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

Clinical efficacy of cell-free fat extract and its effects on bone marrow edema in patients with early to mid-stage knee osteoarthritis: a clinical trial in comparison with hyaluronic acid

BACKGROUND

Previous studies have shown that hyaluronic acid can delay the progression of knee osteoarthritis. Existing research has extracted a bright red fluid called cell-free fat extract from human adipose tissue, which may play an important role in delaying the progression of osteoarthritis. By comparing with intra-articular injection of hyaluronic acid, this study aimed to evaluate the effects of intra-articular injection of CEFFE on both clinical efficacy and the reduction of bone marrow edema in patients with early to mid-stage knee osteoarthritis.

METHODS

A total of 48 patients with KOA (Kellgren-Lawrence grade II-III) symptoms were randomly divided into CEFFE group (24 cases) and HA group (24 cases). The patients in the CEFFE group received five injections of CEFFE (2 ml, 1 time/week), and the patients in the HA group received five injections of HA (2 ml, 1 ml/10 mg, 1 time/week). All the patients underwent clinical assessments using rating scales, including VAS, WOMAC and Lysholm Knee Score. These assessments were conducted at pre-treatment and at 3-week, 6-week, 3-month, and 6-month follow-up timepoints post-treatment. The clinical efficacy was evaluated at the 6-month follow-up after the treatment. The changes in subchondral bone marrow edema before and 6 months after treatment were assessed by grading BME on MRI of the affected knees.

RESULTS

A total of 52 knees from 46 patients were included in the final analysis. Comparison of VAS score, WOMAC score, and Lysholm score between the two groups revealed that the differences between pre-treatment and 3 weeks post-treatment were not statistically significant (P > 0.05). For the VAS score and WOMAC score at 6 weeks, 3 months, and 6 months post-treatment, the CEFFE group was lower than the HA group (P < 0.05). For the Lysholm score, the CEFFE group was higher than the HA group (P < 0.05). Compared with pre-treatment, VAS scores and WOMAC scores were lower and Lysholm scores were higher at all post-treatment time points (P < 0.05). At 6 months post-treatment, the clinical efficacy of the CEFFE group was significantly better than that of the HA group (P < 0.05). At 6 months post-treatment, MRI grading showed that subchondral BME was reduced to different degrees in both groups, with the reduction being more pronounced in the CEFFE group (P < 0.05).

CONCLUSION

This study demonstrated that intra-articular injection of CEFFE into the knee joint could enhance the durability of tissue-specific cells (especially chondrocytes) and improve cellular metabolic processes, preventing the continued progression of osteoarthritis. Both CEFFE and HA were found to improve clinical symptoms and reduced subchondral bone marrow edema in the treatment of early to mid-stage knee osteoarthritis. However, CEFFE was more effective than HA in achieving these outcomes.

Enhanced osteo-angiogenic coupling by a bioactive cell-free fat extract (CEFFE) delivered through electrospun fibers

Regeneration of functional bone tissue relies heavily on achieving adequate vascularization in engineered bone constructs following implantation. This process requires the close integration of osteogenesis and angiogenesis. Cell-free fat extract (CEFFE or FE), a recently emerging acellular fat extract containing abundant growth factors, holds significant potential for regulating osteo-angiogenic coupling and promoting regeneration of vascularized bone tissue. However, its specific role in modulating the coupling between angiogenesis and osteogenesis remains unclear. Our previous research demonstrated that FE-decorated electrospun fibers of polycaprolactone/gelatin (named FE-PDA@PCL/GT) exhibited pro-vasculogenic capabilities both in vitro and in vivo (D. Li, Q. Li, T. Xu, X. Guo, H. Tang, W. Wang, W. Zhang and Y. Zhang, Pro-vasculogenic fibers by PDA-mediated surface functionalization using cell-free fat extract (CEFFE), Biomacromolecules 2024, 25, 1550-1562). Herein, we firstly demonstrated that the FE-PDA@PCL/GT fibers also significantly stimulated osteogenesis in a mouse calvaria osteoblast-like cell line MC3T3-E1 cells, as evidenced by the increased production of alkaline phosphatase (ALP), mineral deposits, and collagen I, as well as the upregulated expression of osteogenic marker genes in the osteoblasts. Using a transwell co-culture system, we further demonstrated that the release of FE from the FE-PDA@PCL/GT fibers not only promoted osteogenesis and angiogenesis but also markedly enhanced the paracrine functions and reciprocal communications between endothelial cells and osteoblasts. This dynamic interaction played a key role in the observed enhancement of osteo-angiogenic coupling. With the confirmed pro-osteogenic and pro-angiogenic properties of FE-PDA@PCL/GT, it is envisaged that these newly engineered bioactive fibers can be used to develop highly biomimicking bone constructs. These constructs are designed to promote native-like cell-scaffold and cell-cell interactions, which are essential for the effective regeneration of defected bone tissue with adequate vasculature.

Recombinant human annexin A5 accelerates diabetic wounds healing by regulating skin inflammation

Background

One of the key obstacles to the healing of diabetic wound is the persistence of active inflammation. We previously demonstrated the potential of cell-free fat extract (CEFFE) to promote the healing of diabetic wounds, and annexin A5 (A5) is a crucial anti-inflammatory protein within CEFFE. This study aimed to evaluate the therapeutic potential of A5 in diabetic wounds.

Methods

A5 was loaded into GelMA hydrogels and applied to skin wounds of diabetic mice in vivo. The diabetic wounds with the treatment of GelMA-A5 were observed for 14 days and evaluated by histological analysis. Accessment of inflammation regulation were conducted through anti-CD68 staining, anti-CD86 and anti-CD206 staining, and qRT-PCR of wound tissue. In presence of A5, macrophages stimulated by lipopolysaccharide (LPS) in vitro, and detected through qRT-PCR, flow cytometry, and immunocytofluorescence staining. Besides, epithelial cells were co-cultured with A5 for epithelialization regulation by CCK-8 assay and cell migration assay.

Results

A5 could promote diabetic wound healing and regulate inflammations by promoting the transition of macrophages from M1 to M2 phenotype. In vitro experiments demonstrated that A5 exerted a significant effect on reducing pro-inflammatory factors and inhibiting the polarization of macrophages from M0 toward M1 phenotype. A5 significantly promoted the migration of epithelial cells.

Conclusion

Annexin A5 has a significant impact on the regulation of macrophage inflammation and promotion of epithelialization.

Cell-Free Fat Extract with Anti-melanogenic Property Improves the Appearance of Infraorbital Dark Circles: A Preliminary Clinical Study

BACKGROUND

The formation of infraorbital dark circles involves various factors including hyperpigmentation, skin aging and laxity. This study is to investigate whether cell-free fat extract (CEFFE) inhibits melanin synthesis and improves the appearance of infraorbital dark circles.

METHODS

Imaging systems analysed the melanin content in three groups of zebrafish embryos treated with 0 (CTRL), 100, and 200μg/mL of CEFFE. Eleven patients with infraorbital dark circles were enrolled and received intradermal injections of autologous CEFFE. Clinical trial assessments included subjective assessments (Global Aesthetic Improvement Scale and Likert satisfaction scale) and objective assessments (standard two-dimensional photographs, VISIA® photographs, and infraorbital skin colour measurement).

RESULTS

In the experiment of zebrafish embryos, the melanin content of CEFFE treatment was significantly reduced. In clinical trial, 72.73% of patients considered CEFFE treatment for infraorbital dark circles to be effective, and more than half of the patients were satisfied with the treatment. In the evaluation of skin colour at the inner, middle, and outer edges of the infraorbital dark circles, there was a gradual improvement in infraorbital skin colour after each treatment and at the 3-month follow-up, with a statistically significant improvement in skin colour on the outer edge of the infraorbital dark circles (p < 0.05). Simultaneously, we observed a reduction in periocular wrinkles, with a significant difference at the 3-month follow-up (p < 0.05). The events observed included bruising, erythema, and oedema, which resolved spontaneously.

CONCLUSION

Our study demonstrated that CEFFE inhibits melanogenesis and is a safe and effective treatment for infraorbital dark circles.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Sodium alginate hydrogels co-encapsulated with cell free fat extract-loaded core-shell nanofibers and menstrual blood stem cells derived exosomes for acceleration of articular cartilage regeneration

This study presents a novel scaffold system comprising sodium alginate hydrogels (SAh) co-encapsulated with cell-free fat extract (CEFFE)-loaded core-shell nanofibers (NFs) and menstrual blood stem cell-derived exosomes (EXOs). The scaffold integrates the regenerative potential of EXOs and CFFFE, offering a multifaceted strategy for promoting articular cartilage repair. Coaxially electrospun core-shell NFs exhibited successful encapsulation of CEFFE and seamless integration into the SAh matrix. Structural modifications induced by the incorporation of CEFFE-NFs enhanced hydrogel porosity, mechanical strength, and degradation kinetics, facilitating cell adhesion, proliferation, and tissue ingrowth. The release kinetics of growth factors from the composite scaffold demonstrated sustained and controlled release profiles, essential for optimal tissue regeneration. In vitro studies revealed high cell viability, enhanced chondrocyte proliferation, and migration in the presence of EXOs/CEFFE-NFs@SAh composite scaffolds. Additionally, in vivo experiments demonstrated significant cartilage regeneration, with the composite scaffold outperforming controls in promoting hyaline cartilage formation and defect bridging. Overall, this study underscores the potential of EXOs and CEFFE-NFs integrated into SAh matrices for enhancing chondrocyte viability, proliferation, migration, and ultimately, articular cartilage regeneration. Future research directions may focus on elucidating underlying mechanisms and conducting long-term in vivo studies to validate clinical applicability and scalability.

Enhancing high-quality fat survival: A novel strategy using cell-free fat extract

High-quality fat (HQF) improves the survival rate of fat and volumetric filling compared to traditional Coleman fat. However, this HQF strategy inevitably leads to a significant amount of unused fat being wasted. "CEFFE" (cell-free fat extract) is an acellular aqueous-phase liquid, rich in bioactive proteins. The remaining fat from preparing HQF can be further processed into CEFFE to promote the survival of HQF. HQF was obtained and the remaining fat was processed into CEFFE, then HQF was transplanted subcutaneously in nude mice. Animal studies showed that CEFFE significantly improved the survival rate of HQF. Histological analysis revealed that CEFFE improved the survival rate of HQF, by enhancing cell proliferation activity, reducing apoptosis, increasing angiogenesis, and improving the inflammatory state. Under simulated anaerobic conditions, CEFFE also improved the viability of HQF. In vitro, studies demonstrated that CEFFE enhanced the survival rate of HQF through multiple mechanisms. Transcriptomic analysis and qPCR showed that CEFFE increased the expression of angiogenesis-related genes in ADSCs while enhancing their proliferation-related gene expression and suppressing the expression of three differentiation-related genes. Moreover, functional experiments demonstrated that CEFFE-induced ADSCs exhibited stronger proliferation and adipogenic differentiation abilities. Tube formation and migration assays revealed that CEFFE promoted tube formation and migration of HUVECs, indicating its inherent pro-angiogenic properties. CEFFE facilitated the development of M0 to M2 macrophages, suggesting its role in improving the inflammatory state. This innovative clinical strategy optimizes HQF transplantation strategy, minimizing fat wastage and enhancing the efficiency of fat utilization.

Annexin A5 Derived from Cell-free Fat Extract Attenuates Osteoarthritis via Macrophage Regulation

Osteoarthritis (OA) is a challenging degenerative joint disease to manage. Previous research has indicated that cell-free fat extract (CEFFE) may hold potential for OA treatment. This study investigated the role of Annexin A5 (AnxA5) within CEFFE in regulating macrophage polarization and protecting chondrocytes. In vitro experiments demonstrated that AnxA5 effectively inhibited M1 macrophage polarization by facilitating toll-like receptor (TLR) 4 internalization and lysosomal degradation through calcium-dependent endocytosis. This process decreased TLR4 expression, suppressed pro-inflammatory mediator release, and reduced the production of reactive oxygen species. Furthermore, AnxA5 displayed protective effects against chondrocyte necrosis and apoptosis. In vivo, studies revealed that intra-articular administration of AnxA5 ameliorated pain symptoms in a monosodium iodoacetate-induced osteoarthritis rat model. Histological analyses indicated a decrease in synovial inflammation and mitigation of cartilage damage following AnxA5 treatment. These results underscored the potential of AnxA5 as a therapeutic option for OA due to its capacity to regulate macrophage polarization and maintain chondrocyte viability. Further investigation into the specific mechanisms and clinical applications of AnxA5 may help improve the management of OA.

3D printing of Ceffe-infused scaffolds for tailored nipple-like cartilage development

The reconstruction of a stable, nipple-shaped cartilage graft that precisely matches the natural nipple in shape and size on the contralateral side is a clinical challenge. While 3D printing technology can efficiently and accurately manufacture customized complex structures, it faces limitations due to inadequate blood supply, which hampers the stability of nipple-shaped cartilage grafts produced using this technology. To address this issue, we employed a biodegradable biomaterial, Poly(lactic-co-glycolic acid) (PLGA), loaded with Cell-Free Fat Extract (Ceffe). Ceffe has demonstrated the ability to promote angiogenesis and cell proliferation, making it an ideal bio-ink for bioprinting precise nipple-shaped cartilage grafts. We utilized the Ceffe/PLGA scaffold to create a porous structure with a precise nipple shape. This scaffold exhibited favorable porosity and pore size, ensuring stable shape maintenance and satisfactory biomechanical properties. Importantly, it could release Ceffe in a sustained manner. Our in vitro results confirmed the scaffold's good biocompatibility and its ability to promote angiogenesis, as evidenced by supporting chondrocyte proliferation and endothelial cell migration and tube formation. Furthermore, after 8 weeks of in vivo culture, the Ceffe/PLGA scaffold seeded with chondrocytes regenerated into a cartilage support structure with a precise nipple shape. Compared to the pure PLGA group, the Ceffe/PLGA scaffold showed remarkable vascular formation, highlighting the beneficial effects of Ceffe. These findings suggest that our designed Ceffe/PLGA scaffold with a nipple shape represents a promising strategy for precise nipple-shaped cartilage regeneration, laying a foundation for subsequent nipple reconstruction.

Pro-vasculogenic Fibers by PDA-Mediated Surface Functionalization Using Cell-Free Fat Extract (CEFFE)

Formation of adequate vascular network within engineered three-dimensional (3D) tissue substitutes postimplantation remains a major challenge for the success of biomaterials-based tissue regeneration. To better mimic the in vivo angiogenic and vasculogenic processes, nowadays increasing attention is given to the strategy of functionalizing biomaterial scaffolds with multiple bioactive agents. Aimed at engineering electrospun biomimicking fibers with pro-vasculogenic capability, this study was proposed to functionalize electrospun fibers of polycaprolactone/gelatin (PCL/GT) by cell-free fat extract (CEFFE or FE), a newly emerging natural "cocktail" of cytokines and growth factors extracted from human adipose tissue. This was achieved by having the electrospun PCL/GT fiber surface coated with polydopamine (PDA) followed by PDA-mediated immobilization of FE to generate the pro-vasculogenic fibers of FE-PDA@PCL/GT. It was found that the PDA-coated fibrous mat of PCL/GT exhibited a high FE-loading efficiency (∼90%) and enabled the FE to be released in a highly sustained manner. The engineered FE-PDA@PCL/GT fibers possess improved cytocompatibility, as evidenced by the enhanced cellular proliferation, migration, and RNA and protein expressions (e.g., CD31, vWF, VE-cadherin) in the human umbilical vein endothelial cells (huvECs) used. Most importantly, the FE-PDA@PCL/GT fibrous scaffolds were found to enormously stimulate tube formation in vitro, microvascular development in the in ovo chick chorioallantoic membrane (CAM) assay, and vascularization of 3D construct in a rat subcutaneous embedding model. This study highlights the potential of currently engineered pro-vasculogenic fibers as a versatile platform for engineering vascularized biomaterial constructs for functional tissue regeneration.

Cell-free fat extract promotes axon regeneration and retinal ganglion cells survival in traumatic optic neuropathy

Injuries to axons within the central nervous system (CNS) pose a substantial clinical challenge due to their limited regenerative capacity. This study investigates the therapeutic potential of Cell-free fat extract (CEFFE) in CNS injury. CEFFE was injected intravitreally after the optic nerve was crushed. Two weeks post-injury, quantification of regenerated axons and survival rates of retinal ganglion cells (RGCs) were performed. Subsequently, comprehensive gene ontology (GO) an-notation elucidated the cellular origins and functional attributes of CEFFE components. Molecular mechanisms underlying CEFFE's therapeutic effects were explored through Western blotting (WB). Additionally, levels of inflammatory factors within CEFFE were determined using enzyme-linked immunosorbent assay (ELISA), and histological staining of microglia was conducted to assess its impact on neuroinflammation. CEFFE demonstrated a significant capacity to promote axon re-generation and enhance RGCs survival. GO annotation revealed the involvement of 146 proteins within CEFFE in axonogenesis and neurogenesis. WB analysis unveiled the multifaceted pathways through which CEFFE exerts its therapeutic effects. Elevated levels of inflammatory factors were detected through ELISA, and CEFFE exhibited a modulatory effect on microglial activation in the retinal tissue following optic nerve crush (ONC). The present study highlights the therapeutic promise of CEFFE in the management of CNS injuries, exemplified by its ability to foster axon regeneration and improve RGCs survival.

Cell-free fat extract restores hair loss: a novel therapeutic strategy for androgenetic alopecia

BACKGROUND

Androgenetic alopecia (AGA) is one of the most common hair loss diseases worldwide. However, current treatments including medicine, surgery, and stem cells are limited for various reasons. Cell-free fat extract (CEFFE), contains various cell factors, may have potential abilities in treating AGA. This study aims to evaluate the safety, effectiveness and the underlying mechanism of CEFFE in treating AGA.

METHODS

Sex hormone evaluation, immunogenicity assay and genotoxicity assay were conducted for CEFFE. In vivo study, male C57BL/6 mice were injected subcutaneously with dihydrotestosterone (DHT) and were treated with different concentration of CEFFE for 18 days (five groups and n = 12 in each group: Control, Model, CEFFELow, CEFFEMiddle, CEFFEHigh). Anagen entry rate and hair coverage percentage were analyzed through continuously taken gross photographs. The angiogenesis and proliferation of hair follicle cells were evaluated by hematoxylin-eosin, anti-CD31, and anti-Ki67 staining. In vitro study, dermal papilla cells (DPCs) were incubated with different concentrations of CEFFE, DHT, or CEFFE + DHT, followed by CCK-8 assay and flow cytometry to evaluate cell proliferation cycle and apoptosis. The intracellular DHT level were assessed by enzyme-linked immunosorbent assay. The expression of 5α-reductase type II, 3α-hydroxysteroid dehydrogenase and androgen receptor were assessed through reverse transcription-quantitative polymerase chain reaction (RT-qPCR) or/and western blot.

RESULTS

In CEFFE-treated mice, an increase in the anagen entry rate and hair coverage percentage was observed. The number of CD31-positive capillaries and Ki67-positive cells were increased, suggesting that CEFFE promoted the proliferation of DPCs, modulated the cell cycle arrest, inhibited apoptosis caused by DHT, reduced the intracellular concentration of DHT in DPCs, and downregulated the expression of AR.

CONCLUSIONS

CEFFE is a novel and effective treatment option for AGA through producing an increased hair follicle density and hair growth rate. The proposed mechanisms are through the DHT/AR pathway regulation and regional angiogenesis ability.

Lipoaspirate fluid derived factors and extracellular vesicles accelerate wound healing in a rat burn model

Background: The regenerative capabilities of derivatives derived from the fat layer of lipoaspirate have been demonstrated. However, the large volume of lipoaspirate fluid has not attracted extensive attention in clinical applications. In this study, we aimed to isolate the factors and extracellular vesicles from human lipoaspirate fluid and evaluate their potential therapeutic efficacy. Methods: Lipoaspirate fluid derived factors and extracellular vesicles (LF-FVs) were prepared from human lipoaspirate and characterized by nanoparticle tracking analysis, size-exclusion chromatography and adipokine antibody arrays. The therapeutic potential of LF-FVs was evaluated on fibroblasts in vitro and rat burn model in vivo. Wound healing process was recorded on days 2, 4, 8, 10, 12 and 16 post-treatment. The scar formation was analyzed by histology, immunofluorescent staining and scar-related gene expression at day 35 post-treatment. Results: The results of nanoparticle tracking analysis and size-exclusion chromatography indicated that LF-FVs were enriched with proteins and extracellular vesicles. Specific adipokines (adiponectin and IGF-1) were detected in LF-FVs. In vitro, LF-FVs augmented the proliferation and migration of fibroblasts in a dose-dependent manner. In vivo, the results showed that LF-FVs significantly accelerated burn wound healing. Moreover, LF-FVs improved the quality of wound healing, including regenerating cutaneous appendages (hair follicles and sebaceous glands) and decreasing scar formation in the healed skin. Conclusion: LF-FVs were successfully prepared from lipoaspirate liquid, which were cell-free and enriched with extracellular vesicles. Additionally, they were found to improve wound healing in a rat burn model, suggesting that LF-FVs could be potentially used for wound regeneration in clinical settings.

Metabolic Mechanisms and Potential Therapeutic Targets for Prevention of Ovarian Aging: Data from Up-to-Date Experimental Studies

Female infertility and reproduction is an ongoing and rising healthcare issue, resulting in delaying the decision to start a family. Therefore, in this review, we examine potential novel metabolic mechanisms involved in ovarian aging according to recent data and how these mechanisms may be addressed through new potential medical treatments. We examine novel medical treatments currently available based mostly on experimental stem cell procedures as well as caloric restriction (CR), hyperbaric oxygen treatment and mitochondrial transfer. Understanding the connection between metabolic and reproductive pathways has the potential to offer a significant scientific breakthrough in preventing ovarian aging and prolonging female fertility. Overall, the field of ovarian aging is an emerging field that may expand the female fertility window and perhaps even reduce the need for artificial reproductive techniques.

Bioactive Injectable and Self-Healing Hydrogel Via Cell-Free Fat Extract for Endometrial Regeneration

The damaged endometrium and the formation of fibrosis are key barriers to pregnancy and further lead to infertility. However, how to promote endometrium repair is always a challenge. Here, a bioactive injectable and self-healing hydrogel is developed by physically combination of thiolated polyethylene (PEG), Cu²⁺ and cell-free fat extract (CEFFE, CF) for endometrial regeneration and fertility. By inheriting the advantages of various active proteins contained in CEFFE, it could induce the overall repair of endometrial microenvironment for intrauterine adhesion (IUA). In vitro, CF@Cu-PEG reduces endometrial cell apoptosis by more than 50%, and increases angiogenesis by 92.8%. In the IUA mouse, injection of CF@Cu-PEG significantly reduces the rate of uterine hydrometra and prevents the formation of endometrial fibrosis. Remarkably, CF@Cu-PEG contributes to the repair of endometrial microstructure, especially increases the number of endometrial pinopodes, significantly improves endometrial receptivity, and increases the pregnancy rate of IUA mice from 7.14% to 66.67%. In summary, through the physically combination of CEFFE and Cu-PEG, the construction of loaded bioactive injectable hydrogel not only inhibits the IUA, but also induces the self-repair of endometrial cells in situ and improves fertility, providing a new strategy for IUA repair in clinical application.

Targeting macrophage polarization as a promising therapeutic strategy for the treatment of osteoarthritis

Osteoarthritis (OA) is a chronic osteoarthropathy characterized by the progressive degeneration of articular cartilage and synovial inflammation. Early OA clinical treatments involve intra-articular injection of glucocorticoids, oral acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs), which are used for anti-inflammation and pain relief. However, long-term use of these agents will lead to inevitable side effects, even aggravate cartilage loss. At present, there are no disease-modifying OA drugs (DMOADs) yet approved by regulatory agencies. Polarization regulation of synovial macrophages is a new target for OA treatment. Inhibiting M1 polarization and promoting M2 polarization of synovial macrophages can alleviate synovial inflammation, relieve joint pain and inhibit articular cartilage degradation, which is a promising strategy for OA treatment. In this study, we describe the molecular mechanisms of macrophage polarization and its key role in the development of OA. Subsequently, we summarize the latest progress of strategies for OA treatment through macrophage reprogramming, including small molecule compounds (conventional western medicine and synthetic compounds, monomer compounds of traditional Chinese medicine), biomacromolecules, metal/metal oxides, cells, and cell derivatives, and interprets the molecular mechanisms, hoping to provide some information for DMOADs development.

Regeneration of articular cartilage defects: Therapeutic strategies and perspectives

Articular cartilage (AC), a bone-to-bone protective device made of up to 80% water and populated by only one cell type (i.e. chondrocyte), has limited capacity for regeneration and self-repair after being damaged because of its low cell density, alymphatic and avascular nature. Resulting repair of cartilage defects, such as osteoarthritis (OA), is highly challenging in clinical treatment. Fortunately, the development of tissue engineering provides a promising method for growing cells in cartilage regeneration and repair by using hydrogels or the porous scaffolds. In this paper, we review the therapeutic strategies for AC defects, including current treatment methods, engineering/regenerative strategies, recent advances in biomaterials, and present emphasize on the perspectives of gene regulation and therapy of noncoding RNAs (ncRNAs), such as circular RNA (circRNA) and microRNA (miRNA).

Nrf2-mediated anti-inflammatory polarization of macrophages as therapeutic targets for osteoarthritis

Macrophages are the most abundant immune cells within the synovial joints, and also the main innate immune effector cells triggering the initial inflammatory responses in the pathological process of osteoarthritis (OA). The transition of synovial macrophages between pro-inflammatory and anti-inflammatory phenotypes can play a key role in building the intra-articular microenvironment. The pro-inflammatory cascade induced by TNF-α, IL-1β, and IL-6 is closely related to M1 macrophages, resulting in the production of pro-chondrolytic mediators. However, IL-10, IL1RA, CCL-18, IGF, and TGF are closely related to M2 macrophages, leading to the protection of cartilage and the promoted regeneration. The inhibition of NF-κB signaling pathway is central in OA treatment via controlling inflammatory responses in macrophages, while the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway appears not to attract widespread attention in the field. Nrf2 is a transcription factor encoding a large number of antioxidant enzymes. The activation of Nrf2 can have antioxidant and anti-inflammatory effects, which can also have complex crosstalk with NF-κB signaling pathway. The activation of Nrf2 can inhibit the M1 polarization and promote the M2 polarization through potential signaling transductions including TGF-β/SMAD, TLR/NF-κB, and JAK/STAT signaling pathways, with the regulation or cooperation of Notch, NLRP3, PI3K/Akt, and MAPK signaling. And the expression of heme oxygenase-1 (HO-1) and the negative regulation of Nrf2 for NF-κB can be the main mechanisms for promotion. Furthermore, the candidates of OA treatment by activating Nrf2 to promote M2 phenotype macrophages in OA are also reviewed in this work, such as itaconate and fumarate derivatives, curcumin, quercetin, melatonin, mesenchymal stem cells, and low-intensity pulsed ultrasound.