Medial Collateral Ligament Healing Research Articles

Role of angiogenesis after muscle derived stem cell transplantation in injured medial collateral ligament

We performed this study to investigate the therapeutic role of vascular endothelial growth factor (VEGF) in medial collateral ligament (MCL) healing. Murine muscle derived stem cells (MDSCs) obtained via the preplate technique were retrovirally transduced to express: (1) VEGF and nLacZ (MDSC-VEGF), (2) soluble fms-like tyrosine kinase-1 (sFLT1, a VEGF-specific antagonist) and nLacZ (MDSC-sFLT1), and (3) nLacZ (MDSC-nLacZ). After transecting the MCL of immunodeficient rats, 5 × 10(5) cells of each of the transduction groups list above were transplanted into the MCL injury site. A control group was injected with phosphate-buffered saline (PBS) only. Immunohistochemical staining demonstrated that there were more Isolectin B4 and β-galactosidase double positive cells in the rats transplanted with MDSC-VEGF transduced cells than the other groups at week 1. Capillary density was significantly higher in the MDSC-VEGF group than the other groups at week 2; however, there were no significant differences in the biomechanical assessment between the MDSC-VEGF and MDSC-nLacZ groups. On the other hand, the MDSC-sFLT1 group revealed a lower capillary density than the other two groups and the functional ligament healing of the MDSC-sFLT1 group was significantly decreased compared to the other groups when assessed biomechanically. The findings of the present study suggest that angiogenesis plays a critical role in the healing process of injured MCL.

Wound healing differences between Yorkshire and red Duroc porcine medial collateral ligaments identified by biomechanical assessment of scars

BackgroundCurrently, there are no large animal models to assess potential genetic contributions to ligament biomechanics during an injury repair response. Yorkshire and red Duroc pigs display phenotypically and genetically different skin wound healing responses; red Duroc skin scars were hyper-contracted and hyper-pigmented, whereas Yorkshire skin scars were not. Such findings raise the question whether connective tissues of synovial joints display a similar differential healing response in these pig breeds. This study assessed medial collateral ligament healing in Yorkshire and red Duroc pigs at the functional (biomechanical) level. MethodsSurgical injury was created in the right hind limb medial collateral ligament of Yorkshire and red Duroc pigs. After 10weeks of healing, low-load (laxity and creep) and high-load (failure) mechanical properties were measured. FindingsLarge, complete ligament scars formed by 10weeks post-injury. A differential healing response was observed between the breeds, where red Duroc ligament scars had larger cross-sectional areas, exhibited greater static and total creep responses, failed at greater deformations and strains (P≤0.05), and failed with strong trends for higher loads and lower moduli (P=0.06) than Yorkshire ligament scars. InterpretationThe ligament healing response of red Duroc pigs differs from Yorkshire pigs. Previously observed breed differences in dorsal skin wound healing are not restricted to skin. Such findings support a genetic basis for breed differences in response to connective tissue injury. Since this animal model is physiologically comparable to humans, these findings could provide further insight into identification of specific genetic contributions to ligament repair in human populations.

Hyperbaric oxygen therapy improves medial collateral ligament healing in a rabbit model

Hyperbaric oxygen (HBO) therapy has been shown to enhance bone, muscle, skin, and wound healing, particularly in conditions of ischemia and low oxygen tension. Preliminary data show that HBO therapy may be beneficial in the treatment of muscle–tendon and ligament injury. However, the effects of HBO therapy on ligament healing have not been thoroughly investigated. The purpose of this study was to assess the effects of HBO on the healing of the medial collateral ligament (MCL) by using biomechanical and histological analyses in a rabbit model. We investigated the effects of intermittent HBO therapy on ligamentous healing in rabbits. Sixty-four male rabbits were divided into eight groups consisting of eight animals each. The experimental group (32 rabbits) was subjected to HBO at 2.5 atmospheres absolute for 2 hours per day, whereas the control group (32 rabbits) did not undergo HBO therapy. All animals underwent a standardized surgical severance of the right MCL, whereas the left MCL was not surgically lacerated. Rabbits from each group were euthanized at 2, 4, 8, and 12 weeks postoperatively for biomechanical testing (six rabbits) and histological analysis (two rabbits). By using the intact left MCL as a control, the mean percentages of failure load calculated at 2, 4, 8, and 12 weeks in the HBO group were 20.6%, 49.1%, 63.9%, and 76.3%, respectively, whereas in the non-HBO group, the mean percentages of failure load at 2, 4, 8, and 12 weeks were 13.5%, 25.3%, 36.5%, and 57.3%, respectively. For all time intervals, the mean percent failure load of the severed MCLs from the HBO group was significantly higher than that from the non-HBO group. The mean percentages of regenerative collagen fibers in the HBO group at 2, 4, 8, and 12 weeks were 53.2%, 75%, 87.8%, and 95.1%, respectively, and 32.4%, 55.7%, 72.4%, and 82%, respectively, in the non-HBO group. For all time intervals, the HBO group showed a significantly higher amount of regenerative collagen fibers than the non-HBO group. The present study results suggest that the healing of the MCL is enhanced by intermittent HBO therapy. HBO therapy may be useful in shortening the healing time of the injured ligaments.

Smoking and Mouse MCL Healing

Cigarette smoking has been shown to delay soft tissue healing and complicate musculoskeletal recovery. Its deleterious effects have been proven in bone and soft tissue, although to a much more limited fashion in ligament or tendon. We exposed 120 experimental mice to two cigarettes per day for 2 months and then induced a blunt medial collateral ligament (MCL) injury. Mice were assigned to three groups: the first group exposed to two cigarettes per day after injury, the second group exposed to one cigarette per day after injury, and the third group not exposed after injury. A fourth, no-smoking group served as control. The cut and contralateral intact ligaments were biomechanically tested to failure at 7 and 28 days. The ligaments of mice exposed to cigarette smoke were weaker (p = 0.02) and less stiff (p = 0.0004) at 28 days (3.2 N, 3.5 N/mm) compared with those of mice exposed to cigarette smoke for 7 days (3.9 N, 4.7 N/mm). The ligaments of mice exposed to cigarette smoke were weaker (p = 0.02) and less stiff (p = 0.01) at 28 days compared with control mice at 28 days. Between 7 and 28 days, smoking had a deleterious effect on healing manifested as weaker and less stiff ligaments. However, our findings did not support a dose-dependent effect of cigarette exposure on the tensile mechanical properties of ligaments.

Molecular events surrounding collagen fibril assembly in the early healing rabbit medial collateral ligament—failure to recapitulate normal ligament development

Although injuries to the medial collateral ligament (MCL) can heal functionally without surgical intervention, the collagen fibers in the healing tissue remain compromised. The molecular basis for this poor healing potential was investigated by examining extracellular matrix-modifying molecules such as bone morphogenetic protein 1 (BMP-1), procollagen C proteinase enhancer (PCOLCE), lysyl oxidase (LOX), and transforming growth factor beta 1 (TGF-β1) involved in collagen fibrillogenesis during normal early postnatal ligament maturation and at comparable intervals after MCL injury. Samples of midsections of rabbit MCLs were collected from 3-, 6-, 14-, and 52-week-old normal animals and at 3, 6, and 14 weeks postinjury.Harvested midsubstance tissues were analyzed for collagen fibril diameter by transmission electron microscopy (TEM), and mRNA levels were assessed by reverse transcription-polymerase chain reaction (RT-PCR). Results showed different patterns of expression between normal MCL maturation and during scar maturation. BMP-1 and PCOLCE mRNA levels were upregulated in the 3–14-week period during maturation of normal ligaments but decreased at skeletal maturity. The scar tissue exhibited a 3.5-fold increase in PCOLCE mRNA levels during the early healing phase, but these decreased with time. After injury, BMP-1 mRNA levels in scars were low and did not change during healing. Both LOX and TGF-β1 mRNA levels were low during normal MCL development compared with levels at maturity and exhibited elevated mRNA levels during early healing that decreased with time postinjury. These results suggest that gene expression in scars during MCL healing does not recapitulate expression in normal ligament fibroblasts during maturation.

Combined use of bFGF and GDF-5 enhances the healing of medial collateral ligament injury

Basic fibroblast growth factor (bFGF) and growth and differentiation factor (GDF)-5 stimulate the healing of medial collateral ligament (MCL) injury. However, the effect of isolated and combined use of bFGF/GDF-5 remains still unclear. We investigated cellular proliferation and migration responding to bFGF/GDF-5 using rabbit MCL fibroblasts. Rabbit MCL injury was treated by bFGF and/or GDF-5 with peptide hydrogels. Gene expression and deposition of collagens in healing tissues were evaluated. bFGF/GDF-5 treatment additively enhanced cell proliferation and migration. bFGF/GDF-5 hydrogels stimulated Col1a1 expression without increasing Col3a1 expression. Combined use of bFGF/GDF-5 stimulated type I collagen deposition and the reorganization of fiber alignment, and induced better morphology of fibroblasts in healing MCLs. Our study indicates that combined use of bFGF/GDF-5 might enhance MCL healing by increasing proliferation and migration of MCL fibroblasts, and by regulating collagen synthesis and connective fiber alignment.

α-Smooth muscle actin and TGF-β receptor I expression in the healing rabbit medial collateral and anterior cruciate ligaments

The aim of our study was to advance the knowledge about the biological differences in the healing of the anterior cruciate ligament (ACL) versus the medial collateral ligament (MCL). We quantified α-smooth muscle actin (α-SMA) expression and TGF-β receptor I (TGF-βRI) expression in experimentally injured rabbit ligaments (from day 3 to 12 weeks post-injury). Myofibroblasts (α-SMA positive cells) were identified as early as the third day post-injury in MCL and their density increased steadily up to day 21. Myofibroblasts were also detected in injured ACL but their density remained very low at all time points. The percentage of positive TGF-βRI area significantly increased in both injured ligaments compared to controls, with a peak expression at day 21; however, it remained constantly lower in ACL compared to MCL. A significant correlation was found between the percentage of TGF-βRI positive cells and the percentage of α-SMA expression only in injured MCL. These results provide evidence that myofibroblasts are important players in MCL remodelling after injury. The combined presence of myofibroblasts and TGF-βRI in the first 3 weeks post-MCL injury may partially explain the difference in the MCL and ACL healing process.

Pentadecapeptide BPC 157 (PL 14736) improves ligament healing in the rat

We improved medial collateral ligament (MCL) healing throughout 90 days after surgical transection. We introduced intraperitoneal, per-oral (in drinking water) and topical (thin cream layer) peptide therapy always given alone, without a carrier. Previously, as an effective peptide therapy, stable gastric pentadecapeptide BPC 157 (GEPPPGKPADDAGLV, an anti-ulcer peptide effective in inflammatory bowel disease therapy (PL 14736)) particularly improved healing of transected tendon and muscle and wound healing effect including the expression of the early growth response 1 (egr-1) gene. After MCL transection BPC 157 was effective in rats when given once daily intraperitoneally (10 microg or 10 ng/kg) or locally as a thin layer (1.0 microg dissolved in distilled water/g commercial neutral cream) at the site of injury, first application 30 min after surgery and the final application 24 h before sacrifice. Likewise, BPC 157 was effective given per-orally (0.16 microg/ml in the drinking water (12 ml/day/rat)) until sacrifice. Commonly, BPC 157 microg-ng-rats exhibited consistent functional, biomechanical, macroscopic and histological healing improvements. Thus, we suggest BPC 157 improved healing of acute ligament injuries in further ligament therapy.

The effect of pulsed ultrasound on medial collateral ligament repair

Objective To investigate the effect of pulsed ultrasound therapy (US) on medial collateral liga-ment healing in rats and it's mechanism. Methods Eighteen 3-month-old male Sprague-Dawley rats with transected medial collateral ligaments (MCLs) were studied. They were randomly divided into a control group, a 0.5 W/cm~2 group and a 1. 0 W/cm~2 group. The control group was not given any treatment. The 0. 5 W/cm~2 group and 1.0 W/cm~2 group were given 10 minutes of pulsed US (duty cycle: on/off = 3 ms/1 ms) daily for 8 days at either 0.5 or 1.0 W/cm~2 intensity. All the rats were sacrificed on the 9th day. After macroscopic examination, their MCLs were harvested and studied using haematoxylin-eosin staining, Van Gieson's staining and immunohistochemical tech-niques in order to detect transforming growth factor beta-1(TGF-β1) and any histological or histochemical changes.Results Macroscopically, the lacerated MCLs had healed with scar tissue formation. Scarring appeared to be greater in the 0.5 W/cm~2 and 1.0 W/cm~2 groups than in the control group. Inflamed cells appeared to be more numerous in the treated groups than in the controls. There were significant differences in collagen fiber extent among all three groups. In the 1.0 W/cm~2 group, the average level of TGF-β1 was significantly up-regulated, and TGF-β1 expres-sion was higher than in the other two groups. Conclusions Pulsed US can improve ligament healing in the short term, however whether long-term treatment with US can yield further improvement is unknown. Pulsed US can in-crease the level of TGF-β1, which will be higher with higher US dosage. Pulsed US may enhance injored ligament re-pair by up-regulating TGF-β1.Objective To investigate the effect of pulsed ultrasound therapy (US) on medial collateral liga-ment healing in rats and it's mechanism. Methods Eighteen 3-month-old male Sprague-Dawley rats with transected medial collateral ligaments (MCLs) were studied. They were randomly divided into a control group, a 0.5 W/cm~2 group and a 1. 0 W/cm~2 group. The control group was not given any treatment. The 0. 5 W/cm~2 group and 1.0 W/cm~2 group were given 10 minutes of pulsed US (duty cycle: on/off = 3 ms/1 ms) daily for 8 days at either 0.5 or 1.0 W/cm~2 intensity. All the rats were sacrificed on the 9th day. After macroscopic examination, their MCLs were harvested and studied using haematoxylin-eosin staining, Van Gieson's staining and immunohistochemical tech-niques in order to detect transforming growth factor beta-1(TGF-β1) and any histological or histochemical changes.Results Macroscopically, the lacerated MCLs had healed with scar tissue formation. Scarring appeared to be greater in the 0.5 W/cm~2 and 1.0 W/cm~2 groups than in the control group. Inflamed cells appeared to be more numerous in the treated groups than in the controls. There were significant differences in collagen fiber extent among all threegroups. In the 1.0 W/cm~2 group, the average level of TGF-β1 was significantly up-regulated, and TGF-β1 expres-sion was higher than in the other two groups. Conclusions Pulsed US can improve ligament healing in the short term, however whether long-term treatment with US can yield further improvement is unknown. Pulsed US can in-crease the level of TGF-β1, which will be higher with higher US dosage. Pulsed US may enhance injored ligament re-pair by up-regulating TGF-β1. Key words: Ultrasound therapy; Medial collateral ligament; TGF-β1; Tissue repair

0441 マクロファージ遊走阻止因子遺伝子の欠損が膝内側側副靭帯損傷の治癒に与える影響 : 生体力学的評価(OS7:腱・靭帯のバイオメカニクス)

0441 マクロファージ遊走阻止因子遺伝子の欠損が膝内側側副靭帯損傷の治癒に与える影響 : 生体力学的評価(OS7:腱・靭帯のバイオメカニクス)

Effect of reconstruction on medial collateral ligament healing of knee in rabbits

Objective To provide histological evidence for clinic tendon reconstruction on severe medial collateral ligament injury in rabbits. Methods Medial collateral ligaments of two knee joints were completely incised to create own control model of MCL rupture. The operation group intimated the procedure of human being MCL reconstruction with semitendinous tendon. In the 4th,12th,16th,24th weeks, healing of MCL was observed by anatomy and the picrosirius-polarization method. Results In the 4th week, the MCL healing tissue of ex-periment group is more than control group. The average ratios of type Ⅲ collagen to Ⅰ, Ⅲ collagen in the experiment group [(0.263±0.075), (0.235±0.041), (0.210±0.045), (0.197±0.029)] were significantly lower than those in control group [(0.310±0.072), (0.286±0.045), (0.261±0.046), (0.236±0.043) ] in the 4th, 12th, 16th, 24th weeks, respectively (P < 0.05). Conclusions The semitendinons tendon reconstruction can improve MCL healing in early and middle period after injury. Key words: Medial collateral ligament; knee/SU; Tendons/SU

Instrument-Assisted Cross-Fiber Massage Accelerates Knee Ligament Healing

Controlled laboratory study. To investigate the effects of instrument-assisted cross-fiber massage (IACFM) on tissue-level healing of knee medial collateral ligament (MCL) injuries. Ligament injuries are common and significant clinical problems for which there are few established interventions. IACFM represents an intervention that may mediate tissue-level healing following ligament injury. Bilateral knee MCL injuries were created in 51 rodents, while 7 rodents were maintained as ligament-intact, control animals. IACFM was commenced 1 week following injury and introduced 3 sessions per week for 1 minute per session. IACFM was introduced unilaterally (IACFM-treated), with the contralateral, injured MCL serving as an internal control (nontreated). Thirty-one injured animals received 9 ACFM treatments, while the remaining 20 injured animals received 30 treatments. Ligament biomechanical properties and morphology were assessed at either 4 or 12 weeks postinjury. IACFM-treated ligaments were 43.1% stronger (P<.05), 39.7% stiffer (P<.01), and could absorb 57.1% more energy before failure (P<.05) than contralateral, injured, nontreated ligaments at 4 weeks postinjury. On histological and scanning electron microscopy assessment, IACFM-treated ligaments appeared to have improved collagen fiber bundle formation and orientation within the scar region than nontreated ligaments. There were minimal differences between IACFM-treated and contralateral, nontreated ligaments at 12 weeks postinjury, although IACFM-treated ligaments were 15.4% stiffer (P<.05). IACFM-accelerated ligament healing, possibly via favorable effects on collagen formation and organization, but had minimal effect on the final outcome of healing. These findings are clinically interesting, as there are few established interventions for ligament injuries, and IACFM is a simple and practical therapy technique. J Orthop Sports Phys Ther 2009;39(7):506-514, Epub 24 February 2009. doi:10.2519/jospt.2009.2997.

Future of Orthopaedic Sports Medicine and Soft Tissue Healing: The Important Role of Engineering

The practice of orthopaedic sports medicine, specifically the management of ligament and tendon injuries, will experience dramatic changes in the near future. Rapid technological advancements, especially in imaging, will greatly increase the speed and accuracy of diagnosing musculoskeletal injuries. On the contrary, effective treatment strategies will lag behind. This widening gap will offer huge opportunities for clinicians, basic scientists, and bioengineers to collaborate and work jointly on in depth basic science and bioengineering research. Together with appropriately designed clinical outcome studies, scientifically based treatment strategies can be designed in order to reduce the gap and to improve patient outcome. In this review, we will focus on the subject of orthopaedic biomechanics and its importance in the treatment of ligament and tendon injuries. We will detail the history of fundamental work done to characterize their biomechanical properties and highlight some recent advances using functional tissue engineering strategies, including the use of bioscaffolds, to improve the healing of medial collateral ligament, patellar tendon, and anterior cruciate ligament. To conclude, we will turn toward the future and highlight a few exciting areas of research as well as emphasize collaborative strategies to solve complex biological and biomechanical problems in ligaments and tendons.

The spatio‐temporal dynamics of ligament healing

Ligament injury commonly occurs with no effective treatment to restore its original state. Numerous studies have examined wound healing after injury, reporting a provisional matrix and scar formation within the wound. Few studies however report the inflammatory, proliferative, and remodeling process during ligament healing in a spatio-temporal manner. Our goal was then to more completely elucidate this process in a rat medial collateral ligament (MCL) healing model. In this study, medial collateral ligaments were surgically transected and allowed to heal. At 1, 3, 5, 7, 9, 11, 14, and 28 days postinjury ligaments were collected and examined with microangiography or immunohistochemistry. We demonstrate that neutrophils and mitotic cells peak between 1 and 5 days postinjury. The majority of factors crest between 5 and 9 days postinjury, including circulating macrophages, resident macrophages, T lymphocytes, hematopoietic cells, vascular endothelial growth factor, and blood vessels. The apoptotic cells predominate from day 9 to the end of the study (day 28). Initially, most assayed markers localize to the epiligament and to granulation tissue at the site of damage. Later, the healing region with its granulation tissue and cells continues to expand into the uninjured tissue. From these results, we have expanded current descriptions of ligament healing and offer a more complete representation of the healing process.

Healing ligament mechanical properties are improved by repair with interpositional allografts but not by concomitant treatment with hyaluronic acid

Healing ligaments have inferior mechanical properties compared to normal ligaments during early healing intervals. The purpose of this study was to investigate if in vivo ligament repair with an interpositional allograft and treatment with hyaluronic acid (HA) would improve the mechanical properties of a medial collateral ligament (MCL) healing from a gap injury. Twenty rabbits were assigned equally to either a donor or recipient group. A gap injury of the MCL was created in both hindlimbs of 10 recipient animals. The right hindlimb was treated with allograft plus HA while the left hindlimb was treated with allograft only. Low-load and high-load mechanical properties, including laxity, relaxation and failure, and histology were evaluated after 6 weeks of healing. Mechanical results were compared to previously published normal MCL and MCL gap scar data. MCL allografts had greater initial force during cyclic relaxation testing and maximum force during failure testing than MCL scars, but were weaker than normal MCLs. Failure stress was the only parameter to demonstrate a statistically significant effect of treatment with HA on the allografts. However, the failure stress of the HA-treated MCL allografts was not different than MCL scars and was less than normal MCLs. In conclusion, interpositional allografts could enhance some mechanical properties of ligament healing but HA, in the way we applied it, did not produce an obvious improvement.

009 Differential Phenotypical Expression of Healing vs. Normal Fibroblasts

Fibroblasts from a healing ligament likely have differential phenotypical expression from those in an intact ligament, because fibroblasts at the healing site need to repair/regenerate the wounded matrix around them caused by injury, whereas normal fibroblasts just maintain an intact matrix. This study was designed to determine the differences in proliferation, collagen production, α-smooth muscle actin (α-SMA) expression, and contraction between healing and normal fibroblasts. Transected and sham-operated rat medial collateral ligaments (MCL) were used to obtain healing and normal fibroblasts, respectively. It was noted that healing and normal MCL fibroblasts in culture were seen to have a similar morphology. However, healing fibroblasts in monolayer culture proliferated 1.4-fold faster at 48 hours and had 1.7-fold greater protein expression of α-SMA than normal fibroblasts. In addition, it was noted that the proliferation of healing fibroblasts in collagen gels was not significantly different from that of normal fibroblasts at 24 hours, but it was at 48 hours. Furthermore, in collagen gels, healing fibroblasts produced 10% more type I collagen than normal fibroblasts and generated 1.6- and 1.7-fold larger contractile forces at 15 and 20 hours, respectively, than their normal counterparts. Taken together, the results of this study show that healing fibroblasts possess a differential proliferation, α-SMA protein expression, and contraction than normal fibroblasts. This study also highlights the importance of using healing fibroblasts to study the cellular and molecular mechanisms of ligament healing. Supported by the NIH grant AR049921 and Whitaker Foundation Grant (JHW)

HGF suppresses the production of collagen type III and α-SMA induced by TGF-β1 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.

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.

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.

Promotion of Medial Collateral Ligament Healing Using a High-Voltage Electrical Field

To assess the biomechanical and histological effects of a high-voltage electrical field on ligament healing. 54 male Wistar rats were used. The medial collateral ligaments (MCLs) of 6 rats were measured for normal biomechanical failure load and stiffness. MCLs of the remaining 48 rats were transected and randomly assigned; half were subjected to a high-voltage electrical field for 8 hours a day (experimental group), and the other half were kept under normal conditions (control group). Eight rats from each group were killed 2, 4, and 6 weeks after the transection and their MCLs were tested biomechanically and histologically. Failure load and stiffness of the MCLs in the experimental group were significantly higher than those in the control group 2 weeks after transection, but not thereafter. At week 2, the granulation tissue completely occupied the space between the cut ends of the MCL in the experimental group, whereas some gaps remained in the control group. A high-voltage electrical field appear to accelerate ligament healing in the initial 2 weeks. Earlier initial healing may allow earlier start of the rehabilitation.