The sternocleidomastoid muscle variations: a mini literature review.

The sternocleidomastoid muscles (SCM) are prominent paired muscles of the neck connecting proximally the manubrium sterni and the clavicle to the mastoid process and the occipital bone distally. Following their points of attachment sternomastoid, sternooccipital, cleidomastoid and cleidooccipital portions of this muscle have been described. Altogether 23 case reports from year 2000 till 2020 with 29 subjects related to the SCM supernumerary variations were searched and analysed where parameters such as supernumerary proximal variation types (sternal vs. clavicular), insertional variation, unilaterality/bilaterality of the variation, study type, reported gender of the subjects and the country of research were extracted. The research shows that 48.3% of the subjects had bilateral presentation of SCM variations. If present unilaterally, three quarters of the cases were on the left side. The most frequent variation is located at the clavicular side of the proximal SCM head whereas isolated sternal sided proximal head variation or an insertional variation alone are very rare. Interestingly, with 96.6%, most of cases in the literature were discovered in cadavers during anatomical dissections. Male gender represented with 82.8% higher prevalence than females. The higher male prevalence in the body donor system, predominantly in the Asian continent could play a decisive role in the outcome as more than half of the reported cases stemmed from India in this period. Importantly, the knowledge of different anatomical variations of the SCM is highly relevant for surgical, clinical or radiological approaches in the neck.

A unilateral sternopharyngeal branch of the sternocleidomastoid muscle in an aged Caucasian male: a unique cadaveric report.

The sternocleidomastoid muscle (SCM) consists of a sternal and a clavicular head which merge together and inserts distally posterolateral on the mastoid process and superior nuchal line, hence separating the anterior from the posterior triangle of the neck. Many types of structural variations in SCM have already been reported before. A unique variation of this muscle was discovered in an aged Caucasian male cadaver during an anatomical dissection at the Paracelsus Medical University in Nuremberg, Germany. This study reports a right unilateral accessory muscular branch at the sternal head of the SCM which formed a tendon on the level of omohyoid muscle before dividing into anterior and posterior fascicles. The posterior fascicle attached to the external carotid artery at the site where a common trunk for lingual and facial artery branched off, drawing external carotid artery inferiorly to build an inferior loop, whereas the anterior fascicle passed further superior and broadened to form a muscular belly. This superior muscular belly extended to the posterior and lateral side of the pharynx to ultimately merge into the superior constrictor pharyngeal muscle. Such anatomical variation has never been reported before. Therefore, we propose the nomenclature of this variational structure as a sternopharyngeal branch of the SCM. This report helps not only to inform the clinicians regarding the possible variation of this muscle during surgical procedures or radiological diagnostics but also encourage developmental researches in the future.

Cleidocervical muscle: a mini literature survey of a human muscle variation.

Cleidocervical muscles (CCM) or levator claviculae muscles in humans can be found as supernumerary unilaterally or bilaterally on the neck attached proximally to the clavicle and distally to the transverse process of cervical vertebrae at various levels. Altogether 20 case reports from year 1994 till present including 25 subjects related to CCM were found and analysed where parameters such as cervical insertion level, clavicular insertion at the middle vs. lateral third, unilateral vs. bilateral presence of the muscle, study type, reported gender of the subjects were extracted. Our literature survey shows that the prevalence of CCM in male and female was equally presented in radiological studies whereas almost 3-fold higher prevalence of males was found in cadaver reports. Since body donor system worldwide is male dominant, a 1:1 proportion of male and female in radiological studies could show more reality-based distribution of this muscle. Nevertheless, the presentation of this muscle was found in over 90% of the case reports unilaterally with higher left sided dominance. Even though the attachment points of CCM varied from case to case, the proximal attachment was found slightly more frequent on the middle third of the clavicle whereas the distal insertion was present more often on the superior cervical vertebrae than the lower ones. With prevalence of CCM in the population around 2.0-2.5%, the clinical, radiological and surgical relevance of this variation has to be highlighted to avoid potential misleading diagnostics in the neck.

Rare malformations associated with partial anomalous pulmonary venous return: a cadaveric case report.

A unique partial anomalous pulmonary venous return in combination with other rare malformations such as annular pancreas and a persistent umbilical vein was discovered in a female Caucasian cadaver during an anatomical dissection at the Paracelsus Medical University in Nuremberg, Germany. The pulmonary anomaly comprised the aberrant left superior pulmonary vein connecting the superior lobe of the left lung with the left brachiocephalic vein resulting in a left to right shunt. An annular pancreas without any signs causing duodenal compression was additionally found. To complete the constellation of malformations, a persistent umbilical vein within the round ligament fissure of the liver was also observed, connecting to an inferior branch of the extrahepatic left ramus of the portal vein. This rare constellation of malformations has been illustrated and thoroughly discussed with the currently available literature to develop a hypothesis for the genetic and developmental background.

Mechanical properties of native and acellular temporal muscle fascia for surgical reconstruction and computational modelling purposes.

The temporal muscle fascia (TMF) is a widely used graft material and of interest for computational simulations of the temporomandibular joint as well as computational and physical human head models in general. However, reliable biomechanical properties of the TMF are lacking to date. This study provides tensile data of 52 TMFs at an age range of 18 to 94 years. It further investigates, if acellular fascia scaffolds differ from native counterparts in their biomechanical behaviour. Native TMF has a median elastic modulus of 26.2 MPa (acellular: 24.5 MPa), an ultimate tensile strength of 2.9 MPa (acellular: 2.1 MPa), a maximum force of 12.6 N (acellular: 9.9 N) and a strain at failure of 14.1% (acellular: 14.8%). No significant difference was found regarding the properties of native and acellular samples. Elastic modulus and the ultimate tensile strength increased with age but only in the acellular group (p < 0.01). Decorin and fibronectin seemed to be washed out by the acellularization procedure. The absence of cells in acellular TMF samples is not of biomechanical relevance compared to the native state. Acellular TMF is a biomechanically promising scaffold material for graft purposes, which can be retrieved easily due to its superficial location.

Immune cells regulate VEGF signalling via release of VEGF and antagonistic soluble VEGF receptor-1.

Vascular endothelial growth factor (VEGF) is an important regulator of physiological and pathological angiogenesis. Besides malignant and stromal cells, local immune cells shape VEGF signalling in the tumour microenvironment. Aminobisphosphonates such as zoledronic acid (Zol) are drugs known to inhibit osteoclast activity and bone resorption, but also have immunomodulatory and anti-tumour effects. These properties have been linked previously to the down-regulation of VEGF and interference with tumour neo-angiogenesis. It was therefore surprising to find that treatment with Zol in combination with low-dose interleukin (IL)-2 increased serum VEGF levels in cancer patients. In this study we aimed to characterize the effect of Zol and IL-2 on VEGF signalling of blood-derived immune cells in vitro. Upon stimulation with IL-2, T cells and natural killer (NK) cells increase production of VEGF consecutively to the release of proinflammatory interferon (IFN)-γ, and Zol accelerates this response specifically in γδ T cells. VEGF can, in turn, be antagonized by soluble VEGF receptor (sVEGFR)-1, which is released depending on stimulatory conditions and the presence of monocytes. Additionally, malignant cells represented by leukaemia and lymphoma cell lines produce VEGF and some release sVEGFR-1 simultaneously. Our findings indicate a mechanism by which the VEGF and the sVEGFR-1 production by immune cells regulates local VEGF signalling. Therefore, immunotherapeutic interventions may enable both pro- as well as anti-tumour effects via immune cell-mediated alterations of VEGF homeostasis.

Bone morphogenetic protein 2/SMAD signalling in human ligamentocytes of degenerated and aged anterior cruciate ligaments.

OBJECTIVE: Anterior cruciate ligament (ACL) degeneration leads to knee instability and favors osteoarthritis (OA) progression. During ageing the growth factor sensitivity of ligaments changes but nothing is known about BMP2-signalling and -sensitivity in degenerated ACLs. This study addressed the question whether a dysregulated BMP2 signalling might contribute to age- and OA-dependent ACL degeneration. METHOD: ACL samples from patients with/without OA of different ages (<60 and ≥60 years, males, females) were graded histopathologically (n = 45). After stimulation of cultured ACL fibroblasts with 5 nM BMP2 for different time points, phosphorylation of SMAD1/5/8 and gene expression of crucial BMP2 signalling proteins, ligamentogenic and chondrogenic transcription factors, scleraxis (SCX) and SOX9, were analyzed. RESULTS: ACL samples displayed different grades of degeneration, often associated with synovitis and calcium deposits. Degeneration correlated significantly with synovitis. ACL fibroblasts expressed BMP type I receptors ALK3 and ALK6 and the BMP type II receptor BMPRII. Donors could be divided into "responders" and "non responders" since their BMP2 mediated SMAD1/5/8 phosphorylation level differed. Basal ID1 expression was lower in cells derived from OA compared with non-OA patients and BMP2 led to an ID1 induction in both. Irrespective of BMP2 stimulation, the donor age significantly influenced the expression profile of BMP6 and SCX but not BMP signalling. The BMP2-mediated SMAD6 expression differed between OA and healthy ACL fibroblasts. CONCLUSION: Our data indicate that the expression level of BMP2/SMAD target genes such as ID1 and SMAD6 was reduced in ACL fibroblasts derived from OA compared with non OA patients.

Diffusion chamber system for testing of collagen-based cell migration barriers for separation of ligament enthesis zones in tissue-engineered ACL constructs.

A temporary barrier separating scaffold zones seeded with different cell types prevents faster growing cells from overgrowing co-cultured cells within the same construct. This barrier should allow sufficient nutrient diffusion through the scaffold. The aim of this study was to test the effect of two variants of collagen-based barriers on macromolecule diffusion, viability, and the spreading efficiency of primary ligament cells on embroidered scaffolds. Two collagen barriers, a thread consisting of a twisted film tape and a sponge, were integrated into embroidered poly(lactic-co-caprolactone) and polypropylene scaffolds, which had the dimension of lapine anterior cruciate ligaments (ACL). A diffusion chamber system was designed and established to monitor nutrient diffusion using fluorescein isothiocyanate-labeled dextran of different molecular weights (20, 40, 150, 500 kDa). Vitality of primary lapine ACL cells was tested at days 7 and 14 after seeding using fluorescein diacetate and ethidium bromide staining. Cell spreading on the scaffold surface was measured using histomorphometry. Nuclei staining of the cross-sectioned scaffolds revealed the penetration of ligament cells through both barrier types. The diffusion chamber was suitable to characterize the diffusivity of dextran molecules through embroidered scaffolds with or without integrated collagen barriers. The diffusion coefficients were generally significantly lower in scaffolds with barriers compared to those without barriers. No significant differences between diffusion coefficients of both barrier types were detected. Both barriers were cyto-compatible and prevented most of the ACL cells from crossing the barrier, whereby the collagen thread was easier to handle and allowed a higher rate of cell spreading.

Immortalised human mesenchymal stem cells undergo chondrogenic differentiation in alginate and PGA/PLLA scaffolds.

Adult mesenchymal stem cells (MSCs) are a promising cell source in tissue engineering due to their availability, ease of isolation and high proliferative activity. This study was undertaken to investigate whether immortalised human MSC are able to undergo chondrogenic differentiation when cultured in alginate or in resorbable scaffolds. We directly compared chondrogenesis MSCs with that of human nasoseptal chondrocytes. Two previously established human stem cell lines L87/4 and V54-2 immortalised using the SV40 large T-antigen were either cultured in alginate or in polyglycolic acid/poly-L-lactic acid (PGA/PLLA) (90/10) copolymer scaffolds. TGF-ß1 was added for induction of chondrogenesis. Human nasoseptal chondrocytes and human fibroblasts were used as controls. Cultures were analysed for sulfated glycosaminoglycans (alcian blue staining) and for the presence of collagen type I, II and X (immunolabelling). SV40 large T-antigen immortalised human MSCs have the potential to undergo chondrogenic differentiation: After 21 days, cartilage-specific type II collagen was present in alginate and PGA/PLLA scaffolds, independent of the addition of TGF-ß1. Collagen type X was present in monolayer cultures as well as in alginate and PGA/PLLA scaffolds. Collagen type I was produced in marginal amounts only. Immortalised human MSCs are a suitable tool to study chondrogenesis in vitro and to screen biomaterials for cartilage tissue engineering applications.

In vitro characterization of self-assembled anterior cruciate ligament cell spheroids for ligament tissue engineering.

Tissue engineering of an anterior cruciate ligament (ACL) implant with functional enthesis requires site-directed seeding of different cell types on the same scaffold. Therefore, we studied the suitability of self-assembled three-dimensional spheroids generated by lapine ACL ligament fibroblasts for directed scaffold colonization. The spheroids were characterized in vitro during 14 days in static and 7 days in dynamic culture. Size maintenance of self-assembled spheroids, the vitality, the morphology and the expression pattern of the cells were monitored. Additionally, we analyzed the total sulfated glycosaminoglycan, collagen contents and the expression of the ligament components type I collagen, decorin and tenascin C on protein and for COL1A1, DCN and TNMD on gene level in the spheroids. Subsequently, the cell colonization of polylactide-co-caprolactone [P(LA-CL)] and polydioxanone (PDS) polymer scaffolds was assessed in response to a directed, spheroid-based seeding technique. ACL cells were able to self-assemble spheroids and survive over 14 days. The spheroids decreased in size but not in cellularity depending on the culture time and maintained or even increased their differentiation state. The area of P[LA-CL] scaffolds, colonized after 14 days by the cells of one spheroid, was in average 4.57 ± 2.3 mm(2). Scaffolds consisting of the polymer P[LA-CL] were more suitable for colonization by spheroids than PDS embroideries. We conclude that ACL cell spheroids are suitable as site-directed seeding strategy for scaffolds in ACL tissue engineering approaches and recommend the use of freshly assembled spheroids for scaffold colonization, due to their balanced proliferation and differentiation.

Embroidered polymer-collagen hybrid scaffold variants for ligament tissue engineering.

Embroidery techniques and patterns used for scaffold production allow the adaption of biomechanical scaffold properties. The integration of collagen into embroidered polylactide-co-caprolactone [P(LA-CL)] and polydioxanone (PDS) scaffolds could stimulate neo-tissue formation by anterior cruciate ligament (ACL) cells. Therefore, the aim of this study was to test embroidered P(LA-CL) and PDS scaffolds as hybrid scaffolds in combination with collagen hydrogel, sponge or foam for ligament tissue engineering. ACL cells were cultured on embroidered P(LA-CL) and PDS scaffolds without or with collagen supplementation. Cell adherence, vitality, morphology and ECM synthesis were analyzed. Irrespective of thread size, ACL cells seeded on P(LA-CL) scaffolds without collagen adhered and spread over the threads, whereas the cells formed clusters on PDS and larger areas remained cell-free. Using the collagen hydrogel, the scaffold colonization was limited by the gel instability. The collagen sponge layers integrated into the scaffolds were hardly penetrated by the cells. Collagen foams increased scaffold colonization in P(LA-CL) but did not facilitate direct cell-thread contacts in the PDS scaffolds. The results suggest embroidered P(LA-CL) scaffolds as a more promising basis for tissue engineering an ACL substitute than PDS due to superior cell attachment. Supplementation with a collagen foam presents a promising functionalization strategy.

Regulation of osteoarthritis-associated key mediators by TNFα and IL-10: effects of IL-10 overexpression in human synovial fibroblasts and a synovial cell line.

Synovial fibroblasts (SF) contribute to the pathogenesis of osteoarthritis (OA), but the effects of intra-articular cytokines on SF are not completely understood. The aim of this study was to characterize the interplay between tumor necrosis factor (TNF)α and the anti-inflammatory interleukin (IL)-10. Non-immortalized human SF and SF of the human cell line K4IM were stimulated with recombinant TNFα, IL-10, or TNFα + IL-10 (10 ng/ml each) for 24 h or transduced with an adenoviral vector overexpressing human IL-10 (hIL-10) and subsequently treated with 10 ng/ml TNFα for 24 h. Effects on the gene expression and protein synthesis of IL-6, IL-10, matrix metalloproteinases (MMP)-1, -3, type I collagen, ß1-integrin, and CD44 were investigated via real-time detection polymerase chain reaction, immunofluorescence labeling, flow cytometry, and Western blotting. IL-10 release by transduced SF was confirmed with enzyme-linked immunosorbent assay. Both cell populations were activated by TNFα and by TNFα + IL-10, increasing their gene expression and protein synthesis of IL-6, IL-10, MMP-1, and MMP-3 and altering the synthesis of type I collagen, ß1-integrin, and CD44. hIL-10 overexpression greatly elevated the gene expression and protein synthesis of IL-10. However, transduction did not significantly affect the gene expression of IL-6, MMP-1, and MMP-3 in SF. The increased expression of pro-inflammatory and catabolic mediators in TNFα-activated SF indicates their role in OA pathogenesis, suggesting they are a potential therapeutic target. Although the vigorousness of the responses of non-immortalized SF and K4IM clearly differ, the K4IM cell line seems to be a suitable model for non-immortalized human SF.

PGA-associated heterotopic chondrocyte cocultures: implications of nasoseptal and auricular chondrocytes in articular cartilage repair.

The availability of autologous articular chondrocytes remains a limiting issue in matrix assisted autologous chondrocyte transplantation. Non-articular heterotopic chondrocytes could be an alternative autologous cell source. The aims of this study were to establish heterotopic chondrocyte cocultures to analyze cell-cell compatibilities and to characterize the chondrogenic potential of nasoseptal chondrocytes compared to articular chondrocytes. Primary porcine and human nasoseptal and articular chondrocytes were investigated for extracellular cartilage matrix (ECM) expression in a monolayer culture. 3D polyglycolic acid- (PGA) associated porcine heterotopic mono- and cocultures were assessed for cell vitality, types II, I, and total collagen-, and proteoglycan content. The type II collagen, lubricin, and Sox9 gene expressions were significantly higher in articular compared with nasoseptal monolayer chondrocytes, while type IX collagen expression was lower in articular chondrocytes. Only ß1-integrin gene expression was significantly inferior in humans but not in porcine nasoseptal compared with articular chondrocytes, indicating species-dependent differences. Heterotopic chondrocytes in PGA cultures revealed high vitality with proteoglycan-rich hyaline-like ECM production. Similar amounts of type II collagen deposition and type II/I collagen ratios were found in heterotopic chondrocytes cultured on PGA compared to articular chondrocytes. Quantitative analyses revealed a time-dependent increase in total collagen and proteoglycan content, whereby the differences between heterotopic and articular chondrocyte cultures were not significant. Nasoseptal and auricular chondrocytes monocultured in PGA or cocultured with articular chondrocytes revealed a comparable high chondrogenic potential in a tissue engineering setting, which created the opportunity to test them in vivo for articular cartilage repair.

In vitro and in vivo neo-cartilage formation by heterotopic chondrocytes seeded on PGA scaffolds.

Implantation of tissue-engineered heterotopic cartilage into joint cartilage defects might be an alternative approach to improve articular cartilage repair. Hence, the aim of this study was to characterize and compare the quality of tissue-engineered cartilage produced with heterotopic (auricular, nasoseptal and articular) chondrocytes seeded on polyglycolic acid (PGA) scaffolds in vitro and in vivo using the nude mice xenograft model. PGA scaffolds were seeded with porcine articular, auricular and nasoseptal chondrocytes using a dynamic culturing procedure. Constructs were pre-cultured 3 weeks in vitro before being implanted subcutaneously in nude mice for 1, 6 or 12 weeks, non-seeded scaffolds were implanted as controls. Heterotopic neo-cartilage quality was assessed using vitality assays, macroscopical and histological scoring systems. Neo-cartilage formation could be observed in vitro in all PGA associated heterotopic chondrocytes cultures and extracellular cartilage matrix (ECM) deposition increased in vivo. The 6 weeks in vivo incubation time point leads to more consistent results for all cartilage species, since at 12 weeks in vivo construct size reductions were higher compared with 6 weeks except for auricular chondrocytes PGA cultures. Some regressive histological changes could be observed in all constructs seeded with all chondrocytes subspecies such as cell-free ECM areas. Particularly, but not exclusively in nasoseptal chondrocytes PGA cultures, ossificated ECM areas appeared. Elastic fibers could not be detected within any neo-cartilage. The neo-cartilage quality did not significantly differ between articular and non-articular chondrocytes constructs. Whether tissue-engineered heterotopic neo-cartilage undergoes sufficient transformation, when implanted into joint cartilage defects requires further investigation.

Healing parameters in a rabbit partial tendon defect following tenocyte/biomaterial implantation.

Although rabbits are commonly used as tendon repair model, interpretative tools are divergent and comprehensive scoring systems are lacking. Hence, the aim was to develop a multifaceted scoring system to characterize healing in a partial Achilles tendon defect model. A 3 mm diameter defect was created in the midsubstance of the medial M. gastrocnemius tendon, which remained untreated or was filled with a polyglycolic-acid (PGA) scaffold + fibrin and either left cell-free or seeded with Achilles tenocytes. After 6 and 12 weeks, tendon repair was assessed macroscopically and histologically using self-constructed scores. Macroscopical scoring revealed superior results in the tenocyte seeded PGA + fibrin group compared with the controls at both time points. Histology of all operated tendons after 6 weeks proved extracellular matrix (ECM) disorganization, hypercellularity and occurrence of irregular running elastic fibres with no significance between the groups. Some inflammation was associated with PGA implantation and increased sulphated proteoglycan deposition predominantly with the empty defects. After 12 weeks defect areas became hard to recognize and differences between groups, except for the increased sulphated proteoglycans content in the empty defects, were almost nullified. We describe a partial Achilles tendon defect model and versatile scoring tools applicable for characterizing biomaterial-supported tendon healing.

The role of pro-inflammatory and immunoregulatory cytokines in tendon healing and rupture: new insights.

Owing to limited self-healing capacity, tendon ruptures and healing remain major orthopedic challenges. Increasing evidence suggests that post-traumatic inflammatory responses, and hence, cytokines are involved in both cases, and also in tendon exercise and homeostasis. This review summarizes interrelations known between the cytokines interleukin (IL)-1ß, tumor necrosis factor (TNF)α, IL-6 and vascular endothelial growth factor (VEGF) in tendon to assess their role in tendon damage and healing. Exogenic cytokine sources are blood-derived leukocytes that immigrate in damaged tendon. Endogenous expression of IL-1ß, TNFα, IL-6, IL-10 and VEGF was demonstrated in tendon-derived cells. As tendon is a highly mechanosensitive tissue, cytokine homeostasis and cell survival underlie an intimate balance between adequate biomechanical stimuli and disturbance through load deprivation and overload. Multiple interrelations between cytokines and tendon extracellular matrix (ECM) synthesis, catabolic mediators e.g. matrix-degrading enzymes, inflammatory and angiogenic factors (COX-2, PGE2, VEGF, NO) and cytoskeleton assembly are evident. Pro-inflammatory cytokines affect ECM homeostasis, accelerate remodeling, amplify biomechanical adaptiveness and promote tenocyte apoptosis. This multifaceted interplay might both contribute to and interfere with healing. Much work must be undertaken to understand the particular interrelation of these inflammatory and regulatory mediators in ruptured tendon and healing, which has relevance for the development of novel immunoregulatory therapeutic strategies.

Differing in vitro biology of equine, ovine, porcine and human articular chondrocytes derived from the knee joint: an immunomorphological study.

For lack of sufficient human cartilage donors, chondrocytes isolated from various animal species are used for cartilage tissue engineering. The present study was undertaken to compare key features of cultured large animal and human articular chondrocytes of the knee joint. Primary chondrocytes were isolated from human, porcine, ovine and equine full thickness knee joint cartilage and investigated flow cytometrically for their proliferation rate. Synthesis of extracellular matrix proteins collagen type II, cartilage proteoglycans, collagen type I, fibronectin and cytoskeletal organization were studied in freshly isolated or passaged chondrocytes using immunohistochemistry and western blotting. Chondrocytes morphology, proliferation, extracellular matrix synthesis and cytoskeleton assembly differed substantially between these species. Proliferation was higher in animal derived compared with human chondrocytes. All chondrocytes expressed a cartilage-specific extracellular matrix. However, after monolayer expansion, cartilage proteoglycan expression was barely detectable in equine chondrocytes whereby fibronectin and collagen type I deposition increased compared with porcine and human chondrocytes. Animal-derived chondrocytes developed more F-actin fibers during culturing than human chondrocytes. With respect to proliferation and extracellular matrix synthesis, human chondrocytes shared more similarity with porcine than with ovine or equine chondrocytes. These interspecies differences in chondrocytes in vitro biology should be considered when using animal models.

IL-10 overexpression differentially affects cartilage matrix gene expression in response to TNF-alpha in human articular chondrocytes in vitro.

Cartilage-specific extracellular matrix synthesis is the prerequisite for chondrocyte survival and cartilage function, but is affected by the pro-inflammatory cytokine TNF-alpha in arthritis. The aim of the present study was to characterize whether the immunoregulatory cytokine IL-10 might modulate cartilage matrix and cytokine expression in response to TNF-alpha. Primary human articular chondrocytes were treated with either recombinant IL-10, TNF-alpha or a combination of both (at 10ng/mL each) or transduced with an adenoviral vector overexpressing human IL-10 and subsequently stimulated with 10ng/ml TNF-alpha for 6 or 24h. The effects of IL-10 on the cartilage-specific matrix proteins collagen type II, aggrecan, matrix-metalloproteinases (MMP)-3, -13 and pro-inflammatory cytokines were evaluated by real-time RT-PCR and immunohistochemistry. Transduced chondrocytes overexpressed high levels of IL-10 which significantly up-regulated collagen type II expression. TNF-alpha suppressed collagen type II and aggrecan, but increased MMP and cytokine expression in chondrocytes compared to the non-stimulated controls. The TNF-alpha mediated down-regulation of aggrecan expression was significantly antagonized by IL-10 overexpression, whereas the suppression of collagen type II was barely affected. The MMP-13 and IL-1beta expression by TNF-alpha was slightly reduced by IL-10. These results suggest that IL-10 overexpression modulates some catabolic features of TNF-alpha in chondrocytes.

Interleukin-10 modulates pro-apoptotic effects of TNF-alpha in human articular chondrocytes in vitro.

The aim of this study is to determine if there is an antagonistic effect between tumour necrosis factor (TNF)-alpha and the immunoregulatory interleukin (IL)-10 on chondrocytes survival. Serum-starved primary human articular chondrocytes were stimulated with either 10 ng/ml recombinant TNF-alpha, IL-10 or a combination of both (at 10 ng/ml each). Chondrocyte apoptosis was determined by measuring caspase-3/7, -8 and -9 activities using caspase assays. Mitochondrial apoptotic inducer bax, and the suppressor bcl-2 were evaluated using western blotting at 48 h. Results indicated that TNF-alpha increased caspase activities and resulted in a significant (p = 0.001) increase in bax/bcl-2 ratio. Stimulation with IL-10 did not alter caspase activities, while co-treatment with IL-10 and TNF-alpha inhibited TNF-alpha induced caspase activities and significantly (p > 0.004) impaired bax/bcl-2 ratio. At 24 h, mRNA levels for collagen type II, TNF-alpha and IL-10 were determined using real-time RT-PCR. Stimulation with TNF-alpha or TNF-alpha and IL-10 significantly inhibited collagen type II and increased IL-10 and TNF-alpha mRNA expression. IL-10 modulated the pro-apoptotic capacity of TNF-alpha in chondrocytes as shown by the decrease in caspase activities and bax/bcl-2 ratio compared to TNF-alpha stimulated chondrocytes, suggesting a mostly antagonistic interplay of IL-10 and TNF-alpha on mitochondrial apoptotic pathways.

Impact of the complement cascade on posttraumatic cartilage inflammation and degradation.

The limited ability of articular cartilage to recover from injury, remains an unsolved clinical challenge in orthopaedic surgery. Persistent injury of the articular surface can lead to the development of posttraumatic osteoarthritis. The local inflammatory response contributes to the pathogenesis of osteoarthritis by inducing chondrocyte apoptosis and the de-regulation of chondrocyte matrix remodelling. The role of the complement system in contributing to secondary inflammation-mediated cartilage degradation represents a newer field of investigation. The purpose of this review article is to summarize the known complement-mediated actions in cartilage homeostasis and injury. This article focuses on the known effects of complement on secondary chondrocyte apoptosis, and the interplay of the complement system with pro-inflammatory cytokines. Pharmacological therapies related to complement inhibition will be discussed as they potentially represent a new avenue for attenuating the effect of the complement system on cartilage repair.