Human iPS cell-derived cartilaginous tissue spatially and functionally replaces nucleus pulposus

The loss of nucleus pulposus (NP) precedes the intervertebral disk (IVD) degeneration that causes back pain. Here, we demonstrate that the implantation of human iPS cell-derived cartilaginous tissue (hiPS-Cart) restores this loss by replacing lost NP spatially and functionally. NP cells consist of notochordal NP cells and chondrocyte-like NP cells. Single cell RNA sequencing (scRNA-seq) analysis revealed that cells in hiPS-Cart corresponded to chondrocyte-like NP cells but not to notochordal NP cells. The implantation of hiPS-Cart into a nuclectomized space of IVD in nude rats prevented the degeneration of the IVD and preserved its mechanical properties. hiPS-Cart survived and occupied the nuclectomized space for at least six months after implantation, indicating spatial and functional replacement of lost NP by hiPS-Cart. Further scRNA-seq analysis revealed that hiPS-Cart cells changed their profile after implantation, differentiating into two lineages that are metabolically distinct from each other. However, post-implanted hiPS-Cart cells corresponded to chondrocyte-like NP cells only and did not develop into notochordal NP cells, suggesting that chondrocyte-like NP cells are nearly sufficient for NP function. The data collectively indicate that hiPS-Cart is a candidate implant for regenerating NP spatially and functionally and preventing IVD degeneration.Kamatani T., Hagizawa H., Yarimitsu S., et al. Human iPS cell-derived cartilaginous tissue spatially and functionally replaces nucleus pulposus. Biomaterials 284, 121491 (2022); https://doi.org/10.1016/j.biomaterials.2022.121491

Effect of collagen-induced residual stress on the frictional property of articular cartilage

Previous findings, such as split-line of the articular cartilage surface and curving of sliced cartilage specimen, would suggest that residual stress is contained in articular cartilage. This study was performed to determine the effect of collagen fibre-induced residual stress on the biphasic lubrication property of articular cartilage. A fibre-reinforced poroelastic model of articular cartilage was developed in Abaqus. In the model, residual stress was contained in the collagen fibre in the surface layer by applying 1–5% of tensile strain. Reciprocating friction analysis was performed between the model and a sphere at a friction speed of 1.0–10.0 mm/s. Results revealed that the coefficients of start-up and dynamic friction at second friction cycle were lower in residual stress model than in no-residual stress model, with the largest decreases observed at a friction speed of 1 mm/s. It was observed that rehydration was promoted in the bearing area in residual stress model. These results suggest that collagen-induced residual stress plays an important role in enhancing the biphasic lubrication property of articular cartilage

Transitional behaviour between biphasic lubrication and soft elastohydrodynamic lubrication of poly(vinyl alcohol) hydrogel using microelectromechanical system pressure sensor

The soft hydrogel material is expected for a candidate material as biomimetic artificial cartilage with synergistic functionalities of adaptive multimode lubrication. In boundary lubrication mode of hydrogel material, the biphasic lubrication mechanism cooperatively exerts its functionality. In hydrodynamic lubrication mode, it is preferable that the lubricating surfaces be impermeable to trap the fluid pressure in contact surfaces, whereas the actual biphasic material like a hydrogel is a permeable material with surface porosity. It is indicated that the interstitial fluid pressurisation in the permeable biphasic material can contribute to significant fluid load support under lower sliding speed condition. So, the authors examined how the contrary fluid pressure effect appears in the transition from the boundary lubrication mode to soft elastohydrodynamic lubrication mode. In the experiment, a small pressure sensor was utilised to measure the in-situ fluid pressure in sliding condition. Although the experimental condition of this study was selective, the result showed a possibility of the negative effect of the biphasic surface, in which the permeable surface diminished the hydrodynamic fluid pressure. This means that one should manage and enhance the biphasic lubrication abilities in wide operation range when the hydrogel material was used as a load bearing material

On the replacement of articular cartilage: The friction of PVA hydrogel layer in hip simulator test

The present study focuses on friction evaluation of the polyvinyl alcohol (PVA) hydrogel layer, an anticipative material for cartilage replacement. The experiments were carried out in a ball-in-socket configuration using a pendulum hip simulator. The friction coefficients of ceramic-on-hydrogel pairs were compared with those of commercial implants (metal/ceramic heads vs UHMWPE, HXPE and metal/ceramic sockets). The effects of hydrogel ageing and hydration were studied, among others. The use of PVA inserts caused up to 98% reduction in friction coefficient compared to original hip pairs. The application of PVA for local or even complete cartilage replacement seems to be an outstanding opportunity in implantology. © 2022 Elsevier LtdJapan Society for the Promotion of Science, KAKEN: JP21H04535; Grantová Agentura České Republiky, GA ČR: 20-00483S, 22-02154

Influence of collagen fibre orientation on the frictional properties of articular cartilage

Articular cartilage has a unique collagen fibre network structure that exhibits both anisotropy and depth dependency. Collagen fibre orientation in a cross-section parallel to the articular cartilage surface may affect the lubrication properties of articular cartilage. The effect of collagen fibre orientation on the frictional properties of articular cartilage was examined through finite element analysis of the friction. Specifically, a three-dimensional fibre-reinforced poroelastic biphasic model was used to determine the influence of collagen fibril orientation on the frictional properties of articular cartilage. The simulations reveal that collagen fibre orientation has a significant influence on the deformation behaviour of articular cartilage in front of and behind the contact area. The coefficient of dynamic friction was lower in the direction parallel to the collagen fibre orientation than in the direction perpendicular to the collagen fibre orientation, regardless of the indenter speed.Special Issue:In memoriam: the first anniversary of the late Professor Duncan Dowson in the area of Biotribolog

Human iPS cell-derived cartilaginous tissue spatially and functionally replaces nucleus pulposus

iPS細胞から作った軟骨様髄核により椎間板を再生 --椎間板変性に伴う腰痛疾患を治療しうる新技術--. 京都大学プレスリリース. 2022-04-18.The loss of nucleus pulposus (NP) precedes the intervertebral disk (IVD) degeneration that causes back pain. Here, we demonstrate that the implantation of human iPS cell-derived cartilaginous tissue (hiPS-Cart) restores this loss by replacing lost NP spatially and functionally. NP cells consist of notochordal NP cells and chondrocyte-like NP cells. Single cell RNA sequencing (scRNA-seq) analysis revealed that cells in hiPS-Cart corresponded to chondrocyte-like NP cells but not to notochordal NP cells. The implantation of hiPS-Cart into a nuclectomized space of IVD in nude rats prevented the degeneration of the IVD and preserved its mechanical properties. hiPS-Cart survived and occupied the nuclectomized space for at least six months after implantation, indicating spatial and functional replacement of lost NP by hiPS-Cart. Further scRNA-seq analysis revealed that hiPS-Cart cells changed their profile after implantation, differentiating into two lineages that are metabolically distinct from each other. However, post-implanted hiPS-Cart cells corresponded to chondrocyte-like NP cells only and did not develop into notochordal NP cells, suggesting that chondrocyte-like NP cells are nearly sufficient for NP function. The data collectively indicate that hiPS-Cart is a candidate implant for regenerating NP spatially and functionally and preventing IVD degeneration