Pre-transplant donor-specific anti-human leukocyte antigen antibodies (DSAs) are known risk factors for acute rejection and reduced graft survival after kidney transplantation. DSAs may also develop de novo DSAs (dnDSAs) after transplantation but the clinical implications of these antibodies remain uncertain. We undertook a systematic review of observational studies that examined the association between dnDSAs and graft and patient outcomes (through August 2017) with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system of reporting used to assess the quality of evidence available. Thirty-six studies involving 10 535 transplant recipients were eligible. There was moderate quality evidence that transplant recipients who developed dnDSAs had increased risks of acute antibody-mediated rejection (AMR) [relative risk (RR) 9.66; 95% confidence interval (CI) 6.79–13.73, 16 studies, n = 4174]. For all other outcomes, the evidence was low to very low due to moderate-high heterogeneity and low study quality (acute cellular rejection, RR 2.92; 95% CI 2.16–3.94, 22 studies, n = 4991, low-quality evidence; chronic AMR and transplant glomerulopathy RR 6.78; 95% CI 4.31–10.66, 3 studies, n = 1617, very low-quality evidence; and graft loss RR 4.95; 95% CI 3.81–6.43, 19 studies, n = 5473, low-quality evidence). Meta-regression indicated that deceased kidney donation (R² = 1.00, P < 0.001) and region of study conduction (R² = 0.50, P = 0.005) modified associations between dnDSAs and outcomes. dnDSAs are associated with increased risks of adverse graft and patient outcomes after kidney transplantation, but estimation uncertainty of the augmented risks exist due to limitations such as heterogeneity within the existing literature. Therapeutic interventions targeted to eliminate or prevent these antibodies evaluated in randomized controlled trials are needed to establish whether dnDSAs are causal to transplantation outcomes.

Susceptibility to inflammatory bowel diseases (IBDs), Crohn’s disease (CD), and ulcerative colitis (UC) is linked with loss of intestinal epithelial barrier integrity and mitochondria dysfunction. Steroidogenic acute regulatory (StAR) protein-related lipid transfer (START) domain-containing protein 7 (STARD7) is a phosphatidylcholine-specific (PC-specific) lipid transfer protein that transports PC from the ER to the mitochondria, facilitating mitochondria membrane stabilization and respiration function. The aim of this study was to define the contribution of STARD7 in the regulation of the intestinal epithelial mitochondrial function and susceptibility to colitis. In silico analyses identified significantly reduced expression of STARD7 in patients with UC, which was associated with downregulation of metabolic function and a more severe disease phenotype. STARD7 was expressed in intestinal epithelial cells, and STARD7 knockdown resulted in deformed mitochondria and diminished aerobic respiration. Loss of mitochondria function was associated with reduced expression of tight junction proteins and loss of intestinal epithelial barrier integrity that could be recovered by AMPK activation. Stard7 ^+/– mice were more susceptible to the development of DSS-induced and Il10 ^–/– spontaneous models of colitis. STARD7 is critical for intestinal epithelial mitochondrial function and barrier integrity, and loss of STARD7 function increases susceptibility to IBD.

Exome sequencing is the current standard for diagnosing Mendelian disorders; however, it is generally not considered the first-line test for detecting copy number variants (CNVs). We retrospectively investigated the additional diagnostic yield by performing concurrent CNV analysis using exome data in a large and diverse pediatric cohort. Patients were referred from various sources with variable phenotypes. Human Phenotype Ontology terms were used to prioritize variants for analysis. Ancestry and CNV analyses were performed using Somalier and NxClinical, respectively. A total of 1538 patients were tested, with the majority being Admixed Americans. Diagnostic CNVs were identified in 70 patients (4.6%), ranging from exonic deletions to large, unbalanced rearrangements, aneuploidies, and mosaic findings. While no significant differences were identified in diagnostic yield, or rates of negative or uncertain diagnoses, between ancestries, our study demonstrates the feasibility and increased yield of CNV analysis of exome data, across multiple phenotypes, referral sources, and ancestries.

Clinical trials have identified 2 distinct eosinophilic esophagitis (EoE) treatment phenotypes: those that show proton pump inhibitor (PPI) responsiveness (PPI-R) and those that show PPI unresponsiveness (PPI-UR). Comprehensive clinical, endoscopic, and RNA-Seq analyses of patients with EoE prior to and following PPI therapy have not previously been performed to our knowledge. We showed that clinical, endoscopic, and histologic evaluation of esophageal biopsies from pediatric PPI-R and PPI-UR individuals with EoE prior to PPI therapy (diagnosis) were indistinguishable. RNA-Seq analyses revealed common immune and inflammatory transcriptional signatures in both PPI-R EoE and PPI-UR EoE esophageal biopsy samples at diagnosis and distinct signatures enriched for processes related to neuropeptide signaling and cell cycle and division. PPI therapy induced histologic, endoscopic, and transcriptional remission in PPI-R EoE, but not in PPI-UR EoE. Persistent disease in PPI-UR EoE was associated with the presence of Th2 inflammatory and dedifferentiated esophageal epithelial transcriptomic signatures, while PPI-R EoE revealed genes enriched in cellular responses to LPS, host defense against viruses, and type I IFN signaling. In silico analyses identified common and unique EoE disease gene drivers in PPI-R and PPI-UR EoE. These studies indicate that the 2 EoE phenotypes have unique transcriptomic elements that underlie the molecular nature of PPI-R and PPI-UR EoE disease.

Mast cells (MCs) are derived from CD34⁺ hematopoietic progenitors, consist of different subtypes, and are involved in several inflammatory conditions. However, our understanding of human MC developmental trajectories and subtypes has been limited by a scarcity of suitable cellular model systems. Herein, we developed an in vitro model of human MC differentiation from induced pluripotent stem cells (iPSC) to study human MC differentiation trajectories. Flow cytometry characterization of hemopoietic cells derived from the myeloid cells-forming complex (MCFC) revealed an initial increase in Lin^- CD34⁺ hematopoietic progenitors within Weeks 1-3, followed by an increase in CD34^- CD45RA^- SSC^low and SSC^high hematopoietic cells. The Lin^- CD34⁺ hematopoietic progenitors consisted of SSC^low CD45RA^- CD123^± c-Kit⁺ FcεRI⁺ populations that were β7-integrin^high CD203c⁺ and β7-integrin^high CD203c^- cells consistent with CMP^FcεRI+ cells. Flow cytometry and cytologic analyses of the CD34^- Lin^- (SSC^low) population revealed hypogranular cell populations, predominantly characterized by CD45RA^- CD123^± c-Kit⁺ FcεRI^- β7-integrin^low and CD45RA^- CD123^± c-Kit^- FcεRI⁺ β7-integrin^Mid cells. Analyses of hypergranular SSC^high cells identified Lin^- CD34^- CD45RA^- c-Kit⁺ FcεRI^- and Lin^- CD34^- CD45RA^- c-Kit⁺ FcεRI⁺ cells. scRNA-seq analysis of the cells harvested at week 4 of the MCFC culture revealed the presence of monocyte and granulocyte progenitors (n = 547 cells, 26.7 %), Erythrocyte / unknown (n = 85, 4.1 %), neutrophils / myelocytes (n = 211 cells, 10.2 %), mast cell progenitor 1 (n = 599, 29.1 %), mast cell progenitor 2 (n = 152, 7.4 %), committed mast cell precursor (n = 113, 5.5 %), and MCs (n = 353, 17.1 %). In silico analyses of the MC precursor and mature MC populations revealed transcriptionally distinct MC precursor subtype and mature MC states (CMA1⁺ and CMA1^- subtypes). Culturing MC precursor populations in MC maturation media (mast cell media II) led to homogenous mature MC populations as evidenced by high expression of high-affinity IgE receptor, metachromatic granules, presence of MC granule proteins (Tryptase and Chymase) and activation following substance P stimulation and FcεRI crosslinking. This human iPSC-based approach generates MC precursors and phenotypically mature and functional MC populations. This system will be a useful model to generate human MC populations and broaden our understanding of MC biology and transcriptional regulation of MC differentiation trajectories.