Bioengineers from the University of California, San Diego (UCSD) report the creation of an artificial environment for stem cells that simultaneously provides the chemical, mechanical, and electrical cues necessary for stem cell growth and differentiation. They were able to use this microenvironment to grow bone-marrow-derived mesenchymal stem cells and guide them to differentiate into cartilage cells.
Their work is detailed in a paper published online in Advanced Functional Materials on November 13 titled “Dynamic Electromechanical Hydrogel Matrices for Stem Cell Culture.”
While researchers have already created artificial environments for stem cells that provide chemical cues combined with either mechanical or electrical cues, the UC San Diego bioengineers say this is the first material reported in scientific literature that provides all three cues at one time, in a 3-D supportive environment.
The UCSD team started by embedding the stem cells in a gelatin-like hydrogel bathed in an electrolyte solution compatible for cell growth. When an electric potential passes through the hydrogel, the gel bends and exerts mechanical strain on the cells that is designed to mimic the mechanical cues stem cells experience in natural microenvironments.
“Our hydrogel provides the chemical cues, and when you expose them to an electric field, the hydrogel surrounding the stem cells bends, which provides mechanical strain to the cells,” explains Shyni Varghese, Ph.D., the bioengineering professor who advised the student researchers working in her Biomimetic Polymers and Stem Cell Engineering laboratory at the UC San Diego Jacobs School of Engineering.
A unique aspect of the matrices developed is that they undergo reversible, anisotropic bending dynamics in an electric field. The direction and magnitude of this bending can be tuned through the hydrogel crosslink density while maintaining the same electric potential gradient, allowing control over the mechanical strain imparted to the cells in a 3-D environment.
The conceptual design of these hydrogels was motivated through theoretical modeling of the osmotic pressure changes occurring at the gel-solution interfaces in an electric field. These electromechanical matrices support survival, proliferation, and differentiation of stem cells. The scientists from UCSD say that these new 3-D in vitro synthetic matrices, which mimic multiple aspects of the native cellular environment, take us one step closer to in vivo systems.