Corrigendum to "Force sensors for measuring microenvironmental forces during mesenchymal condensation" [Biomaterials 270 (2021) 120684].

Mechanical forces are an essential element to early tissue formation. However, few techniques exist that can quantify the mechanical microenvironment present within cell-dense neotissues and organoid structures. Here is a versatile approach to measure microscale, cellular forces during mesenchymal condensation using specially tailored, hyper-compliant microparticles (HCMPs). Through monitoring of HCMP deformation over both space and time, measurements of the mechanical forces that cells exert, and have exerted on them, during tissue formation are acquired. The current study uses this technology to track changes in the mechanical microenvironment as mesenchymal stem cells self-assemble into spheroids and condense into cohesive units. An array analysis approach, using a high-content imaging system, shows that cells exert a wide range of tensile and compressive forces during the first few hours of self-assembly, followed by a period of relative equilibrium. Cellular interactions with HCMPs are further examined by applying collagen coating, which allows for increased tensile forces to be exerted compared to non-coated HCMPs. Importantly, the hyper-compliant nature of our force sensors allows for increased precision over less compliant versions of the same particle. This sensitivity resolves small changes in the microenvironment even at the earliest stages of development and morphogenesis. The overall experimental platform provides a versatile means for measuring direct and indirect spatiotemporal forces in cell-dense biological systems.