PI: Todd McDevitt, Senior Investigator, Gladstone Institute of Cardiovascular Disease; Professor, Department of Bioengineering & Therapeutic Sciences, UCSF; Investigator, Roddenberry Center for Stem Cell Biology & Medicine at Gladstone

AR3T is supporting the development and testing of an ex vivo system capable of applying biologically-relevant mechanical load regimens to an array of microtissue constructs in order to examine the effects of mechanical forces on stem cells in 3D multicellular environments.

Tissue loading is a powerful means for modulating the tissue microenvironment and promoting healing. However, not all loading is the same, and both cellular and tissue responses are highly sensitive to characteristics such as stiffness, magnitude, frequency and duration of the stimulus. Indeed, stem cells interpret mechanical forces in a broad spectrum of ways that can affect their viability, phenotype, secretory properties and other functions.

Significant effort has focused on the engineering of microscale tissue constructs, often derived from or comprised entirely of different types of stem cells, for the purpose of modeling 3D cell assemblies ex vivo. Tissue constructs have been developed using microfabricated technologies or directly within microfabricated devices in order to create arrays of microscale tissues for high-throughput applications such as drug screening. Despite technical advances allowing the creation of complex, well-defined environmental conditions, most currently available technologies are not capable of applying mechanical loading regimens that can replicate biological forces experienced by stem cells, particularly in dynamic multicellular physical environments.

Current approaches to applying mechanical forces on the microscale to engineered tissues typically rely on suspending cells at relatively low density in a hydrogel material and/or physically attaching constructs to deformable substrates or post/pillars. Dynamic microfabricated systems have been developed, such as with pneumatically-actuated microposts, to apply a range of different forces to microtissue constructs in parallel. By varying the dimensions of the actuation diaphragms, it is possible to obtain a range of vertical displacements with a single pressure across an entire array of constructs. While such systems enable well-controlled applications of mechanical forces and measurements, most do not accurately mimic the multicellular physical composition of native tissues and, thus, the direct translational knowledge gained by the results of such experiments may be limited.

For these reasons, AR3T is supporting the development and validation of technology that will be used for the ex vivo elucidation of the stem cell response to extrinsic mechanical signals. The technology will allow for both static and cyclic mechanical loading of the microtissue constructs, using different durations and frequencies of time, in order to simulate conditions analogous to rehabilitation. Efforts will utilize several different types of stem cell microtissues and will examine different dynamic ranges of mechanical forces in order to define system parameters for a range of cell types.

The goal is to provide new techniques for enhancing the mechanistic understanding of the effects of physical forces on stem cell fate and function.

Visit the McDevitt Laboratory website to learn more about regenerative rehabilitation work being done at the Gladstone Institutes.