Speaker
Description
Introduction
Cartilage defects pose significant challenges in terms of healing. Current treatments have limitations in size, availability, or durability.[1,2] Biofabrication aims to restore tissue functionality by placing biological active components in a pre-defined 3D organization, typically using soft hydrogels for cell preferences.[3] These hydrogels can be mechanically reinforced with microfiber structures generated with melt electrowriting (MEW).[4] Small scale (diameter 6mm, A=28 mm2) Fabricated osteochondral plugs with cell-laden hydrogel reinforced with MEW meshes are stable in vivo.[5] Translating this towards patient-specific implants, requires consideration of an overall increase in size (>2 cm2) and the local differences in cartilage mechanical properties throughout the articulating joint. This study investigates the local, anisotropic mechanical properties of a large sized MEW-reinforced cell-laden hydrogel scaffold.
Materials and methods
Polycaprolactone (PCL) microfiber box-shaped scaffolds were fabricated using melt electrowriting (MEW) with inter-fiber spacing from 200 x 200 μm to 500 x 500 μm with 100 μm increments. A large-scale (15 cm2) anisotropic scaffold was designed with fiber spacing ranging from 300, 400, and 500 μm, embedded with equine articular cartilage progenitor cells (ACPC) and cell-free gelatine methacryloyl (gelMA), and crosslinked with dichloro-ruthenium (II) hexahydrate and sodium persulfate. Mechanical testing was performed on cell-free constructs, and the compressive E-moduli were measured between 10% and 15% strain. The cell-laden constructs were cultured for 28 days in chondrogenic differentiation medium. Post-culture, the constructs were analyzed for GAG, collagen type I and II, metabolic activity, and cell morphology.
Results
By altering the inter fibre spacing of gelMA embedded MEW-reinforcement, the compressive modulus varied from 0.49 ± 0.18 MPa for 500 μm to 2.52 ± 0.17 MPa for 200 μm. The large sized anisotropic scaffold showed similar mechanical behavior, resulting in an anisotropic mechanical design of the scaffold, which could be distinguished as a high (300 μm), medium (400 μm), and low (500 μm) density fiber zone. The ACPCs in the cell-laden constructs showed homogenous behavior in the different regions and staining showed production of GAGs and collagen type II. Biochemistry showed a lower DNA content in the low-density zone, but higher GAG production compared to the medium density zones.
Conclusion
This study shows the effect of mechanical reinforcement of cell-laden hydrogel scaffolds using scaffolds with anisotropic designs. Manipulating the internal box-spacing enables to regulate the mechanical properties of the scaffold, while showing homogenous behavior of cartilage cells throughout a large-scale mechanically anisotropic scaffold design. These findings allow to produce clinically-relevant sized constructs with personalized features, while providing a viable environment for cartilage cells.
References
[1] M. Howell et al., 2021
[2] J. Julin, et al., 2010
[3] R. Levato et al., 2020
[4] J. Visser et al., 2015
[5] M. de Ruijter et al., 2023
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