Clinical Characteristics of Adolescents With Juvenile Idiopathic Arthritis Transitioning to Adult Rheumatology Care in Canada: Results From the CAPRI Registry.

OBJECTIVE: Using Canadian Alliance of Pediatric Rheumatology Investigators (CAPRI) juvenile idiopathic arthritis (JIA) registry data, we describe (1) clinical characteristics of patients with JIA transitioning to adult care, (2) prevalence of disease-related damage and complications, and (3) changes in disease activity during the final year prior to transfer. METHODS: Registry participants who turned 17 years between February 2017 and November 2021 were included. Clinical characteristics and patient-reported outcomes (PROs) at the last recorded pediatric rheumatology visit, and changes observed in the year prior to that visit were analyzed. Physicians completed an additional questionnaire characterizing cumulative disease-related damage and adverse events by age 17 years. RESULTS: At their last visit, 88 of 131 participants (67%) had inactive and 42 (32%) had active disease. Overall, 96 (73%) were on medications and 41 (31%) were on biologic disease-modifying antirheumatic drugs. Among 80 participants for whom the additional questionnaire was completed, 26% had clinically detected joint damage, 31% had joint damage on imaging, 14% had uveitis, and 7.5% had experienced at least 1 serious adverse event. During the final year, 44.2% of patients were in remission, 28.4% attained inactive disease, and 27.4% became or remained active. Mean scores of PROs were stable overall during that last year, but a minority reported marked worsening. CONCLUSION: A substantial proportion of youth with JIA transitioning to adult care in Canada had a high disease burden, which was reflected by their degree of disease activity, joint damage, or ongoing medication use. These results will inform pediatric and adult providers of anticipated needs during transition of care.

A decade of progress in juvenile idiopathic athritis treatments and outcomes in Canada: results from ReACCh-Out and the CAPRI registry.

OBJECTIVE: To assess changes in juvenile idiopathic arthritis (JIA) treatments and outcomes in Canada, comparing a 2005-2010 and a 2017-2021 inception cohorts. METHODS: Patients enrolled within three months of diagnosis in the Research in Arthritis in Canadian Children Emphasizing Outcomes (ReACCh-Out) and the Canadian Alliance of Pediatric Rheumatology Investigators Registry (CAPRI) cohorts were included. Cumulative incidences of drug starts and outcome attainment within 70 weeks of diagnosis were compared with Kaplan Meier survival analysis and multivariable Cox regression. RESULTS: The 2005-2010 and 2017-2021 cohorts included 1128 and 721 patients, respectively. JIA category distribution and baseline clinical juvenile idiopathic arthritis disease activity (cJADAS10) scores at enrolment were comparable. By 70 weeks, 6% of patients (95% CI 5, 7) in the 2005-2010 and 26% (23, 30) in the 2017-2021 cohort had started a biologic DMARD (bDMARD), and 43% (40, 47) and 60% (56, 64) had started a conventional DMARD (cDMARD), respectively. Outcome attainment was 64% (61, 67) and 83% (80, 86) for Inactive disease (Wallace criteria), 69% (66, 72) and 84% (81, 87) for minimally active disease (cJADAS10 criteria), 57% (54, 61) and 63% (59, 68) for pain control (<1/10), and 52% (47, 56) and 54% (48, 60) for a good health-related quality of life. CONCLUSION: Although baseline disease characteristics were comparable in the 2005-2010 and 2017-2021 cohorts, cDMARD and bDMARD use increased with a concurrent increase in minimally active and inactive disease. Improvements in parent and patient reported outcomes were smaller than improvements in disease activity.

Development and validation of the Kids Disability Screen for children with juvenile idiopathic arthritis: results from the CAPRI Registry.

OBJECTIVE: The aim of this study was to develop and validate a brief disability screen for children with JIA, the Kids Disability Screen (KDS). METHODS: A total of 216 children enrolled in the Canadian Alliance of Pediatric Rheumatology Investigators (CAPRI) Registry in 2017-2018 formed a development cohort, and 220 children enrolled in 2019-2020 formed a validation cohort. At every clinic visit, parents answered two questions derived from the Childhood Health Assessment Questionnaire (CHAQ): 'Is it hard for your child to run and play BECAUSE OF ARTHRITIS?' ('Hard' 0-10), and 'Does your child usually need help from you or another person BECAUSE OF ARTHRITIS?' ('Help', 0-10). We used 36-fold cross-validation and tested nine different mathematical methods to combine the answers and optimize psychometric properties. The results were confirmed in the validation cohort. RESULTS: Expressed as the mean of the two answers, KDS best balanced ease of use and psychometric properties, while a LASSO regression model combining the two answers with other patient characteristics [estimated CHAQ [eCHAQ]) had the highest responsiveness. In the validation cohort, 22.7%, 25.9% and 28.6% of patients had a score of 0 at enrolment for the KDS, eCHAQ and CHAQ, respectively. Responsiveness was 0.67, 0.74 and 0.62, respectively. Sensitivity to detect a CHAQ > 0 was 0.90 and specificity 0.56, KDS detecting some disability in 44% of children with a CHAQ = 0. CONCLUSION: This simple KDS has psychometric properties comparable with those of a full CHAQ and may be used at every clinic visit to identify those children who need a full disability assessment.

Impact of the COVID-19 pandemic on juvenile idiopathic arthritis presentation and research recruitment: results from the CAPRI registry.

OBJECTIVE: The COVID-19 pandemic has disrupted healthcare delivery and clinical research worldwide, with data from areas most affected demonstrating an impact on rheumatology care. This study aimed to characterize the impact of the pandemic on the initial presentation of JIA and JIA-related research in Canada. METHODS: Data collected from the Canadian Alliance of Pediatric Rheumatology Investigators JIA Registry from the year pre-pandemic (11 March 2019 to 10 March 2020) was compared with data collected during the first year of the pandemic (11 March 2020 to 10 March 2021). Outcomes included time from symptom onset to first assessment, disease severity at presentation and registry recruitment. Proportions and medians were used to describe categorical and continuous variables, respectively. RESULTS: The median time from symptom onset to first assessment was 138 (IQR 64-365) days pre-pandemic vs 146 (IQR 83-359) days during the pandemic. The JIA category frequencies remained overall stable (44% oligoarticular JIA pre-pandemic, 46.8% pandemic), except for systemic JIA (12 cases pre-pandemic, 1 pandemic). Clinical features, disease activity (cJADAS10), disability (CHAQ) and quality of life (JAQQ) scores were similar between the two cohorts. Pre-pandemic, 225 patients were enrolled, compared with 111 in the pandemic year, with the greatest decrease from March to June 2020. CONCLUSIONS: We did not observe the anticipated delay in time to presentation or increased severity at presentation, suggesting that, within Canada, care adapted well to provide support to new patient consults without negative impacts. The COVID-19 pandemic was associated with an initial 50% decrease in registry enrolment but has since improved.

Hemostasis stimulates lymphangiogenesis through release and activation of VEGFC.

Hemostasis associated with tissue injury is followed by wound healing, a complex process by which damaged cellular material is removed and tissue repaired. Angiogenic responses are a central aspect of wound healing, including the growth of new lymphatic vessels by which immune cells, protein, and fluid are transported out of the wound area. The concept that hemostatic responses might be linked to wound healing responses is an old one, but demonstrating such a link in vivo and defining specific molecular mechanisms by which the 2 processes are connected has been difficult. In the present study, we demonstrate that the lymphangiogenic factors vascular endothelial growth factor C (VEGFC) and VEGFD are cleaved by thrombin and plasmin, serine proteases generated during hemostasis and wound healing. Using a new tail-wounding assay to test the relationship between clot formation and lymphangiogenesis in mice, we find that platelets accelerate lymphatic growth after injury in vivo. Genetic studies reveal that platelet enhancement of lymphatic growth after wounding is dependent on the release of VEGFC, but not VEGFD, a finding consistent with high expression of VEGFC in both platelets and avian thrombocytes. Analysis of lymphangiogenesis after full-thickness skin excision, a wound model that is not associated with significant clot formation, also revealed an essential role for VEGFC, but not VEGFD. These studies define a concrete molecular and cellular link between hemostasis and lymphangiogenesis during wound healing and reveal that VEGFC, the dominant lymphangiogenic factor during embryonic development, continues to play a dominant role in lymphatic growth in mature animals.

Hippo signaling is required for Notch-dependent smooth muscle differentiation of neural crest.

Notch signaling has well-defined roles in the assembly of arterial walls and in the development of the endothelium and smooth muscle of the vasculature. Hippo signaling regulates cellular growth in many tissues, and contributes to regulation of organ size, in addition to other functions. Here, we show that the Notch and Hippo pathways converge to regulate smooth muscle differentiation of the neural crest, which is crucial for normal development of the aortic arch arteries and cranial vasculature during embryonic development. Neural crest-specific deletion of the Hippo effectors Yap and Taz produces neural crest precursors that migrate normally, but fail to produce vascular smooth muscle, and Notch target genes such as Jagged1 fail to activate normally. We show that Yap is normally recruited to a tissue-specific Jagged1 enhancer by directly interacting with the Notch intracellular domain (NICD). The Yap-NICD complex is recruited to chromatin by the DNA-binding protein Rbp-J in a Tead-independent fashion. Thus, Hippo signaling can modulate Notch signaling outputs, and components of the Hippo and Notch pathways physically interact. Convergence of Hippo and Notch pathways by the mechanisms described here might be relevant for the function of these signaling cascades in many tissues and in diseases such as cancer.

A curious case of growth failure and hypercalcemia: Questions.

BACKGROUND: Sarcoidosis is a multisystem granulomatous disease of unknown etiology that rarely presents in childhood. Here, we report a case of pediatric sarcoidosis presenting with renal failure and hypercalcemia. CASE DIAGNOSIS/TREATMENT: A previously well 14-year-old Caucasian boy was admitted to the Hospital for Sick Children, Canada, for hypertension and renal failure following work-up by his family physician for initial concerns of growth failure. On admission, his weight was 35 kg (<3rd percentile), his height was 148 cm (≪3rd percentile), and his blood pressure was 154/116 mmHg (>99th percentile for height). Laboratory findings showed elevated creatinine (218 µmol/L), hypercalcemia (3.21 mmol/L), and normocytic anemia (hemoglobin 105 g/L). His further assessment showed a urinary concentrating defect with hypercalciuria (calcium/creatinine 1.76 mmol/mmol) and nephrocalcinosis on ultrasound. His eye examination showed uveitis with conjunctival biopsy remarkable for granulomas, which led to pursuit of a diagnosis of possible sarcoidosis. Angiotensin-converting enzyme was found to be high at 96 U/L, and he had a renal biopsy that was consistent with interstitial nephritis with granulomas. Treatment was started with prednisone leading to resolution of his hypercalcemia but persistence of his mild chronic kidney disease. CONCLUSIONS: This case represents an atypical presentation of a rare pediatric disease and highlights the spectrum of renal manifestations and treatment options in sarcoidosis.

A curious case of growth failure and hypercalcemia: Answers.

BACKGROUND: Sarcoidosis is a multisystem granulomatous disease of unknown etiology that rarely presents in childhood. Here, we report a case of pediatric sarcoidosis, presenting with renal failure and hypercalcemia. CASE DIAGNOSIS/TREATMENT: A previously well 14-year-old Caucasian boy was admitted to the Hospital for Sick Children, Canada, for hypertension and renal failure following work-up by his family physician for initial concerns of growth failure. On admission, his weight was 35 kg (<3rd percentile), his height was 148 cm (<<3rd percentile), and his blood pressure was 154/116 mmHg (>99th percentile for height). Laboratory findings showed elevated creatinine (218 umol/L), hypercalcemia (3.21 mmol/L), and normocytic anemia (hemoglobin 105 g/L). His further assessment showed a urinary concentrating defect with hypercalciuria (calcium/creatinine 1.76 mmol/mmol) and nephrocalcinosis on ultrasound. His eye examination showed uveitis with conjunctival biopsy remarkable for granulomas, which led to pursuit of a diagnosis of possible sarcoidosis. Angiotensin Angiotensin-converting enzyme was found to be high at 96 U/L, and he had a renal biopsy that was consistent with interstitial nephritis with granulomas. Treatment was started with prednisone leading to resolution of his hypercalcemia but persistence of his mild chronic kidney disease. CONCLUSIONS: This case represents an atypical presentation of a rare pediatric disease and highlights the spectrum of renal manifestations and treatment options in sarcoidosis.

Phosphoregulatory protein 14-3-3 facilitates SAC1 transport from the endoplasmic reticulum.

Most secretory cargo proteins in eukaryotes are synthesized in the endoplasmic reticulum and actively exported in membrane-bound vesicles that are formed by the cytosolic coat protein complex II (COPII). COPII proteins are assisted by a variety of cargo-specific adaptor proteins required for the concentration and export of secretory proteins from the endoplasmic reticulum (ER). Adaptor proteins are key regulators of cargo export, and defects in their function may result in disease phenotypes in mammals. Here we report the role of 14-3-3 proteins as a cytosolic adaptor in mediating SAC1 transport in COPII-coated vesicles. Sac1 is a phosphatidyl inositol-4 phosphate (PI4P) lipid phosphatase that undergoes serum dependent translocation between the endoplasmic reticulum and Golgi complex and controls cellular PI4P lipid levels. We developed a cell-free COPII vesicle budding reaction to examine SAC1 exit from the ER that requires COPII and at least one additional cytosolic factor, the 14-3-3 protein. Recombinant 14-3-3 protein stimulates the packaging of SAC1 into COPII vesicles and the sorting subunit of COPII, Sec24, interacts with 14-3-3. We identified a minimal sorting motif of SAC1 that is important for 14-3-3 binding and which controls SAC1 export from the ER. This LS motif is part of a 7-aa stretch, RLSNTSP, which is similar to the consensus 14-3-3 binding sequence. Homology models, based on the SAC1 structure from yeast, predict this region to be in the exposed exterior of the protein. Our data suggest a model in which the 14-3-3 protein mediates SAC1 traffic from the ER through direct interaction with a sorting signal and COPII.

Tissue engineering of decellularized pancreas scaffolds for regenerative medicine in diabetes.

Diabetes mellitus is a global disease requiring long-term treatment and monitoring. At present, pancreas or islet transplantation is the only reliable treatment for achieving stable euglycemia in Type I diabetes patients. However, the shortage of viable pancreata for transplantation limits the use of this therapy for the majority of patients. Organ decellularization and recellularization is emerging as a promising solution to overcome the shortage of viable organs for transplantation by providing a potential alternative source of donor organs. Several studies on decellularization and recellularization of rodent, porcine, and human pancreata have been performed, and show promise for generating usable decellularized pancreas scaffolds for subsequent recellularization and transplantation. In this state-of-the-art review, we provide an overview of the latest advances in pancreas decellularization, recellularization, and revascularization. We also discuss clinical considerations such as potential transplantation sites, donor source, and immune considerations. We conclude with an outlook on the remaining work that needs to be done in order to realize the goal of using this technology to create bioengineered pancreata for transplantation in diabetes patients. STATEMENT OF SIGNIFICANCE: Pancreas or islet transplantation is a means of providing insulin-independence in diabetes patients. However, due to the shortage of viable pancreata, whole-organ decellularization and recellularization is emerging as a promising solution to overcome organ shortage for transplantation. Several studies on decellularization and recellularization of rodent, porcine, and human pancreata have shown promise for generating usable decellularized pancreas scaffolds for subsequent recellularization and transplantation. In this state-of-the-art review, we highlight the latest advances in pancreas decellularization, recellularization, and revascularization. We also discuss clinical considerations such as potential transplantation sites, donor source, and immune considerations. We conclude with future work that needs to be done in order to realize clinical translation of bioengineered pancreata for transplantation in diabetes patients.

Choosing Wisely: The Canadian Rheumatology Association Pediatric Committee's List of Items Physicians and Patients Should Question.

OBJECTIVE: To develop a list of tests or treatments frequently used in pediatric rheumatology practice that may be unnecessary based on existing evidence. METHODS: A Choosing Wisely (CW) working group composed of 16 pediatric rheumatologists, 1 allied health professional, 1 parent, and 1 patient used the Delphi method to generate, rank, and refine a list of tests and treatments that may be unnecessary or harmful. The items with the highest content agreement and perceived impact were presented in a survey to all Canadian Rheumatology Association (CRA) physicians who practice pediatric rheumatology. Respondents were asked to rate their agreement and impact, and to rank the items. Five items with the highest composite scores and 2 additional items selected by the CW working group were put forward for literature review. RESULTS: The initial Delphi procedure generated 80 items. After 3 rounds, the list was narrowed to 13 items. The survey was completed by 41/81 (51%) CRA pediatric members across Canada. Respondent characteristics were similar to those of the CRA pediatric membership for self-reported gender, geographical location, and career stage. The highest composite score items were antinuclear antibody testing, drug toxicity monitoring, HLA-B27 testing, rheumatoid factor/anticyclic citrullinated peptide testing, and Lyme serology testing. Two additional items (numerous or repeated intraarticular corticosteroid injections, and autoinflammatory diseases genetic testing) were also selected. Literature review was performed for these 7 highest priority items. CONCLUSION: We have identified areas for quality improvement in the evaluation and treatment of rheumatic diseases in Canadian children.

Manufacturing clinical-grade human induced pluripotent stem cell-derived beta cells for diabetes treatment.

The unlimited proliferative capacity of human pluripotent stem cells (hPSCs) fortifies it as one of the most attractive sources for cell therapy application in diabetes. In the past two decades, vast research efforts have been invested in developing strategies to differentiate hPSCs into clinically suitable insulin-producing endocrine cells or functional beta cells (ß cells). With the end goal being clinical translation, it is critical for hPSCs and insulin-producing ß cells to be derived, handled, stored, maintained and expanded with clinical compliance. This review focuses on the key processes and guidelines for clinical translation of human induced pluripotent stem cell (hiPSC)-derived ß cells for diabetes cell therapy. Here, we discuss the (1) key considerations of manufacturing clinical-grade hiPSCs, (2) scale-up and differentiation of clinical-grade hiPSCs into ß cells in clinically compliant conditions and (3) mandatory quality control and product release criteria necessitated by various regulatory bodies to approve the use of the cell-based products.

Generating pancreatic beta-like cells from human pluripotent stem cells.

Diabetes is a major healthcare burden globally, affecting over 463 million people today, according to the International Diabetes Federation. The most common types of diabetes are Type I diabetes (T1D) and Type II diabetes (T2D), characterized by hyperglycemia due to autoimmune destruction of ß cells (T1D) and ß cell dysfunction, usually on a background of insulin resistance (T2D). There is currently no cure for diabetes, and patients with T1D require lifelong insulin therapy. Additionally, while most cases of T2D can be managed by lifestyle and diet modifications, with or without antidiabetic drugs, severe cases of T2D may also require insulin therapy. The only means to restore stable euglycemia in these patients is now via whole pancreas or islet transplantation. However, this is limited by the scarcity of donors. In recent years, advances in human pluripotent stem cell (hPSC) technologies and pancreatic ß cell differentiation protocols have opened up new potential avenues for cell replacement therapies for diabetes. These advances have also created opportunities to use hPSC-derived ß-like cells for studies of disease mechanisms and drug discovery, which in turn have the potential to lead to better therapies for diabetes patients. Here, we describe the protocol used in our laboratory to generate ß-like cells from hPSCs to study the mechanisms underlying various types of diabetes.

Prevalence of shiga toxin-producing Escherichia coli as detected by enzyme-linked immunoassays and real-time PCR during the summer months in northern Alberta, Canada.

Shiga toxin-producing Escherichia coli (STEC) in northern Alberta was detected using two enzyme immunoassays and an in-house real-time PCR. Of 2,328 stool samples, 8 were positive for O157:H7 STEC and 13 were positive for non-O157 STEC. No significant gender (P = 0.17) or age (P = 0.81) differences between groups were seen. Most positive diarrheal stool samples were nonbloody.

Whole-body MRI Quantification for Assessment of Bone Lesions in Chronic Nonbacterial Osteomyelitis Patients Treated With Pamidronate: A Prevalence, Reproducibility, and Responsiveness Study.

OBJECTIVE: The purpose of this study was (1) to assess the interreader reliability in detecting and scoring the inflammatory bone lesions in pediatric patients with chronic nonbacterial osteomyelitis (CNO) by using whole-body magnetic resonance imaging (WB-MRI), and (2) to evaluate the responsiveness of the MRI-detected CNO lesions to pamidronate therapy. METHODS: Eighty-eight WB-MRI examinations were independently reviewed and scored by 2 radiologists blinded to clinical details in 32 retrospectively enrolled pediatric patients with CNO. Inflammatory bone lesions, soft tissue abnormality, and bony structural changes were scored before and after pamidronate therapy. Lesion responsiveness was calculated by using standardized response mean and interreader reliability was assessed by k statistics. RESULTS: There was good to excellent interreader agreement for the detection and quantification of bone lesions. After the first cycle of pamidronate in all 32 patients, 96 of the 279 lesions (34%; after excluding 108 lesions of hand and feet) resolved, whereas in a subset of 11 patients with 2 or more cycles, 76% of lesions resolved after the second cycle. Twenty-one (7.5%) lesions worsened and 46 (16.4%) new lesions developed after 1 cycle in all 32 patients. In these 11 patients, the number of worsened lesions reduced to 2 (2%) and new lesions to 14 (14.9%) after the second cycle as detected on MRI. Vertebral lesions had the highest response to treatment. CONCLUSION: WB-MRI is a reliable tool for objective quantification and assessment of response to treatment of pediatric CNO bone lesions and could be used to monitor disease activity for clinical and research purposes.

Metformin Perturbs Pancreatic Differentiation From Human Embryonic Stem Cells.

Metformin is becoming a popular treatment before and during pregnancy, but current literature on in utero exposure to metformin lacks long-term clinical trials and mechanistic studies. Current literature on the effects of metformin on mature pancreatic ß-cells highlights its dual, opposing, protective, or inhibitory effects, depending on metabolic environment. However, the impact of metformin on developing human pancreatic ß-cells remains unknown. In this study, we investigated the potential effects of metformin exposure on human pancreatic ß-cell development and function in vitro. In the absence of metabolic challenges such as high levels of glucose and fatty acids, metformin exposure impaired the development and function of pancreatic ß-cells, with downregulation of pancreatic genes and dysfunctional mitochondrial respiration. It also affected the insulin secretion function of pancreatic ß-cells. These findings call for further in-depth evaluation of the exposure of human embryonic and fetal tissue during pregnancy to metformin and its implications for long-term offspring health.

Genetic blockade of lymphangiogenesis does not impair cardiac function after myocardial infarction.

In recent decades, treatments for myocardial infarction (MI), such as stem and progenitor cell therapy, have attracted considerable scientific and clinical attention but failed to improve patient outcomes. These efforts indicate that more rigorous mechanistic and functional testing of potential MI therapies is required. Recent studies have suggested that augmenting post-MI lymphatic growth via VEGF-C administration improves cardiac function. However, the mechanisms underlying this proposed therapeutic approach remain vague and untested. To more rigorously test the role of lymphatic vessel growth after MI, we examined the post-MI cardiac function of mice in which lymphangiogenesis had been blocked genetically by pan-endothelial or lymphatic endothelial loss of the lymphangiogenic receptor VEGFR3 or global loss of the VEGF-C and VEGF-D ligands. The results obtained using all 3 genetic approaches were highly concordant and demonstrated that loss of lymphatic vessel growth did not impair left ventricular ejection fraction 2 weeks after MI in mice. We observed a trend toward excess fluid in the infarcted region of the left ventricle, but immune cell infiltration and clearance were unchanged with loss of expanded lymphatics. These studies refute the hypothesis that lymphangiogenesis contributes significantly to cardiac function after MI, and suggest that any effect of exogenous VEGF-C is likely to be mediated by nonlymphangiogenic mechanisms.

Atypical cadherin FAT4 orchestrates lymphatic endothelial cell polarity in response to flow.

The atypical cadherin FAT4 has established roles in the regulation of planar cell polarity and Hippo pathway signaling that are cell context dependent. The recent identification of FAT4 mutations in Hennekam syndrome, features of which include lymphedema, lymphangiectasia, and mental retardation, uncovered an important role for FAT4 in the lymphatic vasculature. Hennekam syndrome is also caused by mutations in collagen and calcium binding EGF domains 1 (CCBE1) and ADAM metallopeptidase with thrombospondin type 1 motif 3 (ADAMTS3), encoding a matrix protein and protease, respectively, that regulate activity of the key prolymphangiogenic VEGF-C/VEGFR3 signaling axis by facilitating the proteolytic cleavage and activation of VEGF-C. The fact that FAT4, CCBE1, and ADAMTS3 mutations underlie Hennekam syndrome suggested that all 3 genes might function in a common pathway. We identified FAT4 as a target gene of GATA-binding protein 2 (GATA2), a key transcriptional regulator of lymphatic vascular development and, in particular, lymphatic vessel valve development. Here, we demonstrate that FAT4 functions in a lymphatic endothelial cell-autonomous manner to control cell polarity in response to flow and is required for lymphatic vessel morphogenesis throughout development. Our data reveal a crucial role for FAT4 in lymphangiogenesis and shed light on the mechanistic basis by which FAT4 mutations underlie a human lymphedema syndrome.

Spondyloarthritis Research Consortium of Canada Scoring System for Sacroiliitis in Juvenile Spondyloarthritis/Enthesitis-related Arthritis: A Reliability, Validity, and Responsiveness Study.

OBJECTIVE: Intra- and interreader reliability, construct validity, and responsiveness of the Spondyloarthritis Research Consortium of Canada (SPARCC) magnetic resonance imaging (MRI) scoring system were investigated for scoring sacroiliitis in patients with juvenile spondyloarthritis (JSpA)/enthesitis-related arthritis (ERA) who have received biologic and/or nonbiologic treatment. METHODS: Ninety whole-body MRI examinations with dedicated oblique coronal planes of the sacroiliac joints in 46 patients were independently reviewed and scored by 2 pediatric musculoskeletal radiologists, blinded to clinical details, using the SPARCC system. Intra- and interreader reliability was assessed by intraclass correlation coefficients (ICC). Construct validity testing was done by (1) correlating the SPARCC MRI scores of sacroiliitis with clinical disease activity indicators (cross-sectional validity), and (2) correlating the change in the MRI score with the change in clinical indicators before and after treatment (longitudinal validity). Responsiveness of the MRI and clinical indicators was also evaluated, grouped by biologic and nonbiologic treatment. RESULTS: When applied in children with JSpA/ERA, the SPARCC showed almost perfect intra- and interreader reliability (ICC 0.79-1.00). There was poor cross-sectional and longitudinal correlation between clinical assessment indicators and MRI scoring. SPARCC scores showed higher responsiveness to treatment-related change than most clinical outcome measures. Three clinical outcome measures correlated longitudinally with SPARCC score in nonbiologic treatment: active joint count (r = 0.72, p < 0.001), FABER (Flexion, Abduction, External Rotation) test (r = 0.58, p = 0.012), and physician's global assessment (r = 0.61, p = 0.034). CONCLUSION: The SPARCC MRI scoring system is a reliable tool with relatively higher responsiveness than clinical indicators and is suitable for objective quantification of sacroiliitis when applied to pediatric patients with JSpA/ERA.

Lymphatic mimicry in maternal endothelial cells promotes placental spiral artery remodeling.

Molecular heterogeneity of endothelial cells underlies their highly specialized functions during changing physiological conditions within diverse vascular beds. For example, placental spiral arteries (SAs) undergo remarkable remodeling to meet the ever-growing demands of the fetus - a process which is deficient in preeclampsia. The extent to which maternal endothelial cells coordinate with immune cells and pregnancy hormones to promote SA remodeling remains largely unknown. Here we found that remodeled SAs expressed the lymphatic markers PROX1, LYVE1, and VEGFR3, mimicking lymphatic identity. Uterine natural killer (uNK) cells, which are required for SA remodeling and secrete VEGFC, were both sufficient and necessary for VEGFR3 activation in vitro and in mice lacking uNK cells, respectively. Using Flt4Chy/+ mice with kinase inactive VEGFR3 and Vegfcfl/fl Vav1-Cre mice, we demonstrated that SA remodeling required VEGFR3 signaling, and that disrupted maternal VEGFR3 signaling contributed to late-gestation fetal growth restriction. Collectively, we identified a novel instance of lymphatic mimicry by which maternal endothelial cells promote SA remodeling, furthering our understanding of the vascular heterogeneity employed for the mitigation of pregnancy complications such as fetal growth restriction and preeclampsia.