Measuring cellular forces using bis-aliphatic hydrazone crosslinked stress-relaxing hydrogels.

D D Mckinnon,K A Kyburz,K A Kyburz,K A Kyburz,K A Kyburz,T E Brown,T E Brown,T E Brown,T E Brown,E Kiyotake,E Kiyotake,E Kiyotake,K S Anseth,K S Anseth,K S Anseth,K S Anseth,K S Anseth,J N Cha,J N Cha,J N Cha,J N Cha,D W Domaille,D W Domaille,D W Domaille,D W Domaille

doi:10.1039/c4sm01365d

Abstract

Studies focused on understanding the role of matrix biophysical signals on cells, especially those when cells are encapsulated in hydrogels that are locally remodelled, are often complicated by appropriate methods to measure differences between the bulk and local material properties. From this perspective, stress-relaxing materials that allow long-term culture of embedded cells provide an opportunity to elucidate aspects of this biophysical signalling. In particular, rheological characterization of the stress relaxation properties allows one to link a bulk material measurement to local aspects of cellular functions by quantifying the corresponding cellular forces that must be applied locally. Here, embryonic stem cell-derived motor neurons were encapsulated in a well-characterized covalently adaptable bis-aliphatic hydrazone crosslinked PEG hydrogel, and neurite outgrowth was observed over time. Using fundamental physical relationships describing classical mechanics and viscoelastic materials, we calculated the forces and energies involved in neurite extension, the results of which provide insight to the role of biophysical cues on this process.

Highlights

For the past decade, there has been a growing literature devoted to elucidating the effects of matrix modulus on the function of both plated and encapsulated cells.[1,2,3,4,5,6,7,8] The Discher group pioneered some of the early efforts and demonstrated that human mesenchymal stem cells preferentially commit to a lineage that is heavily dependent on the mechanics of the surface on which they are seeded.[2]
Since the gel mechanical properties can be readily manipulated in a systematic way, these materials should prove useful in efforts to better characterize the complex exchange of biophysical cues between cells and their microenvironment
We have shown that the combination of well-de ned viscoelastic materials, fundamental physics, and real-time microscopy allows for the measurement of basic biophysical processes that are extremely difficult to measure by other means

Summary

Introduction

There has been a growing literature devoted to elucidating the effects of matrix modulus on the function of both plated and encapsulated cells.[1,2,3,4,5,6,7,8] The Discher group pioneered some of the early efforts and demonstrated that human mesenchymal stem cells (hMSCs) preferentially commit to a lineage that is heavily dependent on the mechanics of the surface on which they are seeded.[2]. S. Anseth et al Measuring cellular forces using bis-aliphatic hydrazone crosslinked stress-relaxing hydrogels

Results

Conclusion