Rat Knee Research Articles

Effects of Bakuchiol on chondrocyte proliferation via the PI3K-Akt and ERK1/2 pathways mediated by the estrogen receptor for promotion of the regeneration of knee articular cartilage defects.

ObjectivesCartilaginous tissue degradation occurs because of the lack of survival of chondrocytes. Here, we ascertained whether bakuchiol (BAK) has the capability of activating chondrocyte proliferation.Materials and methodsThe effect of BAK on the proliferation of rat chondrocytes at a concentration of 10 and 20 µmol/L was investigated. The molecular mechanisms involving target binding and signalling pathways were elucidated by RNA‐sequencing, qPCR, molecular docking and Western blotting. Matrigel mixed with bakuchiol was implanted locally into rat knee articular cartilage defects to verify the activation of chondrocytes due to bakuchiol in vivo.ResultsBakuchiol implantation resulted in the activation of rat chondrocyte proliferation in a dose‐dependent manner. RNA‐sequencing revealed 107 differentially expressed genes (DEGs) with 75 that were up‐regulated and 32 that were down‐regulated, indicating increased activation of the PI3K‐Akt and cell cycle pathways. Activation of the phosphorylation of Akt, ERK1/2 and their inhibitors blocked the proliferative effect of bakuchiol treatment, confirming its direct involvement in these signal transduction pathways. Molecular docking and siRNA silencing revealed that estrogen receptor‐α (ERα) was the target of bakuchiol in terms of its cell proliferative effect via PI3K activation. Two weeks after implantation of bakuchiol, the appearance and physiological structure of the articular cartilage was more integrated with abundant chondrocytes and cartilage matrix compared to that of the control.ConclusionsBakuchiol demonstrated significant bioactivity towards chondrocyte proliferation via the PI3K‐Akt and ERK1/2 pathways mediated by estrogen receptor activation and exhibited enhanced promotion of the remodelling of injured cartilage.

Evaluation iontophoretic delivery of a cationic ketoprofen prodrug for treating nociceptive symptoms in monosodium iodoacetate induced osteoarthritic rat model.

Topical nonsteroidal anti-inflammatory drugs have been used in treatment of osteoarthritis but their efficacy is marginal. One major reason is because of limited drug direct penetration to affected joint and muscle tissues from the topical application. The main purpose of this study was to evaluate a new topical treatment through enhancing the direct drug penetration to local muscle and joint tissues for improving topical treatment of osteoarthritis. A cationic prodrug, ketoprofen choline chloride (KCC) was synthesized for iontophoretic topical delivery. Anodal iontophoretic delivery of KCC and cathodal iontophoretic delivery of ketoprofen to the knee of live hairless rats were evaluated and the drug concentrations in the joint and muscle tissues over the time were determined. In addition, a knee osteoarthritis rat model was induced with intra-articular injection of monosodium iodoacetate solution. Anodal iontophoretic delivery of KCC, cathodal iontophoretic delivery of ketoprofen, or anodal iontophoretic delivery of sodium chloride were applied to the affected knee joint of each rat group, respectively. Knee joint pain was evaluated through a hind paw weight bearing study and knee joint inflammation was evaluated through measuring of the knee diameter. Iontophoretic delivery of KCC showed much higher drug concentration in the knee joint and muscle tissues, compared to iontophoretic delivery of ketoprofen. Treatment of rat knee joint with anodal iontophoresis of KCC also showed significant pain relief and knee inflammation reduction comparing to the control group, while treatment results from cathodal iontophoresis of ketoprofen were mostly not significantly different from the control group.

Monosodium iodoacetate-induced monoarthritis develops differently in knee versus ankle joint in rats

ObjectiveDisability and movement-related pain are major symptoms of joint disease, motivating the development of methods to quantify motor behaviour in rodent joint pain models. We compared effects on behaviour, assessed the levels of biochemical mediators and made a detailed histopathological evaluation after induction of rat monoiodoacetate (MIA) monoarthritis into the ankle or knee joint. DesignTwenty-seven male Lewis rats were used. Before and up to 28 days after induction, they were tested for weight bearing during walking (dynamic), and standing (static), and for mechanical sensitivity. At termination synovial fluid was taken from ankle and/or knee joints for analysis of monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), macrophage inflammatory protein 3 alpha (MIP-3α), keratinocyte chemoattractant (KC)/human growth-regulated oncogene (GRO) and L(+)-lactate, and from separate rats joints were collected for histopathological assessment. ResultsMIA ankle joint injection gave a marked reduction of dynamic weight bearing during the first days, not seen in rats with knee joint injection. At three weeks, it was decreased in the group with knee injection, but not in those with ankle injection. However, the different injection sites caused similar reductions in static weight bearing during the early phase, which was normalized in the group with ankle injection but continued and was strengthened with time in the knee injected group. Histopathological assessment, biochemical mediators and joint swelling confirmed the disparate profiles. ConclusionsThis work shows that ankle versus knee joint injection of MIA resulted in different profiles in rats, which may mirror what has been found in human patients with osteoarthritis.

Accuracy of Ultrasound-Guided versus Landmark-Guided Intra-articular Injection for Rat Knee Joints

Our aim was to test the effectiveness of ultrasound-guided intra-articular (IA) injection into the knee joint of rodents by an inexperienced operator compared with standard landmark-guided IA injections by a trained injector. Fifty landmark-guided and 46 ultrasound-guided IA injections in 49 rats were analyzed. Animal positioning and injection protocol were designed for use with the ultrasound system. Injection delivery was verified with a secondary imaging modality. We compared the success of IA injections by method (landmark and ultrasound-guided), adjusting for all other confounding factors (age, weight, experience, laterality and presence of surgery). Ultrasound-guided injections had higher success rates overall (89% vs. 58%) and helped to reduce the number of failed attempts per injection. None of the cofounding factors influenced the success of injection. In conclusion, we found higher accuracy for ultrasound-guided IA injection delivery than the traditional landmark-based injection method and also the technical feasibility for untrained personnel.

Early Changes in Cement-Bone Fixation Using a Novel Rat Knee Replacement Model.

Trabecular resorption from interdigitated regions between cement and bone has been found in postmortem-retrieved knee replacements, but the viability of interdigitated bone, and the mechanism responsible for this bone loss is not known. In this work, a Sprague-Dawley (age 12 weeks) rat knee replacement model with an interdigitated cement-bone interface was developed. Morphological and cellular changes in the interdigitated region of the knee replacement over time (0, 2, 6, or 12 weeks) were determined for ovariectomy (OVX) and Sham OVX treatment groups. Interdigitated bone volume fraction (BV/TV) increased with time for Sham OVX (0.022 BV/TV/wk) and OVX (0.015 BV/TV/wk) group, but the rate of increase was greater for the Sham OVX group (p = 0.0064). Tissue mineral density followed a similar increase with time in the interdigitated regions. Trabecular resorption, when it did occur, started at the cement border with medullary-adjacent bone in the presence of osteoclasts. There was substantial loss of viable bone (~80% empty osteocyte lacunae) in the interdigitated regions. Pre-surgical fluorochrome labels remained in the interdigitated regions, and did not diminish with time, indicating that the bone was not remodeling. There was also some evidence of continued surface mineralization in the interdigitated region after cementing of the knee, but this diminished over time. Statement of clinical significance: Interdigitated bone with cement provides mechanical stability for success of knee replacements. Improved understanding of the fate of the interdigitated bone over time could lead to a better understanding of the loosening process and interventions to prevent loss of fixation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2163-2171, 2019.

Effects of losartan and atorvastatin on the development of early posttraumatic joint stiffness in a rat model.

BackgroundAfter a trauma, exuberant tissue healing with fibrosis of the joint capsule can lead to posttraumatic joint stiffness (PTJS). Losartan and atorvastatin have both shown their antifibrotic effects in different organ systems.ObjectiveThe purpose of this study was the evaluation of the influence of losartan and atorvastatin on the early development of joint contracture. In addition to joint angles, the change in myofibroblast numbers and the distribution of bone sialoprotein (BSP) were assessed.Study design and methodsIn this randomized and blinded experimental study with 24 rats, losartan and atorvastatin were compared to a placebo. After an initial joint injury, rat knees were immobilized with a Kirschner wire. Rats received either losartan, atorvastatin or a placebo orally daily. After 14 days, joint angle measurements and histological assessments were performed.ResultsLosartan increased the length of the inferior joint capsule. Joint angle and other capsule length measurements did not reveal significant differences between both drugs and the placebo. At cellular level both losartan and atorvastatin reduced the total number of myofibroblasts (losartan: 191±77, atorvastatin: 98±58, placebo: 319±113 per counting field, p<0.01) and the percentage area of myofibroblasts (losartan: 2.8±1.8% [p<0.05], atorvastatin: 2.5±1.7% [p<0.01], vs control [6.4±4%], respectively). BSP was detectable in equivalent amounts in the joint capsules of all groups with only a trend toward a reduction of the BSP-stained area by atorvastatin.ConclusionBoth atorvastatin and losartan reduced the number of myofibroblasts in the posterior knee joint capsule of rat knees 2 weeks after trauma and losartan increased the length of the inferior joint capsule. However, these changes at the cellular level did not translate an increase in range of motion of the rats´ knee joints during early contracture development.

The GLP-1 agonist, liraglutide, ameliorates inflammation through the activation of the PKA/CREB pathway in a rat model of knee osteoarthritis

BackgroundInflammation is a common pathological phenomenon of osteoarthritis (OA). Accumulated evidence indicates that ameliorating or suppressing inflammation might be a promising and effective therapeutic strategy for the treatment of OA. Notably, glucagon-like peptide-1 (GLP-1)-based drugs are being successfully used to control glucose levels in patients with diabetes mellitus. In addition, recent findings have indicated that GLP-1 agonists, such as liraglutide have therapeutic potential in preventing inflammation-related disorders through the regulation of protein kinase A (PKA)/ cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) signals. Intra-articular injection of monoiodoacetate (MIA) has been widely used to induce OA. Thus, the present study aimed to investigate whether liraglutide has anti-inflammatory effects on MIA-induced OA rats and uncover its underlying molecular mechanisms.MethodsIntra-articular injection of MIA was used to induce knee OA in a rat model. Subcutaneous injection of liraglutide was used to upregulate the expression of GLP-1 receptor (GLP-1R). Western blot analysis was utilized to measure the expression of GLP-1R, PKA/CREB pathway components and inflammation-related proteins, such as tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and IL-6. Immunoprecipitation techniques were used to detect the interactions between GLP-1R and the PKA/CREB pathway.ResultsThe levels of GLP-1R decreased significantly in the knees of OA rats, accompanied by the downregulation of PKA /CREB signals and upregulation of inflammation-related proteins. We also found that GLP-1R interacted with the PKA/CREB pathway and that liraglutide could activate PKA/CREB signals, thereby inhibiting the expression of inflammation-related proteins.ConclusionsTogether our results suggest that liraglutide exhibits anti-inflammatory activity through the activation of the PKA/CREB pathway in an OA rat model.

TMF inhibits miR-29a/Wnt/β-catenin signaling through upregulating Foxo3a activity in osteoarthritis chondrocytes.

Background: miR-29a, a downstream factor of Wnt/β-catenin signaling, promotes the activity of the Wnt/β-catenin signaling in a positive feedback loop. Our previous work showed that 5,7,3ʹ,4ʹ-tetramethoxyflavone (TMF), a major constituent from Murraya exotica L., exhibited chondroprotective activity by inhibiting the activity of Wnt/β-catenin signaling.Purpose: To investigate whether TMF showed the inhibitory effects on miR-29a/β-catenin signaling by up regulation of Foxo3a expression.Methods: Rat knee OA models were duplicated by using Hulth’s method. TMF (5 μg/mL and 20 μg/mL) was used for administration to cultured cells, which were isolated from the rat cartilages. Analysis of chondrocytes apoptosis, gene expression, and protein expression were conducted. In addition, miR-29a mimics and pcDNA3.1(+)-Foxo3a vector were used for transfection, luciferase reporter assay for detecting the activity of Wnt/β-catenin signaling, and co-immunoprecipitation for determining proteins interaction.Results: TMF down regulated miR-29a/β-catenin signaling activity and cleaved caspase-3 expression and up regulated Foxo3a expression in OA rat cartilages. In vitro, miR-29a mimics down regulated the expression of Foxo3a and up regulated the activity of Wnt/β-catenin signaling and cleaved caspase-3 expression. TMF ameliorated miR-29a/β-catenin-induced chondrocytes apoptosis by up regulation of Foxo3a expression.Conclusion: TMF exhibited chondroprotective activity by up regulating Foxo3a expression and subsequently inhibiting miR-29a/Wnt/β-catenin signaling activity.

A Mini-Invasive Internal Fixation Technique for Studying Immobilization-Induced Knee Flexion Contracture in Rats.

Joint contracture, resulting from a prolonged joint immobilization, is a common complication in orthopedics. Currently, utilizing an internal fixation to restrict knee joint mobility is a widely accepted model to generate experimental contracture. However, implanting application will inevitably cause surgical trauma to the animals. Aiming to develop a less invasive approach, we combined a muscle-gap separation modus with a previously reported mini-incision skill during the surgical procedure: Two mini skin incisions were made on the lateral thigh and leg, followed by performing muscle-gap separation to expose the bone surface. The rat knee joint was gradually immobilized by a preconstructed internal fixation at approximately 135° knee flexion without interfering essential nerves or blood vessels. As expected, this simple technique permits rapid postoperative rehabilitation in animals. The correct position of the internal fixation was confirmed by an x-ray or micro-CT scanning analysis. The range of motion was significantly restricted in the immobilized knee joint than that observed in the contralateral knee joint demonstrating the effectiveness of this model. Besides, histological analysis revealed the development of fibrous deposition and adhesion in the posterior-superior knee joint capsule over time. Thus, this mini-invasive model may be suitable for mimicking the development of immobilized knee joint contracture.

A Synthetic Bottle-brush Polyelectrolyte Reduces Friction and Wear of Intact and Previously Worn Cartilage.

A poly(7-oxanorbornene-2-carboxylate) polymer containing pendent triethyleneglycol (TEG) chains of 2.8 MDa ("2.8M TEG") was synthesized and evaluated for long-term lubrication and wear reduction of ex vivo bovine cartilage as well as for synovitis in rats and dogs after intra-articular administration. Bovine cartilage surfaces were tested under torsional friction for 10,080 rotations while immersed in either saline, bovine synovial fluid (BSF), or 2.8M TEG. For each solution, coefficient of friction (μ), changes in surface roughness, and lost cartilage glycosaminoglycan were compared. To directly compare 2.8M TEG and BSF, additional samples were tested sequentially in BSF, BSF, 2.8M TEG, and then BSF. Finally, another set of samples were tested twice in saline to induce surface roughness and then tested in BSF, Synvisc, or 2.8M TEG to determine each treatment's effect on worn cartilage. Next, male Lewis rats were injected in one knee with 2.8M TEG or saline and evaluated for effects on gait, and female beagles were injected with either 2.8M TEG or saline in one knee, and their synovial tissues analyzed for inflammation by H&E staining. Treatment with 2.8M TEG lowers μ, lessens surface roughness, and minimizes glycosaminoglycan loss compared to saline. The 2.8M TEG also reduces μ compared to BSF in pairwise testing and on worn cartilage surfaces. Injection of 2.8M TEG in rat or beagle knees gives comparable effects to treatment with saline, and does not cause significant synovitis.

Eccentric training enhances the αB-crystallin binding to the myofibrils and prevents skeletal muscle weakness in adjuvant-induced arthritis rat.

Patients with rheumatoid arthritis (RA) frequently suffer from muscle weakness. We examined whether eccentric training prevents skeletal muscle weakness in adjuvant-induced arthritis (AIA) rat, a widely used animal model for RA. AIA was induced in the knees of Wistar rats by injection of complete Freund's adjuvant. To induce eccentric contractions (ECCs), neuromuscular electrical stimulation (45 V) was applied to the plantar flexor muscles simultaneously with forced dorsiflexion of the ankle joint (0-40°) and was given every 6 s. ECC exercise was applied every other day for a total of 11 sessions and consisted of 4 sets of 5 contractions. There was a significant reduction in in vitro maximum Ca2+-activated force in skinned fibers in gastrocnemius muscle from AIA rats. These changes were associated with reduced expression levels of contractile proteins (i.e., myosin and actin), increased levels of inflammation redox stress-related biomarkers (i.e., TNF-α, malondialdehyde-protein adducts, NADPH oxidase 2, and neuronal nitric oxide synthase), and autolyzed active calpain-1 in AIA muscles. ECC training markedly enhanced the steady-state levels of αB-crystallin, a small heat shock protein, and its binding to the myofibrils and prevented the AIA-induced myofibrillar dysfunction, reduction in contractile proteins, and inflammation-oxidative stress insults. Our findings demonstrate that ECC training preserves myofibrillar function without muscle damage in AIA rats, which is at least partially attributable to the protective effect of αB-crystallin on the myofibrils against oxidative stress-mediated protein degeneration. Thus ECC training can be a safe and effective intervention, counteracting the loss of muscle strength in RA patients. NEW & NOTEWORTHY Eccentric contractions (ECCs) are regarded as an effective way to increase muscle strength. No studies, however, assess safety and effectiveness of ECC training on muscle weakness associated with rheumatoid arthritis. Here, we used adjuvant-induced arthritis (AIA) rats to demonstrate that ECC training prevents intrinsic contractile dysfunction without muscle damage in AIA rats, which may be attributed to the protective effect of αB-crystallin on the myofibrils against inflammation-oxidative stress insults.

Overexpression of chaperonin containing T-complex polypeptide subunit zeta 2 (CCT6b) suppresses the functions of active fibroblasts in a rat model of joint contracture

BackgroundJoint contracture is a fibrous disease characterized as joint capsule fibrosis that results in joint dysfunction and disability. The purpose of this study was to analyze the biological activities of chaperonin containing T-complex polypeptide (CCT) subunits and to determine the role of CCT chaperone in joint contracture in a rat model.MethodsIn this study, the rat model of joint contracture was established by immobilizing the rat knee for 8 weeks. Then, fibroblasts were isolated from the posterior joint capsule and were cultured for functional analysis such as qRT-PCR, Western blot, transwell assay, and collagen assay. The effect of CCT subunit was determined by employing a lentivirus containing target gene and transfecting it into fibroblasts.ResultsResults of qRT-PCR and Western blot showed that among all CCT subunits, CCT6b significantly decreased in the fibroblasts from contractive joints compared to cells from normal joints (p < 0.05). Overexpression of CCT6b by transfection of lentivirus containing CCT6b gene to active fibroblasts significantly inhibited fibrous marker (α-SMA, COL-1) expressions, fibroblast migration, and collagen synthesis (all p < 0.05). Moreover, fibrosis-related chaperone CCT7 expression was decreased with CCT6b overexpression (p < 0.05).ConclusionThe biological activities of CCT subunits in fibroblasts from the joint contracture rat model were analyzed in this study. CCT6b significantly decreased in the active fibroblasts, and overexpression of CCT6b significantly inhibited fibroblast functions. These findings indicate that CCT6b appears to be a potential molecular biomarker and therapeutic target for the novel therapies of joint contracture.

Oral shea nut oil triterpene concentrate supplement ameliorates pain and histological assessment of articular cartilage deterioration in an ACLT injured rat knee osteoarthritis model.

Osteoarthritis (OA) is a multifactorial joint disease and a common disabling condition in the elderly population. The associated pain and pathohistological changes in cartilage are common features of OA in both humans and animal models. Shea nut oil extract (SheaFlex75) contains a high triterpenoid concentration and has demonstrated anti-inflammatory and antiarthritic effects in both human and animal studies. In this study, we aim to investigate the potential of SheaFlex75 to prevent articular cartilage deterioration in a rat model of chronic OA progression. By employing anterior cruciate ligament transection (ACLT) with medial meniscectomy (MMx)-induced OA, we found attenuation of both early and chronic onset OA pain and cartilage degeneration in ACLT+MMx rats receiving SheaFlex75 dietary supplementation. Under long-term oral administration, the rats with induced OA presented sustained protection of both pain and OA cartilage integrity compared to the OA-control rats. Moreover, rats subjected to long-term SheaFlex75 ingestion showed normal biochemical profiles (AST, BUN and total cholesterol) and presented relatively lower triglycerides (TGs) and body weights than the OA-control rats, which suggested the safety of prolonged use of this oil extract. Based on the present evidence, preventive management is advised to delay/prevent onset and progression in OA patients. Therefore, we suggest that SheaFlex75 may be an effective management strategy for symptom relief and cartilage protection in patients with both acute and chronic OA.

Endothelin-1 inhibits size dependent lymphatic clearance of PEG-based conjugates after intra-articular injection into the rat knee

Clearance of particles from the knee is an essential mechanism to maintain healthy joint homeostasis and critical to the delivery of drugs and therapeutics. One of the limitations in developing disease modifying drugs for joint diseases, such as osteoarthritis (OA), has been poor local retention of the drugs. Enhancing drug retention within the joint has been a target of biomaterial development, however, a fundamental understanding of joint clearance pathways has not been characterized. We applied near-infrared (NIR) imaging techniques to assess size-dependent in vivo clearance mechanisms of intra-articular injected, fluorescently-labelled polyethylene glycol (PEG-NIR) conjugates. The clearance of 2 kDa PEG-NIR (τ = 171 ± 11 min) was faster than 40 kDa PEG-NIR (τ = 243 ± 16 min). 40 kDa PEG-NIR signal was found in lumbar lymph node while 2 kDa PEG-NIR signal was not. Thus, these two conjugates may be cleared through different pathways, i.e. lymphatics for 40 kDa PEG-NIR and venous for 2 kDa PEG-NIR. Endothelin-1 (ET-1), a potent vasoconstrictor of vessels, is elevated in synovial fluid of OA patients but, its effects on joint clearance are unknown. Intra-articular injection of ET-1 dose-dependently inhibited the clearance of both 2 kDa and 40 kDa PEG-NIR. ET-1 caused a 1.63 ± 0.17-fold increase in peak fluorescence for 2 kDa PEG-NIR and a 1.85 ± 0.15-fold increase for 40 kDa PEG-NIR; and ET-1 doubled their clearance time constants. The effects of ET-1 were blocked by co-injection of ET receptor antagonists, bosentan or BQ-123. These findings provide fundamental insight into retention and clearance mechanisms that should be considered in the development and delivery of drugs and biomaterial carriers for joint diseases. Statement of SignificanceThis study demonstrates that in vivo knee clearance can be measured using NIR technology and that key factors, such as size of materials and biologics, can be investigated to define joint clearance mechanisms. Therapies targeting regulation of joint clearance may be an approach to treat joint diseases like osteoarthritis. Additionally, in vivo functional assessment of clearance may be used as diagnostics to monitor progression of joint diseases.

Intra-articular levels of five biomarkers assessed via magnetic capture in a rat knee model of osteoarthritis

Intra-articular levels of five biomarkers assessed via magnetic capture in a rat knee model of osteoarthritis

Contribution of sensory nerves within osteochondral channels to pain in human and rat knee osteoarthritis

Contribution of sensory nerves within osteochondral channels to pain in human and rat knee osteoarthritis

Quantifying particle distribution in healthy and osteoarthritic rat knee joints using fluorescent imaging and electron paramagnetic resonance spectroscopy

Quantifying particle distribution in healthy and osteoarthritic rat knee joints using fluorescent imaging and electron paramagnetic resonance spectroscopy

Diffusion tractography of the rat knee at microscopic resolution

Magnetic Resonance in MedicineVolume 81, Issue 6 p. C1-C1 COVER IMAGEFree Access Diffusion tractography of the rat knee at microscopic resolution First published: 26 March 2019 https://doi.org/10.1002/mrm.27760AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume81, Issue6June 2019Pages C1-C1 RelatedInformation

Comparison between Operative and Non-Operative Treatment of the Medial Collateral Ligament: Histological and Ultrastructural Findings during Early Healing in the Epiligament Tissue in a Rat Knee Model

The medial collateral ligament of the knee joint is one of the most commonly injured ligaments of the knee. Recent data have shown that the thin layer of connective tissue covering the ligament, known as the epiligament, is essential for its nutrition and normal function, as well as its healing after injury. The aim of the present study was to investigate and compare the changes in the epiligament of the medial collateral ligament which occurred during operative and non-operative treatment throughout the first month after injury. We used 27 male Wistar rats randomly allocated to three groups. In the 9 rats belonging to the first group, the medial collateral ligament was fully transected and left to heal spontaneously without suture. In the 9 rats belonging to the second group, the transected ends were marked with a 9–0 nylon monofilament suture. The 9 rats in the third group were used as normal controls. Three animals from each group were sacrificed on days 8, 16, and 30 after injury. Light microscopic analysis was performed on semi-thin sections stained with 1% methylene blue, azure II, and basic fuchsin. Transmission electron microscopy was used to study and compare the ultrastructural changes in the epiligament. The statistical analysis of the obtained data was performed using the Kruskal-Wallis H test and Mood’s median test. The normal structure of the epiligament of the medial collateral ligament was presented by fibroblasts, fibrocytes, adipose cells, mast cells, collagen fibers, and neuro-vascular bundles. On days 8 and 16 postinjury, the epiligament appeared hypercellular and returned to its normal appearance on the thirtieth day postinjury. The electron microscopic study revealed the presence of different types of fibroblasts with the typical ultrastructural features of collagen-synthetizing cells. The comparative statistical analysis on the respective day showed that there was no statistically significant difference in the number of cells between spontaneously healing animals and animals recovering with suture application. These data further prove that spontaneous healing of the medial collateral ligament yields similar results to surgical treatment and may be used as a basis for the development of treatment regimens with improved patient outcome.

Correction: Epiligament Tissue of the Medial Collateral Ligament in Rat Knee Joint: Ultrastructural Study.

[This corrects the article DOI: 10.7759/cureus.3812.].