Regeneration of Osteochondral Defects Using Developmentally Inspired Cartilaginous Templates

Abstract

There is increased interest in recapitulating aspects of development when designing new tissue engineering strategies. Long bones and their epiphyses are formed through endochondral ossification, a process by which a cartilage template develops in response to genetic and environmental cues to generate a bone organ. The objective of this study was to evaluate the capacity of engineered cartilage templates to regenerate osteochondral defects created in the femoral condyle of skeletally mature rabbits. To this end, bone marrow derived mesenchymal stem cells (BMSCs) were encapsulated in RGD-functionalized, γ-irradiated alginate hydrogel and chondrogenically primed in vitro to engineer cartilage templates tailored for osteochondral defect regeneration. While comparable levels of healing were observed in the bony region of empty and treated groups, the quality of healing was notably different in the chondral region of these defects. Mechanical testing revealed that treatment with engineered cartilage templates promoted the development of a stiffer repair tissue at the articular surface, which correlated with histomorphometric analysis demonstrating the formation of a more hyaline cartilage-like repair tissue. Next, a computational mechanobiological model was used to better understand how local environmental cues were regulating the regenerative process in vivo. This model predicted that higher strains and lower levels of oxygen in the chondral region of the defect were preventing cartilage template progression along the endochondral pathway, with hyaline cartilage or fibrocartilage eventually forming depending on local strain magnitudes. In contrast, higher levels of oxygen and lower magnitudes of strain in the osseous region of the defect facilitated progression of the engineered cartilage template along an endochondral pathway. In conclusion, this study demonstrates that engineered cartilage templates can enhance osteochondral defect regeneration, pointing to the potential for developmentally inspired soft tissue templates, engineered using BMSCs, to regenerate damaged and diseased joints. Impact StatementSuccessfully treating osteochondral defects involves regenerating both the damaged articular cartilage and the underlying subchondral bone, in addition to the complex interface that separates these tissues. In this study we demonstrate that a cartilage template, engineered using bone marrow derived MSCs, can enhance the regeneration of such defects and promote the development of a more mechanically functional repair tissue. We also use a computational mechanobiological model to understand how joint specific environmental factors, specifically oxygen levels and tissue strains, regulate the conversion of the engineered template into cartilage and bone in vivo.

Patterned, organoid-based cartilaginous implants exhibit zone specific functionality forming osteochondral-like tissues in vivo

“…Regarding osteochondral tissues, a distinct engineered cartilage intermediate in vitro could potentially mature into nonmineralized, mineralized cartilage or bone upon implantation in vivo. Cartilage intermediate tissues from lapine bone marrow-derived mesenchymal stromal cells (BMSC) or human periosteum derived cells (hPDC) have been demonstrated to contribute to the regeneration of osteochondral defects, illustrating the power of developmentally inspired approaches [25,26].…”

Combinations of Hydrogels and Mesenchymal Stromal Cells (MSCs) for Cartilage Tissue Engineering—A Review of the Literature

“…MSC-laden AL hydrogels have been shown to promote the formation of repair tissue and regeneration of osteochondral defects in rabbit models [ 42 ]. Research has also shown that hypoxia mimicking AL hydrogels loaded with growth factors guide seeded cells toward a more chondrogenic phenotype while preventing osteogenic and hypertrophic de-differentiation [ 43 ].…”

“…Research has also shown that hypoxia mimicking AL hydrogels loaded with growth factors guide seeded cells toward a more chondrogenic phenotype while preventing osteogenic and hypertrophic de-differentiation [ 43 ]. This effect may be enhanced when paired with shear and compression forces [ 42 ]. The combination of HA hydrogels with AL microspheres has been shown to retain the activity of transported growth factors and induce chondrogenesis in encapsulated MSCs both in vitro and in vivo [ 34 ].…”

Advancements and Frontiers in the High Performance of Natural Hydrogels for Cartilage Tissue Engineering

“…Eames et al found that the ALG/HAP complex could trigger the chondrocytes to secrete a calcified matrix, which was testified by the favorable survival and proliferation of chondrocytes in the ALG/HAP structure and high expression level of calcified cartilage markers (You et al, 2019). Embedding bone marrow-derived mesenchymal stem cells (bMSCs) in RGD (arginine/glycine/aspartic acid)-functionalized, γ-ray alginate hydrogels could enhance the osteochondral regeneration and promote the development of a more mechanically functional repair tissue (Critchley et al, 2019). However, the poor mechanical properties of ALG-based hydrogels limited their biomedical potential in osteochondral tissue regeneration.…”