Utilizing Osteocyte Derived Factors to Enhance Cell Viability and Osteogenic Matrix Deposition within IPN Hydrogels

Abstract

Many bone defects arising due to traumatic injury, disease, or surgery are unable to regenerate, requiring intervention. More than four million graft procedures are performed each year to treat these defects making bone the second most commonly transplanted tissue worldwide. However, these types of graft suffer from a limited supply, a second surgical site, donor site morbidity, and pain. Due to the unmet clinical need for new materials to promote skeletal repair, this study aimed to produce novel biomimetic materials to enhance stem/stromal cell osteogenesis and bone repair by recapitulating aspects of the biophysical and biochemical cues found within the bone microenvironment. Utilizing a collagen type I–alginate interpenetrating polymer network we fabricated a material which mirrors the mechanical and structural properties of unmineralized bone, consisting of a porous fibrous matrix with a young’s modulus of 64 kPa, both of which have been shown to enhance mesenchymal stromal/stem cell (MSC) osteogenesis. Moreover, by combining this material with biochemical paracrine factors released by statically cultured and mechanically stimulated osteocytes, we further mirrored the biochemical environment of the bone niche, enhancing stromal/stem cell viability, differentiation, and matrix deposition. Therefore, this biomimetic material represents a novel approach to promote skeletal repair.

Stiffness-mediated mesenchymal stem cell fate decision in 3D-bioprinted hydrogels

“…The cellular microenvironment can affect MSC differentiation into various types of adult cells, such as osteoblasts, adipocytes and neuroblasts, through the synergistic effects of both biochemical and biophysical cues [ 22–25 ]. For example, several studies have shown that MSCs encapsulated within 3D matrices with tuneable stiffness can initiate osteogenic and adipogenic differentiation programmes [ 24 , 35 , 36 ]. Although biophysical cues control MSC lineage specification probably via cytoskeletal reorganization, the complete mechanism is largely unclear.…”

“…Stiffness-driven stem cell differentiation is probably directed by mechanotransduction effects, as stem cells are usually mechanosensitive at the initiation of differentiation [ 33 ]. The mechanotransduction effects can further affect intracellular and intercellular signalling pathways and ultimately result in stiffness-regulated stem cell behaviour [ 36 , 37 ]. YAP is a key protein in the Hippo pathway of mechano-transduction [ 45 ], and many studies have shown that the mechano-transduction triggered by matrix stiffness in stem cells is mediated by YAP [ 26 , 27 , 46 , 47 ].…”

Collagen–Alginate Composite Hydrogel: Application in Tissue Engineering and Biomedical Sciences

“…While CAC hydrogel can support bMSCs survival and proliferation, bMSCs osteogenesis happens in the presence of osteo-inductive molecules [ 104 , 106 ]. CAC hydrogel can be incorporated with other bioactive agents to provide mechanical cues to bMSCs.…”

The Impact of the Extracellular Matrix Environment on Sost Expression by the MLO-Y4 Osteocyte Cell Line

“…MLO-Y4 cells share similar features with osteocytes such as dendritic processes, low alkaline phosphatase production, and high osteocalcin, and connexin 43 production [ 15 ]. The MLO-Y4 cell line has facilitated the discovery and validation of numerous mechanisms in bone, including that fluid shear stress can result in the synthesis and release of bioactive molecules that initiate signalling pathways to prevent apoptosis, recruit osteoprogenitors, and encourage the osteogenic differentiation of such cells [ 6 , 16 , 17 , 18 , 19 ].…”