Type V collagen is increased during rabbit medial collateral ligament healing

Collagen V haploinsufficiency in female murine patellar tendons results in altered matrix engagement and cellular density, demonstrating decreased healing

Collagen V (Col5) is a quantitatively minor component of collagen fibrils comprising tendon, however, plays a crucial role in regulation of development and dynamic healing processes. Clinically, patients with COL5a1 haploinsufficiency, known as classic Ehlers-Danlos Syndrome (cEDS), present with hyperextensible skin, joint instability and laxity, with females more likely to be affected. Previous studies in Col5-deficient mice indicated that reduced Col5a1 expression leads to a reduction in stiffness, fibril deposition, and altered fibril structure. Additionally, Col5-deficient male tendons demonstrated altered healing compared to wild-type tendons, however female mice have not yet been studied utilizing this model. Along with clinical differences between sexes in cEDS patient populations, differences in hormone physiology may be a factor influencing tendon health. Therefore, the objective of this study was to utilize a Col5a1+/ - female mouse model, to determine the effect of Col5 on tendon cell morphology, cell density, tissue composition, and mechanical properties throughout healing. We hypothesized that reduction in Col5 expression would result in an abnormal wound matrix post-injury, resulting in reduced mechanical properties compared to normal tendons. Following patellar tendon surgery, mice were euthanized at 1, 3, and 6-week post-injury. Col5-deficient tendons demonstrated altered and decreased healing compared to WT tendons. The lack of resolution in cellularity by 6-week post-injury in Col5-deficient tendons influenced the decreased mechanical properties. Stiffness did not increase post-injury in Col5-deficient mice, and collagen fiber realignment was delayed during mechanical loading. Therefore, increased Col5a1 expression post-injury is necessary to re-establish matrix engagement and cellularity throughout tendon healing.

Genomic Determinants of Knee Joint Biomechanics: An Exploration into the Molecular Basis of Locomotor Function, a Narrative Review

In recent years, the nexus between genetics and biomechanics has garnered significant attention, elucidating the role of genomic determinants in shaping the biomechanical attributes of human joints, specifically the knee. This review seeks to provide a comprehensive exploration of the molecular basis underlying knee joint locomotor function. Leveraging advancements in genomic sequencing, we identified specific genetic markers and polymorphisms tied to key biomechanical features of the knee, such as ligament elasticity, meniscal resilience, and cartilage health. Particular attention was devoted to collagen genes like COL1A1 and COL5A1 and their influence on ligamentous strength and injury susceptibility. We further investigated the genetic underpinnings of knee osteoarthritis onset and progression, as well as the potential for personalized rehabilitation strategies tailored to an individual's genetic profile. We reviewed the impact of genetic factors on knee biomechanics and highlighted the importance of personalized orthopedic interventions. The results hold significant implications for injury prevention, treatment optimization, and the future of regenerative medicine, targeting not only knee joint health but joint health in general.

Mesenchymal Stem Cells for Enhanced Healing of the Medial Collateral Ligament of the Knee Joint

Background and Objectives: The medial collateral ligament (MCL) is one of the major supporting ligaments of the knee joint, and MCL injuries are common where excessive valgus loading is applied to the knee joint. Although most MCL injuries can be treated conservatively, healing of the MCL can take several weeks to months. Furthermore, once injured, the biomechanical properties of the healed MCL differ from those of the native MCL, resulting in an increased risk of re-injury and chronic remnant symptoms. Mesenchymal stem cells (MSCs), owing to their therapeutic potential, have been investigated in various musculoskeletal injuries, and some preclinical studies regarding MSC-based approaches in MCL injuries have shown promising results. Despite satisfactory results in preclinical studies, there is still a lack of clinical studies in the orthopedic literature. This article describes the basic knowledge of the MCL, standard treatments for MCL injuries, and recent studies regarding the application of MSCs for enhanced healing of the MCL. MSC-based approaches are expected to be a potential therapeutic option for enhanced healing of the MCL in the future.

Transcriptomic Profiling of Human Limbus-Derived Stromal/Mesenchymal Stem Cells-Novel Mechanistic Insights into the Pathways Involved in Corneal Wound Healing

Limbus-derived stromal/mesenchymal stem cells (LMSCs) are vital for corneal homeostasis and wound healing. However, despite multiple pre-clinical and clinical studies reporting the potency of LMSCs in avoiding inflammation and scarring during corneal wound healing, the molecular basis for the ability of LMSCs remains unknown. This study aimed to uncover the factors and pathways involved in LMSC-mediated corneal wound healing by employing RNA-Sequencing (RNA-Seq) in human LMSCs for the first time. We characterized the cultured LMSCs at the stages of initiation (LMSC−P0) and pure population (LMSC−P3) and subjected them to RNA-Seq to identify the differentially expressed genes (DEGs) in comparison to native limbus and cornea, and scleral tissues. Of the 28,000 genes detected, 7800 DEGs were subjected to pathway-specific enrichment Gene Ontology (GO) analysis. These DEGs were involved in Wnt, TGF-β signaling pathways, and 16 other biological processes, including apoptosis, cell motility, tissue remodeling, and stem cell maintenance, etc. Two hundred fifty-four genes were related to wound healing pathways. COL5A1 (11.81 ± 0.48) and TIMP1 (20.44 ± 0.94) genes were exclusively up-regulated in LMSC−P3. Our findings provide new insights involved in LMSC-mediated corneal wound healing.

The novel epiligament theory: differences in healing failure between the medial collateral and anterior cruciate ligaments

According to current literature, 90% of knee ligament injuries involve the medial collateral ligament or the anterior cruciate ligament. In contrast to the medial collateral ligament, which regenerates relatively well, the anterior cruciate ligament demonstrates compromised healing. In the past, there were numerous studies in animal models that examined the healing process of these ligaments, and different explanations were established. Although the healing of these ligaments has been largely investigated and different theories exist, unanswered questions persist.

Therefore, the aim of this article is 1) to review the different historical aspects of healing of the medial collateral ligament and present the theories for healing failure of the anterior cruciate ligament; 2) to examine the novel epiligament theory explaining the medial collateral ligament healing process and failure of anterior cruciate ligament healing; and 3) to discuss why the enveloping tissue microstructure of the aforementioned ligaments needs to be examined in future studies.

We believe that knowledge of the novel epiligament theory will lead to a better understanding of the normal healing process for implementing optimal treatments, as well as a more holistic explanation for anterior cruciate ligament healing failure.

Talipes Equinus Deformity Caused by Fibrous Gastrocnemius Muscle Contracture After Direct Contusion in Football Players: Report of Two Cases

Two main causes of gastrocnemius contracture have been considered: 1) congenital deformities in pediatric patients, such as limb-length discrepancy, cerebral palsy, flatfoot, and clubfoot; and 2) secondary conditions such as immobilization for trauma or a nonfunctional limb. Talipes equinus deformity caused by fibrous gastrocnemius contracture after a direct muscle contusion is extremely rare. We describe 2 cases of talipes equinus deformity caused by fibrous gastrocnemius muscle contracture after a direct contusion in football players. Both of the players had a talipes equinus deformity with a severe restriction of ankle dorsiflexion, and a cord-like structure was observed at the proximal part of the lateral gastrocnemius head. Both patients' histological examinations revealed fibrous tendon-like tissue within the structure. After discission of the cord-like structures, the restriction of ankle dorsiflexion was completely resolved, and the patients were able to fully return to playing football without any discomfort in their calves.

Bioinspired Scaffold Designs for Regenerating Musculoskeletal Tissue Interfaces

The musculoskeletal system works at a very advanced level of synchrony, where all the physiological movements of the body are systematically performed through well-organized actions of bone in conjunction with all the other musculoskeletal soft tissues, such as ligaments, tendons, muscles, and cartilage through tissue-tissue interfaces. Interfaces are structurally and compositionally complex, consisting of gradients of extracellular matrix components, cell phenotypes as well as biochemical compositions and are important in mediating load transfer between the distinct orthopedic tissues during body movement. When an injury occurs at interface, it must be re-established to restore its function and stability. Due to the structural and compositional complexity found in interfaces, it is anticipated that they presuppose a concomitant increase in the complexity of the associated regenerative engineering approaches and scaffold designs to achieve successful interface regeneration and seamless integration of the engineered orthopedic tissues. Herein, we discuss the various bioinspired scaffold designs utilized to regenerate orthopedic tissue interfaces. First, we start with discussing the structure-function relationship at the interface. We then discuss the current understanding of the mechanism underlying interface regeneration, followed by discussing the current treatment available in the clinic to treat interface injuries. Lastly, we comprehensively discuss the state-of-the-art scaffold designs utilized to regenerate orthopedic tissue interfaces.

Compound phenotype of osteogenesis imperfecta and Ehlers-Danlos syndrome caused by combined mutations in COL1A1 and COL5A1

Osteogenesis imperfecta (OI) is an inherited connective tissue disorder with a broad clinical spectrum that can overlap with Ehlers-Danlos syndrome (EDS). To date, patients with both OI and EDS have rarely been reported. In the present study, we investigated a family with four members, one healthy individual, one displaying OI only, and two displaying the compound phenotype of OI and EDS, and identified the pathogenic mutations. Whole exome sequencing was applied to the proband and her brother. To verify that the mutations were responsible for the pathogenesis, conventional Sanger sequencing was performed for all members of the family. We identified a known COL1A1 (encoding collagen type I α 1 chain) mutation (c.2010delT, p.Gly671Alafs*95) in all three patients (the proband, her brother, and her mother) in this family, but also a novel heterozygous COL5A1 (encoding collagen type V α 1 chain) mutation (c.5335A>G, p.N1779D) in the region encoding the C-terminal propeptide domain in the proband and her mother, who both had the compound phenotype of OI and EDS. The results of the present study suggested that the proband and her mother presented with the compound OI-EDS phenotype caused by pathogenic mutations in COL5A1 and COL1A1.

The Epiligament: Structure, Postnatal Development and Role in Ligament Healing

While much is known about the ligament, the precise morphology and function of the thin layer of connective tissue lining its surface, termed the epiligament, have not been fully studied yet. Herein, we aimed at reviewing the recent findings on the structural and functional significance of the epiligament in both animal models and human tissue. The epiligament is made up of various connective tissue cells such as fibroblasts, fibrocytes, mast cells, and adipocytes and contains a number of neurovascular bundles. Arrangement of collagen fibers in the epiligament is rather chaotic, in multiple directions, which allows for greater mobility and resistance to stress. Differences in the collagen content and types of enzymes of the group of matrix metalloproteinases between the epiligament and the underlying ligament tissue have been reported and are reviewed herein. While the ligament tissue mainly contains collagen type I, the epiligament is also rich in collagen types III and V. As suggested by a number of studies, the epiligament plays a key role in ligament repair as a donor of cells and matrix metalloproteinases, particularly matrix metalloproteinase-2 and 9, which are essential for scar tissue remodeling. In conclusion, future studies will likely reveal additional functional aspects of the epiligament, which may allow scientists to devise more suitable treatment strategies for damaged ligaments in a world where injuries resulting from sports activities or daily routine have long merited their due attention.

A comparative study of the epiligament of the medial collateral and the anterior cruciate ligament in the human knee. Immunohistochemical analysis of collagen type I and V and procollagen type III

BACKGROUND

Recent reports in rat models have shown that fibroblasts in the epiligament, an enveloping tissue of the ligament, are not static cells and play an important role during the early ligament healing of isolated grade III injury of the collateral ligaments of the knee. Fibroblasts produce collagen types I, III and V and infiltrate within the ligament body via the endoligament. In addition, similarities have been reported between the structure of the epiligament of the medial collateral ligament and anterior cruciate ligament of the knee in rat and in human. In line with the ascribed role of the epiligament tissue and the synthesis of these collagens and their role in ligament healing, the aim of this study was to determine their presence in the normal epiligament of the aforementioned ligaments in humans, to compare their differential expression and to present a novel hypothesis about the failure of healing of the anterior cruciate ligament in contrast to the medial collateral ligament.

MATERIALS AND METHODS

We used samples from the mid-substance of the medial collateral and the anterior cruciate ligament of the knee joint, acquired from 12 fresh knee joints. Routine histological analysis was performed through hematoxylin and eosin stain, Mallory's trichrome stain and Van Gieson's stain. The immunohistochemical analysis was conducted using monoclonal antibodies against collagen type I and V and procollagen type III. The number of cells in the epiligament, endoligament and the ligament tissue was assessed quantitatively through a computerized system for image analysis NIS-Elements Advanced Research and Statistica software.

RESULTS

Our observations revealed certain differences in the morphology of the epiligament, as well as variations in the expression of the investigated molecules. Expression of collagen type I was mostly low-positive (1+) in the epiligament and positive (2+) in the ligament tissue of both ligaments. Expression of procollagen type III was mostly positive (2+) in the epiligament and ligament tissue of the medial collateral ligament, low-positive (1+) in the epiligament and negative (0) in ligament tissue of the anterior cruciate ligament. Expression of collagen type V was predominantly low-positive (1+) in the epiligament and negative (0) in the ligament tissue of both ligaments. The immunoreactivity for all three molecules was always higher in the epiligament of the medial collateral ligament than that of the anterior cruciate ligament.

CONCLUSIONS

The results of our study illustrate for the first time that fibroblasts in the human epiligament are indeed responsible for the synthesis of the main types of collagen participating in the early ligament healing, thus corresponding to previous data of the medial collateral ligament healing in animal models. The differences between the epiligament of the investigated ligaments could add a novel explanation for the failed anterior cruciate ligament healing.

Effects of season long participation on ACL volume in female intercollegiate soccer athletes

Background

The aim of this study was to characterize the volumetric changes of the anterior cruciate ligament over the course of a competitive soccer season in female athletes.

Methods

Seventeen Division-I collegiate soccer players were recruited. Two data collection sessions were conducted. The first data collection occurred prior to the start of the soccer season. Each subject completed a brief questionnaire, had height and weight measured, underwent a clinical assessment of their anterior cruciate ligaments and an eight sequence magnetic resonance imagery of their knees. Contours of the anterior cruciate ligaments were outlined in sagittal T-2 weighted MR images and volumes were calculated using Medical Image Processing, Analysis, and Visualization software. Presence or absence of edema within the ligament was determined in pre and post season scans. All subjects were followed during the season to determine if a lower extremity injury had been sustained.

Results

Mean ligament volume significantly increased from preseason to postseason (p=.006). There was a 10% increase in the percentage of knees with edema pre to post season.

Conclusions

The physical demand of a competitive soccer season in female collegiate athletes appears to cause an increase in volume of the anterior cruciate ligament. The increase in volume may be related to the accumulation of microscopic tears over the course of the season which induce inflammation and edema. The volumetric changes in the ligament may have significant clinical implications, however further studies must be done to determine the relationship between anterior cruciate ligament volume and risk of injury.

Molecular insights in the pathogenesis of classical Ehlers-Danlos syndrome from transcriptome-wide expression profiling of patients' skin fibroblasts

Classical Ehlers-Danlos syndrome (cEDS) is a dominant inherited connective tissue disorder mainly caused by mutations in the COL5A1 and COL5A2 genes encoding type V collagen (COLLV), which is a fibrillar COLL widely distributed in a variety of connective tissues. cEDS patients suffer from skin hyperextensibility, abnormal wound healing/atrophic scars, and joint hypermobility. Most of the causative variants result in a non-functional COL5A1 allele and COLLV haploinsufficiency, whilst COL5A2 mutations affect its structural integrity. To shed light into disease mechanisms involved in cEDS, we performed gene expression profiling in skin fibroblasts from four patients harboring haploinsufficient and structural mutations in both disease genes. Transcriptome profiling revealed significant changes in the expression levels of different extracellular matrix (ECM)-related genes, such as SPP1, POSTN, EDIL3, IGFBP2, and C3, which encode both matricellular and soluble proteins that are mainly involved in cell proliferation and migration, and cutaneous wound healing. These gene expression changes are consistent with our previous protein findings on in vitro fibroblasts from other cEDS patients, which exhibited reduced migration and poor wound repair owing to COLLV disorganization, altered deposition of fibronectin into ECM, and an abnormal integrin pattern. Microarray analysis also indicated the decreased expression of DNAJB7, VIPAS39, CCPG1, ATG10, SVIP, which encode molecular chaperones facilitating protein folding, enzymes regulating post-Golgi COLLs processing, and proteins acting as cargo receptors required for endoplasmic reticulum (ER) proteostasis and implicated in the autophagy process. Patients’ cells also showed altered mRNA levels of many cell cycle regulating genes including CCNE2, KIF4A, MKI67, DTL, and DDIAS. Protein studies showed that aberrant COLLV expression causes the disassembly of itself and many structural ECM constituents including COLLI, COLLIII, fibronectin, and fibrillins. Our findings provide the first molecular evidence of significant gene expression changes in cEDS skin fibroblasts highlighting that defective ECM remodeling, ER homeostasis and autophagy might play a role in the pathogenesis of this connective tissue disorder.

Extracellular Matrix Expression and Production in Fibroblast-Collagen Gels: Towards an In Vitro Model for Ligament Wound Healing

Ligament wound healing involves the proliferation of a dense and disorganized fibrous matrix that slowly remodels into scar tissue at the injury site. This remodeling process does not fully restore the highly aligned collagen network that exists in native tissue, and consequently repaired ligament has decreased strength and durability. In order to identify treatments that stimulate collagen alignment and strengthen ligament repair, there is a need to develop in vitro models to study fibroblast activation during ligament wound healing. The objective of this study was to measure gene expression and matrix protein accumulation in fibroblast-collagen gels that were subjected to different static stress conditions (stress-free, biaxial stress, and uniaxial stress) for three time points (1, 2 or 3 weeks). By comparing our in vitro results to prior in vivo studies, we found that stress-free gels had time-dependent changes in gene expression (col3a1, TnC) corresponding to early scar formation, and biaxial stress gels had protein levels (collagen type III, decorin) corresponding to early scar formation. This is the first study to conduct a targeted evaluation of ligament healing biomarkers in fibroblast-collagen gels, and the results suggest that biomimetic in-vitro models of early scar formation should be initially cultured under biaxial stress conditions.

Use of Platelet-Rich Plasma Immediately After an Injury Did Not Improve Ligament Healing, and Increasing Platelet Concentrations Was Detrimental in an In Vivo Animal Model

BACKGROUND

Limited information in basic science and clinical trials exists to determine if ligament healing may be accelerated with the use of biological adjuvants, such as platelet-rich plasma (PRP). However, there has been widespread acceptance of PRP for use in clinical practice, despite an inadequate understanding of its biological mechanism of action.

PURPOSE

To determine whether a single dose of PRP could accelerate ligament healing and correspondingly improve histological characteristics and biomechanical properties when injected immediately postoperatively into the injured medial collateral ligament (MCL) of New Zealand White rabbits.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eighty skeletally mature New Zealand White rabbits (160 knees) were used. The MCL was torn midbody to simulate a grade 3 tear. After an acute injury of the MCL, the administration of autologous PRP at 3 different platelet concentrations (0 million/uL, platelet-poor plasma [PPP]; 0.6 million/uL, 2 times the baseline [2× PRP]; and 1.2 million/uL, 4 times the baseline [4× PRP]) was performed and compared with a saline injection control in the contralateral knee. Histological analysis and a biomechanical endpoint characterization were utilized to assess ligamentous healing and compare it to a sham surgery group.

RESULTS

The PPP ( P = .001) and 4× PRP ( P = .002) groups had a significantly lower collagen subscore than the sham surgery group. No other differences were observed among the treatment groups, including the vascularity subscore and overall ligament tissue maturity index score. Compared with saline-injected contralateral knees, the maximum load for PPP and 2× PRP was not significantly different ( P = .788 and .325, respectively). The maximum load and stiffness for knees treated with 4× PRP were significantly less than for the saline-treated contralateral knees ( P = .006 and .001, respectively).

CONCLUSION

One single dose of PPP or 2× PRP at the time of injury did not improve ligament healing. In addition, 4× PRP negatively affected ligament strength and histological characteristics at 6 weeks after the injury.

CLINICAL RELEVANCE

The current practice of treating knee ligament injuries with PRP may not improve healing at low doses of PRP. The decreased mechanical properties and histological appearance of the torn MCL suggest that high doses of PRP decrease the quality of repair tissue. Further in vivo studies are necessary to determine the dosing and timing of PRP administration after a ligament injury before the widespread use of PRP to treat ligament injuries is recommended.

Collagen V haploinsufficiency in a murine model of classic Ehlers-Danlos syndrome is associated with deficient structural and mechanical healing in tendons

Classic Ehlers-Danlos syndrome (EDS) patients suffer from connective tissue hyperelasticity, joint instability, skin hyperextensibility, tissue fragility, and poor wound healing due to heterozygous mutations in COL5a1 or COL5a2 genes. This study investigated the roles of collagen V in establishing structure and function in uninjured patellar tendons as well as in the injury response using a Col5a1^+/- mouse, a model for classic EDS. These analyses were done comparing tendons from a classic EDS model (Col5a1^+/- ) with wild-type controls. Tendons were subjected to mechanical testing, histological, and fibril analysis before injury as well as 3 and 6 weeks after injury. We found that Col5a1^+/- tendons demonstrated diminished recovery of mechanical competency after injury as compared to normal wild-type tendons, which recovered their pre-injury values by 6 weeks post injury. Additionally, the Col5a1^+/- tendons demonstrated altered fibril morphology and diameter distributions compared to the wild-type tendons. This study indicates that collagen V plays an important role in regulating collagen fibrillogenesis and the associated recovery of mechanical integrity in tendons after injury. In addition, the dysregulation with decreased collagen V expression in EDS is associated with a diminished injury response. The results presented herein have the potential to direct future targeted therapeutics for classic EDS patients. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2707-2715, 2017.

The interaction of polymorphisms in extracellular matrix genes and underlying miRNA motifs that modulate susceptibility to anterior cruciate ligament rupture

OBJECTIVES

Variants within genes that encode proteins regulating fibrillogenesis such as BGN (rs1126499 C>T, rs1042103 C>T), COL5A1 (rs12722 C>T) and DCN (rs516115 C>T) have been associated with susceptibility to anterior cruciate ligament (ACL) ruptures. A miRNA mediated transcript instability was proposed for the COL5A1 association. The study aims were: (i) to investigate the association of inferred allele combinations across the COL5A1 3'-UTR, BGN and DCN genes with susceptibility to ACL rupture; and (ii) to use an in silico approach to identify miRNA binding sites common to these risk associated allele combinations.

DESIGN

Case-control association study METHODS: Allele combinations were generated from the genotype data of the BGN (rs1126499, rs1042103), COL5A1 (rs12722) and DCN (rs516115) loci for 227 participants with surgically diagnosed ACL ruptures and 234 asymptomatic controls. Statistical analyses between the CON and ACL groups as well as sex-specific interactions were investigated. Significance was accepted at p<0.05. miRNA binding sites within these genes were identified using DIANA tools.

RESULTS

Several sex-specific inferred allele combinations were associated with altered susceptibility and miRNA (miR-22, miR-27b, miR-140, miR-199a, miR-199b, miR-299, miR-338 and miR-484) recognition motifs were identified in range of these susceptibility loci.

CONCLUSIONS

In conclusion, this study has implicated inferred allele combinations across BGN (rs1126499, rs1042103), COL5A1 (rs12722) and DCN (rs516115) as well as eight miRNA recognition sequences in susceptibility to ACL rupture. The biological significance of these genomic signatures needs to be explored to understand their effect on the ligaments functional capacity.

The effect of healing in the medial collateral ligament of human knee joint: A three-dimensional finite element analysis

The medial collateral ligament (MCL) is one of the main ligaments that provide knee joint with major restraints against valgus, internal, and external torque loads. The MCL injury most frequently occurs near its femoral attachment but can be healed spontaneously. Hence, the usual clinical treatment for MCL injury is conservative therapy with early controlled rehabilitation motion. However, the effect of the variations in the healing conditions of the MCL portion (i.e. near the femoral insertion) is still unclear. In this study, finite element tibiofemoral joint models with three different MCL healing conditions were analyzed under six kinds of joint loads, such as 10 and 20 N·m valgus tibial torques, 5 and 10 N·m internal tibial torques, and 5 and 10 N·m external tibial torques. The three healing conditions corresponded to the early, medium, and final (i.e. healthy) stages of the healing period, respectively. It was found that different MCL healing conditions greatly affected the main joint kinematics under valgus tibial torques, but neither the reaction force nor stress results of the MCL. The peak strain values in the MCL healing portion changed greatly under all the six loads. Moreover, all the joint kinematics, strain results, and reaction force of the MCL at the medium stage were similar to those in the healthy joint, that is, at the final healing stage. These imply that the partially healed MCL might be enough for providing the restraints for knee joints and would not lead to some high strains occurring in the MCL.

Altered dermal fibroblast behavior in a collagen V haploinsufficient murine model of classic Ehlers-Danlos syndrome

Mutations in collagen V are associated with classic Ehlers-Danlos syndrome (EDS). A significant percentage of these mutations result in haploinsufficiency for collagen V. The purpose of this work was to determine if changes in collagen V expression are associated with altered dermal fibroblast behavior contributing to the poor wound healing response. A haploinsufficient Col5a1(+/-) mouse model of EDS was utilized. In vivo wound healing studies demonstrated that mutant mice healed significantly slower than Col5a1(+/+) mice. The basis for this difference was examined in vitro using dermal fibroblast strains isolated from Col5a1(+/-) and Col5a1(+/+) mice. Fibroblast proliferation was determined for each strain by counting cells at different time points after seeding as well as using the proliferation marker Ki-67. Fibroblast attachment to collagens I and III and fibronectin also was analyzed. In addition, in vitro scratch wounds were used to analyze fibroblast wound closure. Significantly decreased fibroblast proliferation was observed in Col5a1(+/-) compared to Col5a1(+/+) fibroblasts. Our data indicate that the decreased fibroblast number was not due to apoptosis. Wildtype Col5a1(+/+) fibroblasts attached significantly better to components of the wound matrix (collagens I and III and fibronectin) than Col5a1(+/-) fibroblasts. A significant difference in in vitro scratch wound closure rates also was observed. Col5a1(+/+) fibroblasts closed wounds in 22 h, while Col5a1(+/-) fibroblasts demonstrated ~80% closure. There were significant differences in closure at all time points analyzed. Our data suggest that decreased fibroblast proliferation, extracellular matrix attachment, and migration contribute to the decreased wound healing response in classic EDS.

Reprint of: Extracellular matrix as a biological scaffold material: Structure and function

Biological scaffold materials derived from the extracellular matrix (ECM) of intact mammalian tissues have been successfully used in a variety of tissue engineering/regenerative medicine applications both in preclinical studies and in clinical applications. Although it is recognized that the materials have constructive remodeling properties, the mechanisms by which functional tissue restoration is achieved are not well understood. There is evidence to support essential roles for both the structural and functional characteristics of the biological scaffold materials. This paper provides an overview of the composition and structure of selected ECM scaffold materials, the effects of manufacturing methods upon the structural properties and resulting mechanical behavior of the scaffold materials, and the in vivo degradation and remodeling of ECM scaffolds with an emphasis on tissue function.

Characterization of collagen fibrils after equine suspensory ligament injury: an ultrastructural and biochemical approach

Suspensory ligament (SL) injuries are an important cause of lameness in horses. The mechanical properties of connective tissue in normal and pathological ligaments are mainly related to fibril morphology, as well as collagen content and types. The purpose of this study was to evaluate, using biochemical and ultrastructural approaches, the alterations in collagen fibrils after injury. Eight Warmblood horses with visible signs of injury in only one forelimb SL were selected and specimens were examined by transmission electron microscope (TEM). Collagen types I, III and V were purified by differential salt precipitation after collagen extraction with acetic acid containing pepsin. TEM revealed abnormal organization as well as alterations in the diameter and shape of fibrils after SL injury. The bands corresponding to types I, III and V collagen were assessed by densitometry after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Densitometric analysis indicated that the proportions of type III and type V collagen were higher (P < 0.001) in damaged tissues compared with normal tissues with a mean increase of 20.9% and 17.3%, respectively. Concurrently, a decrease (P < 0.001) in type I collagen within damaged tissues was recorded with a mean decrease of 15.2%. These alterations could be the hallmark of a decrease in the tissue quality and mechanical properties of the ligament. The findings provide new insight for subsequent research on tissue regeneration that may lead to the development of future treatment strategies for SL injury.

Impact of prolapse meshes on the metabolism of vaginal extracellular matrix in rhesus macaque

OBJECTIVE

The impact of polypropylene mesh implantation on vaginal collagen and elastin metabolism was analyzed using a nonhuman primate model to further delineate the mechanism of mesh induced complications.

STUDY DESIGN

Forty-nine middle-aged parous rhesus macaques underwent surgical implantation of 3 synthetic meshes via sacrocolpopexy. Gynemesh PS (n = 12) (Ethicon, Somerville, NJ) and 2 lower-weight, higher-porosity, lower-stiffness meshes (UltraPro [n = 19] [Ethicon] and Restorelle [n = 8] [Coloplast, Minneapolis, MN]) were implanted, in which UltraPro was implanted with its blue orientation lines perpendicular (low stiffness direction, n = 11) and parallel (high stiffness direction, n = 8) to the longitudinal axis of the vagina. Sham-operated animals were used as controls (n = 10). Twelve weeks after surgery, the mesh-tissue complex was excised and analyzed.

RESULTS

Relative to sham, Gynemesh PS had a negative impact on the metabolism of both collagen and elastin-favoring catabolic reactions, whereas UltraPro induced an increase only in elastin degradation. Restorelle had the least impact. As compared with sham, the degradation of collagen and elastin in the vagina implanted with Gynemesh PS was increased with a simultaneous increase in active matrix metalloproteinase (MMP)-1, -8, -13, and total MMP-2 and -9 (all P < .05). The degradation of elastin (tropoelastin and mature elastin) was increased in the UltraPro-implanted vagina with a concomitant increase of MMP-2, and -9 (all P < .05). Collagen subtype ratio III/I was increased in Gynemesh PS and UltraPro perpendicular groups (P < .05).

CONCLUSION

Following implantation with the heavier, less porous, and stiffer mesh, Gynemesh PS, the degradation of vaginal collagen and elastin exceeded synthesis, most likely as a result of increased activity of MMPs, resulting in a structurally compromised tissue.

Age-related changes in structure and extracellular matrix protein expression levels in rat tendons

The musculoskeletal system (muscle-tendon-bone) demonstrates numerous age-related changes, with modifications in tendons the least well studied, although increased predisposition to tendinopathy and rupture have been reported. In order to gain insights into the basis of age-associated increase in tendon injuries, we compared Achilles and tibialis anterior tendons and myotendinous junctions (MTJs) from 3- to 5- and 22- to 25-month-old rats for underlying structure and composition. Significant decreases were observed by qRT-PCR for collagen I, III, and V mRNA expression in tendons of old rats, but immunostaining detected no apparent differences in collagen I and V expression on the protein level. Tendons of old compared with young rats had decreased mRNA expression levels of proteoglycan 4 (PRG4) and elastin (Eln), but no differences in the mRNA expression of connective tissue growth factor, TGF-beta 1, or stromal cell-derived factor 1. For PRG4, immunostaining showed good correlation with qRT-PCR results. This is the first study to show reductions in PRG4 in tendons and MTJs of old rats. Decreased PRG4 expression in tendons could result in increased tendon stiffness and may be associated with decreased activity in the elderly. The diminished collagen mRNA expression in combination with decreased PRG4 and Eln mRNA expression may be associated with increased risk of tendon injury with aging.

Lentiviral-encoded shRNA silencing of proteoglycan decorin enhances tendon repair and regeneration within a rat model

Injured tendons often heal with scar tissue formation, resulting in uniformly smaller collagen fibrils and poor mechanical properties. The small leucine-rich proteoglycan decorin is well known to regulate fusion of collagen fibrils. Rat patellar tendon cells were transfected with lentiviral-encoded shRNA that specifically targets decorin. Silencing of decorin expression resulted in decreased cell growth. Three types of scaffold-free engineered tendons with different mix ratios of anti-decorin shRNA-treated cells to untreated cells at 1:0 (DCN), 1:1 (MIX), and 0:1 (CON) were utilized for repair of injured patellar tendons. Four weeks after implantation in situ, the MIX group manifested the best results (best coordination of histology, more mature collagen deposition, and larger collagen fibril diameter). Although the DCN group exhibited the largest collagen fibril diameter, this was associated with abnormal shape. Hence, regulation of decorin expression to an appropriate level is crucial for tendon repair with gene therapy.

Consideration of growth factors and bio-scaffolds for treatment of combined grade II MCL and ACL injury

The literature suggests that a Grade II medial collateral ligament (MCL) injury in combination with anterior cruciate ligament (ACL) injury will heal naturally and not compromise patient outcome following ACL reconstruction. Evidence based on bone-patella tendon-bone autograft use is stronger than evidence supporting anatomically placed soft tissue graft use. Current ACL reconstruction practices make greater use of soft tissue grafts, differing fixation methods, and anatomically lower placement on the inner wall of the lateral femoral condyle. Anatomical graft placement aligns the femoral bone tunnel more directly with valgus knee loading forces. Differences in the soft tissue graft-bone tunnel integration and ligamentization timetable following ACL reconstruction also increase concerns regarding residual Grade II MCL laxity and functional deficiency during accelerated functional rehabilitation. MCL dysfunction may increase susceptibility to early ACL graft slippage, elongation, outright failure, and medial femoral condyle lift-off with valgus knee loading. This concept paper discusses the potential role of growth factors and bio-scaffolds for improving Grade II MCL injury healing and mechanical integrity when the injury occurs in combination with an ACL injury that is reconstructed with a soft tissue graft and an anatomical surgical approach.

Tissue engineering approaches for the construction of a completely autologous tendon substitute

Tissue engineering is a multidisciplinary field that involves the application of the principles and methods of engineering and life sciences towards i) the fundamental understanding of structure-function relationships in normal and pathological mammalian tissues and ii) the development of biological substitutes that restore, maintain or improve tissue function. The goal of tissue engineering is to surpass the limitations of conventional treatments based on organ transplantation and biomaterial implantation. The field of tendon tissue engineering is relatively unexplored due to the difficulty in in vitro preservation of tenocyte phenotype. Only recently has mechanobiology allowed us to gain a better understanding of the fundamental role of in vitro mechanical stimuli in maintaining the phenotype of tendinous tissue. This review analyzes the techniques used so far for in vitro regeneration of tendinous tissue.

Promotion of rabbit ligament healing by local delivery of hepatocyte growth factor

BACKGROUND

Extracapsular ligament injuries of the knee and ankle are common injuries. Ligaments heal slowly, usually over months or longer by scar formation rather than by tissue regeneration. This study was performed to evaluate the therapeutic effect of locally delivered recombinant hepatocyte growth factor (HGF) on the early healing of ligaments in a rabbit model.

METHODS

Japanese white rabbits were subjected to a standardized gap injury in the medial collateral ligaments (MCLs) of both knees. Each rabbit underwent bilateral transection of the midsubstance of the MCL, which was not repaired. During postoperative days 0-6, the rabbits were injected with 10 μg human recombinant HGF into the right MCL, while the left MCL was injected with saline alone. One, 3, 6, and 12 weeks after surgery, experimental rabbits were sacrificed. The structural properties of the femur-MCL-tibia complex were then assessed and the tissue was subjected to histological evaluation. To see the distribution of cells that express c-Met receptor, the tissue was subjected to immunohistochemistry.

RESULTS

Immunohistochemical evaluation revealed that c-Met expression was observed particularly at opposing ligament ends in the HGF-treated limbs 1 week after surgery. Histological evaluation revealed earlier neovascularization and more aligned collagen fibers in the MCLs of the HGF-treated group than the control group. In mechanical evaluations, similar ligament failure modes were noted in the two groups. After 3 weeks, HGF-treated limbs had significantly improved structural properties than the paired control limbs.

CONCLUSIONS

Our findings indicate local administration of recombinant HGF promotes early steps in ligament healing and the repair of structural properties in a rabbit model. Local administration of HGF may represent a new therapeutic approach to accelerating healing and rehabilitation after ligament injury.

Col V siRNA engineered tenocytes for tendon tissue engineering

The presence of uniformly small collagen fibrils in tendon repair is believed to play a major role in suboptimal tendon healing. Collagen V is significantly elevated in healing tendons and plays an important role in fibrillogenesis. The objective of this study was to investigate the effect of a particular chain of collagen V on the fibrillogenesis of Sprague-Dawley rat tenocytes, as well as the efficacy of Col V siRNA engineered tenocytes for tendon tissue engineering. RNA interference gene therapy and a scaffold free tissue engineered tendon model were employed. The results showed that scaffold free tissue engineered tendon had tissue-specific tendon structure. Down regulation of collagen V α1 or α2 chains by siRNAs (Col5α1 siRNA, Col5α2 siRNA) had different effects on collagen I and decorin gene expressions. Col5α1 siRNA treated tenocytes had smaller collagen fibrils with abnormal morphology; while those Col5α2 siRNA treated tenocytes had the same morphology as normal tenocytes. Furthermore, it was found that tendons formed by coculture of Col5α1 siRNA treated tenocytes with normal tenocytes at a proper ratio had larger collagen fibrils and relative normal contour. Conclusively, it was demonstrated that Col V siRNA engineered tenocytes improved tendon tissue regeneration. And an optimal level of collagen V is vital in regulating collagen fibrillogenesis. This may provide a basis for future development of novel cellular- and molecular biology-based therapeutics for tendon diseases.

The process of tendon regeneration in an achilles tendon resection rat model as a model for hamstring regeneration after harvesting for anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to clarify the mechanism of tendon regeneration by investigating macroscopically, histologically, and biomechanically.

METHODS

Fifty, adult, female Sprague-Dawley rats were used. The Achilles tendon in the left hind limb was removed totally by use of the tendon-stripping device. Rats were killed at 2, 7, 30, 90, and 180 days after surgery, and the regenerate tendons were dissected. Contralateral Achilles tendons were used as normal controls. Gross anatomic changes, microscopic remodeling, and recovery of biomechanical properties of regenerate tendons were investigated. The expressions of type I collagen, type III collagen, and transforming growth factor β1 were also investigated by immunohistochemistry.

RESULTS

The regenerate tendons formed in all specimens. In the early phase, hematoma and soft granulation tissue were observed at the harvest defect. These gradually matured with time, and the microscopic structure became quite similar to normal at 180 days after surgery. These findings occurred uniformly along the entire length of the regenerate tendon. However, the biomechanical properties were significantly inferior to the normal tendons (P < .05). Transforming growth factor β1 was well co-localized with inflammatory cells and fibroblasts in the regenerate tendons. The type I-type III collagen ratio in the regenerate tendon was significantly decreased in the early phase (P < .05) but gradually increased with time.

CONCLUSIONS

Tendon regeneration and maturation occurred uniformly along the length of regenerate tendons. The hematoma that initially occupies the harvest defect acted as a scaffold for fibroblast precursor cells from the surrounding peritendinous tissue and tendon sheath. The mechanical properties of regenerate tendon were significantly inferior to contralateral control even at 180 days after surgery, and the alteration of the collagen composition would have an influence on mechanical properties of regenerate tendon.

CLINICAL RELEVANCE

Clinicians should be cautious about using reharvested hamstring tendons for ligament reconstruction surgery.

Parity negatively impacts vaginal mechanical properties and collagen structure in rhesus macaques

OBJECTIVE

The purpose of this study was to determine the impact of parity on mechanical behavior of the vagina and to correlate these findings with alterations in collagen structure.

STUDY DESIGN

Mechanical properties of 5 nulliparous and 6 parous rhesus macaques were derived from uniaxial tensile tests. Collagen ratios and alignment were quantified by quantitative fluorescent microscopy and picrosirius red staining. Outcomes were compared by the Student t test or Mann Whitney U test (P < .05) and Spearman's rho for correlation coefficients.

RESULTS

Mechanical properties were inferior in a parous vs nulliparous vagina with decreased tangent modulus (P = .03), tensile strength (P < .001), and strain energy density (P = .006). Although no difference in collagen ratios (P = .26) were observed, collagen alignment decreased with parity (P = .06). Worsening pelvic organ support negatively correlated with decreasing collagen alignment (r(2) = -0.66) and mechanical properties (r(2) = -0.67).

CONCLUSION

Vaginal parity is associated with inferior tissue mechanics and loss of collagen alignment. Such behavior likely predisposes to the development of pelvic organ prolapse.

Collagen scaffold: a treatment for simulated maternal birth injury in the rat model

OBJECTIVE

We sought to determine the impact of a collagen scaffold on the healing response after simulated birth injury in a rodent model.

STUDY DESIGN

A total of 52 virgin animals were divided into the following groups: control (n = 18), injured untreated (n = 18), and injured treated with porcine small intestinal submucosa (SIS) (n = 16). Histopathology, immunofluorescence of collagens, and vaginal mechanical properties were used to assess the impact of injury and the subsequent healing response.

RESULTS

Collagen I/V decreased by 44% after birth injury relative to the controls (P = .001). Birth injury resulted in inferior mechanical properties of the vagina with a decrease of 38% in the tangent modulus and 44% in the tensile strength. SIS improved the collagen I/V and I/III ratios by 28% and 46%, respectively, paralleling the trend in the mechanical properties.

CONCLUSION

Simulated birth injury negatively affected vaginal biochemical and biomechanical properties long term. SIS treatment mitigated the impact of birth injury by enhancing tissue quality.

Functional tissue engineering of ligament healing

Ligaments and tendons are dense connective tissues that are important in transmitting forces and facilitate joint articulation in the musculoskeletal system. Their injury frequency is high especially for those that are functional important, like the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) of the knee as well as the glenohumeral ligaments and the rotator cuff tendons of the shoulder. Because the healing responses are different in these ligaments and tendons after injury, the consequences and treatments are tissue- and site-specific. In this review, we will elaborate on the injuries of the knee ligaments as well as using functional tissue engineering (FTE) approaches to improve their healing. Specifically, the ACL of knee has limited capability to heal, and results of non-surgical management of its midsubstance rupture have been poor. Consequently, surgical reconstruction of the ACL is regularly performed to gain knee stability. However, the long-term results are not satisfactory besides the numerous complications accompanied with the surgeries. With the rapid development of FTE, there is a renewed interest in revisiting ACL healing. Approaches such as using growth factors, stem cells and scaffolds have been widely investigated. In this article, the biology of normal and healing ligaments is first reviewed, followed by a discussion on the issues related to the treatment of ACL injuries. Afterwards, current promising FTE methods are presented for the treatment of ligament injuries, including the use of growth factors, gene delivery, and cell therapy with a particular emphasis on the use of ECM bioscaffolds. The challenging areas are listed in the future direction that suggests where collection of energy could be placed in order to restore the injured ligaments and tendons structurally and functionally.

Genetics and sports

INTRODUCTION

The limit of each individual to perform a given type of exercise depends on the nature of the task, and is influenced by a variety of factors, including psychology, environment and genetic make up. Genetics provide useful insights, as sport performances can be ultimately defined as a polygenic trait.

SOURCES OF DATA

We searched PubMed using the terms 'sports' and 'genetics' over the period 1990 to present.

AREAS OF AGREEMENT

The physical performance phenotypes for which a genetic basis can be suspected include endurance capacity, muscle performance, physiological attitude to train and ability of tendons and ligaments to withstand injury. Genetic testing in sport would permit to identify individuals with optimal physiology and morphology, and also those with a greater capacity to respond/adapt to training and a lesser chance of suffering from injuries.

AREAS OF CONTROVERSY

Ethical and practical caveats should be clearly emphasized. The translation of an advantageous genotype into a champion's phenotype is still influenced by environmental, psychological and sociological factors.

EMERGING AREAS FOR DEVELOPING RESEARCH

The current scientific evidence on the relationship between genetics and sports look promising. There is a need for additional studies to determine whether genome-wide genotyping arrays would be really useful and cost-effective. Since exercise training regulates the expression of genes encoding various enzymes in muscle and other tissues, genetic research in sports will help clarify several aspects of human biology and physiology, such as RNA and protein level regulation under specific circumstances.

The COL5A1 gene is associated with increased risk of anterior cruciate ligament ruptures in female participants

BACKGROUND

Anterior cruciate ligament ruptures, especially to young female athletes, are a cause of major concern in the sports medicine fraternity. The major structural constituents of ligaments are collagens, specifically types I and V. Recently, the gene that encodes for the alpha1 chain of type I collagen (COL1A1) has been shown to be associated with an increased risk of cruciate ligament ruptures. The COL5A1 gene, which encodes for the alpha1 chain of type V collagen, has been shown to be associated with Achilles tendon injuries.

PURPOSE

The study was conducted to determine (1) if 2 sequence variants (BstUI and DpnII restriction fragment length polymorphisms [RFLPs]) within the COL5A1 gene are associated with an increased risk of anterior cruciate ligament ruptures, and (2) if there were any gender-specific positive associations between the 2 COL5A1 sequence variants and risk of anterior cruciate ligament ruptures.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

A total of 129 white participants (38 women) with surgically diagnosed anterior cruciate ligament ruptures and 216 physically active control participants (84 women) without any history of ACL injury were included in this case-control genetic association study. All participants were genotyped for the COL5A1 BstUI and DpnII RFLPs.

RESULTS

There was a significant difference in the BstUI RFLP genotype frequency between the anterior cruciate ligament rupture and physically active control groups among the female participants, but not the male participants. The CC genotype in the female participants was significantly underrepresented in the anterior cruciate ligament rupture group compared with the controls (27.4% vs 5.6%; odds ratio = 6.6; 95% confidence interval, 1.5-29.7; P = .006). There were no differences in the DpnII RFLP genotype distributions between the anterior cruciate ligament rupture and physically active control groups.

CONCLUSION

The CC genotype of the COL5A1 BstUI RFLP was underrepresented in female participants with anterior cruciate ligament ruptures.

CLINICAL RELEVANCE

This is the first study to show that there is a specific genetic risk factor associated with risk of anterior cruciate ligament ruptures in female athletes.

Role of biomechanics in the understanding of normal, injured, and healing ligaments and tendons

Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and deceleration. These injuries often upset this balance between mobility and stability of the joint which causes damage to other soft tissues manifested as pain and other morbidity, such as osteoarthritis.

The healing of ligament and tendon injuries varies from tissue to tissue. Tendinopathies are ubiquitous and can take up to 12 months for the pain to subside before one could return to normal activity. A ruptured medial collateral ligament (MCL) can generally heal spontaneously; however, its remodeling process takes years and its biomechanical properties remain inferior when compared to the normal MCL. It is also known that a midsubstance anterior cruciate ligament (ACL) tear has limited healing capability, and reconstruction by soft tissue grafts has been regularly performed to regain knee function. However, long term follow-up studies have revealed that 20–25% of patients experience unsatisfactory results. Thus, a better understanding of the function of ligaments and tendons, together with knowledge on their healing potential, may help investigators to develop novel strategies to accelerate and improve the healing process of ligaments and tendons.

With thousands of new papers published in the last ten years that involve biomechanics of ligaments and tendons, there is an increasing appreciation of this subject area. Such attention has positively impacted clinical practice. On the other hand, biomechanical data are complex in nature, and there is a danger of misinterpreting them. Thus, in these review, we will provide the readers with a brief overview of ligaments and tendons and refer them to appropriate methodologies used to obtain their biomechanical properties. Specifically, we hope the reader will pay attention to how the properties of these tissues can be altered due to various experimental and biologic factors. Following this background material, we will present how biomechanics can be applied to gain an understanding of the mechanisms as well as clinical management of various ligament and tendon ailments. To conclude, new technology, including imaging and robotics as well as functional tissue engineering, that could form novel treatment strategies to enhance healing of ligament and tendon are presented.

Effects of cell seeding and cyclic stretch on the fiber remodeling in an extracellular matrix-derived bioscaffold

The porcine small intestine submucosa, an extracellular matrix-derived bioscaffold (ECM-SIS), has been successfully used to enhance the healing of ligaments and tendons. Since the collagen fibers of ECM-SIS have an orientation of +/- 30 degrees , its application in improving the healing of the parallel-fibered ligament and tendon may not be optimal. Therefore, the objective was to improve the collagen fiber alignment of ECM-SIS in vitro with fibroblast seeding and cyclic stretch. The hypothesis was that with the synergistic effects of cell seeding and mechanical stimuli, the collagen fibers in the ECM-SIS can be remodeled and aligned, making it an improved bioscaffold with enhanced conductive properties. Three experimental groups were established: group I (n = 14), ECM-SIS was seeded with fibroblasts and cyclically stretched; group II (n = 13), ECM-SIS was seeded with fibroblasts but not cyclically stretched; and group III (n = 8), ECM-SIS was not seeded with fibroblasts but cyclically stretched. After 5 days' experiments, the scaffolds from all the three groups (n = 9 for group I; n = 8 for groups II and III) were processed for quantification of the collagen fiber orientation with a small-angle light scattering (SALS) system. For groups I and II, in which the scaffolds were seeded with fibroblasts, the cell morphology and orientation and newly produced collagen fibrils were examined with confocal fluorescent microscopy (n = 3/group) and transmission electronic microscopy (n = 2/group). The results revealed that the collagen fiber orientation in group I was more aligned closer to the stretching direction when compared to the other two groups. The mean angle decreased from 25.3 degrees to 7.1 degrees (p < 0.05), and the associated angular dispersion was also reduced (37.4 degrees vs. 18.5 degrees , p < 0.05). In contrast, groups II and III demonstrated minimal changes. The cells in group I were more aligned in the stretching direction than those in group II. Newly produced collagen fibrils could be observed along the cells in both groups I and II. This study demonstrated that a combination of fibroblast seeding and cyclic stretch could remodel and align the collagen fiber orientation in ECM-SIS bioscaffolds. The better-aligned ECM-SIS has the prospect of eliciting improved effects on enhancing the healing of ligaments and tendons.

Effects of a bioscaffold on collagen fibrillogenesis in healing medial collateral ligament in rabbits

Bioscaffolds have been successfully used to improve the healing of ligaments and tendons. In a rabbit model, the application of porcine small intestine submucosa (SIS) to the healing medial collateral ligament (MCL) resulted in improved mechanical properties with the formation of larger collagen fibrils. Thus, the objective of the study was to find out whether the SIS bioscaffold could improve the gene expressions of fibrillogenesis-related molecules, specifically, collagen types I, III, V, and small leucine-rich proteoglycans including decorin, biglycan, lumican, and fibromodulin, as well as collagen fibril morphology and organization, in the healing rabbit MCL at an early time point (6 weeks postinjury). Twenty skeletally mature rabbits were equally divided into two groups. In the SIS-treated group, a 6-mm gap was surgically created and a layer of SIS was sutured to cover the gap, whereas the gap was left open in the nontreated group. At 6 weeks postinjury, Masson's trichrome staining showed that the SIS-treated group had more regularly aligned collagen fibers and cells. Transmission electron microscopy revealed that the SIS-treated group had larger collagen fibrils with a diameter distribution from 24 to 120 nm, whereas the nontreated group had only small collagen fibrils (ranging from 26 to 87 nm, p < 0.05). Finally, the quantitative real-time PCR showed that the mRNAs of collagen type V, decorin, biglycan, and lumican in the SIS-treated group were 41, 58, 51, and 43% lower than those in the nontreated group, respectively (p < 0.05). Such significant reduction in the gene expressions are closely related to the improved morphological characteristics, which are known to be coupled with better mechanical properties, as previously reported in longer term studies.

HGF suppresses the production of collagen type III and alpha-SMA induced by TGF-beta1 in healing fibroblasts

The aim of this study was to examine the effectiveness of HGF in blocking TGF-beta1-induced collagen III and alpha-smooth muscle actin (alpha-SMA) production in rat healing fibroblasts, fibroblasts were obtained from healing medial collateral ligament (MCL) injury. Cell culture was supplemented with 5 ng/ml of TGF-beta1 along with increasing doses of HGF (10-40 ng/ml). The productions of collagen III in supernatants culture were assayed by enzyme-linked immunosorbent assay. Expression of alpha-SMA was assessed by Western blot. Treatment with TGF-beta1 significantly stimulated collagen III and alpha-SMA production in healing fibroblasts. Remarkably, the addition of HGF reduced productions of all components induced by TGF-beta1 in a dose-dependent manner. This study shows that HGF antagonizes the action of TGF-beta1 effectively in cultured healing MCL injury fibroblasts. The results provide a cellular and molecular basis for HGF's acting as a therapeutic agent for MCL scar formation and poor healing.

Systemic vanadate ingestion improves early medial collateral ligament repair

The medial collateral ligament (MCL) of the knee is frequently injured in sport. Repair is slow and often complicated by scar formation which may result in impairment of function. Vanadate is a promising efficacious treatment for tissue injuries and this study aimed to examine its effect in rats on the histological and biomechanical features of MCL healing. Rats received either 0.025 g/kg per day vanadate or equivalent amounts of drinking water (control) by intragastric gavage for 1 week before and 2 weeks after wounding. Repaired sites were dissected out for histological and biomechanical tests 28 days after wounding. Fibre bundles in the vanadate-treated group were uniform and evenly spaced. Furthermore, vanadate significantly increased the diameter of collagen fibrils in the healing tissue. Stiffness and ultimate force of the femur-medial collateral ligament-tibia complex for the vanadate-treated group were significantly higher than for the controls. The results suggest that vanadate significantly improves the histological and biomechanical properties of healing MCL.

Genetic aspects of tendinopathy

Tendinopathy is characterised by a disorganised, haphazard healing response with no histological signs of inflammation. Research on tendon injuries is limited to the description of the condition and its management, and the pathogenesis is still ill defined. Together with known intrinsic and extrinsic factors, genetics may play a significant role in the aetiopathogenesis of tendinopathy. ABO and other closely linked genes, COL5A1, and tenascin-C have all been implicated in the aetiopathogenesis of tendinopathy. However, the precise role of these genes in causing or protecting individuals from developing tendinopathy is yet to be defined. An interaction between the various intrinsic and extrinsic factors with the genetic make-up of an individual may increase the likelihood of one individual developing tendinopathy over another. Tendinopathy may well be polygenic, involving complex interactions between multiple genes, and could possibly run in families. Further investigations should determine the exact role played by genetic influences in maintaining tendon homeostasis and pave the way for gene transfer therapy to be developed for the management of tendinopathies.

Remodeling of vaginal connective tissue in patients with prolapse

PURPOSE OF REVIEW

Pelvic organ prolapse is a common disease that negatively affects the lives of women. To date, basic science research into the pathogenesis of prolapse has been limited. The vagina and its supportive connective tissues provide one of the primary mechanisms of support to the pelvic organs. This review summarizes our current understanding of the alterations in these tissues in women with prolapse.

RECENT FINDINGS

Current research suggests that the vagina and its supportive tissues actively remodel in response to different environmental stimuli. The literature has many shortcomings due to restricted access to tissue, absence of longitudinal data, and limited animal models. Nevertheless, recent studies indicate that within prolapsed tissue metabolism of collagen and elastin is altered. Thus, not only the synthesis of those structural proteins but also the balance between the activity of the major proteolytic enzymes that degrade them and the inhibitors of proteolysis are important components to consider in studies on the pathogenesis of pelvic organ prolapse.

SUMMARY

Biochemical studies of the vagina and its supportive connective tissues have improved understanding of the contribution of altered connective tissue to the pathogenesis of prolapse. It is important to continue research in this area, as the knowledge gained from these studies will allow for the development of innovative reconstructive procedures and the establishment of preventive measures.

Effect of dermatan sulfate glycosaminoglycans on the quasi-static material properties of the human medial collateral ligament

The glycosaminoglycan of decorin, dermatan sulfate (DS), has been suggested to contribute to the mechanical properties of soft connective tissues such as ligaments and tendons. This study investigated the mechanical function of DS in human medial collateral ligaments (MCL) using nondestructive shear and tensile material tests performed before and after targeted removal of DS with chondroitinase B (ChB). The quasi-static elastic material properties of human MCL were unchanged after DS removal. At peak deformation, tensile and shear stresses in ChB treated tissue were within 0.5% (p>0.70) and 2.0% (p>0.30) of pre-treatment values, respectively. From pre- to post-ChB treatment under tensile loading, the tensile tangent modulus went from 242+/-64 to 233+/-57 MPa (p=0.44), and tissue strain at peak deformation went from 4.3+/-0.3% to 4.4+/-0.3% (p=0.54). Tissue hysteresis was unaffected by DS removal for both tensile and shear loading. Biochemical analysis confirmed that 90% of DS was removed by ChB treatment when compared to control samples, and transmission electron microscopy (TEM) imaging further verified the degradation of DS by showing an 88% reduction (p<.001) of sulfated glycosaminoglycans in ChB treated tissue. These results demonstrate that DS in mature knee MCL tissue does not resist tensile or shear deformation under quasi-static loading conditions, challenging the theory that decorin proteoglycans contribute to the elastic material behavior of ligament.

Gene Expression by Fibroblasts Seeded on Small Intestinal Submucosa and Subjected to Cyclic Stretching

Extracellular matrix scaffolds derived from porcine small intestinal submucosa (SIS-ECM) have been shown to promote the formation of site-specific tissue in a number of preclinical animal studies. However, this constructive remodeling process requires that the scaffold be subjected to a site-specific mechanical environment. The specific quantitative effects of mechanical loading on the gene expression patterns of fibroblasts seeded on SIS-ECM are unknown and yet very important in the tissue remodeling process. The objective of the present study was to evaluate the expression of collagen type I (Col I), collagen type III (Col III), smooth muscle actin (SMA), tenascin-C (TN-C), matrix metalloprotease-2 (MMP-2), matrix metalloprotease-9 (MMP-9), transforming growth factor-beta1 (TGF-beta1), and transforming growth factor-beta3 (TGF-beta3) by fibroblasts subjected to various magnitudes (0%, 5%, 10%, and 15%) and frequencies (0.1 Hz, 0.3 Hz, and 0.5 Hz) of stretch. A new cyclic-stretching tissue culture (CSTC) system was developed. This system consists of eight independently controlled culture chambers that can be operated in a sterile incubator. Each chamber includes a load cell so that the load in each scaffold can be monitored. It was found that different stretching regimens led to complex and distinctive patterns of gene expression by fibroblasts seeded onto SIS-ECM. In general, the fibroblasts increased expression of Col I up to 5-fold and decreased that of Col III with increased frequency of stretch. In addition, the fibroblasts exhibited a contractile phenotype with increased expression of SMA, TN-C, and TGF-beta1. These findings support the concept that the mechanical environment of a remodeling ECM scaffold may have substantial effects on the behavior of cells within the scaffold and contribute to the site-specific tissue remodeling that has been observed in in vivo studies.

Adaptations of the rat vagina in pregnancy to accommodate delivery

OBJECTIVE

To characterize ultrastructural changes in the rat vagina in pregnancy, delivery, and postpartum, focusing on collagen architecture and smooth muscle cell morphology.

METHODS

The vagina of four virgin, four midpregnant, four late pregnant, four immediate, and four late post-vaginal-delivery rats were examined by transmission electron microscopy. Images were classified into one of four categories based on collagen fibril area fraction, with group 1 containing the highest number of collagen fibers per unit area and group 4 containing the lowest. Smooth muscle cells were characterized into three cell types ("synthetic," "intermediate," and "contractile") based on the volume fraction of cytoplasm occupied by organelles compared with myofibrils.

RESULTS

Quantitative analysis demonstrated that 76% of collagen fibers in virgin rats were categorized as group 1 or 2 compared with 49% in midpregnant, 40% in late pregnant, and 23% in immediate postpartum animals (P=0.006). Late postpartum tissue seemed similar to virgin tissue (77%). Midpregnant (37%), late-pregnant (34%) and immediate postpartum animals (43%) contained a higher proportion of synthetic smooth muscle cells compared with virgins (20%) and late postpartum animals (21%) (P=.02). Contractile smooth muscle cells predominated in virgin (64%) and late postpartum animals (70%) compared with midpregnant (42%), late pregnant (50%) and immediate postpartum (50%, P=.05).

CONCLUSION

In pregnancy, collagen fiber area decreased while smooth muscle cells transformed from a contractile to a synthetic phenotype. The late postpartum period returned to prepregnant levels for both collagen and smooth muscle cell morphologies. It is likely that these changes represent adaptations to minimize trauma to the vagina during passage of the fetus.

A simple cell motility assay demonstrates differential motility of human periodontal ligament fibroblasts, gingival fibroblasts, and pre-osteoblasts

During periodontal regeneration, multiple cell types can invade the wound site, thereby leading to repair. Cell motility requires interactions mediated by integrin receptors for the extracellular matrix (ECM), which might be useful in guiding specific cell populations into the periodontal defect. Our data demonstrate that fibroblasts exhibit differential motility when grown on ECM proteins. Specifically, gingival fibroblasts are twice as motile as periodontal ligament fibroblasts, whereas osteoblasts are essentially non-motile. Collagens promote the greatest motility of gingival fibroblasts in the following order: collagen III>collagen V>collagen I. Differences in motility do not correlate with cell proliferation or integrin expression. Osteoblasts display greater attachment to collagens than does either fibroblast population, but lower motility. Gingival fibroblast motility on collagen I is generally mediated by alpha2 integrins, whereas motility on collagen III involves alpha1 integrins. Other integrins (alpha10 or alpha11) may also contribute to gingival fibroblast motility. Thus, ECM proteins do indeed differentially promote the cell motility of periodontal cells. Because of their greater motility, gingival fibroblasts have more of a potential to invade periodontal wound sites and to contribute to regeneration. This finding may explain the formation of disorganized connective tissue masses rather than the occurrence of the true regeneration of the periodontium.