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Exposure of articular cartilage to excessive mechanical loading is deeply involved in the pathogenesis of osteoarthritis. Here, we identify gremlin-1 as a mechanical loading-inducible factor in chondrocytes, detected at high levels in middle and deep layers of cartilage after cyclic strain or hydrostatic pressure loading. Gremlin-1 activates nuclear factor-κB signalling, leading to subsequent induction of catabolic enzymes. In mice intra-articular administration of gremlin-1 antibody or chondrocyte-specific deletion of Gremlin-1 decelerates osteoarthritis development, while intra-articular administration of recombinant gremlin-1 exacerbates this process. Furthermore, ras-related C3 botulinum toxin substrate 1 activation induced by mechanical loading enhances reactive oxygen species (ROS) production. Amongst ROS-activating transcription factors, RelA/p65 induces Gremlin-1 transcription, which antagonizes induction of anabolic genes such as Sox9 , Col2a1 , and Acan by bone morphogenetic proteins. Thus, gremlin-1 plays essential roles in cartilage degeneration by excessive mechanical loading. Excessive mechanical stress promotes the development of osteoarthritis. Here Chang et al. identify gremlin-1 as a factor expressed in chondrocytes in response to mechanical stress, and contributing to osteoarthritis via activation of the NF-κB pathway.

Titanium oxide materials have multiple functions such as photocatalytic and photovoltaic effects. Ferroelectrics provide access to light energy conversion that delivers above-bandgap voltages arising from spatial inversion symmetry breaking, whereas their wide bandgap leads to poor absorption of visible light. Bandgap narrowing offers a potential solution, but this material modification suppresses spontaneous polarization and, hence, sacrifices photovoltages. Here, we report successive-redox mediated ferrophotovoltaics that exhibit a robust visible-light response. Our single-crystal experiments and ab initio calculations, along with photo-luminescence analysis, demonstrate that divalent Fe 2+ and trivalent Fe 3+ coexisted in a prototypical ferroelectric barium titanate BaTiO 3 introduce donor and acceptor levels, respectively, and that two sequential Fe 3+ /Fe 2+ redox reactions enhance the photogenerated power not only under visible light but also at photon energies greater than the bandgap. Our approach opens a promising route to the visible-light activation of photovoltaics and, potentially, of photocatalysts. Photovoltaic response from normal ferroelectric materials generates large voltages but low current due to poor absorption of visible light. Noguchi et al. dope ferrous and ferric ion couple into barium titanate crystals to enhance the photogeneration at photon energies both below and above bandgap.

Intervertebral disc degeneration (IDD) is the main contributor to low back pain, which is a leading cause of disability worldwide. Although substantial progress has been made in elucidating the molecular mechanisms of IDD, fundamental and long‐lasting treatments for IDD are still lacking. With increased understanding of the complex pathomechanism of IDD, alternative strategies for treating IDD can be discovered. A brief overview of the prevalence and epidemiologic risk factors of IDD is provided in this review, followed by the descriptions of anatomic, cellular, and molecular structure of the intervertebral disc as well as the molecular pathophysiology of IDD. Finally, the recent findings of intervertebral disc progenitors are reviewed and the future perspectives are discussed. Pathomechanism of intervertebral disc degeneration. Several risk factors including genetic factors as well as mechanical stress, trauma and smoking, attributed to the development of intervertebral disc degeneration. These biological and environmental factors induce the reduction of cell numbers and transformation of intervertebral disc cells through several molecular mechanisms, resulting in decreased production of extracellular matrix due to increased catabolic activity and decreased anabolic activities. Thereafter, the structured integrity of intervertebral disc is lost and intervertebral disc degeneration is further accelerated.

PurposeMinimum clinically important difference (MCID) represents the smallest change in an outcome measure recognized as clinically meaningful to a patient and is one of the most important psychometric parameters for assessing the postoperative results of spinal surgery. The purpose of the present study was to elucidate MCIDs for four common outcome measures used for degenerative cervical myelopathy in the context of patients undergoing laminoplasty.MethodsWe retrospectively reviewed a consecutive series of cervical laminoplasties in a single academic institution. Pre- and postoperative Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), Short Form-36 (SF-36), Neck Disability Index (NDI), and EuroQOL (EQ-5D) scores were obtained. Patients were also asked to answer the anchor question regarding satisfaction with treatment, and the anchor-based method was used to determine cut-off values for MCIDs.ResultsA total of 101 patients were included in the analysis. All outcome scores showed significant improvement postoperatively, with the exception of JOACMEQ bladder function score and SF-36 mental component summary score. Most patients (66%) were at least “somewhat satisfied” with treatment results. Receiver operating characteristic curve analyses revealed MCIDs of 2.5 for JOACEMQ cervical spine function, 13.0 for upper extremity function, 9.35 for lower extremity function, 9.5 for QOL, 3.9 for SF-36 physical component summary score, 4.2 for NDI, and 0.0485 for EQ-5D.ConclusionThe MCIDs of four outcome measures were determined for patients undergoing cervical laminoplasty.Graphical abstractThese slides can be retrieved under Electronic Supplementary Material.

The Runt-related transcription factor (Runx) family plays various roles in the homeostasis of cartilage. Here, we examined the role of Runx2 and Runx3 for osteoarthritis development in vivo and in vitro. Runx3- knockout mice exhibited accelerated osteoarthritis following surgical induction, accompanied by decreased expression of lubricin and aggrecan. Meanwhile, Runx2 conditional knockout mice showed biphasic phenotypes: heterozygous knockout inhibited osteoarthritis and decreased matrix metallopeptidase 13 (Mmp13) expression, while homozygous knockout of Runx2 accelerated osteoarthritis and reduced type II collagen (Col2a1) expression. Comprehensive transcriptional analyses revealed lubricin and aggrecan as transcriptional target genes of Runx3, and indicated that Runx2 sustained Col2a1 expression through an intron 6 enhancer when Sox9 was decreased. Intra-articular administration of Runx3 adenovirus ameliorated development of surgically induced osteoarthritis. Runx3 protects adult articular cartilage through extracellular matrix protein production under normal conditions, while Runx2 exerts both catabolic and anabolic effects under the inflammatory condition. Possible distinct contributions of Runx 2 and Runx3 in osteoarthritis have not been clarified. Nagata et al . show that Runx3 protects adult articular cartilage by extracellular matrix protein production in normal conditions, while Runx2 exerts both catabolic and anabolic effects during inflammation.

Here we examined the involvement of Notch signaling in the endochondral ossification process, which is crucial for osteoarthritis (OA) development. Intracellular domains of Notch1 and -2 were translocated into the nucleus of chondrocytes with their differentiation in mouse limb cartilage and in mouse and human OA articular cartilage. A tissue-specific inactivation of the Notch transcriptional effector recombination signal binding protein for Ig kappa J (RBPjκ) in chondroprogenitor cells of SRY-box containing gene 9 (Sox9) -Cre ;Rbpj ᶠˡ/ᶠˡ mouse embryos caused an impaired terminal stage of endochondral ossification in the limb cartilage. The RBPjκ inactivation in adult articular cartilage after normal skeletal growth using type II collagen (Col2a1)- Cre ᴱᴿᵀ;Rbpj ᶠˡ/ᶠˡ mice by tamoxifen injection caused resistance to OA development in the knee joint. Notch intracellular domain with the effector RBPjκ stimulated endochondral ossification through induction of the target gene Hes1 in chondrocytes. Among the Notch ligands, Jagged1 was strongly induced during OA development. Finally, intraarticular injection of N -[ N -(3,5-diflurophenylacetate)- l -alanyl]-(S)-phenylglycine t-butyl ester (DAPT), a small compound Notch inhibitor, to the mouse knee joint prevented OA development. The RBPjκ-dependent Notch signaling in chondrocytes modulates the terminal stage of endochondral ossification and OA development, representing an extracellular therapeutic target of OA.

In vitro studies have shown that Rela/p65, a key subunit mediating NF-κB signalling, is involved in chondrogenic differentiation, cell survival and catabolic enzyme production. Here, we analyse in vivo functions of Rela in embryonic limbs and adult articular cartilage, and find that Rela protects chondrocytes from apoptosis through induction of anti-apoptotic genes including Pik3r1 . During skeletal development, homozygous knockout of Rela leads to impaired growth through enhanced chondrocyte apoptosis, whereas heterozygous knockout of Rela does not alter growth. In articular cartilage, homozygous knockout of Rela at 7 weeks leads to marked acceleration of osteoarthritis through enhanced chondrocyte apoptosis, whereas heterozygous knockout of Rela results in suppression of osteoarthritis development through inhibition of catabolic gene expression. Haploinsufficiency or a low dose of an IKK inhibitor suppresses catabolic gene expression, but does not alter anti-apoptotic gene expression. The biphasic regulation of chondrocytes by Rela contributes to understanding the pathophysiology of osteoarthritis. Rela is a transcription factor shown to have seemingly contradictory roles in anabolism and catabolism of cartilage. Here the authors find that Rela prevents chondrocyte apoptosis and that homozygous knockout causes accelerated osteoarthritis in adults, whereas heterozygous knockout suppresses osteoarthritis by maintaining wild-type effects on apoptosis but inhibiting catabolic gene expression.

HIF-1α, an essential transcription factor under hypoxic condition, is indispensable for chondrocytes during skeletal development but its expression and roles in articular chondrocytes are yet to be revealed. We examined HIF-1α protein expression and the hypoxic condition during mouse osteoarthritis (OA) development using state of the art hypoxic probes and found that its expression decreased as OA progressed, coinciding with the change in hypoxic conditions in articular cartilage. Gain- and loss-of-function of HIF-1α in cell culture experiments showed that HIF-1α suppressed catabolic genes such as Mmp13 and Hif2a . We confirmed these anticatabolic effects by measuring glycosaminoglycan release from wild type and conditional knock-out mice femoral heads cultured ex vivo . We went on to surgically induce OA in mice with chondrocyte-specific deletion of Hif1a and found that the development of OA was exacerbated. Increased expression of catabolic factors and activation of NF-κB signalling was clearly evident in the knock-out mice. By microarray analysis, C1qtnf3 was identified as a downstream molecule of HIF-1α, and experiments showed it exerted anti-catabolic effects through suppression of NF-κB. We conclude that HIF-1α has an anti-catabolic function in the maintenance of articular cartilage through suppression of NF-κB signalling.

Although several risk factors have been reported for cervical ossification of the longitudinal ligament (OPLL), most evaluations made in the past were based on plain X-ray, not on computed tomography (CT) scan. In this study, we aimed to clarify novel risk factors for cervical OPLL in asymptomatic subjects undergoing CT scan as their routine medical checkups. A total of 1789 Japanese asymptomatic subjects who underwent CT scan for the whole body as their routine medical checkups were retrospectively reviewed. The medical checkup also included laboratory examinations, bone mineral status, and ultrasound of the carotid artery. As a result, cervical OPLL was seen in 120 subjects (6.7%). As we compared the demographic and clinical data between subjects with and without OPLL, OPLL group showed older age, higher proportion of male sex, higher BMI, higher incidence of hypertension, higher levels of blood HbA1c and triglyceride, and higher incidence of plaques in the carotid artery. A multivariate logistic regression analysis revealed that age (Odds ratio (OR):1.03), male sex (OR: 1.91), and the presence of plaque in the carotid artery (OR: 1.71) were risk factors for OPLL. To the best of our knowledge, this is the first report to reveal an association between OPLL and arteriosclerotic lesions.

This study aimed to elucidate mid- to long-term radiological and respiratory outcomes in patients aged 7–11 years at index surgery with Marfan syndrome and early-onset scoliosis (EOS) in a retrospective multicenter study. Primary outcomes were final thoracic height and final percentage of predicted vital capacity (%VC) at or after 16 years of age. We identified 21 (6 male and 15 female) patients with a mean age of 9.9 years and mean follow-up period of 149.3 months. Fifteen patients underwent primary fusion, whereas six underwent growth-friendly surgery (GFS). The mean preoperative and final T1–T12 heights were 204.0 mm and 248.0 mm, respectively. Final pulmonary function tests were available for 16 patients, and the mean final %VC was 54.0% with 10 patients exhibiting a final %VC < 60%. A significant moderate association was observed between the final T1–T12 height and final %VC. The predicted final T1–T12 height required for a final %VC of 60% was approximately 260 mm. Although most older patients with Marfan syndrome and EOS acquired a considerably large final T1–T12 height, a larger thoracic height was required for satisfactory respiratory function in many cases; hence, GFS may be indicated even in this population.