Effect of quercetin on chondrocyte phenotype and extracellular matrix expression / 中国天然药物

Due to the poor repair ability of cartilage tissue, regenerative medicine still faces great challenges in the repair of large articular cartilage defects. Quercetin is widely applied as a traditional Chinese medicine in tissue regeneration including liver, bone and skin tissues. However, the evidence for its effects and internal mechanisms for cartilage regeneration are limited. In the present study, the effects of quercetin on chondrocyte function were systematically evaluated by CCK8 assay, PCR assay, cartilaginous matrix staining assays, immunofluorescence assay, and western blotting. The results showed that quercetin significantly up-regulated the expression of chondrogenesis genes and stimulated the secretion of GAG (glycosaminoglycan) through activating the ERK, P38 and AKT signalling pathways in a dose-dependent manner. Furthermore, in vivo experiments revealed that quercetin-loaded silk protein scaffolds dramatically stimulated the formation of new cartilage-like tissue with higher histological scores in rat femoral cartilage defects. These data suggest that quercetin can effectively stimulate chondrogenesis in vitro and in vivo, demonstrating the potential application of quercetin in the regeneration of cartilage defects.

Direct inhibitory effect of caffeine on viability, synthesis activity and gene expression in cultures of chondrocytes extracted from the articular cartilage of rats / Efeito inibidor direto da cafeína sobre a viabilidade, atividade de síntese e expressão gênica em culturas de condrócitos da cartilagem articular de ratos

The aim of this study was to evaluate the effect of concentrations of caffeine on the viability, synthesis activity and gene expression in cultures of chondrocytes. Extracted articular cartilage from the femurs and tibias of 15 Wistar rats at three days old to isolate chondrocytes. Chondrocytes were cultured in chondrogenic medium (control) or supplemented with caffeine (0.5, 1.0, 2.0mM). Cell viability, alkaline phosphatase activity and collagen synthesis were assessed using colorimetric assays at 7, 14, 21 days. The chondrocyte cultures of all groups grown under coverslips were stained with hematoxylin-eosin to determine the percentage of cells/field and with PAS, safranin O, alcian blue to determine the percentage of matrix chondrogenic/field at 21 days. The expressions of gene transcripts for aggrecan, collagen-II, Sox-9, Runx-2 and alkaline phosphatase were also evaluated by RT-PCR at 21 days. The means were compared using Student-Newman-Keuls. Caffeine significantly reduced the conversion of MTT to formazan, percentage of cells/field, collagen synthesis, alkaline phosphatase activity, synthesis of PAS+, safranin O+ and alcian blue+ chondrogenic matrix, and the expression of aggrecan, Sox-9 and II collagen. It is concluded that caffeine at concentrations of 0.5, 1.0, 2.0mM has a direct inhibitory effect on chondrogenesis in cultures of chondrocytes from rats.(AU)

O objetivo deste estudo foi avaliar o efeito direto de concentrações de cafeína sobre a viabilidade, atividade de síntese e expressão gênica em culturas de condrócitos de ratos. As cartilagens dos fêmures e tíbias de 15 ratos Wistar com três dias foram extraídas para isolamento de condrócitos. Os condrócitos foram cultivados em meio condrogênico (controle) ou em meio acrescido de diferentes concentrações de cafeína (0,5, 1,0, 2,0mM). Foram avaliadas a viabilidade celular, a atividade da fosfatase alcalina e a síntese de colágeno por ensaios colorimétricos aos sete, 14 e 21 dias. Condrócitos cultivados sob lamínulas foram corados pela hematoxilina e eosina, para se determinar a porcentagem de células/campo, e pelo PAS, safranina O, alcian Blue, para se determinar a porcentagem de matriz condrogênica/campo aos 21 dias. Foi avaliada a expressão de transcriptos gênicos para Sox-9, Runx-2, agrecano, colágeno-II e fosfatase alcalina por qRT-PCR, aos 21 dias. As médias foram comparadas pelo Student-Newman-Keuls. A cafeína reduziu significativamente o MTT em cristais de formazan, a porcentagem de células/campo, a síntese de colágeno, a atividade da fosfatase alcalina e a síntese de matriz condrogênica PAS+, safranina O+, alcian blue+ e expressão de Sox-9 e colágeno-II. Conclui-se que a cafeína, nas concentrações de 0,5, 1,0, 2,0mM, apresenta efeito inibidor direto sobre a condrogênese em culturas de condrócitos de ratos.(AU)

Effect of JJYMD-C, a novel synthetic derivative of gallic acid, on proliferation and phenotype maintenance in rabbit articular chondrocytes in vitro

Tissue engineering encapsulated cells such as chondrocytes in the carrier matrix have been widely used to repair cartilage defects. However, chondrocyte phenotype is easily lost when chondrocytes are expanded in vitro by a process defined as “dedifferentiation”. To ensure successful therapy, an effective pro-chondrogenic agent is necessary to overcome the obstacle of limited cell numbers in the restoration process, and dedifferentiation is a prerequisite. Gallic acid (GA) has been used in the treatment of arthritis, but its biocompatibility is inferior to that of other compounds. In this study, we modified GA by incorporating sulfamonomethoxine sodium and synthesized a sulfonamido-based gallate, JJYMD-C, and evaluated its effect on chondrocyte metabolism. Our results showed that JJYMD-C could effectively increase the levels of the collagen II, Sox9, and aggrecan genes, promote chondrocyte growth, and enhance secretion and synthesis of cartilage extracellular matrix. On the other hand, expression of the collagen I gene was effectively down-regulated, demonstrating inhibition of chondrocyte dedifferentiation by JJYMD-C. Hypertrophy, as a characteristic of chondrocyte ossification, was undetectable in the JJYMD-C groups. We used JJYMD-C at doses of 0.125, 0.25, and 0.5 µg/mL, and the strongest response was observed with 0.25 µg/mL. This study provides a basis for further studies on a novel agent in the treatment of articular cartilage defects.

Staurosporine and cytochalasin D induce chondrogenesis by regulation of actin dynamics in different way

Actin cytoskeleton has been known to control and/or be associated with chondrogenesis. Staurosporine and cytochalasin D modulate actin cytoskeleton and affect chondrogenesis. However, the underlying mechanisms for actin dynamics regulation by these agents are not known well. In the present study, we investigate the effect of staurosporine and cytochalasin D on the actin dynamics as well as possible regulatory mechanisms of actin cytoskeleton modulation. Staurosporine and cytochalasin D have different effects on actin stress fibers in that staurosporine dissolved actin stress fibers while cytochalasin D disrupted them in both stress forming cells and stress fiber-formed cells. Increase in the G-/F-actin ratio either by dissolution or disruption of actin stress fiber is critical for the chondrogenic differentiation. Cytochalasin D reduced the phosphorylation of cofilin, whereas staurosporine showed little effect on cofilin phosphorylation. Either staurosporine or cytochalasin D had little effect on the phosphorylation of myosin light chain. These results suggest that staurosporine and cytochalasin D employ different mechanisms for the regulation of actin dynamics and provide evidence that removal of actin stress fibers is crucial for the chondrogenic differentiation.

Periosteum as a source of mesenchymal stem cells: the effects of TGF-β3 on chondrogenesis

INTRODUCTION: Numerous experimental efforts have been undertaken to induce the healing of lesions within articular cartilage by re-establishing competent repair tissue. Adult mesenchymal stem cells have attracted attention as a source of cells for cartilage tissue engineering. The purpose of this study was to investigate chondrogenesis employing periosteal mesenchymal cells. METHODS: Periosteum was harvested from patients who underwent orthopedic surgeries. Mesenchymal stem cells were characterized through flow cytometry using specific antibodies. The stem cells were divided into four groups. Two groups were stimulated with transforming growth factor β3 (TGF-β3), of which one group was cultivated in a monolayer culture and the other was cultured in a micromass culture. The remaining two groups were cultivated in monolayer or micromass cultures in the absence of TGF-β3. Cell differentiation was verified through quantitative reverse transcription-polymerase chain reaction (RT-PCR) and using western blot analysis. RESULT: In the groups cultured without TGF-β3, only the cells maintained in the micromass culture expressed type II collagen. Both the monolayer and the micromass groups that were stimulated with TGF-β3 expressed type II collagen, which was observed in both quantitative RT-PCR and western blot analysis. The expression of type II collagen was significantly greater in the micromass system than in the monolayer system. CONCLUSION: The results of this study demonstrate that the interactions between the cells in the micromass culture system can regulate the proliferation and differentiation of periosteal mesenchymal cells during chondrogenesis and that this effect is enhanced by TGF-β3.

TiO2 nanotube stimulate chondrogenic differentiation of limb mesenchymal cells by modulating focal activity

Vertically aligned, laterally spaced nanoscale titanium nanotubes were grown on a titanium surface by anodization, and the growth of chondroprogenitors on the resulting surfaces was investigated. Surfaces bearing nanotubes of 70 to 100 nm in diameter were found to trigger the morphological transition to a cortical actin pattern and rounded cell shape (both indicative of chondrocytic differentiation), as well as the up-regulation of type II collagen and integrin beta4 protein expression through the down-regulation of Erk activity. Inhibition of Erk signaling reduced stress fiber formation and induced the transition to the cortical actin pattern in cells cultured on 30-nm-diameter nanotubes, which maintained their fibroblastoid morphologies in the absence of Erk inhibition. Collectively, these results indicate that a titanium-based nanotube surface can support chondrocytic functions among chondroprogenitors, and may therefore be useful for future cartilaginous applications.

Curcumin inhibits cellular condensation and alters microfilament organization during chondrogenic differentiation of limb bud mesenchymal cells

Curcumin is a well known natural polyphenol product isolated from the rhizome of the plant Curcuma longa, anti-inflammatory agent for arthritis by inhibiting synthesis of inflammatory prostaglandins. However, the mechanisms by which curcumin regulates the functions of chondroprogenitor, such as proliferation, precartilage condensation, cytoskeletal organization or overall chondrogenic behavior, are largely unknown. In the present report, we investigated the effects and signaling mechanism of curcumin on the regulation of chondrogenesis. Treating chick limb bud mesenchymal cells with curcumin suppressed chondrogenesis by stimulating apoptotic cell death. It also inhibited reorganization of the actin cytoskeleton into a cortical pattern concomitant with rounding of chondrogenic competent cells and down-regulation of integrin beta1 and focal adhesion kinase (FAK) phosphorylation. Curcumin suppressed the phosphorylation of Akt leading to Akt inactivation. Activation of Akt by introducing a myristoylated, constitutively active form of Akt reversed the inhibitory actions of curcumin during chondrogenesis. In summary, for the first time, we describe biological properties of curcumin during chondrogenic differentiation of chick limb bud mesenchymal cells. Curcumin suppressed chondrogenesis by stimulating apoptotic cell death and down-regulating integrin-mediated reorganization of actin cytoskeleton via modulation of Akt signaling.

Alloxan-induced diabetes delays repair in a rat model of closed tibial fracture

A closed fracture was performed on the left tibia of 3-month-old Wistar rats weighing 250 to 350 g that were either healthy (N = 24) or made diabetic with alloxan (N = 24) to investigate the effect of alloxan-induced diabetes on the course of bone fracture healing. Histomorphometric analysis of the fracture site was performed at 7, 14, 25, and 35 days. After 7 days, diabetic rats had significantly less cartilage (P = 0.045) and greater fibrous connective (P = 0.006) tissue formation at the fracture site compared to controls. In contrast, marked callus formation was seen in diabetic rats with significant osteogenesis (P = 0.011, P = 0.010, P = 0.010, respectively, for 14, 25, and 35 days) and chondrogenesis (P = 0.028, P = 0.033, P = 0.019) compared to controls. Radiographic analysis revealed a displaced fracture with poor bone fragment alignment and delayed consolidation at these times in the diabetic group. The levels of alkaline phosphatase were significantly higher in diabetic rats at 25 days (P = 0.009). These results suggest that the initial excessive formation of fibrous connective tissue associated with delay in chondrogenesis and osteogenesis may not provide suitable stability of the fractured site, contributing to the inappropriate alignment of fragments and an increase in the volume of callus in later stages of repair. The resulting displaced fracture in diabetic rats requires long periods for remodeling and complete bone consolidation.

Chondrogenic differentiation of mouse bone marrow mesenchymal stem cells induced by cartilage-derived morphogenetic protein-2 in vitro / 华中科技大学学报（医学）（英德文版）

To study the cartilage differentiation of mouse mesenchymal stem cells (MSCs) induced by cartilage-derived morphogenetic proteins-2 in vitro, the MSCs were isolated from mouse bone marrow and cultured in vitro. The cells in passage 3 were induced into chondrogenic differentiation with different concentrations of recombinant human cartilage-derived morphogenetic proteins-2 (0, 10, 20, 50 and 100 ng/mL). After 14 days of induction, morphology of cells was observed under phase-contrast microscope. Collagen II mRNA and protein were examined with RT-PCR, Western blotting and immunocytochemistry respectively and the sulfate glycosaminoglycan was measured by Alcian blue staining. RT-PCR showed that CDMP-2 could promote expression of collagen II mRNA in an dose-dependant manner, especially at the concentration of 50 ng/mL and 100 ng/mL. Immunocytochemistry and Western blotting revealed a similar change. Alcian blue staining exhibited deposition of typical cartilage extracellular matrix. Our results suggest that mouse bone marrow mesenchymal stem cells can differentiate into chondrogenic phonotype with the induction of CDMP-2 in vitro, which provides a basis for further research on the role of CDMP-2 in chondrogenesis.