Dynamic loading leads to increased metabolic activity and spatial redistribution of viable cell density in nucleus pulposus tissue.

Background: Nucleus pulposus (NP) cell density is orchestrated by an interplay between nutrient supply and metabolite accumulation. Physiological loading is essential for tissue homeostasis. However, dynamic loading is also believed to increase metabolic activity and could thereby interfere with cell density regulation and regenerative strategies.

A bovine nucleus pulposus explant culture model.

Low back pain is a global health problem that is frequently caused by intervertebral disc degeneration (IVDD). Sulfated glycosaminoglycans (sGAGs) give the healthy nucleus pulposus (NP) a high fixed charge density (FCD), which creates an osmotic pressure that enables the disc to withstand high compressive forces. However, during IVDD sGAG reduction in the NP compromises biomechanical function.

Biomimetic Mechanically Strong One-Dimensional Hydroxyapatite/Poly(d,l-lactide) Composite Inducing Formation of Anisotropic Collagen Matrix.

Natural bone is a complex composite, consisting predominantly of collagen and hydroxyapatite (HA), which form a highly organized, hierarchical structure from the nano- to the macroscale. Because of its biphasic, anisotropic, ultrafine structural design, bone tissue possesses excellent mechanical properties. Herein, inspired by the composition and microstructure of natural bone, a biphasic composite consisting of highly aligned strontium/copper-doped one-dimensional hydroxyapatite (Sr/Cu-doped 1D HA) and poly(d,l-lactide) (PDLA) was developed.

Bi-layered micro-fibre reinforced hydrogels for articular cartilage regeneration.

Articular cartilage has limited capacity for regeneration and when damaged cannot be repaired with currently available metallic or synthetic implants. We aim to bioengineer a microfibre-reinforced hydrogel that can capture the zonal depth-dependent mechanical properties of native cartilage, and simultaneously support neo-cartilage formation. With this goal, a sophisticated bi-layered microfibre architecture, combining a densely distributed crossed fibre mat (superficial tangential zone, STZ) and a uniform box structure (middle and deep zone, MDZ), was successfully manufactured via melt electrospinning and combined with a gelatin-methacrylamide hydrogel.

Hypotonicity differentially affects inflammatory marker production by nucleus pulposus tissue in simulated disc degeneration versus herniation.

Inflammatory cytokines play an important role in intervertebral disc degeneration. Although largely produced by immune cells, nucleus pulposus (NP) cells can also secrete them under various conditions, for example, under free swelling. Thus, tissue hypotonicity may be an inflammatory trigger for NP cells.

Bio-ink development for three-dimensional bioprinting of hetero-cellular cartilage constructs.

Bioprinting is a promising tool to fabricate organized cartilage. This study aimed to investigate the printability of gelatin-methacryloyl/gellan gum (gelMA/gellan) hydrogels with and without methacrylated hyaluronic acid (HAMA), and to explore (zone-specific) chondrogenesis of chondrocytes, articular cartilage progenitor cells (ACPCs), and multipotent mesenchymal stromal cells (MSCs) embedded in these bio-inks.The incorporating of HAMA in gelMA/gellan bio-ink increased filament stability, as measured using a filament collapse assay, but did not influence (zone-specific) chondrogenesis of any of the cell types.

Three-Dimensional Bioprinting and Its Potential in the Field of Articular Cartilage Regeneration.

Three-dimensional (3D) bioprinting techniques can be used for the fabrication of personalized, regenerative constructs for tissue repair. The current article provides insight into the potential and opportunities of 3D bioprinting for the fabrication of cartilage regenerative constructs. Although 3D printing is already used in the orthopedic clinic, the shift toward 3D bioprinting has not yet occurred.

Ex vivo model unravelling cell distribution effect in hydrogels for cartilage repair.

The implantation of chondrocyte-laden hydrogels is a promising cartilage repair strategy. Chondrocytes can be spatially positioned in hydrogels and thus in defects, while current clinical cell therapies introduce chondrocytes in the defect depth. The main aim of this study was to evaluate the effect of spatial chondrocyte distribution on the reparative process.

Yield stress determines bioprintability of hydrogels based on gelatin-methacryloyl and gellan gum for cartilage bioprinting.

Bioprinting of chondrocyte-laden hydrogels facilitates the fabrication of constructs with controlled organization and shape e.g. for articular cartilage implants.

A Synthetic Thermosensitive Hydrogel for Cartilage Bioprinting and Its Biofunctionalization with Polysaccharides.

Hydrogels based on triblock copolymers of polyethylene glycol and partially methacrylated poly[N-(2-hydroxypropyl) methacrylamide mono/dilactate] make up an attractive class of biomaterials because of their biodegradability, cytocompatibility, and tunable thermoresponsive and mechanical properties. If these properties are fine-tuned, the hydrogels can be three-dimensionally bioprinted, to generate, for instance, constructs for cartilage repair. This study investigated whether hydrogels based on the polymer mentioned above with a 10% degree of methacrylation (M10P10) support cartilage formation by chondrocytes and whether the incorporation of methacrylated chondroitin sulfate (CSMA) or methacrylated hyaluronic acid (HAMA) can improve the mechanical properties, long-term stability, and printability.

A Well-Controlled Nucleus Pulposus Tissue Culture System with Injection Port for Evaluating Regenerative Therapies.

In vitro evaluation of nucleus pulposus (NP) tissue regeneration would be useful, but current systems for NP culture are not ideal for injections. The aim of this study was to develop a long-term culture system for NP tissue that allows injections of regenerative agents. Bovine caudal NPs were harvested and placed in the newly designed culture system.