Use of ultrasound-targeted microbubble destruction to transfect IGF-1 cDNA to enhance the regeneration of rat wounded Achilles tendon in vivo

Growth factors in the treatment of Achilles tendon injury

Achilles tendon (AT) injury is one of the most common tendon injuries, especially in athletes, the elderly, and working-age people. In AT injury, the biomechanical properties of the tendon are severely affected, leading to abnormal function. In recent years, many efforts have been underway to develop effective treatments for AT injuries to enable patients to return to sports faster. For instance, several new techniques for tissue-engineered biological augmentation for tendon healing, growth factors (GFs), gene therapy, and mesenchymal stem cells were introduced. Increasing evidence has suggested that GFs can reduce inflammation, promote extracellular matrix production, and accelerate AT repair. In this review, we highlighted some recent investigations regarding the role of GFs, such as transforming GF-β(TGF-β), bone morphogenetic proteins (BMP), fibroblast GF (FGF), vascular endothelial GF (VEGF), platelet-derived GF (PDGF), and insulin-like GF (IGF), in tendon healing. In addition, we summarized the clinical trials and animal experiments on the efficacy of GFs in AT repair. We also highlighted the advantages and disadvantages of the different isoforms of TGF-β and BMPs, including GFs combined with stem cells, scaffolds, or other GFs. The strategies discussed in this review are currently in the early stages of development. It is noteworthy that although these emerging technologies may potentially develop into substantial clinical treatment options for AT injury, definitive conclusions on the use of these techniques for routine management of tendon ailments could not be drawn due to the lack of data.

An Extracellular Vesicle-Cloaked Multifaceted Biocatalyst for Ultrasound-Augmented Tendon Matrix Reconstruction and Immune Microenvironment Regulation

The healing of tendon injury is often hindered by peritendinous adhesion and poor regeneration caused by the accumulation of reactive oxygen species (ROS), development of inflammatory responses, and the deposition of type-III collagen. Herein, an extracellular vesicles (EVs)-cloaked enzymatic nanohybrid (ENEV) was constructed to serve as a multifaceted biocatalyst for ultrasound (US)-augmented tendon matrix reconstruction and immune microenvironment regulation. The ENEV-based biocatalyst exhibits integrated merits for treating tendon injury, including the efficient catalase-mimetic scavenging of ROS in the injured tissue, sustainable release of Zn2+ ions, cellular uptake augmented by US, and immunoregulation induced by EVs. Our study suggests that ENEVs can promote tenocyte proliferation and type-I collagen synthesis at an early stage by protecting tenocytes from ROS attack. The ENEVs also prompted efficient immune regulation, as the polarization of macrophages (Mφ) was reversed from M1φ to M2φ. In a rat Achilles tendon defect model, the ENEVs combined with US treatment significantly promoted functional recovery and matrix reconstruction, restored tendon morphology, suppressed intratendinous scarring, and inhibited peritendinous adhesion. Overall, this study offers an efficient nanomedicine for US-augmented tendon regeneration with improved healing outcomes and provides an alternative strategy to design multifaceted artificial biocatalysts for synergetic tissue regenerative therapies.

Tendinopathy and tendon material response to load: What we can learn from small animal studies

Tendinopathy is a debilitating disease that causes as much as 30% of all musculoskeletal consultations. Existing treatments for tendinopathy have variable efficacy, possibly due to incomplete characterization of the underlying pathophysiology. Mechanical load can have both beneficial and detrimental effects on tendon, as the overall tendon response depends on the degree, frequency, timing, and magnitude of the load. The clinical continuum model of tendinopathy offers insight into the late stages of tendinopathy, but it does not capture the subclinical tendinopathic changes that begin before pain or loss of function. Small animal models that use high tendon loading to mimic human tendinopathy may be able to fill this knowledge gap. The goal of this review is to summarize the insights from in-vivo animal studies of mechanically-induced tendinopathy and higher loading regimens into the mechanical, microstructural, and biological features that help characterize the continuum between normal tendon and tendinopathy. STATEMENT OF SIGNIFICANCE: This review summarizes the insights gained from in-vivo animal studies of mechanically-induced tendinopathy by evaluating the effect high loading regimens have on the mechanical, structural, and biological features of tendinopathy. A better understanding of the interplay between these realms could lead to improved patient management, especially in the presence of painful tendon.

Transfection of TGF-β shRNA by Using Ultrasound-targeted Microbubble Destruction to Inhibit the Early Adhesion Repair of Rats Wounded Achilles Tendon In vitro and In vivo

BACKGROUND

Tendon injury is a major orthopedic disorder. Ultrasound-targeted microbubble destruction (UTMD) provides a promising method for gene transfection, which can be used for the treatment of injured tendons.

OBJECTIVE

The purpose of this study was to investigate the optimal transforming growth factor beta (TGF-β) short hairpin RNA (shRNA) sequence and transfection conditions using UTMD in vitro and to identify its ability for inhibiting the early adhesion repair of rats wounded achilles tendons in vivo.

METHODS

The optimal sequence was selected analyzing under a fluorescence microscope and quantitative real-time reverse transcription polymerase chain reaction in vitro. In vivo, 40 rats with wounded Achilles tendons were divided into five groups: (1) control group, (2) plasmid group (3) plasmid + ultrasound group, (4) plasmid + microbubble group, (5) plasmid + microbubble + ultrasound group, and were euthanized at 14 days post treatment. TGF-β expression was evaluated using adhesion scores and pathological examinations.

RESULTS

The optimal condition for UTMD delivery in vitro was 1W/cm2 of output intensity and a 30% duty cycle with 60 s irradiation time (P < 0.05). The transfection efficiency of the plasmid in group 5 was higher than that in other groups (P < 0.05). Moreover, the lowest adhesion index score and the least expression of TGF-β were shown in group 5 (P < 0.05). When compared with the other groups, group 5 had a milder inflammatory reaction.

CONCLUSION

The results suggested that UTMD delivery of TGF-β shRNA offers a promising treatment approach for a tendon injury in vivo.

Injectable hydrogels for tendon and ligament tissue engineering

The problem of tendon and ligament (T/L) regeneration in musculoskeletal diseases has long constituted a major challenge. In situ injection of formable biodegradable hydrogels, however, has been demonstrated to treat T/L injury and reduce patient suffering in a minimally invasive manner. An injectable hydrogel is more suitable than other biological materials due to the special physiological structure of T/L. Most other materials utilized to repair T/L are cell-based, growth factor-based materials, with few material properties. In addition, the mechanical property of the gel cannot reach the normal T/L level. This review summarizes advances in natural and synthetic polymeric injectable hydrogels for tissue engineering in T/L and presents prospects for injectable and biodegradable hydrogels for its treatment. In future T/L applications, it is necessary develop an injectable hydrogel with mechanics, tissue damage-specific binding, and disease response. Simultaneously, the advantages of various biological materials must be combined in order to achieve personalized precision therapy.

Evaluation of a new collagen-based medical device (ElastiCo®) for the treatment of acute Achilles tendon injury and prevention of peritendinous adhesions: An in vitro biocompatibility and in vivo investigation

Tendon healing still represents a challenge for clinicians because it is slow and incomplete. The most injured is the Achilles tendon, and surgery is the therapeutic strategy often adopted because it provides a quicker functional recovery. Peritendinous adhesions are the main complication of surgery with hyperplasia and chemotaxis of fibroblasts. A biomaterial that blocks fibroblast migration, without interfering with the passage of cytokines and growth factors, might be useful. The present study evaluated the biocompatibility of a new Type I collagen-based scaffold (ElastiCo®) and its ability to promote Achilles tendon healing, inhibiting adhesion formation. After verifying in vitro biocompatibility, physical, and mechanical properties of the scaffold, an in vivo study was performed in 28 rats, operated to induce an acute lesion in both Achilles tendons. One tendon was treated with the suture only and the contralateral one with suture wrapped with ElastiCo® film. After 8 and 16 weeks, it was observed that ElastiCo® reduced internal and external peritendinous adhesions and Collagen III content and increased Collagen I. Elastic modulus increased with both treatments over time. Current results highlighted the clinical translationality of ElastiCo® that could improve the quality of life in patients affected by Achilles tendon lesions surgically treated.

CTGF induces tenogenic differentiation and proliferation of adipose-derived stromal cells

Intrasynovial tendons are paucicellular and hypovascular, resulting in a poor response to injury. Surgical repair of ruptured or lacerated tendons often lead to complications such as adhesions, repair site gapping, and repair site rupture. Adipose-derived stem cells (ASCs) have shown promise for enhancing tendon repair, as they have the capacity to differentiate into tendon fibroblasts and augment the healing response. Furthermore, connective tissue growth factor (CTGF) has been shown to promote tendon regeneration via the stimulation of endogenous tendon stem cells. Here, we evaluated the potential of CTGF to promote tenogenic differentiation of ASCs in vitro. Gene and protein expression, cell proliferation, and FAK and ERK1/2 signaling were assessed. CTGF increased tenogenic genes in mouse ASCs in a dose- and time-dependent manner. Western blot and immunostaining analyses demonstrated increases in tenogenic protein expression in CTGF-treated ASCs at all timepoints studied. CTGF increased ASC proliferation in a dose-dependent manner. CTGF induced phosphorylation of ERK1/2 within 5 min and FAK within 15 min; both signals persisted for 120 min. Blocking FAK and ERK1/2 pathways by selective inhibitors SCH772984 and PF573228, respectively, attenuated the CTGF-induced tenogenic differentiation and proliferation of ASCs. These results suggest that CTGF induces tenogenic differentiation of ASCs via the FAK and ERK1/2 pathway. Statement of clinical significance: Although prior research has led to advances in tendon operative techniques and rehabilitation methods, clinical outcomes after tendon repair remain variable, with high rates of repair site gapping or rupture. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Experimental study of TNF-α receptor gene transfection by ultrasound-targeted microbubble destruction to treat collagen-induced arthritis in rats in vivo

Ultrasound-targeted microbubble destruction (UTMD) is a novel method for gene transfection. The aim of the present study was to identify the most suitable method of tumor necrosis factor (TNF)-α receptor (TNFR) gene transfection using UTMD for systemically treating a rat model of collagen-induced arthritis (CIA). Plasmids encoding the TNFR and enhanced green fluorescent protein (EGFP) with or without microbubbles were locally injected into the skeletal muscle and synovial membrane of CIA rats. The rats were divided into the following 6 groups: i) Group 1, plasmid + microbubble + ultrasound (muscle group); ii) group 2, plasmid + microbubble + ultrasound (joint group); iii) group 3, plasmid + ultrasound; iv) group 4, plasmid + microbubble; v) group 5, plasmid only and; vi) group 6, untreated controls. Rats were sacrificed at 2, 4 and 8 weeks of treatment. The transfection efficiency of the plasmids in the muscle or synovium was observed by fluorescence microscopy. Arthritis scores were calculated and serum levels of TNF-α were measured prior to and following treatment. Bilateral ankle joints were obtained and stained to observe synovial inflammation and the expression of TNF-α. EGFP expression was detected in all treated groups at each time point, and the fluorescence intensity of groups 1 and 2 was significantly greater than that of the other groups (P<0.05). For groups 1 and 2, the reductions in joint scores and serum levels of TNF-α were significant compared with the other groups (P<0.05). The number of synovial inflammatory cells and the synovial expression of TNF-α presented similar results among all experimental groups and no significant difference was observed between groups 1 and 2. Therefore, the results of the present study suggest that UTMD significantly enhanced the efficiency of TNFR gene transfection in the muscle and inflamed synovium of rats with. Regardless of whether the transfected TNFR gene was injected into the muscle or joint, it was continuously expressed in the rats for at least 8 weeks, which may improve arthritic symptoms and reduce the levels of inflammatory factors in the synovial tissues and peripheral blood.

Ultrasound-Targeted Microbubble Destruction Delivery of Insulin-Like Growth Factor 1 cDNA and Transforming Growth Factor Beta Short Hairpin RNA Enhances Tendon Regeneration and Inhibits Scar Formation In Vivo

Ultrasound-targeted microbubble destruction (UTMD), which has been successfully used for the treatment of many diseases, offers a promising noninvasive approach for target-specific gene delivery. This study investigated the UTMD delivery of insulin-like growth factor 1 (IGF-1) cDNA and transforming growth factor beta (TGF-β) short hairpin RNA for Achilles tendon injury in rats. Briefly, 168 rats with an injured Achilles tendon were randomly divided into seven groups: (1) IGF-1 + UTMD, (2) TGF-β + UTMD, (3) IGF-1 + TGF-β + UTMD, (4) control, (5) IGF-1, (6) TGF-β, and (7) IGF-1 + TGF-β. At 2, 4, 8, and 12 weeks post treatment, six rats from each group were euthanized. IGF-1 expression and TGF-β expression were evaluated using an adhesion index score, pathological examination, quantitative real-time reverse transcription polymerase chain reaction, Western blotting, and biomechanical measurement. The lowest adhesion index score, the lightest inflammation, the highest 4,6-diamidino-2-phenylindole nuclear counter signals, the highest IGF-1 expression, and the lowest TGF-β expression were observed in group 3 (p < 0.05). Furthermore, higher expression of IGF-1 mRNA was observed in groups 1 and 3, while lower expression of TGF-β mRNA was observed in groups 2 and 3 (p < 0.05). The UTMD groups showed a higher transfection efficiency than the groups without UTMD. Downregulation of type III collagen and upregulation of type I collagen were observed in groups 1-3. Moreover, during weeks 4, 8, and 12, greater maximum load and tensile stress were observed in group 3 compared to the other groups (p < 0.05), while the highest tendon stiffness was observed in week 12 (p < 0.05). To conclude, the results suggest that UTMD delivery of IGF-1 and TGF-β offers a promising treatment approach for tendon injury in vivo.

Tough Composite Hydrogels with High Loading and Local Release of Biological Drugs

Hydrogels are under active development for controlled drug delivery, but their clinical translation is limited by low drug loading capacity, deficiencies in mechanical toughness and storage stability, and poor control over the drug release that often results in burst release and short release duration. This work reports a design of composite clay hydrogels, which simultaneously achieve a spectrum of mechanical, storage, and drug loading/releasing properties to address the critical needs from translational perspectives. The clay nanoparticles provide large surface areas to adsorb biological drugs, and assemble into microparticles that are physically trapped within and toughen hydrogel networks. The composite hydrogels demonstrate feasibility of storage, and extended release of large quantities of an insulin-like growth factor-1 mimetic protein (8 mg mL-1 ) over four weeks. The release rate is primarily governed by ionic exchange and can be upregulated by low pH, which is typical for injured tissues. A rodent model of Achilles tendon injury is used to demonstrate that the composite hydrogels allow for highly extended and localized release of biological drugs in vivo, while demonstrating biodegradation and biocompatibility. These attributes make the composite hydrogel a promising system for drug delivery and regenerative medicine.

Effect of Different Exercise Intensities on the Myotendinous Junction Plasticity

Myotendinous junctions (MTJs) are anatomical regions specialized in transmission of contractile strength from muscle to tendon and, for this reason, a common site where acute injuries occur during sport activities. In this work we investigated the influence of exercise intensity on MTJ plasticity, as well as on the expression of insulin-like growth factor 1 (IGF-1) and transforming growth factor beta (TGF-β) and their receptors in muscle and tendon. Three groups of rats were analyzed: control (CTRL), slow-runner (RUN-S) and fast-runner (RUN-F) trained using a treadmill. Ultrastructural and morphometric analyses of distal MTJs from extensor digitorum longus muscles have been performed. Contractile strength and hypertrophy were investigated by using in vivo tension recordings and muscle cross-sectional area (CSA) analysis, respectively. mRNA levels of PGC-1α, vinculin, IGF-1Ea and TGF-β have been quantified in muscle belly, while IGF-1Ea, TGF-β and their receptors in tendon. Morphometry revealed an increased MTJ complexity and interaction surface between tissues in trained rats according to training intensity. CSA analysis excluded hypertrophy among groups, while muscle strength was found significantly enhanced in exercised rats in comparison to controls. In muscle tissue, we highlighted an increased mRNA expression of PGC-1α and vinculin in both trained conditions and of TGF-β in RUN-F. In tendon, we mainly noted an enhancement of TGF-β mRNA expression only in RUN-F group and a raise of Betaglycan tendon receptor mRNA levels proportional to exercise intensity. In conclusion, MTJ plasticity appears to be related to exercise intensity and molecular analysis suggests a major role played by TGF-β.

Basic FGF or VEGF gene therapy corrects insufficiency in the intrinsic healing capacity of tendons

Tendon injury during limb motion is common. Damaged tendons heal poorly and frequently undergo unpredictable ruptures or impaired motion due to insufficient innate healing capacity. By basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF) gene therapy via adeno-associated viral type-2 (AAV2) vector to produce supernormal amount of bFGF or VEGF intrinsically in the tendon, we effectively corrected the insufficiency of the tendon healing capacity. This therapeutic approach (1) resulted in substantial amelioration of the low growth factor activity with significant increases in bFGF or VEGF from weeks 4 to 6 in the treated tendons (p < 0.05 or p < 0.01), (2) significantly promoted production of type I collagen and other extracellular molecules (p < 0.01) and accelerated cellular proliferation, and (3) significantly increased tendon strength by 68–91% from week 2 after AAV2-bFGF treatment and by 82–210% from week 3 after AAV2-VEGF compared with that of the controls (p < 0.05 or p < 0.01). Moreover, the transgene expression dissipated after healing was complete. These findings show that the gene transfers provide an optimistic solution to the insufficiencies of the intrinsic healing capacity of the tendon and offers an effective therapeutic possibility for patients with tendon disunion.

Gene therapy strategies to improve strength and quality of flexor tendon healing

INTRODUCTION

Rupture of the repair and adhesion around a tendon are two major problems after tendon surgery. Novel biological therapies which enhance healing and reduce adhesions are goals of many investigations. Gene therapy offers a new and promising approach to tackle these difficult problems. In the past decade, we sought to develop methods to augment tendon healing and reduce tendon adhesion through gene therapy.

AREAS COVERED

This review discusses the methods and results of adeno-associated viral (AAV) type 2 vector gene therapy to increase tendon healing strength and reduce adhesions in a chicken model. Micro-RNA related gene therapy is also discussed. We also developed a controlled release system, which incorporates nanoparticles to deliver micro-RNAs to regulate tendon healing.

EXPERT OPINION

We obtained promising results of enhancement of tendon healing strength in a chicken model using AAV2-mediated gene transfer. AAV2-mediated micro-RNA transfer also limited adhesions around the tendon. Controlled release systems incorporating nanoparticles have ideally delivered genes to the healing tendons and resulted in a moderate (but incomplete) reduction of adhesions. It remains to be determined what the best doses are and what other factors are in play in adhesion formation. These are two targets in our future investigations.

Tenogenic differentiation of mesenchymal stem cells and noncoding RNA: From bench to bedside

Tendon is a critical unit of musculoskeletal system that connects muscle to bone to control bone movement. More population participate in physical activities, tendon injuries, such as acute tendon rupture and tendinopathy due to overuse, are common causing unbearable pain and disability. However, the process of tendon development and the pathogenesis of tendinopathy are not well defined, limiting the development of clinical therapy for tendon injuries. Studying the tendon differentiation control pathways may help to develop novel therapeutic strategies. This review summarized the novel molecular and cellular events in tendon development and highlighted the clinical application potential of non-coding RNAs and tendon-derived stem cells in gene and cell therapy for tendon injuries, which may bring insights into research and new therapy for tendon disorders.