Coupling dynamics of a geared multibody system supported by Elastohydrodynamic lubricated cylindrical joints

A comprehensive computational methodology to study the coupling dynamics of a geared multibody system supported by ElastoHydroDynamic (EHD) lubricated cylindrical joints is proposed throughout this work. The geared multibody system is described by using the Absolute-Coordinate-Based (ACB) method that combines the Natural Coordinate Formulation (NCF) describing rigid bodies and the Absolute Nodal Coordinate Formulation (ANCF) characterizing the flexible bodies. Based on the finite-short bearing approach, the EHD lubrication condition for the cylindrical joints supporting the geared system is considered here. The lubrication forces developed at the cylindrical joints are obtained by solving the Reynolds’ equation via the finite difference method. For the evaluation of the normal contact forces of gear pair along the Line Of Action (LOA), the time-varying mesh stiffness, mesh damping and Static Transmission Error (STE) are utilized. The time-varying mesh stiffness is calculated by using the Chaari’s methodology. The forces of sliding friction along the Off-Line-Of-Action (OLOA) are computed by using the Coulomb friction models with a time-varying coefficient of friction under the EHD lubrication condition of gear teeth. Finally, two numerical examples of application are presented to demonstrate and validate the proposed methodology.National Natural Science Foundations of China under Grant 11290151, 11221202 and 11002022, Beijing Higher Education Young Elite Teacher Project under Grant YETP1201

Inhibitor of PD-1/PD-L1: a new approach may be beneficial for the treatment of idiopathic pulmonary fibrosis

Abstract Idiopathic pulmonary fibrosis (IPF) is a globally prevalent, progressive disease with limited treatment options and poor prognosis. Because of its irreversible disease progression, IPF affects the quality and length of life of patients and imposes a significant burden on their families and social healthcare services. The use of the antifibrotic drugs pirfenidone and nintedanib can slow the progression of the disease to some extent, but it does not have a reverse effect on the prognosis. The option of lung transplantion is also limited owing to contraindications to transplantation, possible complications after transplantation, and the risk of death. Therefore, the discovery of new, effective treatment methods is an urgent need. Over recent years, various studies have been undertaken to investigate the relationship between interstitial pneumonia and lung cancer, suggesting that some immune checkpoints in IPF are similar to those in tumors. Immune checkpoints are a class of immunosuppressive molecules that are essential for maintaining autoimmune tolerance and regulating the duration and magnitude of immune responses in peripheral tissues. They can prevent normal tissues from being damaged and destroyed by the immune response. While current studies have focused on PD-1/PD-L1 and CTLA-4, PD-1/PD-L1 may be the only effective immune checkpoint IPF treatment. This review discusses the application of PD-1/PD-L1 checkpoint in IPF, with the aim of finding a new direction for IPF treatment

A Novel Variation in the Mitochondrial Complex I Assembly Factor NDUFAF5 Causes Isolated Bilateral Striatal Necrosis in Childhood

Background: Bilateral striatal necrosis (BSN) is characterized by symmetrical degeneration, predominantly of the caudate and putamen nucleus, in the basal ganglia. It is associated with numerous acquired and hereditary neuro-developmental and motor dysfunction-related pathological conditions. BSN results in high morbidity and mortality among infants and children, and its diagnosis is clinically challenging due to several overlapping disease phenotypes. Therefore, a precise genetic diagnosis is urgently needed for accurate genetic counseling and improved prognostic outcomes as well.Objective: To identify novel missense mutations in the NDUFAF5 gene as a cause of childhood BSN in members of a Chinese family and summarize the clinical characteristics of patients with the NDUFAF5 gene mutations.Methods: This study included a large family living in a remote northwestern area of China. Three siblings developed a neurological disorder characterized by generalized dystonia within the first decade of their lives. Cerebral computed tomography (CT) and magnetic resonance imaging (MRI) showed bilateral lesions of the putamen. Biochemical and genetic approaches were used to identify the cause of BSN.Results: Sequence analysis showed no pathogenic variation in PANK2, SLC25A19, SLC19A3, and NUP62 genes and in the entire mitochondrial genome as well. Whole-exome sequencing revealed compound heterozygous mutations consisting of NDUFAF5:c.425A > C(p.E142A) and c.836T > G (p.M279R). The father, a healthy sister, and a healthy brother of the affected siblings carried the c.836T > G mutation, and the mother carried the c.425A > C mutation. These variants were absent in 100 ethnically matched non-BSN controls. In silico analysis demonstrated that the E142A and M279R mutations in NDUFAF5 protein significantly perturbed the normal conformation of the protein due to alterations in the hydrogen bonding patterns around the evolutionarily conserved catalytic domains, leading to its loss of function in the early stage of mitochondrial complex I assembly.Conclusions: We identified a novel compound heterozygous mutation (c.425A > C and c.836T > G) in the NDUFAF5 gene as the potential cause of autosomal recessive childhood BSN, which extended the pathogenic variation spectrum of the NDUFAF5 gene. This study provides substantial evidence for further improvement of genetic counseling and better clinical management of BSN affected individuals

HIF-1a Pathway, As a Signal Funnel for Genetic, Epigenetic, and Metabolic Aberrations, Is Sufficient and Essential for MDS Development

Abstract Myelodysplastic Syndromes (MDS) are heterogeneous clonal hematopoietic disorders, which are characterized by ineffective hematopoiesis and uni- or multi-lineage dysplasia. Despite the fact that a variety of genetic, epigenetic, and metabolic aberrations have been identified, the clinical features for MDS remain similar, indicating that there is a common underlying mechanism for MDS pathogenesis. Accumulating clinical and research evidence has shown the involvement of systemic inflammation and activated immune signaling in MDS pathogenesis. Hypoxia inducible factor-1α (HIF-1α) is a critical transcription factor for the hypoxic response, angiogenesis, and cancer development. Importantly, HIF-1α is also a key regulator for immune cell activation. To determine whether MDS patients have an activated HIF-1α signature, we analyzed a public gene expression array data set of CD34+ BM cells from a large cohort of MDS patients (n = 183). Although HIF-1α mRNA remains unchanged, some HIF-1α target genes relating with survival/cell growth, glucose metabolism, and invasion/metastasis were significantly activated in the broad spectrum of MDS. We further determined HIF-1α expression in the BM biopsies from MDS patients (n = 39) using immunohistochemistry staining. We found a high frequency of HIF-1α expressed cells in both low- and high-risk IPSS groups. Consistent with this human data, deficiency of frequently mutated genes in MDS resulted in an activated HIF-1α signature in mice. We found that the levels of Hif-1α protein in the c-Kit+ BM cells from Dnmt3a-KO, Runx1-KO, and Mll-partial tandem duplication (PTD) knock-in (MllPTD/WT) mice were significantly upregulated compared with those from WT controls. Although the expression level of Hif-1α protein in the c-Kit+ BM cells from Tet2-KO mice was not changed, they had an activated HIF-1α signature. IDH1/2 mutations are also known to elevate Hif-1α proteins. These results suggest that the HIF-1α pathway is widely activated in MDS patients by MDS-genic mutations through different mechanisms. To determine whether HIF-1α is sufficient for developing MDS phenotypes, we generated blood specific inducible HIF-1α transgenic mice. Using Vav1-Cre/Rosa26-loxP-Stop-loxP (LSL) rtTA driver, stable HIF-1α can be induced in a doxycycline dependent manner. HIF-1α-induced mice developed thrombocytopenia, leukocytopenia, and macrocytic anemia. We found micromegakaryocyte and multi-segmented megakaryocyte formations which are a major diagnostic criteria for MDS. In the BM of anemic mice, we found significant reduction of basophilic and polychromatic erythroblasts. The central macrophages are known to form erythroblastic islands that play a critical role in the late stage of erythropoiesis. Both the frequency and absolute number of F4/80+ Ter119+ BM erythroblastic islands were significantly decreased in HIF-1α-induced mice compared to the control mice. We also found activation of both innate and adaptive immunity in HIF-1α-induced mice. Lineage specific HIF-1α induction revealed the cell-intrinsic effect of HIF-1α on aberrant megakaryocytopoiesis and cell-extrinsic effect of HIF-1α on macrocytic anemia development. We have previously shown that MllPTD/WT mice develop several MDS-associated features, such as increased self-renewal and apoptosis in HSPCs, expansion of myeloid progenitors, and skewed myeloid differentiation. Synergistic effects between MLL-PTD and RUNX1 mutant (S291fs) or Runx1 deletion, further accumulated the Hif-1α protein and caused a variety of MDS features that phenocopy the human MDS. To understand the role of HIF-1α in the context of MDS pathogenesis, we took genetic and pharmacologic approaches. Hif-1α deletion significantly abrogated disease development and rescued macrocytic anemia and thrombocytopenia. This is not due to the elimination of donor derived cells. After the deletion of Hif-1α, a majority of donor derived cells in PB were still CD11b+ cells. HIF-1α inhibition significantly reduced colony formation of MllPTD/WT/RUNX1-291fs cells and MllPTD/WT/Runx1D/D cells in vitro, and prolonged survival of MDS mice in vivo. In conclusion, we identified the sufficient and essential role of HIF-1α in developing MDS. These findings implicate that HIF-1α pathway may be the common underlying mechanism of MDS pathophysiology and could be an effective therapeutic target for a broad spectrum of MDS patients. Disclosures Shih: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding

RUNX1/CBFβ Dosage Is Critical for MLL Leukemias Development

Abstract Transcription factors RUNX1/CBFβ play critical roles in hematopoiesis. Both of them are frequently involved in chromosomal translocations, point mutations, or deletions in acute leukemia. The mixed lineage leukemia (MLL) gene is also frequently involved in chromosomal translocations or partial tandem duplication in acute leukemia. We have previously shown that MLL, RUNX1, and CBFβ interact and form a regulatory complex to regulate downstream target genes. However, the functional consequence of MLL fusions on RUNX1/CBFβ activity remains unknown. To determine the impact of MLL fusion protein on RUNX1/CBFβ, we introduced either MLL, MLL-BP (longer N-terminal Flag-tagged MLL construct which contains CXXC domain; 1-1406), or MLL-fusions together with RUNX1, CBFβ, or both RUNX1 and CBFβ into 293T cells. MLL-BP and MLL fusions significantly decreased RUNX1 levels compared with controls (empty vector and MLL). CBFβ protein was mildly decreased by MLL-BP and MLL-fusions when expressed alone. However, when CBFβ was co-expressed with RUNX1, it was significantly decreased compared with controls. The expression levels of RUNX1 and CBFβ proteins in LSK cells from Mll-Af9 knock-in mice were significantly lower than those from wild-type (WT) mice. To confirm these findings in human acute myeloid leukemia (AML), we measured the expression of RUNX1 and CBFβ at both mRNA and protein levels in various leukemia cell lines. The expression levels of RUNX1 and CBFβ proteins were significantly decreased in AML cells with MLL fusion and MLL partial tandem duplication (MLL-PTD) compared with those in AML cells without MLL aberrations. MLL fusions still have CXXC domain. In MLL-PTD, the CXXC domain is duplicated. Our data showed that RUNX1 protein is not only down-regulated by MLL fusion proteins, but also by MLL-BP. Thus, to determine which region is involved in the down-regulation of RUNX1, we introduced a series of MLL deletion mutants into 293T cells and measured RUNX1 protein expression. MLL deletion mutants without CXXC domain had no effect on RUNX1 stability. The construct which contains point mutations in CXXC domain also lacked the ability to reduce RUNX1 expression. Furthermore, overexpression of only CXXC domain and flanking regions could down-regulate RUNX1 protein expression. These results suggest that MLL fusion proteins and the N-terminal MLL portion of MLL fusions down-regulate RUNX1 and CBFβ protein expression via the MLL CXXC domain and flanking regions. To understand the impact of RUNX1/CBFβ down-regulation on hematopoietic stem and progenitor cells (HSPCs), we generated RUNX1+/–/CBFβ+/– mice as a hypomorph model. The percentage of bone marrow (BM) LSK cells from RUNX1+/–/CBFβ+/– mice was significantly increased compared with that from WT mice. Using BM cells from these mice, we performed in vitro CFU assay and in vivo bone marrow transplantation (BMT) assay. BM cells from RUNX1+/–/CBFβ+/– mice provided more colonies in CFU assay compared with those from WT mice. To determine whether restoration of RUNX1 could repress the MLL mediated leukemogenesis, we retrovirally overexpressed WT RUNX1 in BM cells from Mll-Af9 knock-in mice. Using transduced BM cells, we performed in vitro CFU assay and in vivo BMT assay. RUNX1 overexpressed Mll-Af9 (Mll-Af9/RUNX1) cells underwent terminal differentiation after 2 times replating, while control vector transduced Mll-Af9 (Mll-Af9/Control) cells could still be replated more than 4 times. All the recipient mice transplanted with Mll-Af9/Control cells developed AML. In contrast, all the recipient mice transplanted with Mll-Af9/RUNX1 never develop AML. Furthermore, when we treated MLL leukemia cell lines with DOT1L inhibitor (EPZ-5676), RUNX1 protein levels in these MLL leukemia cell lines were significantly increased 48 hours after the treatment in comparing with controls treated with DMSO. However, there was no significant mRNA expression level change of RUNX1within 48 hours. Future studies are needed to fully understand the mechanism of whether this increasing RUNX1 protein level by DOT1L inhibitor is through blocking CXXC domain and flanking regions mediated degradation. In conclusion, MLL aberrations down-regulate RUNX1/CBFβ via their CXXC domain and flanking regions. Down-regulation of RUNX1/CBFβ plays critical role for MLL mediated leukemia development. Targeting RUNX1/CBFβ levels allows us to test novel therapies for MLL leukemias. Disclosures Mulloy: Celgene: Research Funding; Seattle Genetics: Research Funding; Amgen: Research Funding; NovImmune: Research Funding