The innervation pattern of the human Achilles tendon: studies of the normal and tendinosis tendon with markers for general and sensory innervation

Pain-free normal Achilles tendons and chronic painful Achilles tendons were examined by the use of antibodies against a general nerve marker (protein gene-product 9.5, PGP9.5), sensory markers (substance P, SP; calcitonin gene-related peptide, CGRP), and immunohistochemistry. In the normal tendons, immunoreactions against PGP9.5 and against SP/CGRP were encountered in the paratendinous loose connective tissue, being confined to nerve fascicles and to nerve fibers located in the vicinity of blood vessels. To some extent, these immunoreactions also occurred in the tendon tissue proper. Immunoreaction against PGP9.5 and against SP/CGRP was also observed in the tendinosis samples and included immunoreactive nerve fibers that were intimately associated with small blood vessels. In conclusion, Mechanoreceptors (sensory corpuscles) were occasionally observed, nerve-related components are present in association with blood vessels in both the normal and the tendinosis tendon.     

The Effects of Irreversible Electroporation on the Achilles Tendon: An Experimental Study in a Rabbit Model

Background

To evaluate the potential effects of irreversible electroporation ablation on the Achilles tendon in a rabbit model and to compare the histopathological and biomechanical changes between specimens following electroporation ablation and radiofrequency ablation.

Methods

A total of 140 six-month-old male New Zealand rabbits were used. The animals were randomly divided into two groups, 70 in the radiofrequency ablation group and 70 in the electroporation group. In situ ablations were applied directly to the Achilles tendons of rabbits using typical electroporation (1800 V/cm, 90 pulses) and radiofrequency ablation (power control mode) protocols. Histopathological and biomechanical evaluations were performed to examine the effects of electroporation ablation and radiofrequency ablation over time.

Results

Both electroporation and radiofrequency ablation produced complete cell ablation in the target region. Thermal damage resulted in tendon rupture 3 days post radiofrequency ablation. In contrast, electroporation-ablated Achilles tendons preserved their biomechanical properties and showed no detectable rupture at this time point. The electroporation-ablated tendons exhibited signs of recovery, including tenoblast regeneration and angiogenesis within 2 weeks, and the restoration of their integral structure was evident within 12 weeks.

Conclusions

When applying electroporation to ablate solid tumors, major advantage could be that collateral damage to adjacent tendons or ligaments is minimized due to the unique ability of electroporation ablation to target the cell membrane. This advantage could have a significant impact on the field of tumor ablation near vital tendons or ligaments.     

Role of tissue engineered collagen based tridimensional implant on the healing response of the experimentally induced large Achilles tendon defect model in rabbits: a long term study with high clinical relevance

Background

Tendon injury is one of the orthopedic conditions poses with a significant clinical challenge to both the surgeons and patients. The major limitations to manage these injuries are poor healing response and development of peritendinous adhesions in the injured area. This study investigated the effectiveness of a novel collagen implant on tendon healing in rabbits.

Results

Seventy five mature White New-Zealand rabbits were divided into treated (n = 55) and control (n = 20) groups. The left Achilles tendon was completely transected and 2 cm excised. The defects of the treated animals were filled with collagen implants and repaired with sutures, but in control rabbits the defects were sutured similarly but the gap was left untreated. Changes in the injured and normal contralateral tendons were assessed weekly by measuring the diameter, temperature and bioelectrical characteristics of the injured area. Clinical examination was done and scored. Among the treated animals, small pilot groups were euthanized at 5, 10, 15, 20, 30, 40 and 60 (n = 5 at each time interval) and the remainder (n = 20) and the control animals at 120 days post injury (DPI). The lesions of all animals were examined at macroscopic and microscopic levels and the dry matter content, water delivery and water uptake characteristics of the lesions and normal contralateral tendons of both groups were analyzed at 120 DPI.No sign of rejection was seen in the treated lesions. The collagen implant was invaded by the inflammatory cells at the inflammatory phase, followed by fibroplasia phase in which remnant of the collagen implant were still present while no inflammatory reaction could be seen in the lesions. However, the collagen implant was completely absorbed in the remodeling phase and the newly regenerated tendinous tissue filled the gap. Compared to the controls, the treated lesions showed improved tissue alignment and less peritendinous adhesion, muscle atrophy and fibrosis. They also showed significantly better clinical scoring, indices for water uptake and water absorption, and bioelectrical characteristics than the controls.

Conclusion

This novel collagen implant was biodegradable, biocompatible and possibly could be considered as a substitute for auto and allografts in clinical practice in near future.     

Serum Levels of Oxylipins in Achilles Tendinopathy: An Exploratory Study

Background

Linoleic acid-derived oxidation products are found in experimental pain models. However, little is known about the levels of such oxylipins in human pain. In consequence, in the present study, we have undertaken a lipidomic profiling of oxylipins in blood serum from patients with Achilles tendinopathy and controls.

Methodology/Principal findings

A total of 34 oxylipins were analysed in the serum samples. At a significance level of P<0.00147 (<0.05/34), two linoleic acid-derived oxylipins, 13-hydroxy-10E,12Z-octadecadienoic (13-HODE) and 12(13)-dihydroxy-9Z-octadecenoic acid (12,13-DiHOME) were present at significantly higher levels in the Achilles tendinopathy samples. This difference remained significant when the dataset was controlled for age, gender and body-mass index. In contrast, 0/21 of the arachidonic acid- and 0/4 of the dihomo-γ-linolenic acid, eicosapentaenoic acid or docosahenaenoic acid-derived oxylipins were higher in the patient samples at this level of significance. The area under the Receiver-Operator Characteristic (ROC) curve for 12,13-DiHOME was 0.91 (P<0.0001). Levels of four N-acylethanolamines were also analysed and found not to be significantly different between the controls and the patients at the level of P<0.0125 (<0.05/4).

Conclusions/Significance

It is concluded from this exploratory study that abnormal levels of linoleic acid-derived oxylipins are seen in blood serum from patients with Achilles tendinopathy. Given the ability of two of these, 9- and 13-HODE to activate transient receptor potential vanilloid 1, it is possible that these changes may contribute to the symptoms seen in Achilles tendinopathy.     

Effect of Footwear Modifications on Oscillations at the Achilles Tendon during Running on a Treadmill and Over Ground: A Cross-Sectional Study

Background

Achilles tendon injuries are known to commonly occur in runners. During running repeated impacts are transferred in axial direction along the lower leg, therefore possibly affecting the oscillation behavior of the Achilles tendon. The purpose of the present study was to explore the effects of different footwear modifications and different ground conditions (over ground versus treadmill) on oscillations at the Achilles tendon.

Methods

Oscillations were measured in 20 male runners using two tri-axial accelerometers. Participants ran in three different shoe types on a treadmill and over ground. Data analysis was limited to stance phase and performed in time and frequency space. Statistical comparison was conducted between oscillations in vertical and horizontal direction, between running shoes and between ground conditions (treadmill versus over ground running).

Results

Differences in the oscillation behavior could be detected between measurement directions with peak accelerations in the vertical being lower than those in the horizontal direction, p < 0.01. Peak accelerations occurred earlier at the distal accelerometer than at the proximal one, p < 0.01. Average normalized power differed between running shoes (p < 0.01) with harder damping material resulting in higher power values. Little to no power attenuation was found between the two accelerometers. Oscillation behavior of the Achilles tendon is not influenced by ground condition.

Conclusion

Differences in shoe configurations may lead to variations in running technique and impact forces and therefore result in alterations of the vibration behavior at the Achilles tendon. The absence of power attenuation may have been caused by either a short distance between the two accelerometers or high stiffness of the tendon. High stiffness of the tendon will lead to complete transmission of the signal along the Achilles tendon and therefore no attenuation occurs.     

Increased expression of cannabinoid CB₁ receptors in Achilles tendinosis

Background

The endogenous cannabinoid system is involved in the control of pain. However, little is known as to the integrity of the cannabinoid system in human pain syndromes. Here we investigate the expression of the cannabinoid receptor 1 (CB₁) in human Achilles tendons from healthy volunteers and from patients with Achilles tendinosis.

Methodology

Cannabinoid CB₁ receptor immunoreactivity (CB₁IR) was evaluated in formalin-fixed biopsies from individuals suffering from painful Achilles tendinosis in comparison with healthy human Achilles tendons.

Principal Findings

CB₁IR was seen as a granular pattern in the tenocytes. CB₁IR was also observed in the blood vessel wall and in the perineurium of the nerve. Quantification of the immunoreactivity in tenocytes showed an increase of CB₁ receptor expression in tendinosis tissue compared to control tissue.

Conclusion

Expression of cannabinoid receptor 1 is increased in human Achilles tendinosis suggesting that the cannabinoid system may be dysregulated in this disorder.     

Experimental Diabetes Induces Structural,Inflammatory and Vascular Changes of Achilles Tendons

This study aims to demonstrate how the state of chronic hyperglycemia from experimental Diabetes Mellitus can influence the homeostatic imbalance of tendons and, consequently, lead to the characteristics of tendinopathy. Twenty animals were randomly divided into two experimental groups: control group, consisting of healthy rats and diabetic group constituted by rats induced to Diabetes Mellitus I. After twenty-four days of the induction of Diabetes type I, the Achilles tendon were removed for morphological evaluation, cellularity, number and cross-sectional area of blood vessel, immunohistochemistry for Collagen type I, VEGF and NF-κB nuclear localization sequence (NLS) and nitrate and nitrite level. The Achilles tendon thickness (µm/100g) of diabetic animals was significantly increased and, similarly, an increase was observed in the density of fibrocytes and mast cells in the tendons of the diabetic group. The average number of blood vessels per field, in peritendinous tissue, was statistically higher in the diabetic group 3.39 (2.98) vessels/field when compared to the control group 0.89 (1.68) vessels/field p = 0.001 and in the intratendinous region, it was observed that blood vessels were extremely rare in the control group 0.035 (0.18) vessels/field and were often present in the tendons of the diabetic group 0.89 (0.99) vessels/field. The immunohistochemistry analysis identified higher density of type 1 collagen and increased expression of VEGF as well as increased immunostaining for NFκB p50 NLS in the nucleus in Achilles tendon of the diabetic group when compared to the control group. Higher levels of nitrite/nitrate were observed in the experimental group induced to diabetes. We conclude that experimental DM induces notable structural, inflammatory and vascular changes in the Achilles tendon which are compatible with the process of chronic tendinopathy.     

Proteomics Perspectives in Rotator Cuff Research: A Systematic Review of Gene Expression and Protein Composition in Human Tendinopathy

Background

Rotator cuff tendinopathy including tears is a cause of significant morbidity. The molecular pathogenesis of the disorder is largely unknown. This review aimed to present an overview of the literature on gene expression and protein composition in human rotator cuff tendinopathy and other tendinopathies, and to evaluate perspectives of proteomics – the comprehensive study of protein composition - in tendon research.

Materials and Methods

We conducted a systematic search of the literature published between 1 January 1990 and 18 December 2012 in PubMed, Embase, and Web of Science. We included studies on objectively quantified differential gene expression and/or protein composition in human rotator cuff tendinopathy and other tendinopathies as compared to control tissue.

Results

We identified 2199 studies, of which 54 were included; 25 studies focussed on rotator cuff or biceps tendinopathy. Most of the included studies quantified prespecified mRNA molecules and proteins using polymerase chain reactions and immunoassays, respectively. There was a tendency towards an increase of collagen I (11 of 15 studies) and III (13 of 14), metalloproteinase (MMP)-1 (6 of 12), -9 (7 of 7), -13 (4 of 7), tissue inhibitor of metalloproteinase (TIMP)-1 (4 of 7), and vascular endothelial growth factor (4 of 7), and a decrease in MMP-3 (10 of 12). Fourteen proteomics studies of tendon tissues/cells failed inclusion, mostly because they were conducted in animals or in vitro.

Conclusions

Based on methods, which only allowed simultaneous quantification of a limited number of prespecified mRNA molecules or proteins, several proteins appeared to be differentially expressed/represented in rotator cuff tendinopathy and other tendinopathies. No proteomics studies fulfilled our inclusion criteria, although proteomics technologies may be a way to identify protein profiles (including non-prespecified proteins) that characterise specific tendon disorders or stages of tendinopathy. Thus, our results suggested an untapped potential for proteomics in tendon research.     

Uphill running improves rat Achilles tendon tissue mechanical properties and alters gene expression without inducing pathological changes

Overuse Achilles tendinopathy is a common and challenging problem in sports medicine. Little is known about the etiology of this disorder, and the development of a good animal model for overuse tendinopathy is essential for advancing insight into the disease mechanisms. Our aim was to test a previously proposed rat model for Achilles tendon overuse. Ten adult male Sprague-Dawley rats ran on a treadmill with 10° incline, 1 h/day, 5 days/wk (17-20 m/min) for 12 wk and were compared with 12 control rats. Histological, mechanical, and gene-expression changes were measured on the Achilles tendons after the intervention, and local tendon glucose-uptake was measured before and after the intervention with positron emission tomography. No differences were detected between runners and controls in tissue histology or in glucose uptake, indicating that tendon pathology was not induced. Greater tendon tissue modulus (P < 0.005) and failure stress/body weight (P < 0.02) in runners compared with controls further supported that tendons successfully adapted to uphill running. Several genes of interest were regulated after 12 wk of running. Expression of collagen III and insulin-like growth factor I was increased, while collagen I was unchanged, and decreases were seen in noncollagen matrix components (fibromodulin and biglycan), matrix degrading enzymes, transforming growth factor-β1, and connective tissue growth factor. In conclusion, the tested model could not be validated as a model for Achilles tendinopathy, as the rats were able to adapt to 12 wk of uphill running without any signs of tendinopathy. Improved mechanical properties were observed, as well as changes in gene-expression that were distinctly different from what is seen in tendinopathy and in response to short-term tendon loading.     

Presence of substance P and the neurokinin-1 receptor in tenocytes of the human Achilles tendon

Nerve signal substances, such as the tachykinin substance P (SP), may be involved in the changes that occur in response to tendinopathy (tendinosis). It is previously known that the level of SP innervation within tendon tissue is limited, but results of experimental studies have suggested that SP may have stimulatory, angiogenetic and healing effects in injured tendons. Therefore, it would be of interest to know if there is a local SP-supply in tendon tissue. In the present study, the patterns of expression of SP and its preferred receptor, the neurokinin-1 receptor (NK-1 R), in normal and tendinosis human Achilles tendons were analyzed by use of both immunohistochemistry and in situ hybridization. We found that there was expression of SP mRNA in tenocytes, and that tenocytes showed expression of NK-1 R at protein as well as mRNA levels. The observations concerning both SP and NK-1 R were most evident for tenocytes in tendinosis tendons. Our findings suggest that SP is produced in tendinosis tendons, and furthermore that SP has marked effects on the tenocytes via the NK-1 R. It cannot be excluded that the SP effects are of importance concerning the processes of reorganization and healing that occur for tendon tissue in tendinosis. In conclusion, it appears as if SPergic autocrine/paracrine effects occur in tendon tissue during the processes of tendinosis, hitherto unknown effects for human tendons.     

Changes in Morphological and Elastic Properties of Patellar Tendon in Athletes with Unilateral Patellar Tendinopathy and Their Relationships with Pain and Functional Disability

Background

Patellar tendinopathy (PT) is one of the most common knee disorders among athletes. Changes in morphology and elasticity of the painful tendon and how these relate to the self-perceived pain and dysfunction remain unclear.

Objectives

To compare the morphology and elastic properties of patellar tendons between athlete with and without unilateral PT and to examine its association with self-perceived pain and dysfunction.

Methods

In this cross-sectional study, 33 male athletes (20 healthy and 13 with unilateral PT) were enrolled. The morphology and elastic properties of the patellar tendon were assessed by the grey and elastography mode of supersonic shear imaging (SSI) technique while the intensity of pressure pain, self-perceived pain and dysfunction were quantified with a 10-lb force to the most painful site and the Victorian Institute of Sport Assessment-patella (VISA-P) questionnaire, respectively.

Results

In athletes with unilateral PT, the painful tendons had higher shear elastic modulus (SEM) and larger tendon than the non-painful side (p<0.05) or the dominant side of the healthy athletes (p<0.05). Significant correlations were found between tendon SEM ratio (SEM of painful over non-painful tendon) and the intensity of pressure pain (rho  = 0.62; p = 0.024), VISA-P scores (rho  = −0.61; p = 0.026), and the sub-scores of the VISA-P scores on going down stairs, lunge, single leg hopping and squatting (rho ranged from −0.63 to −0.67; p<0.05).

Conclusions

Athletes with unilateral PT had stiffer and larger tendon on the painful side than the non-painful side and the dominant side of healthy athletes. No significant differences on the patellar tendon morphology and elastic properties were detected between the dominant and non-dominant knees of the healthy control. The ratio of the SEM of painful to non-painful sides was associated with pain and dysfunction among athletes with unilateral PT.     

Identification and In Vitro Derivation of Spermatogonia in Beagle Testis

Background

In vitro culture of spermatogonial stem cells (SSCs) is important for exploration of SSCs self-renewal, differentiation, and manipulation. There are several reports on rodent SSC cultures; however, data on SSC cultures in domestic animals are limited. To provide basic scientific information on canine SSC cultures, we report canine testes development, and the development of spermatogonia-derived colonies (SDCs) for in vitro cultures.

Methodology/Principal Findings

Testes from 2-, 3-, and 12-month-old beagles were used for histology, immunohistochemistry, in vitro culture, immunocytochemistry, and PCR. Protein gene product 9.5 (PGP9.5)-positive spermatogonia, both single and paired, were found to be abundant in the testes of 2-month-old beagles. stempro-34 and Dulbecco''s modified Eagle medium with 5% fetal bovine serum provided as useful substrates for culture of SDCs, and fibroblast growth factor (FGF) played a key role in colony formation. Colonies were positive for alkaline phosphatase and anti-PGP9.5 staining. The early spermatogonia and stem cell markers such as octamer binding protein 4 (Oct4), Nanog homeobox (Nanog), promyelocytic leukemia zinc finger (PLZF), PGP9.5, and GDNF family receptor alpha-1 (GFRα-1) were expressed in the colonies at higher levels than in the testis tissue.

Conclusions

Testes of the 2-month-old beagles had abundant single and paired spermatogonia, which can be used for derivation of SDCs, and FGF was important for colony formation.     

Influence of altered geometry and material properties on tissue stress distribution under load in tendinopathic Achilles tendons – A subject-specific finite element analysis

Achilles tendon material properties and geometry are altered in Achilles tendinopathy. The purpose of this study was to determine the relative contributions of altered material properties and geometry to free Achilles tendon stress distribution during a sub-maximal contraction in tendinopathic relative to healthy tendons. Tendinopathic (n = 8) and healthy tendons (n = 8) were imaged at rest and during a sub-maximal voluntary isometric contraction using three-dimensional freehand ultrasound. Images were manually segmented and used to create subject-specific finite element models. The resting cross-sectional area of the free tendon was on average 31% greater for the tendinopathic compared to healthy tendons. Material properties for each tendon were determined using a numerical parameter optimisation approach that minimised the difference in experimentally measured longitudinal strain and the strain predicted by the finite element model under submaximal loading conditions for each tendon. The mean Young’s modulus for tendinopathic tendons was 53% lower than the corresponding control value. Finite element analyses revealed that tendinopathic tendons experience 24% less stress under the same submaximal external loading conditions compared to healthy tendons. The lower tendon stress in tendinopathy was due to a greater influence of tendon cross-sectional area, which alone reduced tendon stress by 30%, compared to a lower Young’s modulus, which alone increased tendon stress by 8%. These findings suggest that the greater tendon cross-sectional area observed in tendinopathy compensates for the substantially lower Young’s modulus, thereby protecting pathological tendon against excessive stress.     

Differences in glutamate receptors and inflammatory cell numbers are associated with the resolution of pain in human rotator cuff tendinopathy

IntroductionThe relationship between peripheral tissue characteristics and pain symptoms in soft tissue inflammation is poorly understood. The primary aim of this study was to determine immunohistochemical differences in tissue obtained from patients with persistent pain and patients who had become pain-free after surgical treatment for rotator cuff tendinopathy. The secondary aim was to investigate whether there would be differences in glutaminergic and inflammatory gene expression between disease-derived and healthy control cells in vitro.MethodsSupraspinatus tendon biopsies were obtained from nine patients with tendon pain before shoulder surgery and from nine further patients whose pain had resolved completely following shoulder surgery. Histological markers relating to the basic tendon characteristics, inflammation and glutaminergic signalling were quantified by immunohistochemical analysis. Gene expression of glutaminergic and inflammatory markers was determined in tenocyte explants derived from painful rotator cuff tendon tears in a separate cohort of patients and compared to that of explants from healthy control tendons. Dual labelling was performed to identify cell types expressing nociceptive neuromodulators.ResultsTendon samples from patients with persistent pain demonstrated increased levels of metabotropic glutamate receptor 2 (mGluR2), kainate receptor 1 (KA1), protein gene product 9.5 (PGP9.5), CD206 (macrophage marker) and CD45 (pan-leucocyte marker) versus pain-free controls (p <0.05). NMDAR1 co-localised with CD206-positive cells, whereas PGP9.5 and glutamate were predominantly expressed by resident tendon cells. These results were validated by in vitro increases in the expression of mGluR2, N-methyl-D-aspartate receptor (NMDAR1), KA1, CD45, CD206 and tumour necrosis factor alpha (TNF-α) genes (p <0.05) in disease-derived versus control cells.ConclusionsWe conclude that differences in glutamate receptors and inflammatory cell numbers are associated with the resolution of shoulder pain in rotator cuff tendinopathy, and that disease-derived cells exhibit a distinctly different neuro-inflammatory gene expression profile to healthy control cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0691-5) contains supplementary material, which is available to authorized users.     

The regulation of aggrecanase ADAMTS-4 expression in human Achilles tendon and tendon-derived cells

Several members of the ADAMTS (A Disintegrin And Metalloproteinase with ThromboSpondin motifs) family have been identified as aggrecanases, whose substrates include versican, the principal large proteoglycan in the tendon extracellular matrix. We have characterized the expression of ADAMTS-4 in human Achilles tendon and tendon-derived cells. ADAMTS-4 mRNA levels were higher in ruptured tendon compared with normal tendon or chronic painful tendinopathy. In tissue extracts probed by Western blotting, mature ADAMTS-4 (68 kDa) was detected only in ruptured tendons, while processed ADAMTS-4 (53 kDa) was detected also in chronic painful tendinopathy and in normal tendon. In cultured Achilles tendon cells, transforming growth factor-β (TGF-β) stimulated ADAMTS-4 mRNA expression (typically 20-fold after 24 h), while interleukin-1 induced a smaller, shorter-term stimulation which synergised markedly with that induced by TGF-β. Increased levels of immunoreactive proteins consistent with mature and processed forms of ADAMTS-4 were detected in TGF-β-stimulated cells. ADAMTS-4 mRNA was expressed at higher levels by tendon cells in collagen gels than in monolayer cultures. In contrast, the expression of ADAMTS-1 and -5 mRNA was lower in collagen gels compared with monolayers, and these mRNA showed smaller or opposite responses to growth factors and cytokines compared with that of ADAMTS-4 mRNA. We conclude that both ADAMTS-4 mRNA and ADAMTS-4 protein processing may be differentially regulated in normal and damaged tendons and that both the matrix environment and growth factors such as TGF-β are potentially important factors controlling ADAMTS aggrecanase activities in tendon pathology.     

Relationship between innervation zone width and mean muscle fiber conduction velocity during a sustained isometric contraction

Objectives:

To examine the relationship between the biceps brachii muscle innervation zone (IZ) width and the mean muscle fiber conduction velocity (MFCV) during a sustained isometric contraction.

Methods:

Fifteen healthy men performed a sustained isometric elbow flexion exercise at their 60% maximal voluntary contraction (MVC) until they could not maintain the target force. Mean MFCV was estimated through multichannel surface electromyographic recordings from a linear electrode array. Before exercise, IZ width was quantified. Separate non-parametric one-way analyses of variance (ANOVAs) were used to examine whether there was a difference in each mean MFCV variable among groups with different IZ width. In addition, separate bivariate correlations were also performed to examine the relationships between the IZ width and the mean MFCV variables during the fatiguing exercise.

Results:

There was a significant difference in the percent decline of mean MFCV (%ΔMFCV) among groups with different IZ width (χ² (3)=11.571, p=0.009). In addition, there was also a significant positive relationship between the IZ width and the %ΔMFCV (Kendall’s tau= 0.807; p<0.001).

Conclusions:

We believe that such relationship is likely influenced by both muscle fiber size and the muscle fiber type composition.     

Effect of vascular endothelial growth factor on rat Achilles tendon healing

This study evaluated the effect of exogenous vascular endothelial growth factor (VEGF) on tendon healing and regulation of other growth factors in a rat Achilles tendon model. Fifty Sprague-Dawley rats were used. In the experimental group, the left Achilles tendon was transected and repaired with the modified Kessler suture technique, and the right Achilles tendon was transected and repaired with resection of plantaris tendon. VEGF, 100 mul (50 mug/ml), was injected into each tendon at the repair site. The same surgical procedures were performed in the control group, with the same volume of saline injected into the repair sites. At intervals of 1, 2, and 4 weeks, the animals were killed and the tendons were harvested and evaluated for tensile strength (1, 2, and 4 weeks) and gene expression (postoperative day 4). At 1 week postoperatively, when plantaris tendon was preserved, the tensile strength of the repaired tendons with VEGF treatment (3.63 +/- 0.62 MPa) was significantly higher than the tensile strength of the repaired tendons with saline treatment (2.20 +/- 0.36 MPa). There was no difference in tensile strength between the two groups without the plantaris tendon support. At 2 weeks postoperatively, the tensile strength was 11.34 +/- 3.89 MPa in the group with VEGF treatment and plantaris tendon preservation, which was significantly higher than the tensile strength in the other groups. There was no significant difference in tensile strength among the groups at 4 weeks postoperatively. The gene expression showed that transforming growth factor-beta in the VEGF-treated tendon was up-regulated in the early stage of tendon healing, whereas expression of platelet-derived growth factor, basic fibroblast growth factor, and insulin-like growth factor-1 was not significantly different among the groups. In conclusion, administration of exogenous VEGF can significantly improve tensile strength early in the course of the rat Achilles tendon healing and was associated with increased expression of transforming growth factor-beta.     

A Pilot Study Evaluating the Effectiveness of Platelet-Rich Plasma Therapy for Treating Degenerative Tendinopathies: A Randomized Control Trial with Synchronous Observational Cohort

Objective

This pilot study aimed to inform future research evaluating the effectiveness of Platelet Rich Plasma (PRP) injection for tendinopathy.

Design

Randomized control trial (RCT) and synchronous observational cohort studies. For the RCT, consecutive consenting patients treated at an academic sports medicine clinic were randomly assigned to either a PRP or placebo control group.

Setting

The Glen Sather Sport Medicine Clinic, Edmonton, Canada.

Patients

The RCT included 9 participants with rotator cuff tendinopathy. The cohort study included 178 participants with a variety of tendinopathies.

Interventions

Patients receiving PRP were injected with 4 ml of platelets into the supraspinatus and/or infraspinatus, while patients in the placebo group were injected with 4ml of saline. All participants undertook a 3-month standardized, home-based, daily exercise program.

Main Outcome Measures

Participants in the RCT were re-evaluated 3, and 6 months post-injection. Change scores before and after injection on pain, disability and MRI-documented pathology outcomes were compared. In the cohort study, pain and disability were measured at 1, 2 and 3 months post-injection.

Results

For the RCT, 7 participants received PRP and 2 received placebo injections. Patients receiving PRP reported clinically important improvements in pain (>1.5/10 on VAS), disability (>15 point DASH change), and tendon pathology while those receiving placebo injections did not. In the observational cohort, statistically and clinically significant improvements in pain and disability were observed.

Conclusion

This pilot study provides information for planning future studies of PRP effectiveness. Preliminary results indicate intratendinous, ultrasound-guided PRP injection may lead to improvements in pain, function, and MRI-documented tendon pathology.

Trial Registration

Controlled-Trials.com ISRCTN68341698