Single impact cartilage trauma and TNF-α: interactive effects do not increase early cell death and indicate the need for bi-/multidirectional therapeutic approaches

Anti-inflammatory effects of tibial axial loading on knee articular cartilage post traumatic injury

Early therapeutic intervention to mitigate inflammatory responses following joint injury may offer a potential strategy to prevent post-traumatic osteoarthritis (PTOA). In-vitro studies have demonstrated uniaxial dynamic compression mitigates the catabolic and apoptotic responses of articular cartilage (AC) in response to mechanical injury. The objectives of this study were (1) to develop a custom device that can apply dynamic tibial axial loading (TAL) to knee AC by mimicking therapeutic, in-vitro loading conditions and (2) to investigate the potential of TAL to reduce the inflammatory response of AC post traumatic acute joint injury using an ex-vivo porcine model. A TAL device was fabricated to apply dynamic compressive loading to knee AC by combining tibial axial compressive loading with continuous passive motion. Computational analyses demonstrated that the loading condition applied to the knee by the TAL device closely simulate uniaxial dynamic compression reported in previous in-vitro studies. Following single impact injury, injured porcine knees were subjected to TAL with a magnitude of 1/4 body weight at a frequency of 1 Hz for 30 min. AC samples were harvested 8 h post injury for analysis of pro-inflammatory cytokine expression (IL-1β and TNF-α). Expression of both cytokines was upregulated following injury; however, the change was notably mitigated in the specimens subjected to TAL. Thus, TAL may be an effective and potentially, practical-to-administer early intervention strategy to mitigate rapidly occurring detrimental events following acute AC injury, potentially slowing down progression to PTOA.

The effects of TNF-alpha inhibition on cartilage: a systematic review of preclinical studies

OBJECTIVE

To report the most up-to-date evidence on the effects of tumour necrosis factor (TNF)-alpha inhibition on cartilage with a focus on its clinical relevance.

DESIGN

A systematic review was performed by searching PubMed, Embase and Cochrane Library databases. Inclusion criteria were studies of any level of evidence published in peer-reviewed journals reporting clinical or preclinical results written in English. Relative data were extracted and critically analysed. PRISMA guidelines were applied, and risk of bias was assessed as well as the methodological quality of the included studies.

RESULTS

13 studies were included after applying the inclusion and exclusion criteria. Three were in vitro human studies from osteoarthritis (OA) patients. Ten were animal modal studies including two in vitro studies, and eight in vivo studies. TNF-alpha inhibition in in vitro studies was generally reported beneficial due to the improved osteochondral viability, proliferation and chondrogenesis. In addition, TNF-alpha inhibition was noted to be beneficial in promoting the natural repair of osteochondral lesions and has a chondroprotective effect in in vivo studies.

CONCLUSION

Based on current evidence, TNF might have the potential to interfere with the healing process of chondral and osteochondral defects occurring naturally or in low inflammatory environment after a cartilage repair procedure. Therefore, the use of biological agents to inhibit its action in cartilage repair surgery could be beneficial, and this could translate into a promising therapy that improves the outcome of currently available cartilage procedures.

Characterization of a migrative subpopulation of adult human nasoseptal chondrocytes with progenitor cell features and their potential for in vivo cartilage regeneration strategies

Background

Progenitor cells display interesting features for tissue repair and reconstruction. In the last years, such cells have been identified in different cartilage types. In this study, we isolated a migrative subpopulation of adult human nasoseptal chondrocytes with progenitor cell features by outgrowth from human nasal septum cartilage. These putative progenitor cells were comparatively characterized with mesenchymal stem cells (MSC) and human nasal septum chondrocytes with respect to their cellular characteristics as well as surface marker profile using flow cytometric analyses. Differentiation capacity was evaluated on protein and gene expression levels.

Results

The migrative subpopulation differentiated into osteogenic and chondrogenic lineages with distinct differences to chondrocytes and MSC. Cells of the migrative subpopulation showed an intermediate surface marker profile positioned between MSC and chondrocytes. Significant differences were found for CD9, CD29, CD44, CD90, CD105 and CD106. The cells possessed a high migratory ability in a Boyden chamber assay and responded to chemotactic stimulation. To evaluate their potential use in tissue engineering applications, a decellularized septal cartilage matrix was either seeded with cells from the migrative subpopulation or chondrocytes. Matrix production was demonstrated immunohistochemically and verified on gene expression level. Along with secretion of matrix metalloproteinases, cells of the migrative subpopulation migrated faster into the collagen matrix than chondrocytes, while synthesis of cartilage specific matrix was comparable.

Conclusions

Cells of the migrative subpopulation, due to their migratory characteristics, are a potential cell source for in vivo regeneration of nasal cartilage. The in vivo mobilization of nasal cartilage progenitor cells is envisioned to be the basis for in situ tissue engineering procedures, aiming at the use of unseeded biomaterials which are able to recruit local progenitor cells for cartilage regeneration.

Differential Interactive Effects of Cartilage Traumatization and Blood Exposure In Vitro and In Vivo

BACKGROUND

Sport injuries of the knee often lead to posttraumatic arthritis. In addition to direct damage of the cartilage, trauma-associated intra-articular bleeding may cause hemarthrosis. Both blood exposure and trauma are known to induce cell death and inflammation and to enhance proteoglycan release in cartilage.

HYPOTHESIS

Blood exposure increases chondrocyte death as well as inflammatory and degenerative processes in traumatized cartilage.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human macroscopically intact osteoarthritic (OA) cartilage explants were impacted by a drop-tower system (0.59 J) and cultivated with or without 10% blood. Interactive effects were studied concerning cell survival, gene expression, and the release of mediators over 24 hours and 96 hours. To evaluate the effects of trauma and hemarthrosis in vivo, a newly established blunt cartilage trauma model in the rabbit was used. Treatment of the knee joints of mature New Zealand White rabbits consisted of the following groups: control (C), arthrotomy (A), arthrotomy with cartilage trauma (AT; 1.0 J), and arthrotomy with cartilage trauma and blood injection (ATH). After 1 and 12 weeks, inflammatory mediators in the synovial fluid and histological changes of the cartilage were determined, and immunohistological staining was performed.

RESULTS

The in vitro studies revealed a significant additional or synergistic effect of blood exposure on trauma-induced chondrocyte death, interleukin (IL)-1β and prostaglandin-E2 (PGE2) release, and matrix metalloproteinase (MMP)/pro-MMP level. Singular arthrotomy in vivo induced a temporary inflammation. Histologically, cartilage trauma caused significant OA changes that were not aggravated by an additional hemarthrosis. Trauma led to a persistent deposition of terminal complement complex (TCC), being enhanced by hemarthrosis. However, trauma-induced formation of osteophytes and arthrotomy-induced elevation of tumor necrosis factor-α release were reduced by hemarthrosis.

CONCLUSION

While blood exposure clearly aggravated trauma-induced OA processes in the in vitro model, a singular blood injection revealed heterogeneous effects in vivo, enhancing TCC deposition but reducing trauma-induced osteophyte formation while the histological score of traumatized cartilage was not further impaired.

CLINICAL RELEVANCE

The results of this study indicate that a singular, limited bleeding event might not exacerbate early trauma-induced cartilage degeneration in joint injuries. An early removal of intra-articular blood may not prevent the final resulting cartilage damage.

Role of miR-146a in human chondrocyte apoptosis in response to mechanical pressure injury in vitro

MicroRNA (miR)-146a is known to be overexpressed in osteoarthritis (OA). However, the role of miR-146a in OA has not yet been fully elucidated. In the present study, we applied mechanical pressure of 10 MPa to human chondrocytes for 60 min in order to investigate the expression of miR-146a and apoptosis following the mechanical pressure injury. Normal human chondrocytes were transfected with an miR-146a mimic or an inhibitor to regulate miR-146a expression. Potential target genes of miR-146a were predicted using bioinformatics. Moreover, luciferase reporter assay confirmed that Smad4 was a direct target of miR-146a. The expression levels of miR-146a, Smad4 and vascular endothelial growth factor (VEGF) were quantified by quantitative reverse transcription PCR and/or western blot analysis. The effects of miR-146a on apoptosis were detected by Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) flow cytometry. The results indicated that mechanical pressure affected chondrocyte viability and induced the early apoptosis of chondrocytes. Mechanical pressure injury increased the expression levels of miR-146a and VEGF and decreased the levels of Smad4 in the chondrocytes. In the human chondrocytes, the upregulation of miR-146a induced apoptosis, upregulated VEGF expression and downregulated Smad4 expression. In addition, the knockdown of miR-146a reduced cell apoptosis, upregulated Smad4 expression and downregulated VEGF expression. Smad4 was identified as a direct target of miR-146a by harboring a miR‑146a binding sequence in the 3'-untranslated region (3'-UTR) of its mRNA. Furthermore, the upregulation of VEGF induced by miR‑146a was mediated by Smad4 in the chondrocytes subjected to mechanical pressure injury. These results demonstrated that miR-146a was overexpressed in our chondrocyte model of experimentally induced human mechanical injury, accompanied by the upregulation of VEGF and the downregulation of Smad4 in vitro. Moreover, our data suggest that miR-146a is involved in human chondrocyte apoptosis in response to mechanical injury, and may contribute to the mechanical injury of chondrocytes, as well as to the pathogenesis of OA by increasing the levels of VEGF and damaging the transforming growth factor (TGF)-β signaling pathway through the targeted inhibition of Smad4 in cartilage.

In vitro effects of meloxicam on metabolism in articular chondrocytes from dogs with naturally occurring osteoarthritis

OBJECTIVE

To assess effects of in vitro meloxicam exposure on metabolism in articular chondrocytes from dogs with naturally occurring osteoarthritis.

SAMPLE

Femoral head cartilage from 16 dogs undergoing total hip replacement.

PROCEDURES

Articular cartilage samples were obtained. Tissue sulfated glycosaminoglycan (SGAG), collagen, and DNA concentrations were measured. Collagen, SGAG, chondroitin sulfate 846, NO, prostaglandin E2 (PGE2), and matrix metalloproteinase (MMP)-2, MMP-3, MMP-9, and MMP-13 concentrations in culture medium were analyzed. Aggrecan, collagen II, MMP-2, MMP-3, MMP-9, MMP-13, ADAM metallopeptidase with thrombospondin type 1 motif (ADAMTS)-4, ADAMTS-5, tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, TIMP-3, interleukin-1β, tumor necrosis factor-α, cyclooxygenase-1, cyclooxygenase-2, and inducible nitric oxide synthase gene expression were evaluated. Comparisons between tissues cultured without (control) and with meloxicam at concentrations of 0.3, 3.0, and 30.0 μg/mL for up to 30 days were performed by means of repeated-measures analysis.

RESULTS

Meloxicam had no effect on chondrocyte SGAG, collagen, or DNA concentrations. Expression of ADAMTS-5 was significantly decreased in all groups on all days, compared with the day 0 value. On day 3, culture medium PGE2 concentrations were significantly lower in all meloxicam-treated groups, compared with values for controls, and values remained low. Culture medium MMP-3 concentrations were significantly lower on day 30 than on day 3 in all meloxicam-treated groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that in vitro meloxicam treatment of osteoarthritic canine cartilage for up to 30 days did not induce matrix degradation or stimulate MMP production. Meloxicam lowered PGE2 release from this tissue, and effects on tissue chondrocyte content and matrix composition were neutral.