Salinomycin causes dedifferentiation via the extracellular signal-regulated kinase (ERK) pathway in rabbit articular chondrocytes

The Nrf2/HO-1 pathway participates in the antiapoptotic and anti-inflammatory effects of platelet-rich plasma in the treatment of osteoarthritis

INTRODUCTION

We aimed to explore the molecular mechanisms through which platelet-rich plasma (PRP) attenuates osteoarthritis (OA)-induced pain, apoptosis, and inflammation.

METHODS

An in vivo model of OA was established by injuring rats using the anterior cruciate ligament transection method, whereas an in vitro model was generated by exposing chondrocytes to interleukin (IL)-1β. Both models were then treated with PRP.

RESULTS

In both the in vivo and in vitro models, OA led to the suppression of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway, whereas treatment with PRP reactivated this molecular axis. Inhibition of the Nrf2/HO-1 pathway using the Nrf2 inhibitor brusatol or through Nrf2 gene silencing counteracted the effects of PRP in reducing the tenderness and thermal pain thresholds of OA rats. Additionally, PRP reduced the mRNA expression of IL-1β, IL-6, tumor necrosis factor-alpha (TNF-α), and matrix metallopeptidase 13 (MMP-13) and the protein expression of B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X-protein (Bax), and caspase-3. Furthermore, inflammation and apoptosis were induced by brusatol treatment or Nrf2 silencing. Additionally, in the in vitro model, PRP treatment increased the proliferation of chondrocytes and attenuated their inflammatory response and apoptosis, effects that were abrogated by Nrf2 depletion.

CONCLUSIONS

The Nrf2/HO-1 pathway participates in the PRP-mediated attenuation of OA development by suppressing inflammation and apoptosis.

Effects of an Adipose Mesenchymal Stem Cell-Derived Conditioned medium and TGF-β1 on Human Keratinocytes In Vitro

Human keratinocytes play a crucial role during skin wound healing and in skin replacement therapies. The secretome of adipose-derived stem cells (ASCs) has been shown to secrete pro-healing factors, among which include TGF-β1, which is essential for keratinocyte migration and the re-epithelialization of cutaneous wounds during skin wound healing. The benefits of an ASC conditioned medium (ASC-CM) are primarily orchestrated by trophic factors that mediate autocrine and paracrine effects in keratinocytes. Here, we evaluated the composition and the innate characteristics of the ASC secretome and its biological effects on keratinocyte maturation and wound healing in vitro. In particular, we detected high levels of different growth factors, such as HGF, FGFb, and VEGF, and other factors, such as TIMP1 and 4, IL8, PAI-1, uPA, and IGFBP-3, in the ASC-CM. Further, we investigated, using immunofluorescence and flow cytometry, the distinct effects of a human ASC-CM and/or synthetic TGF-β1 on human keratinocyte proliferation, migration, and cell apoptosis suppression. We demonstrated that the ASC-CM increased keratinocyte proliferation as compared to TGF-β1 treatment. Further, we found that the ASC-CM exerted cell cycle progression in keratinocytes via regulating the phases G1, S, and G2/M. In particular, cells subjected to the ASC-CM demonstrated increased DNA synthesis (S phase) compared to the TGF-β1-treated KCs, which showed a pronounced G0/G1 phase. Furthermore, both the ASC-CM and TGF-β1 conditions resulted in a decreased expression of the late differentiation marker CK10 in human keratinocytes in vitro, whereas both treatments enhanced transglutaminase 3 and loricrin expression. Interestingly, the ASC-CM promoted significantly increased numbers of keratinocytes expressing epidermal basal keratinocyte markers, such DLL1 and Jagged2 Notch ligands, whereas those ligands were significantly decreased in TGF-β1-treated keratinocytes. In conclusion, our findings suggest that the ASC-CM is a potent stimulator of human keratinocyte proliferation in vitro, particularly supporting basal keratinocytes, which are crucial for a successful skin coverage after transplantation. In contrast, TGF-β1 treatment decreased keratinocyte proliferation and specifically increased the expression of differentiation markers in vitro.

Salinomycin alleviates osteoarthritis progression via inhibiting Wnt/β-catenin signaling

Osteoarthritis (OA) is the most prevalent degenerative whole-joint disease characterized by cartilage degeneration, synovial hyperplasia, osteophyte formation, and subchondral bone sclerosis. Currently there are no disease-modifying treatments available for OA because its etiology and pathogenesis are largely unknown. Here we report that a natural carboxylic polyether ionophore that is used as an anti-tumor drug, salinomycin (SAL), may be a promising therapeutic drug for OA in the future. We found that SAL showed no cytotoxicity on mouse chondrocytes and displayed a protective effect against interleukin-1β (IL-1β), in cultured mouse chondrocytes and cartilage explants. Treatment with low SAL concentrations directly upregulated the anabolism factors collagen II and aggrecan, while it inhibited the catabolic factors matrix metalloproteinase-13 (MMP13) and metalloproteinase with thrombospondin motifs-5 (ADAMTS5) to protect against extracellular matrix (ECM) degradation, and also suppressed inflammatory responses in mouse chondrocytes. Furthermore, SAL reduced the severity of OA-associated changes and delayed cartilage destruction, subchondral bone sclerosis, and osteophyte formation in a destabilized medial meniscus (DMM) surgery-induced mouse OA model. Mechanistically, a low SAL concentration induced anabolism and inhibited catabolism in chondrocytes via inhibiting Lrp6 phosphorylation and Wnt/β-catenin signaling. Our results suggested that SAL may serve as a potential disease-modifying therapeutic against OA pathogenesis.

Highly Organized Porous Gelatin-Based Scaffold by Microfluidic 3D-Foaming Technology and Dynamic Culture for Cartilage Tissue Engineering

A gelatin-based hydrogel scaffold with highly uniform pore size and biocompatibility was fabricated for cartilage tissue engineering using microfluidic 3D-foaming technology. Mainly, bubbles with different diameters, such as 100 μm and 160 μm, were produced by introducing an optimized nitrogen gas and gelatin solution at an optimized flow rate, and N₂/gelatin bubbles were formed. Furthermore, a cross-linking agent (1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide, EDC) was employed for the cross-linking reaction of the gelatin-based hydrogel scaffold with uniform bubbles, and then the interface between the close cells were broken by degassing. The pore uniformity of the gelatin-based hydrogel scaffolds was confirmed by use of a bright field microscope, conjugate focus microscope and scanning electron microscope. The in vitro degradation rate, mechanical properties, and swelling rate of gelatin-based hydrogel scaffolds with highly uniform pore size were studied. Rabbit knee cartilage was cultured, and its extracellular matrix content was analyzed. Histological analysis and immunofluorescence staining were employed to confirm the activity of the rabbit knee chondrocytes. The chondrocytes were seeded into the resulting 3D porous gelatin-based hydrogel scaffolds. The growth conditions of the chondrocyte culture on the resulting 3D porous gelatin-based hydrogel scaffolds were evaluated by MTT analysis, live/dead cell activity analysis, and extracellular matrix content analysis. Additionally, a dynamic culture of cartilage tissue was performed, and the expression of cartilage-specific proteins within the culture time was studied by immunofluorescence staining analysis. The gelatin-based hydrogel scaffold encouraged chondrocyte proliferation, promoting the expression of collagen type II, aggrecan, and sox9 while retaining the structural stability and durability of the cartilage after dynamic compression and promoting cartilage repair.

Platelet-rich plasma treatment alleviates osteoarthritis-related pain, inflammation, and apoptosis by upregulating the expression levels of microRNA-375 and microRNA-337

OBJECTIVE

The present study was designed to determine the molecular mechanism by which platelet-rich plasma (PRP) acts on Osteoarthritis (OA) -related pain, inflammation, and apoptosis in vivo and in vitro.

MATERIALS AND METHODS

An in vivo OA model was established in rats using anterior cruciate ligament transection, and an in vitro OA model was created by treating chondrocytes with IL-1β. Then, the induced rats and chondrocytes were treated with PRP. Real-time PCR were used to examine the expression of micorRNAs (miRs) and mRNAs of inflammatory cytokines. WB were performed to detect the expression of apoptotic factors and Wnt/β-catenin signals. Structural damage of the cartilage and pain in OA rats were analyzed and represented by Mankin Score, OARSIS score, Tender threshold, and Thermal pain threshold. CCK-8 assay and flow cytometry were used to determine cell viability and apoptosis.

RESULTS

The expression levels of miR-337 and miR-375 were downregulated in the in vivo and vitro OA models; however, PRP treatment elevated their levels. miR-337 and miR-375 inhibition reversed the effects of PRP of reducing tenderness and thermal pain thresholds in OA rats. Moreover, PRP decreased the mRNA expression levels of MMP-13, Bax, and inflammatory factors, such as IL-1β, IL-18, and TNF-α, as well as increased the expression levels of collagen II and antiapoptotic Bcl-2. The decrease in inflammation and apoptosis was reversed by miR-337 and miR-375 inhibition, respectively.

DISCUSSION AND CONCLUSIONS

In conclusion, miR-337 and miR-375 are involved in PRP-delayed OA progression by affecting inflammation and apoptosis.

Dedifferentiation: inspiration for devising engineering strategies for regenerative medicine

Cell dedifferentiation is the process by which cells grow reversely from a partially or terminally differentiated stage to a less differentiated stage within their own lineage. This extraordinary phenomenon, observed in many physiological processes, inspires the possibility of developing new therapeutic approaches to regenerate damaged tissue and organs. Meanwhile, studies also indicate that dedifferentiation can cause pathological changes. In this review, we compile the literature describing recent advances in research on dedifferentiation, with an emphasis on tissue-specific findings, cellular mechanisms, and potential therapeutic applications from an engineering perspective. A critical understanding of such knowledge may provide fresh insights for designing new therapeutic strategies for regenerative medicine based on the principle of cell dedifferentiation.

Simvastatin-dependent actin cytoskeleton rearrangement regulates differentiation via the extracellular signal-regulated kinase-1/2 and p38 kinase pathways in rabbit articular chondrocytes

Alterations in cell morphology involve changes in the actin cytoskeleton and play crucial roles in determining chondrocyte phenotypes. Although the effects of simvastatin (SV) have been demonstrated in various cell types, the mechanisms and effects of SV on chondrocyte differentiation and actin cytoskeletal rearrangement are still unclear. Here, we investigated the roles of actin filament rearrangement on SV-induced differentiation of rabbit articular chondrocytes. Treatment with SV caused actin remodeling in comparison with that in untreated chondrocytes, as determined by immunofluorescence staining. Moreover, treatment with cytochalasin D (CD) and jasplakinolide (JAS), which modulate actin filament formation, resulted in reorganization of the actin cytoskeleton compared with that induced by SV in chondrocytes. In addition, CD synergistically enhanced the SV-induced increase in type II collagen expression, whereas JAS dramatically inhibited SV-induced differentiation. We also found that differentiation via SV-dependent actin cytoskeleton changes was regulated by the extracellular signal-regulated kinase (ERK)-1/2 and p38 kinase pathways. These results demonstrated that actin cytoskeletal rearrangement by SV regulated type II collagen expression and suggested that ERK-1/2 and p38 kinase pathways may play important roles in SV-induced type II collagen expression by altering actin cytoskeletal reorganization in rabbit articular chondrocytes.

PEP-1-glutaredoxin-1 induces dedifferentiation of rabbit articular chondrocytes by the endoplasmic reticulum stress-dependent ERK-1/2 pathway and the endoplasmic reticulum stress-independent p38 kinase and PI-3 kinase pathways

Glutaredoxin-1 (GRX-1), belonging to the oxidoreductase family, is a component of the endogenous antioxidant defense system. In this study, we evaluated the effects of PEP-1-GRX-1 in rabbit articular chondrocytes. We found that PEP-1-GRX-1 causes a loss of the differentiated chondrocyte phenotype. PEP-1-GRX-1-treated cells exhibited decreases in type II collagen expression and sulfated-proteoglycan synthesis in a dose- and time-dependent manner. PEP-1-GRX-1 causes endoplasmic reticulum (ER)-stress, as evidenced by increases in ER stress marker proteins, i.e., glucose-regulated protein (GRP) 78, GRP 94, and phospho-eukaryotic initiation factor 2 (eIF2) α. These effects were inhibited by ER stress inhibitors. PEP-1-GRX-1 increased the phosphorylation of Akt, extracellular signal-regulated kinase (ERK)-1/2, and p38. Inhibition of ERK-1/2 by PD98059 prevented PEP-1-GRX-1-induced dedifferentiation and inhibited ER stress. The blockage of PI-3K/Akt or p38 kinase with SB203580 and LY294002 accelerated PEP-1-GRX-1-induced dedifferentiation, but did not have any effect on PEP-GRX-1-induced ER stress. Our results indicate that the ERK-1/2 pathway mediates chondrocyte dedifferentiation by PEP-GRX-1-induced ER stress. The PI-3K and p38 kinase pathways regulate PEP-1-GRX-1-induced chondrocyte dedifferentiation by an ER stress-independent pathway.

Exposure to fermentation supernatant of Staphylococcus aureus accelerated dedifferentiation of chondrocytes and production of antimicrobial peptides

Staphylococcus aureus (S. aureus) is the most popular pathogen found in septic arthritis. Despite bacteria was eradicated from joint cavity during acute infection, destruction of articular cartilage often continues for years, leading to permanent joint damage. The mechanism responsible for this consistent catabolic reaction in septic arthritis remains unclear. Here, we found that fermentation supernatant (FS) of S. aureus accelerated dedifferentiation of chondrocytes and induced expression of catabolic factors including A Disintegrin-like and Metalloproteinase with Thrombospondin-1 motifs 5, NO synthase 2, matrix metalloproteinase-3, -13. In response to FS of S. aureus stimulation, expression of antimicrobial peptides (AMPs) including β-defensin-1, -2, -3, -4, cathelicidin antimicrobial peptide (CAMP) in dedifferentiated chondrocytes was significantly higher than that in chondrocytes which maintained their differentiated phenotype. Among AMPs detected, expression of CAMP in dedifferentiated chondrocytes was observed to increase 170 times higher than that in differentiated ones. When exposed to FS of S. aureus, expression of interleukin (IL)-1β, IL-17F, and IL-22 were remarkably increased in dedifferentiated chondrocytes. These results indicated that dedifferentiation of chondrocytes caused by exposure to S. aureus might be responsible for secondary osteoarthritis (OA) after acute S. aureus infection in joint. While, one potential benefit of dedifferentiation resulted from S. aureus exposure is that chondrocytes initiates a self-protective responsiveness by producing more AMPs against bacterial infection. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:443-451, 2018.

PEP-1-SIRT2-induced matrix metalloproteinase-1 and -13 modulates type II collagen expression via ERK signaling in rabbit articular chondrocytes

Matrix metalloproteinases (MMPs) are critical for the degradation of the extracellular matrix (ECM), which includes cartilage-specific collagen types I, II and XI. We previously found that PEP-1-sirtuin (SIRT)2 could induce dedifferentiation of articular chondrocytes; however, the underlying mechanisms remains unclear. We addressed this in the present study by examining the association between PEP-1-SIRT2 and the expression of MMP-1 and MMP-13 and type II collagen in rabbit articular chondrocytes. We found that PEP-1-SIRT2 increased MMP-1 and -13 expression in a dose- and time-dependent manner, as determined by western blotting. A similar trend in MMP-1 and -13 levels was observed in cultures during expansion to four passages. Pharmacological inhibition of MMP-1 and -13 blocked the PEP-1-SIRT2-induced decrease in type II collagen level. Phosphorylation of extracellular regulated kinase (ERK) was increased by PEP-1-SIRT2; however, treatment with the mitogen-activated protein kinase inhibitor PD98059 suppressed PEP-1-SIRT2-induced MMP-1 and -13 expression and dedifferentiation while restoring type II collagen expression in passage 2 cells. These results suggest that PEP-1-SIRT2 promotes MMP-induced dedifferentiation via ERK signaling in articular chondrocytes.

Cytokine-induced apoptosis inhibitor-1 causes dedifferentiation of rabbit articular chondrocytes via the ERK-1/2 and p38 kinase pathways

Cytokine-induced apoptosis inhibitor-1 (CIAPIN-1, formally named anamorsin) is a well-known regulator of apoptosis in many different cell types. Recently, it has been reported that some anti-apoptotic proteins are involved with the regulation of cell differentiation. However, relatively little is known about the role of CIAPIN-1 on rabbit articular chondrocytes differentiation. In this study, we investigated the effects of CIAPIN-1 in chondrocytes, focusing on extracellular signal-regulated kinase (ERK)-1/2 and p38 kinase signaling. CIAPIN-1 caused dedifferentiation, as determined by the inhibition of type II collagen expression and sulfated-proteoglycan synthesis. CIAPIN-1 activated ERK-1/2 and inactivated p38 kinase, as determined by the phosphorylation level of each protein. CIAPIN-1-induced ERK phosphorylation was abolished by the MEK inhibitor, PD98059, which also prevented the CIAPIN-1-induced loss of type II collagen expression. Inhibition of p38 kinase with SB203580 enhanced the decrease in type II collagen expression. Our findings collectively suggest that ERK-1/2 and p38 kinase regulate CIAPIN-1-induced dedifferentiation in rabbit articular chondrocytes.