Cartilage regeneration by stem cells provides a tremendous hope for the millions of people who suffer from cartilage injuries, e.g., osteoarthritis. The overall objective of this project is to understand how pore size and matrix elasticity in a 3D environment regulate stem cell-based cartilage regeneration. The building blocks for the novel 3D scaffold are ribbon-like and microsized hydrogels that can be cross linked to encapsulate human mesenchymal stem cells and provide an environment with independently tunable pore size, matrix elasticity and chemical properties. The proposed studies will provide valuable information about the environment needed to achieve complete stem cell based cartilage repair. Educational and outreach impact will be achieved through enhanced research experiences for involved students, new graduate level courses, and activities involving high school teachers and underrepresented K-12 students. This award is co-funded by the Biomaterials program in the Division of Materials Research through the BioMaPs program.
Articular cartilage injuries as a result of trauma and degenerative diseases present a serious health problem. Osteoarthritis alone affects more than 27 million people in the U.S. and is predicted to affect 1 in 2 people in their lifetime. Chondrocytes in the cartilage have a poor regenerative capacity, and most articular injuries cannot heal without open surgery or other invasive intervention. Autologous cartilage implantation, or ACI, and the microfracture technology are the established treatments for cartilage repair, but these methods are often limited by insufficient cartilage supply, continual cartilage degeneration, and the formation of fibrosis cartilages that do not provide sufficient mechanical strength to sustain body loads. Stem cell-based cartilage regeneration provides tremendous hopes for people suffering from cartilage injuries. The success of stem cell chondrogenesis relies on an ideal cell niche that provide properly orchestrated niche properties, forming the key elements that are crucial for chondrogenesis, including biochemical and biophysical cues, to promote the desired stem cell bioactivities. Macropores, the pore space no smaller than the typical cells, is a highly potential mechanosensing regulator to control the stem cell chondrogenic differentiation. However, the mechanisms by which niche properties in three-dimensions regulate stem cells chondrogenesis remain largely unclear. A platform to support the fundamental study on the complex interaction between niche properties and stem cell bioactivities is currently lacking. Given the complex nature of how stem cells respond to niche properties in our body, a three-dimensional niche model that can easily control macroporosity, matrix elasticity and cell morphology will facilitate a mechanistic study on the niche effect on chondrogenesis, and may one day lead to an ideal cell niche to realize the ultimate goal of complete cartilage repair. This project will conduct the first step to attempt such goal by using the crosslinkable microribbons, which are ribbon-like and micron-sized hydrogels that emerged in the past couple years, as the building blocks to construct the model cell niches to provide a vast variation of pore size, cell shape, and elasticity. The microribbons provide the following functions to facilitate a comprehensive study on how niche compositions impact stem cells chondrogenesis: 1) direct cell encapsulation in three dimensions, 2) control of cell shape by tunable macropore size, 3) independently tunable biochemical and mechanical cues, and 4) interconnected macroporosity to retain the ECM components produced by cells. Using macroribbons, the investigators address 3 aims: 1) To develop a 3D model that exposes human mesenchymal stems cells (MSC) to various macropore sizes and matrix elasticity, and to evaluate the cellular properties of MSC with regard to cell shape, focal adhesion, cytoskeleton organization, and transcription factor activity; 2) To determine how macropore size, matrix elasticity and the associated cellular properties influence the chondrogenic differentiation of human MSC; and 3): To understand how macroporosity and matrix elasticity influence the production of cartilage matrix and the stability of chondrocyte phenotypes. If successful, numerous patients suffering from cartilage injuries can benefit from the 3D macroporous cell niche developed. The proposed project spans multiple disciplines including engineering, biology and medicine. Students carrying out proposed research will benefit greatly by being exposed to a variety of experiments including organic synthesis, nanoindentation, stem cell cultivation and cellular assays. New graduate-level courses incorporating the elements from the proposed research will be developed to translate the research outcomes from lab benches to the classroom. Technology used for the proposed project, such as wet-spinning and scaffold fabrication, will be contributed to the outreaching programs hosted by the PI and the college of engineering, providing short lectures, summer camps, and hands-on lab experience to high school teachers and underrepresented K-12 students. The PI and co-PI will actively recruit female and minority students to conduct the proposed research.