Recovery Of Tendons Research Articles

Anti-Adhesive Resorbable Indomethacin/Bupivacaine-Eluting Nanofibers for Tendon Rupture Repair: In Vitro and In Vivo Studies.

The treatment and surgical repair of torn Achilles tendons seldom return the wounded tendon to its original elasticity and stiffness. This study explored the in vitro and in vivo simultaneous release of indomethacin and bupivacaine from electrospun polylactide-polyglycolide composite membranes for their capacity to repair torn Achilles tendons. These membranes were fabricated by mixing polylactide-polyglycolide/indomethacin, polylactide-polyglycolide/collagen, and polylactide-polyglycolide/bupivacaine with 1,1,1,3,3,3-hexafluoro-2-propanol into sandwich-structured composites. Subsequently, the in vitro pharmaceutic release rates over 30 days were determined, and the in vivo release behavior and effectiveness of the loaded drugs were assessed using an animal surgical model. High concentrations of indomethacin and bupivacaine were released for over four weeks. The released pharmaceutics resulted in complete recovery of rat tendons, and the nanofibrous composite membranes exhibited exceptional mechanical strength. Additionally, the anti-adhesion capacity of the developed membrane was confirmed. Using the electrospinning technique developed in this study, we plan on manufacturing degradable composite membranes for tendon healing, which can deliver sustained pharmaceutical release and provide a collagenous habitat.

Preclinical assessment of IL-1β primed human umbilical cord mesenchymal stem cells for tendon functional repair through TGF-β/IL-10 signaling

BackgroundInadequate repair capacity and disturbed immune compartments are the main pathological causes of tendinopathy. Transplantation of mesenchymal stem cells (MSCs) become an effective clinic option to alleviate tendinopathy. Interleukin-1β (IL-1β) could confer on MSCs enhanced immunoregulatory capability to remodel the repair microenvironment favoring tissue repair. Therefore, IL-1β activated UC-MSCs (1βUC-MSCs) may exert favorable efficacy in promoting tendon repair in a preclinical tendinopathy rat model. MethodsTendon-derived stem cells (TDSCs) were isolated and characterized. In vitro, the levels of immunoregulatory-related cytokines such as IL-1β, IL-6, IL-10, and TGF-β secreted by 1βUC-MSCs and unprimed UC-MSCs was measured. And tendon-specific markers expressed by TDSCs cultured with primed cultured medium (CM) or unprimed CM were detected. In vivo, Achilles tendinopathy was induced by 30 μL collagenase I injection in Sprague Dawley rats. One week later, the rats were randomly injected with UC-MSCs primed with IL-1β (106 cells per tendon), UC-MSCs, or PBS. After rats were sacrificed, histological evaluation, electron microscopy, biomechanical tests, gait performance were conducted to evaluate the structural and functional recovery of Achilles tendons. The inflammation and metabolic state of the extracellular matrix, and the potential mechanism were assessed by immunohistochemical staining and Western blot. ResultsUC-MSCs were activated by IL-1β to secrete higher levels of IL-10 and TGF-β while the secretion levels of IL-6 and IL-1β were not changed significantly, promoting a higher expression level of COL I and TNMD in TDSCs under proinflammatory environment. In vivo, the transplanted 1βUC-MSCs could survive up to 5 weeks after injection with tenogenic differentiation and improved tendon healing histologically semi-quantified by modified Bonar scores. This structural regeneration was further confirmed by observation of ultrastructural morphology, and led to good functional recovery including improved biomechanical properties and gait performance. During this process, the inflammatory response and metabolism of the extracellular matrix was improved through TGF-β/IL-10 pathway. ConclusionThis study demonstrated that the transplantation of UC-MSCs activated by IL-1β exhibited satisfactory ability for promoting tendon functional repair in a tendinopathy rat model. During this process, the balance of inflammatory response and extracellular matrix metabolism was remodeled, and the TGF-β/Smad2/3 and IL-10 signaling pathways were activated simultaneously. We cautiously conclude that the IL-1β primed UC-MSCs could be a promising strategy for enhancing the ability of MSCs to treat tendinopathy.

Validation of the Efficacy of Ultrasound Speckle Tracking in Measuring Tendon Gliding After Finger Flexor Tendon Repair.

Restricted tendon gliding is commonly observed in patients after finger flexor tendon (FFT) repair. The study described here was aimed at quantifying the amount of FFT gliding to evaluate the recovery of post-operative tendons using a 2-D radiofrequency (RF)-based ultrasound speckle tracking algorithm (UST). Ex vivo uniaxial tensile testing of porcine flexor tendons and in vivo isometric testing of human FFT were implemented to verify the efficacy of UST beforehand. The verified UST was then applied to the patients after FFT repair to compare tendon gliding between affected and healthy sides and to investigate its correlation with the joint range of motion (ROM). Excellent validity was confirmed with the average R2 value of 0.98, mean absolute error of 0.15 ± 0.08 mm and mean absolute percentage error of 5.19 ± 2.43% between results from UST and ex vivo testing. The test-retest reliability was verified with good agreement of ICC (0.90). The affected side exhibited less gliding (p=0.001) and smaller active ROM (p=0.002) than the healthy side. Meanwhile, a significant correlation between tendon gliding and passive ROM was found only on the healthy side (ρ=0.711, p=0.009). The present study provides a promising protocol to evaluate post-operative tendon recovery by quantifying the amount of FFT gliding with a validated UST. FFT gliding in patients with different levels of ROM restriction should be further explored for categorizing the severity of tendon adhesion.

Effect of loading speed on gap resistance and tensile strength of flexor tendon repair under cyclic loading test

Postoperative digit motion is important for the functional recovery of injured tendons. To date, it is unknown whether the loading speed impacts the biomechanical properties of a repaired tendon. This study investigated the effect of loading speed on the gap resistance and tensile strength of tendon repairs. One hundred porcine flexor tendons were repaired with two core sutures, 4-strand modified Kessler and double Q, and cyclically loaded at the speeds of 10, 40, 80, 160, and 320 mm/min. The number of tendons that formed an initial or 2 mm gap at the repair site during cyclic loading, stiffness at the 1st and 20th loading cycles, gap size between tendon ends when cyclic loading ended, and the ultimate strength were recorded. Under the lowest loading speed, the tendons repaired with the 4-strand modified Kessler suture developed significantly larger gaps and smaller stiffness than those with a greater loading speed. The loading speed did not affect the maximum strength of both tendon repairs. The findings suggest that very slow motion promotes gap formation of tendon repair with inferior gap resistance. The rate corresponds to regular hand action or the tendon core suture possessing a strong gap resistance increases the safety margin during early active finger movement. Our findings help to guide the exercise regimens after tendon surgery.

Mechanical stretch promotes tenocyte migration via chromatin remodeling-mediated nuclear morphology changes.

Wound healing and function recovery of injured tendons is still a big challenge for orthopaedic surgery. Evidence in clinic shows that early controlled motion has significant favorable effects on tendon healing, however, the mechanisms involved in are not fully understood. In the present study, it was shown that an appropriate mechanical stretch (10% strain, 0.5 Hz for 1 h) evidently promotes rat tenocyte migration and nuclear morphology changes. The farther research discovered that mechanical stretch had no effect on Lamin A/C expression, but it could promote chromatin decondensation. Moreover, the histone modification plays an important role in mechanical stretch-mediated chromatin decondensation. Inhibition histone modification could inhibit mechanical stretch-promoted nuclear morphology changes and tenocyte migration. These results indicating that mechanical stretch may promote tenocyte migration via chromatin remodeling-mediated nuclear morphology changes, which contribute to a better understanding of the role of mechanical stretch on tenocyte migration and repair of injured tendon. This article is protected by copyright. All rights reserved.

TGFβ1-transfected tendon stem cells promote tendon fibrosis

BackgroundIn aged people, tendon injuries frequently occur during sporting and daily activities. In clinical practice, typical physiotherapeutic, pharmacotherapeutic, and surgical techniques do not result in the full recovery of injured tendons, which may lead to chronic degenerative disease.MethodsWe first isolated tendon stem cells (TSCs) from rats and transfected them with the TGFβ1 gene, resulting in TGFβ1-TSCs. The proliferation of TSCs was detected using the Cell Counting Kit 8, and TSCs were identified by immunofluorescence analysis and differentiation capacity analysis. Aggrecan, COL2A1, alpha smooth muscle actin (α-SMA), and p-Smad2 expression levels were detected using western blotting and quantitative reverse transcription polymerase chain reaction. Additionally, a tendon injury model was generated to explore the effect of TGFβ1 on the repair of the tendon by TSCs.ResultsCompared with fibrinogen treatment, TSC + fibrinogen or TGFβ1-TSC + fibrinogen treatment significantly promoted the fibrosis of injured tendons, as evidenced by histological analyses, with TGFβ1-TSC + fibrinogen having a greater effect than TSC + fibrinogen. In TGFβ1-TSCs, increased expression levels of aggrecan and COL2A1 indicated that TGFβ1 signaling induced chondrogenic differentiation. Meanwhile, the increased collagen and α-SMA protein levels indicated that TGFβ1 promoted fibrogenesis. Additionally, TGFβ1 stimulated the production of phosphorylated Smad2 in TSCs, which suggested that the chondrogenic and fibrogenic differentiation of TSCs, as well as tissue regeneration, may be associated with the TGFβ1/Smad2 pathway.ConclusionTGFβ1-TSC therapy may be a candidate for effective tendon fibrosis.

Inhibition of glucose use improves structural recovery of injured Achilles tendon in mice.

Injured tendons do not regain their native structure except at fetal or very young ages. Healing tendons often show mucoid degeneration involving accumulation of sulfated glycosaminoglycans (GAGs), but its etiology and molecular base have not been studied substantially. We hypothesized that quality and quantity of gene expression involving the synthesis of proteoglycans having sulfated GAGs are altered in injured tendons and that a reduction in synthesis of sulfated GAGs improves structural and functional recovery of injured tendons. C57BL6/j mice were subjected to Achilles tendon tenotomy surgery. The injured tendons accumulated sulfate proteoglycans as early as 1-week postsurgery and continued so by 4-week postsurgery. Transcriptome analysis revealed upregulation of a wide range of proteoglycan genes that have sulfated GAGs in the injured tendons 1 and 3 weeks postsurgery. Genes critical for enzymatic reaction of initiation and elongation of chondroitin sulfate GAG chains were also upregulated. After the surgery, mice were treated with the 2-deoxy-d-glucose (2DG) that inhibits conversion of glucose to glucose-6-phosphate, an initial step of glucose metabolism as an energy source and precursors of monosaccharides of GAGs. The 2DG treatment reduced accumulation of sulfated proteoglycans, improved collagen fiber alignment, and reduced the cross-sectional area of the injured tendons. The modulus of the 2DG-treated groups was higher than that in the vehicle group, but not of statistical significance. Our findings suggest that mucoid degeneration in injured tendons may result from the upregulated expression of genes involved the synthesis of sulfate proteoglycans and can be inhibited by reduction of glucose utilization.

Microcurrent and adipose-derived stem cells modulate genes expression involved in the structural recovery of transected tendon of rats.

Tendon injuries are common and have a high incidence of re-rupture that can cause loss of functionality. Therapies with adipose-derived stem cells (ASC) and the microcurrent (low-intensity electrical stimulation) application present promising effects on the tissue repair. We analyzed the expression of genes and the participation of some molecules potentially involved in the structural recovery of the Achilles tendon of rats, in response to the application of both therapies, isolated and combined. The tendons were distributed in five groups: normal (N), transected (T), transected and ASC (C) or microcurrent (M) or with ASC, and microcurrent (MC). Microcurrent therapy was beneficial for tendon repair, as it was observed a statistically significant increase in the organization of the collagen fibers, with involvement of the TNC, CTGF, FN, FMDO, and COL3A1 genes as well as PCNA, IL-10, and TNF-α. ASC therapy significantly increased the TNC and FMDO genes expression with no changes in the molecular organization of collagen. With the association of therapies, a significant greater collagen fibers organization was observed with involvement of the FMOD gene. The therapies did not affect the expression of COL1A1, SMAD2, SMAD3, MKX, and EGR1 genes, nor did they influence the amount of collagen I and III, caspase-3, tenomodulin (Tnmd), and hydroxyproline. In conclusion, the application of the microcurrent isolated or associated with ASC increased the organization of the collagen fibers, which can result in a greater biomechanical resistance in relation to the tendons treated only with ASC. Future studies will be needed to demonstrate the biological effects of these therapies on the functional recovery of injured tendons.

Aged Tendon Stem/Progenitor Cells Are Less Competent to Form 3D Tendon Organoids Due to Cell Autonomous and Matrix Production Deficits.

Tendons are dense connective tissues, which are critical for the integrity and function of our musculoskeletal system. During tendon aging and degeneration, tendon stem/progenitor cells (TSPCs) experience profound phenotypic changes with declined cellular functions that can be linked to the known increase in complications during tendon healing process in elderly patients. Tissue engineering is a promising approach for achieving a complete recovery of injured tendons. However, use of autologous cells from aged individuals would require restoring the cellular fitness prior to implantation. In this study, we applied an established cell sheet model for in vitro tenogenesis and compared the sheet formation of TSPC derived from young/healthy (Y-TSPCs) versus aged/degenerative (A-TSPCs) human Achilles tendon biopsies with the purpose to unravel differences in their potential to form self-assembled three-dimensional (3D) tendon organoids. Using our three-step protocol, 4 donors of Y-TSPCs and 9 donors of A-TSPCs were subjected to cell sheet formation and maturation in a period of 5 weeks. The sheets were then cross evaluated by weight and diameter measurements; quantification of cell density, proliferation, senescence and apoptosis; histomorphometry; gene expression of 48 target genes; and collagen type I protein production. The results revealed very obvious and significant phenotype in A-TSPC sheets characterized by being fragile and thin with poor tissue morphology, and significantly lower cell density and proliferation, but significantly higher levels of the senescence-related gene markers and apoptotic cells. Quantitative gene expression analyses at the mRNA and protein levels, also demonstrated abnormal molecular circuits in the A-TSPC sheets. Taken together, we report for the first time that A-TSPCs exhibit profound deficits in forming 3D tendon tissue organoids, thus making the cell sheet model suitable to investigate the molecular mechanisms involved in tendon aging and degeneration, as well as examining novel pharmacologic strategies for rejuvenation of aged cells.

Prostaglandin D2 signaling is not involved in the recovery of rat hind limb tendons from injury.

Injured tendons heal through the formation of a fibrovascular scar that has inferior mechanical properties compared to native tendon tissue. Reducing inflammation that occurs as a result of the injury could limit scar formation and improve functional recovery of tendons. Prostaglandin D2 (PGD2) plays an important role in promoting inflammation in some injury responses and chronic disease processes, and the inhibition of PGD2 has improved healing and reduced disease burden in animal models and early clinical trials. Based on these findings, we sought to determine the role of PGD2 signaling in the healing of injured tendon tissue. We tested the hypothesis that a potent and specific inhibitor of hematopoietic PGD synthase (HPGDS), GSK2894631A, would improve the recovery of tendons of adult male rats following an acute tenotomy and repair. To test this hypothesis, we performed a full‐thickness plantaris tendon tenotomy followed by immediate repair and treated rats twice daily with either 0, 2, or 6 mg/kg of GSK2894631A. Tendons were collected either 7 or 21 days after surgical repair, and mechanical properties of tendons were assessed along with RNA sequencing and histology. While there were some differences in gene expression across groups, the targeted inhibition of HPGDS did not impact the functional repair of tendons after injury, as HPGDS expression was surprisingly low in injured tendons. These results indicate that PGD2 signaling does not appear to be important in modulating the repair of injured tendon tissue.

Viscoelasticity of Tendons Under Transverse Compression.

Tendons are highly anisotropic and also viscoelastic. For understanding and modeling their 3D deformation, information is needed on their viscoelastic response under off-axis loading. A study was made, therefore, of creep and recovery of bovine digital extensor tendons when subjected to transverse compressive stress of up to ca. 100 kPa. Preconditioned tendons were compression tested between glass plates at increasing creep loads. The creep response was anomalous: the relative rate of creep reduced with the increasing stress. Over each ca. 100 s creep period, the transverse creep deformation of each tendon obeyed a power law dependence on time, with the power law exponent falling from ca. 0.18 to an asymptote of ca. 0.058 with the increasing stress. A possible explanation is stress-driven dehydration, as suggested previously for the similar anomalous behavior of ligaments. Recovery after removal of each creep load was also anomalous. Relative residual strain reduced with the increasing creep stress, but this is explicable in terms of the reducing relative rate of creep. When allowance was made for some adhesion occurring naturally between tendon and the glass plates, the results for a given load were consistent with creep and recovery being related through the Boltzmann superposition principle (BSP). The tendon tissue acted as a pressure-sensitive adhesive (PSA) in contact with the glass plates: explicable in terms of the low transverse shear modulus of the tendons.

The role of platelet gel in osteoarticular injuries of young and old patients.

BackgroundThe use of autologous platelet gel in orthopedics is effective in accelerating the healing process of osteochondral, muscle, tendon and ligament lesions. The aim of our study was to verify whether the variability in response to infiltration with platelet gel was dependent on the underlying disease treated, sex and age of the patients. During four years, 140 patients have been treated for musculoskeletal injuries by infiltration of gel platelet and lysate platelet obtained from autologous thrombin, with echo-ultrasound guided. The response to treatment was assessed at different time points T0, T1, T2 with respect to pain estimation (VAS), joint mobility (ROM scale) and echo-ultrasound evaluation. This data collection has allowed classifying the response to treated lesions in three categories: NR (no response), PR (partial response), CR (complete response).ResultsThe data here reported showed that the ability to physical recovery response is evident in tendon injuries, while the large joints injuries gave a poor response. Almost all patients showed a significant pain relief after the first infiltration, but in terms of echo-ultrasound evaluation and tissue repair, only the muscle and tendon injuries showed hyperechoic areas, signs or evidences of repair. Concerning the correlation between response to infiltration with platelet gel and gender/age of the patients, the clinical results appear not influenced by the age and the gender of the patient.DiscussionOur data indicate that, pain relief and ability to physical recovery of muscles, tendons and ligaments depend on tissue repair clearly visible by echo ultrasound evaluation. On the other hand tissue repair seems not occur in the large joints (hip and knee) where arthritis and /or corrosion of articular cartilage cannot be repaired and the only relief is exclusively linked to the reduction of periarticular inflammation (reduction of the inflammatory leakage and signs).

“Soft, hard, or just right?” Applications and limitations of axial-strain sonoelastography and shear-wave elastography in the assessment of tendon injuries

Injury to a tendon leads to alterations in the mechanical properties of the tendon. Axial-strain sonoelastography and shear-wave elastography are relatively new, real-time imaging techniques that evaluate the mechanical properties of tendons in addition to the existing morphological and vascular information that is obtained with traditional imaging tools. Axial-strain sonoelastography displays the subjective distribution of strain data on an elastogram caused by tissue compression, whereas shear-wave elastography provides a more objective, quantitative measure of the intrinsic tissue elasticity using the acoustic push-pulse. Recent studies suggest that axial-strain sonoelastography is able to distinguish between asymptomatic and diseased tendons, and is potentially more sensitive than conventional ultrasound in detecting early tendinopathy. Shear-wave elastography seems to be a feasible tool for depicting elasticity and functional recovery of tendons after surgical management. While initial results have been promising, axial-strain sonoelastography and shear-wave elastography have not yet found routine use in wider clinical practice. Possible barriers to the dissemination of axial-strain sonoelastography technique include operator dependency, technical limitations such as artefacts and lack of reproducibility and quantification of sonoelastography data. Shear-wave elastography may improve the reproducibility of elastography data, although there is only one published study on the topic to date. Large-scale longitudinal studies are needed to further elucidate the clinical relevance and potential applications of axial-strain sonoelastography and shear-wave elastography in diagnosing, predicting, and monitoring the progress of tendon healing before they can be widely adopted into routine clinical practice.

Effects of Different Exercise Amount on the Recovery of Rats' Achilles Tendons

This study aimed to investigate the effects of different exercise amount on the recovery of rats injured Achilles tendon. Fifty-four Sprague-Dawley (SD) male rats (eight weeks old and 200 ~ 250 g) were randomly assigned to three groups: control, 15-minute (15 mins group) and 30-minute (30 mins group). The rats' Achilles tendon of right legs were cut first and then intervened by different exercise amount after the 5th day of Achilles injury and exercised once for each day. They exercised at the speed of 4 meters/min for first two days, and then the speed was increased to 12 meters/min. No exercise was performed in the control group. The functions of Achilles tendon were evaluated on the 5th, 12th, 19th and 28th day, and then all rats were sacrificed on the 28th day. The morphology, growth of collagen, breaking strength of tendon, tensile stress and recovery index were observed. Results: We found that AFI values on 12th day was significantly greater, 30 mins group was significantly greater than control and 15 mins. On the 28th day, 30 mins group was significantly higher than the control. Achilles tendon diameters in all experimental groups were significantly bigger than normal groups. In experimental groups, the control group was significantly bigger than the 30-min group. Collagens: Groups with exercise were found to be tidier. The breaking strength of tendon: Control experimental group was significantly higher than control normal. Experimental groups were not significantly different. Tensile stress: Control experimental group was significantly less than all the normal groups. Experimental groups were not significantly different. Recovery index: All the three experimental groups were not significantly different. In conclusion, the exercise program utilized in this study, we found that exercise amount won't affect breaking strength and tensile stress, but it may promote adjustability of walking and arrangement of newly collagen more order after injury.

The time course of in vivo recovery of transverse strain in high-stress tendons following exercise

ObjectiveTo evaluate the time course of the recovery of transverse strain in the Achilles and patellar tendon following a bout of resistance exercise.MethodsSeventeen healthy adults underwent sonographic examination of the...

Re‐establishment of cytoskeletal tensional homeostasis in lax tendons occurs through an actin‐mediated cellular contraction of the extracellular matrix

Cytoskeletal tensional homeostasis is known to be an important factor in controlling catabolic gene expression in tendon cells. Loss of cell tension in lax rat tail tendon fascicles (RTTfs) has been associated with an upregulation of MMP-13 gene expression and protein synthesis. To determine the role of the actin cytoskeleton in re-establishing tensional homeostasis in lax tendons, RTTfs were allowed to freely contract in vitro for 8 days. The cultured RTTfs contracted rapidly, reaching 50% of their initial length by 3 days. This contraction was associated with the presence of α-smooth muscle actin positive cells within the tendon. Disruption of the actin network by cytochalasian D caused an immediate and significant elongation of the contracted RTTfs. Subsequent removal of the cytochalasian D re-initiated the contraction process. When lax RTTfs were allowed to contract between fixed clamps in culture and become taut, they demonstrated a marked decrease in MMP-13 staining intensity when compared to freely contracting RTTfs. The ability of native tendon cells to contract lax tendons and re-establish their homeostatic "set point" with respect to collagenase production may be an important mechanism in the recovery of tendons elongated by injury, surgical positioning, or cyclic, viscoelastic creep secondary to repetitive exercise.

Functional recovery of tendons and nerves after early repair of electric burns of extremities with cutaneous and myocutaneous flaps

Functional recovery of tendons and nerves after early repair of electric burns of extremities with cutaneous and myocutaneous flaps