Enhanced nutrient transport improves the depth-dependent properties of tri-layered engineered cartilage constructs with zonal co-culture of chondrocytes and MSCs

Abstract

Biomimetic design in cartilage tissue engineering is a challenge given the complexity of the native tissue. While numerous studies have generated constructs with near-native bulk properties, recapitulating the depth-dependent features of native tissue remains a challenge. Furthermore, limitations in nutrient transport and matrix accumulation in engineered constructs hinders maturation within the central core of large constructs. To overcome these limitations, we fabricated tri-layered constructs that recapitulate the depth-dependent cellular organization and functional properties of native tissue using zonally derived chondrocytes co-cultured with MSCs. We also introduced porous hollow fibers (HFs) and HFs/cotton threads to enhance nutrient transport. Our results showed that tri-layered constructs with depth-dependent organization and properties could be fabricated. The addition of HFs or HFs/threads improved matrix accumulation in the central core region. With HF/threads, the local modulus in the deep region of tri-layered constructs nearly matched that of native tissue, though the properties in the central regions remained lower. These constructs reproduced the zonal organization and depth-dependent properties of native tissue, and demonstrate that a layer-by-layer fabrication scheme holds promise for the biomimetic repair of focal cartilage defects.

Extracellular vesicles mediate improved functional outcomes in engineered cartilage produced from MSC/chondrocyte cocultures

“…1A). Full-thickness juvenile cartilage segments were excised from the femoral condyle and divided into three layers (40,41). The topmost 100-μm layer at the articular surface was separated and taken as the superficial zone (S).…”

Mimicking nature: Fabrication of 3D anisotropic electrospun polycaprolactone scaffolds for cartilage tissue engineering applications

“…Recent studies have reported that advanced hydrogels, including both injectable 18 and stimuli responsive 19 , are promising biomimetic platforms for regenerating cartilage since they can guarantee zonal-specific cell responses, for example, by introduction of stiffness gradients 20 or by assembly different layers with specific gelation formulations that consequently ensure particular properties 21 . Additionally, new designs have already overcome some limitations related with the reduced nutrient exchange in the inte rna l regions of tri-layered hydrogels by introducing porous hollow fibres to transport nutrient/waste across the scaffold with the purpose of supporting an optimized and uniform cell behaviour 22 .…”

Promise, progress, and problems in whole disc tissue engineering

“…The culture and maturation of large engineered constructs also poses significant challenges, as diffusional constraints of media components can result in heterogeneity in cell viability and matrix distribution from the periphery to the center of the construct . This has been well documented in the cartilage tissue engineering literature, where substantial differences in mechanical function across the construct depth have been reported . In our work on engineered discs, we noted significant heterogeneity in matrix distribution and loss of cell viability in the center of constructs that were scaled up from a size appropriate for use in the rat caudal spine (2 mm high, 5 mm diameter) to a size comparable to the goat and human cervical disc space (6 mm high, 20 mm diameter) (Figure ) .…”

“…In our work on engineered discs, we noted significant heterogeneity in matrix distribution and loss of cell viability in the center of constructs that were scaled up from a size appropriate for use in the rat caudal spine (2 mm high, 5 mm diameter) to a size comparable to the goat and human cervical disc space (6 mm high, 20 mm diameter) (Figure ) . A number of strategies could be implemented to enhance transport into these large‐size engineered discs in culture, including the inclusion of nutrient channels through the construct depth, the use of alternate media formulations that promote tissue formation through the depth (such as the use of latent TGF‐β as a component of chondrogenic media), and culture in bioreactors that are designed to promote the convective transport of vital nutrients into these larger constructs via cyclic mechanical loading . Many of these techniques have been applied to cartilage tissue engineering, and thus lessons learned from that field may expedite the successful generation of large‐scale engineered discs.…”

“…76 A number of strategies could be implemented to enhance transport into these large-size engineered discs in culture, including the inclusion of nutrient channels through the construct depth, the use of alternate media formulations that promote tissue formation through the depth (such as the use of latent TGF-β as a component of chondrogenic media), and culture in bioreactors that are designed to promote the convective transport of vital nutrients into these larger constructs via cyclic mechanical loading. 57,74,75,77,78 Many of these techniques have been applied to cartilage tissue engineering, and thus lessons learned from that field may expedite the successful generation of large-scale engineered discs.…”