Site-specific analysis of gene expression in early osteoarthritis using the Pond-Nuki model in dogs

An Injectable Containing Morphine, Ropivacaine, Epinephrine, and Ketorolac Is Not Cytotoxic to Articular Cartilage Explants From Degenerative Knees

PURPOSE

The purpose of this study was to determine the effects of a multidrug injectate containing morphine, ropivacaine, epinephrine, and ketorolac, commonly referred to as the "Orthococktail," on cartilage tissue viability and metabolic responses using an established in vitro model.

METHODS

With institutional review board approval and informed patient consent, tissues normally discarded after total knee arthroplasty (TKA) were recovered. Full-thickness cartilage explants (n = 72, Outerbridge grade 1 to 3) were created and bisected. Paired explant halves were treated with either 1 mL Orthococktail or 1 mL of saline and cultured for 8 hours at 37°C, with 0.5 mL of the treatment being removed and replaced with tissue culture media every hour. Explants were cultured for 6 days, and media were changed and collected on days 3 and 6. After day 6, tissues were processed for cell viability, weighed, and processed for histologic grading. Outcome measures were compared for significant differences between treated and untreated samples.

RESULTS

There were no significant differences in cartilage viability between control and Orthococktail-treated samples across a spectrum of cartilage pathologies. Orthococktail treatment consistently resulted in a significant decrease in the release of PGE2, MCP-1, MMP-7, and MMP-8 on day 3 of culture and PGE2, MMP-3, MMP-7, and MMP-8 on day 6 of culture, compared with saline controls.

CONCLUSION

The results of the present study indicate that an Orthococktail injection composed of morphine, ropivacaine, epinephrine, and ketorolac is associated with a transient decrease in degradative and inflammatory mediators produced by more severely affected articular cartilage and may mitigate perioperative joint pain such that postoperative narcotic drug use could be reduced.

CLINICAL RELEVANCE

The Orthococktail solution used in this study may be a safe intraoperative, intra-articular injection option for patients undergoing joint arthroplasty and other joint preservation surgical procedures.

Characterizing correlations among disease severity measures in osteochondral tissues from osteoarthritic knees

Osteoarthritis (OA) is a complex disease with biologic, biomechanical, and clinical heterogeneity among patients. Relationships among OA tissue metabolism, histopathology, and extracellular matrix (ECM) composition have not been well characterized. It was hypothesized that moderate (r = .4-.69) to strong (r > .7) correlations exist among these different measures of disease severity in osteochondral tissues from OA knees. Joint surfaces were obtained from patients (n = 6) undergoing total knee arthroplasty. Osteochondral explants (n = 136) were created and cultured for 3 days. Culture media were collected for biomarker analyses, and tissue was assessed for viability, histological scoring, and ECM composition. Correlations among media biomarker concentrations, histological scoring, ECM composition, and viability were determined using a Spearman correlation. GRO-α, IL-6, IL-8, and MCP-1 showed strong positive correlations to each other, and moderate positive correlations to NO, PGE2, and MMP-2. Total MMP activity, MMP-9, and MMP-13 had strong positive correlations to each other, and moderate positive correlations to MMP-1. MMP-2 had a moderate to strong positive correlations to histological scores (total and cartilage structure) and collagen content. MMP-2, IL-6, IL-8, and MCP-1 had moderate negative correlations, and MMP-9 had a moderate positive correlation, to viability. GRO-α, IL-6, IL-8, and MCP-1 had moderate positive correlations to collagen content. MMP-9, MMP-13, and total MMP activity had moderate negative correlations to tissue GAG. The data suggest links among proinflammatory and degradative pathways are present in OA osteochondral tissues. Further characterization of these links have the potential to delineate mechanisms of disease and diagnostic and therapeutic targets for knee OA.

The relationship between synovial inflammation, structural pathology, and pain in post-traumatic osteoarthritis: differential effect of stem cell and hyaluronan treatment

Background

Synovitis is implicated in the severity and progression of pain and structural pathology of osteoarthritis (OA). Increases in inflammatory or immune cell subpopulations including macrophages and lymphocytes have been reported in OA synovium, but how the particular subpopulations influence symptomatic or structural OA disease progression is unclear. Two therapies, hyaluronan (HA) and mesenchymal stem cells (MSCs), have demonstrated efficacy in some clinical settings: HA acting as device to improve joint function and provide pain relief, while MSCs may have immunomodulatory and disease-modifying effects. We used these agents to investigate whether changes in pain sensitization or structural damage were linked to modulation of the synovial inflammatory response in post-traumatic OA.

Methods

Skeletally mature C57BL6 male mice underwent medial-meniscal destabilisation (DMM) surgery followed by intra-articular injection of saline, a hyaluronan hexadecylamide derivative (Hymovis), bone marrow-derived stem cells (MSCs), or MSC + Hymovis. We quantified the progression of OA-related cartilage, subchondral bone and synovial histopathology, and associated pain sensitization (tactile allodynia). Synovial lymphocytes, monocyte/macrophages and their subpopulations were quantified by fluorescent-activated cell sorting (FACS), and the expression of key inflammatory mediators and catabolic enzyme genes quantified by real-time polymerase chain reaction (PCR).

Results

MSC but not Hymovis significantly reduced late-stage (12-week post-DMM) cartilage proteoglycan loss and structural damage. Allodynia was initially reduced by both treatments but significantly better at 8 and 12 weeks by Hymovis. Chondroprotection by MSCs was not associated with specific changes in synovial inflammatory cell populations but rather regulation of post-injury synovial Adamts4, Adamts5, Mmp3, and Mmp9 expression. Reduced acute post-injury allodynia with all treatments coincided with decreased synovial macrophage and T cell numbers, while longer-term effect on pain sensitization with Hymovis was associated with increased M2c macrophages.

Conclusions

This therapeutic study in mice demonstrated a poor correlation between cartilage, bone or synovium (histo)pathology, and pain sensitization. Changes in the specific synovial inflammatory cell subpopulations may be associated with chronic OA pain sensitization, and a novel target for symptomatic treatment.

An in vitro study of the effect of the optimal irrigation solution conditions during canine articular surgery

OBJECTIVES

To establish whether chondrocyte viability, matrix degradation and the induction of proteolytic gene expression in canine cartilage is independent of irrigation fluid osmolality and time following exposure to the irrigation fluid.

METHODS

Canine cartilage explants were exposed to one of three different solution types i) Culture medium (270-280 mOsmol/kg) ii) NaCl 0.9% (302 mOsmol/kg) iii) NaCl 0.9% with sucrose (600 mOsmol/kg). Chondrocyte viability and selected proteolytic gene expression were measured at two time points; immediately following exposure and 24 h following exposure. The media samples at 24 h following exposure were assessed for sulphated glycosaminoglycan (sGAG) release.

RESULTS

In all samples, no cell death was observed across the superficial or deeper layers of the cartilage. When adjusting for time, gene expression was not shown to be dependent on solution type. However for all solution types, Matrix Metalloproteinase 13 (MMP13) and A Disintegrin and Metalloproteinase with Thrombospondin Motifs 5 (ADAMTS5) expression was significantly decreased in cartilage samples at 24 h post exposure comparatively to samples tested immediately post exposure. No significant differences were identified in the relative sGAG release between the solution types.

CLINICAL SIGNIFCANCE

Arthroscopic solution irrigation of cartilage explants had no effect on cell viability or proteinase production. At present there is no indication to optimise irrigation fluid osmolarity, as conventional arthroscopic solution was not deleterious to healthy cartilage in this model.

Osteoarthritis in the Knee Joints of Göttingen Minipigs after Resection of the Anterior Cruciate Ligament? Missing Correlation of MRI, Gene and Protein Expression with Histological Scoring

Introduction

The Göttingen Minipig (GM) is used as large animal model in articular cartilage research. The aim of the study was to introduce osteoarthritis (OA) in the GM by resecting the anterior cruciate ligament (ACLR) according to Pond and Nuki, verified by histological and magnetic resonance imaging (MRI) scoring as well as analysis of gene and protein expression.

Materials and Methods

The eight included skeletally mature female GM were assessed after ACLR in the left and a sham operation in the right knee, which served as control. 26 weeks after surgery the knee joints were scanned using a 3-Tesla high-field MR tomography unit with a 3 T CP Large Flex Coil. Standard proton-density weighted fat saturated sequences in coronal and sagittal direction with a slice thickness of 3 mm were used. The MRI scans were assessed by two radiologists according to a modified WORMS-score, the X-rays of the knee joints by two evaluators. Osteochondral plugs with a diameter of 4mm were taken for histological examination from either the main loading zone or the macroscopic most degenerated parts of the tibia plateau or condyle respectively. The histological sections were blinded and scored by three experts according to Little et al. Gene expression analysis was performed from surrounding cartilage. Expression of adamts4, adamts5, acan, col1A1, col2, il-1ß, mmp1, mmp3, mmp13, vegf was determined by qRT-PCR. Immunohistochemical staining (IH) of Col I and II was performed. IH was scored using a 4 point grading (0—no staining; 3-intense staining).

Results and Discussion

Similar signs of OA were evident both in ACLR and sham operated knee joints with the histological scoring result of the ACLR joints with 6.48 ± 5.67 points and the sham joints with 6.86 ± 5.84 points (p = 0.7953) The MRI scoring yielded 0.34 ± 0.89 points for the ACLR and 0.03 ± 0.17 for the sham knee joints. There was no correlation between the histological and MRI scores (r = 0.10021). The gene expression profiles as well as the immunohistochemical findings showed no significant differences between ACLR and sham knee joints. In conclusion, both knee joints showed histological signs of OA after 26 weeks irrespective of whether the ACL was resected or not. As MRI results did not match the histological findings, MRI was obviously unsuitable to diagnose the OA in GM. The analysis of the expression patterns of the 10 genes could not shed light on the question, whether sham operation also induced cartilage erosion or if the degeneration was spontaneous. The modified Pond-Nuki model may be used with reservation in the adult minipig to induce an isolated osteoarthritis.

A Porcine Animal Model for Early Meniscal Degeneration - Analysis of Histology, Gene Expression and Magnetic Resonance Imaging Six Months after Resection of the Anterior Cruciate Ligament

BACKGROUND/OBJECTIVE

The menisci of the mammalian knee joint balance the incongruence between femoral condyle and tibial plateau and thus menisci absorb and distribute high loads. Degeneration processes of the menisci lead to pain syndromes in the knee joint. The origin of such degenerative processes on meniscal tissue is rarely understood and may be described best as an imbalance of anabolic and catabolic metabolism. A standardized animal model of meniscal degeneration is needed for further studies. The aim of the current study was to develop a porcine animal model with early meniscal degeneration.

MATERIAL AND METHODS

Resection of the anterior cruciate ligament (ACLR) was performed on the left knee joints of eight Göttingen minipigs. A sham operation was carried out on the right knee joint. The grade of degeneration was determined 26 weeks after the operation using histology and magnetic resonance imaging (MRI). Furthermore, the expression of 14 genes which code for extracellular matrix proteins, catabolic matrix metalloproteinases and inflammation mediators were analyzed.

RESULTS

Degenerative changes were detected by a histological analysis of the medial meniscus after ACLR. These changes were not detected by MRI. In terms of their gene expression profile, these degenerated medial menisci showed a significantly increased expression of COL1A1.

CONCLUSION

This paper describes a new animal model for early secondary meniscal degeneration in the Göttingen minipig. Histopathological evidence of the degenerative changes could be described. This early degenerative changes could not be seen by NMR imaging.

In vitro effects of triamcinolone acetonide and in combination with hyaluronan on canine normal and spontaneous osteoarthritis articular cartilage

The purposes of this study were to examine the cartilage degradation effects of triamcinolone acetonide (TA) on normal and osteoarthritic (OA) primary canine chondrocytes and cartilage explants and to examine the cartilage degradation effects of TA in combination with low-molecular-weight hyaluronan (LMWHA). To assess the effects of these drugs on cell culture, 3,[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and real-time PCR were used to measure chondrotoxicity and determine gene expression, respectively. Uronic acid and hydroxyproline remaining in cartilage and histopathology were used to estimate the effects of these drugs on cartilage explants. In chondrocyte cultures, TA reduced chondrocyte viability in a concentration-dependent manner. LMWHA 2.5 mg/ml combined with TA at IC20 (0.09 mg/ml) could increase the viability of normal chondrocytes when compared with TA-treated alone. TA at IC20 induced down-regulation of ACAN and induced up-regulation of ADAMTS5 in canine normal chondrocytes. TA at IC20 (0.11 mg/ml) up-regulated ADAMTS5, MMP2, MMP3, MMP13, and ACAN expression in canine OA chondrocytes. In explant culture, TA at 1.25, 2.5, and 5 mg/ml increased the severity of structural damage, chondrocyte loss and cluster formation, and proteoglycan loss in OA cartilage. LMWHA could decrease the chondrotoxicity of TA at IC20 only in normal chondrocytes, as observed by chondrocyte viability. The combination of LMWHA and TA did not show clearly beneficial effects in all other normal and OA samples. Consequently, using TA alone or in combination with LMWHA in OA cartilage should be of concern because it may lead to cartilage destruction.

Analysis of Gene Expression and Ultrastructure of Stifle Menisci from Juvenile and Adult Pigs

The origin of the age-associated degenerative processes in meniscal tissue is poorly understood and may be related to an imbalance of anabolic and catabolic metabolism. The aim of the current study was to compare medial menisci isolated from juvenile pigs and degenerated medial menisci from adult pigs in terms of gene expression profile and ultrastructure. Medial menisci were isolated from the knee joints of juvenile and adult pigs (n = 8 for each group). Degeneration was determined histologically according to a scoring system. In addition, the gene expression profiles of 14 genes encoding extracellular matrix proteins, catabolic matrix metalloproteinases and mediators of inflammation were analyzed. Changes in the ultrastructure of the collagen network of the meniscal tissue were analyzed by using transmission electron microscopy. The histologic analysis of menisci showed significantly higher grade of degeneration in tissue isolated from adult porcine knee joints compared with menisci isolated from juvenile knee joints. In particular, destruction of the collagen network was greater in adult menisci than in juvenile menisci. Degenerated menisci showed significantly decreased gene expression of COL1A1 and increased expression of MMP2, MMP13, and IL8. The menisci from adult porcine knee joints can serve as a model for meniscal degeneration. Degenerative changes were manifested as differences in histopathology, gene expression and ultrastructure of collagen network.

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

OBJECTIVE

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

SAMPLE

Femoral head cartilage from 16 dogs undergoing total hip replacement.

PROCEDURES

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

RESULTS

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

CONCLUSIONS AND CLINICAL RELEVANCE

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

Subchondral bone changes in three different canine models of osteoarthritis

OBJECTIVE

To test the hypothesis that changes in subchondral bone are significantly different among three canine models of osteoarthritis (OA).

DESIGN

In 21 purpose-bred mongrel dogs, OA was induced in one knee joint via either anterior cruciate ligament transection (ACLt; n = 5), medial femoral condylar groove creation (GR; n = 6), or medial meniscal release (MR; n = 5). Five dogs that had sham surgery (SH; n = 5) in one knee joint served as controls. Lameness scoring was performed every 4 weeks. Twelve weeks after surgery, the knee joints were examined by histology and histomorphometry.

RESULTS

Articular cartilage pathology as determined by Mankin scores was significantly severe in all three OA models compared to SH controls in the medial tibia (P < 0.001 to P = 0.026). ACLt had significantly thinner subchondral plate thickness (Sp.Th) in both the medial and lateral tibias while MR had significantly thicker Sp.Th in the medial tibia compared to SH controls (P < 0.001 to P = 0.011). Trabecular bone volume (BV/TV) and trabecular bone thickness (Tb.Th) for ACLt were significantly less than SH controls in the tibias (P < 0.001 to P = 0.011). Tibial Sp.Th, BV/TV, and Tb.Th were all moderately to strongly correlated with lameness scores obtained throughout the study period (r = -0.436 to r = -0.738, P < 0.001 to P = 0.047) while Mankin scores showed moderate to strong correlations with Sp.Th in each OA model (r = 0.465 to r = 0.816, P < 0.001 to P = 0.033).

CONCLUSIONS

Changes in Sp.Th are associated with articular cartilage damage while tibial Sp.Th and BV/TV and Tb.Th appear to be all influenced by joint loading alterations.

Diagnostic Modalities for Diseased Articular Cartilage-From Defect to Degeneration: A Review

The progression of cartilage matrix damage to generalized degeneration is associated with specific pathophysiological and clinical aspects. Reliable detection of stage-related characteristics of cartilage disease serves both a therapeutic and prognostic goal. Over the past years, several (pre)clinical diagnostic modalities for cartilage pathologies have been advocated. Each modality focuses on different aspects of the disease. Early diagnosis, before irreversible damage has occurred, opens up the possibility for better treatment and improves the patients' prognosis. This article gives an overview of the diagnostic modalities available for monitoring cartilage pathology and focuses on reliability, clinical value, current status, and possible applications.

Meniscal release in cruciate ligament intact stifles causes lameness and medial compartment cartilage pathology in dogs 12 weeks postoperatively

OBJECTIVE

To evaluate after 12 weeks the effects of caudal medial meniscal release (MR) in the cranial cruciate ligament-intact canine stifle.

STUDY DESIGN

Blinded, prospective in vivo study.

ANIMALS

Purpose-bred hound dogs (n=10).

METHODS

Either MR (n=5) or a sham (SH) surgery (n=5) was performed via arthroscopy. Orthopedic examination and subjective lameness evaluation were performed in each dog preoperatively and at 4, 8, and 12 weeks after surgery. Twelve weeks postoperatively, ultrasonographic, radiographic, and arthroscopic examinations were performed on the operated stifles. Gross pathology of the articular cartilage, cruciate ligaments, and menisci was assessed. India ink staining of the femoral and tibial articular surfaces was performed to determine the percent area of articular cartilage damage.

RESULTS

At 8 and 12 weeks after surgery, MR dogs were lamer than SH dogs. At 12 weeks, the degree of radiographic OA was significantly higher in MR stifles than in SH stifles. Gross and sonographic meniscal pathology was more severe in MR stifles compared with SH stifles. MR stifles had significantly more severe articular cartilage pathology compared with SH stifles 12 weeks after surgery; pathology was most severe in the medial compartment.

CONCLUSIONS

MR alone is associated with articular cartilage loss, further meniscal pathology, degenerative joint disease, and lameness.

CLINICAL RELEVANCE

Subsequent osteoarthritis and dysfunction of the stifle joint should be considered when making clinical decisions regarding MR in dogs.

The BMP antagonists follistatin and gremlin in normal and early osteoarthritic cartilage: an immunohistochemical study

OBJECTIVE

Bone morphogenic protein (BMP) activities are controlled in part by antagonists. In human osteoarthritic (OA) cartilage, the BMP antagonists follistatin and gremlin are increased but differentially regulated. Using the OA dog model, we determined if these BMP antagonists were produced at different stages during the disease process by comparing their in situ temporal and spatial distribution.

METHODS

Dogs were sacrificed at 4, 8, 10 and 12 weeks after surgery; normal dogs served as control. Cartilage was removed, differentiating fibrillated and non-fibrillated areas. Immunohistochemistry and morphometric analyses were performed for follistatin, gremlin, BMP-2/4 and IL-1beta. Growth factor-induced gremlin expression was assessed in dog chondrocytes.

RESULTS

Follistatin and gremlin production were very low in normal cartilage. Gremlin was significantly up-regulated in both non-fibrillated and fibrillated areas at 4 weeks, and only slightly increased with disease progression. Follistatin showed a time-dependent increased level in the non-fibrillated areas with significance reached at 8-12 weeks; in the fibrillated areas significant high levels were seen as early as 4 weeks. In the whole cartilage, follistatin and IL-1beta temporal production showed similar patterns; this was also true for gremlin and BMP-2/4, though BMP-2/4 production was already high in the normal dogs. Interestingly, data revealed that basic fibroblast growth factor (bFGF) could be another factor increasing gremlin expression early in the disease process. Comparison between superficial and deep zones revealed similar patterns for follistatin and IL-1beta in the superficial zone only; gremlin and BMP-2/4 had similar patterns in both zones.

CONCLUSION

Data show, for the first time, different spatial and temporal production of gremlin and follistatin in cartilage during OA progression. These findings may reflect different roles for each antagonist in this disease.

Prostaglandin E2 exerts catabolic effects in osteoarthritis cartilage: evidence for signaling via the EP4 receptor

Elevated levels of PGE(2) have been reported in synovial fluid and cartilage from patients with osteoarthritis (OA). However, the functions of PGE(2) in cartilage metabolism have not previously been studied in detail. To do so, we cultured cartilage explants, obtained from patients undergoing knee replacement surgery for advanced OA, with PGE(2) (0.1-10 muM). PGE(2) inhibited proteoglycan synthesis in a dose-dependent manner (maximum 25% inhibition (p < 0.01)). PGE(2) also induced collagen degradation, in a manner inhibitable by the matrix metalloproteinase (MMP) inhibitor ilomastat. PGE(2) inhibited spontaneous MMP-1, but augmented MMP-13 secretion by OA cartilage explant cultures. PCR analysis of OA chondrocytes treated with PGE(2) with or without IL-1 revealed that IL-1-induced MMP-13 expression was augmented by PGE(2) and significantly inhibited by the cycolooygenase 2 selective inhibitor celecoxib. Conversely, MMP-1 expression was inhibited by PGE(2), while celecoxib enhanced both spontaneous and IL-1-induced expression. IL-1 induction of aggrecanase 5 (ADAMTS-5), but not ADAMTS-4, was also enhanced by PGE(2) (10 muM) and reversed by celecoxib (2 muM). Quantitative PCR screening of nondiseased and end-stage human knee OA articular cartilage specimens revealed that the PGE(2) receptor EP4 was up-regulated in OA cartilage. Moreover, blocking the EP4 receptor (EP4 antagonist, AH23848) mimicked celecoxib by inhibiting MMP-13, ADAMST-5 expression, and proteoglycan degradation. These results suggest that PGE(2) inhibits proteoglycan synthesis and stimulates matrix degradation in OA chondrocytes via the EP4 receptor. Targeting EP4, rather than cyclooxygenase 2, could represent a future strategy for OA disease modification.

Gene expression profiling of normal and ruptured canine anterior cruciate ligaments

OBJECTIVE

To identify genes which may be involved in the development of anterior cruciate ligament (ACL) laxity and rupture in a naturally occurring canine osteoarthritis (OA) model.

DESIGN

Three groups of dog were studied: (1) dogs with ACL rupture; (2) dogs with intact ACLs from a breed predisposed to ACL rupture; (3) dogs with intact ACLs from a breed at very low risk of rupture. The transcriptomes of the ACLs from each group were compared using a whole genome microarray and quantitative reverse transcriptase polymerase chain reaction. Differential gene expression in ruptured canine ACLs was compared with that published in the literature for ruptured human ACLs.

RESULTS

No significant differences were identified between the gene expression profiles of normal ACLs of a breed predisposed to ACL rupture when compared to a breed relatively resistant to ACL rupture. A general pattern of increased protease and extracellular structural matrix gene expression was identified in the ruptured ACLs when compared to intact ACLs. The gene expression profiles of ruptured canine ACLs demonstrate similar patterns to those previously reported for ruptured human ACLs.

CONCLUSIONS

A transcriptomic basis to breed specific risk for the development of canine ACL rupture was not identified. Although changes in matrix associated gene expression in the ruptured ACL are similar between humans and dogs, the molecular events which may predispose to ACL laxity and rupture were not defined.

Cartilage gene expression correlates with radiographic severity of canine elbow osteoarthritis

The relationship between radiographic measures of severity of osteoarthritis (OA) and changes in gene expression in joints are not well characterised. In this study, the expression of 11 candidate genes was characterised by quantitative reverse transcriptase polymerase chain reaction in normal and OA cartilage and bone from the elbows of dogs with fragmented coronoid disease. The levels of expression of type I collagen alpha2 chain (COL1A2), type III collagen alpha1 chain (COL3A1), lumican (LUM), matrix metalloproteinase-2 (MMP2), -9 (MMP9) and -13 (MMP13) genes were increased and the expression of tissue inhibitor of metalloproteinase-2 (TIMP2) and cathepsin D (CTSD) genes were decreased in OA cartilage relative to normal cartilage. All differences correlated with radiographic measures of severity of OA. Levels of expression of COL1A2, MMP2, MMP9, MMP13 and TIMP1 were increased, whereas expression of TIMP2 was decreased in OA bone relative to normal bone. Cartilage gene expression may be correlated with the radiographic severity of OA.