flow rates of 0.1ml/min, larger pressure decrements and overall shear stresses were observed in channels mimicking vessel stenosis than in healthy non-stenotic channels. Specifically, in channels where plexiform lesions reduced channel size 60-77% in diameter, a shear stress increase of 9-29% was observed in the overall channel, while a 67-230% increase was observed in the region specifically with the plexiform lesion relative to non-stenotic channels of the same dimension. the platform with integrated biomimetic arterioles and recapitulated pulmonary microcirculation could advance current microphysiological systems for studying pulmonary hypertension and for drug screening.

Acknowledgements (Optional): : We acknowledge support from the National Science Foundation DMR-1709349 and Kley Dom Biomimetics. The authors disclose licensed patents and patent filings related to the technology. Corresponding authors: dgracias@jhu.edu; lromer@jhmi.edu

References (Optional): : 1. Jin, et al. Science Advances 6.13 (2020): eaaz2598. 2. K. Dani, X. Chen, D. H. Gracias*, L. H. Romer*, An Integrated Microcirculation Platform for Pulmonary Vascular Studies, in preparation (2023).