Zonal-Specific Mineralized Scaffolds for Osteochondral Regeneration - PROJECT SUMMARY/ ABSTRACT Biomineralization is an essential process controlling the structural development and pathological progression of several tissues and organisms. Depending on the degree of biomineralization, collagen fibers can be as compliant as tendons and ligaments (without minerals), as rigid as bones (with abundant minerals), or have a gradient rigidity as cartilage (with zonal-specific minerals), in the musculoskeletal system. On the other hand, ectopic biomineralization often results in severe diseases. For instance, calcification of vascular tissues may lead to thrombus formation or atherosclerotic lesions, while calcification of articular cartilage is a sign of osteoarthritis (OA) progression. Therefore, it is essential to understand the mechanisms of biomineralization and mimic the mineralization process in vitro to replicate the composition, structure, and properties of mineralized tissues. Osteochondral (OC) tissue has a multiphasic structure consisting mainly of articular cartilage and subchondral bone with zonal-dependent mineralization. Specifically, the intrafibrillar minerals (within collagen fibers) and extrafibrillar minerals (on the surface of collagen fibers) constitute 85.8 wt.%, 65.1 wt.%, and 0% of the dry weight of the subchondral bone, calcified cartilage layer, and cartilage layer, respectively. Due to this complex structure and poor intrinsic regeneration capability, OC repair is highly challenging. Tissue engineering approaches using multizonal scaffolds have been shown as effective alternatives for enhanced OC regeneration. The objective of this application is to develop and evaluate a zonal-specific mineralized scaffold optimal for OC regeneration by controlling the mineralization of collagen. The central hypothesis is that the progenitor cell- seeded multizonal scaffold mimicking the hierarchical microstructure and composition of native OC tissue with sustained local release of functional trace elements is a promising therapeutic option to improve OC regeneration. To test our hypothesis, the objective of this proposal will be achieved by three specific aims: (1) Design and fabricate individual zones with different compositions and fiber orientations by controlling biomimetic mineralization. (2) Seamlessly bond Characterize and individual zones into monolithic multizonal scaffolds. (3) Evaluation of in vitro osteochondral cell differentiation and in vivo osteochondral tissue formation within the progenitor cell-loaded multizonal scaffold. The innovation lies in (1) designing highly biomimetic five-zone scaffolds with zonal-dependent mineralization and fiber orientation. (2) for the first time, considering the intrafibrillar and extrafibrillar features in the subchondral bone zone. (3) achieving sustained local release of functional trace elements. (4) using chondroprogenitor cells and BMSCs harboring fluorescent reporters to virtualize zonal-specific osteochondral differentiation in situ. This application is partially designed to create an appropriate undergraduate training experience in biomaterials development and evaluation by advanced imaging technologies, particularly for the first class of Biomedical Engineering students in the university’s history.
