Current pharmacological approaches to the treatment of tendinopathy.

INTRODUCTION: Tendinopathies are common in elite and recreational athletes: traditionally considered overuse injuries, they involve excessive tensile loading and subsequent breakdown of the loaded tendon. Many pharmacological treatments have been proposed for the management of tendinopathy, with no agreement regarding the overall best option available both for Achilles and patellar tendinopathy. AREAS COVERED: The present article reports the best scientific evidence regarding the efficacy and safety of different pharmacological treatments in different types of tendinopathy, focusing on Achilles and patellar tendinopathy, the conditions on which more studies have been published. EXPERT OPINION: No univocal evidence exists regarding the best non-operative management, which includes non-steroidal anti-inflammatory drugs, platelet-rich plasma, high volume image-guided injections, hyaluronic acid, and prolotherapy, for tendinopathy (in particular Achilles and patellar tendinopathies) as a suitable alternative to the commonly used eccentric loading rehabilitation regimen. It is unclear whether the combination of pharmacological substances with physical therapy would produce better results than physical therapy alone. There is an overall lack of published well-performed randomized controlled trials comparing the various options available for the management of tendinopathy, studying large cohorts of patients for adequately long follow-up periods and with well-validated standardized scores and scales.

Dual growth factor-immobilized asymmetrically porous membrane for bone-to-tendon interface regeneration on rat patellar tendon avulsion model.

Insufficient repair of the bone-to-tendon interface (BTI) with structural/compositional gradients has been a significant challenge in orthopedics. In this study, dual growth factor (platelet-derived growth factor-BB [PDGF-BB] and bone morphogenetic protein-2 [BMP-2])-immobilized polycaprolactone (PCL)/Pluronic F127 asymmetrically porous membrane was fabricated to estimate its feasibility as a potential strategy for effective regeneration of BTI injury. The growth factors immobilized (via heparin-intermediated interactions) on the membrane were continuously released for up to ∼80% of the initial loading amount after 5 weeks without a significant initial burst. From the in vivo animal study using a rat patellar tendon avulsion model, it was observed that the PDGF-BB/BMP-2-immobilized membrane accelerates the regeneration of the BTI injury, probably because of the continuous release of both growth factors (biological stimuli) and their complementary effect to create a multiphasic structure (bone, fibrocartilage, and tendon) like a native structure, as well as the role of the asymmetrically porous membrane as a physical barrier (nanopore side; prevention of fibrous tissue invasion into the defect site) and scaffold (micropore side; guidance for tissue regeneration). © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 115-125, 2018.

Proanthocyanidins Attenuation of H2O2-Induced Oxidative Damage in Tendon-Derived Stem Cells via Upregulating Nrf-2 Signaling Pathway.

Proanthocyanidins (PCs) have shown inhibition of oxidative damage by improving Nrf-2 expression in many tissues. However, the cytoprotective effects of PCs on H2O2-induced tendon damage have not been verified. The current study was aimed at assessing the cytoprotection of PCs on the oxidative cellular toxicity of tendon-derived stem cells (TDSCs) induced by H2O2. The TDSCs were isolated from patellar tendons of Sprague Dawley (SD) rats, and the cells after third passage were used for subsequent experiments. The isolated cells were identified by flow cytometry assay and multidifferentiation potential assay. Cell Counting Kit-8 assay was performed to examine cell viability. Real-Time PCR and Western Blot were employed to, respectively, assess the mRNA and protein expressions of Nrf-2, GCLM, NQO-1, and HO-1. PCs significantly improved the cell viability of TDSCs. Furthermore, H2O2 upregulated Nrf-2, GCLM, NQO-1, and HO-1 without significant difference, while the proteins expressions were increased with significant difference in PCs group and PCs + H2O2 cotreated group. All the findings indicated that PCs could protect against the oxidative damage induced by H2O2 in TDSCs, and the cytoprotective effects might be due to the ability of PCs to activate the expressions of GCLM, HO-1, and NQO-1 via upregulating Nrf-2 signaling pathway.

Peritendinous injection of platelet-rich plasma to treat tendinopathy: A retrospective review.

OBJECTIVE: The aim of this study was to determine factors associated with the likelihood of a better clinical outcome after the peritendinous injection of PRP for the treatment of chronic tendinopathy and identify whether PRP represents an effective treatment option for chronic tendinopathies. METHODS: The study included 214 patients (86 males and 128 females; mean age: 39.3 (18-75) years) who received PRP injections for tendinopathy refractory to conventional treatments. The mean duration of symptoms at the moment of the PRP treatment was 8.3 months. Primary outcome measurement was perceived improvement in symptoms for each anatomic compartment for upper and lower limbs at 6 months after treatment. Also, a visual analog scale (VAS) score (pain intensity on a 0-10 scale) was used for pain scoring questionnaire before treatment, 6 weeks and 6 months following the PRP injection(s). To identify factors associated with the likelihood of a better clinical outcome, patients were categorized on the basis of their perceived improvement in symptoms 6 months after the PRP injection(s)-that is, as lower (less than 50% global improvement) or higher (more than 50% global improvement). RESULTS: A visual analogue scale score and perceived improvement in symptoms were significantly lower after peritendinous injection in 6-week and 6-month follow-ups compared with the baseline (P < 0.001) except for peroneal and Achilles tendons. Overall, 83% of patients indicated moderate to complete improvement in symptoms. The most common injection sites were the lateral epicondyle, Achilles, and patellar tendons. Furthermore, 30% of patients received only 1 injection, 30% received 2 injections, and 40% received 3 or more injections. A total of 85% of patients were satisfied (more than 50% global improvement) with the procedure. In addition, upper limb tendons, increase in the age, and female gender were associated with a higher likelihood of perceived improvement in symptoms. CONCLUSIONS: In the present retrospective study assessing PRP injections in the treatment of chronic tendinopathy, a moderate improvement (>50%) in pain symptoms was observed in most of the patients. Our research found that results were most promising with patellar and lateral epicondylar tendinopathy in the short to medium term. Female patients, patients with upper extremity tendinopathy and older patients appeared to benefit more from PRP injection. LEVEL OF EVIDENCE: Level IV, Therapeutic study.

Erythropoietin stimulates patellar tendon healing in rats.

BACKGROUND: Erythropoietin (EPO), regulating erythropoiesis, is used to provide protective and regenerative activity in non-haematopoietic tissues. There is insufficient knowledge about the role of EPO activity in tendon healing. Therefore, we investigated the effect of EPO treatment on healing in rat patellar tendons. METHODS: One hundred and twenty-six, four-month-old male Sprague-Dawley rats were randomly assigned to three experimental groups: 1, no treatment; 2, treatment with isotonic saline (NaCl) and 3, treatment with EPO. Each group was randomly subdivided into two groups for sacrifice at three (1a, 2a, 3a) or six weeks (1b, 2b, 3b). Complete incision of the left patellar tendon from the distal patellar pole was performed. We applied body casts for 20 days after the incised edges of the patellar tendon were brought together with a surgical technique. Both legs were harvested and specimens from each group underwent histological, biomechanical, and protein mRNA expression analyses. RESULTS: There were statistically significant differences in the ultimate breaking force between the EPO group and others at both weeks three and six (p<0.05); significant differences in fibroblast proliferation, capillary vessel formation, and local inflammation were found between groups 1a and 3a, and 2a and 3a (p<0.05). There were statistical differences between 1a, 3a and 2a, 3a for Col III, TGF-ß1, and VEGF and between 1b, 3b and 2b, 3b for Col I, Col III, TGF-ß1, and VEGF mRNA expressions. CONCLUSION: EPO had an additive effect with surgery on the injured tendon healing process in rats compared to the control groups biomechanically, histopathologically and with tissue protein mRNA expression. CLINICAL RELEVANCE: This is the first experimental study to analyze the relationship between EPO treatment and the patellar tendon repair process by biomechanical, histopathological, and tendon tissue mRNA expression methodologies.

Cyclic mechanical stretching induces autophagic cell death in tenofibroblasts through activation of prostaglandin E2 production.

BACKGROUND/AIMS: Autophagic cell death has recently been implicated in the pathophysiology of tendinopathy. Prostaglandin E2 (PGE2), a known inflammatory mediator of tendinitis, inhibits tenofibroblast proliferation in vitro; however, the underlying mechanism is unclear. The present study investigated the relationship between PGE2 production and autophagic cell death in mechanically loaded human patellar tendon fibroblasts (HPTFs) in vitro. METHODS: Cultured HPTFs were subjected to exogenous PGE2 treatment or repetitive cyclic mechanical stretching. Cell death was determined by flow cytometry with acridine orange/ethidium bromide staining. Induction of autophagy was assessed by autophagy markers including the formation of autophagosomes and autolysosomes (by electron microscopy, AO staining, and formation of GPF-LC3-labeled vacuoles) and the expression of LC3-II and BECN1 (by western blot). Stretching-induced PGE2 release was determined by ELISA. RESULTS: Exogenous PGE2 significantly induced cell death and autophagy in HPTFs in a dose-dependent manner. Blocking autophagy using inhibitors 3-methyladenine and chloroquine, or small interfering RNAs against autophagy genes Becn-1 and Atg-5 prevented PGE2-induced cell death. Cyclic mechanical stretching at 8% and 12% magnitudes for 24 h significantly stimulated PGE2 release by HPTFs in a magnitude-dependent manner. In addition, mechanical stretching induced autophagy and cell death. Blocking PGE2 production using COX inhibitors indomethacin and celecoxib significantly reduced stretching-induced autophagy and cell death. CONCLUSION: Taken together, cyclic mechanical stretching induces autophagic cell death in tenofibroblasts through activation of PGE2 production.

The effects of substance p on tendinopathy are dose-dependent: an in vitro and in vivo model study.

OBJECTIVES: Substance P (SP) is known to be involved in neuropathic pain, chronic inflammation, and tendinopathy. The present study evaluated the effects of different doses of SP on tendon-derived stem cells (TDSCs) in vitro and tendons in vivo. METHODS: For the in vitro study, TDSCs cultured in growth medium with different concentrations of SP (negative control, 0.1 nM, and 1.0 nM). The effects of SP on TDSCs were examined with respect to their ability to proliferate and differentiate. For the in vivo study, we injected different doses of SP (saline control, 0.5 nmol, and 5.0 nmol) into rat patella tendons to investigate the effects of SP on tendons. RESULTS: Low and high doses SP significantly enhanced the proliferation ability of TDSCs. Low-dose of SP induced the expression of tenocyte-related genes; however, high-dose of SP induced the expression of non-tenocyte genes, which was evident by the high expression of PPARγ and collagen type II. In the in vivo study, only high-doses of SP (5.0 nmol) induced the tendinosis-like changes in the patella tendon injection model. Low doses of SP (0.5 nmol) enhanced the tenogenesis compared with saline injection and the high-dose SP group. CONCLUSIONS: SP enhances the proliferation of TDSCs in vitro and the effects of SP on tendinopathy are dose-dependent in vivo.

Hyaluronic acid injections protect patellar tendon from detraining-associated damage.

INTRODUCTION: Having previously demonstrated that detraining affects patellar tendon (PT) proteoglycan content and collagen fiber organization, we undertook the present study with two aims: to improve knowledge on the adaptation of PT and its enthesis to detraining from a histological and histomorphometric point of view, and to investigate the hypothesis that repeated peri-patellar injections of hyaluronic acid (HA) on detrained PT may reduce and limit detrained associated-damage. METHODS: Twenty-four male Sprague-Dawley rats were divided into 3 groups: Untrained (n=6), Trained (n=6) (10 wks-treadmill) and Detrained (n=12). In the detrained rats, the left tendon was untreated while the right tendon received repeated peri-patellar injections of either HA or saline (NaCl). Structure and morphology of PTs (modified Movin score, tear density, collagen type I and III) and enthesis (cell morphology, chondrocyte cluster formation, tidemark integrity, matrix staining and vascularization) were evaluated. RESULTS: The left PT and enthesis of the Detrained groups showed altered structure and morphology with the highest Movin score values, the highest percentage of collagen III and the lowest of collagen I; the lowest score values were observed in the Trained and Detrained-HA groups. Detrained-NaCl PTs showed the highest collagen III and the lowest collagen I values with respect to Detrained-HA PTs. CONCLUSION: This study strengthens previously published data showing the alteration in tendon and enthesis morphology due to discontinuation of training, and provides new data showing that treatment with HA is effective in the maintenance of the structural properties of PT and enthesis in Detrained rats. Such beneficial effects could play a significant role in the management of conservative and rehabilitation strategies in athletes that change type, intensity and duration of training.

Sclerosing injections and ultrasound-guided arthroscopic shaving for patellar tendinopathy: good clinical results and decreased tendon thickness after surgery-a medium-term follow-up study.

PURPOSE: Treatment of patellar tendinopathy/jumper's knee with ultrasound-guided sclerosing injections or ultrasound-guided arthroscopic shaving has shown good clinical short-term results. Former studies indicate that the tendon thickness and structure stays unaffected after successful treatment. The aim of this study was to evaluate the sonographic findings and clinical outcome 3-5 years after treatment of patellar tendinopathy with ultrasound-guided sclerosing injections or arthroscopic shaving. METHODS: Fifty-seven patellar tendons (43 patients) with chronic patellar tendinopathy were evaluated, with ultrasound, colour Doppler (CD) and visual analogue scale (VAS) for pain and satisfaction with treatment, 3-5 years after treatment. Functional status was evaluated with a single question-"Back in full loading activity?" yes or no. RESULTS: At endpoint (mean 46 months), there was a significant decrease in anteroposterior thickness of the proximal patellar tendon in patients treated with ultrasound-guided arthroscopic shaving but not after sclerosing injections. Tendon structure had improved, and CD local blood flow had diminished significantly in both groups. There were good clinical results with a significant decrease in VAS for pain after sclerosing injections (VAS 64 ± 18 â†’ 17 ± 23) with 74 % satisfied patients and also after arthroscopic shaving (VAS 77 ± 16 â†’ 13 ± 23) with 80 % satisfied patients. There were no significant differences in VAS between groups. A significant correlation between low local blood flow and high patient satisfaction was found. CONCLUSIONS: Tendon thickness decreased over time after ultrasound-guided arthroscopic shaving, and tendon structure and local blood flow decreased after both treatments. There were good, and similar, clinical results with both methods. LEVEL OF EVIDENCE: III.

Differences in anterior cruciate ligament elasticity and force for knee flexion in women: oral contraceptive users versus non-oral contraceptive users.

Eighty-two percent of sexually active women aged 15-44 have used oral contraceptive pills (OCP) in the United States. The OCP, an exogenous source of synthetic forms of steroid hormones, prevents ovulation. Hormone changes during the menstrual cycle (MC) are believed to have an impact on anterior cruciate ligament (ACL) laxity due to estrogen. Because the estrogen receptor ß resides on human connective tissue, OCP may have potential impact on tendon and ligament synthesis, structure, and biomechanical properties. Temperature has also been known to have an effect on tissue elasticity. Therefore, the purpose of this study was to investigate the differences in ACL elasticity, force to flex the knee (FFK), and knee flexion-extension hysteresis (KFEH) between OCP users and non-OCP users. To investigate these changes, two different knee temperatures were measured. Nineteen young females were divided into two groups: OCP users and non-OCP users. Blood for estradiol serum concentration (E2) was taken before beginning the tests. ACL elasticity, FFK, and KFEH were assessed both at ambient temperature (22 °C) and after 38 °C warming of the leg to stabilize tissue temperature. Assessments were performed four times during the MC. Throughout the MC, ACL elasticity, FFK, and KFEH fluctuated in non-OCP users, but not in OCP users. At ambient temperature, ACL elasticity was significantly lower and FFK and KFEH were significantly higher in OCP users than non-OCP users (p < 0.05). But, no significant differences in FFK and KFEH between the two groups were found after warming to 38 °C.

Effect of androgenic-anabolic steroids and heavy strength training on patellar tendon morphological and mechanical properties.

Combined androgenic-anabolic steroids (AAS) and overloading affects tendon collagen metabolism and ultrastructure and is often associated with a higher risk of injury. The aim of this prospective study was to investigate whether such effects would be reflected in the patellar tendon properties of individuals with a history of long-term resistance training and AAS abuse (RTS group), compared with trained (RT) and untrained (CTRL) nonsteroids users. Tendon cross-sectional area (CSA), stiffness, Young's modulus, and toe limit strain were measured in vivo, from synchronized ultrasonography and dynamometry data. The patellar tendon of RT and RTS subjects was much stiffer and larger than in the CTRL group. However, stiffness and modulus were higher in the RTS group (26%, P < 0.05 and 30%, P < 0.01, respectively) than in the RT group. Conversely, tendon CSA was 15% (P < 0.05) larger in the RT group than in RTS, although differences disappeared when this variable was normalized to quadriceps maximal isometric torque. Yet maximal tendon stress was higher in RTS than in RT (15%, P < 0.05), without any statistical difference in maximal strain and toe limit strain between groups. The present lack of difference in toe limit strain does not substantiate the hypothesis of changes in collagen crimp pattern associated with AAS abuse. However, these findings indicate that tendon adaptations from years of heavy resistance training are different in AAS users, suggesting differences in collagen remodeling. Some of these adaptations (e.g., higher stress) could be linked to a higher risk of tendon injury.

Impact of oral contraceptive use and menstrual phases on patellar tendon morphology, biochemical composition, and biomechanical properties in female athletes.

Sex differences exist with regards to ligament and tendon injuries. Lower collagen synthesis has been observed in exercising women vs. men, and in users of oral contraceptives (OC) vs. nonusers, but it is unknown if OC will influence tendon biomechanics of women undergoing regular training. Thirty female athletes (handball players, 18-30 yr) were recruited: 15 long-term users of OC (7.0 ± 0.6 yr) and 15 nonusers (>5 yr). Synchronized values of patellar tendon elongation (obtained by ultrasonography) and tendon force were sampled during ramped isometric knee extensor maximum voluntary contraction to estimate mechanical tendon properties. Furthermore, tendon cross-sectional area and length were measured from MRI images, and tendon biopsies were obtained for analysis of tendon fibril characteristics and collagen cross-linking. Overall, no difference in tendon biomechanical properties, tendon fibril characteristics, or collagen cross-linking was observed between the OC users and nonusers, or between the different phases of the menstrual cycle. In athletes, tendon cross-sectional area in the preferred jumping leg tended to be larger than that in the contralateral leg (P = 0.09), and a greater absolute (P = 0.01) and normalized tendon stiffness (P = 0.02), as well as a lower strain (P = 0.04), were observed in the jumping leg compared with the contralateral leg. The results indicate that long-term OC use or menstrual phases does not influence structure or mechanical properties of the patellar tendon in female team handball athletes.

Local administration of insulin-like growth factor-I (IGF-I) stimulates tendon collagen synthesis in humans.

Collagen is the predominant structural protein in tendons and ligaments, and can be controlled by hormonal changes. In animals, injections of insulin-like growth factor I (IGF-I) has been shown to increase collagen synthesis in tendons and ligaments and to improve structural tissue healing, but the effect of local IGF-I administration on tendon collagen synthesis in human has not been studied. The purpose of this study was to study whether local injections of IGF-I would have a stimulating effect on tendon collagen synthesis. Twelve healthy nonsmoking men [age 62 ± 1 years (mean ± SEM), BMI 27 ± 1] participated. Two injections of either human recombinant IGF-I (0.1 mL Increlex©) or saline (control) into each patellar tendon were performed 24-h apart, respectively. Tendon collagen fractional synthesis rate (FSR) was measured by stable isotope technique in the hours after the second injection. Simultaneously, interstitial peritendinous (IGF-I) and [procollagen type I N-terminal propeptide (PINP)], as a marker for type I collagen synthesis, were determined by microdialysis technique. Tendon collagen FSR and PINP were significantly higher in the IGF-I leg compared with the control leg (P < 0.05). In conclusion, local IGF-I administration can directly enhance tendon collagen synthesis both within and around the human tendon tissue.

Differential cross-linking and radio-protective effects of genipin on mature bovine and human patella tendons.

Gamma irradiation is a proven sterilization method, but is not widely used on allografts for anterior cruciate ligament reconstruction (e.g., patella tendon) due to radiation-induced decreases in mechanical strength. Addressing this drawback would improve the safety and supply of allografts to meet current and future demand. It was hypothesized that genipin-induced collagen cross-linking would increase the tensile modulus of patella tendon tissue such that 5 MRad gamma irradiation would not reduce the tissue mechanical strength below the original untreated values. Optimized genipin treatment increased the tensile modulus of bovine tendons by ~2.4-fold. After irradiation, genipin treated tissue did not significantly differ from native tissue, proving the hypothesis. Optimized genipin treatment of human tendons increased the tensile modulus by ~1.3-fold. After irradiation, both control and genipin-treated tissues possessed ~50-60% of their native tendon modulus, disproving the hypothesis. These results highlight possible age- and species- dependent effects of genipin cross-linking on tendon tissue. Cross-linking of human allografts may be beneficial only in younger donor tissues. Future research is warranted to better understand the mechanisms and applications of collagen cross-linking for clinical use.

The effects of dexamethasone on human patellar tendon stem cells: implications for dexamethasone treatment of tendon injury.

Injection of Dexamethasone (Dex) is commonly used in clinics to treat tendon injury such as tendinopathy because of its anti-inflammatory capabilities. However, serious adverse effects have been reported as a result of Dex treatment, such as impaired tendon healing and tendon rupture. Using both in vitro and in vivo approaches, this study was to determine the effects of Dex treatment on the proliferation and differentiation of human tendon stem cells (hTSCs), which can directly impact tendon healing. We found that Dex treatment stimulated cell proliferation at lower concentrations (<1,000 nM), whereas a high concentration (1,000 nM) decreased cell proliferation. Moreover, at all concentrations used (5, 10, 100, and 1,000 nM), Dex treatment induced non-tenocyte differentiation of hTSCs, as evidenced by a change in cell shape, a nearly complete suppression of collagen type I expression, and an upregulation of non-tenocyte related genes (PPARγ and Sox-9), which was especially evident when higher concentrations (>10 nM) of Dex were used. Implantation of Dex-treated hTSCs for a short time (3 weeks) resulted in the extensive formation of fatty tissues, cartilage-like tissues, and bony tissues. These findings suggest that Dex treatment in clinics may cause a paradoxical effect on the injured tendons it is supposed to treat: by inducing non-tenocyte differentiation of hTSCs, Dex treatment depletes the stem cell pool and leads to the formation of non-tendinous tissues (e.g., fatty and cartilage-like tissues), which make tendon susceptible to rupture.

Chlorhexidine gluconate cleansing has no effect on the structural properties of human patellar tendon allografts.

PURPOSE: If an anterior cruciate ligament graft somehow becomes contaminated intraoperatively, soaking it in 4% chlorhexidine gluconate has been shown to be the most popular and efficacious method for sterilization before implantation. The purpose of this study was to evaluate the effects of a chlorhexidine soak on the structural properties of human patellar tendon allografts. METHODS: Sixteen human patellar tendon allografts were randomly split into 2 groups of 8. Grafts in 1 group were soaked in 4% chlorhexidine gluconate for 30 minutes, and the other grafts were kept moist in normal saline-soaked gauze. Data on preload width, preload thickness, elongation, ultimate tensile load, and stiffness were obtained through measurement and mechanical testing of the grafts. RESULTS: Graft donor ages ranged from 29 to 43 years. There was no difference in the mean values of graft dimensions of the chlorhexidine-exposed group versus the normal saline-exposed group before mechanical testing (width of 9.48 mm v 9.56 mm, P = .89; thickness of 4.01 mm v 4.57 mm, P = .34). Graft elongation was not statistically different between the groups (2.52 mm v 1.43 mm, P = .27). No statistically significant difference was noted between the ultimate tensile load (2,219 N v 1,878 N, P = .36) or stiffness (274.3 N/mm v 297.0 N/mm, P = .63) of the grafts in both groups. CONCLUSIONS: Structural properties of human patellar tendon allografts are not significantly affected by soaking in 4% chlorhexidine gluconate for 30 minutes. CLINICAL RELEVANCE: Surgeons wishing to treat an inadvertently contaminated graft intraoperatively with 4% chlorhexidine may do so without concern that such treatment will impact graft strength.

Local administration of growth hormone stimulates tendon collagen synthesis in elderly men.

Tendon collagen content and circulating growth hormone (GH) are reduced in elderly. In a placebo-controlled, double-blinded study, we examined if local injections of rhGH enhance collagen synthesis in healthy elderly men (61 ± 1 yr). Two injections of rhGH or saline (control) were injected into each of the patient's patellar tendons, respectively. Subsequently, tendon collagen fractional synthesis rate (FSR) and an indirect marker of type I collagen synthesis (PINP) were measured. Within the first 6 h after the last injections, a tendency towards a higher tendon collagen FSR was observed in 10 out of 12 subjects (P = 0.08). Similarly, PINP was higher 3-4 h after the last GH injection (P = 0.05). Serum IGF-I did not change from baseline, whereas peritendinous bioactive IGF-I was higher in the GH leg vs. control (P = 0.05). In conclusion, local injections of rhGH increase tendon collagen synthesis in humans, either directly or indirectly by increasing local bioactive IGF-I.

Effects of transdermal estrogen on collagen turnover at rest and in response to exercise in postmenopausal women.

Menopause is associated with loss of collagen content in the skin and tendon as well as accumulation of noncontractile tissue in skeletal muscle. The relative role of hormones and physical activity on these changes is not known. Accordingly, in a randomized, controlled, crossover study we investigated effects of transdermal estrogen replacement therapy (ERT) on type I collagen synthesis in tendon and skeletal muscle in 11 postmenopausal women. Patches with estrogen (Evorel) were placed on the skin above the patellar tendons and compared with no patch (control period). On day 2 all subjects performed one-legged exercise, and thereafter the exercised leg (EX leg) was compared with the nonexercised leg (Rest leg). Microdialysis catheters were placed in front of the patellar tendons and in the vastus lateralis muscle of both legs at days 3 and 5. The collected dialysate was analyzed for procollagen type I NH(2)-terminal propeptide (PINP), insulin-like growth factor I (IGF-I), and interleukin-6 (IL-6). Neither loading (Rest leg vs. EX leg) nor treatment (control vs. ERT) influenced peritendinous PINP, whereas combined exercise and ERT enhanced muscle PINP after 72 h (interaction between loading and treatment P = 0.008). In neither skeletal muscle nor peritendinous fluid were IGF-I and IL-6 influenced by treatment or exercise. In conclusion, ERT was associated with enhanced synthesis of type I collagen in the skeletal muscle in response to acute exercise. In perspective, this indicates that the availability of estrogen in postmenopausal women is important for repair of muscle damage or remodeling of the connective tissue within the skeletal muscle after exercise.

Effect of prolotherapy on cellular proliferation and collagen deposition in MC3T3-E1 and patellar tendon fibroblast populations.

Proliferative therapy, or prolotherapy, is a treatment for damaged connective tissues involving the injection of a solution (proliferant) which causes local cell death and triggers the body's wound healing cascade. Physicians vary in their use of this technique; it is employed for ligaments but has also been investigated for tissues such as cartilage. Physicians also vary in treatment regiments using different dosses of the proliferant. This study evaluates several proliferant dosages develop an optimal dosage that maximizes cell and collagen regeneration. This study also looks at cell and collagen regeneration in response to proliferant exposure outside of the healing cascade. MC3T3-E1 cells and patellar tendon fibroblasts were exposed to various amounts of the proliferant P2G and monitored over several weeks. The results showed an inverse relationship between proliferant concentration and cell viability and collagen production in MC3T3-E1 cells. Following exposure, cell populations experienced an initial decrease in cell number followed by increased proliferation. Trichrome staining over 4 weeks showed an increase in collagen production after proliferant exposure. However the cell numbers and amounts of collagen from the treated groups never surpassed those of the untreated groups, although collagen production was comparable in fibroblasts. The results of this basic study show that there is an effective proliferant dosage and point to a local response to the proliferant that increases cell proliferation and collagen production separate from the wound healing cascade. This local response may not be adequate for complete healing and assistance from the body's healing cascade may be required.