Macrophages promote cartilage regeneration in a time- and phenotype-dependent manner

Small Joint Organoids 3D Bioprinting: Construction Strategy and Application

Osteoarthritis (OA) is a chronic disease that causes pain and disability in adults, affecting ≈300 million people worldwide. It is caused by damage to cartilage, including cellular inflammation and destruction of the extracellular matrix (ECM), leading to limited self-repairing ability due to the lack of blood vessels and nerves in the cartilage tissue. Organoid technology has emerged as a promising approach for cartilage repair, but constructing joint organoids with their complex structures and special mechanisms is still challenging. To overcome these boundaries, 3D bioprinting technology allows for the precise design of physiologically relevant joint organoids, including shape, structure, mechanical properties, cellular arrangement, and biological cues to mimic natural joint tissue. In this review, the authors will introduce the biological structure of joint tissues, summarize key procedures in 3D bioprinting for cartilage repair, and propose strategies for constructing joint organoids using 3D bioprinting. The authors also discuss the challenges of using joint organoids' approaches and perspectives on their future applications, opening opportunities to model joint tissues and response to joint disease treatment.

Empowering Cartilage Restructuring with Biodegradable Magnesium Doped-Silicon Based-Nanoplatforms: Sustained Delivery and Enhanced Differentiation Potential

Background

Cartilage-related diseases, such as hypoplastic chondrodysplasia a rare genetic disorder that affects newborns, causing abnormal cartilage development and restricted skeletal growth. However, the development of effective treatment strategies for chondrodysplasia still faces significant challenges due to limitations in the controlled drug delivery, biocompatibility, and biodegradability of nanomedicines.

Methods

A biodegradable magnesium doped-silicon based-nanoplatforms based on silicon nanoparticles (MON) was constructed. Briefly, the MON was modified with sulfhydryl groups using MPTMS to form MOS. Further engineering of MOS was achieved by incorporating Mg2+ ions through the "dissolution-regrowth" method, resulting in MMOS. Ica was effectively loaded into the MMOS channels, and HA was anchored on the surface of MOS to obtain MMOS-Ica@HA nanoplatforms. Additionally, in vitro cell experiments and in vivo zebrafish embryo models were used to evaluate the effect of the nanoplatforms on cartilage differentiation or formation and the efficiency of treating chondrodysplasia.

Results

A series of characterization tests including TEM, SEM, DLS, XPS, EDX, and BET analysis validate the successful preparation of MOS-Ica@HA nanoplatforms. The prepared nanoplatforms show excellent dispersion and controllable drug release behavior. The cytotoxicity evaluation reveals the good biocompatibility of MOS-Ica@HA due to the sustained and controllable release of Ica. Importantly, the presence of Ica and Mg component in MOS-Ica@HA significantly promote chondrogenic differentiation of BMSCs via the Smad5/HIF-1α signaling pathway. In vitro and in vivo experiments confirmed that the nanoplatforms improved chondrodysplasia by promoting cartilage differentiation and formation.

Conclusion

The findings suggest the potential application of the developed biodegradable MMOS-Ica@HA nanoplatforms with acceptable drug loading capacity and controlled drug release in chondrodysplasia treatment, which indicates a promising approach for the treatment of chondrodysplasia.

Exosomes from M2c macrophages alleviate intervertebral disc degeneration by promoting synthesis of the extracellular matrix via MiR-124/CILP/TGF-β

Immuno-inflammation is highly associated with anabolic and catabolic dysregulation of the extracellular matrix (ECM) in the nucleus pulposus (NP), which dramatically propels intervertebral disc degeneration (IVDD). With the characteristics of tissue remodeling and regeneration, M2c macrophages have attracted great attention in research on immune modulation that rebuilds degenerated tissues. Therefore, we first demonstrated the facilitating effects of M2c macrophages on ECM anabolism of the NP in vitro. We subsequently found that exosomes from M2c macrophages (M2c-Exoss) mediated their metabolic rebalancing effects on the ECM. To determine whether M2c-Exoss served as positive agents protecting the ECM in IVDD, we constructed an M2c-Exos-loaded hyaluronic acid hydrogel (M2c-Exos@HA hydrogel) and implanted it into the degenerated caudal disc of rats. The results of MRI and histological staining indicated that the M2c-Exos@HA hydrogel alleviated IVDD in vivo in the long term. To elucidate the underlying molecular mechanism, we performed 4D label-free proteomics to screen dysregulated proteins in NPs treated with M2c-Exoss. Cartilage intermediate layer protein (CILP) was the key protein responsible for the rebalancing effects of M2c-Exoss on ECM metabolism in the NP. With prediction and verification using luciferase assays and rescue experiments, miR-124-3p was identified as the upstream regulator in M2c-Exoss that regulated CILP and consequently enhanced the activity of the TGF-β/smad3 pathway. In conclusion, we demonstrated ameliorating effects of M2c-Exoss on the imbalance of ECM metabolism in IVDD via the miR-124/CILP/TGF-β regulatory axis, which provides a promising theoretical basis for the application of M2c macrophages and their exosomes in the treatment of IVDD.

Targeting different phenotypes of macrophages: A potential strategy for natural products to treat inflammatory bone and joint diseases

BACKGROUND

Macrophages, a key class of immune cells, have a dual role in inflammatory responses, switching between anti-inflammatory M2 and pro-inflammatory M1 subtypes depending on the specific environment. Greater numbers of M1 macrophages correlate with increased production of inflammatory chemicals, decreased osteogenic potential, and eventually bone and joint disorders. Therefore, reversing M1 macrophages polarization is advantageous for lowering inflammatory factors. To better treat inflammatory bone disorders in the future, it may be helpful to gain insight into the specific mechanisms and natural products that modulate macrophage polarization.

OBJECTIVE

This review examines the impact of programmed cell death and different cells in the bone microenvironment on macrophage polarization, as well as the effects of natural products on the various phenotypes of macrophages, in order to suggest some possibilities for the treatment of inflammatory osteoarthritic disorders.

METHODS

Using 'macrophage polarization,' 'M1 macrophage' 'M2 macrophage' 'osteoporosis,' 'osteonecrosis of femoral head,' 'osteolysis,' 'gouty arthritis,' 'collagen-induced arthritis,' 'freund's adjuvant-induced arthritis,' 'adjuvant arthritis,' and 'rheumatoid arthritis' as search terms, the relevant literature was searched using the PubMed, the Cochrane Library and Web of Science databases.

RESULTS

Targeting macrophages through different signaling pathways has become a key mechanism for the treatment of inflammatory bone and joint diseases, including HIF-1α, NF-κB, AKT/mTOR, JAK1/2-STAT1, NF-κB, JNK, ERK, p-38α/β, p38/MAPK, PI3K/AKT, AMPK, AMPK/Sirt1, STAT TLR4/NF-κB, TLR4/NLRP3, NAMPT pathway, as well as the programmed cell death autophagy, pyroptosis and ERS.

CONCLUSION

As a result of a search of databases, we have summarized the available experimental and clinical evidence supporting herbal products as potential treatment agents for inflammatory osteoarthropathy. In this paper, we outline the various modulatory effects of natural substances targeting macrophages in various diseases, which may provide insight into drug options and directions for future clinical trials. In spite of this, more mechanistic studies on natural substances, as well as pharmacological, toxicological, and clinical studies are required.

Could hypoxia rehabilitate the osteochondral diseased interface? Lessons from the interplay of hypoxia and purinergic signals elsewhere

The osteochondral unit comprises the articular cartilage (90%), subchondral bone (5%) and calcified cartilage (5%). All cells present at the osteochondral unit that is ultimately responsible for matrix production and osteochondral homeostasis, such as chondrocytes, osteoblasts, osteoclasts and osteocytes, can release adenine and/or uracil nucleotides to the local microenvironment. Nucleotides are released by these cells either constitutively or upon plasma membrane damage, mechanical stress or hypoxia conditions. Once in the extracellular space, endogenously released nucleotides can activate membrane-bound purinoceptors. Activation of these receptors is fine-tuning regulated by nucleotides' breakdown by enzymes of the ecto-nucleotidase cascade. Depending on the pathophysiological conditions, both the avascular cartilage and the subchondral bone subsist to significant changes in oxygen tension, which has a tremendous impact on tissue homeostasis. Cell stress due to hypoxic conditions directly influences the expression and activity of several purinergic signalling players, namely nucleotide release channels (e.g. Cx43), NTPDase enzymes and purinoceptors. This review gathers experimental evidence concerning the interplay between hypoxia and the purinergic signalling cascade contributing to osteochondral unit homeostasis. Reporting deviations to this relationship resulting from pathological alterations of articular joints may ultimately unravel novel therapeutic targets for osteochondral rehabilitation. At this point, one can only hypothesize how hypoxia mimetic conditions can be beneficial to the ex vivo expansion and differentiation of osteo- and chondro-progenitors for auto-transplantation and tissue regenerative purposes.

A guide to preclinical evaluation of hydrogel-based devices for treatment of cartilage lesions

The drive to develop cartilage implants for the treatment of major defects in the musculoskeletal system has resulted in a major research thrust towards developing biomaterial devices for cartilage repair. Investigational devices for the restoration of articular cartilage are considered as significant risk materials by regulatory bodies and therefore proof of efficacy and safety prior to clinical testing represents a critical phase of the multidisciplinary effort to bridge the gap between bench and bedside. To date, review articles have thoroughly covered different scientific facets of cartilage engineering paradigm, but surprisingly, little attention has been given to the preclinical considerations revolving around the validation of a biomaterial implant. Considering hydrogel-based cartilage products as an example, the present review endeavors to provide a summary of the critical prerequisites that such devices should meet for cartilage repair, for successful implantation and subsequent preclinical validation prior to clinical trials. Considerations pertaining to the choice of appropriate animal model, characterization techniques for the quantitative and qualitative outcome measures, as well as concerns with respect to GLP practices are also extensively discussed. This article is not meant to provide a systematic review, but rather to introduce a device validation-based roadmap to the academic investigator, in anticipation of future healthcare commercialization. STATEMENT OF SIGNIFICANCE: There are significant challenges around translation of in vitro cartilage repair strategies to approved therapies. New biomaterial-based devices must undergo exhaustive investigations to ensure their safety and efficacy prior to clinical trials. These considerations are required to be applied from early developmental stages. Although there are numerous research works on cartilage devices and their in vivo evaluations, little attention has been given into the preclinical pathway and the corresponding approval processes. With a focus on hydrogel devices to concretely illustrate the preclinical path, this review paper intends to highlight the various considerations regarding the preclinical validation of hydrogel devices for cartilage repair, from regulatory considerations, to implantation strategies, device performance aspects and characterizations.