Identification of transcription factors responsible for dysregulated networks in human osteoarthritis cartilage by global gene expression analysis.

OBJECTIVE: Osteoarthritis (OA) is the most prevalent joint disease. As disease-modifying therapies are not available, novel therapeutic targets need to be discovered and prioritized for their importance in mediating the abnormal phenotype of cells in OA-affected joints. Here, we generated a genome-wide molecular profile of OA to elucidate regulatory mechanisms of OA pathogenesis and to identify possible therapeutic targets using integrative analysis of mRNA-sequencing data obtained from human knee cartilage. DESIGN: RNA-sequencing (RNA-seq) was performed on 18 normal and 20 OA human knee cartilage tissues. RNA-seq datasets were analysed to identify genes, pathways and regulatory networks that were dysregulated in OA. RESULTS: RNA-seq data analysis revealed 1332 differentially expressed (DE) genes between OA and non-OA samples, including known and novel transcription factors (TFs). Pathway analysis identified 15 significantly perturbed pathways in OA with ECM-related, PI3K-Akt, HIF-1, FoxO and circadian rhythm pathways being the most significantly dysregulated. We selected DE TFs that are enriched for regulating DE genes in OA and prioritized these TFs by creating a cartilage-specific interaction subnetwork. This analysis revealed eight TFs, including JUN, Early growth response (EGR)1, JUND, FOSL2, MYC, KLF4, RELA, and FOS that both target large numbers of dysregulated genes in OA and are themselves suppressed in OA. CONCLUSIONS: We identified a novel subnetwork of dysregulated TFs that represent new mediators of abnormal gene expression and promising therapeutic targets in OA.

Neuromuscular adaptations induced by adjacent joint training.

Effects of resistance training are well known to be specific to tasks that are involved during training. However, it remains unclear whether neuromuscular adaptations are induced after adjacent joint training. This study examined the effects of hip flexion training on maximal and explosive knee extension strength and neuromuscular performance of the rectus femoris (RF, hip flexor, and knee extensor) compared with the effects of knee extension training. Thirty-seven untrained young men were randomly assigned to hip flexion training, knee extension training, or a control group. Participants in the training groups completed 4 weeks of isometric hip flexion or knee extension training. Standardized differences in the mean change between the training groups and control group were interpreted as an effect size, and the substantial effect was assumed to be ≥0.20 of the between-participant standard deviation at baseline. Both types of training resulted in substantial increases in maximal (hip flexion training group: 6.2% ± 10.1%, effect size = 0.25; knee extension training group: 20.8% ± 9.9%, effect size = 1.11) and explosive isometric knee extension torques and muscle thickness of the RF in the proximal and distal regions. Improvements in strength were accompanied by substantial enhancements in voluntary activation, which was determined using the twitch interpolation technique and RF activation. Differences in training effects on explosive torques and neural variables between the two training groups were trivial. Our findings indicate that hip flexion training results in substantial neuromuscular adaptations during knee extensions similar to those induced by knee extension training.

Dysregulated circadian rhythm pathway in human osteoarthritis: NR1D1 and BMAL1 suppression alters TGF-ß signaling in chondrocytes.

OBJECTIVES: Circadian rhythm (CR) was identified by RNA sequencing as the most dysregulated pathway in human osteoarthritis (OA) in articular cartilage. This study examined circadian rhythmicity in cultured chondrocytes and the role of the CR genes NR1D1 and BMAL1 in regulating chondrocyte functions. METHODS: RNA was extracted from normal and OA-affected human knee cartilage (n = 14 each). Expression levels of NR1D1 and BMAL1 mRNA and protein were assessed by quantitative PCR and immunohistochemistry. Human chondrocytes were synchronized and harvested at regular intervals to examine circadian rhythmicity in RNA and protein expression. Chondrocytes were treated with small interfering RNA (siRNA) for NR1D1 or BMAL1, followed by RNA sequencing and analysis of the effects on the transforming growth factor beta (TGF-ß) pathway. RESULTS: NR1D1 and BMAL1 mRNA and protein levels were significantly reduced in OA compared to normal cartilage. In cultured human chondrocytes, a clear circadian rhythmicity was observed for NR1D1 and BMAL1. Increased BMAL1 expression was observed after knocking down NR1D1, and decreased NR1D1 levels were observed after knocking down BMAL1. Sequencing of RNA from chondrocytes treated with NR1D1 or BMAL1 siRNA identified 330 and 68 significantly different genes, respectively, and this predominantly affected the TGF-ß signaling pathway. CONCLUSIONS: The CR pathway is dysregulated in OA cartilage. Interference with circadian rhythmicity in cultured chondrocytes affects TGF-ß signaling, which is a central pathway in cartilage homeostasis.

Suppression of REDD1 in osteoarthritis cartilage, a novel mechanism for dysregulated mTOR signaling and defective autophagy.

OBJECTIVE: Aging is a main risk factor for the development of osteoarthritis (OA) and the molecular mechanisms underlying the aging-related changes in articular cartilage include increased mammalian target of rapamycin (mTOR) signaling and defective autophagy. REDD1 is an endogenous inhibitor of mTOR that regulates cellular stress responses. In this study we measured REDD1 expression in normal, aged and OA cartilage and assessed REDD1 function in human and mouse articular chondrocytes. METHODS: REDD1 expression was analyzed in human and mouse articular cartilage by qPCR, western blotting, and immunohistochemistry. For functional studies, REDD1 and TXNIP knockdown or overexpression was performed in chondrocytes in the presence or absence of rapamycin and chloroquine, and mTOR signaling and autophagy were measured by western blotting. REDD1/TXNIP protein interaction was assessed by co-immunoprecipitation experiments. RESULTS: Human and mouse cartilage from normal knee joints expressed high levels of REDD1. REDD1 expression was significantly reduced in aged and OA cartilage. In cultured chondrocytes, REDD1 knockdown increased whereas REDD1 overexpression decreased mTOR signaling. In addition, REDD1 activated autophagy by an mTOR independent mechanism that involved protein/protein interaction with TXNIP. The REDD1/TXNIP complex was required for autophagy activation in chondrocytes. CONCLUSION: The present study shows that REDD1 is highly expressed in normal human articular cartilage and reduced during aging and OA. REDD1 in human chondrocytes negatively regulates mTOR activity and is essential for autophagy activation. Reduced REDD1 expression thus represents a novel mechanism for the increased mTOR activation and defective autophagy observed in OA.

Effects of 4 Weeks of Explosive-type Strength Training for the Plantar Flexors on the Rate of Torque Development and Postural Stability in Elderly Individuals.

This study aimed to investigate the effect of a 4-week explosive-type strength training program for the plantar flexors on the rate of torque development and postural stability. The participants were 56 elderly men and women divided into training (17 men and 15 women) and control (14 men and 10 women) groups. The participants in the training group underwent explosive-type strength training of the plantar flexors 2 days per week for 4 weeks. Training consisted of 3 sets of 10 repetitions of explosive plantar flexion lasting less than 1 s. The following parameters were determined: muscle volume of the plantar flexors estimated by the muscle thickness and lower leg length, maximal voluntary contraction torque and rate of torque development of plantar flexion, and one-leg standing ability. The training increased the maximal voluntary contraction torque and rate of torque development, but corresponding increases in muscle volume and one-leg standing ability were not found. These results suggest that, for elderly individuals, the 4-week explosive-type strength training of the plantar flexors is effective for increasing the maximal voluntary contraction torque and rate of torque development of plantar flexion but is not effective for improving postural stability.

Utility of T2 mapping and dGEMRIC for evaluation of cartilage repair after allograft chondrocyte implantation in a rabbit model.

OBJECTIVE: To investigate the effectiveness of quantitative Magnetic resonance imaging (MRI) for evaluating the quality of cartilage repair over time following allograft chondrocyte implantation using a three-dimensional scaffold for osteochondral lesions. DESIGN: Thirty knees from 15 rabbits were analyzed. An osteochondral defect (diameter, 4 mm; depth, 1 mm) was created on the patellar groove of the femur in both legs. The defects were filled with a chondrocyte-seeded scaffold in the right knee and an empty scaffold in the left knee. Five rabbits each were euthanized at 4, 8, and 12 weeks and their knees were examined via macroscopic inspection, histological and biochemical analysis, and quantitative MRI (T2 mapping and dGEMRIC) to assess the state of tissue repair following allograft chondrocyte implantation with a three-dimensional scaffold for osteochondral lesions. RESULTS: Comparatively good regenerative cartilage was observed both macroscopically and histologically. In both chondrocyte-seeded and control knees, the T2 values of repair tissues were highest at 4 weeks and showed a tendency to decrease with time. ΔR1 values of dGEMRIC also tended to decrease with time in both groups, and the mean ΔR1 was significantly lower in the CS-scaffold group than in the control group at all time points. ΔR1 = 1/r (R1post - R1pre), where r is the relaxivity of Gd-DTPA(2-), R1 = 1/T1 (longitudinal relaxation time). CONCLUSION: T2 mapping and dGEMRIC were both effective for evaluating tissue repair after allograft chondrocyte implantation. ΔR1 values of dGEMRIC represented good correlation with histologically and biochemically even at early stages after the implantation.

Hidden osteophyte formation on plain X-ray is the predictive factor for development of knee osteoarthritis after 48 months--data from the Osteoarthritis Initiative.

OBJECTIVE: To examine whether the detection of osteophytes anywhere in the knee could serve as a pre-radiographic biomarker for osteoarthritis (OA) development. METHODS: Baseline magnetic resonance imaging (MRIs) of 132 participants in the Osteoarthritis Initiative (OAI) were studied. Based on radiographs, 66 knees were assessed as osteoarthritis-free (no-osteoarthritis [NOA], or Kellgren/Lawrence [K/L] severity grade 0/1 both at baseline and 48 months), and another 66 knees were assessed as having radiographic OA changes (pre-radiographic osteoarthritis [PROA], or with K/L grade 0/1 at baseline and grade ≥ 2 at 48 months). Using baseline MRI data, we examined eight sites of osteophyte formation: the medial and lateral femoral condyle (MFC and LFC, respectively); medial and lateral tibial plateau (MTP and LTP, respectively); medial and lateral facets of the patellofemoral joint (PM and PL, respectively); tibial spine (TS); and femoral intercondylar notch (IC). Knee joint osteophyte size was assessed via the 8-point marginal osteophytes item of the whole-organ magnetic resonance imaging score (WORMS). The frequencies and distributions of osteophytes were compared between groups. RESULTS: Mild-size osteophytes (defined as score ≥ 2) were observed more frequently at the MFC (P = 0.00278), MTP (P = 0.0046), TS (P = 0.0146), PM (P < 0.0001), PL (P = 0.0012), and IC (P < 0.0001) in PROA knees than in NOA knees. Moderate-size osteophytes (defined as score ≥ 4) were more frequently observed in PROA knees than in NOA knees only at the IC (P < 0.0001). CONCLUSION: Knees with osteophyte formation at the IC, even those of K/L severity grade 0/1, are at risk for the development of radiographic OA by 48 months.

Preventive effects of hyaluronan from deterioration of gait parameters in surgically induced mice osteoarthritic knee model.

OBJECTIVE: Osteoarthritis (OA) leads to pain and loss of function in affected joints. Gait disturbance results from these symptoms of OA, and gait analysis can be important to evaluate the progression of OA. The purpose of this study was to analyze gait pattern in a rodent model of OA and to assess the effects of intra-articular injection of hyaluronan (IAI-HA) by gait analysis, along with histological evaluation. DESIGN: OA was induced by destabilization of the medial meniscus (DMM) of C57BL/6 mice. IAI-HA started 3 weeks after DMM surgery. Mice were allocated to three groups and were given either 800-kDa HA (800-HA), 6000-kDa HA (6000-HA) or saline. We compared these three groups with a sham group by gait analysis using CatWalk. Histological evaluation was performed to assess articular cartilage changes in the knee joints. RESULTS: Mice injected with 800-HA or 6000-HA showed gait patterns similar to that of the sham mice, while the saline-injected group showed gait disturbances 12 and 16 weeks after DMM surgery. Histological changes in articular cartilage were similar among the 800-HA, 6000-HA and saline-treated groups, demonstrating OA progression throughout the experimental time points. Positive gait-related effects of IAI-HA might occur by its pain relieving effect and/or by preventing contracture. CONCLUSION: IAI-HA prevented gait disturbances in the DMM model, but did not prevent histological changes associated with OA progression.

Effect of a 5-week static stretching program on hardness of the gastrocnemius muscle.

This study investigated the effects of a static stretching (SS) program on muscle hardnesses of the gastrocnemius medialis (MG) and gastrocnemius lateralis (LG). Nineteen young men participated in this study. Either the right or left leg was randomly selected to conduct three bouts of 2-min SS of the plantar flexors 6 days a week for 5 weeks in each subject (the SS group), and the other leg was assigned to a control group. Before (pretest) and after (posttest) conducting the SS program, MG and LG hardnesses were measured using shear wave ultrasound elastography. The SS program was found to decrease muscle hardnesses, but not to change the ratio of MG hardness to LG hardness. There were no significant differences between the relative changes in the MG and LG hardnesses from pretest to posttest in both the SS and control groups. Significant correlations between the muscle hardness ratios at pretest and posttest were found in both groups. The results of this study suggest that the current SS program is useful for improving muscle condition in the plantar flexors, and that its long-term effects on the MG and LG hardnesses are of the same degree.

Sex difference in strength and size ratios between reciprocal muscle groups in the lower leg.

This study compared strength and size of reciprocal muscle groups in the lower leg between sexes. 20 young men and 14 young women volunteered as subjects. Joint torques developed during isometric maximal voluntary plantar flexion (TQPF) and dorsiflexion (TQDF) were measured using a dynamometer. Muscle volumes of plantar flexors (MVPF) and dorsiflexors (MVDF) were determined by magnetic resonance imaging. In each of the muscle groups, joint torque was significantly correlated with muscle volume in young men and women (r=0.610-0.848) and the y-intercept of the regression line between them was not significantly different from zero. Based on these observations, the dependencies of muscle strength ratio on muscle size ratio between the plantar flexors and dorsiflexors were investigated using joint torque and muscle volume. The correlations between the MVPF per MVDF and the TQPF per TQDF were significant both in young men (r=0.608) and women (r=0.773), suggesting that strength ratio is strongly affected by size ratio between the plantar flexors and dorsiflexors in young men and women.

Calculation of force and power during bench throws using a Smith machine: the importance of considering the effect of counterweights.

For achieving accurate and safe measurements of the force and power exerted on a load during resistance exercise, the Smith machine has been used instead of free weights. However, because some Smith machines possess counterweights, the equation for the calculation of force and power in this system should be different from the one used for free weights. The purpose of this investigation was to calculate force and power using an equation derived from a dynamic equation for a Smith machine with counterweights and to determine the differences in force and power calculated using 2 different equations. One equation was established ignoring the effect of the counterweights (Method 1). The other equation was derived from a dynamic equation for a barbell and counterweight system (Method 2). 9 female collegiate judo athletes performed bench throws using a Smith machine with a counterweight at 6 different loading conditions. Barbell displacement was recorded using a linear position transducer. The force and power were subsequently calculated by Methods 1 and 2. The results showed that the mean and peak power and force in Method 1 were significantly lower relative to those of Method 2 under all loading conditions. These results indicate that the mean and peak power and force during bench throwing using a Smith machine with counterweights would be underestimated when the calculations used to determine these parameters do not account for the effect of counterweights.

Angiogenic activity of subchondral bone during the progression of osteoarthritis in a rabbit anterior cruciate ligament transection model.

OBJECTIVE: To investigate the longitudinal angiogenic activity of subchondral bone and cartilage during the progression of osteoarthritis (OA) using a rabbit model of OA. MATERIALS AND METHODS: OA was surgically induced by anterior cruciate ligament transaction (ACLT) in left knee of 12 months old female New Zealand white rabbits (n = 33). Histological examination, immunohistochemistry, and angiogenic activity assay was done at 0, 2, 4, 6, 8, 12 weeks after ACLT. Histologic evaluation was performed with haematoxylin and eosin, safranin-O staining to assess the OA change of medial femoral condyle (MFC) and lateral femoral condyle (LFC). CD31 immunohistochemistry was performed to confirm the vascular invasion at osteochondral junction. A co-cultured tubule formation assay was conducted to evaluate angiogenic activity of the subchondral bone and cartilage of MFC and LFC as well as synovium. Association between histological changes, angiogenic activity, and vascular invasion were evaluated. RESULTS: OA changes increased in a time-dependent manner both in MFC and LFC. Angiogenic activity of subchondral bone showed a monomodal change during the OA progression, achieved a peak in the early to progressive stage and decreased to normal level in the late stage of OA. Surge of vascular invasion was observed following the increase of angiogenic activity in the progressive stage of OA. Angiogenic activity of cartilage did not change during the course of OA progression. CONCLUSION: Angiogenic activity of subchondral bone was elevated in the early to progressive stage of OA and vascular invasion into the osteochondral junction followed.

Muscle strength and size balances between reciprocal muscle groups in the thigh and lower leg for young men.

The present study investigated whether the muscle size balance affects the muscle strength balance between reciprocal muscle groups in the thigh and lower leg. 18 young men volunteered as subjects. The joint torques developed during isometric maximal voluntary knee extension and flexion, plantar flexion and dorsiflexion were measured using a dynamometer. The muscle volumes of knee extensors and flexors, plantar flexors and dorsiflexors were determined by magnetic resonance imaging. For each of the muscle groups, the joint torque was significantly correlated with the muscle volume (r=0.644-0.847) and the y-intercept of the regression line between them was not significantly different from zero. Based on these observations, the dependencies of muscle strength balance on muscle size balance between the knee extensors and flexors and between the plantar flexors and dorsiflexors were investigated using the joint torque and muscle volume. The correlation between muscle volume ratio and joint torque ratio was significant between the plantar flexors and dorsiflexors (r=0.622) but not between the knee extensors and flexors (r=0.128). Thus, it is suggested that the strength balance is strongly affected by the size balance between the reciprocal muscle groups in the lower leg but not in the thigh.

Hemin treatment abrogates monocrotaline-induced pulmonary hypertension.

Treatment of rats with monocrotaline (MCT), a pyrrolizidine alkaloid plant toxin, is known to cause pulmonary hypertension (PH), and it has been used as a useful experimental model of PH. Recent findings suggested that pulmonary inflammation may play a significant role in the pathogenesis of MCT-induced PH. We also demonstrated that, following MCT administration to rats, there was a significant and sustained increase in the pulmonary expression of heme oxygenase-1 (HO-1), which is known to be induced by various oxidative stresses, including inflammation and free heme, and is thought to be essential in the protection against oxidative tissue injuries. In this study, we administered hemin (ferriprotoporphyrin chloride, 30 micromol/kg b.w., subcutaneously), a potent inducer of HO-1, every 3 days to rats following subcutaneous administration of MCT (60 mg/kg) and examined its effect on MCT-induced PH and pulmonary inflammation. MCT administration caused pulmonary arterial wall thickening with marked elevation of right ventricular pressure, in association with prominent pulmonary inflammation as revealed by the increase in gene expression of tumor necrosis factor-alpha and the number of infiltrated neutrophils in the lung. In contrast, hemin treatment of MCT-administered animals, which led to a further increase in pulmonary HO-1 mRNA expression, significantly ameliorated MCT-induced PH as well as tissue inflammation. These findings suggest that hemin treatment ameliorates MCT-induced PH possibly mediated through induction of pulmonary HO-1 which leads to the attenuation of pulmonary inflammation.

The effect of femoral bone tunnel configuration on tendon-bone healing in an anterior cruciate ligament reconstruction: An animal study.

OBJECTIVES: To compare the effect of femoral bone tunnel configuration on tendon-bone healing in an anterior cruciate ligament (ACL) reconstruction animal model. METHODS: Anterior cruciate ligament reconstruction using the plantaris tendon as graft material was performed on both knees of 24 rabbits (48 knees) to mimic ACL reconstruction by two different suspensory fixation devices for graft fixation. For the adjustable fixation device model (Socket group; group S), a 5 mm deep socket was created in the lateral femoral condyle (LFC) of the right knee. For the fixed-loop model (Tunnel group; group T), a femoral tunnel penetrating the LFC was created in the left knee. Animals were sacrificed at four and eight weeks after surgery for histological evaluation and biomechanical testing. RESULTS: Histologically, both groups showed a mixture of direct and indirect healing patterns at four weeks, whereas only indirect healing patterns were observed in both groups at eight weeks. No significant histological differences were seen between the two groups at four and eight weeks in the roof zone (four weeks, S: mean 4.8 sd 1.7, T: mean 4.5 sd 0.5, p = 0.14; eight weeks, S: mean 5.8 sd 0.8, T: mean 4.8 sd 1.8, p = 0.88, Mann-Whitney U test) or side zone (four weeks, S: mean 5.0 sd 1.2, T: mean 4.8 sd 0.4, p = 0.43; eight weeks, S: mean 5.3 sd 0.8,T: mean 5.5 sd 0.8, p = 0.61, Mann-Whitney U test) . Similarly, no significant difference was seen in the maximum failure load between group S and group T at four (15.6 sd 9.0N and 13.1 sd 5.6N) or eight weeks (12.6 sd 3.6N and 17.1 sd 6.4N, respectively). CONCLUSION: Regardless of bone tunnel configuration, tendon-bone healing after ACL reconstruction primarily occurred through indirect healing. No significant histological or mechanical differences were observed between adjustable and fixed-loop femoral cortical suspension methods.Cite this article: Y. Sato, R. Akagi, Y. Akatsu, Y. Matsuura, S. Takahashi, S. Yamaguchi, T. Enomoto, R. Nakagawa, H. Hoshi, T. Sasaki, S. Kimura, Y. Ogawa, A. Sadamasu, S. Ohtori, T. Sasho. The effect of femoral bone tunnel configuration on tendon-bone healing in an anterior cruciate ligament reconstruction: An animal study. Bone Joint Res 2018;7:327-335. DOI: 10.1302/2046-3758.75.BJR-2017-0238.R2.

Heme oxygenase-1: a fundamental guardian against oxidative tissue injuries in acute inflammation.

Free heme contributes as a major threat to the oxidative tissue injuries because it catalyzes the formation of reactive oxygen species. When free heme concentration is increased, it results in the induction of heme oxygenase-1 (HO-1), which then breaks free heme down. As such, HO-1 plays a pivotal role in the protection of tissues from oxidative injuries.

Exhaled carbon monoxide concentration is not elevated in patients with inflammatory bowel disease.

The present study was initiated to examine whether the concentration of CO in the breath is elevated in patients with inflammatory bowel disease (IBD). Twenty-three clinically stable patients with IBD in the outpatient clinic (11 with Crohn's disease, 12 with ulcerative colitis), who are non-smokers and non-passive smokers, were selected and the concentration of CO in their breath was measured using a breath gas analyser (TRI lyser mBA-3000). The concentration of CO in the breath of 23 patients with IBD was 2.5+/-0.9 (1.1-4.3) ppm. This concentration comes within the range of standard values in our previous reports (2.5+/-2.2 ppm). Any significant difference was not observed between 2.4+/-0.9 (1.5-4.3) ppm for the 11 Crohn's disease patients and the 2.6+/-1.0 (1.1-3.9) ppm for the 12 ulcerative colitis patients. The results suggest that clinically stable patients with IBD do not show high values for concentration of CO in the breath.

The recognition and incidence of peroneal tendon dislocation associated with a fracture of the talus.

AIMS: The purposes of this study were to clarify first, the incidence of peroneal tendon dislocation in patients with a fracture of the talus and second the factors associated with peroneal tendon dislocation. PATIENTS AND METHODS: We retrospectively examined 30 patients (30 ankles) with a mean age of 37.5 years, who had undergone internal fixation for a fracture of the talus. Independent examiners assessed for peroneal tendon dislocation using the pre-operative CT images. The medical records were also reviewed for the presence of peroneal tendon dislocation. The associations between the presence of dislocation with the patient characteristics or radiological findings, including age, mechanism of injury, severity of fracture, and fleck sign, were assessed using Fisher's exact tests. RESULTS: The pre-operative CT images showed peroneal tendon dislocation in eight out of 30 patients. Dislocation was found later in one patient whose pre-operative CT image had not shown dislocation. The overall incidence of peroneal tendon dislocation was 30% (9/30). The presence of dislocation was associated with the presence of a fleck sign (p = 0.03). CONCLUSIONS: Surprisingly, approximately one-third of the patients who underwent internal fixation for a fracture of the talus had peroneal tendon dislocation. This was associated with a fleck sign. Cite this article: Bone Joint J 2017;99-B:489-93.

The effect of systemic administration of G-CSF on a full-thickness cartilage defect in a rabbit model MSC proliferation as presumed mechanism: G-CSF for cartilage repair.

OBJECTIVES: The aim of this study was to investigate the effect of granulocyte-colony stimulating factor (G-CSF) on mesenchymal stem cell (MSC) proliferation in vitro and to determine whether pre-microfracture systemic administration of G-CSF (a bone marrow stimulant) could improve the quality of repaired tissue of a full-thickness cartilage defect in a rabbit model. METHODS: MSCs from rabbits were cultured in a control medium and medium with G-CSF (low-dose: 4 µg, high-dose: 40 µg). At one, three, and five days after culturing, cells were counted. Differential potential of cultured cells were examined by stimulating them with a osteogenic, adipogenic and chondrogenic medium.A total of 30 rabbits were divided into three groups. The low-dose group (n = 10) received 10 µg/kg of G-CSF daily, the high-dose group (n = 10) received 50 µg/kg daily by subcutaneous injection for three days prior to creating cartilage defects. The control group (n = 10) was administered saline for three days. At 48 hours after the first injection, a 5.2 mm diameter cylindrical osteochondral defect was created in the femoral trochlea. At four and 12 weeks post-operatively, repaired tissue was evaluated macroscopically and microscopically. RESULTS: The cell count in the low-dose G-CSF medium was significantly higher than that in the control medium. The differentiation potential of MSCs was preserved after culturing them with G-CSF.Macroscopically, defects were filled and surfaces were smoother in the G-CSF groups than in the control group at four weeks. At 12 weeks, the quality of repaired cartilage improved further, and defects were almost completely filled in all groups. Microscopically, at four weeks, defects were partially filled with hyaline-like cartilage in the G-CSF groups. At 12 weeks, defects were repaired with hyaline-like cartilage in all groups. CONCLUSIONS: G-CSF promoted proliferation of MSCs in vitro. The systemic administration of G-CSF promoted the repair of damaged cartilage possibly through increasing the number of MSCs in a rabbit model.Cite this article: T. Sasaki, R. Akagi, Y. Akatsu, T. Fukawa, H. Hoshi, Y. Yamamoto, T. Enomoto, Y. Sato, R. Nakagawa, K. Takahashi, S. Yamaguchi, T. Sasho. The effect of systemic administration of G-CSF on a full-thickness cartilage defect in a rabbit model MSC proliferation as presumed mechanism: G-CSF for cartilage repair. Bone Joint Res 2017;6:123-131. DOI: 10.1302/2046-3758.63.BJR-2016-0083.

Associations of three-dimensional T1 rho MR mapping and three-dimensional T2 mapping with macroscopic and histologic grading as a biomarker for early articular degeneration of knee cartilage.

T1 rho and T2 mapping are magnetic resonance imaging (MRI) techniques to detect early degenerative changes in cartilage. Recent advancements have enabled 3D acquisition for both techniques. The objective of the present study was to examine the correlation of 3D T1 rho and 3D T2 mapping with macroscopic and histological characteristics of knee cartilage. Twenty-one patients who underwent total knee arthroplasty due to osteoarthritis with involvement of the medial compartment but with minimum involvement of the lateral compartment were enrolled. Prior to surgery, five series of MRI were acquired with a 3-T scanner. 3D T1 rho/T2 analyses were performed following determination of regions to be assessed using in-house software that incorporated three series of MRI acquisitions data (3D-MERGE, 3D-SPGR, and 3D-CUBE). During surgery, the cartilage of the lateral compartment was macroscopically assessed with the International Cartilage Research Society (ICRS) articular classification system. The extracted specimens were histologically assessed using the OARSI histology score. Three regions of interest (ROI) were assessed for each slice (two slices per knee): the central lateral femoral condyle (cLFC), the posterior portion of the lateral femoral condyle (pLFC), and the lateral tibia plateau (LTP). For each ROI, the mean T1 rho and T2 relaxation time, the ICRS grade, and the OARSI score were compared. Neither the T1 rho nor the T2 reflected the macroscopic grading. The T1 rho could discriminate between histological grades 1 and 2. However, the T2 could not. The T1 rho relaxation time was higher in the pLFC than in the cLFC even in the same grade. Compared to T2 mapping, T1 rho mapping may have an advantage in differentiating grades I and II cartilage degeneration on OARSI histological grading system.