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

Does radiofrequency application improve function and reduce pain in patients with insertional Achilles tendinopathy? A retrospective study with a minimum 2-year follow-up

This case series study aimed to investigate patients with insertional Achilles tendinopathy (IAT) who underwent radiofrequency (RF), how much do their patient-reported outcomes scores improve and what percentage return to sport, and what patient-related factors are associated with improved scores and increased odds of return to sport, at a minimum of 2-year follow-up. Between 2012 and 2018, 41 patients were followed up. The median Victorian Institute of Sports Assessment-Achilles (VISA-A) score increased from 20 (range, 3-62) to 97 (range, 53-100), the median 11-point visual analogue scale (VAS) reduced from 8 (range, 1-10) to 0 (range, 0-3) and the median Tenger score increased from 1 (range, 0-1) to 3 (range, 2-8). Thirty-eight (92.7%) patients returned to sports with a mean time of 11 ± 4.8 months. In linear regression analysis, age was significantly associated with return-to-sports outcome (b = -0.07, 95% CI = -0.13 to -0.02, p = 0.02), while in logistic regression, symptoms duration revealed a significant impact on pain presence (OR = 1.07, 95% CI = 1.01 to 1.14, p = 0.02). In summary, RF for IAT had a 68.7 ± 14.5 VISA-A improvement at 5.4 years of follow-up regarding reliable functional restoration and pain reduction; however, the current evidence remains insufficient to support RF as an effective treatment for IAT.

IL-1β + TGF-β2 dual-licensed mesenchymal stem cells have reduced major histocompatibility class I expression and positively modulate tenocyte migration, metabolism, and gene expression

OBJECTIVE

The study objectives were to 1) determine the mesenchymal stem cell (MSC) surface expression of major histocompatibility complex (MHC) class I and transcriptome-wide gene expression changes following IL-1β + TGF-β2 dual licensing and 2) evaluate if IL-1β + TGF-β2 dual-licensed MSCs had a greater ability to positively modulate tenocyte function compared to naive MSCs.

SAMPLE

Equine bone marrow-derived MSCs from 6 donors and equine superficial digital flexor tenocytes from 3 donors.

METHODS

Experiments were performed in vitro. Flow cytometry and bulk RNA sequencing were utilized to determine naive and dual-licensed MSC phenotype and transcriptome-wide changes in gene expression. Conditioned media were generated from MSCs and utilized in tenocyte cell culture assays as a method to determine the effect of MSC paracrine factors on tenocyte function.

RESULTS

Dual-licensed MSCs have a reduced expression of MHC class I and exhibit enrichment in functional pathways associated with the extracellular matrix, cell signaling, and tissue development. Additionally, dual-licensed MSC-conditioned media significantly improved in vitro tenocyte migration and metabolism to a greater degree than naive MSC-conditioned media. In tenocytes exposed to IL-1β, dual-licensed conditioned media also positively modulated tenocyte gene expression.

CLINICAL RELEVANCE

Our data indicate that conditioned media containing paracrine factors secreted from dual-licensed MSCs significantly modulates in vitro tenocyte function, which may confer benefits in vivo to healing tendons following injury. Additionally, due to reduced MHC class I expression in dual-licensed MSCs, this technique may also provide an avenue to provide an effective "off-the-shelf" allogenic source of MSCs.

Exogenous interleukin-1 beta stimulation regulates equine tenocyte function and gene expression in three-dimensional culture which can be rescued by pharmacological inhibition of interleukin 1 receptor, but not nuclear factor kappa B, signaling

We investigated how Interleukin 1 beta (IL-1β) impacts equine tenocyte function and global gene expression in vitro and determined if these effects could be rescued by pharmacologically inhibiting nuclear factor-κB (NF-KB) or interleukin 1 signalling. Equine superficial digital flexor tenocytes were cultured in three-dimensional (3D) collagen gels and stimulated with IL-1β for two-weeks, with gel contraction and interleukin 6 (IL6) measured throughout and transcriptomic analysis performed at day 14. The impact of three NF-KB inhibitors on gel contraction and IL6 secretion were measured in 3D culture, with NF-KB-P65 nuclear translocation by immunofluorescence and gene expression by qPCR measured in two-dimensional (2D) monolayer culture. In addition, daily 3D gel contraction and transcriptomic analysis was performed on interleukin 1 receptor antagonist-treated 3D gels at day 14. IL-1β increased NF-KB-P65 nuclear translocation in 2D culture and IL6 secretion in 3D culture, but reduced daily tenocyte 3D gel contraction and impacted > 2500 genes at day 14, with enrichment for NF-KB signaling. Administering direct pharmacological inhibitors of NF-KB did reduce NF-KB-P65 nuclear translocation, but had no effect on 3D gel contraction or IL6 secretion in the presence of IL-1β. However, IL1Ra restored 3D gel contraction and partially rescued global gene expression. Tenocyte 3D gel contraction and gene expression is adversely impacted by IL-1β which can only be rescued by blockade of interleukin 1 receptor, but not NF-KB, signalling.

Investigation of the effects of umbilical cord-derived mesenchymal stem cells and curcumin on Achilles tendon healing - can they act synergistically?

BACKGROUND

It is known that curcumin and umbilical cord-derived mesenchymal stem cells (UC-MSCs) positively affect experi-mental tendon injury healing. This study investigated individual effects and potential synergistic effects of using curcumin and UC-MSCs alone and together.

METHODS

Eighty female Wistar albino rats were randomly divided into five groups: Control, curcumin, sesame oil, MSCs, and Curcumin+MSCs groups. In all rats, punch tendon defect was created in both right and left Achilles tendons. While no additional treatment was applied to the control group, curcumin, sesame oil used as a solvent for curcumin, MSCs, and MSCs and curcumin com-bination were applied locally to the injury site, respectively, in the other groups. Curcumin was solved in sesame oil before application. In each group, half of the animals were euthanized in the post-operative 2nd week while the other half were euthanized in the post-operative 4th week. The right Achilles was used for biomechanical testing, while the left Achilles was used for histological evaluation and immunohistochemical analysis of type I, Type III collagen, and tenomodulin.

RESULTS

Histologically, significant improvement was observed in the curcumin, MSCs, and Curcumin+ MSCs groups compared to the control Group in the 2nd week. In the 2nd and 4th weeks, Type III collagen was significantly increased in the curcumin group com-pared to the control group. In week 4, tenomodulin increased significantly in the curcumin and MSCs groups compared to the control group. Tendon tensile strength increased significantly in MSCs and Curcumin+MSCs groups compared to the control group in the 4th week. No superiority was observed between the treatment groups regarding their positive effects on recovery.

CONCLUSION

Locally used curcumin and UC-MSCs showed positive effects that were not superior to each other in the healing of injury caused by a punch in the Achilles tendons of rats. However, synergistic effects on healing were not observed when they were applied together.

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.

Effects of the Foam Massage Roller on VEGF-A and FGF-2 Blood Levels in Young Men

BACKGROUND/AIM

Angiogenesis induced in muscles or massaged tissue is thought to support their regeneration and performance. Therefore, different methods that could promote angiogenesis are investigated. The aim of this study was to examine whether the use of the foam roller massager for lower limb muscles affects VEGF-A and FGF-2 levels in young men.

MATERIALS AND METHODS

The study group included 60 healthy young men attending Military University of Land Forces, Wroclaw, Poland. The participants were randomly divided into two groups. The experimental group included 40 individuals who performed self-massage of the lower limbs using a foam roller. The control group comprised 20 individuals who did not perform massage. Massage was applied to lower limb muscles four times a week for seven weeks. Blood was collected before the experiment and after weeks 1, 3, 5, and 7. ELISA was used to determine changes in VEGF-A and FGF-2 levels in blood serum.

RESULTS

The results of the study demonstrated a significant increase in VEGF-A serum levels in the group of individuals who underwent massage each week compared to VEGF-A concentrations before the experiment. The increase in VEGF-A levels in the experimental group was observed throughout the experiment compared to the control group. No significant changes in serum FGF-2 levels were found.

CONCLUSION

The use of a foam massage roller increased VEGF-A serum levels, which may indicate stimulation of angiogenesis.

Platelet-rich plasma in the pathologic processes of tendinopathy: a review of basic science studies

Tendinopathy is a medical condition that includes a spectrum of inflammatory and degenerative tendon changes caused by traumatic or overuse injuries. The pathological mechanism of tendinopathy has not been well defined, and no ideal treatment is currently available. Platelet-rich plasma (PRP) is an autologous whole blood derivative containing a variety of cytokines and other protein components. Various basic studies have found that PRP has the therapeutic potential to promote cell proliferation and differentiation, regulate angiogenesis, increase extracellular matrix synthesis, and modulate inflammation in degenerative tendons. Therefore, PRP has been widely used as a promising therapeutic agent for tendinopathy. However, controversies exist over the optimal treatment regimen and efficacy of PRP for tendinopathy. This review focuses on the specific molecular and cellular mechanisms by which PRP manipulates tendon healing to better understand how PRP affects tendinopathy and explore the reason for the differences in clinical trial outcomes. This article has also pointed out the future direction of basic research and clinical application of PRP in the treatment of tendinopathy, which will play a guiding role in the design of PRP treatment protocols for tendinopathy.

Stem Cell Applications and Tenogenic Differentiation Strategies for Tendon Repair

Tendons are associated with a high injury risk because of their overuse and age-related tissue degeneration. Thus, tendon injuries pose great clinical and economic challenges to the society. Unfortunately, the natural healing capacity of tendons is far from perfect, and they respond poorly to conventional treatments when injured. Consequently, tendons require a long period of healing and recovery, and the initial strength and function of a repaired tendon cannot be completely restored as it is prone to a high rate of rerupture. Nowadays, the application of various stem cell sources, including mesenchymal stem cells (MSCs) and embryonic stem cells (ESCs), for tendon repair has shown great potential, because these cells can differentiate into a tendon lineage and promote functional tendon repair. However, the mechanism underlying tenogenic differentiation remains unclear. Moreover, no widely adopted protocol has been established for effective and reproducible tenogenic differentiation because of the lack of definitive biomarkers for identifying the tendon differentiation cascades. This work is aimed at reviewing the literature over the past decade and providing an overview of background information on the clinical relevance of tendons and the urgent need to improve tendon repair; the advantages and disadvantages of different stem cell types used for boosting tendon repair; and the unique advantages of reported strategies for tenogenic differentiation, including growth factors, gene modification, biomaterials, and mechanical stimulation.

Hyaluronic acid/platelet rich plasma-infused core-shell nanofiber membrane to prevent postoperative tendon adhesion and promote tendon healing

An anti-adhesive barrier membrane incorporating hyaluronic acid (HA) can reduce fibroblasts attachment and impart lubrication effect for smooth tendon gliding during management of post-surgical tendon adhesion. On the other hand, as numerous growth factors are required during tendon recovery, growth factors released by platelets in platelet-rich plasma (PRP) can provide beneficial therapeutic effects to facilitate tendon recovery post tendon injury. Furthermore, PRP is reported to be associated with anti-inflammatory properties for suppressing postoperative adhesion. Toward this end, we fabricate core-shell nanofiber membranes (NFM) with HA/PRP-infused core and polycaprolactone shell in this study. Different NFM with 100 % (H-P), 75 % (HP31-P), 50 % (HP11-P) and 25 % (H31-P) HA in the core was fabricated through coaxial electrospinning and analyzed through microscopic, pore size, mechanical, as well as HA and growth factor release studies. In vitro study with fibroblasts indicates the NFM can act as a barrier to prevent cell penetration and reduce cell attachment/focal adhesion, in addition to promoting tenocyte migration in tendon healing. In vivo studies in a rabbit flexor tendon rupture model indicates the HP11-P NFM shows improved efficacy over H-P NFM and control in reducing tendon adhesion formation and inflammation, while promoting tendon healing, from functional assays and histological analysis.

Mechanisms of skeletal muscle-tendon development and regeneration/healing as potential therapeutic targets

Skeletal muscle contraction is essential for the movement of our musculoskeletal system. Tendons and ligaments that connect the skeletal muscles to bones in the correct position at the appropriate time during development are also required for movement to occur. Since the musculoskeletal system is essential for maintaining basic bodily functions as well as enabling interactions with the environment, dysfunctions of these tissues due to disease can significantly reduce quality of life. Unfortunately, as people live longer, skeletal muscle and tendon/ligament diseases are becoming more common. Sarcopenia, a disease in which skeletal muscle function declines, and tendinopathy, which involves chronic tendon dysfunction, are particularly troublesome because there have been no significant advances in their treatment. In this review, we will summarize previous reports on the development and regeneration/healing of skeletal muscle and tendon tissues, including a discussion of the molecular and cellular mechanisms involved that may be used as potential therapeutic targets.

Biological and Mechanical Factors and Epigenetic Regulation Involved in Tendon Healing

Tendons are an important part of the musculoskeletal system. Connecting muscles to bones, tendons convert force into movement. Tendon injury can be acute or chronic. Noticeably, tendon healing requires a long time span and includes inflammation, proliferation, and remodeling processes. The mismatch between endogenous and exogenous healing may lead to adhesion causing further negative effects. Management of tendon injuries and complications such as subsequent adhesion formation are still challenges for clinicians. Due to numerous factors, tendon healing is a complex process. This review introduces the role of various biological and mechanical factors and epigenetic regulation processes involved in tendon healing.

Recent advances in tendon tissue engineering strategy

Tendon injuries often result in significant pain and disability and impose severe clinical and financial burdens on our society. Despite considerable achievements in the field of regenerative medicine in the past several decades, effective treatments remain a challenge due to the limited natural healing capacity of tendons caused by poor cell density and vascularization. The development of tissue engineering has provided more promising results in regenerating tendon-like tissues with compositional, structural and functional characteristics comparable to those of native tendon tissues. Tissue engineering is the discipline of regenerative medicine that aims to restore the physiological functions of tissues by using a combination of cells and materials, as well as suitable biochemical and physicochemical factors. In this review, following a discussion of tendon structure, injury and healing, we aim to elucidate the current strategies (biomaterials, scaffold fabrication techniques, cells, biological adjuncts, mechanical loading and bioreactors, and the role of macrophage polarization in tendon regeneration), challenges and future directions in the field of tendon tissue engineering.

Risk factors associated with tendon adhesions after hand tendon repair

Background

Tendon adhesions after hand tendon repair are one of the most difficult complications of hand surgery and can cause severe disability. This study aimed to assess the risk factors associated with tendon adhesions after hand tendon repair to provide a theoretical foundation for the early prevention of tendon adhesions in patients with tendon injuries. Moreover, this study intends to increase doctors' awareness of the issue and serves as a reference for developing new prevention and treatment strategies.

Methods

We retrospectively analyzed 1,031 hand trauma cases that underwent repair after finger tendon injury in our department between June 2009 and June 2019. Tendon adhesions, tendon injury zones, and other relevant information were collected, summarized, and analyzed. The significance of data was determined using a t-test or Pearson's chi-square test, and odds ratios (OR) were calculated using logistic regression tests to describe factors associated with post-tendon repair adhesions.

Results

A total of 1,031 patients were enrolled in this study. There were 817 males and 214 females with an average age of 34.98 (2-82) years. The injured side included 530 left and 501 right hands. Postoperative finger tendon adhesions occurred in 118 cases (11.45%), including 98 males and 20 females, 57 left and 61 right hands. The risk factors for the total sample in the descending order were degloving injury, no functional exercise, zone II flexor tendon injury, time from injury to surgery >12 h, combined vascular injury, and multiple tendon injuries. The flexor tendon sample shared the same risk factors as the total sample. Risk factors for the extensor tendon sample were degloving injury, no functional exercise.

Conclusions

Clinicians should pay close attention to patients with tendon trauma in hand having the following risk factors: degloving injury, zone II flexor tendon injury, lack of functional exercise, time from injury to surgery >12 h, combined vascular injury, and multiple tendon injuries. Due to the high risk of post-repair adhesions in patients with the conditions mentioned above, individualized treatment measures should be designed for the risk factors, and postoperative functional exercise of the hand is required.

Tumour necrosis factor alpha, interleukin 1 beta and interferon gamma have detrimental effects on equine tenocytes that cannot be rescued by IL-1RA or mesenchymal stromal cell-derived factors

Tendon injuries occur commonly in both human and equine athletes, and poor tendon regeneration leads to functionally deficient scar tissue and an increased frequency of re-injury. Despite evidence suggesting inadequate resolution of inflammation leads to fibrotic healing, our understanding of the inflammatory pathways implicated in tendinopathy remains poorly understood, meaning successful targeted treatments are lacking. Here, we demonstrate IL-1β, TNFα and IFN-γ work synergistically to induce greater detrimental consequences for equine tenocytes than when used individually. This includes altering tendon associated and matrix metalloproteinase gene expression and impairing the cells' ability to contract a 3-D collagen gel, a culture technique which more closely resembles the in vivo environment. Moreover, these adverse effects cannot be rescued by direct suppression of IL-1β using IL-1RA or factors produced by BM-MSCs. Furthermore, we provide evidence that NF-κB, but not JNK, P38 MAPK or STAT 1, is translocated to the nucleus and able to bind to DNA in tenocytes following TNFα and IL-1β stimulation, suggesting this signalling cascade may be responsible for the adverse downstream consequences of these inflammatory cytokines. We suggest a superior approach for treatment of tendinopathy may therefore be to target specific signalling pathways such as NF-κB.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Gene Therapy in Orthopaedics: Progress and Challenges in Pre-Clinical Development and Translation

In orthopaedics, gene-based treatment approaches are being investigated for an array of common -yet medically challenging- pathologic conditions of the skeletal connective tissues and structures (bone, cartilage, ligament, tendon, joints, intervertebral discs etc.). As the skeletal system protects the vital organs and provides weight-bearing structural support, the various tissues are principally composed of dense extracellular matrix (ECM), often with minimal cellularity and vasculature. Due to their functional roles, composition, and distribution throughout the body the skeletal tissues are prone to traumatic injury, and/or structural failure from chronic inflammation and matrix degradation. Due to a mixture of environment and endogenous factors repair processes are often slow and fail to restore the native quality of the ECM and its function. In other cases, large-scale lesions from severe trauma or tumor surgery, exceed the body’s healing and regenerative capacity. Although a wide range of exogenous gene products (proteins and RNAs) have the potential to enhance tissue repair/regeneration and inhibit degenerative disease their clinical use is hindered by the absence of practical methods for safe, effective delivery. Cumulatively, a large body of evidence demonstrates the capacity to transfer coding sequences for biologic agents to cells in the skeletal tissues to achieve prolonged delivery at functional levels to augment local repair or inhibit pathologic processes. With an eye toward clinical translation, we discuss the research progress in the primary injury and disease targets in orthopaedic gene therapy. Technical considerations important to the exploration and pre-clinical development are presented, with an emphasis on vector technologies and delivery strategies whose capacity to generate and sustain functional transgene expression in vivo is well-established.

The Functions and Mechanisms of Basic Fibroblast Growth Factor in Tendon Repair

Tendon injury is a disorder of the musculoskeletal system caused by overuse or trauma, which is characterized by pain and limitations in joint function. Since tendon healing is slowly and various treatments are generally ineffective, it remains a clinically challenging problem. Recent evidences suggest that basic fibroblast growth factor (bFGF) not only plays an important role in tendon healing, but also shows a positive effect in laboratory experimentations. The purpose of this review is to summarize the effects of bFGF in the tendon healing. Firstly, during the inflammatory phase, bFGF stimulates the proliferation and differentiation of vascular endothelial cells to foster neovascularization. Furthermore, bFGF enhances the production of pro-inflammatory factors during the early phase of tendon healing, thereby accelerating the inflammatory response. Secondly, the cell proliferation phase is accompanied by the synthesis of a large number of extracellular matrix components. bFGF speeds up tendon healing by stimulating fibroblasts to secrete type III collagen. Lastly, the remodeling phase is characterized by the transition from type III collagen to type I collagen, which can be promoted by bFGF. However, excessive injection of bFGF can cause tendon adhesions as well as scar tissue formation. In future studies, we need to explore further applications of bFGF in the tendon healing process.

Co-Electrospun Silk Fibroin and Gelatin Methacryloyl Sheet Seeded with Mesenchymal Stem Cells for Tendon Regeneration

Silk fibroin (SF) is a promising biomaterial for tendon repair, but its relatively rigid mechanical properties and low cell affinity have limited its application in regenerative medicine. Meanwhile, gelatin-based polymers have advantages in cell attachment and tissue remodeling but have insufficient mechanical strength to regenerate tough tissue such as tendons. Taking these aspects into account, in this study, gelatin methacryloyl (GelMA) is combined with SF to create a mechanically strong and bioactive nanofibrous scaffold (SG). The mechanical properties of SG nanofibers can be flexibly modulated by varying the ratio of SF and GelMA. Compared to SF nanofibers, mesenchymal stem cells (MSCs) seeded on SG fibers with optimal composition (SG7) exhibit enhanced growth, proliferation, vascular endothelial growth factor production, and tenogenic gene expression behavior. Conditioned media from MSCs cultured on SG7 scaffolds can greatly promote the migration and proliferation of tenocytes. Histological analysis and tenogenesis-related immunofluorescence staining indicate SG7 scaffolds demonstrate enhanced in vivo tendon tissue regeneration compared to other groups. Therefore, rational combinations of SF and GelMA hybrid nanofibers may help to improve therapeutic outcomes and address the challenges of tissue-engineered scaffolds for tendon regeneration.

The Economic Impact of Extensor Tendon Lacerations of the Hand in the United States

PURPOSE

Extensor tendon lacerations (ETLs) are a common and debilitating injury for thousands of Americans annually. No study has attempted to estimate their economic impact. The objective of this study was to estimate the economic impact of ETLs in America.

METHODS

The cost of ETLs to society was estimated using a validated prevalence-based cost of illness model. The primary cohort was defined as all patients with complete ETLs in the United States undergoing surgical repair and, secondarily, the imputed number of patients requiring reoperation within 1 year. For these groups, both direct and indirect costs (lost income, missed workdays, and disability payments) were measured.

RESULTS

The total annual direct medical costs amounted to $14,095.28 per injury and 100,000 population. The total annual indirect labor costs were found to range between $80,842.90 and $150,136.82 per injury and 100,000 population. Hence, the estimated total costs of ETLs are $307 million per year in the United States alone and could be as high as $531 million annually depending on the effects of worker absenteeism on the core production-based industries.

CONCLUSIONS

Extensor tendon lacerations incur a significant economic burden to our health care system and are more costly when compared with many other common hand conditions. Specifically, indirect costs are the major contributor toward the total cost these injuries incur on society, accounting for an upward of 91% of the total cost. These results suggest efforts be focused on improving rehabilitation protocols and treatments.

LEVEL OF EVIDENCE

Level II-economic and decision analyses.

Basic science approaches to common hand surgery problems

The field of hand surgery is constantly evolving to meet challenges of populations with increasing age and higher demands for active living. While our surgical care has improved over the last decades, it seems that future major improvement in outcomes of clinical treatment will come through advances in biologics and the translation of major discoveries in basic science. This article aims to provide an update on where basic science solutions may answer some of the most critical issues in hand surgery, with a focus on augmentation of tissue repair.

The Role of Vascular Endothelial Growth Factor in Tendon Healing

Angiogenesis is crucial to facilitate tendon healing, such as delivering oxygen and nutrients, removing waste products, and controlling immune responses. Vascular endothelial growth factor (VEGF) is one of the most vital angiogenic factors that regulate blood vessel formation in tendon healing. Recently, biological therapies, including the application of exogenous VEGF, have been attracting increasing attention. However, at present, the effect of the application of exogenous VEGF in tendon healing is controversial, as the role of endogenous VEGF in tendons has also not been fully elucidated. This article will summarize the role of both endogenous and exogenous VEGF in tendon healing and discuss possible reasons for the controversy. The present review shows that tendon repair is facilitated only by proper angiogenesis and VEGF at the early stage, whereas the persistent high VEGF expression and prolonged presence of blood vessels may impair tendon repair at a later stage.

Boost Tendon/Ligament Repair With Biomimetic and Smart Cellular Constructs

Tendon and ligament are soft connective tissues that play essential roles in transmitting forces from muscle to bone or bone to bone. Despite significant progress made in the field of ligament and tendon regeneration over the past decades, many strategies struggle to recapitulate basic structure-function criteria of native ligament/tendon. The goal here is to provide a fundamental understanding of the structure and composition of ligament/tendon and highlight few key challenges in functional regeneration of these connective tissues. The remainder of the review will examine several biomaterials strategies including biomimetic scaffold with non-linear mechanical behavior, hydrogel patch with anisotropic adhesion and gene-activated scaffold for interactive healing of tendon/ligament. Finally, emerging technologies and research avenues are suggested that have the potential to enhance treatment outcomes of tendon/ligament injuries.

Modulation of vascular response after injury in the rat Achilles tendon alters healing capacity

Tendons are relatively hypovascular but become hypervascular during both injury and degeneration. This is due to the angiogenic response, or the formation of new blood vessels, to tissue injury. The objective of this study was to evaluate the effect of vascular modulation in the rat Achilles tendons during healing. Fischer rats received a bilateral Achilles incisional injury followed by local injections of vascular endothelial growth factor (VEGF), anti-VEGF antibody (B20.4-1-1), or saline either early or late during the healing process. Vascular modulation and healing were evaluated using multiple in vivo ultrasound imaging modalities, in vivo functional assessment, and ex vivo measures of tendon compositional and mechanical properties. The late delivery of anti-VEGF antibody, B20, caused a temporary reduction in healing capacity during a time point where vascularity was also decreased, and then an improvement during a later time point where vascularity was increased relative to control. However, VEGF delivery had a minimal impact on healing and vascular changes in both early and late delivery times. This study was the first to evaluate vascular changes using both in vivo imaging methods and ex vivo histological methods, as well as functional and mechanical outcomes associated with these vascular changes. Clinical significance: this study demonstrates that the alteration of vascular response through the delivery of angiogenic growth factors has the ability to alter tendon healing properties.

Application of Stem Cell Therapy for ACL Graft Regeneration

Graft regeneration after anterior cruciate ligament (ACL) reconstruction surgery is a complex three-stage process, which usually takes a long duration and often results in fibrous scar tissue formation that exerts a detrimental impact on the patients' prognosis. Hence, as a regeneration technique, stem cell transplantation has attracted increasing attention. Several different stem cell types have been utilized in animal experiments, and almost all of these have shown good capacity in improving tendon-bone regeneration. Various differentiation inducers have been widely applied together with stem cells to enhance specific lineage differentiation, such as recombinant gene transfection, growth factors, and biomaterials. Among the various different types of stem cells, bone marrow-derived mesenchymal stem cells (BMSCs) have been investigated the most, while ligament stem progenitor cells (LDSCs) have demonstrated the best potential in generating tendon/ligament lineage cells. In the clinic, 4 relevant completed trials have been reported, but only one trial with BMSCs showed improved outcomes, while 5 relevant trials are still in progress. This review describes the process of ACL graft regeneration after implantation and summarizes the current application of stem cells from bench to bedside, as well as discusses future perspectives in this field.

The effect of fibrin clot and C vitamin on the surgical treatment of Achilles tendon injury in the rat model✰

BACKGROUND

This study aimed to determine the histological, biochemical, and biomechanical efficacy of fibrin clot and vitamin C in the healing of Achilles tendon ruptures (ATR) in a rat model.

METHODS

52 adult Wistar-Albino rats (300-450 g) were used in the study. 12 rats were divided into four groups as Monitor (Group I), Control (Group II), Fibrin Clot (Group III), Fibrin Clot with vitamin C (Group IV). Four rats were used for fibrin clot preparation. Fibroblast Growth Factor (FGF) and Vascular Endothelial Growth Factor (VEGF) were measured on the 3rd, 7th, 14th, and 21st days. Four rats were sacrificed on the 21st day from each group for histological evaluation. The rest of the rats were sacrificed at 42nd day, half for biomechanical and a half for histological evaluation.

RESULTS

The 42nd-day HSS score of group IV was significantly lower than those of group I, group II and group III (p = 0.036, p = 0.019, and p = 0.036, respectively). Group IV showed a significantly higher Maximum force N value than those of group I, group II and group III (p = 0.034, p = 0.034 and, p = 0.025, respectively). The blood FGF and VEGF levels of group III and group IV on the 3rd, 7th, 14th, and 21st days were higher than those of group I and group II (p < 0.05).

CONCLUSION

Fibrin clot and vitamin C produced a stronger tendon structure in terms of biomechanics while providing histological and biochemically better quality tendon healing in the surgical treatment of ATR. This model can be used to accelerate high-quality tendon healing after ATR.

LEVEL OF EVIDENCE

Level II, experimental study.

Basic Research on Tendon Repair: Strategies, Evaluation, and Development

Tendon is a fibro-elastic structure that links muscle and bone. Tendon injury can be divided into two types, chronic and acute. Each type of injury or degeneration can cause substantial pain and the loss of tendon function. The natural healing process of tendon injury is complex. According to the anatomical position of tendon tissue, the clinical results are different. The wound healing process includes three overlapping stages: wound healing, proliferation and tissue remodeling. Besides, the healing tendon also faces a high re-tear rate. Faced with the above difficulties, management of tendon injuries remains a clinical problem and needs to be solved urgently. In recent years, there are many new directions and advances in tendon healing. This review introduces tendon injury and sums up the development of tendon healing in recent years, including gene therapy, stem cell therapy, Platelet-rich plasma (PRP) therapy, growth factor and drug therapy and tissue engineering. Although most of these therapies have not yet developed to mature clinical application stage, with the repeated verification by researchers and continuous optimization of curative effect, that day will not be too far away.

Identification and Distinction of Tenocytes and Tendon-Derived Stem Cells

Restoring the normal structure and function of injured tendons is one of the biggest challenges in orthopedics and sports medicine department. The discovery of tendon-derived stem cells (TDSCs) provides a novel perspective to treat tendon injuries, which is expected to be an ideal seed cell to promote tendon repair and regeneration. Because of the lack of specific markers, the identification of tenocytes and TDSCs has not been conclusive in the in vitro study of tendons. In addition, the morphology of tendon derived cells is similar, and the comparison and identification of tenocytes and TDSCs are insufficient, which causes some obstacles to the in vitro study of tendon. In this review, the characteristics of tenocytes and TDSCs are summarized and compared based on some existing research results (mainly in terms of biomarkers), and a potential marker selection for identification is suggested. It is of profound significance to further explore the mechanism of biomarkers in vivo and to find more specific markers.

Double layer composite membrane for preventing tendon adhesion and promoting tendon healing

Electrospun membranes and hydrogels are widely used to prevent tendon adhesion. Hydrophobic anti-inflammatory drugs could be fully loaded on the electrospinning membrane through the electrospinning process, which can better prevent tendon adhesion. Basic fibroblast growth factor (bFGF) could promote tendon healing. However, the bioactivity of free bFGF is easily inactivated, therefore, a suitable carrier is needed. As a carrier, hydrogel has little effect on the bioactivity of the protein drugs. In this work, a poly(lactic-co-glycolic) acid (PLGA) electrospun membrane loaded with ibuprofen (IBU) was prepared and named EMI. Additionally, Methoxy poly(ethylene glycol)-block-poly(L-valine) (PEG-PLV) was synthesized. bFGF was added to the PEG-PLV solution, a hydrogel containing bFGF (PLVB) was obtained after gelling. PLVB was applied to the surface of EMI, a double-layer composite membrane named EMI-PLVB was obtained. This membrane was used to prevent Achilles tendon adhesion and promote healing. IBU and bFGF in EMI-PLVB were continuously released in vitro. The inflammatory factors at the tendon healing site were significantly reduced, and the production of type I collagen (Col- I) and type III Collagen (Col-III) at the tendon healing site was also increased in vivo. In conclusion, this double-layer composite membrane drug release system can effectively prevent tendon adhesion and promote tendon healing.

Advanced technology-driven therapeutic interventions for prevention of tendon adhesion: Design, intrinsic and extrinsic factor considerations

Tendon adhesion formation describes the development of fibrotic tissue between the tendon and its surrounding tissues, which commonly occurs as a reaction to injury or surgery. Its impact on function and quality of life varies from negligible to severely disabling, depending on the affected area and extent of adhesion formed. Thus far, treatment options remain limited with prophylactic anti-inflammatory medications and revision surgeries constituting the only tools within the doctors' armamentarium - neither of which provides reliable outcomes. In this review, the authors aim to collate the current understanding of the pathophysiological mechanisms underlying tendon adhesion formation, highlighting the significant role ascribed to the inflammatory cascade in accelerating adhesion formation. The bulk of this article will then be dedicated to critically appraising different therapeutic structures like nanoparticles, hydrogels and fibrous membranes fabricated by various cutting-edge technologies for adhesion formation prophylaxis. Emphasis will be placed on the role of the fibrous membranes, their ability to act as drug delivery vehicles as well as the combination with other therapeutic structures (e.g., hydrogel or nanoparticles) or fabrication technologies (e.g., weaving or braiding). Finally, the authors will provide an opinion as to the future direction of the prevention of tendon adhesion formation in view of scaffold structure and function designs.

Nanoparticle-coated sutures providing sustained growth factor delivery to improve the healing strength of injured tendons

Tendon injuries are common diseases. The healing capacity of tendon is limited due to its special composition of extra-cellular matrix and hypocellularity and hypovascularity. The purpose of this study was to evaluate the effectiveness of nanoparticle-coated sutures carrying growth factors for accelerating tendon repair. A variety of experimental methods had been used to investigate the characteristics and therapeutic effects of the modified sutures. Nanoparticles could adhere uniformly to the surface of the suture through polydopamine. Even sutured in the tendon, most of nanoparticles were still remained on the surface of suture, and the loaded proteins could spread into the tendon tissues. In vivo study, the ultimate strength of repaired tendons treated with bFGF and VEGFA-releasing sutures was significantly greater than the tendons repaired with control sutures at multiple time-points, whether in the chicken model of flexor tendon injury or the rat model of Achilles tendon injury. At week 6, the adhesion score in the bFGF and VEGFA-releasing suture group was significantly lower than those of the control suture group. Tendon gliding excursion was significantly longer in the bFGF and VEGFA-releasing suture group than that in the control bare sutures. Work of digital flexion was significantly decreased in the bFGF and VEGFA-releasing suture group. In a word, we developed a platform for local and continuous delivery of growth factors based on the nanoparticle-coated sutures, which could effectively deliver growth factors to tissues and control the release of growth factors. This growth factors delivery system is an attractive therapeutic tool to repair injured tendons. STATEMENT OF SIGNIFICANCE: Tendon rupture is a common clinical injury, due to the special character of the tendon with mainly extra cellular matrix and hypocellularity and hypovascularity, the healing capacity of the injured tendon is limited. In this study, nanoparticle-coated surgical sutures carrying growth factors were prepared to accelerate tendon repair. After treatment, bFGF and VEGFA loaded nanoparticle-coated sutures can significantly enhance tendon healing, and significantly improve tendon gliding function and effectively inhibit the formation of adhesion. Moreover, these nanoparticle-coated sutures have good biocompatibility and no obvious tissue reaction, which provides more guarantee for further clinical application. This is an attractive and promising approach that uses surgical suture as a growth factor delivery tool to repair tendon injury, which can simplify the treatment. And this kind of bioactive sutures may be applied to other tissue repair, such as muscle, nerve, intestinal canal, blood vessel, skin, and so on.

Transcriptome profiling of digital flexor tendons after injury in a chicken model

BACKGROUND

Modulation of tendon healing remains a challenge because of our limited understanding of the tendon repair process. Therefore, we performed the present study to provide a global perspective of the gene expression profiles of tendons after injury and identify the molecular signals driving the tendon repair process.

RESULTS

The gene expression profiles of flexor digitorum profundus tendons in a chicken model were assayed on day 3, weeks 1, 2, 4, and 6 after injury using the Affymetrix microarray system. Principal component analysis (PCA) and hierarchical cluster analysis of the differentially expressed genes showed three distinct clusters corresponding to different phases of the tendon healing period. Gene ontology (GO) analysis identified regulation of cell proliferation and cell adhesion as the most enriched biological processes. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis revealed that the cytokine-cytokine receptor interaction and extracellular matrix (ECM)-receptor interaction pathways were the most impacted. Weighted gene co-expression network analysis (WGCNA) demonstrated four distinct patterns of gene expressions during tendon healing. Cell adhesion and ECM activities were mainly associated with genes with drastic increase in expression 6 weeks after injury. The protein-protein interaction (PPI) networks were constructed to identify the key signaling pathways and hub genes involved.

CONCLUSIONS

The comprehensive analysis of the biological functions and interactions of the genes differentially expressed during tendon healing provides a valuable resource to understand the molecular mechanisms underlying tendon healing and to predict regulatory targets for the genetic engineering of tendon repair. Tendon healing, Adhesion, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, Weighted Gene Co-expression Network Analysis, Protein-protein Interaction.

Bio-artificial pleura using autologous dermal fibroblast sheets to mitigate air leaks during thoracoscopic lung resection

Lung air leaks (LALs) due to visceral pleura injury during surgery are a difficult-to-avoid complication in thoracic surgery (TS). Reliable LAL closure is an important patient management issue after TS. We demonstrated both safeties of transplantation of a cultured human autologous dermal fibroblast sheet (DFS) to LALs. From May 2016 to March 2018, five patients who underwent thoracoscopic lung resection met all the inclusion criteria. Skin biopsies were acquired from each patient to source autologous dermal cells for DFS fabrication. During the primary culture, fibroblasts migrated from the dermal tissue pieces and proliferated to form cell monolayers. These fibroblasts were subcultured to confluence. Transplantable DFSs were fabricated from these subcultured fibroblasts that were trypsinized and seeded onto temperature-responsive culture dishes. After 10 days of fabrication culture, intact patient-specific DFS were harvested. DFSs were analyzed for fibroblast cell content and tissue contaminants prior to application. For closing intraoperative LAL, mean number of transplanted autologous DFS per patient was 6 ± 2 sheets. Mean chest drainage duration was 5.0 ± 4.8 days. The two patients with major LAL had a drainage duration of more than 7 days. All patients currently have no LAL recurrence after discharge. DFSs effectively maintain LAL closure via remodeling of the deposited extracellular matrix. The use of autologous DFSs to permanently close air leaks using a patient-derived source is expected to reduce surgical complications during high-risk lung resections.

Effects of nanoparticle-mediated growth factor gene transfer to the injured microenvironment on the tendon-to-bone healing strength

The tendon-to-bone healing after trauma is usually slow and weak, and the repair site is easily disrupted during early mobilization exercise. bFGF and VEGFA gene therapy may hold promise in augmenting the tendon-to-bone healing process through enhancing cell proliferation and angiogenesis. This study is conducted to determine the effects of nanoparticle-mediated co-delivery of bFGF and VEGFA genes to the tendon-to-bone repair interface on the healing strength and biological responses in a chicken model. The PLGA nanoparticle/pEGFP-bFGF + pEGFP-VEGFA plasmid complexes were prepared and were characterized in vitro and in vivo. The nanoparticle/plasmid complexes can effectively transfer bFGF and VEGFA genes to the tendon-to-bone interface. Nanoparticle-mediated co-delivery of bFGF and VEGFA genes significantly improved the tendon-to-bone healing in terms of healing strengths and histology in a chicken flexor tendon repair model. Our results suggest a new biological approach to accelerate the tendon-to-bone healing.

The Economic Impact of Flexor Tendon Lacerations of the Hand in the United States

PURPOSE

Flexor tendon lacerations are a common and debilitating injury for thousands of Americans annually. Despite this, no study has attempted to estimate the economic impact of these injuries. The objective of this study was to estimate the economic impact of flexor tendon lacerations in America.

METHODS

The cost of flexor tendon lacerations to society was estimated using a validated prevalence-based cost of illness model. The primary cohort was defined as all patients in the United States presenting with complete flexor tendon lacerations who underwent surgical repair. The secondary cohort was defined by all patients who required reoperation within 1 year of their initial operation. For these groups, both direct and indirect costs (lost income, missed workdays, and disability payments) were measured.

RESULTS

Flexor tendon lacerations incur an estimated cost of between US $240.8 and US $409.1 million annually to the American medical system. The total direct cost per injury is estimated to be US $13,725, whereas estimates to the indirect costs range from US $60,786 to US $112,888.

CONCLUSIONS

Flexor tendon lacerations represent an important economic burden to our health care system, even when compared with other common hand conditions. Specifically, indirect costs, such as missed workdays, are the major contributor toward the total cost these injuries incur on society, accounting for upward of 89% of the total cost. This suggests that we should focus our efforts to improve treatments and rehabilitation protocols which decrease these indirect costs.

Application of gene therapy in the treatment of superficial digital flexor tendon injury in horses

Background:

Tendon injuries are one of the most common causes of orthopedic disorders in horses. Such injuries involve a long course of treatment and recovery. The most promising method of treating these injuries is the use of recombinant proteins and gene therapy.

Aim:

In this work, we evaluated the therapeutic efficacy of plasmid DNA (pDNA) containing two species-specific coding sequences, i.e. vascular endothelial growth factor 164 (VEGF164) and fibroblast growth factor 2 (FGF2), in the treatment of severe damage to the tendon of the superficial digital flexor.

Methods:

A pDNA construct was used to restore the damaged superficial digital flexor tendon in the horse.

Results:

This study showed that the administration of pDNA encoding VEGF164 and FGF2 genes at the injury area increased the regenerative activities of the damaged tendon.

Conclusion:

This study shows the therapeutic properties of genetic constructs (pDNA) and contributes to the advancements in the use of these therapies.

Mesenchymal Stem Cells Seeded Decellularized Tendon Scaffold for Tissue Engineering

Tendon is a collagenous tissue to connect bone and muscle. Healing of damaged/injured tendon is the primary clinical challenge in musculoskeletal regeneration because they often react poorly to treatment. Tissue engineering (a triad strategy of scaffolds, cells and growth factors) may have the potential to improve the quality of tendon tissue healing under such impaired situations. Tendon tissue engineering aims to synthesize graft alternatives to repair the injured tendon. Biological scaffolds derived from decellularized tissue may be a better option as their biomechanical properties are similar to the native tissue. This review is designed to provide background information on the current challenges in curing torn/worn out the tendon and the clinical relevance of decellularized scaffolds for such applications.

Advances in the development of gene therapy, noncoding RNA, and exosome-based treatments for tendinopathy

Tendinopathy is a common musculoskeletal disorder characterized by chronic low-grade inflammation and tissue degeneration. Tendons have poor innate healing ability and there is currently no cure for tendinopathy. Studies elucidating mechanisms underlying the pathogenesis of tendinopathy and mechanisms mediating the genesis of tendons during development have provided novel targets and strategies to enhance tendon healing and repair. This review summarizes the current understanding and treatments for tendinopathy. The review also highlights recent advances in gene therapy, the potential of noncoding RNAs, such as microRNAs, and exosomes, which are nanometer-sized extracellular vesicles secreted from cells, for the treatment of tendinopathy.

Multi-differentiation potential is necessary for optimal tenogenesis of tendon stem cells

Background

Tendon injury is a significant clinical problem due to poor healing and a high reinjury rate; successful treatment is limited by our poor understanding of endogenous tendon stem cells. Recent evidence suggests that adult stem cells are phenotypically diverse, even when comparing stem cells isolated from the same tissue from the same individual, and may in fact exist on a spectrum of proliferation and differentiation capacities. Additionally, the relationships between and clinical relevance of this phenotypic variation are poorly understood. In particular, tenogenic capacity has not been studied in comparison to tenogenic differentiation and cell proliferation. Toward this end, we performed a comprehensive assessment of cell proliferation and differentiation capacity toward four connective tissue lineages (tendon, cartilage, bone, and adipose) using tendon stem cell lines derived from single cells released directly from tendon tissue to (1) evaluate the differences, if any, in tenogenic potential, and (2) identify the relationships between differentiation phenotypes and proliferation capacity.

Methods

Tendon stem cells were derived from the endotenon of superficial digital flexor tendon from 3 horses. The cell suspension from each horse was separately plated simultaneously (1) at moderate density to generate a heterogenous population of cells—parent tendon cell line—and (2) at low density to separate single cells from each other to allow isolation of colonies that derive from single mother cells—clonal tendon stem cell lines.

Thirty clonal tendon stem cell lines—10 from each horse—and each parent tendon cell line were assessed for tenogenesis, tri-lineage differentiation, and cell proliferation. Differentiation was confirmed by lineage-specific cell staining and quantified by the relative gene expression of lineage-specific markers. Statistical significance was determined using analysis of variance and post hoc Tukey’s tests.

Results

Three distinct differentiation phenotypes—differentiation potency toward all 4 tissue lineages and two tri-lineage differentiation potencies—were identified in tendon clonal stem cell lines. These phenotypes were differentiation toward (1) tendon, cartilage, bone, and adipose (TCOA); (2) tendon, cartilage, and bone (TCO); and (3) tendon, cartilage, and adipose (TCA). Further, clonal cell lines that differentiated toward all four lineages had the highest expression of scleraxis and mohawk upon tenogenesis. Moreover, cell proliferation was significantly different between phenotypic groups, as evidenced by increased numbers of cumulative cell population doublings in clonal cell lines that did not differentiate toward adipose.

Conclusions

Our study provides evidence of the heterogenous character of adult stem cells and identifies key differences in tendon stem cell differentiation and proliferative potentials from the same individual and from the same tendon. Isolation of tendon stem cell lines with the capacity to differentiate into all four connective tissue lineages may yield improved therapeutic benefits in clinical models of repair and promote a native, regenerative phenotype in engineered tendons. Future studies may be targeted to understanding the functional contributions of each tendon stem cell phenotype in vivo and identifying additional cell phenotypes.

Flexor Tendon: Development, Healing, Adhesion Formation, and Contributing Growth Factors

Management of flexor tendon injuries of the hand remains a major clinical problem. Even with intricate repair, adhesion formation remains a common complication. Significant progress has been made to better understand the mechanisms of healing and adhesion formation. However, there has been slow progress in the clinical prevention and reversal of flexor tendon adhesions. The goal of this article is to discuss recent literature relating to tendon development, tendon healing, and adhesion formation to identify areas in need of further research. Additional research is needed to understand and compare the molecular, cellular, and genetic mechanisms involved in flexor tendon morphogenesis, postoperative healing, and mechanical loading. Such knowledge is critical to determine how to improve repair outcomes and identify new therapeutic strategies to promote tissue regeneration and prevent adhesion formation.

PEG grafted chitosan scaffold for dual growth factor delivery for enhanced wound healing

Application of growth factors at wound site has improved the efficiency and quality of healing. Basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) induce proliferation of various cells in wound healing. Delivery of growth factor from controlled release systems protect it from degradation and also result in sustained delivery of it at the site of injury. The goal of the study was to develop a Polyethylene glycol (PEG) cross-linked cotton-like chitosan scaffold (CS-PEG-H) by freeze-drying method and chemically conjugate heparin to the scaffold to which the growth factors can be electrostatically bound and evaluate its wound healing properties in vitro and in vivo. The growth factor containing scaffolds induced increased proliferation of HaCaT cells, increased neovascularization and collagen formation seen by H and E and Masson's trichrome staining. Immunohistochemistry was performed using the Ki67 marker which increased proliferation of cells in growth factor containing scaffold treated group. Frequent dressing changes are a major deterrent to proper wound healing. Our system was found to release both VEGF and bFGF in a continuous manner and attained stability after 7 days. Thus our system can maintain therapeutic levels of growth factor at the wound bed thereby avoiding the need for daily applications and frequent dressing changes. Thus, it can be a promising candidate for wound healing.

Autologous Microfragmented Adipose Tissue Reduces the Catabolic and Fibrosis Response in an In Vitro Model of Tendon Cell Inflammation

Background

Mesenchymal stem cells (MSCs) emerged as a promising therapy for tendon pathologies. Microfragmented adipose tissue (μFAT) represents a convenient autologous product for the application of MSC-based therapies in the clinical setting. In the present study, the ability of μFAT to counteract inflammatory processes induced by IL-1β on human tendon cells (TCs) was evaluated.

Methods

Cell viability and proliferation were evaluated after 48 hours of transwell coculture of TCs and autologous μFAT in the presence or absence of IL-1β. Gene expression of scleraxis, collagen type I and type III, metalloproteinases-1 and -3, and cyclooxygenase-2 was evaluated by real-time RT-PCR. The content of VEGF, IL-1Ra, TNFα, and IL-6 was evaluated by ELISA.

Results

IL-1β-treated TCs showed augmented collagen type III, metalloproteases, and cyclooxygenase-2 expression. μFAT was able to reduce the expression of collagen type III and metalloproteases-1 in a significant manner, and at the same time, it enhanced the production of VEGF, IL-1Ra, and IL-6.

Conclusions

In this in vitro model of tendon cell inflammation, the paracrine action of μFAT, exerted by anti-inflammatory molecules and growth factors, was able to inhibit the expression of fibrosis and catabolic markers. Then, these results suggest that the application of μFAT may represent an effective conservative or adjuvant therapy for the treatment of tendon disorders.

Current Trends in Viral Gene Therapy for Human Orthopaedic Regenerative Medicine

Background

Viral vector-based therapeutic gene therapy is a potent strategy to enhance the intrinsic reparative abilities of human orthopaedic tissues. However, clinical application of viral gene transfer remains hindered by detrimental responses in the host against such vectors (immunogenic responses, vector dissemination to nontarget locations). Combining viral gene therapy techniques with tissue engineering procedures may offer strong tools to improve the current systems for applications in vivo.

Methods

The goal of this work is to provide an overview of the most recent systems exploiting biomaterial technologies and therapeutic viral gene transfer in human orthopaedic regenerative medicine.

Results

Integration of tissue engineering platforms with viral gene vectors is an active area of research in orthopaedics as a means to overcome the obstacles precluding effective viral gene therapy.

Conclusions

In light of promising preclinical data that may rapidly expand in a close future, biomaterial-guided viral gene therapy has a strong potential for translation in the field of human orthopaedic regenerative medicine.

Gene-Loaded Nanoparticle-Coated Sutures Provide Effective Gene Delivery to Enhance Tendon Healing

How to accelerate tendon healing remains a clinical challenge. In this study, a suture carrying nanoparticle/pEGFP-basic fibroblast growth factor (bFGF) and pEGFP-vascular endothelial growth factor A (VEGFA) complexes was developed to transfer the growth factor genes into injured tendon tissues to promote healing. Polydopamine-modified sutures can uniformly and tightly absorb nanoparticle/plasmid complexes. After tendon tissues were sutured, the nanoparticle/plasmid complexes still existed on the suture surface. Further, we found that the nanoparticle/plasmid complexes delivered into tendon tissues could diffuse from sutures to tendon tissues and effectively transfect genes into tendon cells, significantly increasing the expression of growth factors in tendon tissues. Finally, biomechanical tests showed that nanoparticle/pEGFP-bFGF and pEGFP-VEGFA complex-coated sutures could significantly increase the ultimate strengths of repaired tendons, especially at 4 weeks after operation. Two kinds of nanoparticle/plasmid complex-coated sutures significantly increased flexor tendon healing strength by 3.7 times for Ethilon and 5.8 times for PDS II, respectively, compared with the corresponding unmodified sutures. In the flexor tendon injury model, at 6 weeks after surgery, compared with the control suture, the nanoparticle/plasmid complex-coated sutures can significantly increase the gliding excursions of the tendon and inhibit the formation of adhesion. These results indicate that this nanoparticle/plasmid complex-coated suture is a promising tool for the treatment of injured tendons.

Applications of Virus Vector-Mediated Gene Therapy in China

Due to the increased safety and efficiency of virus vectors, virus vector-mediated gene therapy is now widely used for various diseases, including monogenic diseases, complex disorders, and infectious diseases. Recent gene therapy trials have shown significant therapeutic benefits, and Chinese researchers have contributed significantly to this progress. This review highlights disease applications and strategies for virus vector-mediated gene therapy in preclinical studies and clinical trials in China.

Tenocyte cell density, migration, and extracellular matrix deposition with amniotic suspension allograft

Amniotic suspension allografts (ASA), derived from placental tissues, contain particulated amniotic membrane and amniotic fluid cells. Recently, ASA and other placental-derived allografts have been used in orthopaedic applications, including tendinopathies and tendon injuries. The purpose of this study was to determine the potential effects of ASA on tenocyte cell density, migration, and responses to inflammatory stimuli. Tenocyte cell density was measured using AlamarBlue over multiple time points, while migration was determined using a Boyden chamber assay. Deposition of ECM markers were measured using BioColor kits. Gene expression and protein production of cytokines and growth factors following stimulus with pro-inflammatory IL-1β and TNF-α was measured using qPCR and ELISAs. Conditioned media (CM) was made from ASA and used for all assays in this study. In vitro, ASA CM treatment significantly promoted tenocyte increases in cell density and migration compared to assay media controls. ASA CM also increased the deposition of extracellular matrix (ECM) proteins, including collagen, elastin, and sGAG. Following inflammatory stimulation and treatment with ASA CM, tenocytes downregulated IL-8 gene expression, a pro-inflammatory cytokine normally elevated during the inflammatory phase of tendon healing. Additionally, tenocytes treated with ASA CM had significantly lower protein levels of TGF-β1 compared to controls. This study evaluated ASA and its effect on tenocytes; specifically, treatment with ASA resulted in increased cell density, more robust migration and matrix deposition, and some alteration of inflammatory targets. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:412-420, 2019.

Current trends in tendinopathy: consensus of the ESSKA basic science committee. Part II: treatment options

The treatment of painful chronic tendinopathy is challenging. Multiple non-invasive and tendon-invasive methods are used. When traditional non-invasive treatments fail, the injections of platelet-rich plasma autologous blood or cortisone have become increasingly favored. However, there is little scientific evidence from human studies supporting injection treatment. As the last resort, intra- or peritendinous open or endoscopic surgery are employed even though these also show varying results. This ESSKA basic science committee current concepts review follows the first part on the biology, biomechanics and anatomy of tendinopathies, to provide a comprehensive overview of the latest treatment options for tendinopathy as reported in the literature.

Gene Therapy Using Plasmid DNA Encoding VEGF164 and FGF2 Genes: A Novel Treatment of Naturally Occurring Tendinitis and Desmitis in Horses

This clinical study describes the intralesional application of the plasmid DNA encoding two therapeutic species-specific growth factors: vascular endothelial growth factor (VEGF164) and fibroblast growth factor 2 (FGF2) in seven horses to restore naturally occurring injuries of the superficial digital flexor tendon (SDFT) (tendinitis) and in three horses with suspensory ligament branch desmitis. Following application all horses were able to commence a more rapid exercise program in comparison to standardized exercise programs. Clinical observation and ultrasonic imaging was used to evaluate the regeneration rate of the tendon and ligament injury recovery and to confirm the safety of this gene therapy in horses, throughout a 12 month period. Follow-up data of the horses revealed a positive outcome including significant ultrasonographic and clinical improvements in 8 out of 10 horses with SDFT and suspensory ligament branch lesions, with return to their pre-injury level of performance by 2–6 months after the completion of treatment. The ninth horse initially presenting with severe suspensory ligament branch desmopathy, showed no significant ultrasonographic improvements in the first 2 months after treatment, however, it improved clinically and became less lame. The final horse, presenting with severe tendinitis of the SDFT returned to their pre-injury level of performance, but experienced re-injury 6 months after treatment. This data is highly promising, however, further research in experimental models, with the histopathological, immunohistochemical and gene expression evaluation of the equine tendon/ligament after gene therapy application is required in order to fully understand the mechanisms of action. This treatment and the significant clinical impacts observed represents an important advancement in the field of medicine.

A Comparison of Radiofrequency-Based Microtenotomy and Arthroscopic Release of the Extensor Carpi Radialis Brevis Tendon in Recalcitrant Lateral Epicondylitis: A Prospective Randomized Controlled Study

PURPOSE

To compare the clinical effects of radiofrequency (RF)-based microtenotomy and arthroscopic release of the extensor carpi radialis brevis (ECRB) tendon in patients with recalcitrant lateral epicondylitis through a prospective randomized controlled study.

METHODS

A total of 46 patients were randomly assigned to receive arthroscopic release (group A, 24 patients) or RF-based microtenotomy (group B, 22 patients). The visual analog scale (VAS) score for pain, flexion-extension arc, operation time, Disabilities of the Arm, Shoulder, and Hand questionnaire (DASH), Mayo Elbow Performance Score (MEPS), and grip power of groups A and B were compared during the recovery phases for up to 2 postoperative years.

RESULTS

Both groups showed statistically significant functional improvement compared with their preoperative grip strength and DASH, VAS, and MEPS scores at 2 years after surgery (P < .05). There were no differences in postoperative pain relief or functional restoration between the 2 groups during the recovery phases, however the mean operation time for group B (41.4 ± 5.2 minutes) was significantly shorter than that for group A (15.6 ± 3.6 minutes, P < .001). In group B, 1 patient underwent revision surgery due to postoperative ECRB rupture, and 1 patient in group A underwent open release for persistent postoperative discomfort.

CONCLUSIONS

RF-based microtenotomy for treating recalcitrant lateral epicondylitis provided clinical outcomes comparable with those from arthroscopic release of ECRB tendon during the recovery phase. RF-based microtenotomy is considered as one of the surgical procedures for treating recalcitrant lateral epicondylitis, with the advantages of reliable elbow functional restoration and significantly shorter operation time.

LEVEL OF EVIDENCE

Level I, prospective randomized trial.