Seibel, A. J. | Search bioRxiv

bioRxiv2022

ECM-derived biophysical cues mediate interstitial flow-induced sprouting angiogenesis

Sprouting angiogenesis is orchestrated by an intricate balance of biochemical and mechanical cues in the local microenvironment. Interstitial flow has been established as a potent regulator of angiogenesis. Similarly, extracellular matrix (ECM) physical properties, such as stiffness and microarchitecture, have also emerged as important mediators of angiogenesis. Yet, the interplay between interstitial flow and ECM physical properties in the initiation and control of angiogenesis is poorly understood. Using a 3-D microfluidic tissue analogue of angiogenic sprouting with defined interstitial flow, we found that the addition of hyaluronan (HA) to collagen-based matrices significantly enhances sprouting induced by interstitial flow compared to responses in collagen-only hydrogels. We confirmed that both the stiffness and matrix pore size of collagen-only hydrogels were increased by the addition of HA. Interestingly, interstitial flow-potentiated sprouting responses in collagen/HA matrices were not affected when functionally blocking the HA receptor CD44. In contrast, enzymatic depletion of HA in collagen/HA matrices with hyaluronidase (HAdase) resulted in decreased stiffness, pore size, and interstitial flow-mediated sprouting to the levels observed in collagen-only matrices. Taken together, these results suggest that HA enhances interstitial flow-mediated angiogenic sprouting through its alterations to collagen ECM stiffness and pore size.

bioengineering↗

bioRxiv2019

Integrated biophysical characterization of fibrillar collagen-based hydrogels

This paper describes an experimental characterization scheme of the biophysical properties of reconstituted hydrogel matrices based on indentation testing, quantification of transport via microfluidics, and confocal reflectance microscopy analysis. While methods for characterizing hydrogels exist and are widely used, they often do not measure diffusive and convective transport concurrently, determine the relationship between microstructure and transport efficiency, and decouple matrix mechanics and transport properties. Our integrated approach enabled independent and quantitative measurements of the structural, mechanical, and transport properties of hydrogels in a single study. We used fibrillar type I collagen as the base matrix and investigated the effects of two different matrix modifications: 1) cross-linking with human recombinant tissue transglutaminase II (hrTGII) and 2) supplementation with the non-fibrillar matrix constituent hyaluronic acid (HA). hrTGII modified matrix structure and transport but not mechanical parameters. Furthermore, changes in matrix structure due to hrTGII were seen to be dependent on the concentration of collagen. In contrast, supplementation of HA at different collagen concentrations altered matrix microstructure and mechanical indentation behavior but not transport parameters. These experimental observations reveal the important relationship between ECM composition and biophysical properties. The integrated techniques are versatile, robust, and accessible; and as matrix-cell interactions are instrumental for many biological processes, the methods and findings described here should be broadly applicable for characterizing hydrogel materials used for 3-D tissue engineered culture models.

bioengineering↗