A Comparative Study of Collagen Matrix Density Effect on Endothelial Sprout Formation Using Experimental and Computational Approaches

Abstract

A thorough understanding of determining factors in angiogenesis is a necessary step to control the development of new blood vessels. Extracellular matrix density is known to have a significant influence on cellular behaviors and consequently can regulate vessel formation. The utilization of experimental platforms in combination with numerical models can be a powerful method to explore the mechanisms of new capillary sprout formation. In this study, using an integrative method, the interplay between the matrix density and angiogenesis was investigated. Owing the fact that the extracellular matrix density is a global parameter that can affect other parameters such as pore size, stiffness, cell-matrix adhesion and cross-linking, deeper understanding of the most important biomechanical or biochemical properties of the ECM causing changes in sprout morphogenesis is crucial. Here, we implemented both computational and experimental methods to analyze the mechanisms responsible for the influence of ECM density on the sprout formation that is difficult to be investigated comprehensively using each of these single methods. For this purpose, we first utilized an innovative approach to quantify the correspondence of the simulated collagen fibril density to the collagen density in the experimental part. Comparing the results of the experimental study and computational model led to some considerable achievements. First, we verified the results of the computational model using the experimental results. Then, we reported parameters such as the ratio of proliferating cells to migrating cells that was difficult to obtain from experimental study. Finally, this integrative system led to gain an understanding of the possible mechanisms responsible for the effect of ECM density on angiogenesis. The results showed that stable and long sprouts were observed at an intermediate collagen matrix density of 1.2 and 1.9 mg/ml due to a balance between the number of migrating and proliferating cells. As a result of weaker connections between the cells and matrix, a lower collagen matrix density (0.7 mg/ml) led to unstable and broken sprouts. However, higher matrix density (2.7 mg/ml) suppressed sprout formation due to the high level of matrix entanglement, which inhibited cell migration. This study also showed that extracellular matrix density can influence sprout branching. Our experimental results support this finding.

Modeling, signaling and cytoskeleton dynamics: integrated modeling‐experimental frameworks in cell migration

“…With this corresponding matrix density index obtained, the angiogenesis process, that is the migration of endothelial cells, is simulated mimicking different collagen density effect. Shamloo et al confirmed their previous model predictions on endothelial sprout formation morphology under different ECM matrix. Recent studies also consider the effect of MMP and the nucleus compartments in cell migration using cellular Potts models.…”

“…The cellular Potts model has addressed multiple cell migration predictions that can be validated by experiments. One of the successes is in predicting endothelial cell migration in angiogenesis . Shamloo et al first used an in silico collagen fibrils model to estimate the corresponding matrix density index used in their model through matching collagen area in microscopic and in silico images under different densities.…”

“…One of the successes is in predicting endothelial cell migration in angiogenesis . Shamloo et al first used an in silico collagen fibrils model to estimate the corresponding matrix density index used in their model through matching collagen area in microscopic and in silico images under different densities. We also have used an in silico collagen fibers model to mimic microscopic collagen images in vitro .…”

Optimal bovine collagen concentration to achieve tracheal epithelial coverage of collagen sponges

“…Although it has been reported that collagen sponge scaffolds prepared from porcine and bovine collagen have different structures, only porcine collagen has been investigated for its regenerative effect on the tracheal epithelium. Because the structure of collagen sponge scaffolds is known to affect cell behavior, collagen sponges with various structures have been prepared by modifying crosslinking methods, collagen concentration, and temperature for freezing the collagen solution . However, the concentrations of bovine collagen that are optimal for tracheal epithelial regeneration have never been reported.…”

“…Because the structure of collagen sponge scaffolds is known to affect cell behavior, collagen sponges with various structures have been prepared by modifying crosslinking methods, collagen concentration, and temperature for freezing the collagen solution. 15 However, the concentrations of bovine collagen that are optimal for tracheal epithelial regeneration have never been reported.…”