Control of fibroblast shape in sequentially formed 3D hybrid hydrogels regulates cellular responses to microenvironmental cues

A sequentially formed hybrid hydrogel system consisting of collagen and alginate was designed to control cell shape in 3D. The cell with different spreading state had significantly different responses to mechanical (i.e., matrix stiffness) and biochemical (i.e., transforming growth factor-beta 1 (TGF-beta 1)) cues. Biomaterials: addding an extra dimension to cell shape Researchers in China have developed a material-based approach that can control the shape of cells in three dimensions. The shape of a cell, which is known to be dependent on its microenvironment, heavily influences its growth, movement and differentiation. This dependency has previously been studied mainly using two-dimensional cultures, but it is believed that cell behavior could be significantly different in more realistic three-dimensional cultures. To better understand the influence of a cell's surroundings on its shape and function, Feng Xu, Guoyou Huang and their colleagues from Xi'an Jiaotong University created an artificial cellular microenvironment by developing an approach based on sequentially formed hybrid hydrogels. They demonstrated the ability of this microenvironment to control the shape of cardiac fibroblasts in three dimensions and showed how this affected the cells' responses to mechanical and biochemical stimuli. Cell shape plays important roles in regulating cell behavior; however, independently controlling cell shape in three dimensions is a challenging undertaking, and how cell shape affects cellular responses to mechanical and biochemical cues in three dimensions remains unclear. Here, we present a hydrogel-based platform to control cell shape in three dimensions by using sequentially formed hybrid hydrogels consisting of collagen and alginate. By adjusting the cross-linking time of the alginate, we fixed the shape of NIH 3T3 fibroblasts at different spreading states. Then, we explored the influence of cell shape on the cell responses to microenvironmental cues by using cardiac fibroblasts (CFs) as model cells. We found that the spreading state of the CFs influences their responses to both mechanical (i.e., matrix stiffness) and biochemical (i.e., transforming growth factor-beta 1 (TGF-beta 1)) cues in three dimensions. Additional experiments revealed that integrin beta 1 in focal adhesions and Smad2/3 are involved in mediating the cell shape-dependent responses of CFs to matrix stiffness and TGF-beta 1 cues, respectively. This work represents the first step in understanding how cell shape influences cell responses to mechanical and biochemical cues in three dimensions and can be instructive for developing novel approaches to target cell shape regulation for treating fibrosis and other diseases.