Selective targeting of dipeptidyl-peptidase 4 (DPP-4) positive senescent chondrocyte ameliorates osteoarthritis progression.

Senescent cells increase in many tissues with age and induce age-related pathologies, including osteoarthritis (OA). Senescent chondrocytes (SnCs) are found in OA cartilage, and the clearance of those chondrocytes prevents OA progression. However, targeting SnCs is challenging due to the absence of a senescent chondrocyte-specific marker. Therefore, we used flow cytometry to screen and select senescent chondrocyte surface markers and cross-validated with published transcriptomic data. Chondrocytes expressing dipeptidyl peptidase-4 (DPP-4), the selected senescent chondrocyte-specific marker, had multiple senescence phenotypes, such as increased senescence-associated-galactosidase, p16, p21, and senescence-associated secretory phenotype expression, and showed OA chondrocyte phenotypes. To examine the effects of DPP-4 inhibition on DPP-4+ SnCs, sitagliptin, a DPP-4 inhibitor, was treated in vitro. As a result, DPP-4 inhibition selectively eliminates DPP-4+ SnCs without affecting DPP-4- chondrocytes. To assess in vivo therapeutic efficacy of targeting DPP-4+ SnCs, three known senolytics (ABT263, 17DMAG, and metformin) and sitagliptin were comparatively verified in a DMM-induced rat OA model. Sitagliptin treatment specifically and effectively eliminated DPP-4+ SnCs, compared to the other three senolytics. Furthermore, Intra-articular sitagliptin injection to the rat OA model increased collagen type II and proteoglycan expression and physical functions and decreased cartilage destruction, subchondral bone plate thickness and MMP13 expression, leading to the amelioration of OA phenotypes. Collectively, OARSI score was lowest in the sitagliptin treatment group. Taken together, we verified DPP-4 as a surface marker for SnCs and suggested that the selective targeting of DPP-4+ chondrocytes could be a promising strategy to prevent OA progression.

High-glutathione mesenchymal stem cells isolated using the FreSHtracer probe enhance cartilage regeneration in a rabbit chondral defect model.

BACKGROUND: Mesenchymal stem cells (MSCs) are a promising cell source for cartilage regeneration. However, the function of MSC can vary according to cell culture conditions, donor age, and heterogeneity of the MSC population, resulting in unregulated MSC quality control. To overcome these limitations, we previously developed a fluorescent real-time thiol tracer (FreSHtracer) that monitors cellular levels of glutathione (GSH), which are known to be closely associated with stem cell function. In this study, we investigated whether using FreSHtracer could selectively separate high-functioning MSCs based on GSH levels and evaluated the chondrogenic potential of MSCs with high GSH levels to repair cartilage defects in vivo. METHODS: Flow cytometry was conducted on FreSHtracer-loaded MSCs to select cells according to their GSH levels. To determine the function of FreSHtracer-isolated MSCs, mRNA expression, migration, and CFU assays were conducted. The MSCs underwent chondrogenic differentiation, followed by analysis of chondrogenic-related gene expression. For in vivo assessment, MSCs with different cellular GSH levels or cell culture densities were injected in a rabbit chondral defect model, followed by histological analysis of cartilage-regenerated defect sites. RESULTS: FreSHtracer successfully isolated MSCs according to GSH levels. MSCs with high cellular GSH levels showed enhanced MSC function, including stem cell marker mRNA expression, migration, CFU, and oxidant resistance. Regardless of the stem cell tissue source, FreSHtracer selectively isolated MSCs with high GSH levels and high functionality. The in vitro chondrogenic potential was the highest in pellets generated by MSCs with high GSH levels, with increased ECM formation and chondrogenic marker expression. Furthermore, the MSCs' function was dependent on cell culture conditions, with relatively higher cell culture densities resulting in higher GSH levels. In vivo, improved cartilage repair was achieved by articular injection of MSCs with high levels of cellular GSH and MSCs cultured under high-density conditions, as confirmed by Collagen type 2 IHC, Safranin-O staining and O'Driscoll scores showing that more hyaline cartilage was formed on the defects. CONCLUSION: FreSHtracer selectively isolates highly functional MSCs that have enhanced in vitro chondrogenesis and in vivo hyaline cartilage regeneration, which can ultimately overcome the current limitations of MSC therapy.

Correction to: Hypoxic condition enhances chondrogenesis in synovium-derived mesenchymal stem cells.

[This corrects the article DOI: 10.1186/s40824-018-0134-x.].

Hypoxic condition enhances chondrogenesis in synovium-derived mesenchymal stem cells.

BACKGROUND: The chondrogenic differentiation of mesenchymal stem cells (MSCs) is regulated by many factors, including oxygen tensions, growth factors, and cytokines. Evidences have suggested that low oxygen tension seems to be an important regulatory factor in the proliferation and chondrogenic differentiation in various MSCs. Recent studies report that synovium-derived mesenchymal stem cells (SDSCs) are a potential source of stem cells for the repair of articular cartilage defects. But, the effect of low oxygen tension on the proliferation and chondrogenic differentiation in SDSCs has not characterized. In this study, we investigated the effects of hypoxia on proliferation and chondrogenesis in SDSCs. METHOD: SDSCs were isolated from patients with osteoarthritis at total knee replacement. To determine the effect of oxygen tension on proliferation and colony-forming characteristics of SDSCs, A colony-forming unit (CFU) assay and cell counting-based proliferation assay were performed under normoxic (21% oxygen) or hypoxic (5% oxygen). For in vitro chondrogenic differentiation, SDSCs were concentrated to form pellets and subjected to conditions appropriate for chondrogenic differentiation under normoxia and hypoxia, followed by the analysis for the expression of genes and proteins of chondrogenesis. qRT-PCR, histological assay, and glycosoaminoglycan assays were determined to assess chondrogenesis. RESULTS: Low oxygen condition significantly increased proliferation and colony-forming characteristics of SDSCs compared to that of SDSCs under normoxic culture. Similar pellet size and weight were found for chondrogensis period under hypoxia and normoxia condition. The mRNA expression of types II collagen, aggrecan, and the transcription factor SOX9 was increased under hypoxia condition. Histological sections stained with Safranin-O demonstrated that hypoxic conditions had increased proteoglycan synthesis. Immunohistochemistry for types II collagen demonstrated that hypoxic culture of SDSCs increased type II collagen expression. In addition, GAG deposition was significantly higher in hypoxia compared with normoxia at 21 days of differentiation. CONCLUSION: These findings show that hypoxia condition has an important role in regulating the synthesis ECM matrix by SDSCs as they undergo chondrogenesis. This has important implications for cartilage tissue engineering applications of SDSCs.

Flavonol-rich RVHxR from Rhus verniciflua Stokes and its major compound fisetin inhibits inflammation-related cytokines and angiogenic factor in rheumatoid arthritic fibroblast-like synovial cells and in vivo models.

Rheumatoid arthritis (RA) is an aggressive inflammatory disease in which cytokines/chemokines are thought to recruit leukocytes and induce angiogenesis. The aim of this study is to investigate the effect of flavonol-rich residual layer of hexane fraction from Rhus verniciflua Stokes (RVHxR) and its major compound fisetin on inflammatory cytokine/chemokine production and angiogenic factor in IL-1beta-stimulated RA fibroblast-like synovial cells (FLS) and inflammatory in vivo models. Flavonol-rich RVHxR and its major compound fisetin significantly inhibited IL-1beta-induced FLS proliferation in a dose-dependent manner. Flavonol-rich RVHxR and fisetin significantly decreased IL-1beta-induced inflammatory cytokines (TNF-alpha, interleukin (IL)-6)/chemokines (IL-8, monocyte chemoattractant protein (MCP)-1), and vascular endothelial growth factor (VEGF) of RA FLS. Flavonol-rich RVHxR dose dependently diminished the phophorylation of extracellular signal regulated kinase (ERK) and phospho-Jun NH((2))-terminal kinase (JNK), and its down regulation induced by RVHxR at nontoxic concentrations, while activated the phosphorylation of p38 MAPK in IL-1beta-stimulated RA FLS. The p38 specific inhibitor SB203580 cotreatment with RVHxR effectively increased the expression of VEGF and blocked the phosphorylation of p38 MAPK in IL-1beta-stimulated RA FLS, confirming a critical role of p38 MAPK pathway in angiogenesis inhibition. In experimental inflammation-related models, flavonol-rich RVHxR and fisetin have shown significant anti-inflammatory activities on vascular permeability, leukocyte migration and cellular immunity. Also, flavonol-rich RVHxR and fisetin treatments significantly reduced the incidence and severity of collagen-induced arthritis model. These results suggest that RVHxR and its major compound fisetin have shown potent suppressive effects on some inflammatory cytokines/chemokines and angiogenic factor in IL-1beta-stimulated RA FLS and inflammatory in vivo models. We believe that flavonol-rich RVHxR is a potential therapeutic agent in the treatment of inflammatory and angiogenesis related diseases.

Effect of Betula platyphylla var. japonica on proteoglycan release, type II collagen degradation, and matrix metalloproteinase expression in rabbit articular cartilage explants.

Articular cartilage is a potential target for drugs designed to inhibit the activity of matrix metalloproteinases (MMPs) to stop or slow the destruction of proteoglycan and collagen in the cartilage extracellular matrix. The purpose of this study was to investigate the effects of Betula platyphylla var. japonica on inhibiting the release of glycosaminoglycan (GAG), the degradation of collagen, and MMP expression and activity in rabbit articular cartilage explants. Interleukin-1alpha (IL-1alpha) rapidly induced GAG, but collagen was much less readily released from cartilage explants. Betula platyphylla var. japonica significantly inhibited GAG and collagen release in a concentration-dependent manner. Betula platyphylla var. japonica dose-dependently inhibited MMP-3 and MMP-13 expression and activities from IL-1alpha-treated cartilage explant culture when tested at concentrations ranging from 0.02 to 0.2 mg/ml. Betula platyphylla var. japonica had no harmful effect on chondrocyte viability or cartilage morphology in cartilage explants. Histological analysis indicated that Betula platyphylla var. japonica reduced the degradation of the cartilage matrix compared with that of IL-1alpha-treated cartilage explants. These results indicate that Betula platyphylla var. japonica inhibits the degradation of proteoglycan and collagen through the down regulation of MMP-3 and MMP-13 expression and activities without affecting the viability or morphology of IL-1alpha-stimulated rabbit articular cartilage explants.

Puerariae radix promotes differentiation and mineralization in human osteoblast-like SaOS-2 cells.

Puerariae radix (PR) is a traditional medicine herb used for enhancing body resistance against various diseases. The aim of this study was to identify whether Puerariae radix extract induces osteogenic activity in human osteoblast-like SaOS-2 cells. Puerariae radix had no effect on the viability of osteoblastic cells, and dose-dependently increased alkaline phosphatase (ALP) activity. Puerariae radix markedly increased mRNA expression for vascular endothelial growth factor (VEGF), osteocalcin (OCN), osteopontin (OPN), and type I collagen (Col I) in SaOS-2 cells. Extracellular accumulation of proteins such as VEGF and Col I was increased in a dose-dependent manner. Also, Puerariae radix significantly induced mineralization in the culture of SaOS-2 cells. In conclusion, this study showed that Puerariae radix had no effect on viability, but enhanced ALP activity, VEGF, bone matrix proteins such as OCN, OPN, and Col I, and mineralization in SaOS-2 cells. These results propose that Puerariae radix can play an important role in osteoblastic bone formation, and may possibly lead to the development of bone-forming drugs.

Uncaria rhynchophylla induces angiogenesis in vitro and in vivo.

Angiogenesis consists of the proliferation, migration, and differentiation of endothelial cells, and angiogenic factors and matrix protein interactions modulate this process. The aim of this study was to determine the angiogenic properties of Uncaria rhynchophylla. Uncaria rhynchophylla significantly enhanced human umbilical vein endothelial cells (HUVECs) proliferation in a dose-dependent manner. Neutralization of vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF) by monoclonal antibody suppressed the Uncaria rhynchophylla stimulatory effect on proliferation. In addition, Uncaria rhynchophylla significantly increased chemotactic-migration on gelatin and tubular structures on Matrigel of HUVECs in a dose-dependent manner. Interestingly, Uncaria rhynchophylla dose-dependently increased VEGF, and bFGF gene expression and protein secretion of HUVEC. The angiogenic activity of Uncaria rhynchophylla was confirmed using an in vivo Matrigel angiogenesis model, showing promotion of blood vessel formation. These results suggest that Uncaria rhynchophylla could potentially used to accelerate vascular wound healing or to promote the growth of collateral blood vessel in ischemic tissues.