In vitro flexor tendon cell response to TGF-beta1: a gene expression study

Early activity after strong sutures helps to tendon healing in a rat tendon rupture model

The purpose of this study was to investigate the effect of different times return to activity on tendon healing after Double Kessler method suture in rats with Achilles tendon rupture. The left Achilles tendon of 80 10-week-old rats was repaired. The rats were randomly divided into 4 groups: non-fixed group, fixed one week group, fixed two weeks group and fixed three weeks group. In the fourth week, all rats were trained on a treadmill for one hour a day at a speed of 10 m/min. Complications were recorded during the study period and passive ankle motion was measured after the rats were euthanized. The healing and adhesion of tendons were evaluated by anatomy, biomechanics, histology and immunohistochemistry. The earlier return to activity after surgery, the higher the quality of tendon healing and the less adhesion will occur. There was no difference in complication rate among the four groups (P< 0.05). There was one case of tendon re-rupture in the non-fixed group and one case in the fixed one week group. The passive range of motion, biomechanical properties, histological evaluation and immunohistochemical results of the ankle in non-fixed group were better than those in the other three groups, while those in fixed three weeks group were worse than those in the other three groups (P< 0.05). The passive ankle range of motion, count of fibroblasts, biomechanical results, and immunohistochemical results showed no statistic significant difference between the fixed one week group and fixed two weeks group (P> 0.05). Early return to activity with strong sutures is advantageous for tendon injuries. With the advanced of return to activity time, the healing strength of tendon increased and the degree of adhesion decreased four weeks after surgery.

Non-isocyanate polyurethane-co-polyglycolic acid electrospun nanofiber membrane wound dressing with high biocompatibility, hemostasis, and prevention of chronic wound formation

The prevention of chronic wound formation has already been a primary subject in wound management, particularly for deep wounds. The electrospun nanofiber membranes hold tremendous potential in the prevention of chronic wounds due to their micro/nano pore structures. Currently, many natural and synthetic materials have been utilized in the fabrication of nanofiber membranes. However, striking a balance between the structural stability and the biocompatibility remains challenging. It is necessary not only to ensure the long-term durability of nanofiber membranes but also to enhance their biocompatibility for alleviating patients' suffering. In this study, we reported a nanofiber membrane dressing with excellent biocompatibility and mechanical properties, which is potential for the treatment of deep wounds. The basal material chosen for the preparation of the nanofiber membrane was a co-polyester (NI-LPGD5) synthesized by non-isocyanate polyurethane (NIPU) and polyglycolic acid with a dihydroxy structure (LPGD-synthesized from glycolic acid and neopentyl glycol). Moreover, curcumin was also added as a bioactive substance to enhance the pro-healing effect of dressings. The physicochemical properties of the prepared nanofiber membranes were characterized through various physicochemical tools. Our results demonstrated that the NI-LPGD5 co-polymer can be electrospun into smooth fibers. Meanwhile, curcumin-loaded nanofiber membranes (Cur/NI-LPGD5) also exhibited a favorable microscopic morphology. The fabricated membranes exhibited suitable mechanical properties, outstanding hygroscopic-swelling rate and water vapor transmittance. Besides, in vitro cell culturing, the cells on the NI-LPGD5 membrane maintained their maximum viability. The potential of in vivo wound healing was further demonstrated through animal experiments. The experimental results showed that the nanofiber membranes effectively prevented chronic wounds from forming and promoted granulation tissue growth without replacing the dressing throughout the healing process. We also found that these nanofiber membranes could effectively promote the expression of related biomarkers to accelerate wound healing, particularly the Cur/NI-LPGD5 membrane. In conclusion, the fabricated membranes possess suitable physicochemical properties and promising bioactivity. As a result, it effectively prevented the formation of chronic wounds and demonstrated significant potential in reducing the frequency of dressing changes.

The mechanisms and functions of TGF-β1 in tendon healing

Tendon injury accounts for 30% of musculoskeletal diseases and often leads to disability, pain, healthcare cost, and lost productivity. Following injury to tendon, tendon healing proceeds via three overlapping healing processes. However, due to the structural defects of the tendon itself, the tendon healing process is characterized by the formation of excessive fibrotic scar tissue, and injured tendons rarely return to native tendons, which can easily contribute to tendon reinjury. Moreover, the resulting fibrous scar is considered to be a precipitating factor for subsequent degenerative tendinopathy. Despite this, therapies are almost limited because underlying molecular mechanisms during tendon healing are still unknown. Transforming Growth Factor-β1 (TGF-β1) is known as one of most potent profibrogenic factors during tendon healing process. However, blockage TGF-β1 fails to effectively enhance tendon healing. A detailed understanding of real abilities of TGF-β1 involved in tendon healing can bring promising perspectives for therapeutic value that improve the tendon healing process. Thus, in this review, we describe recent efforts to identify and characterize the roles and mechanisms of TGF-β1 involved at each stage of the tendon healing and highlight potential roles of TGF-β1 leading to the fibrotic response to tendon injury.

Effects of Low-Intensity Pulsed Ultrasound in Tendon Injuries

Tendon injuries are the most common soft tissue injuries, caused by tissue overuse and age-related degeneration. However, the tendon repair process is slow and inefficient due to the lack of cellular structure and blood vessels in the tendon. Low-intensity pulsed ultrasound (LIPUS) has received increasing attention as a non-invasive, simple, and safe way to promote tendon healing. This review summarizes the effects and underlying mechanisms of LIPUS on tendon injury by comprehensively examining the published literature, including in vitro, in vivo, and clinical studies. This review reviewed 24 studies, with 87.5% showing improvement. The application of LIPUS in tendon diseases is a promising field worthy of further study.

Neutralization of excessive levels of active TGF-β1 reduces MSC recruitment and differentiation to mitigate peritendinous adhesion

Peritendinous adhesion formation (PAF) can substantially limit the range of motion of digits. However, the origin of myofibroblasts in PAF tissues is still unclear. In this study, we found that the concentration of active TGF-β1 and the numbers of macrophages, mesenchymal stromal cells (MSCs), and myofibroblasts in human and mouse adhesion tissues were increased. Furthermore, knockout of TGF-β1 in macrophages or TGF-β1R2 in MSCs inhibited PAF by reducing MSC and myofibroblast infiltration and collagen I and III deposition, respectively. Moreover, we found that MSCs differentiated into myofibroblasts to form adhesion tissues. Systemic injection of the TGF-β-neutralizing antibody 1D11 during the granulation formation stage of PAF significantly reduced the infiltration of MSCs and myofibroblasts and, subsequently, PAF. These results suggest that macrophage-derived TGF-β1 recruits MSCs to form myofibroblasts in peritendinous adhesions. An improved understanding of PAF mechanisms could help identify a potential therapeutic strategy.

Up-regulation of CREB-1 regulates tendon adhesion in the injury tendon healing through the CREB-1/TGF-β3 signaling pathway

AIM

To explore the mechanism of the healing of tendon tissue and anti-adhesion, and to discuss the role of the transforming growth factor-β3 (TGF-β3)/cAMP response element binding protein-1 (CREB-1) signaling pathway in the healing process of tendons.

METHOD

All mice were divided into four groups of 1, 2, 4, and 8 weeks respectively. Each time group was divided into four treatment groups: the amplification group, the inhibition group, the negative group, and the control group. When the tendon injury model was established, the CREB-1 virus was injected into the tendon injury parts. A series of methods such as gait behaviourism, anatomy, histological examination, immunohistochemical examination and collagen staining were employed to assess the tendon healing and the protein expression of TGF-β3, CREB-1, Smad3/7 and type I/III collagen (COL-I/III). CREB-1 virus was sent to tendon stem cells to assess the protein expression of TGF-β1, TGF-β3, CREB-1, COL-I/III by methods such as immunohistochemistry and Western blot.

RESULTS

The amplification group showed better gait behaviourism than the inhibition group in the healing process. The amplification group also had less adhesion than the negative group. Hematoxylin-eosin (HE) staining of tendon tissue sections showed that the number of fibroblasts in the amplification group was less than the inhibition group, and the immunohistochemical results indicated that the expression of TGF-β3, CREB-1, and Smad7 at each time point was higher than the inhibition group. The expression of COL-I/III and Smad3 in the amplification group was lower than the inhibition group at all time points. The collagen staining indicated that the ratio of type I/III collagen in the amplification group was higher than the negative group at 2,4,8 week. The CREB-1 amplification virus could promote the protein expression of TGF-β3, CREB-1 and inhibit the protein expression of TGF-β1 and COL-I/III in the tendon stem cells.

CONCLUSION

In the process of tendon injury healing, CREB-1 could promote the secretion of TGF-β3, so as to promote the tendon healing and have the effect of anti-adhesion in tendons. It might provide new intervention targets for anti-adhesion treatment of tendon injuries.

TGF-β3 regulates adhesion formation through the JNK/c-Jun pathway during flexor tendon healing

BACKGROUND

The injured flexor tendon has poor healing ability, which is easy to cause tendon adhesion. It can affect the recovery of tendon function, which is still a long-term and difficult task for surgeons. Transforming growth factor β (TGF-β) has been widely considered to play an important role in flexor tendon repair in recent years.

AIM

This work was to investigate the anti-adhesion and anti-inflammatory effects of TGF-β3 on flexor digitorum longus (FDL) tendon repair rats.

METHOD

Anastomosis models of tendon laceration in the flexion toes of rats were delivered with no treatment, vehicle, or TGF-β3 -overexpressed adenovirus vector (ad-TGF-β3) locally to the injured tendon area from day 3 to 8. Subsequently, the expression of TGF-β3, TGF-β1/2, Smad3, Smad7, JNK, phosphorylation (p)-JNK, c-Jun, and phosphorylation (p)-c-Jun were detected by western blot, the expression of Mmp9 and Mmp2 by RT-qPCR, the Range of motion (ROM) and gliding resistance by adhesion formation testing, the mechanical strength of tendon healing by biomechanical testing, the pathologic changes of flexor tendon tissues by HE staining, the expression of collagen type III by immunohistochemical staining, and the levels of IL-6, TNF-α, COX2 and IL-1β in serum by ELISA, respectively.

RESULTS

Rat models treated with no treatment showed a lower elevation of TGF-β3 and Smad7 expression, and a higher elevation of TGF-β1/2 and Smad3 expression, during day 14 to day 28. Besides, under the treatment of ad-TGF-β3, a significantly increase was reflected in the expression of TGF-β3 and Smad7, ROM, as well as mechanical strength of flexor tendon, whereas significantly reduction was shown in gliding resistance, the content of inflammatory cytokines, the ratio of p-JNK/JNK, p-c-Jun/c-Jun, as well as the expression of TGF-β1/2, Smad3, Mmp9, and Mmp2 genes, as compared to those from vehicle treatment. Meanwhile, TGF-β3 demonstrated a better pathologic recovery process with no obvious necrosis or fracture of collagen fibers. Besides, TGF-β3 revealed a significant reduction of collagen type-III expression in the flexor tendon healing tissues.

CONCLUSION

These findings suggested that TGF-β3 effectively protected against flexor tendon injury via regulating adhesion formation.

Stem Cell Therapy for Tendon Regeneration: Current Status and Future Directions

In adults the healing tendon generates fibrovascular scar tissue and recovers never histologically, mechanically, and functionally which leads to chronic and to degenerative diseases. In this review, the processes and mechanisms of tendon development and fetal regeneration in comparison to adult defect repair and degeneration are discussed in relation to regenerative therapeutic options. We focused on the application of stem cells, growth factors, transcription factors, and gene therapy in tendon injury therapies in order to intervene the scarring process and to induce functional regeneration of the lesioned tissue. Outlines for future therapeutic approaches for tendon injuries will be provided.

Biologic and mechanical aspects of tendon fibrosis after injury and repair

Tendon injuries of the hand that require surgical repair often heal with excess scarring and adhesions to adjacent tissues. This can compromise the natural gliding mechanics of the flexor tendons in particular, which operate within a fibro-osseous tunnel system similar to a set of pulleys. Even combining the finest suture repair techniques with optimal hand therapy protocols cannot ensure predictable restoration of hand function in these cases. To date, the majority of research regarding tendon injuries has revolved around the mechanical aspects of the surgical repair (i.e. suture techniques) and postoperative rehabilitation. The central principles of treatment gleaned from this literature include using a combination of core and epitendinous sutures during repair and initiating motion early on in hand therapy to improve tensile strength and limit adhesion formation. However, it is likely that the best clinical solution will utilize optimal biological modulation of the healing response in addition to these core strategies and, recently, the research in this area has expanded considerably. While there are no proven additive biological agents that can be used in clinical practice currently, in this review, we analyze the recent literature surrounding cytokine modulation, gene and cell-based therapies, and tissue engineering, which may ultimately lead to improved clinical outcomes following tendon injury in the future.

Prevention of Peritendinous Adhesion Formation After the Flexor Tendon Surgery in Rabbits: A Comparative Study Between Use of Local Interferon-α, Interferon-β, and 5-Fluorouracil

BACKGROUND

Peritendinous adhesion is the most common complication after tendon surgery, particularly in zone II of the hand. Prevention of inflammation around the tendon, which develops after trauma and surgery, can decrease the tendon adhesion formation. This study compares the effect of some anti-inflammatory cytokines with 5-fluorouracil (5-FU) on the tensile strength and in prevention of peritendinous adhesion formation.

METHODS

Sixteen rabbits were allocated equally into 4 groups. Tendons of the index and ring fingers in zone II of the right hind paw were cut in all animals and then repaired. Interferon (IFN)-α in group 1, 5-FU in group 2, normal saline in group 3, and IFN-β in group 4 were locally applied to the repaired sites. Three weeks later, tensometric and histopathologic evaluations were performed.

RESULTS

The force required for removing the tendon from the sheath was not different between the groups (P = 0.130), but the time required for removal was significantly shorter in 5-FU group (P = 0.049). The strength of repair was not different between the groups in terms of force and time needed for rupture (P = 0.11 and 0.67, respectively). In histopathologic examination, normal architecture of the tendon and peritendon environment was less disturbed in the IFN groups, especially in IFN-β specimens.

CONCLUSIONS

Local application of 5-FU significantly reduced peritendinous adhesion. Local IFN-α and IFN-β had no significant effect on the prevention of peritendinous adhesion formation. The strength of the repair was not affected by these cytokines and 5-FU.

Differential expression of extracellular matrix genes in glenohumeral capsule of shoulder instability patients

Anterior shoulder instability is a common orthopedic problem. After a traumatic shoulder dislocation, patients present a plastic deformation of the capsule. The shoulder instability biology remains poorly understood. We evaluated the expression of genes that encode the cartilage oligomeric matrix protein (COMP), fibronectin 1 (FN1), tenascin C (TNC) and tenascin XB (TNXB) in the glenohumeral capsule of anterior shoulder instability patients and controls. Moreover, we investigated the associations between gene expression and clinical parameters. The gene expression was evaluated by quantitative reverse transcription-polymerase chain reaction in the antero-inferior (macroscopically injured region), antero-superior and posterior regions of the capsule of 29 patients with shoulder instability and 8 controls. COMP expression was reduced and FN1 and TNC expression was increased in the antero-inferior capsule region of cases compared to controls (p < 0.05). TNC expression was increased in the posterior capsule portion of shoulder instability patients (p = 0.022). COMP expression was reduced in the antero-inferior region compared to the posterior region of shoulder instability patients (p = 0.007). In the antero-inferior region, FN1 expression was increased in the capsule of patients with more than one year of symptoms (p = 0.003) and with recurrent dislocations (p = 0.004) compared with controls. FN1 and TNXB expression was correlated with the duration of symptoms in the posterior region (p < 0.05). Thus, COMP, FN1, TNC and TNXB expression was altered across the capsule of shoulder instability patients. Dislocation episodes modify FN1, TNC and TNXB expression in the injured tissue. COMP altered expression may be associated with capsule integrity after shoulder dislocation, particularly in the macroscopically injured portion.

Restoration of the pubourethral ligament with platelet rich plasma for the treatment of stress urinary incontinence

Stress urinary incontinence (SUI) is a major health problem, which affects nearly 20% of adult women and has a detrimental impact on their daily activities and quality of life. Several surgical techniques have been proposed for the treatment of SUI including the Burch colposuspension, retropubic mid-urethral slings (TVT), trans-obturator tapes (TOT), trans-obturator tapes inside out (TVT-O), bladder neck injections and the insertion of an artificial urethral sphincter. All of these treatments aim to either restore the urethral support, which is naturally preserved by the pubourethral ligament (PUL) or to increase the urethral resistance at rest. Most surgical techniques are associated with a variety of intraoperative and postoperative complications. Platelet rich plasma (PRP) is extremely rich in growth factors and cytokines, which regulate tissue reconstruction and has been studied extensively among trauma patients and trauma experimental models. To date, however, there is no evidence to support or oppose its use in women who suffer from SUI due to PUL damage. PRP is an easily produced and relatively inexpensive biologic material. It is produced directly from the patient's blood and is, thus, superior to synthetic materials in terms of potential adverse effects such as from foreign body reaction. In the present article we summarize the existing evidence in the field, which supports the conduct of animal experimental and clinical studies to elucidate the potential role of PRP in treating SUI.

Recent Scientific Advances Towards the Development of Tendon Healing Strategies

There exists a range of surgical and non-surgical approaches to the treatment of both acute and chronic tendon injuries. Despite surgical advances in the management of acute tears and increasing treatment options for tendinopathies, strategies frequently are unsuccessful, due to impaired mechanical properties of the treated tendon and/or a deficiency in progenitor cell activities. Hence, there is an urgent need for effective therapeutic strategies to augment intrinsic and/or surgical repair. Such approaches can benefit both tendinopathies and tendon tears which, due to their severity, appear to be irreversible or irreparable. Biologic therapies include the utilization of scaffolds as well as gene, growth factor, and cell delivery. These treatment modalities aim to provide mechanical durability or augment the biologic healing potential of the repaired tissue. Here, we review the emerging concepts and scientific evidence which provide a rationale for tissue engineering and regeneration strategies as well as discuss the clinical translation of recent innovations.

Biologics for tendon repair

Tendon injuries are common and present a clinical challenge to orthopedic surgery mainly because these injuries often respond poorly to treatment and require prolonged rehabilitation. Therapeutic options used to repair ruptured tendons have consisted of suture, autografts, allografts, and synthetic prostheses. To date, none of these alternatives has provided a successful long-term solution, and often the restored tendons do not recover their complete strength and functionality. Unfortunately, our understanding of tendon biology lags far behind that of other musculoskeletal tissues, thus impeding the development of new treatment options for tendon conditions. Hence, in this review, after introducing the clinical significance of tendon diseases and the present understanding of tendon biology, we describe and critically assess the current strategies for enhancing tendon repair by biological means. These consist mainly of applying growth factors, stem cells, natural biomaterials and genes, alone or in combination, to the site of tendon damage. A deeper understanding of how tendon tissue and cells operate, combined with practical applications of modern molecular and cellular tools could provide the long awaited breakthrough in designing effective tendon-specific therapeutics and overall improvement of tendon disease management.

Application of stem cells derived from the periodontal ligament or gingival tissue sources for tendon tissue regeneration

Tendon injuries are often associated with significant dysfunction and disability due to tendinous tissue's very limited self-repair capacity and propensity for scar formation. Dental-derived mesenchymal stem cells (MSCs) in combination with appropriate scaffold material present an alternative therapeutic option for tendon repair/regeneration that may be advantageous compared to other current treatment modalities. The MSC delivery vehicle is the principal determinant for successful implementation of MSC-mediated regenerative therapies. In the current study, a co-delivery system based on TGF-β3-loaded RGD-coupled alginate microspheres was developed for encapsulating periodontal ligament stem cells (PDLSCs) or gingival mesenchymal stem cells (GMSCs). The capacity of encapsulated dental MSCs to differentiate into tendon tissue was investigated in vitro and in vivo. Encapsulated dental-derived MSCs were transplanted subcutaneously into immunocompromised mice. Our results revealed that after 4 weeks of differentiation in vitro, PDLSCs and GMSCs as well as the positive control human bone marrow mesenchymal stem cells (hBMMSCs) exhibited high levels of mRNA expression for gene markers related to tendon regeneration (Scx, DCn, Tnmd, and Bgy) via qPCR measurement. In a corresponding in vivo animal model, ectopic neo-tendon regeneration was observed in subcutaneous transplanted MSC-alginate constructs, as confirmed by histological and immunohistochemical staining for protein markers specific for tendons. Interestingly, in our quantitative PCR and in vivo histomorphometric analyses, PDLSCs showed significantly greater capacity for tendon regeneration than GMSCs or hBMMSCs (P < 0.05). Altogether, these findings indicate that periodontal ligament and gingival tissues can be considered as suitable stem cell sources for tendon engineering. PDLSCs and GMSCs encapsulated in TGF-β3-loaded RGD-modified alginate microspheres are promising candidates for tendon regeneration.

The growth factors involved in flexor tendon repair and adhesion formation

Flexor tendon injuries remain a significant clinical problem, owing to the formation of adhesions or tendon rupture. A number of strategies have been tried to improve outcomes, but as yet none are routinely used in clinical practice. Understanding the role that growth factors play in tendon repair should enable a more targeted approach to be developed to improve the results of flexor tendon repair. This review describes the main growth factors in tendon wound healing, and the role they play in both repair and adhesion formation.

A new TGF-β3 controlled-released chitosan scaffold for tissue engineering synovial sheath

The post-operative outcome of flexor tendon healing remains limited by flexor tendon adhesion that reduces joint range of motion. Despite improvement in different methods, peritendinous adhesion formation continues to present a formidable challenge. Recent studies showed that transforming growth factor-β3 (TGF-β3) may be the key factor to reducing adhesion formation in skin or tendon. In this study, we designed a novel type of tissue engineering synovial sheath containing TGF-β3, to prevent flexor tendon adhesion. First, to achieve a stable release of TGF-β3, chitosan microspheres, prepared by crosslinking-emulsion, were used for the delivery of TGF-β3. Second, a three-dimensional chitosan scaffold was prepared by lyophilization, and TGF-β3 microspheres were carefully introduced into the scaffold. Then, synovial cells were cultured and then seeded into the TGF-β3 loaded scaffold to produce TGF-β3 controlled-released tissue engineering synovial sheath. Tests clearly demonstrated that the scaffold has good structure and compatibility with cells. These results expand the feasibility of combinative strategies of controlled protein release and tissue-engineered synovial sheath formation. Application of this scaffold to tendon repair sites may help to prevent adhesion of tendon healing.

Managing the injured tendon: current concepts

Despite advances in understanding of the mechanical aspects of tendon management with improved suture technique and early stress application with postoperative therapy, clinical results remain inconsistent after repair, especially within the synovial regions. Complementary research to enhance the intrinsic pathway of healing, suppress the extrinsic pathway of healing, and manipulate frictional resistance to tendon gliding is now the focus of current basic science research on tendons. In the future, application of these new biologic therapies may increase the "safety zone" (or tolerance for load and excursion without dysfunctional gapping) as therapists apply stress to healing tendons and may alter future rehabilitation protocols by allowing greater angles of motion (and thus tendon excursion), increased external load, and decreased time in protective orthoses (splints). However, at this time, the stronger repair techniques and the application of controlled stress remain the best and most well-supported intervention after tendon injury and repair in the recovery of functional tendon excursion and joint range of motion. The hand therapist's role in this process remains a critical component contributing to satisfactory outcomes.

Tendon healing in vivo: effect of mannose-6-phosphate on flexor tendon adhesion formation

The purpose of this study was to investigate the preventive effect of mannose-6-phosphate on flexor tendon adhesion formation. From a total of 84 adult New Zealand White rabbits, 36 were randomly divided into 2 groups, the normal saline group and the mannose-6-phosphate group, after anastomosis of the flexor tendons. Tendons were harvested at 4 weeks, and biomechanics testing was conducted. The other 48 rabbits were randomly divided into 2 groups, the normal saline group and the mannose-6-phosphate group, after anastomosis of the flexor tendons, and tendons were harvested at 7, 14, 28, and 56 days and analyzed by in situ hybridization to determine the mRNA expression of transforming growth factor (TGF)-β1 and collagen I. The results of biomechanics testing indicated that mannose-6-phosphate can effectively prevent flexor tendon adhesion formation after anastomonsis. The in situ hybridization examination revealed that TGF-β1 and collagen I mRNA expression in the mannose-6-phosphate group was lower than that in the normal saline group at each time point. Mannose-6-phosphate can effectively inhibit the function of TGF-β1 and prevent adhesion formation after flexor tendon injury.

Achilles tendon regeneration can be improved by amniotic epithelial cell allotransplantation

Amniotic epithelial cells (AECs) are ideal seed cells for tissue regeneration, but no research has yet been reported on their tendon regeneration potential. This study investigated the efficiency of AEC allotransplantation for tendon healing, as well as the mechanism involved. To this aim ovine AECs, characterized by specific surface and stemness markers (CD14(-), CD31(-), CD45(-), CD49f, CD29, CD166, OCT4, SOX2, NANOG, TERT), were allotransplanted into experimentally induced tissue defects in sheep Achilles tendon. In situ tissue repair revealed that AEC-treated tendons had much better structural and mechanical recoveries than control ones during the early phase of healing. Immunohistochemical and biochemical analyses indicated that extracellular matrix remodeling was more rapid and that immature collagen fibers were completely replaced by mature ones in 28 days. Moreover, spatial-temporal analysis of cellularity, proliferation index, vascular area, and leukocyte infiltration revealed that AECs induced a specific centripetal healing process that first started in the tissue closer to the healthy portion of the tendons, where AECs rapidly migrated to then progress through the core of the lesion. This peculiar healing evolution could have been induced by the growth factor stimulatory influence (TGF-β1 and VEGF) and/or by the host progenitor cells recruitment, but also as the consequence of a direct tenogenic AEC differentiation resulting in the regeneration of new tendon matrix. These findings demonstrate that AECs can support tendon regeneration, and their effects may be used to develop future strategies to treat tendon disease characterized by a poor clinical outcome in veterinary medicine.

Inhibition effect of mannose-6-phosphate on expression of transforming growth factor Beta receptor in flexor tendon cells

Transforming growth factor beta (TGF-β) has an important role in tendon healing and adhesion formation. Inhibiting TGF-β and its receptor expression may prevent adhesions after tendon open. The goal of this study was to examine the effects of mannose-6-phosphate, a natural inhibitor of TGF-β, on TGF-β and its receptor production in tendon sheath fibroblasts, epitenon tenocytes, and endotenon tenocytes of rabbit flexor tendons. Tendon sheath fibroblasts, epitenon tenocytes, and endotenon tenocytes were isolated from rabbit flexor tendons and cultured separately. The cells were divided into 2 groups at random: an experiment group supplemented with mannose-6-phosphate and a control group without mannose-6-phosphate. The expression of TGF-β and TGF-β receptor was quantified with enzyme-linked immunosorbent assay. The luciferase assay measured TGF-β bioactivity. Transforming growth factor beta expression in the experimental group was not decreased compared with the control group, with no significant difference (P>.05) Transforming growth factor beta receptor expression in the experiment group was significantly lower than that in control group (P<.05). Mannose-6-phosphate significantly decreased the expression of TGF-β receptor and TGF-β bioactivity. Modulation of mannose-6-phosphate levels may provide a means of modulating the effects of TGF-β on adhesion formation in flexor tendon wound healing.

Tissue engineered biological augmentation for tendon healing: a systematic review

INTRODUCTION

Tendon injuries give rise to significant morbidity. In the last few decades, several techniques have been increasingly used to optimize tendon healing.

SOURCES OF DATA

We performed a comprehensive search of PubMed, Medline, Cochrane, CINAHL and Embase databases using various combinations of the commercial names of each scaffold and the keywords 'tendon', 'rotator cuff', 'supraspinatus tendon', 'Achilles tendon', 'growth factors', 'cytokines', 'gene therapy', 'tissue engineering', 'mesenchymal' and 'stem cells' over the years 1966-2009. All articles relevant to the subject were retrieved, and their bibliographies were hand searched for further references in the context to tissue-engineered biological augmentation for tendon healing.

AREAS OF AGREEMENT

Several new techniques are available for tissue-engineered biological augmentation for tendon healing, growth factors, gene therapy and mesenchimal stem cells.

AREAS OF CONTROVERSY

Data are lacking to allow definitive conclusions on the use of these techniques for routine management of tendon ailments.

GROWING POINTS

The emerging field of tissue engineering holds the promise to use new techniques for tendon augmentation and repair. Preliminary studies support the idea that these techniques can provide an alternative for tendon augmentation with great therapeutic potential.

AREAS TIMELY FOR DEVELOPING RESEARCH

The optimization strategies discussed in this article are currently at an early stage of development. Although these emerging technologies may develop into substantial clinical treatment options, their full impact needs to be critically evaluated in a scientific fashion.

Tendon healing in vivo and in vitro: neutralizing antibody to TGF-β improves range of motion after flexor tendon repair

Adhesion formation between the flexor tendon and its surrounding fibro-osseous sheath results in a decreased postoperative range of motion (ROM) in the hand. Transforming growth factor-beta (TGF-β) is a key cytokine in the pathogenesis of tissue fibrosis. In this study, the effects of TGF-β1 neutralizing antibody were investigated in vitro and in vivo. In the in vitro investigation, primary cell cultures from rabbit flexor tendon sheath, epitenon, and endotenon were established and each was supplemented with TGF-β along with increasing doses of TGF-β1 neutralizing antibody. Collagen I production was measured with enzyme-linked immunosorbent assay. In the in vivo study, rabbit zone-II flexor tendons were transected and then immediately repaired. Transforming growth factor-β1 neutralizing antibody or phosphate-buffered saline solution (control) was added to the repair sites, and the forepaws were tested for ROM and repair strength at 8 weeks postoperatively. Transforming growth factor-β1 neutralizing antibody reduced TGF-β upregulated collagen production. Intraoperative application of TGF-β1 neutralizing antibody significantly improved the ROM of the operatively treated digits. The effect on breaking strength of the tendon repair was inconclusive.