The effects of doxycycline on nitric oxide and stromelysin production in dogs with cranial cruciate ligament rupture

Etiopathogenesis of Canine Cruciate Ligament Disease: A Scoping Review

The spontaneous rupture of the cranial cruciate ligament in dogs remains a pathoetiologic puzzle. Despite much progress in research over the past years, the systemic and local mechanisms leading to ligament degeneration and structural failure remain largely obscure. This scoping review focuses on pathogenesis and aims at summarizing and interpreting today's knowledge on causes of canine cruciate ligament rupture, i.e., the multifactorial mechanisms leading to degenerative stifle joint disease with collagen matrix degeneration and structural failures. Thus, the initial view of traumatic ligament rupture, fostered by "wear and tear", has clearly been replaced by a new concept of systemic processes linked to progressive degenerative joint disease and ligament failure; thus, the term "cranial cruciate ligament disease" has been coined and is generally accepted. In addition, cruciate ligament rupture in people shares some similarities with the lesion in dogs; therefore, the review also includes comparative studies. The methods used were based on the PRISMA-ScR model (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews).

A Systematic Review of Basic Science and Animal Studies on the Use of Doxycycline to Reduce the Risk of Posttraumatic Osteoarthritis After Anterior Cruciate Ligament Rupture/Transection

BACKGROUND

Posttraumatic osteoarthritis (PTOA) after injury to the anterior cruciate ligament (ACL) is common.

PURPOSE

To perform a systematic review of basic science and animal studies to determine the effect of doxycycline treatment on the prevention of PTOA after ACL rupture/transection.

STUDY DESIGN

Systematic review.

METHODS

A systematic review was performed by searching the PubMed, Cochrane Library, and Embase databases to identify basic science and animal studies evaluating the effect of doxycycline treatment on the prevention of PTOA of the knee joint after ACL/cranial cruciate ligament (CCL) injury. The search phrase used was "doxycycline cruciate ligament." Inclusion criteria were basic science and animal studies evaluating the effect of oral administration of doxycycline in ACL/CCL-deficient animals with or without a control group.

RESULTS

Seven studies met inclusion criteria and were included in this systematic review. Five studies were performed in dogs, 1 in rabbits, and 1 in mice. Overall, the effects of doxycycline treatment on the prevention of PTOA after ACL/CCL rupture/transection were mixed. In dogs, no significant effects of doxycycline treatment were found in terms of matrix metalloproteinase (MMP) activity, while a mouse study found significantly lower MMP-13 expression on the tibia in doxycycline-treated animals, suggesting that doxycycline may protect against proteoglycan loss and decrease osteoarthritis progression. Cartilage nitric oxide concentrations were lower in doxycycline-treated dogs compared with untreated dogs, suggesting decreased cartilage degradation among doxycycline-treated dogs, although there were no significant effects on cartilage stromelysin levels with no significant effects in terms of physiological remodeling or catabolism of cartilage. Bone formation or resorption was not found to be affected by doxycycline treatment. One study demonstrated a substantial beneficial effect of doxycycline on gross morphology of the medial femoral condyle. Doxycycline was found to conserve bone strain energy density and appeared to limit subchondral bone loss in 1 study.

CONCLUSION

Based on the limited available animal studies, doxycycline appears to demonstrate some benefits in the prevention of PTOA after ACL/CCL rupture/transection. Additional studies are needed to further characterize the potential benefits, side effects, dosage, and duration of this treatment after ACL injury in human patients.

Effect of doxycycline on contralateral canine cranial cruciate ligament rupture. A prospective randomized clinical trial in 69 dogs

OBJECTIVE

To evaluate whether doxycycline administered to dogs with unilateral cranial cruciate ligament rupture (Uni-CCLR) would decrease the risk of contralateral-CCLR (Co-CCLR). To evaluate predictors for Co-CCLR survival. To evaluate if a predisposition of Labrador Retrievers to Co-CCLR exists when compared to other breeds.

METHODS

In this prospective randomized controlled clinical trial, 69 client-owned dogs with Uni-CCLR were randomly assigned to a doxycycline (group-D: 7.5 mg/kg PO BID x 6 weeks) or non-doxycycline (group-ND: negative control). Medical and imaging data, time from Uni- to Co-CCLR and to follow-up were recorded. Statistics included chi-squared test, logistic regression, Kaplan-Meier survival analysis, log rank test, survival curves, and frailty model (p <0.05).

RESULTS

This study included 32 dogs in group-D, and 37 dogs in group-ND. Median follow-up was 54.5 and 61 months, respectively. Contralateral CCLR occurred in 53.1% and 48.6% at medians of 20 and 11 months, respectively. Doxycycline did not significantly decrease the risk of Co-CCLR (p = 0.83). This risk was decreased by 14.2% with each year of age but increased with each increasing kilogram of body weight and each increasing degree of tibial plateau angle by 5.4% and 9.7%, respectively. Labrador Retrievers were not significantly predisposed (p = 0.37).

CLINICAL SIGNIFICANCE

At the dose regimen investigated doxycycline does not decrease the risk for Co-CCLR.

A posteriori comparison of natural and surgical destabilization models of canine osteoarthritis

For many years Canis familiaris, the domestic dog, has drawn particular interest as a model of osteoarthritis (OA). Here, we optimized the dog model of experimental OA induced by cranial cruciate ligament sectioning. The usefulness of noninvasive complementary outcome measures, such as gait analysis for the limb function and magnetic resonance imaging for structural changes, was demonstrated in this model. Relationships were established between the functional impairment and the severity of structural changes including the measurement of cartilage thinning. In the dog model of naturally occurring OA, excellent test-retest reliability was denoted for the measurement of the limb function. A criterion to identify clinically meaningful responders to therapy was determined for privately owned dogs undergoing clinical trials. In addition, the recording of accelerometer-based duration of locomotor activity showed strong and complementary agreement with the biomechanical limb function. The translation potential of these models to the human OA condition is underlined. A preclinical testing protocol which combines the dog model of experimental OA induced by cranial cruciate ligament transection and the Dog model of naturally occurring OA offers the opportunity to further investigate the structural and functional benefits of disease-modifying strategies. Ultimately, a better prediction of outcomes for human clinical trials would be brought.

Matrix metalloproteinase activity in stifle synovial fluid of cranial cruciate ligament deficient dogs and effect of postoperative doxycycline treatment

This prospective clinical study investigated the activity of matrix metalloproteinases (MMPs) in stifle synovial fluid (SF) of 13 dogs with acute cranial cruciate ligament (CCL) rupture, and the effect of a postoperative doxycycline treatment. MMP-2, 3, 9 and 13 activities were compared with respect to the time of sampling (preoperatively or 1 month after surgical stabilisation) and the type of postoperative adjuvant treatment (doxycycline or not). No significant activity was detected for both MMP-3 and MMP-13. MMP-2 and MMP-9 activities were found to be significantly highly increased in SF of CCL ruptured stifles compared to control stifles of unaffected dogs. No significant effect from surgical stabilisation and postoperative doxycycline treatment on MMP-2 and MMP-9 activities was found, indicating that doxycycline may not be an appropriate postoperative medical treatment after CCL rupture.

Proinflammatory Cytokine Activities, Matrix Metalloproteinase-3 Activity, and Sulfated Glycosaminoglycan Content in Synovial Fluid of Dogs with Naturally Acquired Cranial Cruciate Ligament Rupture

OBJECTIVE

To measure and compare activities of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and matrix metalloproteinase-3 (MMP-3); as well as sulfated glycosaminoglycan (S-GAG) content in synovial fluid from dogs with cranial cruciate ligament rupture (CCLR) and dogs with clinically normal stifles. To determine whether correlations exist between demographic and disease-related variables and these synovial markers.

STUDY DESIGN

Prospective clinical study.

ANIMALS

Dogs with CCLR (n=23) and Beagles with normal stifle joints (n=21).

METHODS

Synovial fluid activities of proinflammatory cytokines (IL-1beta, IL-6, and TNF-alpha) were determined by bioassay. MMP-3 activity was measured using fluorogenic substrate. S-GAG contents were determined by dimethylmethylene blue dye-binding assay. Mann-Whitney U-test was used to compare results from CCLR joints with normal controls. Spearman's rank correlation test was used to evaluate associations between demographic and disease-related markers and synovial markers.

RESULTS

Mean values for synovial markers were significantly higher in CCLR joints compared with controls. IL-1beta and MMP-3 were positively correlated with lameness duration.

CONCLUSIONS

Activities of proinflammatory cytokines, MMP-3 activity and S-GAG contents were significantly elevated in synovial fluid from canine stifle joints with naturally acquired CCLR. These results indicate that there is joint inflammation and increased release of GAGs into synovial fluid, suggesting that these inflammatory changes are associated with depletion of proteoglycan from articular cartilage.

CLINICAL RELEVANCE

Medical and surgical treatments designed to decrease joint inflammation and breakdown of proteoglycans may be of value in the management of CCLR in the dog.

Oral treatment options for degenerative joint disease--presence and future

Alleviation of pain and inhibition of inflammation are the primary goals of pharmacotherapy of osteoarthritis (OA). These therapeutic goals can almost always be accomplished by the use of analgesics and nonsteroidal anti-inflammatory drugs (NSAID). One of the main problems of NSAIDs is their gastrointestinal toxicity, for which a prophylactic medication should be considered particularly amongst risk groups. Recent studies have shown that COX-2-selective and maybe also non-selective NSAIDs increase the cardiovascular risk so that their application is getting now drastically restricted. Pharmacological results published until now suggest that a clinically relevant minor analgesic and/or anti-inflammatory effect can be attained with the use of some of the SYmptomatic Slow Acting Drugs in OA (SYSADOAs). However, no clinical studies exist, which can positively confirm prevention, slowing down or reversal of any advanced joint cartilage destruction by any individual medication. Disease modifying therapy is still in its infancy; discovery and development of novel therapeutic targets and agents are an extremely difficult task, currently challenging many pharmaceutical companies and academic institutions.

Chondroprotective drugs in degenerative joint diseases

Catabolic cytokine and anabolic growth factor pathways control destruction and repair in osteoarthritis (OA). A unidirectional TNF-alpha/IL-1-driven cytokine cascade disturbs the homeostasis of the extracellular matrix of articular cartilage in OA. Although chondrocytes in OA cartilage overexpress anabolic insulin-like growth factor (IGF) and its specific receptor (IGFRI) autocrine TNF-alpha released by apoptotic articular cartilage cells sets off an auto/paracrine IL-1-driven cascade that overrules the growth factor activities that sustain repair in degenerative joint disease. Chondroprotection with reappearance of a joint space that had disappeared has been documented unmistakably in peripheral joints of patients suffering from spondyloarthropathy when treated with TNF-alpha-blocking agents that repressed the unidirectional TNF-alpha/IL-1-driven cytokine cascade. A series of connective tissue structure-modifying agents (CTSMAs) that directly affect IL-1 synthesis and release in vitro and down-modulate downstream IL-1 features, e.g. collagenase, proteoglycanase and matrix metalloproteinase activities, the expression of inducible nitric oxide synthase, the increased release of nitric oxide, and the secretion of prostaglandin E(2), IL-6 and IL-8, have been shown to possess disease-modifying OA drug (DMOAD) activities in experimental models of OA and in human subjects with finger joint and knee OA. Examples are corticosteroids, some sulphated polysaccharides, chemically modified tetracyclines, diacetylrhein/rhein, glucosamine and avocado/soybean unsaponifiables.

Pharmaceutical and nutraceutical management of canine osteoarthritis: present and future perspectives

Osteoarthritis (OA) is one of the most common chronic musculoskeletal diseases and causes of lameness in the dogs. The osteoarthritic disease process involves the entire synovial joint, encompassing the synovium, cartilage and underlying bone. Joint failure results from an abnormal mechanical strain causing damage to normal tissue or failure of pathologically impaired articular cartilage and bone under the influence of normal physiological strain or a combination of both. In both cases, the end point is cartilage loss and joint impairment. Osteoarthritic chondrocytes show an altered phenotype characterised by an excess production of catabolic factors, including metalloproteinases and reactive oxygen species. These factors constitute potential therapeutic targets and some new drugs and nutraceuticals have been proposed to promote the return to homeostasis. Until now, the therapeutic management of OA in dogs has been dominated by nonsteroidal anti-inflammatory drugs, but some new compounds, including diacerhein, with potential structure-modifying effects, are already used to treat OA in humans and could be helpful to manage OA in the dog. In addition, novel nutraceuticals, such as avocado/soybean unsaponifiable substances, have shown symptomatic effects in knee OA in humans, and could offer an alternative to prevent OA progression. This paper provides an overview of recent discoveries in the pathophysiology and in the therapeutic management of osteoarthritis in dogs.

Correlation of urinary nitric oxide concentrations with the development of hip dysplasia in Labrador retrievers

Urinary nitric oxide was determined in terms of the ratio of the concentrations of total urinary nitrite and nitrate:creatinine in 40 juvenile labrador retrievers, and radiographic signs of hip dysplasia and distraction indices were investigated in the same dogs in later life. The ratio was correlated significantly with the Norberg angle and with subchondral sclerosis in both hips, and with the grade of dysplasia in each hip and the dogs' overall grade of hip dysplasia. No correlations were observed between the ratio and the distraction indices or other radiographic criteria for hip dysplasia.

Managing chronic arthritis

Many compounds are being investigated for the control of symptoms of osteoarthritis in people and animals. Ideally, treatment should include analgesia, inflammation control, and chondroprotection. With further progress in this area, combination therapies tailored to the needs of the individual animal should enable us to maximize efficacy and minimize side effects. Only a few of the newer therapies and pharmaceutic agents have been investigated in the horse, however. With more rigorous investigation, they may be determined to be ineffective or unsafe. Meanwhile, as much information should be gathered from manufacturers as possible so as to ensure that appropriate recommendations are made.

Lessons from animal models of osteoarthritis

Characterization of transgenic murine osteoarthritis (OA) models and analysis of anterior cruciate ligament and meniscectomy models in various species, including rodents, has provided insight into pathogenic mechanisms and impact of loading. Development of a transgenic murine OA model by postnatal expression in hyaline cartilage of constitutively expressed human matrix metalloproteinase-13 emphasizes the potential role of this enzyme. On the other hand, collagenase involvement in OA models seems a confined focal process, complicating therapeutic approaches. The potential role of interleukin-1 still needs further confirmation. Apart from destructive cytokines, disturbed growth factor responses seems obvious. Transforming growth factor-beta is a crucial mediator in osteophyte formation, but its role in cartilage destruction has not yet been clarified. Nitric oxide appears involved in chondrocyte apoptosis and blocking of nitric oxide provides protection against joint pathology in OA models. Treatment with a range of disease-modifying drugs showed some efficacy in a number of OA models, but its predictive value for human OA remains obscure.