COL-3 inhibition of collagen fragmentation in ruptured cranial cruciate ligament explants from dogs with stifle arthritis

Inhibition of collagen fragment generation in canine cranial cruciate ligament (CCL) explant cultures by the matrix metalloprotease inhibitor (6-demethyl)-6-deoxy-4-dedimethylamino tetracycline (COL-3) was studied. Cranial cruciate ligament specimens were collected from dogs with inflammatory stifle arthritis/CCL rupture and dogs with normal stifles. Explant cultures from each CCL specimen included one COL-3 treated explant and a baseline control; explants from 12 ruptured CCLs were prepared in triplicate and a protease inhibitor cocktail positive control was used. Explant supernatants were analyzed for generation of collagen fragments after two days. Treatment of ruptured CCL explants with 10(-4)M COL-3 decreased generation of collagen fragments. The extent of this inhibition was increased in explants treated with a protease inhibitor cocktail. Generation of collagen fragments was increased in ruptured CCLs, when compared with intact CCLs. It is concluded that generation of collagen fragments was increased in pathological ruptured CCL explants. This degradation could be significantly inhibited in vitro by 10(-4)M COL-3.

Anatomic double-bundle anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) reconstruction is one of the most common procedures performed by orthopaedic surgeons. The procedure has improved significantly since its inception in 1900 and continues to be intensively studied with outcomes receiving considerable attention. Traditional ACL reconstruction techniques have focused on one portion of the ACL--the anteromedial bundle. Single-bundle ACL reconstruction is the criterion standard and has provided good to excellent results, with many athletes being able to return to sports; however, recently, some authors have noted persistent instability with functional testing and degenerative radiographic changes after single-bundle ACL reconstruction. As a result, several centers have attempted to improve upon the single-bundle technique by reconstructing both the anteromedial and posterolateral bundles of the ACL. This article will present the embryologic, anatomic, and biomechanical rationale for double-bundle ACL reconstruction. In addition, the latest outcomes of double-bundle ACL reconstruction will be presented.

Collagen fragmentation in ruptured canine cranial cruciate ligament explants

Collagen fragmentation in cranial cruciate ligament (CCL) explants and stifle synovial fluid was investigated in dogs with ruptured and intact CCL. Cathepsin K and tartrate-resistant acid phosphatase (TRAP) activities were determined in CCL explant supernatants. Formation of collagen fragments was determined in explant supernatants and stifle synovial fluid. Cathepsin K(+) and TRAP(+) cells were stained specifically in histological sections of CCL. Formation of telopeptide collagen fragments was increased in ruptured CCL explants and stifle synovial fluid from dogs with ruptured CCL. In ruptured CCL explants, release of collagen fragments was associated with extracellular release of TRAP and the presence of cathepsin K(+) cells within CCL tissue. Cathepsin K(+) and TRAP(+) cells were only seen in ruptured CCL. It was concluded that infiltration of the CCL with TRAP(+) cells in dogs with CCL rupture is associated with increased collagenolysis. It is hypothesized that recruitment and activation of TRAP(+) mononuclear cells within the synovium and CCL precipitates CCL rupture through upregulation of collagenolytic enzymes and collagen degradation.

Characterization of sulfate, proline, and glucose transport systems in anterior cruciate and medial collateral ligament cells

The present study was undertaken to define the nature of key transport processes for sodium, glucose, proline, and sulfate in primary culture of canine anterior cruciate ligament (ACL) and medial collateral ligament (MCL) cells. Uptake studies using radiolabeled isotopes were performed and Na,K-ATPase activity was determined in cell lysates. At 25 degrees C both ACL and MCL cells showed a significant uptake of 86Rb. Ouabain inhibited Rb uptake by 55% in ACL cells and by 60% in MCL cells. The transport activity of Na,K-ATPase in intact cells was calculated to be 57 and 71 nmol.(mg protein)-1.(15 min)-1, respectively. The enzymatic activity of Na,K-ATPase in cell lysates was observed to be 104 for ACL cells and 121 nmol.(mg protein)-1.(15 min)-1 for MCL cells. Cytochalasin B, a known inhibitor of sodium-independent D-glucose transport, completely inhibited D-glucose uptake in ACL and MCL cells. Removal of Na+ or addition of 10-5 mol/L phlorizin, a potent inhibitor of the sodium-D-glucose cotransporter, did not alter D-glucose uptake, suggesting that glucose entered the cells using a sodium-independent pathway. Both ACL and MCL cells exhibited high sulfate uptake that was not altered by replacement of Na+ by N-methyl-D-glucamine, whereas DIDS, an inhibitor of sulfate/anion exchange abolished sulfate uptake in both cell types. Thus, neither cell type seems to possess a sodium-sulfate cotransport system. Rather, sulfate uptake appeared to be mediated by sulfate/anion exchange. Proline was rapidly taken up by ACL and MCL cells and its uptake was reduced by 85% when Na+ was replaced by N-methyl-D-glucamine, indicating that proline entered the cells via sodium-dependent cotransport systems. The data demonstrate that both ACL and MCL cells possess a highly active sodium pump, a secondary active sodium-proline cotransport system, and sodium-independent transport systems for D-glucose and sulfate.

Differential MMP-2 activity of ligament cells under mechanical stretch injury: an in vitro study on human ACL and MCL fibroblasts

Recent studies have revealed that following injuries, ligament tissues such as anterior cruciate ligaments (ACL), release large amounts of matrix metalloproteinases (MMPs). These enzymes have a devastating effect on the healing process of the injured ligaments. Although these enzymes are produced following ligament injuries, because of different healing capacities seen between the medial collateral ligament (MCL) and ACL, we were curious to find if the MMP activity was expressed and modulated differently in these tissues. For this purpose ACL and MCL fibroblasts were seeded on equi-biaxial stretch chambers and were stretched in different levels. The stretched cells were assayed using Zymography, Western Blot and global MMP activity assays. The results showed that within 72 h after injurious stretch, production of 72 kD pro-MMP-2 increased in both ACL and MCL. However, the ACL fibroblasts generated significantly more pro-MMP-2 than the MCL fibroblasts. Furthermore we found in ACL pro-MMP-2 was converted more into active form. With 4-aminophenyl mercuric acetate (APMA) treatment, large amounts of pro-MMP-2 were converted into active form in both. This indicates that there is no significant difference between ACL and MCL fibroblasts in post-translational modification of MMP-2. The fluorescent MMP activity assays revealed that the MMP family activities were higher in the injured ACL fibroblasts than the MCL. Since the MMPs are critically involved in extracellular matrix (ECM) turnover, these findings may explain one of the reasons why the injured ACL hardly repairs. The higher levels of active MMP-2 seen in the ACL injuries may disrupt the delicate balance of ECM remodeling process. These results suggest that the generation and modulation of MMP-2 may be directly involved in the different responses seen in ACL and MCL injuries.

Localization of Cathepsin K and Tartrate-Resistant Acid Phosphatase in Synovium and Cranial Cruciate Ligament in Dogs with Cruciate Disease

OBJECTIVE

To localize cathepsin K and tartrate-resistant acid phosphatase (TRAP) in synovium and cranial cruciate ligament (CCL) of dogs with cruciate disease.

ANIMALS

Dogs (n=15) with cruciate disease and ruptured CCL, and 12 dogs with intact CCL.

METHODS

Synovium and CCL were examined histologically and cells containing cathepsin K or TRAP were identified immunohistochemically and histochemically, respectively.

RESULTS

Increased cellular localization of cathepsin K and TRAP was detected in synovium and ruptured CCL in dogs with cruciate disease, when compared with tissues from dogs with intact CCL. Inflammation of synovium with TRAP+ macrophage-like cells was seen in 73% of dogs with CCL disease, but was not seen in dogs with intact CCL. The presence of cathepsin K and TRAP protein in synovium and CCL tissues was significantly correlated in dogs with CCL rupture.

CONCLUSION

Inflammation of the epiligament of ruptured CCL with cathepsin K+ and TRAP+ macrophage-like cells forms part of a similar, more generalized chronic inflammatory change within the periarticular tissues of the stifle of a large proportion of dogs with CCL rupture.

CLINICAL RELEVANCE

Production of matrix-degrading enzymes by the synovium may induce progressive pathologic rupture of the CCL. Therefore, these collagenolytic pathways may offer a novel target for medical therapy of joint inflammation in canine patients with cruciate disease.

Expression of matrix metalloprotease and tissue inhibitor of metalloprotease genes in human anterior cruciate ligament

Women are more susceptible to anterior cruciate ligament (ACL) injuries than men performing similar athletic activities. Because tissue remodeling may affect ligament strength, we assessed expression of tissue remodeling effector genes in the human ACL. Specifically, we surveyed ACL for RNAs encoding all known matrix metalloproteases (MMPs) and tissue inhibitors of metalloproteases (TIMPs) by reverse transcription/polymerase chain reaction (RT-PCR). These experiments revealed that mRNAs encoding nine of sixteen MMPs and all four TIMPs are present in the normal ACL. The nine expressed proteases were MMPs 1-3, 7, 9, 11, 14, and 17 (collagenase 1, gelatinase A, stromelysin 1, matrilysin, gelatinase B, stromelysin 3, and membrane types 1 and 4, respectively), and MMP-18. Genes for MMPs 8, 10, 12, 13, 15, and 16 appeared not to be expressed in ACL, as their mRNAs were not detected using RT-PCR conditions that did yield positive signals from other tissues (testis or bone). We conclude that numerous genes encoding tissue remodeling effector proteins are expressedin the human ACL.

Collagen remodeling in the anterior cruciate ligament associated with developing spontaneous murine osteoarthritis

The initiating factors in primary, idiopathic osteoarthritis are unknown, the characteristic bone and cartilage changes being late features of the disease. We have proposed that biochemical cruciate ligament alteration may be important in early osteoarthritis by mediating loading consequences on the bone and cartilage. Using the widely accepted STR/ORT mouse model of spontaneous osteoarthritis we have found biochemical evidence that, before radiological signs of osteoarthritis develop, cruciate ligament collagen metabolism is upregulated in the STR/ORT mouse when compared to controls. Also, importantly, at this time the anterior cruciate ligament is weaker in STR/ORT mice than in controls. This is the first biochemical evidence to show that alterations in cruciate ligament metabolism occur early in the etiopathogenesis of idiopathic, primary osteoarthritis.

Collagenase activity in anterior cruciate ligament: protective role of the synovial sheath

To evaluate the protective role of the synovial sheath of the anterior cruciate ligament (ACL), we have developed a synovectomy model that exposes the ACL substance to the intra-articular environment with and without hemarthrosis. Histology and the level of collagenase activity were studied to assess intrinsic ligament alterations. The treatment groups studied were as follows: ACLs of sham-operated knees receiving arthrotomy only, ACLs of knees receiving arthrotomy and acute hemarthrosis, ACLs of knees that underwent synovectomy, and ACLs of knees that underwent both synovectomy and acute hemarthrosis. All animals were killed 10 days postoperatively for gross, histological, and biochemical assessment. Histologically at 10 days ACLs experiencing synovectomy and ACLs having synovectomy plus hemarthrosis revealed marked hypocellular areas. Biochemical results indicate that synovectomy is the treatment mainly responsible for the observed increase in ACL collagenase activity. Hemarthrosis alone clearly had no effect, although hemarthrosis coupled with synovectomy appeared to further increase the amount of active collagenase present in the ACLs. This study indicates that, with exposure of the ACL substance to the synovial fluid or with hemarthrosis after synovectomy, there is an increase in the degradative activity of the ACL. The protective role of the synovial sheath suggests that the synovial sheath injury associated with acute ACL rupture may allow for exposure of the ligament substance to the degradative effects of the synovial environment and associated hemarthrosis.