Tumor necrosis factor alpha-dependent aggrecan cleavage and release of glycosaminoglycans in the meniscus is mediated by nitrous oxide-independent aggrecanase activity in vitro

Tranexamic acid has positive effect in early period of tendon healing by stimulating the tumor necrosis factor-alpha and matrix metalloproteinase-3 expression levels

Objectives

This study aims to evaluate the effect of tranexamic acid (TXA) application in tendon healing by using its immunohistochemical effects on tumor necrosis factor-alpha (TNF-α), matrix metalloproteinase-3 (MMP-3), and transforming growth factor-beta (TGF-β) expression; and to identify if TNF-α, MMP-3, and TGF-β can be used to monitor and evaluate tendon healing or not in tenotomized rat Achilles tendons.

Materials and methods

Twelve male Wistar-Albino rats (age 6-7-month-old; weighing 300-350 g) were used in this retrospective study conducted between November 2016 and May 2017. The rats were divided into two groups with similar weights. The right legs of the rats were determined as the study group (TXA), and the left legs as the control serum physiologic (SP) group. Under anesthesia, bilateral Achilles tenotomy was performed and surgically repaired. 1 mL of TXA was applied locally for the right side and 1 mL of SP was locally applied for the left side. Half of the rats were sacrificed at the third week (right leg-TXA3, left leg-SP3) and the other half at sixth week (right leg-TXA6, left leg-SP6) and tendon samples were taken from the extremities. Immunohistochemical findings of TNF-α, MMP-3, and TGF-β were evaluated on the basis of the frequency and intensity of staining.

Results

In TNF-α and MMP-3 and TXA groups, there was a significant difference in staining compared to SP groups (p<0.05). Regarding TNF-α expression, the total index score in the TXA6 subgroup was higher than the TXA3, SP6, and SP3 subgroups (8, 7, 3, and 4, respectively). Overall scores of TNF-α showed that TXA groups had significantly higher scores when compared to SP groups (p<0.05). In addition, total MMP-3 expression scores were significantly higher in TXA groups than in SP groups, respectively; TXA3: 14, TXA6: 11, SP3: 10, and SP6: 9 (p<0.05). However, the degree of staining with TNF-α was found to be significantly lower than MMP-3 (p<0.05). Immunohistochemical reactivity was not observed with TGF-β.

Conclusion

Tranexamic acid has positive effect in early period of tendon healing by stimulating the TNF-α and MMP-3 expression levels. TNF-α and MMP-3 can be used to monitor and evaluate tendon healing.

Matrix Metalloproteinase-3 is Key Effector of TNF-α-Induced Collagen Degradation in Skin

Inflammatory processes in the skin augment collagen degradation due to the up-regulation of matrix metalloproteinases (MMPs). The aim of the present project was to study the specific impact of MMP-3 on collagen loss in skin and its interplay with the collagenase MMP-13 under inflammatory conditions mimicked by the addition of the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α). Skin explants from MMP-3 knock-out (KO) mice or from transgenic (TG) mice overexpressing MMP-3 in the skin and their respective wild-type counterparts (WT and WTT) were incubated ex vivo for eight days. The rate of collagen degradation, measured by released hydroxyproline, was reduced (p < 0.001) in KO skin explants compared to WT control skin but did not differ (p = 0.47) between TG and WTT skin. Treatment with the MMP inhibitor GM6001 reduced hydroxyproline media levels from WT, WTT and TG but not from KO skin explants. TNF-α increased collagen degradation in the WT group (p = 0.0001) only. More of the active form of MMP-13 was observed in the three MMP-3 expressing groups (co-incubation with receptor-associated protein stabilized MMP-13 subforms and enhanced detection in the media). In summary, the innate level of MMP-3 seems responsible for the accelerated loss of cutaneous collagen under inflammatory conditions, possibly via MMP-13 in mice.

IL-21 Enhances the Degradation of Cartilage Through the JAK-STAT Signaling Pathway During Osteonecrosis of Femoral Head Cartilage

This study aims to investigate the role of interleukin-21 (IL-21) in the mechanism of osteonecrosis of the femoral head. The serum content of IL-21 in patients with osteonecrosis of the femoral head (ONFH) and with femoral neck fracture (FNF) was examined by an enzyme-linked immunosorbent assay (ELISA). The cartilage specimens were stained with safranin-O. The expression of IL-21, tumor necrosis factor-α (TNF-α), cyclooxygenase (COX-2), a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4), matrix metalloproteinase-13(MMP-13), and aggrecan in the cartilage was detected, by immunohistochemistry and western blot analysis. Moreover, chondrocytes were treated with IL-21 (100 ng/mL) or PBS to examine the mRNA content of TNF-α, COX-2, IL-1β and NOS-2 by RT-PCR, and the protein levels of ADAMTS-4, MMP-13, and aggrecan by western blot analysis. The activity of the JAK-STAT pathway was determined in vitro after stimulation with IL-21. IL-21 serum levels were obviously higher in the ONFH patients and positively correlated with the severity of ONFH. There were more cells positive for inflammatory cytokines, including IL-21, TNF-α, and COX-2, in the cartilage of the ONFH patients than the FNF patients. The level of certain relative biomarkers, such as ADAMTS-4 and MMP-13, was higher and aggrecan was lower in the ONFH patients. The mRNA contents of TNF-α, COX-2, IL-1β, and NOS-2, as well as the levels of ADAMTS-4, MMP-13, were enhanced, and aggrecan decreased after stimulation with IL-21. The protein content of p-STAT-1, as well as p-STAT-3, also increased after IL-21 stimulation, and the highest level appeared at 30 min. Furthermore, the protein level of ADAMTS-4 and MMP-13 and the mRNA level of TNF-α, COX-2, IL-1β, and NOS-2 significantly decreased after stimulation with AG-490. IL-21 enhances cartilage inflammation to promote cartilage degradation through the JAK-STAT signaling pathway in the cartilage of ONFH patients.

IL-10 ameliorates TNF-α induced meniscus degeneration in mature meniscal tissue in vitro

Background

Joint inflammation causes meniscus degeneration and can exacerbate post-traumatic meniscus injuries by extracellular matrix degradation, cellular de-differentiation and cell death. The aim of this study was to examine whether anti-inflammatory interleukin-10 exerts protective effects in an in vitro model of TNF-α-induced meniscus degeneration.

Methods

Meniscus tissue was harvested from the knees of adult cows. After 24 h of equilibrium explants were simultaneously treated with bovine TNF-α and IL-10. After an incubation time of 72 h cell death was measured histomorphometrically (nuclear blebbing, NB) and release of glycosaminoglycans (GAG, DMMB assay) and nitric oxide (NO, Griess-reagent) were analysed. Transcription levels (mRNA) of matrix degrading enzymes, collagen type X (COL10A1) and nitric oxide synthetase 2 (NOS2) were measured by quantitative real time PCR. TNF-α-dependent formation of the aggrecanase-specific aggrecan neoepitope NITEGE was visualised by immunostaining. Differences between groups were calculated using a one-way ANOVA with a Bonferroni post hoc test.

Results

Administration of IL-10 significantly prevented the TNF-α-related cell death (P .001), release of NO (P .003) and NOS2 expression (P .04). Release of GAG fragments (P .001), NITEGE formation and expression of MMP3 (P .007), -13 (P .02) and ADAMTS4 (P .001) were significantly reduced. The TNF-α-dependent increase in COL10A1 expression was also antagonized by IL-10 (P .02).

Conclusion

IL-10 prevented crucial mechanisms of meniscal degeneration induced by a key cytokine of OA, TNF-α. Administration of IL-10 might improve the biological regeneration and provide a treatment approach in degenerative meniscus injuries and in conditions of post-traumatic sports injuries.

Selenium Reduces Early Signs of Tumor Necrosis Factor Alpha-Induced Meniscal Tissue Degradation

Meniscal integrity is a prerequisite for sustained knee joint health and prevention of meniscal degeneration is a main research goal. Cartilage-protective effects of selenium have been described, but little is known about the impact on the meniscus. We therefore investigated the influence of sodium selenite on meniscal explants under tumor necrosis factor-alpha (TNFα)-stimulated proinflammatory conditions. Meniscal explant disks (3 mm diameter × 1 mm thickness) were isolated from 2-year-old cattle and incubated with TNFα (10 ng/ml) and sodium selenite (low dose, LoD 6.7 ng/ml as being found in Insulin-Transferrin-Selenium medium supplements, ITS; medium-dose, MeD 40 ng/ml described as physiological synovial concentration; high dose, HiD 100 ng/ml described as optimal serum concentration). After 3 days of culture glycosaminoglycan (GAG) release (DMMB assay), nitric oxide (NO) production (Griess assay), gene expression of matrix-degrading enzymes (quantitative RT-PCR), and apoptosis rate were determined. TNFα led to a significant raise of GAG release and NO production. LoD and MeD selenite significantly reduced the TNFα-induced GAG release (by 83, 55 %, respectively), NO production (by 59, 40 %, respectively), and apoptosis (by 68, 39 %, respectively). LoD and MeD selenite showed a tendency to reduce the TNFα-mediated increase of inducible NO-synthase (iNOS) levels, LoD selenite furthermore matrix metalloproteinase (MMP)-3 transcription levels and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 levels. LoD and less pronounced MeD selenite show a substantial impact on the early meniscal inflammatory response. To our knowledge this is the first study showing the protective influence of selenium on meniscal tissue maintenance. To understand the superior potency of low-dose selenium on molecular level future studies are needed.

Contrast-enhanced CT imaging as a non-destructive tool for ex vivo examination of the biochemical content and structure of the human meniscus

The biochemical and histopathological techniques used to investigate meniscal content and structure are destructive and time-consuming. Therefore, this study evaluated whether contrast-enhanced computed tomography (CECT) attenuation and contrast agent flux using the iodinated contrast agents CA4+ and ioxaglate correlate with the glycosaminoglycan (GAG) content/distribution and water content in human menisci. The optimal ioxaglate and CA4+ contrast agent concentrations for mapping meniscal GAG distribution were qualitatively determined by comparison of CECT color maps with Safranin-O stained histological sections. The associations between CECT attenuation and GAG content, CECT attenuation and water content, and flux and water content at various time points were determined using both contrast agents. Depth-wise analyses were also performed through each of the native surfaces to examine differences in contrast agent diffusion kinetics and equilibrium partitioning. The optimal concentrations for GAG depiction for ioxaglate and CA4+ were ≥80 and 12 mgI/ml, respectively. Using these concentrations, weak to moderate associations were found between ioxaglate attenuation and GAG content at all diffusion time points (1-48 h), while strong and significant associations were observed between CA4+ attenuation and GAG content as early as 7 h (R²  ≥ 0.67), being strongest at the equilibrium time point (48 h, R²  = 0.81). CECT attenuation for both agents did not significantly correlate with water content, but CA4+ flux correlated with water content (R²  = 0.56-0.64). CECT is a promising, non-destructive imaging technique for ex vivo assessment of meniscal GAG concentration and water content compared to traditional biochemical and histopathological methods. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1018-1028, 2017.

Response of mature meniscal tissue to a single injurious compression and interleukin-1 in vitro

OBJECTIVE

To study mechanical overload of mature meniscal tissue under normal and pro-inflammatory conditions in vitro.

METHOD

Three days after a single unconfined compression (strain: 25-75%, strain rate 1/s) of meniscal explants from 16 to 24 months-old cattle combined with interleukin-1-treatment (IL-1, 10 ng/ml) release of glycosaminoglycans (GAGs; dimethylmethylene blue (DMMB) assay), lactate dehydrogenase (LDH; cytotoxicity detection kit), and nitric oxide (NO; Griess assay), as well as gene transcription (quantitative reverse transcription polymerase chain reaction (RT-PCR)) and numbers of cells with condensed nuclei (CN; histomorphometry) were determined.

RESULTS

Mean peak stresses during compression were about five (25%), 11 (50%), and 30 MPa (75%), respectively. GAG and LDH release and numbers of CN increased whereas NO production and mRNA levels of matrix metalloproteinase (MMP)-2, -3 and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 decreased strain-dependently after compression. IL-1 induced an increase in GAG and NO release as well as MMP-2, -3 and ADAMTS-4 levels, but had no impact on the LDH release and slightly increased numbers of CN. However, in combination with compression the tissue responses were reduced and LDH and CN levels were increased compared to IL-1 alone.

CONCLUSION

Our data suggest that a single impact compression induces cell damage and release of GAG and reduces the NO production and transcription of certain matrix-degrading enzymes. It also reduces the capacity of meniscal tissue to respond to IL-1, which might be related to the cell damage and suggests that the compression-related GAG release might rather be the result of immediate extracellular matrix-damage than a cell-mediated event. This, however, needs to be confirmed in future studies.

Zonal differences in meniscus matrix turnover and cytokine response

OBJECTIVE

To determine the mechanisms of meniscal degeneration and whether this varied zonally and from articular cartilage.

DESIGN

Normal ovine menisci were dissected into inner and outer zones and along with cartilage cultured ±IL-1α and TNFα. Glycosaminoglycan (GAG) and collagen release, and gene expression were quantified. Aggrecan proteolysis was analysed by Western blotting with neoepitope-specific antibodies. Matrix metalloproteinase (MMP)2, MMP9 and MMP13 activity was evaluated by gelatin zymography or fluorogenic assay.

RESULTS

Inner meniscus was more cartilaginous containing more GAG and expressing more ACAN and COL2A1 than outer zones. Higher expression of VCAN and ADAMTS4 in medial outer and both zones of the lateral meniscus reflected their embryologic origin from cells outside the cartilage anlagen. All meniscal regions released a greater % GAG in response to cytokines; only outer zones had cytokine-stimulated collagenolysis. Cytokine-induced aggrecanolysis was primarily due to increased ADAMTS cleavage in cartilage and inner menisci but MMPs in the outer menisci. Outer menisci always released more active MMP2 than other tissues and more active MMP13 in basal and TNF-stimulated cultures. Expression of ACAN, COL1A1 and COL2A1 was decreased by both cytokines in all tissues, while VCAN was increased by IL-1α in cartilage and inner menisci. Metalloproteinase expression was differentially regulated by IL-1α and TNFα: ADAMTS4, MMP1, MMP3 were upregulated more by IL-1α in inner zones whereas ADAMTS5, MMP13 and MMP9 were more upregulated by TNFα in outer zones.

CONCLUSIONS

Meniscal degeneration mechanisms are zonally-dependent, and may contribute to the enzymatic burden in the joint.

Regional variation in the mechanical role of knee meniscus glycosaminoglycans

High compressive properties of cartilaginous tissues are commonly attributed to the sulfated glycosaminoglycan (GAG) fraction of the extracellular matrix (ECM), but this relationship has not been directly measured in the knee meniscus, which shows regional variation in GAG content. In this study, biopsies from each meniscus region (outer, middle, and inner) were either subjected to chondroitinase ABC (CABC) to remove all sulfated GAGs or not. Compressive testing revealed that GAG depletion in the inner and middle meniscus regions caused a significant decrease in modulus of relaxation (58% and 41% decreases, respectively, at 20% strain), and all regions exhibited a significant decrease in viscosity (outer: 29%; middle: 58%; inner: 62% decrease). Tensile properties following CABC treatment were unaffected for outer and middle meniscus specimens, but the inner meniscus displayed significant increases in Young's modulus (41% increase) and ultimate tensile stress (40% increase) following GAG depletion. These findings suggest that, in the outer meniscus, GAGs contribute to increasing tissue viscosity, whereas in the middle and inner meniscus, where GAGs are most abundant, these molecules also enhance the tissue's ability to withstand compressive loads. GAGs in the inner meniscus also contribute to reducing the circumferential tensile properties of the tissue, perhaps due to the pre-stress on the collagen network from increased hydration of the ECM. Understanding the mechanical role of GAGs in each region of the knee meniscus is important for understanding meniscus structure-function relationships and creating design criteria for functional meniscus tissue engineering efforts.

Dynamic loading enhances integrative meniscal repair in the presence of interleukin-1

OBJECTIVE

Meniscal tears are a common knee injury and increased levels of interleukin-1 (IL-1) have been measured in injured and degenerated joints. Studies have shown that IL-1 decreases the shear strength, cell accumulation, and tissue formation in meniscal repair interfaces. While mechanical stress and IL-1 modulate meniscal biosynthesis and degradation, the effects of dynamic loading on meniscal repair are unknown. The purpose of this study was to determine the effects of mechanical compression on meniscal repair under normal and inflammatory conditions.

EXPERIMENTAL DESIGN

Explants were harvested from porcine medial menisci. To simulate a full-thickness defect, a central core was removed and reinserted. Explants were loaded for 4h/day at 1 Hz and 0%-26% strain for 14 days in the presence of 0 or 100 pg/mL of IL-1. Media were assessed for matrix metalloproteinase (MMP) activity, aggrecanase activity, sulfated glycosaminoglycan (S-GAG) release, and nitric oxide (NO) production. After 14 days, biomechanical testing and histological analyses were performed.

RESULTS

IL-1 increased MMP activity, S-GAG release, and NO production, while decreasing the shear strength and tissue repair in the interface. Dynamic loading antagonized IL-1-mediated inhibition of repair at all strain amplitudes. Neither IL-1 treatment nor strain altered aggrecanase activity. Additionally, strain alone did not alter meniscal healing, except at the highest strain magnitude (26%), a level that enhanced the strength of repair.

CONCLUSIONS

Dynamic loading blocked the catabolic effects of IL-1 on meniscal repair, suggesting that joint loading through physical therapy may be beneficial in promoting healing of meniscal lesions under inflammatory conditions.