Gene expression in human tissue has primarily been studied on the transcriptional level, largely neglecting translational regulation. Here, we analyze the translatomes of 80 human hearts to identify new translation events and quantify the effect of translational regulation. We show extensive translational control of cardiac gene expression, which is orchestrated in a process-specific manner. Translation downstream of predicted disease-causing proteintruncating variants appears to be frequent, suggesting inefficient translation termination. We identify hundreds of previously undetected microproteins, expressed from lncRNAs and circRNAs, for which we validate the protein products in vivo. The translation of microproteins is not restricted to the heart and prominent in the translatomes of human kidney and liver. We associate these microproteins with diverse cellular processes and compartments and find that many locate to the mitochondria. Importantly, dozens of microproteins are translated from lncRNAs with well-characterized noncoding functions, indicating previously unrecognized biology.

The safe application of new strategies for the treatment of graft-versus-host disease (GVHD) is hampered by the lack of a clinically relevant model for preclinical testing. Current models are based on intraperitoneal transfer of human peripheral blood mononuclear cells (huPBMCs) into NOD-SCID (nonobese diabetic-severe combined immunodeficient)/SCID mice. Intravenous transfer would be preferred but this has always been ineffective. We developed a new model for xenogeneic GVHD (X-GVHD) by intravenous transfer of huPBMCs into RAG2 ؊/؊ ␥c ؊/؊ mice. Our results show a high human T-cell chimerism of more than 20% (up to 98%) in more than 90% of mice, associated with a consistent development of X-GVHD within 14 to 28 days and a total mortality rate of 85% shorter than 2 months. After murine macrophage depletion, engraftment was earlier and equally high with lower doses of huPBMCs. Human macrophages were also absent in these mice. Purified huCD3 ؉ cells showed a similar X-GVH effect with contribution of both CD4 and CD8 phenotypes. Human immunoglobulins and cytokines were produced in diseased mice. One of 30 mice developed chronic X-GVHD with skin histology similar to human GVHD. In conclusion, we present a new model for X-GVHD by intravenous transfer of huPBMCs in RAG2 ؊/؊ ␥c ؊/؊ mice. Murine and human macrophages do not seem to be necessary for acute X-GVHD in this model.

Traditionally, mesenchymal stem cells (MSCs) isolated from adult bone marrow were described as being capable of differentiating to various lineages including cartilage. Despite increasing interest in these MSCs, concerns regarding their safety, in vivo behavior and clinical effectiveness have restrained their clinical application. We hypothesized that MSCs have trophic effects that stimulate recycled chondrons (chondrocytes with their native pericellular matrix) to regenerate cartilage. Searching for a proof of principle, this phase I (first-in-man) clinical trial applied allogeneic MSCs mixed with either 10% or 20% recycled autologous cartilage-derived cells (chondrons) for treatment of cartilage defects in the knee in symptomatic cartilage defect patients. This unique first in man series demonstrated no treatment-related adverse events up to one year postoperatively. At 12 months, all patients showed statistically significant improvement in clinical outcome compared to baseline. Magnetic resonance imaging and second-look arthroscopies showed completely filled defects with regenerative cartilage tissue. Histological analysis on biopsies of the grafts indicated hyaline-like regeneration with a high concentration of proteoglycans and type II collagen. Short tandem repeat analysis showed the regenerative tissue only contained patient-own DNA. These findings support the novel insight that the use of allogeneic MSCs is safe and opens opportunities for other applications. Stem cell-induced paracrine mechanisms may play an important role in the chondrogenesis and successful tissue regeneration found. STEM CELLS 2017;35:256-264 SIGNIFICANCE STATEMENTThis is the first study showing allogeneic MSCs are safe and effective in stimulating cartilage regeneration in the knee when combined with autologous chondrons. The fact that one year after surgery, no stem cell DNA could be traced in the regenerative tissue, may confirm the recent view on MSCs as cellular moderators, that stimulate autologous tissue repair through paracrine mechanisms.

Background CD27 is a lymphocyte co-stimulatory molecule that regulates T, NK B, and plasma cell function, survival and differentiation. Based on its function and expression pattern we considered CD27 as a candidate gene in patients with hypogammaglobulinemia. Objective Description of the clinical and immunological phenotype of patients having genetic CD27 deficiency. Methods A molecular and extended immunological analysis was performed on two patients lacking CD27 expression. Results We identified two brothers with a homozygous mutation in CD27 leading to absence of CD27 expression. Both patients suffered from persistent symptomatic EBV viremia. The index patient was hypogammaglobulinemic and immunoglobulin replacement therapy was initiated. His brother developed aplastic anemia in the course of his EBV infection and died from fulminant Gram positive bacterial sepsis. Immunologically, lack of CD27 expression was associated with impaired T-cell dependent B-cell responses and T-cell dysfunction. Conclusion Our findings identify a role for CD27 in humans and suggest that this deficiency can explain particular cases of persistent symptomatic EBV viremia with hypogammaglobulinemia and impaired T cell dependent antibody generation.

Molecular pathology is becoming more and more important in present day pathology. A major challenge for any molecular test is its ability to reliably detect mutations in samples consisting of mixtures of tumor cells and normal cells, especially when the tumor content is low. The minimum percentage of tumor cells required to detect genetic abnormalities is a major variable. Information on tumor cell percentage is essential for a correct interpretation of the result. In daily practice, the percentage of tumor cells is estimated by pathologists on hematoxylin and eosin (H&E)-stained slides, the reliability of which has been questioned. This study aimed to determine the reliability of estimated tumor cell percentages in tissue samples by pathologists. On 47 H&E-stained slides of lung tumors a tumor area was marked. The percentage of tumor cells within this area was estimated independently by nine pathologists, using categories of 0-5%, 6-10%, 11-20%, 21-30%, and so on, until 91-100%. As gold standard, the percentage of tumor cells was counted manually. On average, the range between the lowest and the highest estimate per sample was 6.3 categories. In 33% of estimates, the deviation from the gold standard was at least three categories. The mean absolute deviation was 2.0 categories (range between observers 1.5-3.1 categories). There was a significant difference between the observers (Po0.001). If 20% of tumor cells were considered the lower limit to detect a mutation, samples with an insufficient tumor cell percentage (o20%) would have been estimated to contain enough tumor cells in 27/72 (38%) observations, possibly causing false negative results. In conclusion, estimates of tumor cell percentages on H&E-stained slides are not accurate, which could result in misinterpretation of test results. Reliability could possibly be improved by using a training set with feedback.

Background Arrhythmogenic cardiomyopathy (AC) is tightly associated with desmosomal mutations in the majority of patients. Arrhythmogenesis in AC patients is likely related to remodeling of cardiac gap junctions and increased levels of fibrosis. Recently, using experimental models, we also identified sodium channel dysfunction secondary to desmosomal dysfunction. The aim of the present study was to assess the immunoreactive signal levels of the sodium channel protein NaV1.5, as well as Connexin43 and Plakoglobin, in myocardial specimens obtained from AC patients. Methods Left and right ventricular free wall (LVFW/RVFW) post-mortem material was obtained from 5 AC patients and 5 age and sex-matched controls. RV septal biopsies (RVSB) were taken from another 15 AC patients. All patients fulfilled the 2010 revised Task Force Criteria for AC diagnosis. Immunohistochemical analyses were performed using antibodies against Connexin43 (Cx43), Plakoglobin, NaV1.5, Plakophilin-2 and N-Cadherin. Results N-Cadherin and Desmoplakin immunoreactive signals and distribution were normal in AC patients compared to control. Plakophilin-2 signals were unaffected unless a PKP2 mutation predicting haploinsufficiency was present. Distribution was unchanged compared to control. Immunoreactive signal levels of PKG, Cx43 and NaV1.5 were disturbed in 74%, 70% and 65% of the patients, respectively. Conclusions Reduced immunoreactive signal of PKG, Cx43 and NaV1.5 at the intercalated disks can be observed in a large majority of the patients. Decreased levels of Nav1.5 might contribute to arrhythmia vulnerability and, in the future, potentially could serve as a new clinically relevant tool for risk assessment strategies.

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Aims Growth differentiation factor‐15 (GDF‐15) is a stress‐responsive cytokine and is emerging as a biomarker of cardiac remodelling. Left ventricular assist devices (LVADs) provide unloading of the left ventricle, resulting in partial reverse remodelling. Our aim was to study GDF‐15 in patients with a non‐ischaemic dilated cardiomyopathy (DCM) during LVAD support. Methods and results We analysed circulating GDF‐15 in 30 patients before and 1, 3, and 6 months after LVAD implantation and before heart transplantation or explantation. In addition, mRNA and protein expression of GDF‐15 were evaluated in myocardial tissue obtained prior to and after LVAD support. Circulating GDF‐15 was significantly higher before LVAD implantation as compared with healthy controls (P < 0.001). After 1 month of mechanical support, GDF‐15 levels were significantly decreased compared with pre‐implantation levels (P < 0.001) and remained stable thereafter. Circulating GDF‐15 was significantly correlated with kidney function and the severity of myocardial fibrosis. Interestingly, GDF‐15 mRNA and protein expression in the myocardium were hardly detectable. Conclusions High circulating levels of GDF‐15 in patients with end‐stage non‐ischaemic DCM correlate with myocardial fibrosis and kidney function and decline strongly after 1 month of mechanical unloading, remaining stable thereafter. However, cardiac mRNA and protein expression of GDF‐15 are very low, suggesting that the heart is not an important source of GDF‐15 production in these patients.