INTELLECTUAL MERIT: Small interfering (siRNA) is a powerful and specific gene silencing mechanism that can initiate signaling cascades governing stem cell differentiation. Thus, siRNA may provide potent cues to direct stem-cell differentiation for regenerative medicine applications. However, development of technology to provide patterned, localized, and efficacious delivery of siRNA is crucial for realizing this potential. The objective of this work is to incorporate and control the patterning of polymer nanoparticles (NPs) to deliver siRNA within a hydrogel to affect encapsulated mesenchymal stem cell (MSC) differentiation, where MSCs are multipotent precursor cells capable of differentiating into cells of the musculoskeletal lineage. The PI aims to develop hydrogel scaffolds that can be patterned with powerful siRNA differentiation cues capable of directing osteogenic and chondrogenic differentiation of MSCs for osteochondral tissue engineering applications. Four technical objectives have been established to achieve this goal: (1) Assemble and characterize siRNA/polymer nanoparticles (NPs) to direct MSC osteogenic and chondrogenic differentiation. (2) Exploit controlled release chemistries to sustain the release of siRNA from or within hydrogels. (3) Develop spatial photopatterning techniques for siRNA/polymer NP within hydrogel microenvironments. (4) Exploit spatiotemporally regulated siRNA/polymer NP availability to develop osteogenic, chondrogenic, and osteochondral tissue in vitro. The results of these objectives will establish MSC differentiation induced by siRNA within hydrogel microenvironments. Moreover, it will demonstrate that delivery of spatiotemporally controlled differentiation cues can be exploited to develop complex tissue structures. These developments will advance and expand the utility of siRNA for numerous therapeutic applications within regenerative medicine and beyond, where spatial and temporal depot delivery is required.
BROADER IMPACTS: Over 50% of orthopaedic injuries involve damage to osteochondral tissues within articular joints. Due to the paucity of regenerative strategies, these injuries commonly progress to irreversible degenerative osteoarthritis. This work will develop the means to exploit spatially and temporally controlled siRNA therapeutics for osteochondral tissue regeneration. However, the approach can readily be tailored for the engineering of any multicomponent tissue. Beyond the anticipated scientific results, the PI has planned a variety of activities to educate non-engineers as well as to recruit and retain women and underrepresented minorities in engineering. Specifically, the PI will be proactive in working with UR programs aimed at increasing diversity and exposing high school students to possible career opportunities in engineering. These programs include: hosting and mentoring Xerox, Kearns, and SURF students each summer, developing and teaching hands-on laboratory experiments for UR's Summer Scholars Program, working with UR's Women In Engineering Group to host events in our laboratory and speak to visiting student groups, hosting shadowing high school students, and speaking at numerous public engagements to educate the general public about engineering's impact in society (e.g., WXXI Healthy Friday radio program, Annual Benoit Laboratory Alex's Lemonade Stand).
