Cluster analysis defines four groups of Japanese patients with adult-onset Still's disease.

OBJECTIVES: To define groups and characterize differences in the prognosis of patients with adult-onset Still's disease (AOSD). METHODS: We performed a retrospective cohort study. Patients with AOSD were grouped using hierarchical unsupervised cluster analysis according to age, sex, clinical features, and laboratory data. The primary endpoints were overall survival and drug-free remission rate. RESULTS: A total of 153 patients with AOSD were placed into four clusters. Those in Cluster 1 had a young onset, tended to be female, and had fewer complications and moderate ferritin concentrations. Those in Cluster 2 had a young onset and had more complications and higher ferritin concentrations. Those in Cluster 3 had a young onset, tended to be male, and had no lymphadenopathy and fewer complications. Those in Cluster 4 had an older onset, tended to be female, and had more complications and higher ferritin concentrations. Overall survival tended to be lower (P = .0539) in Cluster 4, and drug-free remission was higher in Clusters 1, 2, and 3 [hazard ratios (HRs) 2.19, 3.37, and 3.62 vs. Cluster 4, respectively]. CONCLUSIONS: Four groups of AOSD that have distinct clinical manifestations, ferritin concentrations, severity, and drug-free remission rate were identified, which were lowest in Cluster 4. Graphical Abstract.

A synthetic retinoic acid receptor γ antagonist (7C)-loaded nanoparticle enhances bone morphogenetic protein-induced bone regeneration in a rat spinal fusion model.

BACKGROUND CONTEXT: Bone morphogenetic proteins (BMPs) have potent osteoinductivity and have been applied clinically for challenging musculoskeletal conditions. However, the supraphysiological doses of BMPs used in clinical settings cause various side effects that prevent widespread use, and therefore the BMP dosage needs to be reduced. PURPOSE: To address this problem, we synthesized 7C, a retinoic acid receptor γ antagonist-loaded nanoparticle (NP), and investigated its potential application in BMP-based bone regeneration therapy using a rat spinal fusion model. STUDY DESIGN: An experimental animal study. METHODS: Fifty-three male 8-week-old Sprague-Dawley rats underwent posterolateral spinal fusion and were divided into the following five treatment groups: (1) no recombinant human (rh)BMP-2 and blank-NP (Control), (2) no rhBMP-2 and 1 µg 7C-NP (7C group), (3) low-dose rhBMP-2 (0.5 µg) and 1 µg blank-NP (L-BMP group), (4) low-dose rhBMP-2 (0.5 µg) and 1 µg 7C-NP (L-BMP + 7C group), and (5) high-dose rhBMP-2 (5.0 µg) and 1 µg blank-NP (H-BMP group). Micro-computed tomography and histologic analysis were performed 2 and 6 weeks after the surgery. RESULTS: The spinal fusion rates of the Control and 7C groups were both 0%, and those of the L-BMP, L-BMP + 7C, and H-BMP groups were 55.6%, 94.4%, and 100%, respectively. The L-BMP + 7C group markedly promoted cartilaginous tissue formation during BMP-induced endochondral bone formation that resulted in a significantly better spinal fusion rate and bone formation than in the L-BMP group. Although spinal fusion was slower in the L-BMP + 7C group, the L-BMP + 7C group formed a spinal fusion mass with better bone quality than the spinal fusion mass in the H-BMP group. CONCLUSIONS: The combined use of 7C-NP with rhBMP-2 in a rat posterolateral lumbar fusion model increased spinal fusion rate and new bone volume without deteriorating the quality of newly formed bone. CLINICAL SIGNIFICANCE: 7C-NP potentiates BMP-2-induced bone regeneration and has the potential for efficient bone regeneration with low-dose BMP-2, which can reduce the dose-dependent side effects of BMP-2 in clinical settings.

Nutrient-regulated dynamics of chondroprogenitors in the postnatal murine growth plate.

Longitudinal bone growth relies on endochondral ossification in the cartilaginous growth plate, where chondrocytes accumulate and synthesize the matrix scaffold that is replaced by bone. The chondroprogenitors in the resting zone maintain the continuous turnover of chondrocytes in the growth plate. Malnutrition is a leading cause of growth retardation in children; however, after recovery from nutrient deprivation, bone growth is accelerated beyond the normal rate, a phenomenon termed catch-up growth. Although nutritional status is a known regulator of long bone growth, it is largely unknown whether and how chondroprogenitor cells respond to deviations in nutrient availability. Here, using fate-mapping analysis in Axin2CreERT2 mice, we showed that dietary restriction increased the number of Axin2+ chondroprogenitors in the resting zone and simultaneously inhibited their differentiation. Once nutrient deficiency was resolved, the accumulated chondroprogenitor cells immediately restarted differentiation and formed chondrocyte columns, contributing to accelerated growth. Furthermore, we showed that nutrient deprivation reduced the level of phosphorylated Akt in the resting zone and that exogenous IGF-1 restored the phosphorylated Akt level and stimulated differentiation of the pooled chondroprogenitors, decreasing their numbers. Our study of Axin2CreERT2 revealed that nutrient availability regulates the balance between accumulation and differentiation of chondroprogenitors in the growth plate and further demonstrated that IGF-1 partially mediates this regulation by promoting the committed differentiation of chondroprogenitor cells.

Nutrient-regulated dynamics of chondroprogenitors in the postnatal murine growth plate.

Longitudinal bone growth relies on endochondral ossification in the cartilaginous growth plate where chondrocytes accumulate and synthesize the matrix scaffold that is replaced by bone. The chondroprogenitors in the resting zone maintain the continuous turnover of chondrocytes in the growth plate. Malnutrition is a leading cause of growth retardation in children; however, after recovery from nutrient deprivation, bone growth is accelerated beyond the normal rate, a phenomenon termed catch-up growth. Though nutritional status is a known regulator of long bone growth, it is largely unknown if and how chondroprogenitor cells respond to deviations in nutrient availability. Here, using fate-mapping analysis in Axin2Cre ERT2 mice, we showed that dietary restriction increased the number of Axin2+ chondroprogenitors in the resting zone and simultaneously inhibited their differentiation. Once nutrient deficiency was resolved, the accumulated chondroprogenitor cells immediately restarted differentiation and formed chondrocyte columns, contributing to accelerated growth. Furthermore, we showed that nutrient deprivation reduced the level of phosphorylated Akt in the resting zone, and that exogenous IGF-1 canceled this reduction and stimulated differentiation of the pooled chondroprogenitors, decreasing their numbers. Our study of Axin2Cre ERT2 revealed that nutrient availability regulates the balance between accumulation and differentiation of chondroprogenitors in the growth plate, and further demonstrated that IGF-1 partially mediates this regulation by promoting the committed differentiation of the chondroprogenitor cells.

WT1 Trio Peptide-Based Cancer Vaccine for Rare Cancers Expressing Shared Target WT1.

No standard treatment has been established for most rare cancers. Here, we report a clinical trial of a biweekly WT1 tri-peptide-based vaccine for recurrent or advanced rare cancers. Due to the insufficient number of patients available for a traditional clinical trial, the trial was designed for rare cancers expressing shared target molecule WT1. The recruitment criteria included WT1-expressing tumors as well as HLA-A*24:02 or 02:01. The primary endpoints were immunoglobulin G (IgG) antibody (Ab) production against the WT1-235 cytotoxic T lymphocyte (CTL) epitope and delayed-type hypersensitivity (DTH) skin reactions to targeted WT1 CTL epitopes. The secondary endpoints were safety and clinical efficacy. Forty-five patients received WT1 Trio, and 25 (55.6%) completed the 3-month protocol treatment. WT1-235 IgG Ab was positive in 88.0% of patients treated with WT1 Trio at 3 months, significantly higher than 62.5% of the weekly WT1-235 CTL peptide vaccine. The DTH positivity rate in WT1 Trio was 62.9%, which was not significantly different from 60.7% in the WT1-235 CTL peptide vaccine. The WT1 Trio safety was confirmed without severe treatment-related adverse events, except grade 3 myasthenia gravis-like symptoms observed in a patient with thymic cancer. Fifteen (33.3%) patients achieved stable disease after 3 months of treatment. In conclusion, the biweekly WT1 Trio vaccine containing the WT1-332 helper T lymphocyte peptide induced more robust immune responses targeting WT1 than the weekly WT1-235 CTL peptide vaccine. Therefore, WT1-targeted immunotherapy may be a potential therapeutic strategy for rare cancers.

The role of hypertrophic chondrocytes in regulation of the cartilage-to-bone transition in fracture healing.

Endochondral bone formation is an important pathway in fracture healing, involving the formation of a cartilaginous soft callus and the process of cartilage-to-bone transition. Failure or delay in the cartilage-to-bone transition causes an impaired bony union such as nonunion or delayed union. During the healing process, multiple types of cells including chondrocytes, osteoprogenitors, osteoblasts, and endothelial cells coexist in the callus, and inevitably crosstalk with each other. Hypertrophic chondrocytes located between soft cartilaginous callus and bony hard callus mediate the crosstalk regulating cell-matrix degradation, vascularization, osteoclast recruitment, and osteoblast differentiation in autocrine and paracrine manners. Furthermore, hypertrophic chondrocytes can become osteoprogenitors and osteoblasts, and directly contribute to woven bone formation. In this review, we focus on the roles of hypertrophic chondrocytes in fracture healing and dissect the intermingled crosstalk in fracture callus during the cartilage-to-bone transition.

The renoprotective effect of once-weekly GLP-1 receptor agonist dulaglutide on progression of nephropathy in Japanese patients with type 2 diabetes and moderate to severe chronic kidney disease (JDDM67).

AIMS/INTRODUCTION: Few studies have investigated the renoprotective effect of glucagon-like peptide-1 (GLP-1) receptor in patients with chronic kidney disease (CKD). This study evaluated the effect of dulaglutide 0.75 mg on renal function in Japanese patients with type 2 diabetes and CKD stage 3 to 4. MATERIALS AND METHODS: Dulaglutide (group A) and non-dulaglutide (group B) were compared using data collected from a computerized diabetes care database. For group B, propensity score weighting based on propensity scores was performed. Evaluation items were a change from baseline in hemoglobin A1c (HbA1c), body weight, urine albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR), for 3 years. RESULTS: In total, the data obtained from 255 patients (125 and 130 patients for group A and B, respectively) were analyzed. Propensity score-adjusted patient background characteristics (group A vs B) were age 70.8 vs 69.4 years, body weight 70.2 vs 72.9 kg, body mass index 27.3 vs 28.1 kg/m2 , HbA1c 8.4 vs 8.5%, eGFR 47.9 vs 47.7 mL/min/1.73 m2 , and UACR 218 vs 251 mg/gCr. Although there were no statistically significant differences in the change from baseline between groups A and B at most time points in eGFR, a statistically significant eGFR decline in group B was observed in slope analysis for 3 years. This renoprotective effect was marked in patients with macro-albuminuria and/or concomitant SGLT2 inhibitor use. CONCLUSIONS: Dulaglutide slowed the eGFR decline in patients with type 2 diabetes and CKD stage 3 to 4.

Selective Retinoic Acid Receptor γ Antagonist 7C is a Potent Enhancer of BMP-Induced Ectopic Endochondral Bone Formation.

Bone morphogenetic proteins (BMPs) have been clinically applied for induction of bone formation in musculoskeletal disorders such as critical-sized bone defects, nonunions, and spinal fusion surgeries. However, the use of supraphysiological doses of BMP caused adverse events, which were sometimes life-threatening. Therefore, safer treatment strategies for bone regeneration have been sought for decades. Systemic administration of a potent selective antagonist of retinoic acid nuclear receptor gamma (RARγ) (7C) stimulated BMP-induced ectopic bone formation. In this study, we developed 7C-loaded poly lactic nanoparticles (7C-NPs) and examined whether local application of 7C enhances BMP-induced bone regeneration. The collagen sponge discs that absorbed recombinant human (rh) BMP-2 were implanted into the dorsal fascia of young adult mice to induce ectopic bone. The combination of rhBMP-2 and 7C-NP markedly increased the total bone volume and thickness of the bone shell of the ectopic bone in a dose-dependent manner compared to those with rhBMP-2 only. 7C stimulated sulfated proteoglycan production, expression of chondrogenic marker genes, and Sox9 reporter activity in both chondrogenic cells and MSCs. The findings suggest that selective RARγ antagonist 7C or the related compounds potentiate the bone inductive ability of rhBMP-2, as well as support any future research to improve the BMP-2 based bone regeneration procedures in a safe and efficient manner.

Culture Condition of Bone Marrow Stromal Cells Affects Quantity and Quality of the Extracellular Vesicles.

Extracellular vesicles (EVs) released by bone marrow stromal cells (BMSCs) have been shown to act as a transporter of bioactive molecules such as RNAs and proteins in the therapeutic actions of BMSCs in various diseases. Although EV therapy holds great promise to be a safer cell-free therapy overcoming issues related to cell therapy, manufacturing processes that offer scalable and reproducible EV production have not been established. Robust and scalable BMSC manufacturing methods have been shown to enhance EV production; however, the effects on EV quality remain less studied. Here, using human BMSCs isolated from nine healthy donors, we examined the effects of high-performance culture media that can rapidly expand BMSCs on EV production and quality in comparison with the conventional culture medium. We found significantly increased EV production from BMSCs cultured in the high-performance media without altering their multipotency and immunophenotypes. RNA sequencing revealed that RNA contents in EVs from high-performance media were significantly reduced with altered profiles of microRNA enriched in those related to cellular growth and proliferation in the pathway analysis. Given that pre-clinical studies at the laboratory scale often use the conventional medium, these findings could account for the discrepancy in outcomes between pre-clinical and clinical studies. Therefore, this study highlights the importance of selecting proper culture conditions for scalable and reproducible EV manufacturing.

4PBA reduces growth deficiency in osteogenesis imperfecta by enhancing transition of hypertrophic chondrocytes to osteoblasts.

Short stature is a major skeletal phenotype in osteogenesis imperfecta (OI), a genetic disorder mainly caused by mutations in genes encoding type I collagen. However, the underlying mechanism is poorly understood, and no effective treatment is available. In OI mice that carry a G610C mutation in COL1A2, we previously found that mature hypertrophic chondrocytes (HCs) are exposed to cell stress due to accumulation of misfolded mutant type I procollagen in the endoplasmic reticulum (ER). By fate mapping analysis of HCs in G610C OI mice, we found that HCs stagnate in the growth plate, inhibiting translocation of HC descendants to the trabecular area and their differentiation to osteoblasts. Treatment with 4-phenylbutyric acid (4PBA), a chemical chaperone, restored HC ER structure and rescued this inhibition, resulting in enhanced longitudinal bone growth in G610C OI mice. Interestingly, the effects of 4PBA on ER dilation were limited in osteoblasts, and the bone fragility was not ameliorated. These results highlight the importance of targeting HCs to treat growth deficiency in OI. Our findings demonstrate that HC dysfunction induced by ER disruption plays a critical role in the pathogenesis of OI growth deficiency, which lays the foundation for developing new therapies for OI.

Clinical course of different long-acting insulin therapies-glargine U100, U300, degludec, and insulin degludec/insulin aspart-among Japanese patients with type 2 diabetes: a multicenter retrospective observational study (JDDM65 study).

This study aimed to retrospectively compare the clinical efficacy of different types of long-acting insulin therapies-glargine U100, glargine U300, degludec, and insulin degludec/insulin aspart-among Japanese patients with type 2 diabetes after insulin use was initiated in an outpatient setting. The study consisted of 822 insulin-naïve patients in Japan who started using long-acting insulin for treatment of type 2 diabetes and continued for over 12 months. In addition, the impact of insulin type on insulin withdrawal was investigated by dividing the participants into two groups: those who achieved insulin withdrawal and those who did not, during the 12-month observation period based on a Cox proportional hazards model. As a result, HbA1c was decreased, and BMI was increased in all participants regardless of the insulin type used. A total of 185 participants succeeded in insulin withdrawal. After adjustment was made for several confounders, the positive determinant factors for withdrawal were short duration of diabetes and the choice of IDegAsp when compared with Gla100; the negative determinant factor was use of insulin secretagogues at the start of the study. In conclusion, all long-acting insulins were a powerful tool for treatment of type 2 diabetes, and patients with short duration of diabetes and/or no usage of insulin secretagogues resulted in favorable outcomes in terms of insulin withdrawal within a year in an outpatient setting. In addition, insulin degludec/insulin aspart was found to possibly be a better choice for treatment when it was compared with glargine U100 among the four types of insulin.

Inhibition of glucose use improves structural recovery of injured Achilles tendon in mice.

Injured tendons do not regain their native structure except at fetal or very young ages. Healing tendons often show mucoid degeneration involving accumulation of sulfated glycosaminoglycans (GAGs), but its etiology and molecular base have not been studied substantially. We hypothesized that quality and quantity of gene expression involving the synthesis of proteoglycans having sulfated GAGs are altered in injured tendons and that a reduction in synthesis of sulfated GAGs improves structural and functional recovery of injured tendons. C57BL6/j mice were subjected to Achilles tendon tenotomy surgery. The injured tendons accumulated sulfate proteoglycans as early as 1-week postsurgery and continued so by 4-week postsurgery. Transcriptome analysis revealed upregulation of a wide range of proteoglycan genes that have sulfated GAGs in the injured tendons 1 and 3 weeks postsurgery. Genes critical for enzymatic reaction of initiation and elongation of chondroitin sulfate GAG chains were also upregulated. After the surgery, mice were treated with the 2-deoxy-d-glucose (2DG) that inhibits conversion of glucose to glucose-6-phosphate, an initial step of glucose metabolism as an energy source and precursors of monosaccharides of GAGs. The 2DG treatment reduced accumulation of sulfated proteoglycans, improved collagen fiber alignment, and reduced the cross-sectional area of the injured tendons. The modulus of the 2DG-treated groups was higher than that in the vehicle group, but not of statistical significance. Our findings suggest that mucoid degeneration in injured tendons may result from the upregulated expression of genes involved the synthesis of sulfate proteoglycans and can be inhibited by reduction of glucose utilization.

Bronchiectasis is as crucial as interstitial lung disease in the severe pneumonia that occurs during treatment with biologic DMARDs in rheumatoid arthritis: a retrospective cohort study in a single facility.

Interstitial lung disease (ILD) carries a risk for severe pneumonia in patients with rheumatoid arthritis (RA). Bronchiectasis, another risk of severe pneumonia, has not been well elucidated in RA. We investigated the types of respiratory diseases in RA and correlated them to severe pneumonia during the course of treatment using biologic DMARDs (bDMARDs), with special attention to bronchiectasis and ILD. RA patients were examined by computed tomography before starting bDMARDs and divided into three groups: normal, bronchiectasis and ILD. The log-rank test and Dunnett's multiple comparisons test were employed for the statistical analysis. Among 424 patients, 350 were categorized as normal, 32 as having bronchiectasis, and 42 as having ILD. Two in the normal group, three in the bronchiectasis group and four in the ILD group developed severe pneumonia. The log-rank test showed a significant difference among the three groups (p < 0.0001). The pneumonia-free rates in the bronchiectasis and ILD groups were significantly lower than the normal group, respectively, with Dunnett's multiple comparison test (p < 0.0001). This study suggests that the bronchiectasis that occurs in RA carries a risk of severe pneumonia during treatment with bDMARDs that is comparable to ILD.

Usefulness of the severity classification for predicting drug-free remission in Japanese patients with adult-onset Still's disease.

OBJECTIVES: To investigate the usefulness of severity classification for predicting outcomes in patients with adult-onset Still's disease (AOSD). METHODS: This was a multi-centre retrospective cohort study. AOSD patients were classified into mild, moderate, and severe groups based on severity classification (Japanese Ministry of Health, Labour and Welfare) during the initial treatment, and clinical features were compared among these groups. The primary endpoints were the AOSD-related mortality and drug-free remission rate. For comparison, the same analysis was performed in parallel for patient groups stratified by the modified Pouchot systemic score. RESULTS: According to severity classification, 49 (35%), 37 (26%), and 56 patients (39%) were classified into mild, moderate, and severe groups, respectively. Patients in the severe group showed higher frequency of severe complications and the use of biological agents. Although AOSD-related survival was not significantly different (p = .0776), four of the five fatal cases were classified into the severe group. The severe group showed a reduced rate of drug-free remission (p = .0125). Patient groups classified by systemic score did not correlate with survival or drug-free remission. CONCLUSIONS: Severity classification is useful for predicting outcomes in patients with AOSD.

Epstein-Barr virus encephalitis in a patient with rheumatoid arthritis.

A 53-year-old woman with a 6-year history of rheumatoid arthritis (RA) presented with pharyngeal pain, fever, and altered mental status. The patient had been treated with methotrexate (MTX) 12 mg/week, baricitinib 4 mg/day, and tacrolimus 2 mg/day. Magnetic resonance imaging of the brain revealed diffuse high-intensity lesions in the cerebral white matter, basal ganglia, brainstem, and right cerebellar hemisphere. She was diagnosed with Epstein-Barr virus (EBV) encephalitis due to elevated levels of EBV-DNA in the cerebrospinal fluid and serum. Although MTX-associated lymphoproliferative disorders are well-known complications in patients with RA, EBV encephalitis requires careful attention for such patients undergoing treatment with multiple potent immunosuppressants.

Osteochondroma Pathogenesis: Mouse Models and Mechanistic Insights into Interactions with Retinoid Signaling.

Osteochondromas are cartilage-capped tumors that arise near growing physes and are the most common benign bone tumor in children. Osteochondromas can lead to skeletal deformity, pain, loss of motion, and neurovascular compression. Currently, surgery is the only available treatment for symptomatic osteochondromas. Osteochondroma mouse models have been developed to understand the pathology and the origin of osteochondromas and develop therapeutic drugs. Several cartilage regulatory pathways have been implicated in the development of osteochondromas, such as bone morphogenetic protein, hedgehog, and WNT/ß-catenin signaling. Retinoic acid receptor-γ is an important regulator of endochondral bone formation. Selective agonists for retinoic acid receptor-γ, such as palovarotene, have been investigated as drugs for inhibition of ectopic endochondral ossification, including osteochondromas. This review discusses the signaling pathways involved in osteochondroma pathogenesis and their possible interactions with the retinoid pathway.

Administration of a selective retinoic acid receptor-γ agonist improves neuromuscular strength in a rodent model of volumetric muscle loss.

PURPOSE: Volumetric muscle loss is a uniquely challenging pathology that results in irrecoverable functional deficits. Furthermore, a breakthrough drug or bioactive factor has yet to be established that adequately improves repair of these severe skeletal muscle injuries. This study sought to assess the ability of an orally administered selective retinoic acid receptor-γ agonist, palovarotene, to improve recovery of neuromuscular strength in a rat model of volumetric muscle loss. METHODS: An irrecoverable, full thickness defect was created in the tibialis anterior muscle of Lewis rats and animals were survived for 4 weeks. Functional recovery of the tibialis anterior muscle was assessed in vivo via neural stimulation and determination of peak isometric torque. Histological staining was performed to qualitatively assess fibrous scarring of the defect site. RESULTS: Treatment with the selective retinoic acid receptor-γ agonist, palovarotene, resulted in a 38% improvement of peak isometric torque in volumetric muscle loss affected limbs after 4 weeks of healing compared to untreated controls. Additionally, preliminary histological assessment suggests that oral administration of palovarotene reduced fibrous scarring at the defect site. CONCLUSIONS: These results highlight the potential role of selective retinoic acid receptor-γ agonists in the design of regenerative medicine platforms to maximize skeletal muscle healing. Additional studies are needed to further elucidate cellular responses, optimize therapeutic delivery, and characterize synergistic potential with adjunct therapies.

Unexpected suppression of tumorigenesis by c-MYC via TFAP4-dependent restriction of stemness in B lymphocytes.

The proliferative burst of B lymphocytes is essential for antigen receptor repertoire diversification during the development and selective expansion of antigen-specific clones during immune responses. High proliferative activity inevitably promotes oncogenesis, the risk of which is further elevated in B lymphocytes by endogenous gene rearrangement and somatic mutations. However, B-cell-derived cancers are rare, perhaps owing to putative intrinsic tumor-suppressive mechanisms. We show that c-MYC facilitates B-cell proliferation as a protumorigenic driver and unexpectedly coengages counteracting tumor suppression through its downstream factor TFAP4. TFAP4 is mutated in human lymphoid malignancies, particularly in >10% of Burkitt lymphomas, and reduced TFAP4 expression was associated with poor survival of patients with MYC-high B-cell acute lymphoblastic leukemia. In mice, insufficient TFAP4 expression accelerated c-MYC-driven transformation of B cells. Mechanistically, c-MYC suppresses the stemness of developing B cells by inducing TFAP4 and restricting self-renewal of proliferating B cells. Thus, the pursuant transcription factor cascade functions as a tumor suppressor module that safeguards against the transformation of developing B cells.

Fatal Thrombotic Microangiopathy and Posterior Reversible Encephalopathy Syndrome in a Patient with Anti-melanoma Differentiation-associated Gene 5 Antibody-positive Dermatomyositis.

A 56-year-old woman presented with dermatomyositis positive for anti-melanoma differentiation-associated gene 5 antibody. No interstitial lung disease was detected. Despite treatment with methylprednisolone pulse therapy and cyclosporine, dysphagia developed. Furthermore, the presence of thrombocytopenia, elevated lactate dehydrogenase levels, and an undetectable haptoglobin level suggested the possibility of thrombotic microangiopathy (TMA). Disturbed consciousness developed shortly after TMA onset, and brain magnetic resonance imaging revealed hyperintensity lesions in the bilateral basal ganglia, thalami, and brainstem. The patient was diagnosed with atypical posterior leukoencephalopathy syndrome before dying of heart failure later that day. In conclusion, early TMA recognition and prompt intensive treatment are critical in such cases.

Premature Growth Plate Closure Caused by a Hedgehog Cancer Drug Is Preventable by Co-Administration of a Retinoid Antagonist in Mice.

The growth plates are key engines of skeletal development and growth and contain a top reserve zone followed by maturation zones of proliferating, prehypertrophic, and hypertrophic/mineralizing chondrocytes. Trauma or drug treatment of certain disorders can derange the growth plates and cause accelerated maturation and premature closure, one example being anti-hedgehog drugs such as LDE225 (Sonidegib) used against pediatric brain malignancies. Here we tested whether such acceleration and closure in LDE225-treated mice could be prevented by co-administration of a selective retinoid antagonist, based on previous studies showing that retinoid antagonists can slow down chondrocyte maturation rates. Treatment of juvenile mice with an experimental dose of LDE225 for 2 days (100 mg/kg by gavage) initially caused a significant shortening of long bone growth plates, with concomitant decreases in chondrocyte proliferation; expression of Indian hedgehog, Sox9, and other key genes; and surprisingly, the number of reserve progenitors. Growth plate involution followed with time, leading to impaired long bone lengthening. Mechanistically, LDE225 treatment markedly decreased the expression of retinoid catabolic enzyme Cyp26b1 within growth plate, whereas it increased and broadened the expression of retinoid synthesizing enzyme Raldh3, thus subverting normal homeostatic retinoid circuitries and in turn accelerating maturation and closure. All such severe skeletal and molecular changes were prevented when LDE-treated mice were co-administered the selective retinoid antagonist CD2665 (1.5 mg/kg/d), a drug targeting retinoid acid receptor γ, which is most abundantly expressed in growth plate. When given alone, CD2665 elicited the expected maturation delay and growth plate expansion. In vitro data showed that LDE225 acted directly to dampen chondrogenic phenotypic expression, a response fully reversed by CD2665 co-treatment. In sum, our proof-of-principle data indicate that drug-induced premature growth plate closures can be prevented or delayed by targeting a separate phenotypic regulatory mechanism in chondrocytes. The translation applicability of the findings remains to be studied. © 2021 American Society for Bone and Mineral Research (ASBMR).