Enforced bipedal downhill running induces Achilles tendinosis in rats

Enforced downhill running has been reported to induce tendinosis in the rat supraspinatus tendon but similar exercise failed to induce Achilles tendinosis in this animal. Due to the presence of acromial arch in the shoulder, accessing the supraspinatus tendon with physical modalities is difficult; thus this model may not be suitable for studying the treatment for tendinosis. To develop a rat model for Achilles tendinosis, we tested 14 mature Sprague-Dawley rats by dividing them into 2 groups of 7 each. The experimental group was subjected to a daily enforced downhill bipedal running program by suspending their upper bodies so that they ran with their hind limbs on a treadmill for 1 hr/day for 8 weeks. The downward inclination was 20 degrees and the speed was 17 m/min. The animals in the control group did not undergo any exercise. After 8 weeks, the Achilles tendons were harvested and subjected to histological and biomechanical analysis. Histological examination revealed tenocyte proliferation, change in tenocytes appearance, and collagen bundle disintegration in the running group. The biomechanical testing revealed significant decrease in stiffness (p = 0.002) and ultimate tensile strength (p = 0.016) in the running group than in the control group. Both the histological and biomechanical findings are suggestive of changes in the tendon of the running group that resembled the pathological changes of tendinosis in human. This new model of Achilles tendinosis in rat will be useful for studying the etiology and subsequent management strategies of this condition.     

Uphill running does not exacerbate collagenase-induced pathological changes in the Achilles tendon of rats selectively bred for high-capacity running

Abstract

The Achilles tendon is a frequent site for degeneration, and advanced understanding of this pathology requires an animal model that replicates the human condition. The aim of this study was to explore whether intratendinous collagenase injection combined with treadmill running created a pathology in the rat Achilles tendon consistent with human Achilles tendinosis. Collagenase was injected into one Achilles tendon of 88 high-capacity running (HCR) rats, which were randomized into treadmill running and cage control groups. Running animals ran at speeds up to 30?m/min on a treadmill at a 15° incline for up to 1?h/d, 5?d/week for 4 or 10 weeks. Cage control animals maintained cage activity. Collagenase induced molecular, histopathological and mechanical changes within the Achilles tendon at 4 weeks. The mechanical changes persisted at 10 weeks; however, the histopathological and majority of the molecular changes were no longer present at 10 weeks. Treadmill running had minimal effect and did not exacerbate the collagenase-induced changes as there were no statistical interactions between the interventions. These data suggest combined intratendinous collagenase injection and treadmill running does not create pathology within the Achilles tendon of rats selectively bred for HCR that is consistent with human Achilles tendinosis.     

The Effect of Overuse Activity on Achilles Tendon in an Animal Model: A Biomechanical Study

Musculoskeletal soft tissue injuries from athletic activities are common in the rotator cuff tendons, lateral epicondyle of the elbow, the patella tendon, and the Achilles tendon. Despite the fact that the Achilles tendon is the largest and strongest tendon in the human body, it is frequently injured in the athletic setting. To study the etiology and pathogenesis of Achilles tendon injuries, our goal was to develop a model of Achilles tendon overuse by evaluating the Achilles tendons from animals subjected to the exercise protocol previously described as overuse for the supraspinatus tendon. We hypothesized that the same exercise protocol would produce injuries to the Achilles tendon as demonstrated by changes in the cross-sectional area and biomechanical properties. While a significant injury was induced into the supraspinatus tendon, we found no changes in the Achilles tendons of these exercised animals based on gross observation, geometric measurements, and mechanical testing analyses. Although surprising, there are many possible explanations for these findings including differences in potential injury mechanisms, functional capabilities of the differing tendons, and other factors.     

The effect of dry needling and treadmill running on inducing pathological changes in rat Achilles tendon

Achilles tendinopathy is a common degenerative condition without a definitive treatment. An adequate chronic animal model of Achilles tendinopathy has not yet been developed. The purpose of this study was to evaluate the individual and combined effects of dry needling and treadmill running on the Achilles tendon of rats. Percutaneous dry needling, designed to physically replicate microrupture of collagen fibers in overloaded tendons, was performed on the right Achilles tendon of 80 Sprague–Dawley rats. The rats were randomly divided into two groups: a treadmill group, which included rats that underwent daily uphill treadmill running (n?=?40), and a cage group, which included rats that could move freely within their cages (n?=?40). At the end of weeks 1 and 4, 20 rats from each group were sacrificed, and bilateral Achilles tendons were collected. The harvested tendons were subjected to mechanical testing and histological analysis. Dry needling induced histological and mechanical changes in the Achilles tendons at week 1, and the changes persisted at week 4. The needled Achilles tendons of the treadmill group tended to show more severe histological and mechanical changes than those of the cage group, although these differences were not statistically significant. Dry needling combined with free cage activity or treadmill running produced tendinopathy-like changes in rat Achilles tendons up to 4 weeks after injury. Dry needling is an easy procedure with a short induction period and a high success rate, suggesting it may have relevance in the design of an Achilles tendinopathy model.     

A novel biodegradable PCL film for tendon reconstruction: Achilles tendon defect model in rats

This study aims to investigate applicability of poly(epsilon-caprolactone) (PCL) biodegradable films for repair of gaps in Achilles tendons in a rat model, also comparing surgical repair versus no repair approaches. PCL was synthesized with tailor-made properties, then, PCL films were prepared by solvent casting. Seventy-five outbred Sprague-Dawley rats were randomly allocated into five groups: (i) sham operated (skin incision only); (ii) no repair (complete division of the Achilles tendon and plantaris tendon without repair); (iii) Achilles repair (with a modified Kessler type suture); and (iv) plasty of Achilles tendon defects with the biodegradable PCL films, and (v) animals subjected to 1 cm mid-substance defect with no repair. Functional performance was determined from the measurements of hindpaw prints utilizing the Achilles functional index. The animals were killed 8 weeks after surgery and histological and biomechanical evaluations were made. All groups subjected to Achilles tendon division had a significant functional impairment that gradually improved so that by day 28 there were no functional impairments in any group whereas animals with a defect remained impaired. The magnitude of the biomechanical and morphological changes at postoperative 8 weeks were similar for no repair group (conservative), Achilles repair group and tendonplasty group (biodegradable PCL film group). The initial rate of functional recovery was significantly different for primary suture, Achilles repair group and PCL film group (p>0.01). But, at the 28th day, functional recovery was quite similar to the other groups. In summary, our results suggest that the PCL film can be an alternative biomaterial for tendon replacement.     

Effect of taurine on rat Achilles tendon healing

Taurine has anti-inflammatory and antioxidant characteristics. We have introduced taurine into a tendon-healing model to evaluate its effects on tendon healing and adhesion formation. Two groups of 16 rats underwent diversion and repair of the Achilles tendon. One group received a taurine injection (200?mg/ml) at the repair site, while the other group received 1?ml of saline. Specimens were harvested at 6 weeks and underwent biomechanical and histological evaluation. No tendon ruptured. Average maximum load was significantly greater in the taurine-applied group compared with the control group (p?p?p?>?0.05). After histological assessment, we found that fibroblast proliferation, edema, and inflammation statistically decreased in the treatment group (p?相似文献   

Rotator cuff tendinosis in an animal model: role of extrinsic and overuse factors

The rat shoulder animal model has been used previously to study the role of intrinsic injury (modeled as an acute insult to the tendon), extrinsic injury (modeled as external subacromial impingement), and overuse factors on rotator cuff tendinosis. These studies demonstrated that it is possible to produce rotator cuff tendinosis with any one of these factors in isolation. The current study uses the rat shoulder model to study the roles of extrinsic compression, overuse, and overuse in combination with extrinsic compression, on the development of rotator cuff tendinosis. The results of this study demonstrate that the injury created by overuse plus extrinsic compression is greater than the injuries created by overuse or extrinsic compression alone, particularly when important biomechanical variables are considered. While ineffective in causing a change in supraspinatus tendon properties in animals with normal cage activity, extrinsic compression had a significant and dramatic effect when it was combined with overuse activity. Without an additional factor, such as overhead activity, the extrinsic compression alone may be insufficient to cause tendinosis. The results of the present study support the role of multiple factors in the etiology of some rotator cuff injuries. © 2002 Biomedical Engineering Society. PAC2002: 8719Rr, 8719St     

Mechanical properties of achilles tendon in rats induced to experimental diabetes

The aim of this study was to quantify the effect of chemically induced diabetes mellitus (DM) on the mechanical properties of the Achilles tendon of rats and correlate it with metabolic and biomechanical findings. Adult rats were selected randomly and assigned to two groups, the diabetic group consisted of animals receiving a dose of streptozotocin to induce type I diabetes and the control group. The animals were placed in metabolic cages for analysis of metabolism. Ten weeks after diabetes induction, the Achilles tendon of both groups were collected and submitted to a traction test in a conventional testing machine. The measurements of mechanical properties indicated that the elastic modulus (MPa) was significantly higher in the control group (p < 0.01). In Maximum tension (MPa), the groups did not have differences (p > 0.01). Energy/tendon area (N mm/mm²), specific strain (%) and maximum specific strain (mm) were higher in tendon tests of the diabetic group (p < 0.01). We observed that the mechanical properties of tendons have correlations with metabolic properties of the diabetic animals. These results showed that induced DM in rats have an important negative effect on the mechanical properties of the Achilles tendon.     

耐力运动大鼠跟腱胶原、基质金属蛋白酶1及其抑制剂1的表达

背景：胶原是肌腱细胞外基质中的主要成分,基质金属蛋白酶是降解肌腱细胞外基质蛋白的重要蛋白酶。 目的：观察12周跑台运动对大鼠跟腱胶原、胶原Ⅰ、基质金属蛋白酶1及其抑制剂1表达的影响。 方法：将20只雄性SD大鼠随机分为对照组和运动组。第1周每天运动20 min,速度由12 m/min递增至20 m/min;以后跑台速度均为20 m/min,第2周坡度为5%,时间为30 min,第3~12周坡度为10%,时间为40 min,共运动12周。对照组正常饲养。 结果与结论：末次运动后24 h取大鼠跟腱。与对照组比较,运动组大鼠跟腱前胶原Ⅰα1、基质金属蛋白酶1及其抑制剂1 mRNA的表达明显升高(P < 0.05或P < 0.01),羟脯氨酸的含量也有所增多,但与对照组比较差异无显著性意义(P > 0.05)。表明长期耐力运动可以提高跟腱中胶原的合成和降解能力。     

Histopathological and biomechanical evaluation of tenocyte seeded allografts on rat Achilles tendon regeneration

Tendon injuries in humans as well as in animals' veterinary medicine are problematic because tendon has poor regenerative capacity and complete regeneration of the ruptured tendon is never achieved. In the last decade there has been an increasing need of treatment methods with different approaches. The aim of the current study was to improve the regeneration process of rat Achilles tendon with tenocyte seeded decellularized tendon matrices. For this purpose, Achilles tendons were harvested, decellularized and seeded as a mixture of three consecutive passages of tenocytes at a density of 1 × 10⁶ cells/ml. Specifically, cells with different passage numbers were compared with respect to growth characteristics, cellular senescence and collagen/tenocyte marker production before seeding process. The viability of reseeded tendon constructs was followed postoperatively up to 6 months in rat Achilles tendon by histopathological and biomechanical analysis. Our results suggests that tenocyte seeded decellularized tendon matrix can significantly improve the histological and biomechanical properties of tendon repair tissue without causing adverse immune reactions. To the best of our knowledge, this is the first long-term study in the literature which was accomplished to prove the use of decellularized matrix in a clinically relevant model of rat Achilles tendon and the method suggested herein might have important implications for translation into the clinic.     

Knitted poly-lactide-co-glycolide scaffold loaded with bone marrow stromal cells in repair and regeneration of rabbit Achilles tendon

The objectives of this study were to evaluate the morphology and biomechanical function of Achilles tendons regenerated using knitted poly-lactide-co-glycolide (PLGA) loaded with bone marrow stromal cells (bMSCs). The animal model used was that of an adult female New Zealand White rabbit with a 10-mm gap defect of the Achilles tendon. In group I, 19 hind legs with the created defects were treated with allogeneic bMSCs seeded on knitted PLGA scaffold. In group II, the Achilles tendon defects in 19 hind legs were repaired using the knitted PLGA scaffold alone, and in group III, 6 hind legs were used as normal control. The tendon-implant constructs of groups I and II were evaluated postoperatively at 2, 4, 8, and 12 weeks using macroscopic, histological, and immunohistochemical techniques. In addition, specimens from group I (n = 7), group II (n = 7), and group III (n = 6) were harvested for biomechanical test 12 weeks after surgery. Postoperatively, at 2 and 4 weeks, the histology of group I specimens exhibited a higher rate of tissue formation and remodeling as compared with group II, whereas at 8 and 12 weeks postoperation, the histology of both group I and group II was similar to that of native tendon tissue. The wound sites of group I healed well and there was no apparent lymphocyte infiltration. Immunohistochemical analysis showed that the regenerated tendons were composed of collagen types I and type III fibers. The tensile stiffness and modulus of group I were 87 and 62.6% of normal tendon, respectively, whereas those of group II were about 56.4 and 52.9% of normal tendon, respectively. These results suggest that the knitted PLGA biodegradable scaffold loaded with allogeneic bone marrow stromal cells has the potential to regenerate and repair gap defect of Achilles tendon and to effectively restore structure and function.     

上、下坡跑台训练膝骨关节炎模型大鼠关节软骨及炎症因子的变化

BACKGROUND: Different training methods have different effects on primary knee osteoarthritis. OBJECTIVE: To compare the effects of uphill or downhill running on articular cartilage degeneration and inflammatory responses of knee osteoarthritis rats.   METHODS: 108 female Sprague-Dawley rats were randomly divided into six groups: normal control group, ovariectomized group, uphill running group (run & up), downhill running group (run & down), uphill running model group (model & up), downhill running model group (model & down). The rats in the normal control group were raised routinely with no treatment; rats in the ovariectomized group were ovarientomized and raised in routine way; rats in the run & up group and run & down group were subjected to uphill running training on the slop +15° or downhill running training on the slop -15°; rats in the model & up group and model & down group were subjected to uphill running training on the slop +15°or downhill running training on the slop -15° after ovarientomized. Training programs were as follows: 28 m/min, 60 minutes per day, 6 days per week. RESULTS AND CONCLUSION: Compared with the other five groups, in the model & up group, the Mankin’s score was significantly increased, indicating that articular cartilage degeneration occurred, and the peak of carboxy-terminal telopeptide of type II collagen contained in the urine had passed, at 4 weeks after modeling. At 6 weeks, the Mankin’s score of the model & down group was increased to reach the degeneration standard, but it was still lower than that of the model & up group; the expression levels of tumor necrosis factor-α and interleukin-1β in the synovial fluid were significantly higher in the model & up and model & down groups than the other four groups. At 8 weeks, the Mankin’s score and the expression levels of tumor necrosis factor-α and interleukin-1β were further increased in the model & up and model & down groups, especially in the model & up group. These results indicate that treadmill running exercise after ovariectomized can result in articular cartilage injury and local inflammatory responses; compared with the downhill running training, the uphill running training can cause cartilage injury earlier and more efficiently.      

Adenovirus-mediated gene transfer of growth and differentiation factor-5 into tenocytes and the healing rat Achilles tendon

Growth and differentiation factor-5 (GDF-5) is known to induce tendon tissue and stimulate tendon healing. The hypothesis was that adenoviral GDF-5 transfer leads to transitory transgene expression and improves Achilles tendon healing. In vitro experiments were first performed with rat tenocytes. Transgene expression was evaluated by RT-PCR, Western blotting and GDF-5-ELISA. In vivo virus dosage and transgene expression were examined by a marker gene transfer (LacZ and luciferase). In the main experiment in 131 rats, adenovirus particles (3 x 10(10)) were injected into transected Achilles tendons. The time course of GDF-5 mRNA expression was assessed by real-time RT-PCR. Histology and biomechanical testing were used to evaluate tendon healing and tensile strength. In vitro GDF-5 was secreted with a maximum after 2 weeks (330 ng GDF-5/10(6) cells per 24 hr). In vivo GDF-5 transgene expression showed a maximum at 4 weeks. At 8 weeks, GDF-5 specimens were thicker (p<0.05) with a trend to higher strength (p=0,064). Histology showed greater cartilage formation in type II collagen stains than in controls. Injection of adenovirus particles successfully can deliver the GDF-5 gene in healing tendons and leads to thicker tendon regenerates after 8 weeks. This technique might become a new approach for nonsurgical treatment of tendon injuries.     

A Novel Application of Biosynthetic Tissue-Engineered Tridimensional Implant on Large Tendon Defects: A Comprehensive,Detailed, In Vivo Investigation with Significant Clinical Value

This study was designed to investigate the effect of a biosynthetic implant on tendon healing in vivo. Fifty white New Zealand male rabbits were randomly divided into two groups, namely treated (n = 25) and control (n = 25) groups. A large gap was created in the Achilles tendon and was maintained by Kessler pattern. In the treated group, the implant was inserted in the injured area. No implant was used in the control group. Contrast radiography, hematology, and clinical examination were conducted during the course of the experiment. The animals were euthanized at 60 days post injury (DPI) and their Achilles tendons were subjected to the gross, histopathologic, and biomechanical analyses and the hydroxyproline content of these tendons was also evaluated. Another five treated animals, as a pilot group, were used to define the inflammatory reaction at 10 DPI. Severe inflammatory reaction was initiated by the partially degraded implant, at 10 DPI. However, at 60 DPI, the inflammation subsided, the implant was mostly removed but a few small remnants were still present in the injured area. The newly formed tendon, properly aligned along the longitudinal axis of the Achilles tendon replaced the collagen implant. In the control tendons, a loose areolar connective tissue which tightly adhered to the peri-tendinous tissue was the only regenerated structure in the injured area. At this stage, the treated tendons showed significantly higher ultimate strength (p = 0.001), yield strength (p = 0.001), and stiffness (p = 0.001) compared with the control ones. Application of the biosynthetic implant was a safe and effective option in managing the large tendon defects and could be considered as a substitute for autografts in clinical practice.     

带血管蒂肌腱移植修复跟腱缺损的实验研究

目的为带血供肌腱移植修复跟腱缺损提供生物力学和组织学依据.方法选用新西兰大白兔15只,其中12只分两组一侧行带血管蒂趾长屈肌腱转位修复跟腱缺损,对侧为游离肌腱移植对照组,术后12周取材,分别行组织学检查和生物力学测试.结果带血管蒂肌腱组移植跟腱组织学形态近似正常跟腱,肌腱最大拉伸力为正常跟腱的67.7%,而游离肌腱组移植跟腱的腱纤维为瘢痕包裹,最大拉伸力为跟腱的35.3%,两者的差异性非常显著(P＜0.01).结论带血管蒂肌腱移植修复跟腱缺损优于游离肌腱移植.     

Evidence of the TNF-α System in the Human Achilles Tendon: Expression of TNF-α and TNF Receptor at both Protein and mRNA Levels in the Tenocytes

Understanding adaption to load is essential for prevention and treatment of tendinopathy/tendinosis. Cytokine release in response to load is one mechanism involved in mechanotransduction. The cytokine tumor necrosis factor alpha (TNF-α) is implicated in tendinosis and can induce apoptotic effects via tumor necrosis factor receptor 1 (TNFR1). The complete absence of information concerning the TNF-α system in Achilles tendon is a limitation as mid-portion Achilles tendinosis is very frequent. Purpose: To examine expression patterns of TNF-α and its two receptors (TNFR1 and TNFR2) in human Achilles tendinosis and control tissue and to biochemically confirm the presence of TNF-α in tendinosis tissue. Methods: TNF-α and TNFR1 mRNA were detected via in situ hybridization. TNF-α, TNFR1, and TNFR2 were demonstrated immunohistochemically. Apoptosis markers were utilized. ELISA was used to detect TNF-α. Results: TNF-α and TNFR1 mRNA was detected in tenocytes of both tendinosis and control tendons. Tenocytes from both groups displayed specific immunoreactions for TNF-α, TNFR1, and TNFR2. The widened/rounded tenocytes of tendinosis samples exhibited the most intense immunoreactions. Apoptosis was detected in only a subpopulation of the tenocytes in tendinosis tissue. TNF-α was measurable in tendinosis tissue. Inflammatory cells were not seen. Conclusion: This is the first evidence of the existence of the TNF-α system in the human Achilles tendon. Findings are confirmed at mRNA and protein levels as well as biochemically. The TNF-α system was in principle confined to the tenocytes. The connection between tenocyte morphology and the expression pattern of TNF-α, TNFR1, and TNFR2 suggests that the TNF-α system may be involved in tenocyte activation in Achilles tendinosis.     

肿瘤坏死因子α拮抗剂对应力屏蔽导致的跟腱挛缩形态学影响

背景：跟腱应力屏蔽后肿瘤坏死因子α明显升高,应用肿瘤坏死因子α拮抗剂干预肿瘤坏死因子α的作用是否会干预跟腱挛缩尚不清楚。 目的：通过观察重组人Ⅱ型肿瘤坏死因子受体-抗体融合蛋白(益赛普)干预应力屏蔽后大鼠跟腱形态学变化,了解肿瘤坏死因子α在肌腱挛缩中的影响及肿瘤坏死因子α拮抗剂对肌腱挛缩的干预作用。 方法：20只健康雄性SD大鼠左后肢行跟腱应力屏蔽后随机数字表法均分为实验组和模型组,两组中随机各抽取5只大鼠以右后肢为正常对照组。建模后即刻实验组大鼠使用0.6 mg/kg重组人Ⅱ型肿瘤坏死因子受体-抗体融合蛋白、模型组使用1 mL磷酸缓冲盐溶液于大鼠皮下注射,后根据重组人Ⅱ型肿瘤坏死因子受体-抗体融合蛋白半衰期两组分别再注射3次,干预2周时大体下及透射电镜下观察跟腱形态学改变。 结果与结论：大体观察实验组跟腱明显比模型组细小、光滑,但较正常对照组粗。电镜下模型组胶原纤维束较实验组组疏松、紊乱;实验组横切面和纵切面均与正常对照组差异无显著性意义。说明,在2周时,肿瘤坏死因子α拮抗剂能明显预防应力屏蔽所致的肌腱挛缩。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

Adenovirus-Mediated Gene Transfer of Growth and Differentiation Factor-5 into Tenocytes and the Healing Rat Achilles Tendon

Growth and differentiation factor-5 (GDF-5) is known to induce tendon tissue and stimulate tendon healing. The hypothesis was that adenoviral GDF-5 transfer leads to transitory transgene expression and improves Achilles tendon healing. In vitro experiments were first performed with rat tenocytes. Transgene expression was evaluated by RT-PCR, Western blotting and GDF-5-ELISA. In vivo virus dosage and transgene expression were examined by a marker gene transfer (LacZ and luciferase). In the main experiment in 131 rats, adenovirus particles (3× 10¹⁰) were injected into transected Achilles tendons. The time course of GDF-5 mRNA expression was assessed by real-time RT-PCR. Histology and biomechanical testing were used to evaluate tendon healing and tensile strength. In vitro GDF-5 was secreted with a maximum after 2 weeks (330 ng GDF-5/10⁶ cells per 24 hr). In vivo GDF-5 transgene expression showed a maximum at 4 weeks. At 8 weeks, GDF-5 specimens were thicker (p < 0.05) with a trend to higher strength (p = 0,064). Histology showed greater cartilage formation in type II collagen stains than in controls. Injection of adenovirus particles successfully can deliver the GDF-5 gene in healing tendons and leads to thicker tendon regenerates after 8 weeks. This technique might become a new approach for nonsurgical treatment of tendon injuries.     

Glycogen depletion and resynthesis in the rat after downhill running

Summary to study the effect of downhill running on glycogen metabolism, 94 rats were exercised by running for 3 h on the level or down an 18° incline. Muscle and liver glycogen concentrations were measured before exercise and 0, 48 and 52 h postexercise. Rats were not fed during the first 48 h of recovery but ingested a glucose solution 48 h postexercise. Downhill running depleted glycogen in the soleus muscle and liver significantly more than level running (P<0.01). The amount of glycogen resynthesized in the soleus muscle and liver in fasting or nonfasting rats was not altered significantly by downhill running (P>0.05). On every day of recovery the rats were injected with dexamethasone, which induced similar increases in glycogen concentration in the soleus muscle and liver after the 52nd h of the postexercise period in the case of downhill and level running. The glycogen depletion and repletion results indicated that, under our experimental conditions, downhill running in the rat, a known model of eccentric exercise, affected muscle glycogen metabolism differently from eccentric cycling in humans.