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Introduction: The meniscus is essential for load distribution, shock absorption, and knee joint stability. Its function depends on the organization of collagen fibers in both radial and circumferential directions. Meniscus damage is often a precursor for degenerative conditions to the articular cartilage (AC). Treatment of meniscal tears is limited to the avascular areas[2]. Current artificial meniscus implants (e.g., CMI® or ACTIfit®) [3] offer clinical relief, but lack the mechanical integrity required for long-term function. To address this limitation, we developed a 3D-printed implant that combines the collagen alignment properties of polycaprolactone nanofibers printed with melt electrofibrillation (MEF) [1], with the mechanical properties of melt electrowritten (MEW) PCL microfiber scaffolds.[1]
Methods: PCL microfibers (MEW) and PCL/polyvinyl acetate (PVAc) nanofibers (MEF) were co-printed using dual syringe setup on a RegenHU 3D Discovery printer (Fig.1A). After printing, PVAc was dissolved using 70% ethanol and PBS to reveal the PCL nanofibrils. Scanning Electron Microscopy confirmed nanofiber integration within the reinforcing scaffold (Fig. 1B). The compressive E-modulus of the converged MEW-MEF constructs was measured using a dynamic mechanical analyzer. To assess cell-material interactions, scaffolds were seeded with human meniscus progenitor cells (hMPCs, 5×10⁶cells/ml) (Fig.1E). Type I and II collagen deposition were evaluated via immunohistochemistry, cell deposition via H&E, glycosaminoglycan via Safranin-O/Fast-green and collagen alignment via Picrosirius-red and polarized light (Fig.1F).
Results: Nanofibers were successfully integrated into the reinforced MEW scaffold (Fig.1A,1B), and co-printing MEF and MEW fibers yielded meniscus constructs without compromising mechanical stability. Scaled-down (1:2) meniscus implants were fabricated by alternating circumferential and radial nanofiber orientations to mimic native fiber architecture (Fig.1C,1D). MEF nanofibers effectively guided hMPC alignment and promoted organized type I collagen deposition (Fig.1E), without glycosaminoglycan accumulation, consistent with native-healthy meniscus composition. Polarized light confirmed that collagen deposition aligned with the underlying printed nanofibers (Fig.1F).
Conclusion: We present a cell-laden 3D-printed meniscus implant featuring a nanofiber architecture that guides cell-mediated type I collagen alignment. This approach combines the immediate mechanical stability of microfiber reinforcement with the ability of nanofibers to direct organized collagen deposition, offering a promising strategy for achieving long-term structural and functional integrity in meniscus repair.
[1] M. Ryma et al., 2021
[2] K. Vadodaria et al., 2019
[3] R. D. Linke et al., 2006
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