Ossification of the posterior longitudinal ligament is linked to heterotopic ossification of the ankle/foot tendons.

INTRODUCTION: Systemic osteogenesis has been speculated to be involved in the pathogenesis of ossification of the posterior longitudinal ligament (OPLL). Our purpose was to compare the radiologic prevalence and severity of heterotopic ossification in foot tendons of Japanese patients with OPLL and to determine their association with systemic heterotopic ossification. MATERIALS AND METHODS: Clinical and radiographic data of 114 patients with OPLL were collected from 2020 to 2022. Control data were extracted from a medical database of 362 patients with ankle radiographs. Achilles and plantar tendon ossification were classified as grades 0-4, and the presence of osteophytes at five sites in the foot/ankle joint was assessed by radiography. Factors associated with the presence and severity of each ossification were evaluated by multivariable logistic regression and linear regression analysis. RESULTS: The prevalence of Achilles and plantar tendon ossification (grade ≥ 2) was 4.0-5.5 times higher in patients with OPLL (40-56%) than in the controls (10-11%). The presence of Achilles tendon ossification was associated with OPLL, age, and coexisting plantar tendon ossification, and was most strongly associated with OPLL (standardized regression coefficient, 0.79; 95% confidence interval, 1.34-2.38). The severity of Achilles and plantar tendon ossification was associated with the severity of ossification of the entire spinal ligament. CONCLUSIONS: The strong association of foot tendon ossification with OPLL suggests that patients with OPLL have a systemic osteogenesis background. These findings will provide a basis for exploring new treatment strategies for OPLL, including control of metabolic abnormalities.

Involvement of Siglec-15 in regulating RAP1/RAC signaling in cytoskeletal remodeling in osteoclasts mediated by macrophage colony-stimulating factor.

DNAX-associated protein 12 kD size (DAP12) is a dominant immunoreceptor tyrosine-based activation motif (ITAM)-signaling adaptor that activates costimulatory signals essential for osteoclastogenesis. Although several DAP12-associated receptors (DARs) have been identified in osteoclasts, including triggering receptor expressed on myeloid cells 2 (TREM-2), C-type lectin member 5 A (CLEC5A), and sialic acid-binding Ig-like lectin (Siglec)-15, their precise role in the development of osteoclasts and bone remodeling remain poorly understood. In this study, mice deficient in Trem-2, Clec5a, Siglec-15 were generated. In addition, mice double deficient in these DAR genes and FcεRI gamma chain (FcR)γ, an alternative ITAM adaptor to DAP12, were generated. Bone mass analysis was conducted on all mice. Notably, Siglec-15 deficient mice and Siglec-15/FcRγ double deficient mice exhibited mild and severe osteopetrosis respectively. In contrast, other DAR deficient mice showed normal bone phenotype. Likewise, osteoclasts from Siglec-15 deficient mice failed to form an actin ring, suggesting that Siglec-15 promotes bone resorption principally by modulating the cytoskeletal organization of osteoclasts. Furthermore, biochemical analysis revealed that Sigelc-15 activates macrophage colony-stimulating factor (M-CSF)-induced Ras-associated protein-1 (RAP1)/Ras-related C3 botulinum toxin substrate 1 (Rac1) pathway through formation of a complex with p130CAS and CrkII, leading to cytoskeletal remodeling of osteoclasts. Our data provide genetic and biochemical evidence that Siglec-15 facilitates M-CSF-induced cytoskeletal remodeling of the osteoclasts.

Flk1 Deficiency and Hypoxia Synergistically Promote Endothelial Dysfunction, Vascular Remodeling, and Pulmonary Hypertension.

BACKGROUND: The mechanisms underlying pulmonary hypertension (PH) remain largely unknown; further, why advanced vascular remodeling preferentially occurs in arterioles is yet to be answered. VEGF (vascular endothelial growth factor) regulates angiogenesis through Flk1 (fetal liver kinase 1) and Flt1 (fms-like tyrosine kinase 1) on endothelial cells (ECs), which may be related to PH pathogenesis. However, spatiotemporal expression patterns of Flk1 and Flt1 in the pulmonary vascular system and the role of endothelial Flk1 in PH development remain poorly understood. METHODS: We analyzed multiple reporter mice, including Flk1-GFP (green fluorescent protein) bacterial artificial chromosome transgenic (Tg), Flt1-DsRed bacterial artificial chromosome Tg, and Flk1-GFP/Flt1-DsRed double Tg mice, to determine the spatiotemporal expression of Flk1 and Flt1 in hypoxia-induced PH. We also used Cdh5CreERT2/Flk1f/f/Tomato (Flk1-KO [knockout]) mice to induce EC-specific Flk1 deletion and lineage tracing in chronic hypoxia. RESULTS: Flk1 was specifically expressed in the ECs of small pulmonary vessels, including arterioles. Conversely, Flt1 was more broadly expressed in the ECs of large- to small-sized vessels in adult mouse lungs. Intriguingly, Flk1+ ECs were transiently increased in hypoxia with proliferation, whereas Flt1 expression was unchanged. Flk1-KO mice did not exhibit pulmonary vascular remodeling nor PH in normoxia; however, the arteriolar ECs changed to a cuboidal shape with protrusion. In hypoxia, Flk1 deletion exacerbated EC dysfunction and reduced their number via apoptosis. Additionally, Flk1 deletion promoted medial thickening and neointimal formation in arterioles and worsened PH. Mechanistically, lineage tracing revealed that neointimal cells were derived from Flk1-KO ECs. Moreover, RNA sequencing in pulmonary ECs demonstrated that Flk1 deletion and hypoxia synergistically activated multiple pathways, including cell cycle, senescence/apoptosis, and cytokine/growth factor, concomitant with suppression of cell adhesion and angiogenesis, to promote vascular remodeling. CONCLUSIONS: Flk1 and Flt1 were differentially expressed in pulmonary ECs. Flk1 deficiency and hypoxia jointly dysregulated arteriolar ECs to promote vascular remodeling. Thus, dysfunction of Flk1+ ECs may contribute to the pathogenesis of advanced vascular remodeling in pulmonary arterioles.

High whole-body bone mineral density in ossification of the posterior longitudinal ligament.

BACKGROUND CONTEXT: Recent studies suggest that ossification of the posterior longitudinal ligament (OPLL) is exacerbated by systemic metabolic disturbances, including obesity. However, although an increase in bone mineral density (BMD) measured at the lumbar spine has been reported in patients with OPLL, no studies have investigated the systemic BMD of patients with OPLL in detail. PURPOSE: We investigated whether patients with OPLL develop increased whole-body BMD. STUDY DESIGN: Single institution cross-sectional study. PATIENT SAMPLE: Data were collected from Japanese patients with symptomatic OPLL (OPLL [+]; n=99). Control data (OPLL [-]; n=226) without spinal ligament ossification were collected from patients who underwent spinal decompression, spinal fusion, or hip replacement surgery. OUTCOME MEASURES: Demographic data, including age, body mass index (BMI), comorbidities, history of treatment for osteoporosis, and history of vertebral and nonvertebral fractures, was obtained from all participants. In addition, whole-body BMD, including the lumbar spine, thoracic spine, femoral neck, skull, ribs, entire upper extremity, entire lower extremity, and pelvis, were measured in all participants using whole-body dual-energy X-ray absorptiometry. METHODS: Patient data were collected from 2018 to 2022. All participants were categorized based on sex, age (middle-aged [<70 years] and older adults [≥70 years]), and OPLL type (localized OPLL [OPLL only in the cervical spine], diffuse OPLL [OPLL in regions including the thoracic spine]), and OPLL [-]) and each parameter was compared. The factors associated with whole-body BMD were evaluated via multivariable linear regression analysis. RESULTS: Compared with the OPLL (-) group, the OPLL (+) group of older women had significantly higher BMD in all body parts (p<.01), and the OPLL (+) group of older men had significantly higher BMD in all body parts except the ribs, forearm, and skull (p<.01). The factors associated with increased BMD of both the femoral neck (load-bearing bone) and skull (nonload-bearing bone) were age, BMI, and coexisting diffuse OPLL in women and BMI and coexisting localized OPLL in men. CONCLUSIONS: Patients with OPLL have increased whole-body BMD regardless of sex, indicating that it is not simply due to load-bearing from obesity. These findings suggested that OPLL is associated with a systemic pathology.

MEF2C/p300-mediated epigenetic remodeling promotes the maturation of induced cardiomyocytes.

Cardiac transcription factors (TFs) directly reprogram fibroblasts into induced cardiomyocytes (iCMs), where MEF2C acts as a pioneer factor with GATA4 and TBX5 (GT). However, the generation of functional and mature iCMs is inefficient, and the molecular mechanisms underlying this process remain largely unknown. Here, we found that the overexpression of transcriptionally activated MEF2C via fusion of the powerful MYOD transactivation domain combined with GT increased the generation of beating iCMs by 30-fold. Activated MEF2C with GT generated iCMs that were transcriptionally, structurally, and functionally more mature than those generated by native MEF2C with GT. Mechanistically, activated MEF2C recruited p300 and multiple cardiogenic TFs to cardiac loci to induce chromatin remodeling. In contrast, p300 inhibition suppressed cardiac gene expression, inhibited iCM maturation, and decreased the beating iCM numbers. Splicing isoforms of MEF2C with similar transcriptional activities did not promote functional iCM generation. Thus, MEF2C/p300-mediated epigenetic remodeling promotes iCM maturation.

Inhibition of microRNA-33b in humanized mice ameliorates nonalcoholic steatohepatitis.

Nonalcoholic steatohepatitis (NASH) can lead to cirrhosis and hepatocellular carcinoma in their advanced stages; however, there are currently no approved therapies. Here, we show that microRNA (miR)-33b in hepatocytes is critical for the development of NASH. miR-33b is located in the intron of sterol regulatory element-binding transcription factor 1 and is abundantly expressed in humans, but absent in rodents. miR-33b knock-in (KI) mice, which have a miR-33b sequence in the same intron of sterol regulatory element-binding transcription factor 1 as humans and express miR-33b similar to humans, exhibit NASH under high-fat diet feeding. This condition is ameliorated by hepatocyte-specific miR-33b deficiency but unaffected by macrophage-specific miR-33b deficiency. Anti-miR-33b oligonucleotide improves the phenotype of NASH in miR-33b KI mice fed a Gubra Amylin NASH diet, which induces miR-33b and worsens NASH more than a high-fat diet. Anti-miR-33b treatment reduces hepatic free cholesterol and triglyceride accumulation through up-regulation of the lipid metabolism-related target genes. Furthermore, it decreases the expression of fibrosis marker genes in cultured hepatic stellate cells. Thus, inhibition of miR-33b using nucleic acid medicine is a promising treatment for NASH.

Generation of a MyoD knock-in reporter mouse line to study muscle stem cell dynamics and heterogeneity.

Myoblast determination protein 1 (MyoD) dynamics define the activation status of muscle stem cells (MuSCs), aiding in muscle tissue regeneration after injury. However, the lack of experimental platforms to monitor MyoD dynamics in vitro and in vivo has hampered the investigation of fate determination and heterogeneity of MuSCs. Herein, we report a MyoD knock-in (MyoD-KI) reporter mouse expressing tdTomato at the endogenous MyoD locus. Expression of tdTomato in MyoD-KI mice recapitulated the endogenous MyoD expression dynamics in vitro and during the early phase of regeneration in vivo. Additionally, we showed that tdTomato fluorescence intensity defines MuSC activation status without immunostaining. Based on these features, we developed a high-throughput screening system to assess the effects of drugs on the behavior of MuSCs in vitro. Thus, MyoD-KI mice are an invaluable resource for studying the dynamics of MuSCs, including their fate decisions and heterogeneity, and for drug screening in stem cell therapy.

Dyslipidemia as a novel risk for the development of symptomatic ossification of the posterior longitudinal ligament.

BACKGROUND CONTEXT: Obesity and visceral fat have been implicated as potential factors in the pathogenesis of the ossification of the posterior longitudinal ligament (OPLL); the details of the factors involved in OPLL remain unclear. PURPOSE: We aimed to determine the association between dyslipidemia and symptomatic OPLL. STUDY DESIGN: Single institution cross-sectional study. PATIENT SAMPLE: Data were collected from Japanese patients with OPLL (n=92) who underwent whole-spine computed tomography scanning. Control data (n=246) without any spinal ligament ossification were collected from 627 Japanese participants who underwent physical examination. OUTCOME MEASURES: Baseline information and lipid parameters, including triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) from fasting blood samples were collected to assess the comorbidity of dyslipidemia. METHODS: Patient data were collected from 2020 to 2022. Patients with dyslipidemia were defined as those who were taking medication for dyslipidemia and who met one of the following criteria: TG ≥150 mg/dL, LDL-C ≥140 mg/dL, and/or HDL-C <40 mg/dL. The factors associated with OPLL development were evaluated using multivariate logistic regression analysis. RESULTS: The comorbidity of dyslipidemia in the OPLL group was more than twice that in the control group (71.7% and 35.4%, respectively). The mean body mass index (BMI) of the OPLL group was significantly higher than that of the control group (27.2 kg/m2 and 23.0 kg/m2). Multivariate logistic regression analysis revealed that dyslipidemia was associated with the development of OPLL (regression coefficient, 0.80; 95% confidence interval, 0.11-1.50). Additional risk factors included age, BMI, and diabetes mellitus. CONCLUSIONS: We demonstrated a novel association between dyslipidemia and symptomatic OPLL development using serum data. This suggests that visceral fat obesity or abnormal lipid metabolism are associated with the mechanisms of onset and exacerbation of OPLL as well as focal mechanical irritation due to being overweight.

Lunar gravity prevents skeletal muscle atrophy but not myofiber type shift in mice.

Skeletal muscle is sensitive to gravitational alterations. We recently developed a multiple artificial-gravity research system (MARS), which can generate gravity ranging from microgravity to Earth gravity (1 g) in space. Using the MARS, we studied the effects of three different gravitational levels (microgravity, lunar gravity [1/6 g], and 1 g) on the skeletal muscle mass and myofiber constitution in mice. All mice survived and returned to Earth, and skeletal muscle was collected two days after landing. We observed that microgravity-induced soleus muscle atrophy was prevented by lunar gravity. However, lunar gravity failed to prevent the slow-to-fast myofiber transition in the soleus muscle in space. These results suggest that lunar gravity is enough to maintain proteostasis, but a greater gravitational force is required to prevent the myofiber type transition. Our study proposes that different gravitational thresholds may be required for skeletal muscle adaptation.

High Throughput Screening of Mitochondrial Bioenergetics in Myoblasts and Differentiated Myotubes.

Skeletal muscles contain stem cells called satellite cells, which are essential for muscle regeneration. The population of satellite cells declines with aging and the incidence of pathological conditions such as muscular dystrophy. There is increasing evidence that metabolic switches and mitochondrial function are critical regulators of cell fate decision (quiescence, activation, differentiation, and self-renewal) during myogenesis. Thus, monitoring and identifying the metabolic profile in live cells using the Seahorse XF Bioanalyzer could provide new insights on the molecular mechanisms governing stem cell dynamics during regeneration and tissue maintenance. Here we described a method to assess mitochondrial respiration (oxygen consumption rate) and glycolysis (ECAR) in primary murine satellite cells, multinucleated myotubes, and C2C12 myoblasts.

Large Maf transcription factor family is a major regulator of fast type IIb myofiber determination.

Myofibers are broadly characterized as fatigue-resistant slow-twitch (type I) fibers and rapidly fatiguing fast-twitch (type IIa/IIx/IIb) fibers. However, the molecular regulation of myofiber type is not entirely understood; particularly, information on regulators of fast-twitch muscle is scarce. Here, we demonstrate that the large Maf transcription factor family dictates fast type IIb myofiber specification in mice. Remarkably, the ablation of three large Mafs leads to the drastic loss of type IIb myofibers, resulting in enhanced endurance capacity and the reduction of muscle force. Conversely, the overexpression of each large Maf in the type I soleus muscle induces type IIb myofibers. Mechanistically, a large Maf directly binds to the Maf recognition element on the promoter of myosin heavy chain 4, which encodes the type IIb myosin heavy chain, driving its expression. This work identifies the large Maf transcription factor family as a major regulator for fast type IIb muscle determination.

Lumbar ossification of the ligamentum flavum reflects a strong ossification tendency of the entire spinal ligament.

Patients with ossification of the ligamentum flavum (OLF) in the lumbar spine may be at high risk of developing concomitant ossification of the entire spinal ligament, but the etiology remains unclear. We investigated the propensity for spinal ligament ossification in asymptomatic subjects with lumbar OLF using the data of 595 Japanese individuals receiving medical check-ups, including computed tomography (CT) scanning. The severity of OLF (total number of intervertebral segments with OLF) of the entire spine on CT was quantified using an OLF index. Subjects with OLF were grouped according to this index: localized OLF (n = 138), intermediate OLF (n = 70), and extensive OLF (n = 31). The proportion of subjects with lumbar OLF increased with increasing OLF index (localized 13.7%, intermediate 41.4%, and extensive 70.9%). Multiple regression analysis found that lumbar OLF index was associated with thoracic OLF index, and co-existence of ossification of the posterior longitudinal ligament (OPLL) of the thoracic and lumbar spine. This study showed that subjects with more multilevel lumbar OLF were more likely to develop multilevel thoracic OLF and to have coexisting OPLL. Patients with lumbar OLF may be a distinctive subgroup with a strong tendency to ossification of the entire spinal ligament.

Cervical Myelopathy Caused by Non-Rheumatic Retro-Odontoid Pseudotumor: An Investigation of Underlying Mechanisms and Optimal Surgical Strategy.

STUDY DESIGN: Retrospective case-control study. OBJECTIVE: This study aimed to identify the underlying pathologies of non-rheumatic retro-odontoid pseudotumors (NRPs), which would help establish an appropriate surgical strategy for myelopathy caused by NRP. METHODS: We identified 35 patients with myelopathy caused by NRP who underwent surgery between 2006 and 2017. An age- and sex-matched control group of 70 subjects was selected from patients with degenerative cervical myelopathy. Radiographic risk factors for NRP were compared between cases and controls. We also assessed surgical outcomes following occipital-cervical (O-C) fusion, atlantoaxial (C1-2) fusion, or C1 laminectomy. RESULTS: Patients with NRP had significantly lower C1 sagittal inner diameter, C2-7 range of motion (ROM), C2-7 Cobb angle, and C7 tilt, as well as significantly higher C1-2 ROM, atlantodental interval (ADI), and C1-2 to O-C7 ROM ratio. Multivariate regression analysis revealed that ADI, C2-7 ROM, and C7 tilt were independent risk factors for NRP. Neurological recovery and pseudotumor size reduction were comparable among surgical procedures, whereas post-operative cervical spine function was significantly lower in the O-C fusion group than in the other groups. CONCLUSION: Non-rheumatic retro-odontoid pseudotumor was associated with an increase in ADI, suggesting that spinal arthrodesis surgery is a reasonable strategy for NRP. C1-2 fusion is preferable over O-C fusion because of the high prevalence of ankylosis in the subaxial cervical spine. Given that 29% of patients with NRP have C1 hypoplasia, such cases can be treated by posterior decompression alone. Our study highlights the need to select appropriate surgical procedures based on the underlying pathology in each case.

Aggravation of Ossified Ligamentum Flavum Lesion Is Associated With the Degree of Obesity.

STUDY DESIGN: Retrospective cross-sectional study. OBJECTIVES: There is insufficient data on the clinical features of ossification of the ligamentum flavum (OLF) of the thoracic spine and the risk of progression of ossified lesions. The link between obesity and ossification of the posterior longitudinal ligament (OPLL), which frequently coexists with OLF, has been demonstrated. However, the link between obesity and OLF has not been recognized. We aimed to determine the prevalence of obesity in thoracic OLF and whether the severity of OLF is associated with the degree of obesity. METHODS: A total of 204 symptomatic Japanese subjects with thoracic OLF and 136 subjects without spinal ligament ossification as controls were included. OLF subjects were divided into 3 groups: 1) localized OLF (OLF <2-intervertebral regions); 2) multilevel OLF (OLF ≥3-intervertebral regions); and 3) OLF + OPLL. The severity of OLF was quantified using the OLF index using computed tomography imaging of the entire spine. RESULTS: The proportion of severely obese subjects (BMI ≥ 30 kg/m2) was significantly higher both in the multilevel OLF group (25.5%) and the OLF + OPLL group (44.3%) than in the localized OLF group (3.6%) and the control group (1.4%) (P < 0.01). BMI, age, and coexistence of cervical OPLL and lumbar OLF were associated with thoracic OLF index in the multiple regression analysis. CONCLUSIONS: Our findings demonstrated that obesity is a distinct feature of multilevel OLF in the thoracic spine and that the severity of OLF is associated with the degree of obesity.

Direct Reprogramming Improves Cardiac Function and Reverses Fibrosis in Chronic Myocardial Infarction.

BACKGROUND: Because adult cardiomyocytes have little regenerative capacity, resident cardiac fibroblasts (CFs) synthesize extracellular matrix after myocardial infarction (MI) to form fibrosis, leading to cardiac dysfunction and heart failure. Therapies that can regenerate the myocardium and reverse fibrosis in chronic MI are lacking. The overexpression of cardiac transcription factors, including Mef2c/Gata4/Tbx5/Hand2 (MGTH), can directly reprogram CFs into induced cardiomyocytes (iCMs) and improve cardiac function under acute MI. However, the ability of in vivo cardiac reprogramming to repair chronic MI with established scars is undetermined. METHODS: We generated a novel Tcf21iCre/reporter/MGTH2A transgenic mouse system in which tamoxifen treatment could induce both MGTH and reporter expression in the resident CFs for cardiac reprogramming and fibroblast lineage tracing. We first tested the efficacy of this transgenic system in vitro and in vivo for acute MI. Next, we analyzed in vivo cardiac reprogramming and fusion events under chronic MI using Tcf21iCre/Tomato/MGTH2A and Tcf21iCre/mTmG/MGTH2A mice, respectively. Microarray and single-cell RNA sequencing were performed to determine the mechanism of cardiac repair by in vivo reprogramming. RESULTS: We confirmed the efficacy of transgenic in vitro and in vivo cardiac reprogramming for acute MI. In chronic MI, in vivo cardiac reprogramming converted ≈2% of resident CFs into iCMs, in which a majority of iCMs were generated by means of bona fide cardiac reprogramming rather than by fusion with cardiomyocytes. Cardiac reprogramming significantly improved myocardial contraction and reduced fibrosis in chronic MI. Microarray analyses revealed that the overexpression of MGTH activated cardiac program and concomitantly suppressed fibroblast and inflammatory signatures in chronic MI. Single-cell RNA sequencing demonstrated that resident CFs consisted of 7 subclusters, in which the profibrotic CF population increased under chronic MI. Cardiac reprogramming suppressed fibroblastic gene expression in chronic MI by means of conversion of profibrotic CFs to a quiescent antifibrotic state. MGTH overexpression induced antifibrotic effects partly by suppression of Meox1, a central regulator of fibroblast activation. CONCLUSIONS: These results demonstrate that cardiac reprogramming could repair chronic MI by means of myocardial regeneration and reduction of fibrosis. These findings present opportunities for the development of new therapies for chronic MI and heart failure.

Posterolateral full-endoscopic debridement and irrigation is effective in treating thoraco-lumbar pyogenic spondylodiscitis, except in cases with large abscess cavities.

PURPOSE: To determine the efficacy and poor prognostic factors of posterolateral full-endoscopic debridement and irrigation (PEDI) surgery for thoraco-lumbar pyogenic spondylodiscitis. METHODS: We included 64 patients (46 men, 18 women; average age: 63.7 years) with thoracic/lumbar pyogenic spondylodiscitis who had undergone PEDI treatment and were followed up for more than 2 years. Clinical outcomes after PEDI surgery were retrospectively investigated to analyze the incidence and risk factors for prolonged and recurrent infection. RESULTS: Of 64 patients, 53 (82.8%) were cured of infection after PEDI surgery, and nine (17.2%) had prolonged or recurrent infection. Multivariate analysis demonstrated that significant risk factors for poor prognosis included a large intervertebral abscess cavity (P = 0.02) and multilevel intervertebral infections (P < 0.05). CONCLUSION: PEDI treatment is an effective, minimally invasive procedure for pyogenic spondylodiscitis. However, a large intervertebral abscess space could cause instability at the infected spinal column, leading to prolonged or recurrent infection after PEDI. In cases with a large abscess cavity with or without vertebral bone destruction, endoscopic drainage alone may have a poor prognosis, and spinal fixation surgery could be considered.

Strong relationship between dyslipidemia and the ectopic ossification of the spinal ligaments.

Obesity and metabolic disturbances are prevalent in ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF); however, the involvement of dyslipidemia (DL) in OPLL/OLF remains uncertain. We investigated the association between dyslipidemia and OPLL/OLF using a dataset of 458 individuals receiving health screening tests, including computed tomography. Subjects were grouped according to the presence or location of OPLL/OLF: controls (no OPLL/OLF, n = 230), OLF (n = 167), cervical OPLL (n = 28), and thoracic OPLL (n = 33). They were also grouped according to the presence of dyslipidemia (DL[+], n = 215; DL[-], n = 243). The proportion of dyslipidemia in the OLF and OPLL groups was 1.6-2.2 times higher than that in the control group. The proportion of OLF and OPLL in the DL(+) group was significantly higher than that in the DL(-) group (OLF, 43% vs. 29%; cervical OPLL, 14.4% vs. 3.2%; thoracic OPLL, 11.1% vs. 3.7%). Multivariate logistic regression analysis showed an association between all ossification types and dyslipidemia. This study demonstrated an association of dyslipidemia with OPLL/OLF; further investigation on the causal relationship between dyslipidemia and ectopic spinal ligament ossification is warranted to develop a therapeutic intervention for OPLL/OLF.

The adhesion G-protein-coupled receptor Gpr116 is essential to maintain the skeletal muscle stem cell pool.

Skeletal muscle is populated with a reservoir of quiescent muscle stem cells (MuSCs), which regenerate the tissue after injury. Here, we show that the adhesion G-protein-coupled receptor Gpr116 is essential for long-term maintenance of the MuSC pool. Quiescent MuSCs express high levels of Gpr116, which is rapidly downregulated upon MuSC activation. MuSCs deficient for Gpr116 exhibit progressive depletion over time and are defective in self-renewal. Adhesion G-protein-coupled receptors contain an agonistic peptide sequence, called the "Stachel" sequence, within their long N-terminal ectodomains. Stimulation of MuSCs with the GPR116 Stachel peptide delays MuSC activation and differentiation. Stachel peptide stimulation of GPR116 leads to strong interaction with ß-arrestins. Stimulation of GPR116 increases the nuclear localization of ß-arrestin1, where it interacts with cAMP response element binding protein to regulate gene expression. Altogether, we propose a model by which GPR116 maintains the MuSC pool via nuclear functions of ß-arrestin1.

Long-Term Clinical Course of Patients After Decompression and Posterior Instrumented Fusion Surgery for Thoracic Ossification of the Posterior Longitudinal Ligament: An Average Follow-Up of 18 years.

STUDY DESIGN: Retrospective observational study. OBJECTIVES: To evaluate the long-term recurrence rates and functional status of patients with thoracic ossification of the posterior longitudinal ligament (OPLL) after decompression and posterior fusion surgery. METHODS: Thirty-seven consecutive patients who underwent posterior thoracic spine surgery at a single institution were retrospectively reviewed. The long-term neurological and functional outcomes of 25 patients who were followed up for ≥10 years after surgery were assessed. Factors associated with the recurrence of myelopathy were also analyzed. RESULTS: The mean preoperative Japanese Orthopaedic Association score was 3.7, which improved to 6.5 at postoperative year 2 and declined to 6.0 at a mean follow-up of 18 years. No patient experienced a relapse of myelopathy due to OPLL within the instrumented spinal segments. However, 15 (60%) patients experienced late neurological deterioration, 10 of whom had a relapse of myelopathy due to OPLL or ossification of the ligamentum flavum (OLF) in the region outside the primary operative lesion, while 4 developed myelopathy due to traumatic vertebral fracture of the ankylosed spine. Young age, a high body mass index, and lumbar OPLL are likely associated with late neurological deterioration. CONCLUSIONS: Decompression and posterior instrumented fusion surgery is a reliable surgical procedure with stable long-term clinical outcomes for thoracic OPLL. However, as OPLL may progress through the spine, attention should be paid to the recurrence of paralysis due to OPLL or OLF in regions other than the primary operative lesion and vertebral fractures of the ankylosed spine after surgery for thoracic OPLL.