Polymeric Nanoparticles Enable mRNA Transfection and Its Translation in Intervertebral Disc and Human Joint Cells, Except for M1 Macrophages

Chronic lower back pain caused by intervertebral disc degeneration and osteoarthritis (OA) are highly prevalent chronic diseases. Although pain management and surgery can alleviate symptoms, no disease-modifying treatments are available. mRNA delivery could halt inflammation and degeneration and induce regeneration by overexpressing anti-inflammatory cytokines or growth factors involved in cartilage regeneration. Here, we investigated poly(amidoamine)-based polymeric nanoparticles to deliver mRNA to human joint and intervertebral disc cells. Human OA chondrocytes, human nucleus pulposus (NP) cells, human annulus fibrosus (AF) cells, fibroblast-like synoviocytes (FLS) and M1-like macrophages were cultured and transfected with uncoated or PGA-PEG-coated nanoparticles loaded with EGFP-encoding mRNA. Cell viability and transfection efficiency were analyzed for all cell types. Nanoparticle internalization was investigated in FLS and M1-like macrophages. No significant decrease in cell viability was observed in most conditions. Only macrophages showed a dose-dependent reduction of viability. Transfection with either nanoparticle version resulted in EGFP expression in NP cells, AF cells, OA chondrocytes and FLS. Macrophages showed internalization of nanoparticles by particle-cell co-localization, but no detectable expression of EGFP. Taken together, our data show that poly (amidoamine)-based nanoparticles can be used for mRNA delivery into cells of the human joint and intervertebral disc, indicating its potential future use as an mRNA delivery system in OA and IVDD, except for macrophages.

A Modular Albumin-Oligonucleotide Biomolecular Assembly for Delivery of Antisense Therapeutics

Antisense nucleic acid drugs are susceptible to nuclease degradation, rapid renal clearance, and short circulatory half-life. In this work, we introduce a modular-based recombinant human albumin-oligonucleotide (rHA-cODN) biomolecular assembly that allows incorporation of a chemically stabilized therapeutic gapmer antisense oligonucleotide (ASO) and FcRn-driven endothelial cellular recycling. A phosphodiester ODN linker (cODN) was conjugated to recombinant human albumin (rHA) using maleimide chemistry, after which a complementary gapmer ASO, targeting ADAMTS5 involved in osteoarthritis pathogenesis, was annealed. The rHA-cODN/ASO biomolecular assembly production, fluorescence labeling, and purity were confirmed using polyacrylamide gel electrophoresis. ASO release was triggered by DNase-mediated degradation of the linker strand, reaching 40% in serum after 72 h, with complete release observed following 30 min of incubation with DNase. Cellular internalization and trafficking of the biomolecular assembly using confocal microscopy in C28/I2 cells showed higher uptake and endosomal localization by increasing incubation time from 4 to 24 h. FcRn-mediated cellular recycling of the assembly was demonstrated in FcRn-expressing human microvascular endothelial cells. ADAMTS5 in vitro silencing efficiency reached 40%, which was comparable to free gapmer after 72 h incubation with human osteoarthritis patients' chondrocytes. This work introduces a versatile biomolecular modular-based "Plug-and-Play" platform potentially applicable for albumin-mediated half-life extension for a range of different types of ODN therapeutics.

A poly(amidoamine)-based polymeric nanoparticle platform for efficient in vivo delivery of mRNA

The successful use of mRNA vaccines enabled and accelerated the development of several new vaccine candidates and therapeutics based on the delivery of mRNA. In this study, we developed bioreducible poly(amidoamine)-based polymeric nanoparticles (PAA PNPs) for the delivery of mRNA with improved transfection efficiency. The polymers were functionalized with chloroquinoline (Q) moieties for improved endosomal escape and further stabilization of the mRNA-polymer construct. Moreover, these PAAQ polymers were covalently assembled around a core of multi-armed ethylenediamine (Mw 800, 2 % w/w) to form a pre-organized polymeric scaffolded PAAQ (ps-PAAQ) as a precursor for the formation of the mRNA-loaded nanoparticles. Transfection of mammalian cell lines with EGFP mRNA loaded into these PNPs showed a favorable effect of the Q incorporation on GFP protein expression. Additionally, these ps-PAAQ NPs were co-formulated with PEG-polymer coatings to shield the positive surface charge for increased stability and better in vivo applicability. The ps-PAAQ NPs coated with PEG-polymer displayed smaller particle size, electroneutral surface charge, and higher thermal stability. Importantly, these nanoparticles with both Q and PEG-polymer coating induced significantly higher luciferase activity in mice muscle than uncoated ps-PAAQ NPs, following intramuscular injection of PNPs loaded with luciferase mRNA. The developed technology is broadly applicable and holds promise for the development of new nucleotide-based vaccines and therapeutics in a range of infectious and chronic diseases.

Cell uptake and intracellular trafficking of bioreducible poly(amidoamine) nanoparticles for efficient mRNA translation in chondrocytes

Disulfide-containing poly(amidoamine) (PAA) is a cationic and bioreducible polymer, with potential use as a nanocarrier for mRNA delivery in the treatment of several diseases including osteoarthritis (OA). Successful transfection of joint cells with PAA-based nanoparticles (NPs) was shown previously, but cell uptake, endosomal escape and nanoparticle biodegradation were not studied in detail. In this study, C28/I2 human chondrocytes were transfected with NPs co-formulated with a PEG-polymer coating and loaded with EGFP mRNA for confocal imaging of intracellular trafficking and evaluation of transfection efficiency. Compared with uncoated NPs, PEG-coated NPs showed smaller particle size, neutral surface charge, higher colloidal stability and superior transfection efficiency. Furthermore, endosomal entrapment of these PEG-coated NPs decreased over time and mRNA release could be visualized both in vitro and in live cells. Importantly, cell treatment with modulators of the intracellular reducing environment showed that glutathione (GSH) concentrations affect translation of the mRNA payload. Finally, we applied a D-optimal experimental design to test different polymer-to-RNA loading ratios and dosages, thus obtaining an optimal formulation with up to ≈80% of GFP-positive cells and without toxic effects. Together, the biocompatibility and high transfection efficiency of this system may be a promising tool for intra-articular delivery of therapeutical mRNA in OA treatment.

Celecoxib alleviates nociceptor sensitization mediated by interleukin-1beta-primed annulus fibrosus cells

PURPOSE

This study aims to analyze the effect of pro-inflammatory cytokine-stimulated human annulus fibrosus cells (hAFCs) on the sensitization of dorsal root ganglion (DRG) cells. We further hypothesized that celecoxib (cxb) could inhibit hAFCs-induced DRG sensitization.

METHODS

hAFCs from spinal trauma patients were stimulated with TNF-α or IL-1β. Cxb was added on day 2. On day 4, the expression of pro-inflammatory and neurotrophic genes was evaluated using RT-qPCR. Levels of prostaglandin E2 (PGE-2), IL-8, and IL-6 were measured in the conditioned medium (CM) using ELISA. hAFCs CM was then applied to stimulate the DRG cell line (ND7/23) for 6 days. Then, calcium imaging (Fluo4) was performed to evaluate DRG cell sensitization. Both spontaneous and bradykinin-stimulated (0.5 μM) calcium responses were analyzed. The effects on primary bovine DRG cell culture were performed in parallel to the DRG cell line model.

RESULTS

IL-1ß stimulation significantly enhanced the release of PGE-2 in hAFCs CM, while this increase was completely suppressed by 10 µM cxb. hAFCs revealed elevated IL-6 and IL-8 release following TNF-α and IL-1β treatment, though cxb did not alter this. The effect of hAFCs CM on DRG cell sensitization was influenced by adding cxb to hAFCs; both the DRG cell line and primary bovine DRG nociceptors showed a lower sensitivity to bradykinin stimulation.

CONCLUSION

Cxb can inhibit PGE-2 production in hAFCs in an IL-1β-induced pro-inflammatory in vitro environment. The cxb applied to the hAFCs also reduces the sensitization of DRG nociceptors that are stimulated by the hAFCs CM.

Sustained release of locally delivered celecoxib provides pain relief for osteoarthritis: a proof of concept in dog patients

OBJECTIVE

Drug delivery platforms that allow for gradual drug release after intra-articular administration have become of much interest as a treatment strategy for osteoarthritis (OA). The aim of this study was to investigate the safety and efficacy of an intra-articular sustained release formulation containing celecoxib (CXB), a cyclooxygenase-2 (COX-2) selective inhibitor.

METHODS

Amino acid-based polyesteramide microspheres (PEAMs), a biodegradable and non-toxic platform, were loaded with CXB and employed in two in vivo models of arthritis: an acute inflammatory arthritis model in rats (n = 12), and a randomized controlled study in chronic OA dog patients (n = 30). In parallel, the bioactivity of sustained release of CXB was evaluated in monolayer cultures of primary dog chondrocytes under inflammatory conditions.

RESULTS

Sustained release of CXB did not alleviate acute arthritis signs in the rat arthritis model, based on pain measurements and synovitis severity. However, in OA dog patients, sustained release of CXB improved limb function as objective parameter of pain and quality of life based on gait analysis and owner questionnaires. It also decreased pain medication dependency over a 2-month period and caused no adverse effects. Prostaglandin E2 levels, a marker for inflammation, were lower in the synovial fluid of CXB-treated dog OA patients and in CXB-treated cultured dog chondrocytes.

CONCLUSION

These results show that local sustained release of CXB is less suitable to treat acute inflammation in arthritic joints, while safe and effective in treating pain in chronic OA in dogs.

Harmonization and standardization of nucleus pulposus cell extraction and culture methods

Background

In vitro studies using nucleus pulposus (NP) cells are commonly used to investigate disc cell biology and pathogenesis, or to aid in the development of new therapies. However, lab-to-lab variability jeopardizes the much-needed progress in the field. Here, an international group of spine scientists collaborated to standardize extraction and expansion techniques for NP cells to reduce variability, improve comparability between labs and improve utilization of funding and resources.

Methods

The most commonly applied methods for NP cell extraction, expansion, and re-differentiation were identified using a questionnaire to research groups worldwide. NP cell extraction methods from rat, rabbit, pig, dog, cow, and human NP tissue were experimentally assessed. Expansion and re-differentiation media and techniques were also investigated.

Results

Recommended protocols are provided for extraction, expansion, and re-differentiation of NP cells from common species utilized for NP cell culture.

Conclusions

This international, multilab and multispecies study identified cell extraction methods for greater cell yield and fewer gene expression changes by applying species-specific pronase usage, 60-100 U/ml collagenase for shorter durations. Recommendations for NP cell expansion, passage number, and many factors driving successful cell culture in different species are also addressed to support harmonization, rigor, and cross-lab comparisons on NP cells worldwide.

Intradiscal injection of human recombinant BMP-4 does not reverse intervertebral disc degeneration induced by nuclectomy in sheep

Background

Methods

Results

Conclusion

The Translational Potential of This Article

Hyperosmolar expansion medium improves nucleus pulposus cell phenotype

Background

Repopulating the degenerated intervertebral disc (IVD) with tissue‐specific nucleus pulposus cells (NPCs) has already been shown to promote regeneration in various species. Yet the applicability of NPCs as cell‐based therapy has been hampered by the low cell numbers that can be extracted from donor IVDs and their potentially limited regenerative capacity due to their degenerated phenotype. To optimize the expansion conditions, we investigated the effects of increasing culture medium osmolarity during expansion on the phenotype of dog NPCs and their ability to produce a healthy extracellular matrix (ECM) in a 3D culture model.

Methods

Dog NPCs were expanded in expansion medium with a standard osmolarity of 300 mOsm/L or adjusted to 400 or 500 mOsm/L in both normoxic and hypoxic conditions. Following expansion, NPCs were cultured in a 3D culture model in chondrogenic culture medium with a standard osmolarity. Read‐out parameters included cell proliferaton rate, morphology, phenotype and healthy ECM production.

Results

Increasing the expansion medium osmolarity from 300 to 500 mOsm/L resulted in NPCs with a more rounded morphology and a lower cell proliferation rate accompanied by the expression of several healthy NPC and progenitor markers at gene (KRT18, ACAN, COL2, CD73, CD90) and protein (ACAN, PAX1, CD24, TEK, CD73) level. The NPCs expanded at 500 mOsm/L were able to retain most of their phenotypic markers and produce healthy ECM during 3D culture independent of the oxygen level used during expansion.

Conclusions

Altogether, our findings show that increasing medium osmolarity during expansion results in an NPC population with improved phenotype, which could enhance the potential of cell‐based therapies for IVD regeneration.

The function of CD146 in human annulus fibrosus cells and mechanism of the regulation by TGF-β

The mouse outer annulus fibrosus (AF) was previously shown to contain CD146⁺ AF cells, while in vitro culture and exposure to transforming growth factor-beta (TGF-β) further increased the expression of CD146. However, neither the specific function of CD146 nor the underlying mechanism of TGF-β upregulation of CD146⁺ AF cells have been elucidated yet. In the current study, CD146 expression and its role in cultured human AF cells was investigated studying the cells' capacity for matrix contraction and gene expression of functional AF markers. In addition, TGF-β pathways were blocked by several pathway inhibitors and short hairpin RNAs (shRNAs) targeting SMAD and non-SMAD pathways to investigate their involvement in TGF-β-induced CD146 upregulation. Results showed that knockdown of CD146 led to reduction in AF cell-mediated collagen gel contraction, downregulation of versican and smooth muscle protein 22α (SM22α), and upregulation of scleraxis. TGF-β-induced CD146 upregulation was significantly blocked by inhibition of TGF-β receptor ALK5, and partially inhibited by shRNA against SMAD2 and SMAD4 and by an Protein Kinase B (AKT) inhibitor. Interestingly, the inhibition of extracellular signal-regulated kinases (ERK) pathway induced CD146 upregulation. In conclusion, CD146 was shown to be crucial to maintain the cell contractility of human AF cells in vitro. Furthermore, TGF-β upregulated CD146 via ALK5 signaling cascade, partially through SMAD2, SMAD4, and AKT pathway, whereas, ERK was shown to be a potential negative modulator. Our findings suggest that CD146 can potentially be used as a functional marker in AF repair strategies.

PLGA Nanoparticles Grafted with Hyaluronic Acid to Improve Site-Specificity and Drug Dose Delivery in Osteoarthritis Nanotherapy

Nanoparticles (NPs) have a tremendous potential in medicinal applications, and recent studies have pushed the boundaries in nanotherapy, including in osteoarthritis treatments. The aim of this study was to develop new poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) surfaces decorated with hyaluronic acid (HA) to enhance targeted drug specificity to the osteoarthritic knee joint. HA was selected since it binds to specific receptors expressed in many cells, such as the cluster determinant 44 (CD44), a major receptor of chondrocytes, and because of its function in the synovial fluid (SF), such as maintenance of high fluid viscosity. The PLGA polymer was grafted to sodium hyaluronate using dimethoxy-PEG (PLGA-HA) and compared with control PLGA NPs (not grafted). NPs were characterized by 1H-NMR and IR spectroscopy. Then, near-infrared (NIR) dye and gold (20 nm) were encapsulated in the formulated NPs and used to access NPs’ performance in in vitro, in vivo, and ex vivo experiments. To test the NPs’ CD44 receptor specificity, an antibody assay was performed. All NPs presented a size in the range viable for cell-uptake, no cytotoxicity to chondrocytes was registered. Although all the NPs had a high capacity to be absorbed by the cells, PLGA-HA NPs showed significantly higher affinity towards the chondrocytic C28/I2 cell line. In conclusion, PLGA NPs grafted to sodium hyaluronate showed increased binding to cartilage cells and tissue and enhanced accumulation at the target site. Thus, this study presents a safe drug-delivery system with improved receptor specificity, which may represent an advantageous alternative to current nanotherapies.

Intra-articular Administration of Triamcinolone Acetonide in a Murine Cartilage Defect Model Reduces Inflammation but Inhibits Endogenous Cartilage Repair

BACKGROUND

Cartilage defects result in joint inflammation. The presence of proinflammatory factors has been described to negatively affect cartilage formation.

PURPOSE

To evaluate the effect and timing of administration of triamcinolone acetonide (TAA), an anti-inflammatory drug, on cartilage repair using a mouse model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A full-thickness cartilage defect was created in the trochlear groove of 10-week-old male DBA/1 mice (N = 80). Mice received an intra-articular injection of TAA or saline on day 1 or 7 after induction of the defect. Mice were euthanized on days 10 and 28 for histological evaluation of cartilage defect repair, synovial inflammation, and synovial membrane thickness.

RESULTS

Mice injected with TAA had significantly less synovial inflammation at day 10 than saline-injected mice independent of the time of administration. At day 28, the levels of synovitis dropped toward healthy levels; nevertheless, the synovial membrane was thinner in TAA- than in saline-injected mice, reaching statistical significance in animals injected on day 1 (70.1 ± 31.9 µm vs 111.9 ± 30.9 µm, respectively; P = .01) but not in animals injected on day 7 (68.2 ± 21.86 µm vs 90.2 ± 21.29 µm, respectively; P = .26). A thinner synovial membrane was moderately associated with less filling of the defect after 10 and 28 days (r = 0.42, P = .02; r = 0.47, P = .01, respectively). Whereas 10 days after surgery there was no difference in the area of the defect filled and the cell density in the defect area between saline- and TAA-injected knees, filling of the defect at day 28 was lower in TAA- than in saline-injected knees for both injection time points (day 1 injection, P = .04; day 7 injection, P = .01). Moreover, there was less collagen type 2 staining in the filled defect area in TAA- than in saline-injected knees after 28 days, reaching statistical significance in day 1-injected knees (2.6% vs 18.5%, respectively; P = .01) but not in day 7-injected knees (7.4% vs 15.8%, respectively; P = .27).

CONCLUSION

Intra-articular injection of TAA reduced synovial inflammation but negatively affected cartilage repair. This implies that inhibition of inflammation may inhibit cartilage repair or that TAA has a direct negative effect on cartilage formation.

CLINICAL RELEVANCE

Our findings show that TAA can inhibit cartilage defect repair. Therefore, we suggest not using TAA to reduce inflammation in a cartilage repair setting.

The Added Value of the “Co” in Co-Culture Systems in Research on Osteoarthritis Pathology and Treatment Development

Osteoarthritis (OA) is a highly prevalent disease and a major health burden. Its development and progression are influenced by factors such as age, obesity or joint overuse. As a whole organ disease OA affects not only cartilage, bone and synovium but also ligaments, fatty or nervous tissue surrounding the joint. These joint tissues interact with each other and understanding this interaction is important in developing novel treatments. To incorporate and study these interactions in OA research, several co-culture models have evolved. They combine two or more cell types or tissues and investigate the influence of amongst others inflammatory or degenerative stimuli seen in OA. This review focuses on co-cultures and the differential processes occurring in a given tissue or cell as a consequence of being combined with another joint cell type or tissue, and/or the extent to which a co-culture mimics the in vivo processes. Most co-culture models depart from synovial lining and cartilage culture, but also fat pad and bone have been included. Not all of the models appear to reflect the postulated in vivo OA pathophysiology, although some of the discrepancies may indicate current assumptions on this process are not entirely valid. Systematic analysis of the mutual influence the separate compartments in a given model exert on each other and validation against in vivo or ex vivo observation is still largely lacking and would increase their added value as in vitro OA models.

Comparison of annulus fibrosus cell collagen remodeling rates in a microtissue system

It has been suggested that curvature progression in adolescent idiopathic scoliosis occurs through irreversible changes in the intervertebral discs. Strains of mice have been identified who differ in their disc wedging response upon extended asymmetrical compression. Annulus fibrosus (AF) tissue remodeling could contribute to the faster disc wedging progression previously observed in these mice. Differences in collagen remodeling capacity of AF cells between these in-bred mice strains were compared using an in vitro microtissue system. AF cells of 8-10-week-old LG/J ("fast-healing") and C57BL/6J ("normal healing") mice were embedded in a microtissue platform and cultured for 48 h. Hereafter, tissues were partially released and cultured for another 96 h. Microtissue surface area and waistcoat contraction, collagen orientation, and collagen content were measured. After 96 h postrelease, microtissues with AF cells of LG/J mice showed more surface area contraction (p < .001) and waistcoat contraction (p = .002) than C57BL/6J microtissues. Collagen orientation did not differ at 24 h after partial release. However, at 96 h, collagen in the microtissues from LG/J AF cells was aligned more than in those from C57BL/6J mice (p < .001). Collagen content did not differ between microtissues at 96 h. AF cells of inbred LG/J mice were better able to remodel and realign their collagen fibers than those from C57BL/6J mice. The remodeling of AF tissue could be contributing to the faster disc wedging progression observed in LG/J mice.

Prospective Evaluation of Local Sustained Release of Celecoxib in Dogs with Low Back Pain

Back pain affects millions globally and in 40% of the cases is attributed to intervertebral disc degeneration. Oral analgesics are associated with adverse systemic side-effects and insufficient pain relief. Local drug delivery mitigates systemic effects and accomplishes higher local dosing. Clinical efficacy of intradiscally injected celecoxib (CXB)-loaded polyesteramide microspheres (PEAMs) was studied in a randomized prospective double-blinded placebo controlled veterinary study. Client-owned dog patients suffering from back pain were treated with CXB-loaded (n = 20) or unloaded PEAMs ("placebo") (n = 10) and evaluated by clinical examination, gait analysis, owners' questionnaires, and MRI at 6 and 12 weeks follow-up. At 6 and 12 weeks, CXB-treated dogs experienced significantly less pain interference with their daily life activities compared to placebo. The risk ratio for treatment success was 1.90 (95% C.I. 1.24-2.91, p = 0.023) at week 6 and 1.95 (95% C.I. 1.10-3.45, p = 0.036) at week 12. The beneficial effects of CXB-PEAMs were more pronounced for the subpopulation of male dogs and those with no Modic changes in MRI at inclusion in the study; disc protrusion did not affect the outcome. It remains to be determined whether intradiscal injection of CXB-PEAMs, in addition to analgesic properties, has the ability to halt the degenerative process in the long term or restore the disc.

Nanoghosts: Mesenchymal Stem cells derived nanoparticles as a unique approach for cartilage regeneration

Osteoarthritis (OA) is a chronic degenerative disease, which affects the joints and is characterized by inflammation, cartilage loss and bone changes. Nowadays, there are no treatments for OA, and current therapies are focused on relieving the symptoms. As a new therapy approach, micro and nanoparticles have been extensively explored and among all the studied particles, the use of cell-membrane-based particles is expanding. Another promising approach studied to treat OA, is the use of mesenchymal stem cells (MSCs) which play an important role modulating inflammation. We developed a novel kind of MSCs' cytoplasmic-membrane-based nanoparticles, termed nano-ghosts (NGs). Retaining MSCs' surface properties and lacking cells' internal machinery allow the NGs to have immunomodulatory capacity and to be immune-evasive while not susceptible to host-induced changes. In this study, we demonstrate NGs' ability to target cartilage tissues, in vitro and in vivo, while modulating the inflammatory process. In vivo studies demonstrated NGs ability to act as an immunomodulatory drug slowing down cartilage degeneration process. Our proof-of-concept experiments show that NGs system is a versatile nano-carrier system, capable of therapeutics loading, with targeting capabilities towards healthy and inflamed cartilage cells. Our results, along with previously published data, clearly reveal the NGs system as a promising nano-carrier platform and as a potential immunomodulatory drug for several inflammation-related diseases.

"Old Drugs, New Tricks" - Local controlled drug release systems for treatment of degenerative joint disease

Osteoarthritis (OA) and chronic low back pain (CLBP) caused by intervertebral disc (IVD) degeneration are joint diseases that have become major causes for loss of quality of life worldwide. Despite the unmet need, effective treatments other than invasive, and often ineffective, surgery are lacking. Systemic administration of drugs entails suboptimal local drug exposure in the articular joint and IVD. This review provides an overview of the potency of biomaterial-based drug delivery systems as novel treatment modality, with a focus on the biological effects of drug release systems that have reached translation at the level of in vivo models and relevant ex vivo models. These studies have shown encouraging results of biomaterial-based local delivery of several types of drugs, mostly inhibitors of inflammatory cytokines or other degenerative factors. Prevention of inflammation and degeneration and pain relief was achieved, although mainly in small animal models, with interventions applied at an early disease stage. Less convincing data were obtained with the delivery of regenerative factors. Multidisciplinary efforts towards tackling the discord between in vitro and in vivo release, combined with adaptations in the regulatory landscape may be needed to enhance safe and expeditious introduction of more and more effective controlled release-based treatments with the OA and CLBP patients.

Proinflammatory intervertebral disc cell and organ culture models induced by tumor necrosis factor alpha

Inflammation plays an important role in the pathogenesis of intervertebral disc (IVD) degeneration. The proinflammatory cytokine tumor necrosis factor alpha (TNF-α) has shown markedly higher expression in degenerated human disc tissue compared with healthy controls. Anti-inflammatory treatment targeting TNF-α has shown to alleviate discogenic pain in patients with low back pain. Therefore, in vitro and ex vivo inflammatory models utilizing TNF-α provide relevant experimental conditions for drug development in disc degeneration research. The current method article addressed several specific questions related to the model establishment. (a) The effects of bovine and human recombinant TNF-α on bovine nucleus pulposus (NP) cells were compared. (b) The required dose for an inflammatory IVD organ culture model with intradiscal TNF-α injection was studied. (c) The effect of TNF-α blocking at different stages of inflammation was evaluated. Outcomes revealed that bovine and human recombinant TNF-α induced equivalent inflammatory effects in bovine NP cells. A bovine whole IVD inflammatory model was established by intradiscal injection of 100 ng TNF-α/ cm3 disc volume, as indicated by increased nitric oxide, glycosaminoglycan, interleukin 6 (IL-6), and interleukin 8 (IL-8) release in culture media, and upregulation of MMP3, ADAMTS4, IL-8, IL-6, and cyclooxygenase (COX)-2 expression in NP tissue. However, results in human NP cells showed that the time point of anti-inflammatory treatment was crucial to achieve significant effects. Furthermore, anticatabolic therapy in conjunction with TNF-α inhibition would be required to slow down the pathologic cascade of disc degeneration.

Hedgehog proteins and parathyroid hormone-related protein are involved in intervertebral disc maturation, degeneration, and calcification

Parathyroid hormone-related protein (PTHrP) and hedgehog signaling play an important role in chondrocyte development, (hypertrophic) differentiation, and/or calcification, but their role in intervertebral disc (IVD) degeneration is unknown. Better understanding their involvement may provide therapeutic clues for low back pain due to IVD degeneration. Therefore, this study aimed to explore the role of PTHrP and hedgehog proteins in postnatal canine and human IVDs during the aging/degenerative process. The expression of PTHrP, hedgehog proteins and related receptors was studied during the natural loss of the notochordal cell (NC) phenotype during IVD maturation using tissue samples and de-differentiation in vitro and degeneration by real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry. Correlations between their expression and calcification levels (Alizarin Red S staining) were determined. In addition, the effect of PTHrP and hedgehog proteins on canine and human chondrocyte-like cells (CLCs) was determined in vitro focusing on the propensity to induce calcification. The expression of PTHrP, its receptor (PTHR1) and hedgehog receptors decreased during loss of the NC phenotype. N-terminal (active) hedgehog (Indian hedgehog/Sonic hedgehog) protein expression did not change during maturation or degeneration, whereas expression of PTHrP, PTHR1 and hedgehog receptors increased during IVD degeneration. Hedgehog and PTHR1 immunopositivity were increased in nucleus pulposus tissue with abundant vs no/low calcification. In vitro, hedgehog proteins facilitated calcification in CLCs, whereas PTHrP did not affect calcification levels. In conclusion, hedgehog and PTHrP expression is present in healthy and degenerated IVDs. Hedgehog proteins had the propensity to induce calcification in CLCs from degenerated IVDs, indicating that in the future, inhibiting hedgehog signaling could be an approach to inhibit calcification during IVD degeneration.

Dog as a Model for Osteoarthritis: The FGF4 Retrogene Insertion May Matter

Osteoarthritis (OA) is a degenerative joint disease associated with chronic pain and disability in humans and companion animals. The canine species can be subdivided into non-chondrodystrophic (NCD) and chondrodystrophic (CD) dogs, the latter having disproportionally short limbs due to disturbance in endochondral ossification of long bones. This phenotype is associated with retrogene insertions of the fibroblast growth factor 4 (FGF4) gene, resulting in enhanced fibroblast growth factor receptor 3 (FGFR3) signaling. The effect on cartilage is unknown and in experimental studies with dogs, breeds are seemingly employed randomly. The aim of this study was to determine whether CD- and NCD-derived cartilage differs on a structural and biochemical level, and to explore the relationship between FGF4 associated chondrodystrophy and OA. Cartilage explants from CD and NCD dogs were cultured for 21 days. Activation of canonical Wnt signaling was assessed in primary canine chondrocytes. OA and synovitis severity from an experimental OA model were compared between healthy and OA samples from CD and NCD dogs. Release of glycosaminoglycans, DNA content, and cyclooxygenase 2 (COX-2) expression were higher in NCD cartilage explants. Healthy cartilage from NCD dogs displayed higher cartilage degeneration and synovitis scores, which was aggravated by the induction of OA. Dikkopf-3 gene expression was higher in NCD cartilage. No differences in other Wnt pathway read outs were found. To conclude, chondrodystrophy associated with the FGF4 retrogene seems to render CD dogs less susceptible to the development of OA when compared with NCD dogs. These differences should be considered when choosing a canine model to study the pathobiology and new treatment strategies of OA. © 2019 The Authors. Journal of Orthopaedic Research^® Published by Wiley Periodicals, Inc. J Orthop Res 37:2550-2560, 2019.

Local controlled release of corticosteroids extends surgically induced joint instability by inhibiting tissue healing

Background and Purpose

Corticosteroids are intra‐articularly injected to relieve pain in joints with osteoarthritis (OA) or acute tissue damage such as ligament or tendon tears, despite its unverified contraindication in unstable joints. Biomaterial‐based sustained delivery may prolong reduction of inflammatory pain, while avoiding harmful peak drug concentrations.

Experimental Approach

The applicability of prolonged corticosteroid exposure was examined in a rat model of anterior cruciate ligament and medial meniscus transection (ACLT + pMMx) with ensuing degenerative changes.

Key Results

Intra‐articular injection of a bolus of the corticosteroid triamcinolone acetonide (TAA) resulted in enhanced joint instability in 50% of the joints, but neither instability‐induced OA cartilage degeneration, synovitis, nor the OA‐related bone phenotype was affected. However, biomaterial microsphere‐based extended TAA release enhanced instability in 94% of the animals and induced dystrophic calcification and exacerbation of cartilage degeneration. In healthy joints, injection with TAA releasing microspheres had no effect at all. In vitro, TAA inhibited cell migration out of joint tissue explants, suggesting inhibited tissue healing in vivo as mechanisms for enhanced instability and subsequent cartilage degeneration.

Conclusions and Implications

We conclude that short‐term TAA exposure has minor effects on surgically induced unstable joints, but its extended presence is detrimental by extending instability and associated joint degeneration through compromised healing. This supports a contraindication of prolonged corticosteroid exposure in tissue damage‐associated joint instability, but not of brief exposure.

Enhanced Sensitivity Using MALDI Imaging Coupled with Laser Postionization (MALDI-2) for Pharmaceutical Research

Visualizing the distributions of drugs and their metabolites is one of the key emerging application areas of matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) within pharmaceutical research. The success of a given MALDI-MSI experiment is ultimately determined by the ionization efficiency of the compounds of interest, which in many cases are too low to enable detection at relevant concentrations. In this work we have taken steps to address this challenge via the first application of laser-postionisation coupled with MALDI (so-called MALDI-2) to the analysis and imaging of pharmaceutical compounds. We demonstrate that MALDI-2 increased the signal intensities for 7 out of the 10 drug compounds analyzed by up to 2 orders of magnitude compared to conventional MALDI analysis. This gain in sensitivity enabled the distributions of drug compounds in both human cartilage and dog liver tissue to be visualized using MALDI-2, whereas little-to-no signal from tissue was obtained using conventional MALDI. This work demonstrates the vast potential of MALDI-2-MSI in pharmaceutical research and drug development and provides a valuable tool to broaden the application areas of MSI. Finally, in an effort to understand the ionization mechanism, we provide the first evidence that the preferential formation of [M + H]⁺ ions with MALDI-2 has no obvious correlation with the gas-phase proton affinity values of the analyte molecules, suggesting, as with MALDI, the occurrence of complex and yet to be elucidated ionization phenomena.

Fibrin-hyaluronic acid hydrogel-based delivery of antisense oligonucleotides for ADAMTS5 inhibition in co-delivered and resident joint cells in osteoarthritis

To date no disease-modifying drugs for osteoarthritis (OA) are available, with treatment limited to the use of pain killers and prosthetic replacement. The ADAMTS (A Disintegrin and Metallo Proteinase with Thrombospondin Motifs) enzyme family is thought to be instrumental in the loss of proteoglycans during cartilage degeneration in OA, and their inhibition was shown to reverse osteoarthritic cartilage degeneration. Locked Nucleic Acid (LNA)-modified antisense oligonucleotides (gapmers) released from biomaterial scaffolds for specific and prolonged ADAMTS inhibition in co-delivered and resident chondrocytes, is an attractive therapeutic strategy. Here, a gapmer sequence identified from a gapmer screen showed 90% ADAMTS5 silencing in a monolayer culture of human OA chondrocytes. Incorporation of the gapmer in a fibrin-hyaluronic acid hydrogel exhibited a sustained release profile up to 14 days. Gapmers loaded in hydrogels were able to transfect both co-embedded chondrocytes and chondrocytes in a neighboring gapmer-free hydrogel, as demonstrated by flow cytometry and confocal microscopy. Efficient knockdown of ADAMTS5 was shown up to 14 days in both cell populations, i.e. the gapmer-loaded and gapmer-free hydrogel. This work demonstrates the use applicability of a hydrogel as a platform for combined local delivery of chondrocytes and an ADAMTS-targeting gapmer for catabolic gene modulation in OA.

Controlled release of celecoxib inhibits inflammation, bone cysts and osteophyte formation in a preclinical model of osteoarthritis

Major hallmarks of osteoarthritis (OA) are cartilage degeneration, inflammation and osteophyte formation. COX-2 inhibitors counteract inflammation-related pain, but their prolonged oral use entails the risk for side effects. Local and prolonged administration in biocompatible and degradable drug delivery biomaterials could offer an efficient and safe treatment for the long-term management of OA symptoms. Therefore, we evaluated the disease-modifying effects and the optimal dose of polyesteramide microspheres delivering the COX-2 inhibitor celecoxib in a rat OA model. Four weeks after OA induction by anterior cruciate ligament transection and partial medial meniscectomy, 8-week-old female rats (n = 6/group) were injected intra-articular with celecoxib-loaded microspheres at three dosages (0.03, 0.23 or 0.39 mg). Unloaded microspheres served as control. During the 16-week follow-up, static weight bearing and plasma celecoxib concentrations were monitored. Post-mortem, micro-computed tomography and knee joint histology determined progression of synovitis, osteophyte formation, subchondral bone changes, and cartilage integrity. Systemic celecoxib levels were below the detection limit 6 days upon delivery. Systemic and local adverse effects were absent. Local delivery of celecoxib reduced the formation of osteophytes, subchondral sclerosis, bone cysts and calcified loose bodies, and reduced synovial inflammation, while cartilage histology was unaffected. Even though the effects on pain could not be evualated directly in the current model, our results suggest the application of celecoxib-loaded microspheres holds promise as novel, safe and effective treatment for inflammation and pain in OA.

Successful fishing for nucleus pulposus progenitor cells of the intervertebral disc across species

BACKGROUND

Recently, Tie2/TEK receptor tyrosine kinase (Tie2 or syn. angiopoietin-1 receptor) positive nucleus pulposus progenitor cells were detected in human, cattle, and mouse. These cells show remarkable multilineage differentiation capacity and direct correlation with intervertebral disc (IVD) degeneration and are therefore an interesting target for regenerative strategies. Nevertheless, there remains controversy over the presence and function of these Tie2+ nucleus pulposus cells (NPCs), in part due to the difficulty of identification and isolation.

PURPOSE

Here, we present a comprehensive protocol for sorting of Tie2+ NPCs from human, canine, bovine, and murine IVD tissue. We describe enhanced conditions for expansion and an optimized fluorescence-activated cell sorting-based methodology to sort and analyze Tie2+ NPCs.

METHODS

We present flow cytometry protocols to isolate the Tie2+ cell population for the aforementioned species. Moreover, we describe crucial pitfalls to prevent loss of Tie2+ NPCs from the IVD cell population during the isolation process. A cross-species phylogenetic analysis of Tie2 across species is presented.

RESULTS

Our protocols are efficient towards labeling and isolation of Tie2+ NPCs. The total flow cytometry procedure requires approximately 9 hours, cell isolation 4 to 16 hours, cell expansion can take up to multiple weeks, dependent on the application, age, disease state, and species. Phylogenetic analysis of the TEK gene revealed a strong homology among species.

CONCLUSIONS

Current identification of Tie2+ cells could be confirmed in bovine, canine, mouse, and human specimens. The presented flow cytometry protocol can successfully sort these multipotent cells. The biological function of isolated cells based on Tie2+ expression needs to be confirmed by functional assays such as in vitro differentiation. in vitro culture conditions to maintain and their possible proliferation of the Tie2+ fraction is the subject of future research.

Comparing Hydrogels for Human Nucleus Pulposus Regeneration: Role of Osmolarity During Expansion

Hydrogels can facilitate nucleus pulposus (NP) regeneration, either for clinical application or research into mechanisms of regeneration. However, many different hydrogels and culture conditions for human degenerated NP have been employed, making literature data difficult to compare. Therefore, we compared six different hydrogels of natural polymers and investigated the role of serum in the medium and of osmolarity during expansion or redifferentiation in an attempt to provide comparators for future studies. Human NP cells of Thompson grade III discs were cultured in alginate, agarose, fibrin, type II collagen, gelatin methacryloyl (gelMA), and hyaluronic acid-poly(ethylene glycol) hydrogels. Medium containing fetal bovine serum and a serum-free (SF) medium were compared in agarose, gelMA, and type II collagen hydrogels. Isolation and expansion of NP cells in low compared to high osmolarity medium were performed before culture in agarose and type II collagen hydrogels in media of varying osmolarity. NP cells in agarose produced the highest amounts of proteoglycans, followed by cells in type II collagen hydrogels. The absence of serum reduced the total amount of proteoglycans produced by the cells, although incorporation efficiency was higher in type II collagen hydrogels in the absence than in the presence of serum. Isolation and expansion of NP cells in high osmolarity medium improved proteoglycan production during culture in hydrogels, but variation in osmolarity during redifferentiation did not have any effect. Agarose hydrogels seem to be the best option for in vitro culture of human NP cells, but for clinical application, type II collagen hydrogels may be better because, as opposed to agarose, it degrades in time. Although culture in SF medium reduces the amount of proteoglycans produced during redifferentiation culture, isolating and expanding the cells in high osmolarity medium can largely compensate for this loss.

Intradiscal application of a PCLA-PEG-PCLA hydrogel loaded with celecoxib for the treatment of back pain in canines: What's in it for humans?

Chronic low back pain is a common clinical problem in both the human and canine population. Current pharmaceutical treatment often consists of oral anti-inflammatory drugs to alleviate pain. Novel treatments for degenerative disc disease focus on local application of sustained released drug formulations. The aim of this study was to determine safety and feasibility of intradiscal application of a poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-bpoly(ε-caprolactone-co-lactide) PCLA-PEG-PCLA hydrogel releasing celecoxib, a COX-2 inhibitor. Biocompatibility was evaluated after subcutaneous injection in mice, and safety of intradiscal injection of the hydrogel was evaluated in experimental dogs with early spontaneous intervertebral disc (IVD) degeneration. COX-2 expression was increased in IVD samples surgically obtained from canine patients, indicating a role of COX-2 in clinical IVD disease. Ten client-owned dogs with chronic low back pain related to IVD degeneration received an intradiscal injection with the celecoxib-loaded hydrogel. None of the dogs showed adverse reactions after intradiscal injection. The hydrogel did not influence magnetic resonance imaging signal at long-term follow-up. Clinical improvement was achieved by reduction of back pain in 9 of 10 dogs, as was shown by clinical examination and owner questionnaires. In 3 of 10 dogs, back pain recurred after 3 months. This study showed the safety and effectiveness of intradiscal injections in vivo with a thermoresponsive PCLA-PEG-PCLA hydrogel loaded with celecoxib. In this set-up, the dog can be used as a model for the development of novel treatment modalities in both canine and human patients with chronic low back pain.

Link-N: The missing link towards intervertebral disc repair is species-specific

Introduction

Degeneration of the intervertebral disc (IVD) is a frequent cause for back pain in humans and dogs. Link-N stabilizes proteoglycan aggregates in cartilaginous tissues and exerts growth factor-like effects. The human variant of Link-N facilitates IVD regeneration in several species in vitro by inducing Smad1 signaling, but it is not clear whether this is species specific. Dogs with IVD disease could possibly benefit from Link-N treatment, but Link-N has not been tested on canine IVD cells. If Link-N appears to be effective in canines, this would facilitate translation of Link-N into the clinic using the dog as an in vivo large animal model for human IVD degeneration.

Materials and methods

This study’s objective was to determine the effect of the human and canine variant of Link-N and short (s) Link-N on canine chondrocyte-like cells (CLCs) and compare this to those on already studied species, i.e. human and bovine CLCs. Extracellular matrix (ECM) production was determined by measuring glycosaminoglycan (GAG) content and histological evaluation. Additionally, the micro-aggregates’ DNA content was measured. Phosphorylated (p) Smad1 and -2 levels were determined using ELISA.

Results

Human (s)Link-N induced GAG deposition in human and bovine CLCs, as expected. In contrast, canine (s)Link-N did not affect ECM production in human CLCs, while it mainly induced collagen type I and II deposition in bovine CLCs. In canine CLCs, both canine and human (s)Link-N induced negligible GAG deposition. Surprisingly, human and canine (s)Link-N did not induce Smad signaling in human and bovine CLCs. Human and canine (s)Link-N only mildly increased pSmad1 and Smad2 levels in canine CLCs.

Conclusions

Human and canine (s)Link-N exerted species-specific effects on CLCs from early degenerated IVDs. Both variants, however, lacked the potency as canine IVD regeneration agent. While these studies demonstrate the challenges of translational studies in large animal models, (s)Link-N still holds a regenerative potential for humans.

A hyaluronic acid-based hydrogel enabling CD44-mediated chondrocyte binding and gapmer oligonucleotide release for modulation of gene expression in osteoarthritis

Hyaluronic acid (HA) is an attractive biomaterial for osteoarthritis (OA) treatment due to inherent functional and compatibility properties as an endogenous knee joint component. In this work, we describe a HA-based hydrogel with the dual functionality of increased CD44-dependent chondrocyte binding and controlled release of gapmer antisense oligonucleotides for unassisted cellular entry and subsequent gene silencing activity. A Schiff base-mediated gelation method was used to produce a panel of hydrogels varying in the aldehyde-modified HA (900kDa) to chitosan ratios (3:7, 5:5 and 7:3) for identifying designs displaying optimal engagement of OA patient-derived CD44-expressing chondrocytes. Correlation was found between cell binding and CD44 expression, with maximal binding exhibited at a HA/chitosan ratio of 7:3, that was 181% higher than CD44-negative MCF-7 cell control cells. Transfection agent-free uptake into OA chondrocytes of fluorescent 13-mer DNA oligonucleotides with a flanked locked nucleic acid (LNA) gapmer design, in contrast to naked siRNA, was demonstrated by confocal and flow cytometric analysis. A sustained and complete release over 5days was found with the 7:3 hydrogel, in contrast, the 5:5 and 3:7 hydrogel released 60% and 43% of loaded gapmers, respectively over the same period. A COX-2-specific gapmer designed with maximal chondrocyte gene silencing (~70% silencing efficiency at 500nM compared with a mismatch gapmer sequence) resulted in effective COX-2 silencing over 14days in hydrogels seeded with OA chondrocytes, with significant difference exhibited between day 3 and 10. This work introduces a novel HA-based CD44-mediated cellular binding and gapmer controlled release platform to modulate cellular gene expression.

Derivatization Strategies for the Detection of Triamcinolone Acetonide in Cartilage by Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging

Osteoarthritis (OA), characterized by degeneration of the cartilaginous tissue in articular joints, severely impairs mobility in many people worldwide. The degeneration is thought to be mediated by inflammatory processes occurring in the tissue of the joint, including the cartilage. Intra-articular administered triamcinolone acetonide (TAA) is one of the drug treatments employed to ameliorate the inflammation and pain that characterizes OA. However, the penetration and distribution of TAA into the avascular cartilage is not well understood. We employed matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), which has been previously used to directly monitor the distribution of drugs in biological tissues, to evaluate the distribution of TAA in human cartilage after in vitro incubation. Unfortunately, TAA is not easily ionized by regular electrospray ionization (ESI) or MALDI. To overcome this problem, we developed an on-tissue derivatization method with Girard's reagent T (GirT) in human incubated cartilage being able to study its distribution and quantify the drug abundance (up to 3.3 ng/μL). Our results demonstrate the depth of penetration of a corticosteroid drug in human OA cartilage using MALDI-MSI.

Soluble and pelletable factors in porcine, canine and human notochordal cell-conditioned medium: implications for IVD regeneration

During intervertebral disc (IVD) maturation, notochordal cells (NCs) are replaced by chondrocyte-like cells (CLCs) in the nucleus pulposus, suggesting that NCs play a role in maintaining tissue health. Affirmatively, NC-conditioned medium (NCCM) exerts regenerative effects on CLC proliferation and extracellular matrix (ECM) production. The aim of this study was to identify NC-secreted substances that stimulate IVD regeneration. By mass spectrometry of porcine, canine and human NCCM, 149, 170 and 217 proteins were identified, respectively, with 66 proteins in common. Mainly ECM-related proteins were identified, but also organelle-derived and membrane-bound vesicle proteins. To determine whether the effect of NCCM was mediated by soluble and/or pelletable factors, porcine and canine NCCM were separated into a soluble (NCCM-S; peptides and proteins) and pelletable (NCCM-P; protein aggregates and extracellular vesicles) fraction by ultracentrifugation, and tested on bovine and canine CLCs in vitro, respectively. In each model, NCCM-S exerted a more pronounced anabolic effect than NCCM-P. However, glycosaminoglycan (GAG) uptake from the medium into the carrier gel prevented more definite conclusions. While the effect of porcine NCCM-P on bovine CLCs was negligible, canine NCCM-P appeared to enhance GAG and collagen type II deposition by canine CLCs. In conclusion, porcine and canine NCCM exerted their anabolic effects mainly through soluble factors, but also the pelletable NCCM factors showed moderate regenerative potential. Although the regenerative potential of NCCM-P should not be overlooked, future studies should focus on unraveling the protein-based regenerative mechanism from NCCM produced from isolated NCs, e.g. by NCCM fractionation and pathway blocking studies.

Class 3 semaphorins expression and association with innervation and angiogenesis within the degenerate human intervertebral disc

Nerve and blood vessel ingrowth during intervertebral disc degeneration, is thought to be a major cause of low back pain, however the regulation of this process is poorly understood. Here, we investigated the expression and regulation of a subclass of axonal guidance molecules known as the class 3 semaphorins, and their receptors; plexins and neuropilins within human NP tissue and their regulation by pro-inflammatory cytokines. Importantly this determined whether semaphorin expression was associated with the presence of nerves and blood vessels in tissues from human intervertebral discs. The study demonstrated that semaphorin3A, 3C, 3D, 3E and 3F and their receptors were expressed by native NP cells and further demonstrated their expression was regulated by IL-1β but to a lesser extent by IL-6 and TNFα. This is the first study to identify sema3C, sema3D and their receptors within the nucleus pulposus of intervertebral discs. Immunopositivity shows significant increases in semaphorin3C, 3D and their receptor neuropilin-2 in degenerate samples which were shown to contain nerves and blood vessels, compared to non-degenerate samples without nerves and blood vessels. Therefore data presented here suggests that semaphorin3C may have a role in promoting innervation and vascularisation during degeneration, which may go on to cause low back pain.

Increased caveolin-1 in intervertebral disc degeneration facilitates repair

Background

Preceding intervertebral disc (IVD) degeneration, the cell phenotype in the nucleus pulposus (NP) shifts from notochordal cells (NCs) to chondrocyte-like cells (CLCs). Microarray analysis showed a correlation between caveolin-1 expression and the phenotypic transition of NCs to CLCs. With a clinical directive in mind, the aim of this study was to determine the role of caveolin-1 in IVD degeneration. As a scaffolding protein, caveolin-1 influences several signaling pathways, and transforming growth factor (TGF)-β receptors have been demonstrated to colocalize with caveolin-1. Therefore, the hypothesis of this study was that caveolin-1 facilitates repair by enhancing TGF-β signaling in the IVD.

Methods

Protein expression (caveolin-1, apoptosis, progenitor cell markers, extracellular matrix, and phosphorylated Smad2 [pSmad2]) was determined in IVDs of wild-type (WT) and caveolin-1-null mice and canine IVDs of different degeneration grades (immunofluorescence, immunohistochemistry, and TUNEL assay). Canine/human CLC microaggregates were treated with chondrogenic medium alone or in combination with caveolin-1 scaffolding domain (CSD) peptide and/or caveolin-1 silencing RNA. After 28 days, gene and protein expression profiles were determined.

Results

The NP of WT mice was rich in viable NCs, whereas the NP of caveolin-1-null mice contained more collagen-rich extracellular matrix and fewer cells, together with increased progenitor cell marker expression, pSmad2 TGF-β signaling, and high apoptotic activity. During canine IVD degeneration, caveolin-1 expression and apoptotic activity increased. In vitro caveolin-1 silencing decreased the CLC microaggregate glycosaminoglycan (GAG) content, which could be rescued by CSD treatment. Furthermore, CSD increased TGF-β/pSmad2 signaling at gene and protein expression levels and enhanced the anabolic effects of TGF-β₁, reflected in increased extracellular matrix deposition by the CLCs.

Conclusions

Caveolin-1 plays a role in preservation of the NC phenotype. Additionally, it may be related to CLC apoptosis, given its increased expression in degenerated IVDs. Nevertheless, CSD enhanced CLC GAG deposition in vitro, and hence the increased caveolin-1 expression during IVD degeneration may also facilitate an ultimate attempt at repair. Further studies are needed to investigate how caveolin-1 modifies other signaling pathways and facilitates IVD repair.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0960-y) contains supplementary material, which is available to authorized users.

Nucleus pulposus phenotypic markers to determine stem cell differentiation: fact or fiction?

Progress in mesenchymal stem cell (MSC) based therapies for nucleus pulposus (NP) regeneration are hampered by a lack of understanding and consensus of the normal NP cell phenotype. Despite the recent consensus paper on NP markers, there is still a need to further validate proposed markers. This study aimed to determine whether an NP phenotypic profile could be identified within a large population of mature NP samples.qRT-PCR was conducted to assess mRNA expression of 13 genes within human non-degenerate articular chondrocytes (AC) (n=10) and NP cells extracted from patients across a spectrum of histological degeneration grades (n=71). qRT-PCR results were used to select NP marker candidates for protein expression analysis.Differential expression at mRNA between AC and non-degenerate NP cells was only observed for Paired Box Protein 1 (PAX1) and Forkhead box F1 (FOXF1). In contrast no other previously suggested markers displayed differential expression between non-degenerate NP and AC at mRNA level. PAX1 and FOXF1 protein expression was significantly higher in the NP compared to annulus fibrosus (AF), cartilaginous endplate (CEP) and AC. In contrast Laminin-5 (LAM-332), Keratin-19 (KRT-19) and Hypoxia Inducible Factor 1 alpha (HIF1α) showed no differential expression in NP cells compared with AC cells.A marker which exclusively differentiates NP cells from AF and AC cells remains to be identified, raising the question: is the NP a heterogeneous population of cells? Or does the natural biological variation during IVD development, degeneration state and even the life cycle of cells make finding one definitive marker impossible?

Inflammatory profiles in canine intervertebral disc degeneration

Background

Intervertebral disc (IVD) disease is a common spinal disorder in dogs and degeneration and inflammation are significant components of the pathological cascade. Only limited studies have studied the cytokine and chemokine profiles in IVD degeneration in dogs, and mainly focused on gene expression. A better understanding is needed in order to develop biological therapies that address both pain and degeneration in IVD disease. Therefore, in this study, we determined the levels of prostaglandin E2 (PGE₂), cytokines, chemokines, and matrix components in IVDs from chondrodystrophic (CD) and non-chondrodystrophic (NCD) dogs with and without clinical signs of IVD disease, and correlated these to degeneration grade (according to Pfirrmann), or herniation type (according to Hansen). In addition, we investigated cyclooxygenase 2 (COX-2) expression and signs of inflammation in histological IVD samples of CD and NCD dogs.

Results

PGE₂ levels were significantly higher in the nucleus pulposus (NP) of degenerated IVDs compared with non-degenerated IVDs, and in herniated IVDs from NCD dogs compared with non-herniated IVDs of NCD dogs. COX-2 expression in the NP and annulus fibrosus (AF), and proliferation of fibroblasts and numbers of macrophages in the AF significantly increased with increased degeneration grade. GAG content did not significantly change with degeneration grade or herniation type. Cytokines interleukin (IL)-2, IL-6, IL-7, IL-8, IL-10, IL-15, IL-18, immune protein (IP)-10, tumor necrosis factor (TNF)-α, and granulocyte macrophage colony-stimulating factor (GM-CSF) were not detectable in the samples. Chemokine (C-C) motif ligand (CCL)2 levels in the NP from extruded samples were significantly higher compared with the AF of these samples and the NP from protrusion samples.

Conclusions

PGE₂ levels and CCL2 levels in degenerated and herniated IVDs were significantly higher compared with non-degenerated and non-herniated IVDs. COX-2 expression in the NP and AF and reactive changes in the AF increased with advancing degeneration stages. Although macrophages invaded the AF as degeneration progressed, the production of inflammatory mediators seemed most pronounced in degenerated NP tissue. Future studies are needed to investigate if inhibition of PGE₂ levels in degenerated IVDs provides effective analgesia and exerts a protective role in the process of IVD degeneration and the development of IVD disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0635-6) contains supplementary material, which is available to authorized users.

Nerves are more abundant than blood vessels in the degenerate human intervertebral disc

BACKGROUND

Chronic low back pain (LBP) is the most common cause of disability worldwide. New ideas surrounding LBP are emerging that are based on interactions between mechanical, biological and chemical influences on the human IVD. The degenerate IVD is proposed to be innervated by sensory nerve fibres and vascularised by blood vessels, and it is speculated to contribute to pain sensation. However, the incidence of nerve and blood vessel ingrowth, as well as whether these features are always associated, is unknown. We investigated the presence of nerves and blood vessels in the nucleus pulposus (NP) of the IVD in a large population of human discs.

METHODS

Immunohistochemistry was performed with 61 human IVD samples, to identify and localise nerves (neurofilament 200 [NF200]/protein gene product 9.5) and blood vessels (CD31) within different regions of the IVD.

RESULTS

Immunopositivity for NF200 was identified within all regions of the IVD within post-mortem tissues. Nerves were seen to protrude across lamellar ridges and through matrix towards NP cells. Nerves were identified deep within the NP and were in many cases, but not always, seen in close proximity to fissures or in areas where decreased matrix was seen. Fifteen percent of samples were degenerate and negative for nerves and blood vessels, whilst 16 % of all samples were degenerate with nerves and blood vessels. We identified 52% of samples that were degenerate with nerves but no blood vessels. Interestingly, only 4% of all samples were degenerate with no nerves but positive for blood vessels. Of the 85 samples investigated, only 6 % of samples were non-degenerate without nerves and blood vessels and 7% had nerves but no blood vessels.

CONCLUSIONS

This study addresses the controversial topic of nerve and blood vessel ingrowth into the IVD in a large number of human samples. Our findings demonstrate that nerves are present within a large proportion of NP samples from degenerate IVDs. This study shows a possible link between nerve ingrowth and degeneration of the IVD and suggests that nerves can migrate in the absence of blood vessels.

Safety of intradiscal injection and biocompatibility of polyester amide microspheres in a canine model predisposed to intervertebral disc degeneration

Repair of degenerated intervertebral discs (IVD) might be established via intradiscal delivery of biologic therapies. Polyester amide polymers (PEA) were evaluated for in vitro cytotoxicity and in vivo biocompatibility, and thereafter intradiscal application of PEA microspheres (PEAMs) in a canine model predisposed to IVD degeneration at long-term (6 months) follow-up. PEA extracts did not induce cytotoxicity in mouse fibroblast cells (microscopy and XTT assay), while a slight foreign body reaction was demonstrated by histopathology after intramuscular implantation in rabbits. Intradiscal injection of a volume of 40 µL through 26 and 27G needles induced no degenerative changes in acanine model susceptible to IVD disease. Although sham-injected IVDs showed increased CAV1 expression compared with noninjected IVDs, which may indicate increased cell senescence, these findings were not supported by immunohistochemistry, biomolecular analysis of genes related to apoptosis, biochemical and histopathological results. PEAM-injected IVDs showed significantly higher BAX/BCL2 ratio vs sham-injected IVDs suggestive of an anti-apoptotic effect of the PEAMs. These findings were not supported by other analyses (clinical signs, disc height index, T2 values, biomolecular and biochemical analyses, and IVD histopathology). PEAs showed a good cytocompatibility and biocompatibility. PEAMs are considered safe sustained release systems for intradiscal delivery of biological treatments. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 707-714, 2017.

Osteogenic protein 1 does not stimulate a regenerative effect in cultured human degenerated nucleus pulposus tissue

Low back pain is a major cause of disability and is heavily associated with intervertebral disc degeneration. Osteogenic protein 1 (OP-1) is a growth factor that has shown potential to regenerate the intervertebral disc in human cells and animal models. However, high doses are required, presumably due to clearance from the tissue; controlled release may be a solution to this problem. In this study, we developed a preclinical, pathophysiological human tissue explant culture model of degenerated nucleus pulposus (NP). The NP explants were cultured for 28 days and injected with 100 µg OP-1 as a bolus, or with sustained-release biodegradable microspheres loaded with 16 or 1.6 µg OP-1. After culture, the tissue explants were analysed for biochemical content [water, sulphated glycosaminoglycans (GAGs), hydroxyproline and DNA], histology, cell viability and gene expression (disc matrix anabolic and catabolic markers). Untreated degenerated NP explants lost some of their GAG content when cultured for 4 weeks, but maintained other tissue constituents. Gene expression levels were close to native values. A bolus injection of OP-1 partially restored GAG content to the native level in half of the donors, while the sustained release of OP-1 did not affect the NP explants. No effect of treatment was observed on anabolic or catabolic gene expression at day 28. These results demonstrated that the regenerative potential of OP-1 is donor dependent, and only at very high doses. This questions the clinical use of OP-1 as a regenerative agent, as these high doses may increase the incidence of complications. Copyright © 2015 John Wiley & Sons, Ltd.

Biomaterials for intervertebral disc regeneration: past performance and possible future strategies

Intervertebral disc (IVD) degeneration is associated with most cases of cervical and lumbar spine pathologies, amongst which chronic low back pain has become the number one cause of loss of quality-adjusted life years. In search of alternatives to the current less than optimal and usually highly invasive treatments, regenerative strategies are being devised, none of which has reached clinical practice as yet. Strategies include the use of stem cells, gene therapy, growth factors and biomaterial carriers. Biomaterial carriers are an important component in musculoskeletal regenerative medicine techniques. Several biomaterials, both from natural and synthetic origin, have been used for regeneration of the IVD in vitro and in vivo. Aspects such as ease of use, mechanical properties, regenerative capacity, and their applicability as carriers for regenerative and anti-degenerative factors determine their suitability for IVD regeneration. The current review provides an overview of the biomaterials used with respect to these properties, including their drawbacks. In addition, as biomaterial application until now appears to have been based on a mix of mere availability and intuition, a more rational design is proposed for future use of biomaterials for IVD regeneration. Ideally, high-throughput screening is used to identify optimally effective materials, or alternatively medium content comparative studies should be carried out to determine an appropriate reference material for future studies on novel materials.

The species-specific regenerative effects of notochordal cell-conditioned medium on chondrocyte-like cells derived from degenerated human intervertebral discs

During intervertebral disc (IVD) maturation, the main cell type shifts from notochordal cells (NCs) to chondrocyte-like cells (CLCs). NCs secrete factors with regenerative potential, making them an interesting focus for regenerative treatments. During initial development, these strategies preferably employ non-human donors due to easy availability of their NC-rich nucleus pulposus (NP) tissue. To increase the success of translating these strategies for clinical application, this study aimed to delineate whether NC-secreted factors of different species have a regenerative effect on human CLCs. Human, canine and porcine NC-rich NP tissue and NC-conditioned medium (NCCM) were analysed biochemically and histologically. Human CLC micro-aggregates from degenerated IVDs were cultured in human, canine or porcine NCCM. Collagen, glycosaminoglycan (GAG) and DNA content was determined and histology was performed. Canine and porcine NPs were richer in NCs than human NPs. Human NPs contained the highest collagen content, whereas the DNA and GAG content of canine NPs was significantly higher than that of human or porcine NPs. NCCM from all species significantly increased the DNA and GAG content of the human CLC micro-aggregates. Porcine and canine NCCM were significantly more potent than human NCCM in inducing GAG deposition, whereas only human NCCM induced collagen type II production. Secreted factors from human, canine and porcine NC-rich NPs exerted regenerative effects on human CLCs, indicating a cross-species effect. Bioactive compound(s) are present in NCCM of different species that may reverse human IVD degeneration, supporting further research into strategies based on NC-technology employing canine or porcine models for their translation into humans.

A novel injectable thermoresponsive and cytocompatible gel of poly(N-isopropylacrylamide) with layered double hydroxides facilitates siRNA delivery into chondrocytes in 3D culture

Hybrid hydrogels composed of poly(N-isopropylacrylamide) (pNIPAAM) and layered double hydroxides (LDHs) are presented in this study as novel injectable and thermoresponsive materials for siRNA delivery, which could specifically target several negative regulators of tissue homeostasis in cartilaginous tissues. Effectiveness of siRNA transfection using pNIPAAM formulated with either MgAl-LDH or MgFe-LDH platelets was investigated using osteoarthritic chondrocytes. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as an endogenous model gene to evaluate the extent of silencing. No significant adverse effects of pNIPAAM/LDH hydrogels on cell viability were noticed. Cellular uptake of fluorescently labeled siRNA was greatly enhanced (>75%) in pNIPAAM/LDH hydrogel constructs compared to alginate, hyaluronan and fibrin gels, and was absent in pNIPAAM hydrogel without LDH platelets. When using siRNA against GAPDH, 82-98% reduction of gene expression was found in both types of pNIPAAM/LDH hydrogel constructs after 6 days of culturing. In the pNIPAAM/MgAl-LDH hybrid hydrogel, 80-95% of GAPDH enzyme activity was reduced in parallel with gene. Our findings show that the combination of a cytocompatible hydrogel and therapeutic RNA oligonucleotides is feasible. Thus it might hold promise in treating degeneration of cartilaginous tissues by providing supporting scaffolds for cells and interference with locally produced degenerative factors.

Biocompatibility and intradiscal application of a thermoreversible celecoxib-loaded poly-N-isopropylacrylamide MgFe-layered double hydroxide hydrogel in a canine model

Introduction

Chronic low back pain due to intervertebral disc (IVD) degeneration is associated with increased levels of inflammatory mediators. Current medical treatment consists of oral anti-inflammatory drugs to alleviate pain. In this study, the efficacy and safety of a novel thermoreversible poly-N-isopropylacrylamide MgFe-layered double hydroxide (pNIPAAM MgFe-LDH) hydrogel was evaluated for intradiscal controlled delivery of the selective cyclooxygenase (COX) 2 inhibitor and anti-inflammatory drug celecoxib (CXB).

Methods

Degradation, release behavior, and the ability of a CXB-loaded pNIPAAM MgFe-LDH hydrogel to suppress prostaglandin E₂ (PGE₂) levels in a controlled manner in the presence of a proinflammatory stimulus (TNF-α) were evaluated in vitro. Biocompatibility was evaluated histologically after subcutaneous injection in mice. Safety of intradiscal application of the loaded and unloaded hydrogels was studied in a canine model of spontaneous mild IVD degeneration by histological, biomolecular, and biochemical evaluation. After the hydrogel was shown to be biocompatible and safe, an in vivo dose–response study was performed in order to determine safety and efficacy of the pNIPAAM MgFe-LDH hydrogel for intradiscal controlled delivery of CXB.

Results

CXB release correlated to hydrogel degradation in vitro. Furthermore, controlled release from CXB-loaded hydrogels was demonstrated to suppress PGE₂ levels in the presence of TNF-α. The hydrogel was shown to exhibit a good biocompatibility upon subcutaneous injection in mice. Upon intradiscal injection in a canine model, the hydrogel exhibited excellent biocompatibility based on histological evaluation of the treated IVDs. Gene expression and biochemical analyses supported the finding that no substantial negative effects of the hydrogel were observed. Safety of application was further confirmed by the absence of clinical symptoms, IVD herniation or progression of degeneration. Controlled release of CXB resulted in a nonsignificant maximal inhibition (approximately 35 %) of PGE₂ levels in the mildly degenerated canine IVDs.

Conclusions

In conclusion, this study showed biocompatibility and safe intradiscal application of an MgFe LDH-pNIPAAM hydrogel. Controlled release of CXB resulted in only limited inhibition of PGE₂ in this model with mild IVD degeneration, and further studies should concentrate on application of controlled release from this type of hydrogel in animal models with more severe IVD degeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0727-x) contains supplementary material, which is available to authorized users.

Direct Cell-Cell Contact with Chondrocytes Is a Key Mechanism in Multipotent Mesenchymal Stromal Cell-Mediated Chondrogenesis

Using a combination of articular chondrocytes (ACs) and mesenchymal stromal cells (MSCs) has shown to be a viable option for a single-stage cell-based treatment of focal cartilage defects. However, there is still considerable debate whether MSCs differentiate or have a chondroinductive role through trophic factors. In addition, it remains unclear whether direct cell-cell contact is necessary for chondrogenesis. Therefore, the aim of this study was to investigate whether direct or indirect cell-cell contact between ACs and MSCs is essential for increased cartilage production in different cellular environments and elucidate the mechanisms behind these cellular interactions. Human ACs and MSCs were cultured in a 10:90 ratio in alginate beads, fibrin scaffolds, and pellets. Cells were mixed in direct cocultures, separated by a Transwell filter (indirect cocultures), or cultured with conditioned medium. Short tandem repeat analysis revealed that the percentages of ACs increased during culture, while those of MSCs decreased, with the biggest change in fibrin glue scaffolds. For alginate, where the lack of cell-cell contact could be confirmed by histological analysis, no difference was found in matrix production between direct and indirect cocultures. For fibrin scaffolds and pellet cultures, an increased glycosaminoglycan production and type II collagen deposition were found in direct cocultures compared with indirect cocultures and conditioned medium. Positive connexin 43 staining and transfer of cytosolic calcein indicated communication through gap junctions in direct cocultures. Taken together, these results suggest that MSCs stimulate cartilage formation when placed in close proximity to chondrocytes and that direct cell-cell contact and communication through gap junctions are essential in this chondroinductive interplay.

Intradiscal application of rhBMP-7 does not induce regeneration in a canine model of spontaneous intervertebral disc degeneration

INTRODUCTION

Strategies for biological repair and regeneration of the intervertebral disc (IVD) by cell and tissue engineering are promising, but few have made it into a clinical setting. Recombinant human bone morphogenetic protein 7 (rhBMP-7) has been shown to stimulate matrix production by IVD cells in vitro and in vivo in animal models of induced IVD degeneration. The aim of this study was to determine the most effective dose of an intradiscal injection of rhBMP-7 in a spontaneous canine IVD degeneration model for translation into clinical application for patients with low back pain.

METHODS

Canine nucleus pulposus cells (NPCs) were cultured with rhBMP-7 to assess the anabolic effect of rhBMP-7 in vitro, and samples were evaluated for glycosaminoglycan (GAG) and DNA content, histology, and matrix-related gene expression. Three different dosages of rhBMP-7 (2.5 μg, 25 μg, and 250 μg) were injected in vivo into early degenerated IVDs of canines, which were followed up for six months by magnetic resonance imaging (T2-weighted images, T1rho and T2 maps). Post-mortem, the effects of rhBMP-7 were determined by radiography, computed tomography, and macroscopy, and by histological, biochemical (GAG, DNA, and collagen), and biomolecular analyses of IVD tissue.

RESULTS

In vitro, rhBMP-7 stimulated matrix production of canine NPCs as GAG deposition was enhanced, DNA content was maintained, and gene expression levels of ACAN and COL2A1 were significantly upregulated. Despite the wide dose range of rhBMP-7 (2.5 to 250 μg) administered in vivo, no regenerative effects were observed at the IVD level. Instead, extensive extradiscal bone formation was noticed after intradiscal injection of 25 μg and 250 μg of rhBMP-7.

CONCLUSIONS

An intradiscal bolus injection of 2.5 μg, 25 μg, and 250 μg rhBMP-7 showed no regenerative effects in a spontaneous canine IVD degeneration model. In contrast, intradiscal injection of 250 μg rhBMP-7, and to a lesser extent 25 μg rhBMP-7, resulted in extensive extradiscal bone formation, indicating that a bolus injection of rhBMP-7 alone cannot be used for treatment of IVD degeneration in human or canine patients.

Osteoarthritis treatment using autologous conditioned serum after placebo

BACKGROUND AND PURPOSE

Autologous conditioned serum (ACS) is a disease-modifying drug for treatment of knee osteoarthritis, and modest superiority over placebo was reported in an earlier randomized controlled trial (RCT). We hypothesized that when given the opportunity, placebo-treated patients from that RCT would now opt for ACS treatment, which would result in a greater clinical improvement than placebo.

METHODS

Of 74 patients treated with placebo in the previous trial, 20 opted for ACS treatment. Patients who did not choose further treatment were interviewed about their reasons. Clinical improvement of the 20 ACS-treated patients was measured using knee-specific clinical scores, as was "response shift" at 3 and 12 months.

RESULTS

In the 20 patients who did opt for ACS, the visual analog scale (VAS) score for pain improved; but after 12 months, clinical results were similar to those after placebo treatment. Response shift measurement demonstrated that the 20 patients had adapted to their disabilities during treatment.

INTERPRETATION

Placebo-treated patients from an earlier trial were reluctant to undergo ACS treatment, in part due to the laborious nature of the therapy. In a subset of patients who opted for treatment, ACS treatment after placebo did not result in greater clinical improvement than placebo treatment only. However, due to the limited power of the current study and possible selection bias, definite advice on using or refraining from ACS cannot be given.

Enhanced cell-induced articular cartilage regeneration by chondrons; the influence of joint damage and harvest site

OBJECTIVE

Interactions between chondrocytes and their native pericellular matrix provide optimal circumstances for regeneration of cartilage. However, cartilage diseases such as osteoarthritis change the pericellular matrix, causing doubt to them as a cell source for autologous cell therapy.

METHODS

Chondrons and chondrocytes were isolated from stifle joints of goats in which cartilage damage was surgically induced in the right knee. After 4 weeks of regeneration culture, DNA content and proteoglycan and collagen content and release were determined.

RESULTS

The cartilage regenerated by chondrons isolated from the damaged joint contained less proteoglycans and collagen compared to chondrons from the same harvest site in the nonoperated knee (P < 0.01). Besides, chondrons still reflected whether they were isolated from a damaged joint, even if they where isolated from the opposing or adjacent condyle. Although chondrocytes did not reflect this diseased status of the joint, chondrons always outperformed chondrocytes, even when isolated from the damaged joints (P < 0.0001). Besides increased cartilage production, the chondrons showed less collagenase activity compared to the chondrocytes.

CONCLUSION

Chondrons still outperform chondrocytes when they were isolated from a damaged joint and they might be a superior cell source for articular cartilage repair and cell-induced cartilage formation.

Cytokine profiles in the joint depend on pathology, but are different between synovial fluid, cartilage tissue and cultured chondrocytes

Introduction

This study aimed to evaluate whether profiles of several soluble mediators in synovial fluid and cartilage tissue are pathology-dependent and how their production is related to in vitro tissue formation by chondrocytes from diseased and healthy tissue.

Methods

Samples were obtained from donors without joint pathology (n = 39), with focal defects (n = 65) and osteoarthritis (n = 61). A multiplex bead assay (Luminex) was performed measuring up to 21 cytokines: Interleukin (IL)-1α, IL-1β, IL-1RA, IL-4, IL-6, IL-6Rα, IL-7, IL-8, IL-10, IL-13, tumor necrosis factor (TNF)α, Interferon (IFN)γ, oncostatin M (OSM), leukemia inhibitory factor (LIF), adiponectin, leptin, monocyte chemotactic factor (MCP)1, RANTES, basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), vascular growth factor (VEGF).

Results

In synovial fluid of patients with cartilage pathology, IL-6, IL-13, IFNγ and OSM levels were higher than in donors without joint pathology (P ≤0.001). IL-13, IFNγ and OSM were also different between donors with cartilage defects and OA (P <0.05). In cartilage tissue from debrided defects, VEGF was higher than in non-pathological or osteoarthritic joints (P ≤0.001). IL-1α, IL-6, TNFα and OSM concentrations (in ng/ml) were markedly higher in cartilage tissue than in synovial fluid (P <0.01). Culture of chondrocytes generally led to a massive induction of most cytokines (P <0.001). Although the release of inflammatory cytokines was also here dependent on the pathological condition (P <0.001) the actual profiles were different from tissue or synovial fluid and between non-expanded and expanded chondrocytes. Cartilage formation was lower by healthy unexpanded chondrocytes than by osteoarthritic or defect chondrocytes.

Conclusions

Several pro-inflammatory, pro-angiogenic and pro-repair cytokines were elevated in joints with symptomatic cartilage defects and/or osteoarthritis, although different cytokines were elevated in synovial fluid compared to tissue or cells. Hence a clear molecular profile was evident dependent on disease status of the joint, which however changed in composition depending on the biological sample analysed. These alterations did not affect in vitro tissue formation with these chondrocytes, as this was at least as effective or even better compared to healthy chondrocytes.

Soluble mediators in posttraumatic wrist and primary knee osteoarthritis

BACKGROUND

New discoveries about the pathophysiology changed the concept that all forms of osteoarthritis are alike; this lead to the delineation of different phenotypes such as age, trauma or obese related forms. We aim to compare soluble mediator profiles in primary knee and posttraumatic wrist osteoarthritis. Based on the general faster progression rate of wrist osteoarthritis, we hypothesize a more inflammatory profile.

METHODS

We collected synovial fluid from 20 primary osteoarthritic knee and 20 posttraumatic osteoarthritic wrist joints. 17 mediators were measured by multiplex enzyme-linked immunosorbent assay: chemokine ligand 5, interferon-γ, leukemia inhibitory factor, oncostatin-M, osteoprotegerin, tumor necrosis factor-α, vascular endothelial growth factor, interleukin (IL)-1α, IL-1β, IL-1 receptor antagonist, IL-4, IL-6, IL-7, IL-8, IL-10, IL-13 and IL-17.

RESULTS

TEN MEDIATORS WERE HIGHER IN POSTTRAUMATIC OSTEOARTHRITIC SYNOVIAL FLUID: tumor necrosis factor-α (TNFα), IL-1α, IL-1RA, IL-6, IL-10, IL-17, oncostatin-M, interferon-γ, chemokine ligand 5 and leukemia inhibitory factor (P<0.001). IL-1ß, IL-4, IL-7 were not detected, TNFα was not detected in knee osteoarthritic synovial fluid. IL-8, IL-13, osteoprotegerin and vascular endothelial growth factor levels did not differ between the synovial fluid types.

CONCLUSIONS

In general wrist osteoarthritis seems characterized by a stronger inflammatory response than primary knee osteoarthritis. More pronounced inflammatory mediators might offer a paradigm for the faster progression of posttraumatic osteoarthritis. Increase of specific mediators could form a possible target for future mediator modulating therapy in wrist osteoarthritis.