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A potential new role for myofibroblasts in remodeling of sub-rupture fatigue tendon injuries by exercise.

ABSTRACT: Tendons are ineffective at repairing sub-rupture fatigue injuries. Accordingly, we evaluated whether an exercise protocol that we have previously found to decrease structural damage kinks in fatigue damaged tendons, leads to improvement in mechanical properties. We hypothesized that exercise that promotes repair of fatigue damage will decrease apoptosis and increase the population of myofibroblasts. Rat patellar tendons underwent in vivo fatigue loading for 500 or 7200 cycles. Animals resumed cage activity for 2-weeks, then either remained cage active or began treadmill running until sacrifice at 4- or 10-weeks post-fatigue loading. Exercise following fatigue damage increased the stiffness back towards naïve levels, decreased apoptosis and increased the population of myofibroblasts. Next, proteins associated with inhibition of apoptosis (Collagen VI) or activation of myofibroblast (pSmad 2/3, fibrillin, integrin subunits ?V and ?5) were evaluated. Data suggests that collagen VI may not be integral to inhibition of apoptosis in this context. Exercise increased pSmad 2/3 and fibrillin in the insertion region for the 7200-cycles group. In addition, exercise decreased integrin ?V and increased integrin ?5 in fatigue damaged tendons. Data suggests that a decrease in apoptosis and an increase in population of myofibroblasts may be integral to remodeling of fatigue damaged tendons.

SUBMITTER: Bell R

PROVIDER: S-EPMC5997675 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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A potential new role for myofibroblasts in remodeling of sub-rupture fatigue tendon injuries by exercise.

Bell Rebecca R Gendron N Remi NR Anderson Matthew M Flatow Evan L EL Andarawis-Puri Nelly N

Scientific reports 20180612 1

Tendons are ineffective at repairing sub-rupture fatigue injuries. Accordingly, we evaluated whether an exercise protocol that we have previously found to decrease structural damage kinks in fatigue damaged tendons, leads to improvement in mechanical properties. We hypothesized that exercise that promotes repair of fatigue damage will decrease apoptosis and increase the population of myofibroblasts. Rat patellar tendons underwent in vivo fatigue loading for 500 or 7200 cycles. Animals resumed ca ...[more]

PMID: 29895865

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Project description:BackgroundLow-cycle fatigue damage accumulating to the point of structural failure has been recently reported at the origin of the human anterior cruciate ligament under strenuous repetitive loading. If this can occur in a ligament, low-cycle fatigue damage may also occur in the connective tissue of muscle-tendon units. To this end, we reviewed what is known about how, when, and where injuries of muscle-tendon units occur throughout the body.PurposeTo systematically review injuries in the muscle-tendon-bone complex; assess the site of injury (muscle belly, musculotendinous junction [MTJ], tendon/aponeurosis, tendon/aponeurosis-bone junction, and tendon/aponeurosis avulsion), incidence, muscles and tendons involved, mechanism of injury, and main symptoms; and consider the hypothesis that injury may often be consistent with the accumulation of multiscale material fatigue damage during repetitive submaximal loading regimens.MethodsPubMed, Web of Science, Scopus, and ProQuest were searched on July 24, 2019. Quality assessment was undertaken using ARRIVE, STROBE, and CARE (Animal Research: Reporting In Vivo Experiments, Strengthening the Reporting of Observational Studies in Epidemiology, and the Case Report Statement and Checklist, respectively).ResultsOverall, 131 studies met the inclusion criteria, including 799 specimens and 2,823 patients who sustained 3,246 injuries. Laboratory studies showed a preponderance of failures at the MTJ, a viscoelastic behavior of muscle-tendon units, and damage accumulation at the MTJ with repetitive loading. Observational studies showed that 35% of injuries occurred in the tendon midsubstance; 28%, at the MTJ; 18%, at the tendon-bone junction; 13%, within the muscle belly and that 6% were tendon avulsions including a bone fragment. The biceps femoris was the most injured muscle (25%), followed by the supraspinatus (12%) and the Achilles tendon (9%). The most common symptoms were hematoma and/or swelling, tenderness, edema and muscle/tendon retraction. The onset of injury was consistent with tissue fatigue at all injury sites except for tendon avulsions, where 63% of the injuries were caused by an evident trauma.ConclusionExcluding traumatic tendon avulsions, most injuries were consistent with the hypothesis that material fatigue damage accumulated during repetitive submaximal loading regimens. If supported by data from better imaging modalities, this has implications for improving injury detection, prevention, and training regimens.

Project description:BACKGROUND:While some traumatic closed index extensor tendon ruptures at the musclotendinous junction have been previously reported, closed index extensor tendon pseudorupture due to intertendinous attenuation is exceedingly rare with only one case report of a gymnastics-related sports injury in the English literature. Herein, we report two non-sports injury related cases of traumatic index extensor tendon attenuation mimicking closed tendon rupture, including the pathological findings and intraoperative video of the attenuated extensor indicis proprius tendon. CASE PRESENTATION:A 28-year-old man and a 30-year-old man caught their hands in a high-speed drill and lathe, respectively, which caused a sudden forced flexion of their wrists. They could not actively extend the metacarpophalangeal joints of their index fingers. Intraoperatively, although the extensor indicis proprius and index extensor digitorum communes tendons were in continuity without ruptures, both tendons were attenuated and stretched. The attenuated index extensor tendons were reconstructed either with shortening by plication or step-cut when the tendon damage was less severe or, in severely attenuated tendons, with tendon grafting (ipsilateral palmaris longus) or tendon transfer. Six months after the operation, the active extension of the index metacarpophalangeal joints had recovered well. CONCLUSIONS:Two cases of traumatic index extensor tendon attenuation were treated successfully by shortening the attenuated tendon in combination with tendon graft or transfer. We recommend WALANT (wide-awake local anesthesia and no tourniquet) in the reconstruction surgery of index extensor tendon attenuation to determine the appropriate amount of tendon shortening or optimal tension for tendon grafting or transfer. Intraoperative voluntary finger movement is essential, as it is otherwise difficult to judge the stretch length of intratendinous elongation and extent of traumatic intramuscular damage affecting tendon excursion.

Project description:BACKGROUND:Injuries to tendons and ligaments make up a large portion of musculoskeletal injuries, and contribute to significant morbidity and healthcare costs. However, there is currently a poor understanding of the burden of these injuries at a population level. The purpose of this study was to quantify the burden and distribution of tendon and ligament injuries in the Aotearoa/New Zealand population. METHODS:Using the Accident Compensation Corporation (ACC, a no fault comprehensive compensation scheme encompassing all of Aotearoa/New Zealand; population in 2013 4.4 million) database, data specific to tendon and ligament injuries were identified between July 2010 and June 2016. The total number of claims made and the total cost of these claims per financial year were analyzed. Injuries were categorized by anatomical site, gender, ethnicity and age of the claimant. RESULTS:During the 6-year study period, the total number of tendon and ligament injury claims was 1,112,077, with a total cost of over $1.4 billion NZD. There was a 16.2% increase in the number of claims, and a 40% increase in the total cost of these injuries during this period. The majority of claims were made by people of European ethnicity, whilst the number of claims made by people of Asian ethnicity increased at the greatest rate; 52% (from 9047 claims in 2011) during the 6-year study period. Interestingly, M?ori (Indigenous New Zealanders) maintained the highest average cost per claim ($1614.05 NZD); 13% more than the overall average cost per claim ($1262.12 NZD). The most common sites of injury were the shoulder and knee; these injuries were also the greatest contributors to overall cost. The total costs of injuries peaked in claimants aged 40-54, irrespective of the number of claims made for that age group. CONCLUSIONS:Health and economic burdens of tendon and ligament injuries in Aotearoa/New Zealand are rising. The high healthcare costs underscore the urgent need for multifaceted interventions to reduce the incidence and improve clinical outcomes of tendon and ligament injuries.

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A potential new role for myofibroblasts in remodeling of sub-rupture fatigue tendon injuries by exercise.

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A potential new role for myofibroblasts in remodeling of sub-rupture fatigue tendon injuries by exercise.

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