Contrasting effects of fluoroquinolone antibiotics on the expression of the collagenases, matrix metalloproteinases (MMP)-1 and -13, in human tendon-derived cells

Short-Term Exposure to Ciprofloxacin Reduces Proteoglycan Loss in Tendon Explants

Fluoroquinolone antibiotics are associated with increased risk of tendinopathy and tendon rupture, which can occur well after cessation of treatment. We have previously reported that the fluoroquinolone ciprofloxacin (CPX) reduced proteoglycan synthesis in equine tendon explants. This study aimed to determine the effects of CPX on proteoglycan catabolism and whether any observed effects are reversible. Equine superficial digital flexor tendon explant cultures were treated for 4 days with 1, 10, 100 or 300 µg/mL CPX followed by 8 days without CPX. The loss of [³⁵S]-labelled proteoglycans and chemical pool of aggrecan and versican was studied as well as the gene expression levels of matrix-degrading enzymes responsible for proteoglycan catabolism. CPX suppressed [³⁵S]-labelled proteoglycan and total aggrecan loss from the explants, although not in a dose-dependent manner, which coincided with downregulation of mRNA expression of MMP-9, -13, ADAMTS-4, -5. The suppressed loss of proteoglycans was reversed upon removal of the fluoroquinolone with concurrent recovery of MMP and ADAMTS mRNA expression, and downregulated TIMP-2 and upregulated TIMP-1 expression. No changes in MMP-3 expression by CPX was observed at any stage. These findings suggest that CPX suppresses proteoglycan catabolism in tendon, and this is partially attributable to downregulation of matrix-degrading enzymes.

Tendon and Ligament Genetics: How Do They Contribute to Disease and Injury? A Narrative Review

A significant proportion of patients requiring musculoskeletal management present with tendon and ligament pathology. Our understanding of the intrinsic and extrinsic mechanisms that lead to such disabilities is increasing. However, the complexity underpinning these interactive multifactorial elements is still not fully characterised. Evidence highlighting the genetic components, either reducing or increasing susceptibility to injury, is increasing. This review examines the present understanding of the role genetic variations contribute to tendon and ligament injury risk. It examines the different elements of tendon and ligament structure and considers our knowledge of genetic influence on form, function, ability to withstand load, and undertake repair or regeneration. The role of epigenetic factors in modifying gene expression in these structures is also explored. It considers the challenges to interpreting present knowledge, the requirements, and likely pathways for future research, and whether such information has reached the point of clinical utility.

Association between tendon ruptures and use of fluoroquinolone, and other oral antibiotics: a 10-year retrospective study of 1 million US senior Medicare beneficiaries

OBJECTIVES

To assess the association of fluoroquinolone use with tendon ruptures compared with no fluoroquinolone and that of the four most commonly prescribed non-fluoroquinolone antibiotics in the USA.

DESIGN

Retrospective observational study.

SETTING

US seniors enrolled in the federal old-age, survivor's insurance programme.

PARTICIPANTS

1 009 925 Medicare fee-for-service beneficiaries and their inpatient, outpatient, prescription drug records were used.

INTERVENTIONS

Seven oral antibiotics, fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) and amoxicillin, amoxicillin-clavulanate, azithromycin and cephalexin.

PRIMARY AND SECONDARY OUTCOME MEASURES

All tendon ruptures combined, and three types of tendon ruptures by anatomic site, Achilles tendon rupture, rupture of rotator cuff and other tendon ruptures occurred in 2007-2016.

RESULTS

Of three fluoroquinolones, only levofloxacin exhibited a significant increased risk of tendon ruptures-16% (HR=1.16; 95% CI 1.06 to 1.28), and 120% (HR=2.20; 95% CI 1.50 to 3.24) for rotator cuff and Achilles tendon rupture, respectively, in the ≤30 days window. Ciprofloxacin (HR=0.96; 95% CI 0.89 to 1.03) and moxifloxacin (HR=0.59; 95% CI 0.37 to 0.93) exhibited no increased risk of tendon ruptures combined.Among the non-fluoroquinolone antibiotics, cephalexin exhibited increased risk of combined tendon ruptures (HR=1.31; 95% CI 1.22 to 1.41) and modest to large risks across all anatomic rupture sites (HRs 1.19-1.93) at ≤30 days window. Notably, the risk of levofloxacin never exceeded the risk of the non-fluoroquinolone, cephalexin in any comparison.

CONCLUSIONS

In our study, fluoroquinolones as a class were not associated with the increased risk of tendon ruptures. Neither ciprofloxacin nor moxifloxacin exhibited any risk for tendon ruptures. Levofloxacin did exhibit significant increased risk. Cephalexin with no reported effect on metalloprotease activity had an equal or greater risk than levofloxacin; so we question whether metalloprotease activity has any relevance to observed associations with tendon rupture. Confounding by indication bias may be more relevant and should be given more consideration as explanation for significant associations in observational studies of tendon rupture.

Prospective of extracellular matrix and drug correlations in disease management

The extracellular matrix (ECM) comprises of many structural molecules that constitute the extracellular environment. ECM molecules are characterized by specific features like diversity, complexity and signaling, which are also results of improvement or development of disease mediated by some physiological changes. Several drugs have also been used to manage diseases and they have been reported to modulate ECM assembly, including physiological changes, beyond their primary targets and ECM metabolism. This review highlights the alteration of ECM environment for diseases and effect of different classes of drugs like nonsteroidal anti-inflammatory drugs, immune suppressant drug, steroids on ECM or its components. Thus, it is summarized from previously conducted researches that diseases can be managed by targeting specific components of ECM which are involved in the pathophysiology of diseases. Moreover, the drug delivery focused on targeting the ECM components also has the potential for the discovery of targeted and site specific release of drugs. Therefore, ECM or its components could be future targets for the development of new drugs for controlling various disease conditions including neurodegenerative diseases and cancers.

Uremic Toxins and Ciprofloxacin Affect Human Tenocytes In Vitro

Tendinopathy is a rare but serious complication of quinolone therapy. Risk factors associated with quinolone-induced tendon disorders include chronic kidney disease accompanied by the accumulation of uremic toxins. Hence, the present study explored the effects of the representative uremic toxins phenylacetic acid (PAA) and quinolinic acid (QA), both alone and in combination with ciprofloxacin (CPX), on human tenocytes in vitro. Tenocytes incubated with uremic toxins +/- CPX were investigated for metabolic activity, vitality, expression of the dominant extracellular tendon matrix (ECM) protein type I collagen, cell-matrix receptor β1-integrin, proinflammatory interleukin (IL)-1β, and the ECM-degrading enzyme matrix metalloproteinase (MMP)-1. CPX, when administered at high concentrations (100 mM), suppressed tenocyte metabolism after 8 h exposure and at therapeutic concentrations after 72 h exposure. PAA reduced tenocyte metabolism only after 72 h exposure to very high doses and when combined with CPX. QA, when administered alone, led to scarcely any cytotoxic effect. Combinations of CPX with PAA or QA did not cause greater cytotoxicity than incubation with CPX alone. Gene expression of the pro-inflammatory cytokine IL-1β was reduced by CPX but up-regulated by PAA and QA. Protein levels of type I collagen decreased in response to high CPX doses, whereas PAA and QA did not affect its synthesis significantly. MMP-1 mRNA levels were increased by CPX. This effect became more pronounced in the form of a synergism following exposure to a combination of CPX and PAA. CPX was more tenotoxic than the uremic toxins PAA and QA, which showed only distinct suppressive effects.

Determination of two fluoroquinolones and their combinations with hyaluronan effect in in vitro canine cartilage explants

Background

Previous studies reported the effect of enrofloxacin (Enro) and marbofloxacin (Mar) on cell death and alteration of the key genes involved in catabolic and anabolic processes and demonstrated the beneficial effects of hyaluronan (HA) combined with fluoroquinolones (FQs) on primary canine chondrocytes. This study further determines the effects of these treatments on canine cartilage explants in both normal and interleukin-1 beta (IL-1β)-stimulated conditions.

Methods

We examined sulfate glycosaminoglycan (s-GAG) release, uronic acid (UA) content, and safranin-O staining, as well as the expression patterns of inflammatory, extracellular matrix (ECM) component and enzymes.

Results

Enro treatment alone effectively stimulated proteoglycan anabolism by increasing UA content and glycosaminoglycans (GAGs) in normal and pre-IL-1β-stimulated explant, whereas Mar showed opposite results. The combination of HA and FQs increased s-GAG release and UA content in normal explants in addition to effective down-regulated expression of MMP3. HA reduced the adverse effects of Mar by enhancing UA and GAG contents in both normal and pre-IL-1β-explants. Moreover, HA effectively induced HAS1and ACANup-regulation and reduced MMP9, TNF, PTGS2,and NFKB1 expression for a long term.

Discussion

Our results suggest the direct effects of Enro and Mar may selectively stimulate the conditioned explants to express MMP-codinggenes and promote gene expression involved in matrix production, pro-inflammatory cytokines, and cell degradation in different directions. HA successfully reduced the adverse effects of FQs by enhancing s-GAG and UA contents and down-regulated expression of MMPs.

Association between oral fluoroquinolone use and lateral canthal tendon rupture: case report

It is well established and documented that fluoroquinolone use is associated with the development of tendinopathy. However, little is known about the possible effects of this class of antibiotics on the orbit. We present a case of lateral canthal tendon rupture that presented with an acute right lower eyelid ectropion in a young, renal compromised patient in the setting of recent fluoroquinolone use for pneumonia. Eye care clinicians need to be aware of the possible effects of fluoroquinolones on the eyelids.

Fluoroquinolones and the Risk of Achilles Tendon Disorders: Update on a Neglected Complication

OBJECTIVE

To evaluate the current evidence and to identify associated risk factors that increase the incidence of this complication. Fluoroquinolone (FQ) has been considered the first-line therapy for uncomplicated urinary infections. FQ has been associated with Achilles tendon disorders, especially during the first month of treatment.

METHODS

Data sources searched included PubMed, MEDLINE, and Scopus from January 1988 to June 2017.

RESULTS

A total of 79 articles were used, with ciprofloxacin representing the most common drug.

CONCLUSION

We found that male gender, advanced age, normal body mass index, chronic renal failure, and concurrent use of corticosteroids increase the risk of Achilles tendon disorders.

Two Unique Cases of Ciprofloxacin-Associated Avulsion of Ligament and Tendon

Ciprofloxacin is recognized to have a deleterious relationship with tendons, particularly Achilles tendinopathy, which makes up most case reports. Tendinopathy seems to occur because of induction of collagen-degrading enzymes causing damage and ischemia of the poorly vascularized regions preventing repair. The focus on the relationship of ciprofloxacin and the Achilles tendon leaves patients on fluoroquinolones with non-Achilles tendinopathy symptoms at risk of misdiagnosis. There have not been any documented instances of ligament damage with ciprofloxacin administration in the literature, although ligament and tendon compositions are similar and should have similar susceptibility. This report includes two cases, one presenting with right lateral thumb pain and a medical history of gastroenteritis treated with ciprofloxacin. Physical examination showed swelling of the right metacarpophalangeal joint and ultrasound confirmed disruption of the radial collateral ligament at insertion on first metacarpal; the second case is of a woman presenting with right hip pain in setting of chronic recurrent diverticulitis treated with ciprofloxacin. She received work-up for lumbar disc disease and spondylosis. After standard therapy with pharmacotherapy and physical therapy for radiculopathy failed, magnetic resonance imaging was performed showing near complete avulsion of the right hamstring tendons from the ischial tuberosity.

Nonantibiotic Effects of Fluoroquinolones in Mammalian Cells

Fluoroquinolones (FQ) are powerful broad-spectrum antibiotics whose side effects include renal damage and, strangely, tendinopathies. The pathological mechanisms underlying these toxicities are poorly understood. Here, we show that the FQ drugs norfloxacin, ciprofloxacin, and enrofloxacin are powerful iron chelators comparable with deferoxamine, a clinically useful iron-chelating agent. We show that iron chelation by FQ leads to epigenetic effects through inhibition of α-ketoglutarate-dependent dioxygenases that require iron as a co-factor. Three dioxygenases were examined in HEK293 cells treated with FQ. At sub-millimolar concentrations, these antibiotics inhibited jumonji domain histone demethylases, TET DNA demethylases, and collagen prolyl 4-hydroxylases, leading to accumulation of methylated histones and DNA and inhibition of proline hydroxylation in collagen, respectively. These effects may explain FQ-induced nephrotoxicity and tendinopathy. By the same reasoning, dioxygenase inhibition by FQ was predicted to stabilize transcription factor HIF-1α by inhibition of the oxygen-dependent hypoxia-inducible transcription factor prolyl hydroxylation. In dramatic contrast to this prediction, HIF-1α protein was eliminated by FQ treatment. We explored possible mechanisms for this unexpected effect and show that FQ inhibit HIF-1α mRNA translation. Thus, FQ antibiotics induce global epigenetic changes, inhibit collagen maturation, and block HIF-1α accumulation. We suggest that these mechanisms explain the classic renal toxicities and peculiar tendinopathies associated with FQ antibiotics.

Fluoroquinolones impair tendon healing in a rat rotator cuff repair model: a preliminary study

BACKGROUND

Recent studies suggest that fluoroquinolone antibiotics predispose tendons to tendinopathy and/or rupture. However, no investigations on the reparative capacity of tendons exposed to fluoroquinolones have been conducted.

HYPOTHESIS

Fluoroquinolone-treated animals will have inferior biochemical, histological, and biomechanical properties at the healing tendon-bone enthesis compared with controls.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ninety-two rats underwent rotator cuff repair and were randomly assigned to 1 of 4 groups: (1) preoperative (Preop), whereby animals received fleroxacin for 1 week preoperatively; (2) pre- and postoperative (Pre/Postop), whereby animals received fleroxacin for 1 week preoperatively and for 2 weeks postoperatively; (3) postoperative (Postop), whereby animals received fleroxacin for 2 weeks postoperatively; and (4) control, whereby animals received vehicle for 1 week preoperatively and for 2 weeks postoperatively. Rats were euthanized at 2 weeks postoperatively for biochemical, histological, and biomechanical analysis. All data were expressed as mean ± standard error of the mean (SEM). Statistical comparisons were performed using either 1-way or 2-way ANOVA, with P < .05 considered significant.

RESULTS

Reverse transcriptase quantitative polymerase chain reaction (RTqPCR) analysis revealed a 30-fold increase in expression of matrix metalloproteinase (MMP)-3, a 7-fold increase in MMP-13, and a 4-fold increase in tissue inhibitor of metalloproteinases (TIMP)-1 in the Pre/Postop group compared with the other groups. The appearance of the healing enthesis in all treated animals was qualitatively different than that in controls. The tendons were friable and atrophic. All 3 treated groups showed significantly less fibrocartilage and poorly organized collagen at the healing enthesis compared with control animals. There was a significant difference in the mode of failure, with treated animals demonstrating an intrasubstance failure of the supraspinatus tendon during testing. In contrast, only 1 of 10 control samples failed within the tendon substance. The healing enthesis of the Pre/Postop group displayed significantly reduced ultimate load to failure compared with the Preop, Postop, and control groups. There was no significant difference in load to failure in the Preop group compared with the Postop group. Pre/Postop animals demonstrated significantly reduced cross-sectional area compared with the Postop and control groups. There was also a significant reduction in area between the Preop and control groups.

CONCLUSION

In this preliminary study, fluoroquinolone treatment negatively influenced tendon healing.

CLINICAL RELEVANCE

These findings indicate that there was an active but inadequate repair response that has potential clinical implications for patients who are exposed to fluoroquinolones before tendon repair surgery.

Toxic effects of levofloxacin on rat annulus fibrosus cells: an in-vitro study

BACKGROUND

Fluoroquinolones are in wide clinical use as safe and effective antibiotics. Articular cartilage, tendons, and epiphyseal growth plates have been recognized as targets of fluoroquinolone-induced connective tissue toxicity. However, the effects of fluoroquinolones on annulus fibrosus (AF) cells are still unknown.

MATERIAL/METHODS

The main objective of this study was to investigate the effects of levofloxacin, a typical fluoroquinolone antibiotic drug, on rat AF cells in vitro. Rat annulus fibrosus (RAF) cells were treated with levofloxacin at different concentrations (0, 10, 20, 30, 40, 60, 80, and 90 μg/ml) and were assessed to determine the possible cytotoxic effects of levofloxacin. Inverted phase-contrast microscopy was used to accomplish the morphological observation of apoptosis of treated cells. Western blot and real-time quantitative RT-PCR (qPCR) was used to explore the expression of active caspase-3 and MMP-3. Flow cytometry was used to measure the apoptotic incidences.

RESULTS

Our study showed that levofloxacin, with concentrations at 30, 60, and 90 μg/ml, induced dose-dependent RAF cell apoptosis and higher expression of caspase-3 and MMP-3. More apoptotic cells were observed by inverted phase-contrast microscopy. Moreover, levofloxacin increased the activity of caspase-3, and it also reduced cell viability with different concentrations ranging from 10 to 80 μg/ml.

CONCLUSIONS

Our study results suggest that levofloxacin has cytotoxic effects on RAF cells, characterized by enhancing apoptosis and reducing cell viability, and indicate a potential toxic effect of fluoroquinolones on RAF cells.

Pathology of the tendo Achillis: do our genes contribute?

The incidence of acute and chronic conditions of the tendo Achillis appear to be increasing. Causation is multifactorial but the role of inherited genetic elements and the influence of environmental factors altering gene expression are increasingly being recognised. Certain individuals' tendons carry specific variations of genetic sequence that may make them more susceptible to injury. Alterations in the structure or relative amounts of the components of tendon and fine control of activity within the extracellular matrix affect the response of the tendon to loading with failure in certain cases. This review summarises present knowledge of the influence of genetic patterns on the pathology of the tendo Achillis, with a focus on the possible biological mechanisms by which genetic factors are involved in the aetiology of tendon pathology. Finally, we assess potential future developments with both the opportunities and risks that they may carry.

Ciprofloxacin has antifibrotic effects in scleroderma fibroblasts via downregulation of Dnmt1 and upregulation of Fli1

Systemic sclerosis (SSc) is characterized by fibrosis of the skin and internal organs. The present study was undertaken to examine the effects of ciprofloxacin, a fluoroquinolone antibiotic implicated in matrix remodeling, on dermal and lung fibroblasts obtained from SSc patients. Dermal and lung fibroblasts from SSc patients and healthy subjects were treated with ciprofloxacin. Western blotting was used to analyze protein levels and RT-PCR was used to measure mRNA expression. The pharmacologic inhibitor UO126 was used to block Erk1/2 signaling. SSc dermal fibroblasts demonstrated a significant decrease in collagen type I mRNA and protein levels after antibiotic treatment, while healthy dermal fibroblasts were less sensitive to ciprofloxacin, downregulating collagen only at the protein levels. Connective tissue growth factor (CCN2) gene expression was significantly reduced and matrix metalloproteinase 1 (MMP1) levels were enhanced after ciprofloxacin treatment to a similar extent in healthy and SSc fibroblasts. Ciprofloxacin induced Erk1/2 phosphorylation, and Erk1/2 blockade completely prevented MMP1 upregulation. However, Smad1 and Smad3 activation in response to TGFβ was not affected. The expression of friend leukemia integration factor 1 (Fli1), a transcriptional repressor of collagen, was increased after treatment with ciprofloxacin only in SSc fibroblasts, and this was accompanied by a decrease in the levels of DNA methyltransferase 1 (Dnmt1). Similar effects were observed in SSc-interstitial lung disease (ILD) lung fibroblasts. In summary, our study demonstrates that ciprofloxacin has antifibrotic actions in SSc dermal and lung fibroblasts via the downregulation of Dnmt1, the upregulation of Fli1 and induction of MMP1 gene expression via an Erk1/2-dependent mechanism. Thus, our data suggest that ciprofloxacin may be an attractive therapy for SSc skin and lung fibrosis.

Platelet-rich plasma protects tenocytes from adverse side effects of dexamethasone and ciprofloxacin

BACKGROUND

Ruptured tendons heal very slowly and complete recovery from injury is uncertain. Platelet-rich plasma (PRP), a rich source of growth factors, is currently being widely tested as a soft tissue healing agent and may accelerate tendon repair. The authors assessed the ability of PRP to prevent in vitro adverse effects of 2 drugs commonly linked to tendon rupture and tendinopathy, glucocorticoids and fluoroquinolone antibiotics.

HYPOTHESIS

The pro-healing response induced by PRP protects human tenocytes against the cytotoxic effects of dexamethasone and ciprofloxacin.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human primary hamstring tenocytes were exposed to different doses of ciprofloxacin and dexamethasone with and without PRP. AlamarBlue, β-galactosidase assay, and live/dead stain were used to measure, respectively, viability, senescence, and death in tenocyte culture.

RESULTS

The viability of cells exposed to high doses of ciprofloxacin was significantly decreased compared with controls, with no induced senescence but increased cell death. Dexamethasone reduced viable cell number without inducing overt cell death, but the number of senescent cells increased considerably. After co-treatment with 10% PRP, viable cell number increased significantly in both conditions and the number of dead cells decreased in ciprofloxacin-treated cultures. Moreover, dexamethasone-induced senescence was markedly reduced by co-treatment with 10% PRP.

CONCLUSION

This study demonstrates that ciprofloxacin and dexamethasone have differing adverse effects on human tenocytes, with ciprofloxacin inducing cell death while dexamethasone primarily induces senescence. The authors showed that PRP can protect cultured human tenocytes against cell death or senescence induced by these drugs.

CLINICAL RELEVANCE

Both ciprofloxacin and dexamethasone are highly effective in treatment of inflammatory and infectious conditions, therefore new strategies to minimize their adverse effects are of strong interest. These findings suggest the potential for local administration of PRP to enhance tendon healing in patients undergoing glucocorticoid or fluoroquinolone treatment.

Effect of fluoroquinolones on the expression of matrix metalloproteinase in debrided cornea of rats

Matrix metalloproteinases (MMPs) are implicated in regenerative and healing processes in corneal injuries. Based upon reports that topical fluoroquinolones (FQs) may cause perforations during corneal healing by modulating MMPs, this study evaluated the comparative effects of commercially available FQs eye drops on the expression of MMP-2 and MMP-9 in the cornea after ethanol injury. Uniform corneal epithelial defects were created using 70% ethanol in the right eye of the rats (n = 6). The groups studied were (I) sham, (II) normal saline with benzalkonium chloride (NS-BKC), (III) norfloxacin 0.3%, (IV) ciprofloxacin 0.3%, (V) lomefloxacin 0.3%, (VI) sparfloxacin 0.3%, (VII) gatifloxacin 0.3%, and (VIII) moxifloxacin 0.5%. Each treatment was instilled six times/day up to 48 h and rats were sacrificed using excess of anesthesia. The corneas were excised to study the expression of MMP-2 and MMP-9 using gelatin zymography and real-time PCR. All the FQs significantly increased the expression of MMP-2 and MMP-9 as compared to the sham and NS-BKC-treated group. NS-BKC did not show a significant effect on MMPs expression compared to the sham group. Among the studied FQs, ciprofloxacin was observed to exhibit maximal induction of MMP-2 and MMP-9, whereas lomefloxacin exhibited an equivocal effect on both MMP-2 and MMP-9 expression. Findings of the present study demonstrate that topical application of FQs may induce the expression of MMP-2 and MMP-9 in debrided corneal epithelium and, therefore, may delay corneal wound healing. Thus, it can be concluded that selecting a FQ for ophthalmic use having minimal effect on MMPs may impact wound healing in injured or vulnerable cornea.

Comparative study of the properties of tendinocytes derived from three different sites in the equine superficial digital flexor tendon

This aim of this study was to determine the characteristic differences in tendinocytes derived from three sites of the equine superficial digital flexor tendon (SDFT)-proximally the myotendinous junction (MTJ), mid-metacarpal (mM) and osteotendinous junction (OTJ)-in morphology, proliferation, and ability for synthesis of collagen and matrix metalloproteinases (MMPs). Little difference was observed in cell proliferation. Addition of tumor necrosis factor (TNF) alpha to the culture medium resulted in increased collagen synthesis by tendinocytes from all three sites. The amount of collagen synthesized by tendinocytes derived from the mM and OTJ was much larger than that synthesized by untreated tendinocytes. A collagen zymogram revealed that proMMP-13 synthesis was increased towards the distal site. However, TNFalpha treatment resulted in a significant decrease in the amount of proMMP-13 synthesized by tendinocytes from all three sites. On the other hand, a gelatin zymogram showed that the synthesis level of proMMP-9 tended to decrease towards the distal site, but there was little difference between synthesis levels of proMMP-9 before and after TNFalpha treatment. These results indicated that tendinocytes in the same tendon have different characteristics and that these characterisities would reflect the function of tendinocytes in vivo. Also, the isolated tendinocytes provided much information on the characteristics and properties of tendons for the ECM turnover system and on the responsiveness of tendinocytes to complex inflammatory responses in a tendinopathy condition.

Extracellular matrix molecules: potential targets in pharmacotherapy

The extracellular matrix (ECM) consists of numerous macromolecules classified traditionally into collagens, elastin, and microfibrillar proteins, proteoglycans including hyaluronan, and noncollagenous glycoproteins. In addition to being necessary structural components, ECM molecules exhibit important functional roles in the control of key cellular events such as adhesion, migration, proliferation, differentiation, and survival. Any structural inherited or acquired defect and/or metabolic disturbance in the ECM may cause cellular and tissue alterations that can lead to the development or progression of disease. Consequently, ECM molecules are important targets for pharmacotherapy. Specific agents that prevent the excess accumulation of ECM molecules in the vascular system, liver, kidney, skin, and lung; alternatively, agents that inhibit the degradation of the ECM in degenerative diseases such as osteoarthritis would be clinically beneficial. Unfortunately, until recently, the ECM in drug discovery has been largely ignored. However, several of today's drugs that act on various primary targets affect the ECM as a byproduct of the drugs' actions, and this activity may in part be beneficial to the drugs' disease-modifying properties. In the future, agents and compounds targeting directly the ECM will significantly advance the treatment of various human diseases, even those for which efficient therapies are not yet available.

Molecular and histologic evaluation of idiopathic hyperextension of the metacarpophalangeal and metatarsophalangeal joints in adult llamas

OBJECTIVE

To determine the molecular and histologic characteristics of hyperextension of the metacarpophalangeal and metatarsophalangeal joints in adult llamas.

ANIMALS

12 adult llamas (6 with bilateral hyperextension of the metacarpophalangeal or metatarsophalangeal joints [affected] and 6 age- and sex-matched clinically normal control llamas).

PROCEDURES

Llamas were euthanized, and specimens of superficial digital flexor tendon, deep digital flexor tendon, and suspensory ligament were obtained from 4 areas and snap frozen in liquid nitrogen or suspended in neutral-buffered 10% formalin. Histologic evaluation of collagen fiber orientation, elastin content, and proteoglycan content was performed by use of Masson trichrome, picrosirius red, Verhoeff, and Alcian blue stains. Total RNA was isolated from frozen suspensory ligament specimens. Gene expression of collagen types I and III, lysyl oxidase, and matrix metalloproteinase-13 was evaluated with a real-time quantitative reverse transcriptase PCR assay.

RESULTS

Gene expression of collagen types I and III, lysyl oxidase, and matrix metalloproteinase-13 in suspensory ligaments was similar between affected and control llamas. Collagen orientation and elastin content of the flexor tendons and suspensory ligaments were also similar between the groups. Proteoglycan content was low in most specimens but was focally increased in discrete lesions of suspensory ligaments in 2 affected and 2 control llamas.

CONCLUSIONS AND CLINICAL RELEVANCE

Hyperextension of the metacarpophalangeal or metatarsophalangeal joints in llamas did not appear to be caused by degeneration or inflammation of the suspensory ligament. Although focal proteoglycan accumulation existed in the suspensory ligaments of 2 affected llamas, widespread abnormal connective tissue proteoglycan accumulation was not found.

Drug-induced arthritic and connective tissue disorders

OBJECTIVES

All pharmacologic agents have the potential for both benefit and toxicity. Among the more interesting and important adverse consequences of drug therapy are a range of joint and connective tissue complaints that may mimic or reproduce primary rheumatologic diseases. In this article, we review the literature on commonly used drugs reported to induce arthritis and/or connective tissue-based diseases. We assess the strength of the reported associations, discuss diagnostic features and treatment implications, and consider possible mechanisms for drug-induced genesis of rheumatic conditions.

METHODS

We reviewed the Medline database from 1987 to 2006 to identify drug-induced arthritic and connective-tissue disease syndromes, utilizing 48 search terms. A qualitative review was performed after the articles were abstracted and the relevant information was organized.

RESULTS

Three hundred fifty-seven articles of possible relevance were identified. Two hundred eleven publications were included in the final analysis (case series and reports, clinical trials, and reviews). Many drugs were identified as mimicking existing rheumatic conditions, including both well-established small molecules (eg, sulfasalazine) and recently introduced biologic agents (eg, antitumor necrosis factor agents). The most commonly reported drug-induced rheumatic conditions were lupus-like syndromes. Arthritis and vasculitis were also often reported.

CONCLUSIONS

Drug-induced rheumatic syndromes are manifold and offer the clinician an opportunity to define an illness that may remit with discontinuation of the offending agent. Early diagnosis and withdrawal of the drug may prevent unnecessary morbidity and disability.

Incidence of major tendon ruptures and anterior cruciate ligament tears in US Army soldiers

BACKGROUND

Although a rare event, the prevalence of major tendon rupture has increased in recent decades. Identification of risk factors is important for prevention purposes.

HYPOTHESIS

Race is a risk factor for major tendon ruptures.

STUDY DESIGN

Cohort study (prevalence); Level of evidence, 2.

METHODS

All patients admitted for surgical management of a rupture of a major tendon at Womack Army Medical Center, Fort Bragg, North Carolina, in 1995 and 1996 were identified and evaluated for risk factors.

RESULTS

The authors identified 52 major tendon ruptures: 29 Achilles, 12 patellar, 7 pectoralis major, and 4 quadriceps tendon ruptures. All patients were active-duty soldiers, and 1 was a female soldier. Forty-one tendon ruptures occurred among black soldiers, 8 occurred among white soldiers, and 3 occurred among Latino soldiers. The population at risk included 93,224 exposures during the 2-year period, of which 67.1% were white, 24.5% were black, and 8.4% were self-classified as other race. The rate ratio for tendon rupture, adjusted for gender and age, was 13.3 (95% confidence interval, 6.2-28.5) between blacks and whites and 2.9 (95% confidence interval, 0.8-10.9) between Latinos and whites.

CONCLUSION

The rate of major tendon rupture was 13 times greater for black men in this study population when compared with whites. Interventions among those at a higher risk for injury should be considered.

Fluoroquinolones-Induced Tendinitis and Tendon Rupture in Kidney Transplant Recipients: 2 Cases and a Review of the Literature

Fluoroquinolones are an important class of synthetic antibiotics and their use recently expanded with a new activity against Gram positive and anaerobics. In the literature many side effects were documented and, among them, tendinitis and subsequent tendon rupture are important causes of morbidity. The incidence is 0.14% to 0.4% but, in the kidney recipient population, the phenomenon is even more common (incidence, 12.2%-15.6%). Advanced age seems to be the most significant risk factor. Long period of hemodialysis, diabetes mellitus, hyperparathyroidism, rheumatic diseases, gout, and corticosteroids are the other predisposing factors in kidney recipients, even if they are still under discussion. All of these risk factors can create a synergistic toxicity or at least an additive effect. A case of tendinitis and a case of bilateral Achilles tendon ruptures in 2 kidney recipients are described and a brief discussion of the literature is presented.

Active Expression of Matrix Metalloproteinase-13 mRNA in the Granulation Tissue of Equine Superficial Digital Flexor Tendinitis

The DNA microarray analysis for matrix metalloproteinase (MMP)-related mRNA expression in equine superficial digital flexor tendinitis indicated that mRNA level of MMP-13 was apparently up-regulated in the tendinitis as compared to normal tendon. In situ hybridization also revealed that fibroblastic cells proliferated in the granulation tissue generated in the tendinitis actively expressed MMP-13 mRNA. On the other hand, in normal tendon, a few fibroblastic cells and vascular components lied in the endotenon barely expressed its mRNA, but other cellular components in the tendon bundle were not positively hybridized. As mentioned above, MMP-13 but not other collagenases or gelatinases, may play an important role in tendon injuries in the racehorses.