Effects of basic fibroblast growth factor (bFGF) on early stages of tendon healing: a rat patellar tendon model

Tendon: biology, biomechanics, repair, growth factors, and evolving treatment options

Surgical treatment of tendon ruptures and lacerations is currently the most common therapeutic modality. Tendon repair in the hand involves a slow repair process, which results in inferior repair tissue and often a failure to obtain full active range of motion. The initial stages of repair include the formation of functionally weak tissue that is not capable of supporting tensile forces that allow early active range of motion. Immobilization of the digit or limb will promote faster healing but inevitably results in the formation of adhesions between the tendon and tendon sheath, which leads to friction and reduced gliding. Loading during the healing phase is critical to avoid these adhesions but involves increased risk of rupture of the repaired tendon. Understanding the biology and organization of the native tendon and the process of morphogenesis of tendon tissue is necessary to improve current treatment modalities. Screening the genes expressed during tendon morphogenesis and determining the growth factors most crucial for tendon development will likely lead to treatment options that result in superior repair tissue and ultimately improved functional outcomes.

PDGF-BB released in tendon repair using a novel delivery system promotes cell proliferation and collagen remodeling

The purpose of this study was to promote fibroblast proliferation and collagen remodeling in flexor tendon repair through sustained delivery of platelet derived growth factor (PDGF-BB). The release kinetics of PDGF-BB from a novel fibrin matrix delivery system was initially evaluated in vitro. After the in vivo degradation rate of the fibrin matrix was determined using fluorescently tagged fibrin, PDGF-BB was delivered to the site of flexor tendon repair in vivo in a canine model. The effect of PDGF-BB on intrasynovial tendon healing was studied using histology-based assays (cell density, proliferation, and type I collagen expression) and by measuring total DNA levels and reducible collagen crosslink levels. The fibrin matrix delivery system provided sustained release of PDGF-BB in vitro at a rate modulated by the ratio of heparin to growth factor. In vivo, the fibrin matrix remained at the repair site for more than 10 days. Delivery of PDGF-BB led to a qualitative increase in cell density, cell proliferation, and type I collagen mRNA expression. PDGF-BB also led to statistically significant increases in total DNA (20% increase at 7 days, 18% increase at 14 days) and reducible collagen crosslinks (30% increase at 7 days). Sustained delivery of growth factors may be achieved using a novel fibrin-based delivery system. PDGF-BB delivery increased cell proliferation and matrix remodeling and thus may accelerate flexor tendon healing.

Modifications of the fibroblast growth factor-2 gene led to a marked enhancement in secretion and stability of the recombinant fibroblast growth factor-2 protein

Progress in FGF-2 gene therapy has been hampered by the difficulty in achieving therapeutic levels of FGF-2 secretion. This study tested whether the addition of BMP2/4 hybrid secretion signal to the FGF-2 gene and mutation of cys-70 and cys-88 to serine and asparagine, respectively, would increase the stability and secretion of active FGF-2 protein in mammalian cells using MLV-based vectors. Single or double mutations of cys-70 and cys-88 to ser-70 and asp-88, respectively, markedly increased the amounts of FGF-2 protein in conditioned media and cell lysates, which may be due to glycosylation, particularly at the mutated asp-88 residue. Addition of BMP2/4 secretion signal increased FGF-2 secretion, but also suppressed FGF-2 biosynthesis. The combination of BMP2/4 secretion signal and double cys-70 and cys-88 mutations increased the total amount of secreted FGF-2 protein >60-fold. The modifications did not alter its ability to stimulate cell proliferation and Erk1/2 phosphorylation in marrow stromal cells or its ability to bind heparin in vitro, suggesting that the modified FGF-2 protein was functionally as effective as the unmodified FGF-2. An ex vivo application of rat skin fibroblasts (RSF) transduced with the modified FGF-2 vector in a subcutaneous implant model showed that rats with implants containing cells transduced with the modified FGF-2 vector increased serum FGF-2 level >15-fold, increased growth of the implant, and increased vascularization within the implant, compared to rats that received implants containing beta-galactosidase- or wild-type FGF-2-transduced control cells. This modified vector may be useful in FGF-2 gene therapy investigations.

Stimulation of tendon repair: mechanical loading, GDFs and platelets. A mini-review

The repair of subcutaneous tendon ruptures can be stimulated by a single application of one of several growth factors [e.g. platelet-derived growth factor (PDGF), transforming growth factor (TGF)-beta, insulin-like growth factor (IGF)-1, vascular endothelial growth factor (VEGF), bone morphogenetic proteins (BMPs) like growth differentiation factor (GDF)-5, -6, -7] or by a thrombocyte concentrate (PRP). The response to these measures is dependent on the mechanical microenvironment, which is crucial for repair. So far, almost all research has been limited to rodent models, mostly using the rat Achilles tendon. Ruptured human Achilles tendons appear to be mechanically loaded in spite of immobilisation. This suggests that the mechanical microenvironment might be favourable for the clinical use of growth factors or platelets for this indication. New methods to quantitate human Achilles tendon repair have been developed.

Repair of experimental Achilles tenotomy with porcine renal capsule material in a rat model

Porcine small intestinal submucosa (SIS) is a collagenous acellular matrix which has found substantial utility as a tissue growth scaffold. In the present study, the utility of porcine renal capsule matrix (RCM) was compared to SIS in a rat Achilles tenotomy repair model. Groups of rats underwent surgical tenotomy followed by either no repair, repair with a SIS graft, or repair with a RCM graft. The weight-bearing ability of the manipulated limb was evaluated for 10 days following surgery using a subjective scale. Tenotomy sites sampled 28 days after surgery were numerically graded for degree of histologic change. There were no statistically significant differences between groups with respect to return to weight-bearing ability (p >or= 0.05) or degree of histologic change (p >or= 0.001); however, a non-significant trend suggested that rats treated with SIS or RCM experienced a faster return to limb function than untreated rats, and RCM-treated rats had slightly higher scores for degree of histologic change, suggesting a more rapid repair of the tenotomy site than in SIS-treated or untreated rats. The harvested tenotomy sites in all treatment groups were characterized by marked fibroplasia and presence of macrophages. Remnants of SIS surrounded by macrophages and multi-nucleated giant cells were still present in some rats, however remnants of RCM were not observed, suggesting more rapid incorporation of RCM. The results show that RCM is equivalent to SIS as a material for repair of Achilles tendon injury and merits further study in other tendon injury models.

Tendon and ligament engineering: from cell biology to in vivo application

Tendons and ligaments are related connective tissues that join muscle to bone and bone to bone, respectively. Tendon and ligament injuries are widely distributed clinical problems in society and while healing of such disorders can occur, the original biological properties of the tissue do not return to normal. In this review, recent work on tendon and ligament development and the use of growth factors for successful cellular therapy of tendon and ligament disorders are discussed. In addition, anti-inflammatory concepts for the treatment of tendon and ligament injuries and recent developments in stem cell engineering for tendon and ligament tissues are examined. Lastly, gene transfer strategies for therapeutic applications to heal tendon and ligament disorders are reviewed.

Mechanical Conditioning of Cell-Seeded Small Intestine Submucosa: A Potential Tissue-Engineering Strategy for Tendon Repair

Our long-term objective is to enhance tendon repair by delivering cells on natural biologic scaffolds to the repair site. Clinical outcomes may be improved by first preconditioning these cell-seeded constructs in bioreactors to enhance their properties at implantation and to deliver cells expressing a desired phenotype. In this work, we have investigated the effect of in vitro mechanical conditioning on small-intestine submucosa (SIS) scaffolds seeded with primary tendon cells (tenocytes). SIS scaffolds (with and without cells) were conditioned under various loading regimes over a 2-week period. In vitro cyclic loading significantly increased the biomechanical properties (e.g., stiffness) of cell-seeded SIS constructs (129.1 +/- 10.2%) from time 0. The stiffness change of cyclically loaded constructs without cells was 33.9 +/- 13.8% and of statically loaded constructs with cells was 34.0 +/- 15.2% and without cells was 33.4 +/- 10.7%. In the cell-seeded groups, our data demonstrate a direct role (e.g., cell tensioning) for cells in construct stiffening. In addition, the initial stiffness of the cell-seeded, cyclically loaded constructs was found to be a strong predictor of the change in construct stiffness. Despite the mechanical integrity of these constructs being significantly less than native tendon, our data show that structural properties can be improved with in vitro mechanical conditioning. These data provide the basis for future studies investigating in vitro conditioning (mechanical, chemical) of cell-seeded ECM scaffolds and the use of such constructs for enhancing tendon repair in vivo.

Comparison of surgically repaired Achilles tendon tears using platelet-rich fibrin matrices

BACKGROUND

Platelet-rich fibrin matrices release a natural mixture of growth factors that play central roles in the complex processes of tendon healing.

HYPOTHESIS

Application of autologous platelet-rich matrices during Achilles tendon surgery may promote healing and functional recovery.

STUDY DESIGN

Case-control study and descriptive laboratory study; Level of evidence, 3.

METHODS

Twelve athletes underwent open suture repair after complete Achilles tendon tear. Open suture repair in conjunction with a preparation rich in growth factors (PRGF) was performed in 6 athletes and retrospectively compared with a matched group that followed conventional surgical procedure. The outcomes were evaluated on the basis of range of motion, functional recovery, and complications. Achilles tendons were examined by ultrasound at 50 +/- 11 months in retrospective controls and 32 +/- 10 months in the PRGF group. In the laboratory portion of the study, PRGF treatment was characterized by the number of platelets and concentration of insulin (IGF-I), transformed (TGF-beta1), platelet-derived (PDGF-AB), vascular endothelial (VEGF), hepatocyte (HGF), and epidermal (EGF) growth factors in patients affected by musculoskeletal traumatic injuries.

RESULTS

Athletes receiving PRGF recovered their range of motion earlier (7 +/- 2 weeks vs 11 +/- 3 weeks, P = .025), showed no wound complication, and took less time to take up gentle running (11 +/- 1 weeks vs 18 +/- 3 weeks, P = .042) and to resume training activities (14 +/- 0.8 weeks vs 21 +/- 3 weeks, P = .004). The cross-sectional area of the PRGF-treated tendons increased less (t = 3.44, P = .009). TGF-beta1 (74.99 +/- 32.84 ng/mL), PDGF-AB (35.62 +/- 14.57 ng/mL), VEGF (383.9 +/- 374.9 pg/mL), EGF (481.5 +/- 187.5 pg/mL), and HGF (593.87 +/- 155.76 pg/mL) significantly correlated with the number of platelets (677 +/- 217 platelets/microL, P < .05).

CONCLUSION

The operative management of tendons combined with the application of autologous PRGF may present new possibilities for enhanced healing and functional recovery. This needs to be evaluated in a randomized clinical trial.

Tendon Healing In Vitro: Adeno-Associated Virus-2 Effectively Transduces Intrasynovial Tenocytes with Persistent Expression of the Transgene, but Other Serotypes Do Not

BACKGROUND

Transfer of exogenous growth factor genes to injured tendons offers a promising method for strengthening tendon repairs. Adeno-associated virus vectors have advantages of being both nonpathogenic and nontoxic. The authors explored the efficiency of transduction of intrasynovial tenocytes with different serotypes of adeno-associated virus (AAV) and the persistency of its expression of a growth factor transgene.

METHODS

Tenocytes were obtained from cultures of rat intrasynovial tendons and distributed to 82 wells in eight culture plates and to 30 culture dishes. The tenocytes in the wells were treated with AAV1, AAV2, AAV3, AAV4, AAV5, AAV7, and AAV8 vectors containing the lacZ gene, and plasmid vectors (pCMVbeta-lacZ). The tenocytes were stained with in situ beta-galactosidase 5 days later. The basic fibroblast growth factor (bFGF) gene was cloned to the AAV2 vector to construct the AAV2-bFGF vector, which transduced tenocytes in culture dishes. Expression of the transgene was measured over 3 weeks and analyzed statistically.

RESULTS

AAV2 effectively delivered exogenous genes to proliferating intrasynovial tenocytes. In contrast, other tested adeno-associated viruses transduced tenocytes minimally or not at all. The efficiency of gene transfer by AAV2, indicated by the percentage of cells with positive beta-galactosidase staining, was significantly greater than that by a plasmid vector (p = 0.001). Expression of the bFGF gene in tenocytes transduced with the AAV2-bFGF was significantly higher than that in the control over the 3-week period (p < 0.01).

CONCLUSIONS

Gene transfer to tenocytes by AAV2 is more efficient than that by a plasmid vector. However, other adeno-associated virus serotypes cannot effectively transduce tenocytes. The bFGF gene can be delivered to intrasynovial tenocytes by the AAV2 vector effectively, and the gene transfer significantly increases expression of bFGF gene over 3 weeks.

Independent and additive stimulation of tendon repair by thrombin and platelets

BACKGROUND

Platelet concentrate application with added thrombin improves Achilles tendon repair in the rat. Upon tissue injury, platelets are activated by thrombin, which has many biological properties in common with growth factors. We wanted to differentiate the effect of platelets from that of thrombin.

METHODS

The Achilles tendon was transected in 50 rats. Platelet gel was prepared from the blood of 10 other rats. The rats were given either platelet gel with active or neutralized thrombin implanted into the defect during the operation, or a local injection 6h postoperatively with 50 microL of either platelet concentrate, thrombin or saline. The rats were killed after 14 days and the tendons were mechanically tested.

RESULTS

Compared to saline, platelet gel caused a 42% increase in force at failure, a 90% increase in energy, and a 61% increase in ultimate stress. Platelet gel with neutralized thrombin caused a 22% increase in force at failure, and energy and stress were less elevated. Injected platelet concentrate caused a 24% increase in force at failure, and thrombin caused a 10% increase. These effects and the differences between treatments were statistically significant.

INTERPRETATION

Platelets and thrombin had independent and additive stimulatory effects on tendon repair. The clinical relevance is so far unknown.

Tissue engineering for tendon repair

Tissue engineering aims to induce tissue self-regeneration in vivo or to produce a functional tissue replacement in vitro to be then implanted in the body. To produce a viable and functional tendon, a uniaxially orientated collagen type I matrix has to be generated. Biochemical and physical factors can potentially alter both the production and the organisation of this matrix, and their combination in a dose- and time-dependent manner is probably the key to in vitro engineered tendons. This review discusses the role of these different factors affecting tenocyte growth in a three-dimensional environment in vivo and in vitro, and underlines the future challenge of tendon tissue engineering.

Patterns of mRNA expression for matrix molecules and growth factors in flexor tendon injury: differences in the regulation between tendon and tendon sheath

PURPOSE

Injuries to tendons, particularly flexor tendons, can lead to loss of function after healing due to adhesion formation and other complications. The aim of this study was to increase our understanding of the healing process in tendons and tendon sheaths to develop methods to affect the healing process and improve the outcome of tendon repair in the future.

METHODS

In a rabbit model of flexor tendon injury, tissues were harvested 3, 6, 12, and 24 days after surgery (n = 6 for each group). After RNA extraction, messenger RNA (mRNA) levels for relevant genes in tendon and tendon sheaths were measured using the reverse transcription polymerase chain reaction. Messenger RNA levels for a subset of relevant molecules at different time points after injury were compared with those of uninjured controls for tendons and tendon sheaths.

RESULTS

Initially after injury, there was a shift in collagen expression with a marked increase in type III mRNA levels in both the tendon and tendon sheath, whereas those for collagen I increased only in the sheath at later time points. Aggrecan and versican mRNA levels were increased in both tissues, but temporal aspects of the changes were different. The mRNA levels for biglycan and lumican were all upregulated throughout the healing interval examined, whereas those for decorin were significantly decreased throughout in the tendon more so than the sheath. The mRNA levels for basic fibroblastic growth factor and transforming growth factor beta were elevated after injury in the tendon but not in the sheath. In contrast, mRNA levels for connective tissue growth factor were unaltered or decreased in both tissues throughout the interval assessed.

CONCLUSIONS

Healing after injury to the rabbit flexor tendon and tendon sheath follow a reproducible pattern of gene expression; however, the pattern in the tendon is very different from that in the sheath. These findings indicate that interventions developed to improve healing of these tissues will have to address these differences, because they will likely affect the outcomes.

Tissue engineering of flexor tendons: optimization of tenocyte proliferation using growth factor supplementation

A significant problem in flexor tendon repair is the lack of suitable graft material for reconstruction. The ex vivo production of flexor tendon graft constructs requires the expansion of primary cells. Growth factors, such as platelet-derived growth factor-BB (PDGF-BB), insulin-like growth factor-1 (IGF-1), and basic fibroblast growth factor (bFGF), are known to promote tendon healing and tendon cell proliferation. The purpose of these experiments was to optimize tenocyte proliferation in 3 tendon cell populations using growth factor supplementation. Cells of the synovial sheath, epitenon, and endotenon were isolated from rabbit flexor digitorum profundus tendons and maintained in culture. Cell cultures were supplemented with IGF-1, PDGF-BB, and bFGF alone and in combination. The conditions used for individual growth factor supplementation were IGF-1 (10, 50, and 100 ng/mL), PDGF-BB (1, 10, and 50 ng/mL), and bFGF (0.5, 1, and 5 ng/mL). The conditions used for combinations of growth factors were IGF-1 + PDGF-BB (50 + 10 and 100 + 50 ng/mL, respectively) and IGF-1 + PDGF-BB+ bFGF (50 + 10 + 1; 50 + 10 + 5; 100 + 50 + 1; and 100 + 50 + 5 ng/mL, respectively). For all 3 tendon cell populations, proliferation at 72 h was greater in the presence of individual growth factors as compared to controls. With PDGF-BB (50 ng/mL) supplementation, mean absorbance values increased 97% (0.57 to 1.13) in S cells, 37% (0.51 to 0.70) in E cells, and 33% (0.33 to 0.44) in T cells ( p < 0.001). In addition, a synergistic effect was observed. The combination of growth factors resulted in greater proliferation as compared to maximal doses of individual growth factors. In cultures supplemented with IGF-1 (100 ng/mL) +PDGF-BB (50 ng/mL), mean absorbance increased 114% (0.57 to 1.22) in S cells, 63% (0.51 to 0.831) in E cells, and 47% (0.33 to 0.48) in T cells ( p < 0.001). IGF-1 (100 ng/mL) + PDGF-BB (50 ng/mL) + bFGF (5 ng/mL) resulted in the greatest amount of cell proliferation for all 3 tendon cell populations. The mean absorbances increased 251% in S cells, 98% in E cells, and 106% in T cells ( p < 0.001). In summary, IGF-1, PDGF-BB, and bFGF can be used in combination to maximize tenocyte proliferation. Synergism among growth factors may provide a means to facilitate tendon engineering.

Supplementation-time dependence of growth factors in promoting tendon healing

Growth factors potentially promote tendon healing. Understanding the right time to administer growth factors and the dosage of growth factors are prerequisites for designing effective cytokine therapy. We investigated the supplementation-time dependence of the effects of platelet-derived growth factor isoform B at various dosages on tendon healing, and the temporal responsiveness of healing tendon toward platelet-derived growth factor. Platelet-derived growth factor isoform B at various dosages (0, 10, 100, or 1000 ng) was delivered into the gap wound of rat patellar tendons via microsyringe injection on Day 3 or Day 7 after injury. Tendon specimens were harvested on Day 14 for measurement of cell proliferation, pyridinoline content, and mechanical properties. We found increased proliferative response only when the growth factor was supplemented on Day 3 after injury, whereas supplementation on Day 7 resulted in greater peak load, cross-sectional area, and pyridinoline content. The ultimate stress did not change. Our findings suggest supplementation of platelet-derived growth factor isoform B at Day 7 benefits the mechanical properties and maturation of healing tendons. We also found platelet-derived growth factor receptor beta expressing cells at the remodeling site as much as 6 months after injury, suggesting healing tendon also may be responsive to long-term delivery of platelet-derived growth factor.

Tendon tissue engineering and gene transfer: the future of surgical treatment

Technologic improvements in the field of tissue engineering are leading to new potential developments in the currently used approaches to treat tendon injuries including difficult clinical scenarios such as zone II flexor tendon injuries of the hand and the mutilated hand with extensive tendon defects. A combination of mesenchymal (adult stem) cells, growth factors, and bioresorbable polymers can provide a solution for the treatment of difficult tendon injuries. Extensive research is needed to show that the extracellular matrix produced in response to the cell/growth factor/polymer composites in vivo is effective and functional as a regenerate tissue. Further exciting advances are foreseen in cell-based genetic engineering with the transfer of DNA to the site of tendon lacerations. These treatment modalities require improved safety precautions to reduce the risks and enhance the benefits of gene therapy.

Expression of growth factors in the early phase of supraspinatus tendon healing in rabbits

Growth factors are known to appear during wound healing. We hypothesized that growth factors would also appear during the healing process of a rotator cuff tear. We determined the expression of various growth factors during healing of acute rotator cuff tears in the rabbit. We made a full-thickness defect in the supraspinatus tendon of 27 Japanese white rabbits. The shoulders were harvested on days 1, 3, 5, 7, 9, 11, 14, 21, and 28 postoperatively (n = 3 at each time point). We assessed the expression of basic fibroblast growth factor, insulin-like growth factor 1, platelet-derived growth factor, and transforming growth factor beta. Basic fibroblast growth factor appeared with its peak on days 7 and 9, insulin-like growth factor 1 appeared with its peak on day 5, platelet-derived growth factor appeared with a mild expression between days 7 and 14, and transforming growth factor beta appeared with constant mild expression throughout the observation period. It is likely that each of these growth factors plays a role in the early phase of healing of the supraspinatus tendon in rabbits.

Effects of monofilament nylon coated with basic fibroblast growth factor on endogenous intrasynovial flexor tendon healing

PURPOSE

We developed a monofilament nylon thread that can release various growth factors to enhance intrinsic reparative processes after flexor tendon injury. We evaluated the properties of this thread in vitro and in vivo.

METHODS

Nylon threads were coated with gelatin that subsequently was cross-linked in glutaraldehyde. The thread was soaked in basic fibroblast growth factor (bFGF) solution (400 microg/mL). Exogenous bFGF in the thread was released constantly over the course of 1 week. The biologic activity of bFGF and the biomechanical strength of the thread were examined in vitro and its efficacy was investigated in an in vivo rabbit tendon repair model after early flexion exercises. The sutured sites were examined histologically (hematoxylin-eosin, immunohistochemistry, in situ hybridization), biochemically (Western blot test), and biomechanically (ultimate load) after surgery.

RESULTS

This gelatin-coated thread absorbed iodine 125-labeled bFGF in a time-dependent manner. The total amount of bFGF absorbed by the thread within the tendon tissue was between 3 and 15 mug depending on the concentration of bFGF solution. Basic fibroblast growth factor protein was delivered selectively-not in the surrounding scar but in the repaired tendon-for 3 weeks. Histologic analysis showed that the cellular density at the repaired site increased in accordance with the expression of bFGF messenger RNA and protein in the tendon. Endogenous bFGF expression seemed to be enhanced transiently by exogenous bFGF during the first few weeks. The epitenon showed a vigorous fibroblastic response to the coated thread and the ultimate load also was increased significantly at 3 weeks after surgery.

CONCLUSIONS

This bFGF-coated nylon suture gave excellent results in delivering a drug selectively to tendon; it also induced an increase of biomechanical strength and a thickening of the epitenon layer in vivo during a 3-week period, thereby accelerating cellular proliferation, initially peripherally and later centrally. This system may become a therapeutic tool to be used in hand surgery.

Tendon and ligament: development, repair and disease

Tendons and ligaments (T/L) are very similar fibrous tissues that respectively connect muscle to bone and bone to bone. They are comprised of fibroblasts that produce large amounts of extra-cellular matrix, resulting in a dense and hypocellular structure. The complex molecular organization of T/L, together with high water content, are responsible for their viscoelastic properties, hence insuring their mechanical function. We will first review recent work on tendon embryology and discuss ligament formation, which has been less documented. We will next summarize our current knowledge of T/L molecular architecture, alterations of which are a major cause for disease. We will finally focus on T/L repair after injury and on genetic diseases responsible for T/L defects.

Tendon healing in vitro: bFGF gene transfer to tenocytes by adeno-associated viral vectors promotes expression of collagen genes

PURPOSE

Adeno-associated virus-mediated gene transfer is promising in the delivery of genes to tendons because this vector stimulates few adverse tissue reactions. Basic fibroblast growth factor (bFGF) promotes collagen production in healing tendons. We transferred the exogenous bFGF gene to proliferating tenocytes by adeno-associated viral (AAV) vectors and investigated its effects on the expression of the collagen genes in an in vitro tenocyte model.

METHODS

AAV2 vectors harboring the rat bFGF gene were constructed. Tenocytes were obtained from explant cultures of rat intrasynovial tendons and were distributed into 21 culture dishes and 8 wells. Tenocytes in 7 dishes were treated with AAV2 bFGF for 3 hours and then were cultured for 10 days. Tenocytes in 14 dishes (sham vector and nontreatment controls) did not receive the transgene. Efficiency of the gene transfer was evaluated by in situ beta-galactosidase staining in 8 wells after treatment with AAV2 lacZ. Expression of the target genes was assessed by reverse-transcription polymerase chain reactions with primers specifically amplifying the target genes. Expression of bFGF and type I and III collagen genes was determined by quantitative analysis of the polymerase chain reaction products.

RESULTS

Positive beta-galactosidase staining confirmed the effectiveness of AAV2-mediated gene delivery to tenocytes. The level of expression of the bFGF gene was increased significantly after gene transfer. Levels of expression of type I and III collagen genes after transfer of the exogenous bFGF gene were increased significantly compared with those in the cells treated with sham vectors or in nontreatment controls.

CONCLUSIONS

Delivery of exogenous bFGF gene to tenocytes can increase significantly the levels of expression of the bFGF and type I and III collagen genes. AAV2 vectors provide a novel method for delivering growth factor genes to tenocytes. These findings warrant future in vivo study of the delivery of genes pertinent to tendon healing through AAV2-based gene therapy to enhance repairs of injured flexor tendons.

Stem cell-based composite tissue constructs for regenerative medicine

A major task of contemporary medicine and dentistry is restoration of human tissues and organs lost to diseases and trauma. A decade-long intense effort in tissue engineering has provided the proof of concept for cell-based replacement of a number of individual tissues such as the skin, cartilage, and bone. Recent work in stem cell-based in vivo restoration of multiple tissue phenotypes by composite tissue constructs such as osteochondral and fibro-osseous grafts has demonstrated probable clues for bioengineered replacement of complex anatomical structures consisting of multiple cell lineages such as the synovial joint condyle, tendon-bone complex, bone-ligament junction, and the periodontium. Of greater significance is a tangible contribution by current attempts to restore the structure and function of multitissue structures using cell-based composite tissue constructs to the understanding of ultimate biological restoration of complex organs such as the kidney or liver. The present review focuses on recent advances in stem cell-based composite tissue constructs and attempts to outline challenges for the manipulation of stem cells in tailored biomaterials in alignment with approaches potentially utilizable in regenerative medicine of human tissues and organs.

The use of growth factors on tendon injuries

Tendon injuries continue to be a vexing clinical problem faced by the upper extremity surgeon. These injuries often lead to disability and dissatisfaction for both the patient and treating physician. Advances throughout the century have focused largely on improvements in surgical techniques and therapy protocols. Recently, attention has been turned to the biologic pathways by which tendons heal and the growth factors involved in this process have been identified. There is great hope that these growth factors may one day be used to treat tendon injuries. This article provides a summary of the use of growth factors on tendon injuries including contemporary research, delivery methods, and future directions in this field.

CDMP-2 injection improves early tendon healing in a rabbit model for surgical repair

This study examines the hypothesis that cartilage-derived morphogenic protein-2 (CDMP-2) can improve tendon healing after surgical repair. We have previously found improved tendon healing by applying CDMP-2 in models for conservative treatment with mechanically loaded Achilles tendon defects in rats and rabbits. In this study, the patellar tendon was unloaded by patello- tibial cerclage and cut transversely in 40 rabbits. Two hours post-operative, the rabbits received a dose of 20 microg of CDMP-2 or vehicle injected into the hematoma. Specimens were harvested after 14 and 28 days and evaluated by biomechanical testing, radiography and histology. At 14 days, CDMP-2 caused a 65% increase in force at failure, a 50% increase in ultimate stress and a 57% increase in stiffness, as compared with controls. There was no effect on callus size. At 28 days, no differences between the treatment groups could be demonstrated. No bone or cartilage was found in any tendon or regenerated tissue at any time point. Thus, early tendon repair can be stimulated by CDMP-2 in an unloaded model. These results suggest that CDMP-2 might be of interest for clinical use as a complement to surgical treatment of tendon ruptures.

Mechanobiology of tendon

Tendons are able to respond to mechanical forces by altering their structure, composition, and mechanical properties--a process called tissue mechanical adaptation. The fact that mechanical adaptation is effected by cells in tendons is clearly understood; however, how cells sense mechanical forces and convert them into biochemical signals that ultimately lead to tendon adaptive physiological or pathological changes is not well understood. Mechanobiology is an interdisciplinary study that can enhance our understanding of mechanotransduction mechanisms at the tissue, cellular, and molecular levels. The purpose of this article is to provide an overview of tendon mechanobiology. The discussion begins with the mechanical forces acting on tendons in vivo, tendon structure and composition, and its mechanical properties. Then the tendon's response to exercise, disuse, and overuse are presented, followed by a discussion of tendon healing and the role of mechanical loading and fibroblast contraction in tissue healing. Next, mechanobiological responses of tendon fibroblasts to repetitive mechanical loading conditions are presented, and major cellular mechanotransduction mechanisms are briefly reviewed. Finally, future research directions in tendon mechanobiology research are discussed.

Modulation of proliferation and differentiation of human bone marrow stromal cells by fibroblast growth factor 2: potential implications for tissue engineering of tendons and ligaments

Bone marrow stromal cells (BMSCs) play a central role in the repair and regeneration of mesenchymal tissues. For tissue engineering of ligaments and tendons, both stimulation of cell proliferation and differentiation with increased expression of essential extracellular matrix proteins and cytoskeletal elements are desirable. This study analyzes the effect of low-dose (3 ng/mL) fibroblast growth factor 2 (FGF-2) and high-dose FGF-2 (30 ng/mL) on proliferation (bromodeoxyuridine content, spectrophotometry), differentiation (transcription of collagen I, collagen III, fibronectin, elastin, alpha-smooth muscle actin, and vimentin, reverse transcription-polymerase chain reaction, and cell density and apoptosis (annexin V, fluorescence-activated cell sorting) of human BMSCs, and compares the results with those of a control group without FGF-2. Low-dose FGF-2 triggered a biphasic BMSC response: on day 7, cell proliferation reached its maximum and was significantly higher compared with the other groups. On days 14 or 28, collagen I, collagen III, fibronectin, and alpha- smooth muscle actin mRNA expression was significantly enhanced in the presence of low-dose FGF-2. In contrast, high-dose FGF-2 did not stimulate differentiation or proliferation. Vimentin mRNA was expressed only in cultures with low-dose and high-dose FGF-2 after 14 and 28 days. Cell density was significantly higher in cultures with low-dose FGF-2 compared with the group with high-dose FGF-2 on days 7, 14, and 28. The apoptosis rate remained stable, at a rather high level, in all groups. Microscopic investigation of the cell cultures with low-dose FGF-2 showed more homogeneous, dense, fibroblast-like, spindle-shaped cells with long cell processes compared with cultures with high-dose, or no FGF-2. Low-dose FGF-2 may be useful for tissue engineering of ligaments and tendons by increasing BMSC proliferation and stimulating mRNA expression of specific extracellular matrix proteins and cytoskeletal elements.

Patellar tendinopathy in athletes: current diagnostic and therapeutic recommendations

Formerly known as 'jumper's knee', patellar tendinopathy gives rise to considerable functional deficit and disability in recreational as well as professional athletes. It can interfere with their performance, often perseveres throughout the sporting career and may be the primary cause to end it. The diagnosis of patellar tendinopathy is primarily a clinical one but new imaging techniques, such as Doppler ultrasonography, may provide additional diagnostic value. Current therapeutic protocols are characterised by wide variability ensuing from anecdotal experience rather than evidence. Moreover, numerous reports in recent years have shattered previous doctrines and dogmatic belief on tendon overuse. Histopathological and biochemical evidence has indicated that the underlying pathology of tendinopathy is not an inflammatory tendinitis but a degenerative tendinosis. Consequently, pain in chronic patellar tendinopathy is not inflammatory in nature, but its exact origin remains unexplained. In pursuit of pathology- and evidence-based management, conservative therapy should be shifted from anti-inflammatory strategies towards a complete rehabilitation with eccentric tendon strengthening as a key element. If conservative management fails, surgery is opted for. However, considering the heterogeneity of surgical procedures and the absence of randomised studies, no conclusive evidence can be drawn from the literature regarding the effectiveness of surgical treatment for patellar tendinopathy. Parallel with the improved knowledge on the pathophysiology and pain mechanisms in patellar tendinopathy, new treatment strategies are expected to emerge in the near future.

Effect of several growth factors on canine flexor tendon fibroblast proliferation and collagen synthesis in vitro

PURPOSE

Growth factor delivery may be useful to accelerate the rate of tendon healing. Before in vivo use, however, the effects of growth factors on tendon cells need to be well characterized. The purpose of this study was to evaluate the effects of 4 growth factors on intrasynovial tendon fibroblast proliferation and collagen production in vitro. Our first hypothesis was that platelet-derived growth factor BB (PDGF-BB) and basic fibroblast growth factor (bFGF) would promote cell proliferation and collagen production. Our second hypothesis was that there would be a positive effect from the combination of PDGF-BB and bFGF.

METHODS

The growth factors PDGF-BB, bFGF, vascular endothelial growth factor (VEGF), and bone morphogenetic protein 2 (BMP-2) were evaluated in vitro with canine flexor tendon fibroblasts. The effects of single factors (PDGF-BB, bFGF, VEGF, or BMP-2) or a combination of factors (PDGF-BB and bFGF) on cell proliferation (ie, thymidine incorporation) and collagen production (ie, proline incorporation) were evaluated.

RESULTS

The results supported our hypotheses. Cell proliferation increased significantly with PDGF-BB and bFGF. Collagen production also increased significantly with PDGF-BB and bFGF. Cell proliferation and collagen production were unchanged with VEGF and BMP-2. A dose-response effect was seen for PDGF-BB combined with bFGF. The combination of PDGF-BB and bFGF led to an increase in cell proliferation but no change in collagen production compared with each factor alone.

CONCLUSIONS

The growth factors PDGF-BB and bFGF significantly increased flexor tendon fibroblast proliferation and matrix synthesis when applied singly. Administration of PDGF-BB and bFGF combined led to increased proliferation to single factors.

Total flavones of Hippophae rhamnoides promotes early restoration of ultimate stress of healing patellar tendon in a rat model

Traditional Chinese herbal medicine has long been used for treatment of tendon injuries. Comparing to the modern way of treatments, Traditional Chinese medicine also stresses on strategies to promote the inherent healing capacity of tendons. Hippophae rhamnoides, known as Shaji, is one of Chinese herbal drugs that are traditionally used to promote tendon and ligament injuries. The total flavones of H. rhamnoides (TFH), with major constituents including quercetin, isorhamnetin and kaempferol, have been demonstrated with most of the bioactive properties of Shaji. In the present study, we evaluated the potential effect of TFH in the restoration of ultimate stress of healing patellar tendon in a well-established gap wound model in rats. A 0.1 mg TFH was injected to wound 1 day after the injury, and the ultimate stress of the healing tendon was measured at day 14 post-injury. The results showed that the ultimate stress of the healing tendon was significantly promoted by injection of TFH, increasing from 30 to 50% as compared to saline control. Excessive fibrotic response was not found in TFH-treated animals, but an enhanced collagen deposition and a better fibre alignment were observed. The results suggest that TFH may improve the ultimate stress of healing tendons at early stages, which implies possible earlier rehabilitation programme and better recovery.

Photochemical repair of Achilles tendon rupture in a rat model1

BACKGROUND

Photochemical tissue bonding (PTB) is an emerging technique for bonding or sealing tissue surfaces that requires light and a photoactive dye for its effect. The potential of PTB for tendon repair was assessed in a rat model.

MATERIALS AND METHODS

The optical properties of bovine tendon were determined ex vivo to gauge the depth of light penetration as a function of wavelength and dosimetry parameters were established for PTB repair of ruptured tendon. PTB was then tested in vivo to repair transected tendons in Sprague-Dawley rats. Repair strengths were measured using a strain gauge up to 14 days post treatment.

RESULTS

The effective penetration depth in tendon was estimated to be 0.68 mm at 514 nm. Following PTB treatment of mechanically ruptured tendon, significant bonding was dependent on the presence of both light and dye and attained a plateau strength at a fluence of 125 J/cm2. In a subsequent in vivo study to investigate PTB for repair of transected rat Achilles tendon, the ultimate stress required to break the repaired tendon was measured immediately after irradiation and at 7 and 14 days post-repair. Results showed that the difference in the ultimate stress between control and PTB treatment groups was statistically significant immediately after treatment and at 7 days (p = 0.04) but not 14 days (p = 0.75) post-repair.

CONCLUSIONS

PTB provides a benefit to tendon repair at early stages in repair and is worthy of further investigation as a potential surgical adjunct for tendon repair in orthopedic surgeries.

Tendon healing in vitro: modification of tenocytes with exogenous vascular endothelial growth factor gene increases expression of transforming growth factor beta but minimally affects expression of collagen genes

PURPOSE

It is not clear how the transfer of exogenous growth factor genes to tenocytes affects collagen production. An increase in collagen production enhances the repair but an increase in growth factors that stimulate tissue fibrosis may cause adhesion. Gene therapy is a new way to regulate tendon healing but it has been explored rarely. We genetically modified tenocytes with the vascular endothelial growth factor (VEGF) gene and investigated the expression of the genes for collagen production in an in vitro model of the proliferating tenocytes.

METHODS

Tenocytes were obtained from cultures of rat intrasynovial tendons and distributed randomly to 25 dishes. The tenocytes in the experimental dishes (n = 9) were treated for 12 hours with plasmid containing the VEGF complementary deoxyribonucleic acid and then were cultured for 5 days; the tenocytes in the control dishes (n = 8) did not receive the exogenous gene. Tenocytes in the other dishes received exogenous platelet-derived growth factor (PDGF) gene for comparison of the effects of VEGF gene therapy. Efficiency of the gene transfer was evaluated by presence of the transgene in the tenocytes which was detected by reverse transcription polymerase chain reactions. Levels of expression of types I and III collagen and transforming growth factor (TGF)-beta genes were determined by quantitative analysis of the products of reverse transcription polymerase chain reactions.

RESULTS

Expression of the TGF-beta gene increased significantly in the cells treated with exogenous VEGF cDNA. Expression of type I and III collagen genes by tenocytes was affected minimally by transfer of the VEGF gene to the tenocytes and was significantly weaker than that stimulated by PDGF gene therapy. Efficient gene transfer was confirmed by the presence of the VEGF complementary deoxyribonucleic acid in the tenocytes receiving the transferred gene.

CONCLUSIONS

Transfer of exogenous VEGF gene has very limited effects on the promotion of collagen production in the proliferating tenocytes. This study suggests that VEGF gene therapy is not as beneficial as PDGF gene therapy to tendon healing and may increase the activities of TGF-beta that are associated with adhesion formations.

TGF-beta1 reverses the effects of matrix anchorage on the gene expression of decorin and procollagen type I in tendon fibroblasts

Transforming growth factor-beta1 is known for its effect on the production of extracellular matrix in tendons. Elevated levels of transforming growth factor-beta1 have been reported in tendon adhesion and tendinosis, which suggests that transforming growth factor-beta1 plays an important role in matrix disturbances. Tendon adhesion involves excessive collagen deposition, whereas tendinosis is associated with increased proteoglycan deposition. It seems that other factors also may affect matrix deposition and modulate the effects of transforming growth factor-beta1. We assessed whether matrix anchorage to Type I collagen or fibronectin could change the gene expression of matrix proteins in tendon fibroblasts, and studied whether the effects of transforming growth factor-beta1 were altered by matrix anchorage. Human patellar tendon fibroblast cultures were prepared in different cell anchorages, and the cellular responses to transforming growth factor-beta1 were measured as gene expression of procollagen Type I, Type III, decorin, and biglycan by real-time reverse transcriptase-polymerase chain reaction. Fibronectin anchorage significantly increased the messenger ribonucleic acid level of decorin, and the messenger ribonucleic acid level of procollagen Type I was decreased by matrix anchorage to either fibronectin or Type I collagen. Transforming growth factor-beta1 increased the messenger ribonucleic acid level of procollagen Type I in Type I collagen-coated plates, but it suppressed the messenger ribonucleic acid level of decorin in fibronectin-coated plates. These findings suggest that interaction of matrix anchorage and transforming growth factor-beta1 is an important determinant of matrix deposition in healing tendons and the development of matrix disturbances in tendons.

Signals regulating tendon formation during chick embryonic development

Tendons are collagen-rich structures that link muscle to cartilage. By using quail-chick chimeras, it has been shown that tendon and cartilage cells originate from the same mesodermic compartment, which is distinct from that giving rise to muscle cells. Axial tendons originate from the sclerotomal compartment, and limb tendons originate from the lateral plate, whereas axial and limb muscles derive from dermomyotomes. Despite these different embryologic origins, muscle and tendon morphogenesis occurs in close spatial and temporal association. Facilitated by the distinct embryologic origin of myogenic and tendon cells, surgical studies in the avian embryo have highlighted interactions between tendons and muscles, during embryonic development. However, these interactions seem to differ between axial and limb levels. The molecular mechanisms underlying muscle and tendon interactions have been shown recently to involve different members of the fibroblast growth factor family. This review covers the available data on the early steps of tendon formation in the limb and along the primary axis. The relationship with muscle morphogenesis will be highlighted.

Clinical implications of growth factors in flexor tendon wound healing

Recent research has focused on the role of growth factors in flexor tendon wound healing. These basic science reports have described the identification and quantification of various growth factors in in vitro and in vivo models. Although these reports have begun to piece together the cascade of events involved in flexor tendon wound healing, the clinical relevance for the practicing hand surgeon is unclear. Growth factors are cell-secreted proteins that regulate cellular functions. These growth factors are involved in cell differentiation and growth, including the normal processes of development and tissue repair. Several growth factors recently have been identified as playing roles in tendon healing including vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and transforming growth factor beta (TGF-beta). In addition, the transcription factor NF-kappaB has been implicated in the signaling pathways of these growth factors. The purpose of this article is to describe what is known about the molecular basis of flexor tendon wound healing, to review the most commonly studied growth factors, and to summarize likely clinical applications of these growth factors to flexor tendon repair.

Promoting the proliferative and synthetic activity of knee meniscal fibrochondrocytes using basic fibroblast growth factor in vitro

BACKGROUND

Meniscal tears situated within the inner avascular region do not heal despite suturing. New approaches need to be developed to augment surgical repair.

HYPOTHESIS

To demonstrate that basic fibroblast growth factor, used as a single agent or in combination with serum, stimulates the activity of fibrochondrocytes by enhancing proliferation and extracellular matrix synthesis in all meniscal zones, including the inner (avascular) zone of the meniscus.

STUDY DESIGN

Controlled laboratory study.

METHODS

Monolayer cell cultures were prepared from the inner, middle, and outer zones of the lateral meniscus. Various concentrations of basic fibroblast growth factor were used in the presence or absence of 10% fetal calf serum. The authors measured the uptake of radiolabeled thymidine to assess cell proliferation and radioactive sulfur and proline to assess extracellular matrix formation.

RESULTS

Overall, basic fibroblast growth factor-stimulated cells from all meniscal zones to proliferate and to form new extra-cellular matrix (P <.05). The basic fibroblast growth factor (in the absence of serum) increased DNA formation and protein synthesis by cells from the inner meniscal zone by 7- and 15-fold, respectively (P <.001).

CONCLUSIONS

These results indicate that meniscal cells and, more important, cells from the avascular zone are capable of responding favorably to the addition of basic fibroblast growth factor by expressing their intrinsic potential to proliferate and generate new extracellular matrix.

CLINICAL RELEVANCE

The results suggest that it may be possible to augment surgical repair of the meniscus in the future.

Effect of vascular endothelial growth factor on rat Achilles tendon healing

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

The roles of growth factors in tendon and ligament healing

Tendon healing is a complex and highly-regulated process that is initiated, sustained and eventually terminated by a large number and variety of molecules. Growth factors represent one of the most important of the molecular families involved in healing, and a considerable number of studies have been undertaken in an effort to elucidate their many functions. This review covers some of the recent investigations into the roles of five growth factors whose activities have been best characterised during tendon healing: insulin-like growth factor-I (IGF-I), transforming growth factor beta (TGFbeta), vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and basic fibroblast growth factor (bFGF). All five are markedly up-regulated following tendon injury and are active at multiple stages of the healing process. IGF-I has been shown to be highly expressed during the early inflammatory phase in a number of animal tendon healing models, and appears to aid in the proliferation and migration of fibroblasts and to subsequently increase collagen production. TGFbeta is also active during inflammation, and has a variety of effects including the regulation of cellular migration and proliferation, and fibronectin binding interactions. VEGF is produced at its highest levels only after the inflammatory phase, at which time it is a powerful stimulator of angiogenesis. PDGF is produced shortly after tendon damage and helps to stimulate the production of other growth factors, including IGF-I, and has roles in tissue remodelling. In vitro and in vivo studies have shown that bFGF is both a powerful stimulator of angiogenesis and a regulator of cellular migration and proliferation. This review also covers some of the most recent studies into the use of these molecules as therapeutic agents to increase the efficacy and efficiency of tendon and ligament healing. Studies into the effects of the exogenous application of TGFbeta, IGF-I, PDGF and bFGF into the wound site singly and in combination have shown promise, significantly decreasing a number of parameters used to define the functional deficit of a healing tendon. Application of IGF-I has been shown to increase in the Achilles Functional Index and the breaking energy of injured rat tendon. TGFbeta and PDGF have been shown separately to increase the breaking energy of healing tendon. Finally, application of bFGF has been shown to promote cellular proliferation and collagen synthesis in vivo.

Systemic vanadate ingestion modulates rat tendon repair

The chronic ingestion of vanadate prevents the appearance of myofibroblasts within granulation tissue of full excision wounds in rats, yet these wounds close at an optimal rate. Myofibroblasts are reported in the repair of transected tendons. Here we investigate tendon repair in the absence of myofibroblasts. Vanadate in saline drinking water was given to rats in the experimental group, while rats in the control group received saline alone. The Achilles tendon of the left leg of each rat was transected and suture repaired. On day 10, both repaired tendons and uninjured tendons from the right leg were harvested and processed for histology. By immunohistology the repaired tendons of control rats had myofibroblasts (fibroblasts with alpha smooth muscle actin positive stress fibers), while myofibroblasts were absent in healing tendons from vanadate-treated rats. By transmission electron microscopy and polarized light optics, repaired tendons of control rats demonstrated thin, loosely packed, immature collagen fiber bundles. Collagen fiber bundles from healing tendons of the vanadate-treated group were thicker, uniformly packed, and more mature. The chronic ingestion of vanadate promotes the more rapid organization of collagen fiber bundles of healing transected tendons in the absence of myofibroblasts.

Adenovirus-mediated gene transfer to healing tendon--enhanced efficiency using a gelatin sponge

Adenovirus-mediated gene transfer is a potential method for enhancing tendon healing. We investigated the transfection of Ad5CMVntLacZ, an adenovirus containing the reporter gene LacZ, in primary cultured human rotator cuff tendon cells and in a rat Achilles tendon healing model in vivo. Ad5CMVempty, the adenoviral vector containing no inserted gene, was used as a control for adenoviral transfection alone. Activity of beta-galactosidase,the protein expressed by LacZ gene, was measured using a beta-galactosidase assay and detected visually by X-gal staining. Cultured cells were successfully transfected without impairing cell viability. Maximal beta-galactosidase activity was detected when cells were transfected at the dose of 1000 PFU/cell. The duration of LacZ expression was six days with a peak value at 24 h post-transfection. A transfection rate of 100% was obtained at 5000 PFU/cell. Successful in vivo transfection by Ad5CMVntLacZ was obtained in healing rat Achilles tendon as confirmed by X-gal staining. 0.4% of tendon cells were transfected when Ad5CMVntLacZ was injected into the tendon at a dose of 10(6) PFU. The rate rose to 2% with 10(8) PFU and 3% with 10(9) PFU. The duration of LacZ expression in vivo was 17 days. Transfection efficiency was enhanced threefold and localization improved when a gelatin sponge was used to deliver the adenovirus. The results demonstrate that adenovirus can be used to deliver a gene of interest to cultured human rotator cuff tendon cells and healing tendon, with gelatin sponge implantation enhancing adenoviral transfection efficiency in vivo.

Basic science and clinical studies coincide: active treatment approach is needed after a sports injury

The basic response to injury at the tissue level is well known and consists of acute inflammatory phase, proliferative phase, and maturation and remodeling phase. Knowing these phases, the treatment and rehabilitation program of athletes' acute musculoskeletal injuries should use a short period of immobilization followed by controlled and progressive mobilization. Both experimental and clinical trials have given systematic and convincing evidence that this program is superior to immobilization - a good example where basic science and clinical studies do coincide - and therefore active approach is needed in the treatment of these injuries.

The roles of bone morphogenetic protein (BMP) 12 in stimulating the proliferation and matrix production of human patellar tendon fibroblasts

Recombinant human (rh) bone morphogenetic protein 12 (BMP12) is proved to induce the formation of tendon and ligament tissues in animal experiments. But the roles of BMP12 on tissue regeneration in human tendons remain unexplored. In the present study, healthy human patellar tendon samples were collected for histological examination and preparation of tendon fibroblast culture. Immunohistochemical staining showed that BMP12 was detected on healthy patellar tendon samples, only located on active tenoblasts and perivascular mesenchymal cells but not in interstitial tenocytes. The expression of PCNA and procollagen type I also exhibited a similar distribution. It indicates that BMP12 may be involved in matrix remodeling process in adult tissues. In vitro studies showed that rhBMP12 could increase proliferation of tendon fibroblasts and increase the gene expression of procollagen type I and type III, but decrease the gene expression of decorin in tendon fibroblasts culture. Our findings suggest that BMP12 may play a role in early phases of tissue regeneration in tendons.

Effect of recombinant basic fibroblast growth factor (bFGF) on fibroblast-like cells from human rotator cuff tendon

Rotator cuff tendon cells (RCC) derived from surgical samples showed fibroblast-like morphology. Histological staining demonstrated collagen secretion by RCC. Immunohistological findings revealed that RCC secreted type I and III collagen, but not type II collagen. In addition, the SDS-PAGE analysis suggested that RCC predominantly produced type I collagen. Basic fibroblast growth factor (bFGF) had a stimulatory effect on the proliferation of RCC dose-dependently up to 1 ng/ml. Administration of bFGF suppressed the secretion of collagens from RCC in a dose-dependent manner.

Fgf4 positively regulates scleraxis and tenascin expression in chick limb tendons

In vertebrates, tendons connect muscles to skeletal elements. Surgical experiments in the chick have underlined developmental interactions between tendons and muscles. Initial formation of tendons occurs autonomously with respect to muscle. However, further tendon development requires the presence of muscle. The molecular signals involved in these interactions remain unknown. In the chick limb, Fgf4 transcripts are located at the extremities of muscles, where the future tendons will attach. In this paper, we analyse the putative role of muscle-Fgf4 on tendon development. We have used three general tendon markers, scleraxis, tenascin, and Fgf8 to analyse the regulation of these tendon-associated molecules by Fgf4 under different experimental conditions. In the absence of Fgf4, in muscleless and aneural limbs, the expression of the three tendon-associated molecules, scleraxis, tenascin, and Fgf8, is down-regulated. Exogenous implantation of Fgf4 in normal, aneural, and muscleless limbs induces scleraxis and tenascin expression but not that of Fgf8. These results indicate that Fgf4 expressed in muscle is required for the maintenance of scleraxis and tenascin but not Fgf8 expression in tendons.