Abstract
Diabetes, a disease increasingly affecting the U.S. population, puts patients at risk for chronic wound development. Chronic wounds respond poorly to available treatments and burden our healthcare system, thus demanding an improvement of existing therapy. Mesenchymal stem cells (MSCs) are a promising therapeutic for chronic wounds as they can differentiate into cells required in the skin, secrete antimicrobial peptides, and modulate the inflammatory effects of immune cells. In current treatment models, MSCs often fail to engraft into a wound site. The Maverakis lab aims to create an improved MSC delivery system to better facilitate MSC engraftment and appropriately direct cellular response within a chronic wound. The improved MSC delivery system utilizes a hydrogel matrix embedded with synthetic peptides that specifically interact with integrins proteins. Integrins are renowned mediators of cellular attachment, and targeting these proteins may allow MSCs to better embed into the hydrogel and engraft into a wound. Furthermore, targeting a specific integrin will allow for tight control of downstream cellular response. LLP2A, a synthetic peptide and a candidate molecule for use in hydrogels, specifically binds the α4β1 integrin on the surface of MSCs. The downstream effects of LLP2A require thorough characterization to ensure the MSC response to LLP2A improves wound healing. MSC exposure to LLP2A causes a three-fold increase in expression of collagen mRNA, an extracellular matrix protein found in skin that supports wound healing. LLP2A also induces cells to increase expression of the α4 integrin, which may improve MSC attachment to the ECM if LLP2A is used in wound healing. As MSCs are multipotent cells with various differentiation potentials, it is critical to ensure LLP2A does not promote differentiation into unwanted cell types within a skin wound. LLP2A exposure induces expression of osteogenesis and chondrogenesis markers in MSCs, which could prove disadvantageous to wound healing in skin tissue. Preliminary in vivo hydrogel studies showed hydrogel composition could allow for a tunable rate of biodegradation; hydrogels can degrade over the course of three weeks, or hydrogels can be prevented from degrading for at least two months. More in vitro and in vivo testing is necessary before this hydrogel mediated MSC delivery model can be used for therapy. Preliminary analysis of LLP2A’s effect on MSCs suggests this peptide would be most useful to wound healing in a hydrogel that degrades quickly, thereby preventing MSC differentiation into unwanted cell types. On the contrary, if this peptide is used in hydrogels aimed at MSC-mediated treatment of diseases of joints and bone, a non-degradable hydrogel would allow MSCs to differentiate and, in this case, directly regenerate damaged tissues. In vitro examination of LLP2A’s effect on MSCs doesn’t account for the complex signaling environment that cells would encounter within an organism during therapy. Future in vivo testing will further elucidate how many signals that converge on the MSCs delivered to a wound effect differentiation and healing outcomes.