Tenocytes from ruptured and tendinopathic achilles tendons produce greater quantities of type III collagen than tenocytes from normal achilles tendons. An in vitro model of human tendon healing

Functional anatomy of the Achilles tendon

The Achilles tendon is the strongest and thickest tendon in the human body. It is also the commonest tendon to rupture. It begins near the middle of the calf and is the conjoint tendon of the gastrocnemius and soleus muscles. The relative contribution of the two muscles to the tendon varies. Spiralisation of the fibres of the tendon produces an area of concentrated stress and confers a mechanical advantage. The calcaneal insertion is specialised and designed to aid the dissipation of stress from the tendon to the calcaneum. The insertion is crescent shaped and has significant medial and lateral projections. The blood supply of the tendon is from the musculotendinous junction, vessels in surrounding connective tissue and the osteotendinous junction. The vascular territories can be classified simply in three, with the midsection supplied by the peroneal artery, and the proximal and distal sections supplied by the posterior tibial artery. This leaves a relatively hypovascular area in the mid-portion of the tendon where most problems occur. The Achilles tendon derives its innervation from the sural nerve with a smaller supply from the tibial nerve. Tenocytes produce type I collagen and form 90% of the cellular component of the normal tendon. Evidence suggests ruptured or pathological tendon produce more type III collagen, which may affect the tensile strength of the tendon. Direct measurements of forces reveal loading in the Achilles tendon as high as 9 KN during running, which is up to 12.5 times body weight.

Regeneration of bone- and tendon/ligament-like tissues induced by gene transfer of bone morphogenetic protein-12 in a rat bone defect

Members of the bone morphogenetic protein (BMP) family have diverse physiological roles. For instance, BMP-2 stimulates osteogenesis, while BMP-12 induces the formation of tendon/ligament-like tissues. Here, we designed a study to determine whether BMP-12 has bone and/or cartilage regeneration abilities similar to those of BMP-2. We implanted plasmid vectors encoding either BMP-2 or BMP-12 in rats with femur defects, and monitored the bone healing process for 8-weeks. The BMP-12 transgene induced prominent fibrogenesis by 2 weeks, with bone substitution occurring by 8 weeks. BMP-2, however, was associated predominantly with osteogenesis throughout the 8 week period. Thus, we conclude that BMP-12 does not function similarly to BMP-2 during bone healing. Further work is needed to better understand the mechanisms by which it stimulates bony growths to replace the connective tissues formed during the first stages of bone healing.

Fibril morphology and tendon mechanical properties in patellar tendinopathy: effects of heavy slow resistance training

BACKGROUND

Patellar tendinopathy is characterized by pathologic abnormalities. Heavy slow resistance training (HSR) is effective in the management of patellar tendinopathy, but the underlying functional mechanisms remain elusive.

PURPOSE

To investigate fibril morphology and mechanical properties in patellar tendinopathy and the effect of HSR on these properties.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Eight male patients with patellar tendinopathy completed 12 weeks of HSR. Nine healthy subjects served as controls. Assessments were conducted at baseline and at 12 weeks. Patients assessed symptoms/function and maximal tendon pain during activity. Tendon biopsy samples were analyzed for fibril density, volume fraction, and mean fibril area. Tendon mechanical properties were assessed using force and ultrasonography samplings.

RESULTS

Patients improved in symptoms/function (P = .02) and maximal tendon pain during activity (P = .008). Stiffness and modulus of control and tendinopathy tendons were similar at baseline. Stiffness remained unaffected in control tendons (3487 +/- 392 to 3157 +/- 327 N/mm, P = .57) but declined in tendinopathic tendons at 12 weeks (3185 +/- 187 to 2701 +/- 201 N/mm, P = .04). At baseline, fibril volume fraction was equal, fibril density smaller (P = .03), and mean fibril area tended to be higher in tendinopathy versus controls (P = .07). Fibril morphology remained unchanged in controls but fibril density increased (70% +/- 18%, P = .02) and fibril mean area decreased (-26% +/- 21%, P = .04) in tendinopathic tendons after HSR.

CONCLUSION

Fibril morphology is abnormal in tendinopathy, but tendon mechanical properties are not. Clinical improvements after HSR were associated with changes in fibril morphology toward normal fibril density and mean fibril area. Heavy slow resistance training improved the clinical outcome of patellar tendinopathy, and these improvements were associated with normalization of fibril morphology, most likely due to a production of new fibrils.

Ibuprofen upregulates expressions of matrix metalloproteinase-1, -8, -9, and -13 without affecting expressions of types I and III collagen in tendon cells

Nonsteroidal antiinflammatory drugs are widely used to treat sports-related tendon injuries or tendinopathy. This study was designed to investigate the effect of ibuprofen on expressions of types I and III collagen, as well as collagen-degrading enzymes including matrix metalloproteinase (MMP)-1, -2, -8, -9, and -13. Rat Achilles tendon cells were treated with ibuprofen and then underwent MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Reverse transcription-polymerase chain reaction was used to evaluate mRNA expressions of types I and III collagen, MMP-1, -2, -8, -9, and -13. Protein expressions of types I and III collagen, MMP-1, -8, and -13 were determined by Western blot analysis. Gelatin zymography was used to evaluate the enzymatic activities of MMP-2 and MMP-9. The results revealed that ibuprofen upregulated expressions of MMP-1, -8, -9, and -13, both at mRNA and protein levels. There was no effect of ibuprofen on mRNA and protein expressions of types I and III collagen. Gelatin zymography revealed that the enzymatic activity of MMP-9 was upregulated after ibuprofen treatment. In conclusion, ibuprofen upregulates the expressions of collagenases including MMP-1, -8, -9, and -13 without affecting the expressions of types I and III collagen. These findings suggest a molecular mechanism potentially accounting for the inhibition of tendon healing by ibuprofen.

A new measurement of heel-rise endurance with the ability to detect functional deficits in patients with Achilles tendon rupture

Studies evaluating treatment effects on muscle function after an Achilles tendon rupture often use various tests for evaluating calf muscle strength. However, these tests rarely demonstrate the difference between treatment groups; therefore, new tests with a higher ability to detect possible differences in outcome are needed. The purpose of this study was to evaluate the validity and ability to detect differences in outcome of a heel-rise work test that would measure both the height of each heel-rise and the number of repetitions. Seventy-eight patients (65 men and 13 women) at a mean (standard deviation) age of 42 (9) years with Achilles tendon ruptures were included. The patients were evaluated with the new heel-rise test at 6 and 12 months after injury. The limb symmetry index (LSI = involved/uninvolved x 100) was calculated to determine the size of the difference in function between the injured and the uninjured side. The heel-rise height differed significantly between the injured and uninjured sides at the 6- and 12-month evaluations (P < 0.001). At the 6-month evaluation, the patients had achieved a mean LSI of 84% on the number of repetitions parameter but only a mean LSI of 61% on the work parameter. At the 12-month evaluation the mean, LSI of the heel-rise repetition parameter was 95%, indicating that the patients had fully recovered function, but on the work parameter the mean LSI was only 76%. The heel-rise work test in the present study has good validity and greater ability to detect differences between the injured and the uninjured sides than a test that measures only the number of heel-rise repetitions in patients with Achilles tendon rupture.

Effectiveness of microRNA in Down-regulation of TGF-beta gene expression in digital flexor tendons of chickens: in vitro and in vivo study

PURPOSE

Transforming growth factor (TGF)-beta is considered to be responsible for the formation of scars such as adhesions around healing digital flexor tendons. We proposed to deliver microRNAs (miRNAs) to silence expression of the TGF-beta1 gene and to investigate the effectiveness of miRNAs in down-regulation of the TGF-beta1 gene in vitro and in vivo.

METHODS

We designed and engineered 4 miRNAs according to genetic sequences of chicken TGF-beta1. Four plasmid vectors harboring the respective engineered miRNAs and 1 control vector were constructed. We transfected 30 wells of cultured tenocytes with these vectors and harvested them 48 hours later. The gene expression levels were quantified using real-time polymerase chain reactions. Subsequently, the miRNA that most effectively silenced TGF-beta gene in vitro was tested on 25 chickens in vivo. The miRNA and control vectors were injected into the injured tendons, respectively. At 1 and 6 weeks after surgery, the tendons were analyzed for gene expression and protein production.

RESULTS

In both in vitro and in vivo settings, delivery of miRNA to the tendon substantially down-regulated expression of the TGF-beta gene but did not affect expression of the collagen I gene. In the healing tendon, TGF-beta gene expression was significantly down-regulated by 50% to 60% at 1 and 6 weeks. At 6 weeks, the collagen III gene expression was significantly down-regulated by 55% at 6 weeks and the connective tissue growth factor gene was significantly down-regulated by 25%. At 6 weeks, TGF-beta protein was substantially decreased.

CONCLUSIONS

MicroRNA significantly down-regulates expression of the TGF-beta in vitro and in vivo. Application of miRNA did not down-regulate expression of the collagen I, but downregulated the collagen III gene. Application of miRNA treatment to modulate TGF-beta expression holds great promise in preventing tendon adhesion formation.

Accelerated healing of the rat Achilles tendon in response to autologous conditioned serum

BACKGROUND

Despite advances in the treatment of ruptured Achilles tendon, imperfections of endogenous repair often leave patients symptomatic. Local administration of autologous conditioned serum (ACS) in patients with inflammatory, degenerative conditions has shown beneficial effects.

PURPOSE

Because ACS also contains growth factors that should accelerate tendon healing, we studied the effect of ACS on the healing of transected rat Achilles tendon.

STUDY DESIGN

Controlled laboratory study.

METHODS

In preliminary in vitro experiments, rat tendons were incubated with ACS and the effect on the expression of Col1A1 and Col3A1 was assessed by real-time quantitative polymerase chain reaction. To test its effect in vivo, the Achilles tendons of 80 Sprague Dawley rats were transected and sutured back together. Ten rats from each group (ACS group, n = 40; control group, n = 40) were euthanized at 1, 2, 4, and 8 weeks postoperatively for biomechanical (n = 7) and histologic (n = 3) testing. Lysyl oxidase activity was assayed by a flurometric assay. The organization of repair tissue was assessed histologically with hematoxylin and eosin- and with Sirius red-stained sections, and with immunohistochemistry.

RESULTS

Tendons exposed to ACS in vitro showed a greatly enhanced expression of the Col1A1 gene. The ACS-treated tendons were thicker, had more type I collagen, and an accelerated recovery of tendon stiffness and histologic maturity of the repair tissue. However, there were no differences in the maximum load to failure between groups up to week 8, perhaps because lysyl oxidase activities were unchanged.

CONCLUSION AND CLINICAL RELEVANCE

Overall, our study demonstrates that treatment with ACS has the potential to improve Achilles tendon healing and should be considered as a treatment modality in man. However, as strength was not shown to be increased within the parameters of this study, the clinical importance of the observed changes in humans still needs to be defined.

Effect of eccentric exercise program for early tibialis posterior tendinopathy

BACKGROUND

Morphology and vascularization of painful tibialis posterior (TP) tendons before and after an intervention targeting the degenerated tendon were examined. Functional status and pain level were also assessed.

MATERIALS AND METHODS

A10-week twice daily, progressive eccentric tendon loading, calf stretching program with orthoses was implemented with ten, early stage TP tendinopathy subjects. TP tendons were imaged by grayscale and Doppler ultrasound at INITIAL and POST evaluations to assess the tendon's morphology and signs of neovascularization. The Foot Functional Index (FFI), Physical Activity Scale (PAS), 5-Minute Walk Test, and single heel raise (SHR) test were completed at INITIAL and POST evaluations. The Global Rating Scale (GRS) was completed at 6 months followup. One-way ANOVA was used to compare the FFI at INITIAL, POST, and 6-MONTH time points. Paired t-tests were used to compare means between the remaining variables. The level of significance was p = 0.05.

RESULTS

There was a significant difference in FFI total, pain, and disability at the three time-points. Post-hoc paired t-tests revealed that the FFI scores were lower for the total score and pain and disability subcategories when comparing from INITIAL to POST and INITIAL to 6-MONTH evaluations (p < 0.05 for all). The number of SHR increased significantly on the involved side from INITIAL to POST evaluation (p = 0.041). The GRS demonstrated minimum clinically important differences for improvements in symptoms at 6-MONTH. Tendon morphology and vascularization remained abnormal following the intervention.

CONCLUSION

A 10-week tendon specific eccentric program resulted in improvements in symptoms and function without changes in tendon morphology or neovascularization.

Management of tendinopathy

Overuse disorders of tendons, or tendinopathies, present a challenge to sports physicians, surgeons, and other health care professionals dealing with athletes. The Achilles, patellar, and supraspinatus tendons are particularly vulnerable to injury and often difficult to manage successfully. Inflammation was believed central to the pathologic process, but histopathologic evidence has confirmed the failed healing response nature of these conditions. Excessive or inappropriate loading of the musculotendinous unit is believed to be central to the disease process, although the exact mechanism by which this occurs remains uncertain. Additionally, the location of the lesion (for example, the midtendon or osteotendinous junction) has become increasingly recognized as influencing both the pathologic process and subsequent management. The mechanical, vascular, neural, and other theories that seek to explain the pathologic process are explored in this article. Recent developments in the nonoperative management of chronic tendon disorders are reviewed, as is the rationale for surgical intervention. Recent surgical advances, including minimally invasive tendon surgery, are reviewed. Potential future management strategies, such as stem cell therapy, growth factor treatment, and gene transfer, are also discussed.

Acute ruptures of the achilles tendon

The Achilles tendon (AT) is the most frequently ruptured tendon in the human body, but the etiology of AT ruptures is still not completely understood. Percutaneous repair and conservative management are viable alternatives to open surgery, which carries higher complication rates and is the most costly of the 3 management options. Individual patients will have different needs due to their age, occupation, or level of sporting activity. If the studies reporting a rising incidence of AT rupture are accurate, the field of AT surgery will become an increasingly important one for orthopedic surgeons. A major problem in the evaluation of the outcome of management of AT ruptures has been the lack of a universally accepted scoring system for the evaluation of results of management of AT rupture. The AT Total Rupture Score is a self-administered instrument with high clinical utility, and it can be used for measuring the outcome, related to symptoms and physical activity, after treatment in patients with a total AT rupture. Future developments may include the use of adhesives in tendon surgery. An understanding of the role, which cytokines play in tendon healing may also lead to the advent of new treatments, possibly based on gene therapy. However, such novel interventions are unlikely to be in routine clinical use for some time.

Maturational alterations in gap junction expression and associated collagen synthesis in response to tendon function

Energy-storing tendons including the equine superficial digital flexor tendon (SDFT) contribute to energetic efficiency of locomotion at high-speed gaits, but consequently operate close to their physiological strain limits. Significant evidence of exercise-induced microdamage has been found in the SDFT which appears not to exhibit functional adaptation; the degenerative changes have not been repaired by the tendon fibroblasts (tenocytes), and are proposed to accumulate and predispose the tendon to rupture during normal athletic activity. The anatomically opposing common digital extensor tendon (CDET) functions only to position the digit, experiencing significantly lower levels of strain and is rarely damaged by exercise. A number of studies have indicated that tenocytes in the adult SDFT are less active in collagen synthesis and turnover than those in the immature SDFT or the CDET. Gap junction intercellular communication (GJIC) is known to be necessary for strain-induced collagen synthesis by tenocytes. We postulate therefore that expression of GJ proteins connexin 43 and 32 (Cx43; Cx32), GJIC and associated collagen expression levels are high in the SDFT and CDET of immature horses, when the SDFT in particular grows significantly in cross-sectional area, but reduce significantly during maturation in the energy-storing tendon only. The hypothesis was tested using tissue from the SDFT and CDET of foetuses, foals, and young adult Thoroughbred horses. Cellularity and the total area of both Cx43 and Cx32 plaques/mm(2) of tissue reduced significantly with maturation in each tendon. However, the total Cx43 plaque area per tenocyte significantly increased in the adult CDET. Evidence of recent collagen synthesis in the form of levels of neutral salt-soluble collagen, and collagen type I mRNA was significantly less in the adult compared with the immature SDFT; procollagen type I amino-propeptide (PINP) and procollagen type III amino-propeptide (PIIINP) levels per mm(2) of tissue and PINP expression per tenocyte also decreased with maturation in the SDFT. In the CDET PINP and PIIINP expression per tenocyte increased in the adult, and exceeded those in the adult SDFT. The level of PINP per mm(2) was greater in the adult CDET than in the SDFT despite the higher cellularity of the latter tendon. In the adult SDFT, levels of PIIINP were greater than those of PINP, suggesting relatively greater synthesis of a weaker form of collagen previously associated with microdamage. Tenocytes in monolayers showed differences in Cx43 and Cx32 expression compared with those in tissue, however there were age- and tendon-specific phenotypic differences, with a longer time for 50% recovery of fluorescence after photobleaching in adult SDFT cells compared with those from the CDET and immature SDFT. As cellularity reduces following growth in the SDFT, a failure of the remaining tenocytes to show a compensatory increase in GJ expression and collagen synthesis may explain why cell populations are not able to respond to exercise and to repair microdamage in some adult athletes. Enhancing GJIC in mature energy-storing tendons could provide a strategy to increase the cellular synthetic and reparative capacity.

Achilles tendon ruptures, re rupture with revision surgery, tendinosis, and insertional disease

Achilles tendon pathology is one of the more common conditions encountered by the foot and ankle surgeon. While it most frequently affects the athletic population, it can also lead to significant morbidity in the older and sedentary patient. The etiology of Achilles tendon dysfunction is multifactorial and has been found to be associated with overuse injury, training error, malalignment of the lower extremity, inflammatory disorders, and intrinsic disease or degeneration. Achilles tendon disorders have been classified temporally as acute and chronic, with the later subdivided into insertional and non-insertional (intrinsic) involvement. Histopathology has contributed a great deal to the understanding of disease process. Classification systems have been developed in an attempt to determine methods of treatment and prognosis. This article reviews the clinical spectrum of disease and presents contemporary treatment options.

Collagen I membranes for tendon repair: effect of collagen fiber orientation on cell behavior

Tendons have poor spontaneous regenerative capabilities, and complete regeneration is never achieved despite intensive remodeling. In this in vitro study, we characterized two multilamellar collagen I membranes differing in the arrangement of collagen fiber deposition (oriented vs. nonoriented) and compared their mechanical properties. Human dermal fibroblasts and tenocytes were seeded on the two membranes to evaluate the effect of fiber orientation on cell viability and cytoskeletal organization. Results demonstrate that the multilamellar collagen I membrane with oriented fibers has the better mechanical properties and affords optimum cell proliferation and adhesion. Its fiber arrangement provides an instructive pattern for cell growth and may serve to guide the alignment of cells migrating from the ends of a crushed or frayed tendon to obtain a strong, correctly structured tendon, thus providing a viable clinical option for tendon repair.

The mitochondria targeted antioxidant MitoQ protects against fluoroquinolone-induced oxidative stress and mitochondrial membrane damage in human Achilles tendon cells

Tendinitis and tendon rupture during treatment with fluoroquinolone antibiotics is thought to be mediated via oxidative stress. This study investigated whether ciprofloxacin and moxifloxacin cause oxidative stress and mitochondrial damage in cultured normal human Achilles' tendon cells and whether an antioxidant targeted to mitochondria (MitoQ) would protect against such damage better than a non-mitochondria targeted antioxidant. Human tendon cells from normal Achilles' tendons were exposed to 0-0.3 mM antibiotic for 24 h and 7 days in the presence of 1 microM MitoQ or an untargeted form, idebenone. Both moxifloxacin and ciprofloxacin resulted in up to a 3-fold increase in the rate of oxidation of dichlorodihydrofluorescein, a marker of general oxidative stress in tenocytes (p<0.0001) and loss of mitochondrial membrane permeability (p<0.001). In cells treated with MitoQ the oxidative stress was less and mitochondrial membrane potential was maintained. Mitochondrial damage to tenocytes during fluoroquinolone treatment may be involved in tendinitis and tendon rupture.

Differential regulation of gene expression in isolated tendon fascicles exposed to cyclic tensile strain in vitro

Mechanical stimulus is a regulator of tenocyte metabolism. The present study investigated temporal regulation of the expression of selected genes by tenocytes in isolated fascicles subjected to tensile strain in vitro. Cyclic tensile strain with a 3% amplitude superimposed on a 2% static strain was provided for 10 min, followed by either an unstrained period or continuous cyclic strain until the end of a 24-h incubation period. mRNA expression of selected anabolic and catabolic genes were evaluated with quantitative PCR at 10 min, 1 h, 6 h, and 24 h. The application of 6-h cyclic strain significantly upregulated type III collagen mRNA expression in strained fascicles compared with unstrained controls, but no alterations were observed in mRNA expression of type I collagen and biglycan. Significant downregulation in the expression of the decorin core protein was observed in fascicles subjected to 24-h cyclic strain. MMP3 and MMP13 expression levels were upregulated by the application of 10 min of cyclic strain, followed by a progressive downregulation until the end of the incubation period in both the absence and the presence of the continuing cyclic strain. Accordingly, alterations in the expression of anabolic genes were limited to the upregulation of type III collagen by prolonged exposure to cyclic strain, whereas catabolic genes were upregulated by a small number of strain cycles and downregulated by a prolonged cyclic strain. These findings demonstrate distinctive patterns of mechanoregulation for anabolic and catabolic genes and help our understanding of tenocyte response to mechanical stimulation.

Therapeutic touch stimulates the proliferation of human cells in culture

OBJECTIVES

Our objective was to assess the effect of Therapeutic Touch (TT) on the proliferation of normal human cells in culture compared to sham and no treatment. Several proliferation techniques were used to confirm the results, and the effect of multiple 10-minute TT treatments was studied.

DESIGN

Fibroblasts, tendon cells (tenocytes), and bone cells (osteoblasts) were treated with TT, sham, or untreated for 2 weeks, and then assessed for [(3)H]-thymidine incorporation into the DNA, and immunocytochemical staining for proliferating cell nuclear antigen (PCNA). The number of PCNA-stained cells was also quantified. For 1 and 2 weeks, varying numbers of 10-minute TT treatments were administered to each cell type to determine whether there was a dose-dependent effect.

RESULTS

TT administered twice a week for 2 weeks significantly stimulated proliferation of fibroblasts, tenocytes, and osteoblasts in culture (p = 0.04, 0.01, and 0.01, respectively) compared to untreated control. These data were confirmed by PCNA immunocytochemistry. In the same experiments, sham healer treatment was not significantly different from the untreated cultures in any group, and was significantly less than TT treatment in fibroblast and tenocyte cultures. In 1-week studies involving the administration of multiple 10-minute TT treatments, four and five applications significantly increased [(3)H]-thymidine incorporation in fibroblasts and tenocytes, respectively, but not in osteoblasts. With different doses of TT for 2 weeks, two 10-minute TT treatments per week significantly stimulated proliferation in all cell types. Osteoblasts also responded to four treatments per week with a significant increase in proliferation. Additional TT treatments (five per week for 2 weeks) were not effective in eliciting increased proliferation compared to control in any cell type.

CONCLUSIONS

A specific pattern of TT treatment produced a significant increase in proliferation of fibro-blasts, osteoblasts, and tenocytes in culture. Therefore, TT may affect normal cells by stimulating cell proliferation.

Movin and Bonar scores assess the same characteristics of tendon histology

The Movin scoring system and its validated modifications and the Bonar scoring system are used to classify the histopathological findings of tendinopathy. We compared the reliability of these two different histopathological evaluation scores of tendon tissue. Tendon samples were harvested from 88 individuals (49 men, 39 women; mean age, 58.2 years) who underwent arthroscopic repair of a rotator cuff tear, and from five male patients who died of cardiovascular events (mean age, 69.6 years). A piece of supraspinatus tendon that was not directly involved in the tear was harvested en bloc within the intact middle portion of the tendon. Using hematoxylin and eosin staining and Alcian blue, slides were assessed using Bonar and Movin scores. The intraclass correlation was 0.921 (confidence interval 95% 0.790-0.963). Movin's and Bonar's scores have a high correlation and assess similar characteristics and variables of tendon abnormalities.

The basic science of tendinopathy

Tendinopathy is a common clinical problem with athletes and in many occupational settings. Tendinopathy can occur in any tendon, often near its insertion or enthesis where there is an area of stress concentration, and is directly related to the volume of repetitive load to which the tendon is exposed. Recent studies indicate tendinopathy is more likely to occur in situations that increase the "dose" of load to the tendon enthesis - including increased activity, weight, advancing age, and genetic factors. The cells in tendinopathic tendon are rounder, more numerous, and show evidence of oxidative damage and more apoptosis. These cells also produce a matrix that is thicker and weaker with more water, more immature and cartilage-like matrix proteins, and less organization. There is now evidence of a population of regenerating stem cells within tendon. These studies suggest prevention of tendinopathy should be directed at reducing the volume of repetitive loads to below that which induces oxidative-induced apoptosis and cartilage-like genes. The management strategies might involve agents or cells that induce tendon stem cell proliferation, repair and restoration of matrix integrity.

Histological analysis of achilles tendons in an overuse rat model

The purpose of this study was to design an animal model that induces histological changes in Achilles tendons consistent with those cited in the literature for human Achilles tendon disease. Sprague-Dawley rats were subjected to 10 degrees uphill treadmill running on a custom-designed rodent treadmill and at a speed of 17 meters per minute for 1 h, five times per week, over a 12-week treatment period. Subsequent histological analysis revealed alterations in the rat Achilles tendon that were generally consistent with those described in the literature for diseased human tendon tissues. These features include: decreased collagen fiber organization, more intense collagen staining, and increased cell nuclei numbers. Interestingly, though, immunohistochemical cell typing suggests that the observed increased cellularity does not include a significant inflammatory component but is secondary to increased numbers of endothelial cells (i.e., vascularization) and fibroblasts. These histological features likely represent a biological repair/remodeling response resulting from overuse running.

Can platelet-rich plasma enhance tendon repair? A cell culture study

BACKGROUND

Autologous platelet-rich plasma (PRP) application appears to improve tendon healing in traumatic tendon injuries, but basic knowledge of how PRP promotes tendon repair is needed.

HYPOTHESIS

Platelet-rich plasma has a positive effect on cell proliferation and collagen production and induces the production of matrix-degrading enzymes and endogenous growth factors by human tenocytes.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human tenocytes were cultured 14 days in 2% fetal calf serum medium complemented with 0%, 10%, or 20% vol/vol platelet-rich clot releasate ([PRCR] the active releasate of PRP) or platelet-poor clot releasate (PPCR). At day 4, 7, and 14, cell amount, total collagen, and gene expression of collagen I alpha 1 (COL1) and III alpha 1 (COL3), matrix metalloproteinases ([MMPs] MMP1, MMP3, and MMP13), vascular endothelial-derived growth factor (VEGF)-A, and transforming growth factor (TGF)-beta1 were analyzed.

RESULTS

Platelet numbers in PRP increased to 2.55 times baseline. Growth-factor concentrations of VEGF and platelet-derived growth factor (PDGF)-BB were higher in PRCR than PPCR. Both PRCR and PPCR increased cell number and total collagen, whereas they decreased gene expression of COL1 and COL3 without affecting the COL3/COL1 ratio. PRCR, but not PPCR, showed upregulation of MMP1 and MMP3 expression. Matrix metalloproteinase 13 expression was not altered by either treatment. PRCR increased VEGF-A expression at all time points and TGF-beta1 expression at day 4.

CONCLUSION

In human tenocyte cultures, PRCR, but also PPCR, stimulates cell proliferation and total collagen production. PRCR, but not PPCR, slightly increases the expression of matrix-degrading enzymes and endogenous growth factors.

CLINICAL RELEVANCE

In vivo use of PRP, but also of PPP to a certain extent, in tendon injuries might accelerate the catabolic demarcation of traumatically injured tendon matrices and promote angiogenesis and formation of a fibrovascular callus. Whether this will also be beneficial for degenerative tendinopathies remains to be elucidated.

Histopathology of the supraspinatus tendon in rotator cuff tears

BACKGROUND

Causes of rotator cuff pathology are poorly understood.

HYPOTHESIS

Macroscopically intact supraspinatus tendon may show profound light microscopy changes. These changes may be the pathogenic precursor to a subsequent rotator cuff tear.

STUDY DESIGN

Comparative laboratory study.

METHODS

Tendon samples were harvested from 88 individuals (49 men, 39 women; mean age, 58.2 years) who had sustained a rotator cuff tear and underwent arthroscopic repair of the lesion, and from 5 male patients who died of cardiovascular events (mean age, 69.6 years). A full-thickness supraspinatus tendon biopsy specimen was harvested en bloc within the arthroscopically intact middle portion of the tendon between the lateral edge of the tendon tear and the muscle-tendon junction. Slides stained with hematoxylin and eosin were interpreted twice by the same observer using a semiquantitative grading scale assessing fiber structure and arrangement, rounding of the nuclei, regional variations in cellularity, increased vascularity, decreased collagen stainability, and hyalinization. Intraobserver reliability of the subscore readings was calculated.

RESULTS

The mean pathologic sum-score of ruptured tendons was significantly greater than the mean pathologic score of control tendons (15.66 +/- 1.82 vs 3.7 +/- 2.31, P = .001). Within each specific category of tendon abnormalities, the control and ruptured tendons were significantly different (chi(2) test); all variables were significantly different (Mann-Whitney U test <0.05; P = .001). The agreement between the 2 readings ranged from 0.56 to 0.86 (kappa statistics).

CONCLUSION

Nonruptured supraspinatus tendons, even at an advanced age, and ruptured supraspinatus tendons are clearly part of 2 distinct populations.

CLINICAL RELEVANCE

During cuff repair, it is not necessary to excessively freshen the torn tendon to bleeding tissue: the macroscopically intact supraspinatus tendon is degenerated as well, and the failed healing response is not limited to the ends of the torn tendon.

Is cultured tendon fibroblast a good model to study tendon healing?

Cultured tendon fibroblasts (CTFs) from intact explants are widely used to study tendon healing in vitro. The significance of these findings may rely on similarities between CTFs and healing tendon fibroblasts in situ. Our purpose was to compare CTFs with fibroblasts cultured from healing tendons. We cultured CTFs from intact and healing tendons at day 7 and day 14 postinjury in a rat model of patellar donor site injury. The mRNA expression of COL1A1, COL3A1, decorin, and biglycan, with or without supplementation of 1 ng/mL TGF-beta1, was compared by quantitative real-time RT-PCR. The expression of proliferation cell nuclear antigen (PCNA) and alpha-smooth muscle actin (alpha-SMA) was determined by immunostain. COL3A1 and decorin mRNA in CTFs was lower as compared to day 7 healing fibroblasts, but its biglycan mRNA level was higher than day 14 healing fibroblasts. TGF-beta1 increased COL1A1 and decorin mRNA in CTFs, but decreased the mRNA of all four genes in day 7 healing tendon fibroblasts. CTFs exhibited lower PCNA immunopositivity as compared to day 7 and day 14 healing fibroblasts, but a higher alpha-SMA immunopositivity than cultured day 14 healing fibroblasts. These findings showed that CTFs did not resemble healing tendon cells with respect to major cellular activities related to tendon healing. Thus, fibroblasts from healing tendon may be a more appropriate model for studying cellular activities in tendon healing.

Freeze-dried tendon allografts as tissue-engineering scaffolds for Gdf5 gene delivery

Tendon reconstruction using grafts often results in adhesions that limit joint flexion. These adhesions are precipitated by inflammation, fibrosis, and the paucity of tendon differentiation signals during healing. In order to study this problem, we developed a mouse model in which the flexor digitorum longus (FDL) tendon is reconstructed using a live autograft or a freeze-dried allograft, and identified growth and differentiation factor 5 (Gdf5) as a therapeutic target. In this study we have investigated the potential of rAAV-Gdf5 -loaded freeze-dried tendon allografts as "therapeutically endowed" tissue-engineering scaffolds to reduce adhesions. In reporter gene studies we have demonstrated that recombinant adeno-associated virus (rAAV)-loaded tendon allografts mediate efficient transduction of adjacent soft tissues, with expression peaking at 7 days. We have also demonstrated that the rAAV-Gdf5 vector significantly accelerates wound healing in an in vitro fibroblast scratch model and, when loaded onto freeze-dried FDL tendon allografts, improves the metatarsophalangeal (MTP) joint flexion to a significantly greater extent than the rAAV-lacZ controls do. Collectively, our data demonstrate the feasibility and efficacy of therapeutic tendon allograft processing as a novel paradigm in tissue engineering in order to address difficult clinical problems such as tendon adhesions.

Light microscopic histology of supraspinatus tendon ruptures

We analysed the morphological features of the human surgical specimens of supraspinatus tendon from patients with rotator cuff tears. Tendon samples were harvested from 31 subjects (21 men and 10 women; mean age 51 years, range 38-64) who underwent arthroscopic repair of a rotator cuff tear, and from five male patients who died of cardiovascular events (mean age, 69.6 years). Histological examination was performed using Haematoxylin and Eosin, Masson's Trichrome and Van Gieson's connective tissue stain. The specimens were examined twice by the same examiner under white light and polarized light microscopy. Particular effort was made to assess any evidence of the changes associated with tendinopathy. Within each specific category of tendon abnormalities, the chi-square test showed significant differences between the control and ruptured tendons (P < 0.05). Using the kappa statistics, the agreement between the two readings ranged from 0.57 to 0.84. We found thinning and disorientation of collagen fibres and chondroid metaplasia to be more pronounced on the articular side of the specimens from patients with rotator cuff tear (P < 0.05). The present study provides a description of the histological architecture of human surgical specimens of normal supraspinatus tendon from patients with rotator cuff tears and demonstrates more frequent tendon changes on the articular side of the rotator cuff.

Evaluation of gene expression through qRT-PCR in cyclically loaded tendons: an in vivo model

An in vivo rabbit animal model for the tendinopathy, epicondylitis, was used to examine the effects of repetitive load on the expression of various genes associated with matrix remodeling. Following 80 h of cumulative load, tissue from the distal and proximal regions of the flexor digitorum profundus tendon was collected. Quantitative RT-PCR was used to asses mRNA levels of collagenase-1 (MMP-1), stromelysin (MMP-3), vascular endothelial growth factor (VEGF), connective tissue growth factor (CTGF), cyclooxygenase-2 (COX-2), interleukin-1beta (IL-1beta), type III collagen (COL-III) and fibronectin (FBRN). No significant differences in expression levels were found between loaded and unloaded limbs at either region of the tendon. The findings were unexpected as the same model has already demonstrated an increase in the density of cells staining for VEGF and CTGF. Different regulatory mechanisms between mRNA and protein expression or localized changes missed due to homogenization of the tissue samples, may explain the discrepancy in findings.

Gap junction protein expression and cellularity: comparison of immature and adult equine digital tendons

Injury to the energy-storing superficial digital flexor tendon is common in equine athletes and is age-related. Tenocytes in the superficial digital flexor tendon of adult horses appear to have limited ability to respond adaptively to exercise or prevent the accumulation of strain-induced microdamage. It has been suggested that conditioning exercise should be introduced during the growth period, when tenocytes may be more responsive to increased quantities or intensities of mechanical strain. Tenocytes are linked into networks by gap junctions that allow coordination of synthetic activity and facilitate strain-induced collagen synthesis. We hypothesised that there are reductions in cellular expression of the gap junction proteins connexin (Cx) 43 and 32 during maturation and ageing of the superficial digital flexor tendon that do not occur in the non-injury-prone common digital extensor tendon. Cryosections from the superficial digital flexor tendon and common digital extensor tendon of 5 fetuses, 5 foals (1-6 months), 5 young adults (2-7 years) and 5 old horses (18-33 years) were immunofluorescently labelled and quantitative confocal laser microscopy was performed. Expression of Cx43 and Cx32 protein per tenocyte was significantly higher in the fetal group compared with all other age groups in both tendons. The density of tenocytes was found to be highest in immature tissue. Higher levels of cellularity and connexin protein expression in immature tendons are likely to relate to requirements for tissue remodelling and growth. However, if further studies demonstrate that this correlates with greater gap junctional communication efficiency and synthetic responsiveness to mechanical strain in immature compared with adult tendons, it could support the concept of early introduction of controlled exercise as a means of increasing resistance to later injury.

Tendon and bone responses to a collagen-coated suture material

Tendon to bone integration after rotator cuff repair is not a reproducible process. During repair, bioabsorbable and nonabsorbable suture material is universally used to facilitate the procedure. Improving the biological architecture of inert suture might aid in overall tendon to bone healing. The objective of our study is to enhance the bone to tendon union by absorbing type I collagen onto high strength nonabsorbable polyester/polyethylene suture commonly used in rotator cuff surgery. Our purpose was to evaluate the tendon and bone cellular response to this novel coated suture compared to uncoated suture. Primary human osteoblasts (HOBs) and tenocytes were plated onto polyester/polyethylene suture that was either uncoated or coated with type I bovine collagen. Cell adhesion to the sutures was assayed at 24 hours. Proliferation was determined at 48 hours by measuring [3H]- Thymidine incorporation in cells attached to the sutures. At 24 and 48 hours, respectively, cells grown on the collagen-coated suture showed a significantly greater response measured by adhesion and proliferation than cells grown on uncoated suture. At five days of culture, alkaline phosphatase activity and protein synthesis was significantly greater on the collagen-coated suture compared to uncoated. Collagen-coated polyester/polyethylene suture appears to stimulate adhesion, proliferation alkaline phosphatase, and protein synthesis more than uncoated sutures, and therefore may aid in the tendon to bone incorporation process critical to rotator cuff repair.

Tenocyte responses to mechanical loading in vivo: a role for local insulin-like growth factor 1 signaling in early tendinosis in rats

OBJECTIVE

To investigate tenocyte regulatory events during the development of overuse supraspinatus tendinosis in rats.

METHODS

Supraspinatus tendinosis was induced by running rats downhill at 1 km/hour for 1 hour a day. Tendons were harvested at 4, 8, 12, and 16 weeks and processed for brightfield, polarized light, or transmission electron microscopy. The development of tendinosis was assessed semiquantitatively using a modified Bonar histopathologic scale. Apoptosis and proliferation were examined using antibodies against fragmented DNA or proliferating cell nuclear antigen, respectively. Insulin-like growth factor 1 (IGF-1) expression was determined by computer-assisted quantification of immunohistochemical reaction. Local IGF-1 signaling was probed using antibodies to phosphorylated insulin receptor substrate 1 (IRS-1) and ERK-1/2.

RESULTS

Tendinosis was present after 12 weeks of downhill running and was characterized by tenocyte rounding and proliferation as well as by glycosaminoglycan accumulation and collagen fragmentation. The proliferation index was elevated in CD90+ tenocytes in association with tendinosis and correlated with increased local IGF-1 expression by tenocytes and phosphorylation of IRS-1 and ERK-1/2. Both apoptosis and cellular inflammation were absent at all time points.

CONCLUSION

In this animal model, early tendinosis was associated with local stimulation of tenocytes rather than with extrinsic inflammation or apoptosis. Our data suggest a role for IGF-1 in the load-induced tenocyte responses during the pathogenesis of overuse tendon disorders.

Achilles tendon rupture following surgical management for tendinopathy: a case report

Background

Achilles tendinopathy is understood to be a failed healing response. Operative management is utilised following the failure of non-operative methods.

Case Presentation

We present a case of Achilles tendon rupture, sustained whilst isometrically loading the Achilles tendon during an eccentric loading exercise programme. Conclusion: Bilateral surgical exploration and debridement had previously been performed after conservative management of bilateral Achilles tendinopathy had been unsuccessful.

Effects of short-term treatment strategies over 4 weeks in Achilles tendinopathy

BACKGROUND

The therapeutic efficacy of non-surgical treatment strategies in Achilles tendinopathy (AT) has not been well clarified. Time-consuming and costly combinations of treatment for pain, physiotherapy and biomechanical procedures are often applied.

OBJECTIVE

To analyse the efficacy of single therapeutic regimens commonly used over a short period of 4 weeks.

METHODS

31 male runners (mileage >32 km/week) with unilateral, untreated AT completed 4 weeks of either physiotherapy (10 treatments: deep-friction, pulsed ultrasound, ice, sensory motor training; (P)), wearing custom fit semirigid insoles (I) or remained without treatment (control group C). Before and after treatment, all patients underwent a treadmill test and a plantar flexion strength exercise. Subjective pain (Pain Disability Index, Pain Experience Scale), as well as strength performance capacity (peak torque), was analysed (mean, 95% CI, repeated measures analysis of variance, alpha = 0.05).

RESULTS

Pain was reduced to <50% of the baseline value after physiotherapy or after wearing insoles (p<0.05). Individual pain reduction was >50% (25%) in 89% (100%) of subjects in I and 55% (73%) in P. Higher eccentric plantar flexion peak torques after treatment were observed in I and P.

CONCLUSIONS

Most patients with AT experience a reduction in pain after only 4 weeks of differentiated, non-surgical treatment consisting of physiotherapy or semirigid insoles.

An isokinetic eccentric programme for the management of chronic lateral epicondylar tendinopathy

BACKGROUND

Lateral epicondylitis represents a frequent overuse injury. In spite of many conservative treatment procedures, prolonged symptoms and relapse are frequently observed.

OBJECTIVE

To compare the outcome of patients performing an isokinetic eccentric training with that of age-, gender-, activity-matched patients receiving a non-strengthening classical rehabilitation.

METHODS

Ninety-two patients with unilateral chronic lateral epicondylar tendinopathy (mean duration of symptoms 8+/-3 months) were assigned either to a control group (n = 46) or to an eccentrically trained group (n = 46). The control group underwent a passive standardised rehabilitation programme that excluded strengthening exercises. In addition to this programme, the trained group also performed eccentric exercises based on the repetitive lengthening of the active musculo-tendinous unit. The latter exercises started with submaximal contraction intensity and slow speed movement. Modalities were progressively intensified (increase in intensity contraction and speed movement) over a long period of treatment. Programme effectiveness was assessed through pain score evaluation, a disability questionnaire, muscle strength measurement and ultrasonographic examination.

RESULTS

Compared to the non-strengthening control group, the following observations were made in the eccentrically trained group: (1) a significantly more marked reduction of pain intensity, mainly after one month of treatment; (2) an absence of strength deficit on the involved side through bilateral comparison for the forearm supinator and wrist extensor muscles; (3) an improvement of the tendon image as demonstrated by decreasing thickness and a recovered homogenous tendon structure; and (4) a more marked improvement in disability status during occupational, spare time and sports activities.

CONCLUSION

These results highlight the relevance of implementing isokinetic adapted eccentric training in the management of chronic lateral epicondylar tendinopathy.

In vitro study comparing two collageneous membranes in view of their clinical application for rotator cuff tendon regeneration

Tenocytes were isolated from the rotator cuff tendons of healthy (HT) and glucocorticoid (GC)-treated rats (GCT) and were cultured on polystyrene wells (TCP) as control, and on 2 de-cellularized collagen matrices: porcine small intestinal submucosa (SIS), and human dermal matrix (Graftjacket, GJ). At 3 and 7 days cell proliferation and synthesis were evaluated. Proliferation of HT tenocytes increased between experimental times for both tested membranes, but already at 3 days, HT tenocytes cultured on GJ showed the highest WST-1 value. The collagen-I (CICP) synthesis on GJ membrane did not change between experimental times and was significantly higher than TCP and SIS at 7 days. Proteoglycans (PG), and fibronectin (FBN) synthesis increased when HT were cultured on GJ, between experimental times, and both PG and FBN synthesis on GJ membrane were higher than TCP and SIS at 7 days. GC determined decreases in cell proliferation, CICP and PG syntheses at 3 days of culture on TCP when compared to HT tenocytes while a decrease in WST-1 was maintained at 7 days. CICP, PG and FBN (only at 3 days) syntheses were significantly higher in GCT tenocytes cultured on GJ. The negative effects on GC on GCT tenocytes cultured on membrane were particularly evident on SIS for CICP (-18%) and FBN (-67%) synthesis. The obtained results support the conclusion that GJ is more suitable than SIS as a scaffold for in situ tissue engineering and for the in vitro bioengineering of tendons to heal massive tears of the rotator cuff tendon.

Serum-dependent effects on adult and fetal tendon fibroblast migration and collagen expression

Cell migration and extracellular matrix synthesis play an important role in the wound-healing response to injury. Several studies have described differences in migratory behavior and collagen biosynthetic activity in adult vs. fetal skin fibroblasts. The objective of this study was to examine the serum- and age-dependent effects on cell migration and collagen expression in tendon fibroblasts. Medial tendon fibroblasts were isolated from pregnant ewes and their fetuses, and cultured with and without serum for up to 7 days. Cell migration was determined by quantitative image analysis, and collagen expression was assessed by reverse transcription-polymerase chain reaction and immunohistochemical staining. In serum-containing medium, tendon fibroblasts migrated significantly faster than cells in serum-free medium. Additionally, fetal tendon fibroblasts migrated significantly faster than adult tendon fibroblasts under both culture conditions. The expression of types I and III collagen mRNA was significantly up-regulated in tendon cell populations in serum-free medium compared with those in serum-containing medium. Quantitative assessment of collagen staining indicated that fetal tenocytes produced more type I collagen than adult tenocytes under both culture conditions. These findings suggest that there is an inherent difference between adult and fetal tendon fibroblasts, which may have implications in the wound-healing response in tendons.

Small molecule inducers of angiogenesis for tissue engineering

Engineering of implantable tissues requires rapid induction of angiogenesis to meet the significant oxygen and nutrient demands of cells during tissue repair. To this end, our laboratories have utilized medicinal chemistry to synthesize non-peptide-based inducers of angiogenesis to aid tissue engineering. In this study, we describe the evaluation of SC-3-149, a small molecule compound with proliferative effects on vascular endothelial cells. Specifically, exogenous exposure of SC-3-149 induced an 18-fold increase in proliferation of human microvascular endothelial cells in vitro at low micromolar potency by day 14 in culture. Moreover, SC-3-149 significantly increased the formation of endothelial cord and tubelike structures in vitro, and improved endothelial scratch wound healing within 24 h. SC-3-149 also significantly inhibited vascular endothelial cell death owing to serum deprivation and high acidity (pH 6). Concurrent incubation of SC-3-149 with vascular endothelial growth factor increased cell survivability under serum-deprived conditions by an additional 7%. In addition, in vivo injection of SC-3-149 into the rat mesentery produced qualitative increases in microvessel length density. Taken together, our studies suggest that SC-3-149 and its analogs may serve as promising new angiogenic agents for targeted drug delivery and therapeutic angiogenesis in tissue engineering.

Chondral metaplasia in calcific insertional tendinopathy of the Achilles tendon

OBJECTIVE

To ascertain whether tendon samples harvested from patients with calcific insertional Achilles tendinopathy showed features of failed healing response, and whether abnormal quantities of type II collagen had been produced in that area by these tenocytes.

DESIGN

Comparative laboratory study.

DESIGN

University teaching hospitals.

PATIENTS

Tendon samples were harvested from eight otherwise healthy male individuals (average age 47.5+/-8.4 years, range 38 to 60) who were operated for calcific insertional Achilles tendinopathy and from nine male patients who died of cardiovascular events (mean age 63.1+/-10.9 years) while in hospital.

INTERVENTIONS

Open surgery for calcific insertional Achilles tendinopathy.

MAIN OUTCOME MEASURE

Semi-quantitative histochemical, immunohistochemical, and immunocytochemical methods to ascertain whether tendinopathic tendons were morphologically different from control tendons, and whether abnormal types of collagen were produced.

RESULTS

Tenocytes from tendons from patients with calcific insertional Achilles tendinopathy exhibit chondral metaplasia, and produce abnormally high quantities of collagen type II and III.

CONCLUSIONS

The altered production of collagen may be one reason for the histopathological alterations described in the present study. Areas of calcific insertional Achilles tendinopathy have been subjected to abnormal loads. These tendons may be less resistant to tensile forces. Further studies should investigate why some tendons undergo these changes.

RGD-tethered silk substrate stimulates the differentiation of human tendon cells

Tendon reconstruction surgery often requires healing of the tendon to bone. The development of a more rapid and strong interaction at the tendon to bone interface would be invaluable to patients having orthopaedic surgery. Therefore, our rationale was to modify sutures so that they would be anabolic for tendon to bone healing. It has been shown that silk stimulates bone formation in osteoblast cultures. In the current study, we tested the ability of silk and silk-RGD (arginine-glycine-aspartic acid) to stimulate human tenocyte adhesion, proliferation, and differentiation. A 1.3-fold increase in tenocyte adhesion was found on silk-RGD compared with tissue culture plastic. By 72 hours, proliferation had increased on all substrates but was particularly enhanced on silk-RGD compared with the control. At 6 weeks, Northern blot analysis of decorin and Type I collagen mRNA levels showed a 2-3-fold increase in message levels on silk-RGD and silk compared with tissue culture plastic. The data suggest cultured human tenocytes adhere, proliferate, and differentiate on silk and silk-RGD substrates. A suture material, such as silk, decorated with RGD, may have the potential to facilitate tendon-bone healing with widespread applications in tendon reconstruction surgery.

Phenotypic Drift in Human Tenocyte Culture

Tendon ruptures are increasingly common, repair can be difficult, and healing is poorly understood. Tissue engineering approaches often require expansion of cell numbers to populate a construct, and maintenance of cell phenotype is essential for tissue regeneration. Here, we characterize the phenotype of human Achilles tenocytes and assess how this is affected by passaging. Tenocytes, isolated from tendon samples from 6 patients receiving surgery for rupture of the Achilles tendon, were passaged 8 times. Proliferation rates and cell morphology were recorded at passages 1, 4, and 8. Total collagen, the ratio of collagen types I and III, and decorin were used as indicators of matrix formation, and expression of the integrin beta1 subunit as a marker of cell-matrix interactions. With increasing passage number, cells became more rounded, were more widely spaced at confluence, and confluent cell density declined from 18,700/cm2 to 16,100/cm2 ( p = 0.009). No change to total cell layer collagen was observed but the ratio of type III to type I collagen increased from 0.60 at passage 1 to 0.89 at passage 8 ( p < 0.001). Decorin expression significantly decreased with passage number, from 22.9 +/- 3.1 ng/ng of DNA at passage 1, to 9.1 +/- 1.8 ng/ng of DNA at passage 8 ( p < 0.001). Integrin expression did not change. We conclude that the phenotype of tenocytes in culture rapidly drifts with progressive passage.

The effect of corticosteroid on collagen expression in injured rotator cuff tendon

BACKGROUND

Subacromial corticosteroid injections are commonly used in the nonoperative management of rotator cuff disease. The effects of corticosteroid injection on injured rotator cuff tendons have not been studied. Our aims were to characterize the acute response of rotator cuff tendons to injury through the analysis of the type-III to type-I collagen expression ratio, a tendon injury marker, and to examine the effects of corticosteroid on this response.

METHODS

Sixty Sprague-Dawley rats were randomly assigned to four groups: control, tendon injury, steroid treatment, and tendon injury and steroid treatment. Six rats served as sham controls. Unilateral tendon injuries were created with full-thickness defects across 50% of the total width of the infraspinatus tendon, 5 mm from its humeral insertion. Steroid treatment with a single dose of methylprednisolone (0.6 mg/kg), equivalent to that given to humans, was injected into the subacromial space under direct visualization. Steroid treatment followed the creation of an injury in the rats in the injury and steroid treatment group. At one, three, and five weeks after the injury, the total RNA isolated from tendons was quantified with real-time polymerase chain reaction with use of primers for type-I and type-III collagen and ribosomal 18s RNA.

RESULTS

The type-III to type-I collagen expression ratio remained at baseline at all time-points in the control and sham groups. At one week, the type-III to type-I collagen expression ratio increased more than fourfold above the control level in the tendon injury group (p = 0.017) and the tendon injury and steroid treatment group (p = 0.003). The ratio remained greater than twofold above the control at three weeks in both groups (p = 0.003 and p = 0.037) and returned to baseline at five weeks. Interestingly, the group that had steroid treatment only showed an increase of >4.5-fold (p = 0.001) in the type-III to type-I collagen expression ratio, without structural injury to the tendon. This ratio returned to baseline levels by three weeks.

CONCLUSIONS

A single dose of corticosteroid does not alter the acute phase response of an injured rotator cuff tendon in the rat. However, the same steroid dose in uninjured tendons initiates a short-term response equivalent to that of structural injury.

Ultrasound stimulation of types I and III collagen expression of tendon cell and upregulation of transforming growth factor beta

Traumatic tendon injuries are commonly treated with ultrasound. However, previous research has not examined the molecular mechanism of this therapeutic effect on collagen synthesis of tendon cells. This study was designed to determine the effect of ultrasound on the expression of type I and type III collagen of tendon cells intrinsic to rat Achilles tendon. Whether a correlation exits between this effect and the expression of transforming growth factor beta (TGF-beta), which enhances collagen synthesis, was also investigated. Tendon cells after ultrasound treatment and protein expression of types I and III collagen were determined by immunocytochemistry. The mRNA expressions of alpha1(I) procollagen, alpha1(III) procollagen, and TGF-beta were determined by reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the concentration of TGF-beta in conditioned medium was evaluated by enzyme-linked immunosorbent assay (ELISA). Immunocytochemical staining revealed that ultrasound-treated tendon cells were stained more strongly for types I and III collagen than were control cells. Upregulation of procollagen alpha1(I) gene, procollagen alpha1(III) gene, and TGF-beta at the mRNA level was confirmed by RT-PCR. A dose-dependent increase in the concentration of TGF-beta in conditioned medium obtained from cells treated with ultrasound was demonstrated by ELISA assay (p = 0.043). In conclusion, ultrasound stimulates the expression of type I and type III collagen in a process that is likely mediated by the upregulation of TGF-beta.

Achilles detachment in rat and stable gastric pentadecapeptide BPC 157: Promoted tendon-to-bone healing and opposed corticosteroid aggravation

Stable gastric pentadecapeptide BPC 157 (BPC 157, as an antiulcer agent in clinical trials for inflammatory bowel disease; PLD-116, PL 14736, Pliva, no toxicity reported) alone (without carrier) ameliorates healing of tendon and bone, respectively, as well as other tissues. Thereby, we focus on Achilles tendon-to-bone healing: tendon to bone could not be healed spontaneously, but it was recovered by this peptide. After the rat's Achilles tendon was sharply transected from calcaneal bone, agents [BPC 157 (10 microg, 10 ng, 10 pg), 6alpha-methylprednisolone (1 mg), 0.9% NaCl (5 mL)] were given alone or in combination [/kg body weight (b.w.) intraperitoneally, once time daily, first 30-min after surgery, last 24 h before analysis]. Tested at days 1, 4, 7, 10, 14, and 21 after Achilles detachment, BPC 157 improves healing functionally [Achilles functional index (AFI) values substantially increased], biomechanically (load to failure, stiffness, and Young elasticity modulus significantly increased), macro/microscopically, immunohistochemistry (better organization of collagen fibers, and advanced vascular appearance, more collagen type I). 6alpha-Methylprednisolone consistently aggravates the healing, while BPC 157 substantially reduces 6alpha-methylprednisolone healing aggravation. Thus, direct tendon-to-bone healing using stabile nontoxic peptide BPC 157 without a carrier might successfully exchange the present reconstructive surgical methods.

Acute rupture of the Achilles tendon

Achilles tendon ruptures are common, and their incidence is increasing. The evidence for best management is controversial, and, in selected patients, conservative management and early mobilization achieves excellent results. Surgery is associated with an increased risk of superficial skin breakdown; however, modern techniques of percutaneous repair that are performed under local anesthesia and followed by early functional rehabilitation are becoming increasingly common, and should be considered when managing such patients.

Molecular events in tendinopathy: a role for metalloproteases

Disorganized, haphazard ineffective healing is a constant feature of chronic tendinopathy. Normal tendon is composed mostly of type I collagen. Tendinopathic tendons, conversely, have a greater proportion of type III collagen, which is associated with tendon rupture. Matrix metalloproteinases (MMPs) are involved in remodelling of the extracellular matrix (ECM) of tendons, because they are either up- or down-regulated in tendinopathy. A balance between MMPs and tissue inhibitors of metalloproteinases is required to maintain tendon homeostasis. The mechanism of activation of MMPs is poorly understood, and their precise role in tendinopathy is unclear.

Mechanism of cell death in inflamed superficial digital flexor tendon in the horse

The aim of the present study was to clarify the presence and determine the role of apoptosis in the degenerative process of the superficial digital flexor tendon (SDFT) in the horse. Samples were obtained from normal and inflamed SDFTs of horses. To detect apoptosis and to identify apoptotic cells, the samples were subjected to immunohistochemical labelling and Western blot analysis. Although a large number of cells in degenerate areas showed positive reactions with caspase-3 and single stranded DNA antibodies, cells in normal tendon samples showed very weak reactions. Excessive apoptosis was confirmed by the results of Western blot analysis, which showed a significant increase in activated caspase-3 protein in the inflamed SDFTs, suggesting that apoptosis occurred in the tendinocytes via a caspase-3-dependent pathway. This is the first report of excessive apoptosis in inflamed SDFT of the horse. The results indicate that apoptosis may play an important role in the process of degeneration of the tendon as well as other tissues.