Figure 4.

a) Composite components of elastin and collagen contribute to the J-like tension-length (stress-strain) behavior of human iliac arteries. Reproduced with permission.^[168] Copyright 1999, Journal of Experimental Biology. b) Stiffness of IPN hydrogel covers a range between common soft hydrogels and stiff polymeric materials, agreeing well with physiological tissues surrounding vessels. c) ECs cultured in a branched IPH hydrogel channel form a tight monolayer and are impermeable to red-fluorescent Alexa Fluor 549-labeled bovine serum albumin after 15-min perfusion, compared to an acellular hydrogel channel with notable diffusion. White dash line indicates the boundary of microchannels. d) Schematic of the deposition of basement membrane components, such as laminin and collagen IV. e) Physiology-relevant permeability using HUVECs and other ECs can last up to 30 days in IPN microchannels. f) 3D confocal images of the endothelialized IPN microchannels perfused with sickle RBCs and Alexa 488-labeled bovine serum albumin. Sickle RBC occlusions, indicated by white arrows, lead to the local increase in permeability. b-f) Reproduced with permission.^[146] Copyright 2018, Springer Nature. g) Schematic of a vessel mimicking microchannel constituted with PA hydrogels and ECM coatings. h) Phase-contrast image of an ECs monolayer on fibronectin (FN)-coated PA hydrogels with 19.2-kPa stiffness after one hour of shear stress. i) ECM coating influences cellular responses to substrate stiffness. Permeability of FN coating is higher than collagen (CL) coating and depends on stiffness. g-i) Reproduced with permission.^[181] Copyright 2019, Royal Society of Chemistry.