Single-Step Extrusion Printing of Microgrooved Annulus Fibrosus Scaffolds via Patterned Nozzles

TL;DR

A new 3D-printing method creates microgrooved scaffolds that guide cell alignment and support potential spinal disc repair.

Contribution

A single-step extrusion-printing method with patterned nozzles to create microgrooved scaffolds that mimic the annulus fibrosus structure.

Findings

Patterned nozzles enabled fabrication of PCL scaffolds with aligned microgrooves promoting cell organization.

Cells cultured on patterned scaffolds aligned within grooves and deposited extracellular matrix in guided arrays.

TGF-β3 supplementation upregulated outer AF markers, and patterned scaffolds increased TAGLN expression.

Abstract

Intervertebral disk pathology, including disk herniation and degeneration, is a major contributor to chronic low back pain, and when conservative treatment fails, surgical management often involves discectomy-based procedures that leave residual annulus fibrosus (AF) defects associated with reherniation and progressive degeneration. These limitations have motivated interest in regenerative strategies using biomaterial scaffolds; however, reproducing the hierarchical, angle-ply architecture of the AF remains challenging. Here, we present a single-step extrusion-based 3D-printing approach to fabricate polycaprolactone (PCL) scaffolds with aligned microscale surface grooves that promote AF-like organization. Patterned nozzles with circumferential peaks generated uniaxial concave microgrooves (10–17 µm wide) directly during printing, enabling formation of multilamellar angle-ply constructs. Human bone marrow-derived mesenchymal stem cells cultured on patterned scaffolds aligned longitudinally within concave grooves, forming end-to-end arrays that guided extracellular matrix deposition. Gene expression analysis showed that topographical cues governed cellular organization without significantly altering gene expression profiles, while TGF-β3 supplementation upregulated outer AF-associated markers, including COL1, COL12, SFRP2, MKX, MCAM, and SCX. TAGLN expression increased specifically on patterned scaffolds in the absence of TGF-β3, indicating an association between microgroove-guided cellular organization and TAGLN expression, warranting further investigation into potential tension-related mechanisms. This novel single-step extrusion-printing approach leverages custom nozzle geometry to impart concave microgrooves, facilitating scalable fabrication of multilamellar angle-ply scaffolds that induce aligned cellular organization and support potential applications in annulus fibrosus repair, as well as mechanobiological studies of anisotropic musculoskeletal tissues.

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