Engineering microscale hydrogel deposition to direct single stem cell differentiation

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PROJECT SUMMARY Adult stem cells hold broad-ranging clinical potential to regenerate injured tissues. For instance, mesenchymal stem cells (MSCs) have been investigated in over 950 clinical trials for use in many disease indications. Despite their significant clinical relevance, however, there is currently lack of the mechanistic understanding to precisely control MSC functions for reproducible therapeutic outcomes. Engineered hydrogels have been used to reveal the ability of MSCs to sense and respond to matrix biophysical cues, which subsequently impact the differentiation potential of MSCs. However, leveraging these insights for therapeutic purposes has been challenging, since current approaches to interface a cell population with a hydrogel by uncontrolled mixing overlook the significance of heterogeneity in the local amount of the gel presented to individual cells, leading to variable and unclear cell-material interactions at the single cell level. We describe herein a highly efficient approach to control microscale hydrogel deposition around single cells in a 3D space independently of gel composition and elasticity. Using this approach, our preliminary data show that MSCs rapidly expand in volume when they adhere to an integrin ligand in thinner gels. We show that encapsulating single MSCs in a thin gel coating is sufficient to enhance the osteogenic potential of MSCs even when gel elasticity is low. We will build upon these results to test the hypothesis that controlling local gel deposition around single MSCs impacts membrane tension and lineage specification by regulating cell volume expansion. In Aim 1, we will determine the effect of varying local gel deposition on regulatory volume decrease by modulating mechanosensitive ion channels and its impact on membrane tension of MSCs. In Aim 2, we will determine how varied local gel deposition impacts single MSC fate and MSC-based bone regeneration. We predict that there exists a transcriptional program that is selectively activated when the gel deposition becomes thinner, thereby impacting lineage specification of MSCs independently of gel elasticity. The project is highly multidisciplinary in that it will employ a combination of expertise in biomaterials, biophysical, genetic, and in vivo approaches to address the specific aims. The results will help to define local gel deposition as an important determinant of stem cell growth, thereby impacting stem cell mechanics and fate. Given the clinical relevance of these cells, our results will inform formulation design of MSC-based therapeutics for improved regenerative outcomes.