Mesenchymal stromal cell-based therapy for cartilage regeneration in knee osteoarthritis

Functionalized Hydrogels for Cartilage Repair: The Value of Secretome-Instructive Signaling

Cartilage repair has been a challenge in the medical field for many years. Although treatments that alleviate pain and injury are available, none can effectively regenerate the cartilage. Currently, regenerative medicine and tissue engineering are among the developed strategies to treat cartilage injury. The use of stem cells, associated or not with scaffolds, has shown potential in cartilage regeneration. However, it is currently known that the effect of stem cells occurs mainly through the secretion of paracrine factors that act on local cells. In this review, we will address the use of the secretome—a set of bioactive factors (soluble factors and extracellular vesicles) secreted by the cells—of mesenchymal stem cells as a treatment for cartilage regeneration. We will also discuss methodologies for priming the secretome to enhance the chondroregenerative potential. In addition, considering the difficulty of delivering therapies to the injured cartilage site, we will address works that use hydrogels functionalized with growth factors and secretome components. We aim to show that secretome-functionalized hydrogels can be an exciting approach to cell-free cartilage repair therapy.

Acellular cartilage matrix biomimetic scaffold with immediate enrichment of autologous bone marrow mononuclear cells to repair articular cartilage defects

Functional repair of articular cartilage defects is always a great challenge in joint surgery clinically. Tissue engineering strategies that combine autologous cell implantation with three-dimensional scaffolds have proven effective for repairing articular cartilage tissue. However, it faces the problem of cell sources and scaffold materials. Autologous chondrocytes and bone marrow are difficult to popularize clinically due to limited donor sources and low mononuclear cell (MNC) concentrations, respectively. The density gradient centrifugation method can increase the concentration of MNCs in fresh bone marrow by nearly a hundredfold and achieve immediate enrichment. In addition, acellular cartilage matrix (ACM), with good biocompatibility and a cartilage-specific microenvironment, is considered to be an ideal candidate scaffold for cartilage regeneration. In this study, hybrid pigs were used to establish articular cartilage defect models of different sizes to determine the feasibility and maximum scope of application of ACM-based biomimetic scaffolds combined with MNCs for inducing articular cartilage regeneration. Importantly, ACM-based biomimetic scaffolds instantly enriched MNCs could improve the repair effect of articular cartilage defects in situ, which established a new model of articular cartilage regeneration that could be applied immediately and suited for large-scale clinical promotion. The current study significantly improves the repair effect of articular cartilage defects, which provides scientific evidence and detailed insights for future clinical applications of ACM-based biomimetic scaffolds combined with MNCs.

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Explore the maximum scope of repairing articular cartilage defect with ACM scaffold.

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Immediate enrichment of mononuclear cells by density gradient centrifugation.

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ACM scaffold enriched MNCs improve the repair effect of articular cartilage defect.

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Enrichment of MNCs expands the maximum scope of repairing articular cartilage defect.

Cell-free fat extract attenuates osteoarthritis via chondrocytes regeneration and macrophages immunomodulation

Background

The prevalence of osteoarthritis (OA) is increasing, yet clinically effective and economical treatments are unavailable. We have previously proposed a cell-free fat extract (CEFFE) containing multiple cytokines, which possessed antiapoptotic, anti-oxidative, and proliferation promotion functions, as a “cell-free” strategy. In this study, we aimed to evaluate the therapeutic effect of CEFFE in vivo and in vitro.

Methods

In vivo study, sodium iodoacetate-induced OA rats were treated with CEFFE by intra-articular injections for 8 weeks. Behavioral experiments were performed every two weeks. Histological analyses, anti-type II collagen, and toluidine staining provided structural evaluation. Macrophage infiltration was assessed by anti-CD68 and anti-CD206 staining. In vitro study, the effect of CEFFE on macrophage polarization and secretory factors was evaluated by flow cytometry, immunofluorescence, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The effect of CEFFE on cartilage regeneration was accessed by cell counting kit-8 assay and qRT-PCR. The generation of reactive oxygen species (ROS) and levels of ROS-related enzymes were investigated by qRT-PCR and western blotting.

Results

In rat models with sodium iodoacetate (MIA)-induced OA, CEFFE increased claw retraction pressure while decreasing bipedal pressure in a dose-dependent manner. Moreover, CEFFE promoted cartilage structure restoration and increased the proportion of CD206⁺ macrophages in the synovium. In vitro, CEFFE decreased the proportion of CD86⁺ cells and reduced the expression of pro-inflammatory factors in LPS + IFN-γ induced Raw 264.7. In addition, CEFFE decreased the expression of interleukin-6 and ADAMTs-5 and promoted the expression of SOX-9 in mouse primary chondrocytes. Besides, CEFFE reduced the intracellular levels of reactive oxygen species in both in vitro models through regulating ROS-related enzymes.

Conclusions

CEFFE inhibits the progression of OA by promoting cartilage regeneration and limiting low-grade joint inflammation.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02813-3.