Murine Injury Model Research Articles

4-Aminobutyrate aminotransferase regulates chondrocyte homeostasis and can be targeted using peptide-sirna nanoparticles to attenuate osteoarthritis in a murine injury model

Purpose: Epigenetic changes, including DNA methylation, regulate cellular homeostasis. We previously showed that DNA methyltransferase 3B (DNMT3B) expression is reduced in murine and human osteoarthritic (OA) articular chondrocytes (ACs); and that DNMT3B loss-of-function (LOF) leads to OA in mice. An unbiased screen of genes regulated by DNMT3B showed that 4-aminobutyrate aminotransferase (Abat) is increased with DNMT3B LOF. Moreover, upregulation of Abat expression in articular chondrocytes was observed in human OA and injury induced murine OA cartilage.

Differential role of MLKL in alcohol-associated and non-alcohol-associated fatty liver diseases in mice and humans.

Hepatocellular death contributes to progression of alcohol–associated (ALD-associated) and non–alcohol-associated (NAFL/NASH) liver diseases. However, receptor-interaction protein kinase 3 (RIP3), an intermediate in necroptotic cell death, contributes to injury in murine models of ALD but not NAFL/NASH. We show here that a differential role for mixed-lineage kinase domain–like protein (MLKL), the downstream effector of RIP3, in murine models of ALD versus NAFL/NASH and that RIP1-RIP3-MLKL can be used as biomarkers to distinguish alcohol-associated hepatitis (AH) from NASH. Phospho-MLKL was higher in livers of patients with NASH compared with AH or healthy controls (HCs). MLKL expression, phosphorylation, oligomerization, and translocation to plasma membrane were induced in WT mice fed diets high in fat, fructose, and cholesterol but not in response to Gao-binge (acute on chronic) ethanol exposure. Mlkl–/– mice were not protected from ethanol-induced hepatocellular injury, which was associated with increased expression of chemokines and neutrophil recruitment. Circulating concentrations of RIP1 and RIP3, but not MLKL, distinguished patients with AH from HCs or patients with NASH. Taken together, these data indicate that MLKL is differentially activated in ALD/AH compared with NAFL/NASH in both murine models and patients. Furthermore, plasma RIP1 and RIP3 may be promising biomarkers for distinguishing AH and NASH.

S100A9 blockade prevents lipopolysaccharide-induced lung injury via suppressing the NLRP3 pathway

BackgroundS100 calcium binding protein A9 (S100A9) is a pro-inflammatory alarmin associated with several inflammation-related diseases. However, the role of S100A9 in lung injury in sepsis has not been fully investigated. Therefore, the present study aimed to determine the role of S100A9 in a lipopolysaccharide (LPS)-induced lung injury murine model and its underlying molecular mechanisms.MethodsLPS was utilized to induce sepsis and lung injury in C57BL/6 or NOD-like receptor family pyrin domain containing 3 (NLRP3)−/− mice. To investigate the effects of S100A9 blockade, mice were treated with a specific inhibitor of S100A9. Subsequently, lung injury and inflammation were evaluated by histology and enzyme‑linked immunosorbent assay (ELISA), respectively. Furthermore, western blot analysis and RT-qPCR were carried out to investigate the molecular mechanisms underlying the effects of S100A9.ResultsS100A9 was upregulated in the lung tissues of LPS-treated mice. However, inhibition of S100A9 alleviated LPS-induced lung injury. Additionally, S100A9 blockade also attenuated the inflammatory responses and apoptosis in the lungs of LPS-challenged mice. Furthermore, the increased expression of NLRP3 was also suppressed by S100A9 blockade, while S100A9 blockade had no effect on NLRP3−/− mice. In vitro, S100A9 downregulation mitigated LPS-induced inflammation. Interestingly, these effects were blunted by NLRP3 overexpression.ConclusionThe results of the current study suggested that inhibition of S100A9 could protect against LPS-induced lung injury via inhibiting the NLRP3 pathway. Therefore, S100A9 blockade could be considered as a novel therapeutic strategy for lung injury in sepsis.

Senolytic therapy ameliorates renal fibrosis postacute kidney injury by alleviating renal senescence.

Acute kidney injury (AKI) is a common clinical problem, and patients who survive AKI have a high risk of chronic kidney disease (CKD). The mechanism of CKD post-AKI, characterized by progressive renal fibrosis, is still unclear. Maladaptive tubular epithelial cells (TECs) after AKI are considered a leading cause of renal fibrosis post-AKI. TECs under maladaptive repair manifest characteristics of senescence. Removing senescent TECs by genetic ablation has been proven effective in reducing renal fibrosis. Senolytics, which eliminate senescent cells by pharmacological intervention, have been studied in a series of degenerative diseases. To our knowledge, the effects of senolytics on renal fibrosis post-AKI have not been verified before. Here, we confirmed renal senescence in the unilateral ischemia/reperfusion injury murine model. Senescent TECs could activate fibroblasts and senolytics specifically induced apoptosis of senescent TECs. Next, we demonstrated that senolytics could reduce renal senescence and ameliorate renal fibrosis in both unilateral renal ischemia/reperfusion injury and multiple-cisplatin-treatment murine models. Our results indicate senescent TECs as a vital factor in renal fibrosis progression, and senolytic therapy might be promising for treating CKD post-AKI.

Defibrotide for the Treatment of Endotheliitis Complicating Sars-Cov-2 Infection: Rationale and Ongoing Studies As Part of the International Defacovid Study Group

Coronavirus disease 2019 (COVID-19) is a heterogeneous clinical condition caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The initial stage of infection occurs at the time of respiratory viral invasion through angiotensin-converting enzyme 2 (ACE2) receptors in alveolar pneumocytes and macrophages. In the second stage of established pulmonary disease without and with hypoxia, viral multiplication and localized inflammation occurs. The third stage COVID-19 is the most severe, characterized by systemic hyperinflammation, acute respiratory distress syndrome (ARDS) and generalized microangiopathy, with significantly elevated biomarkers including IL-2, IL-6, IL-7, granulocyte-colony stimulating factor, macrophage inflammatory protein 1α, tumor necrosis factor-α, C-reactive protein, ferritin, D-dimer, von Willebrand factor (vWF) and thrombomodulin (TM). Evidence suggests that endothelial damage and activation play a key role in the pathobiology of the disease, and thus protecting endothelium and reversing endotheliitis may be a key therapeutic goal (Teuwen et al,Nat Rev Immunol2020).Defibrotide (DF), a complex mixture of poly-deoxyribonucleotides extracted from porcine mucosa, modulates expression of thrombogenic and inflammatory mediators produced in response to endothelial cell injury and/or leukocyte activation. DF increases tissue plasminogen activator (t-PA) and TM expression, thereby enhancing the enzymatic activity of plasmin to hydrolyze fibrin clot, while also decreasing vWF and plasminogen activator inhibitor-1 (PAI-1). Platelet adhesion is inhibited via increases in nitric oxide (NO), prostaglandin I2 (PGI2), and prostaglandin E2 (PGE2) (Falanga A et al,Leukemia 2003). Anti-inflammatory properties via inhibition of p38 MAPK pathway have been demonstrated with DF, attenuating the release of inflammatory mediators including IL-6, thromboxane A2, leukotriene B4, tumor necrosis factor-alpha, and reactive oxygen species (Mitsiades et al,Clin Cancer Res2009). Additionally, DF inhibits both the expression and activity of heparanase, which in turn modulates heparan sulfate, a vital moiety for viral infection (Richardson et al,Blood Adv2018; Koganti et al,Cell Mol Life Sci2020).DF also modulates endothelial cell injury in murine models by down-regulating the expression of endothelial cell adhesion molecules such as E-selectin, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), that are critical to leukocyte adhesion and migration, and by increasing the endothelial cell release of anti-inflammatory cytokines, conferring survival benefit (Garcia-Bernal et al,J Cell Mol Med2020). DF is approved for the treatment of severe veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) complicating stem cell transplantation and has demonstrated efficacy and safety in critically ill patients with multi-organ failure, underpinned by vasculopathy, endotheliitis, immune activation and hemorrhagic risk (Richardson et al,Blood2016). This multi-target and pleiotropic approach makes DF an attractive candidate for the treatment of advanced stage COVID 19 and the systemic endothelial complications underpinning both its pathobiology and ensuing mortality (Figure 1).Various clinical studies in Spain, Italy, Ireland, the UK and USA are underway, with the larger randomized placebo-controlled prospective phase 2 study in Spain (clinicaltrials.gov: NCT04348383) leading in accrual with promising early results, demonstrating safety to date with potential efficacy, as reflected by favorable outcome in a subset of intubated patients as part of an ongoing multi-center trial. Other studies within the group have focused on safety and particularly the therapeutic role of DF in advanced disease, including those patients requiring extracorporeal membrane oxygenation (ECMO) and full dose systemic anticoagulation. These trials include common in-depth biological correlatives, assessing biomarkers including heparanase, inflammatory cytokines, immune cell sub-populations, vWF and soluble TM, as well as other novel markers and pharmacokinetics. In aggregate, these studies will hopefully help demonstrate the effects of DF on the proposed targets in COVID-19 and successfully correlate these effects with improved clinical outcome.DisclosuresMoraleda:Jazz Pharmaceuticals:Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding;Novartis, Sandoz, Takeda:Honoraria;Gilead:Honoraria, Other: Travel expenses.Carlo-Stella:Servier, Novartis, Genenta Science srl, ADC Therapeutics, F. Hoffmann-La Roche, Karyopharm, Jazz Pharmaceuticals:Membership on an entity’s Board of Directors or advisory committees;Bristol-Myers Squibb, Merck Sharp & Dohme, Janssen Oncology, AstraZeneca:Honoraria;Boehringer Ingelheim and Sanofi:Consultancy;ADC Therapeutics and Rhizen Pharmaceuticals:Research Funding.Jara Rubio:Edwards Lifesciences, Getinge:Honoraria.Diaz-Ricart:Jazz Pharmaceuticals:Honoraria, Research Funding;German Jose Carreras Leukaemia Foundation:Research Funding.Carreras:Jazz Pharmaceuticals:Research Funding, Speakers Bureau;German Jose´ Carreras Leukaemia Foundation:Research Funding.Mo:Celgene/BMS:Membership on an entity’s Board of Directors or advisory committees.Cooke:Jazz Pharmaceuticals:Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau.Soiffer:Be the Match/ National Marrow Donor Program:Membership on an entity’s Board of Directors or advisory committees;alexion:Consultancy;Celgene:Membership on an entity’s Board of Directors or advisory committees;Juno:Membership on an entity’s Board of Directors or advisory committees;Novartis:Consultancy;VOR Biopharma:Consultancy;Mana Therapeutics:Consultancy;Precision Bioscience:Consultancy;Cugene:Consultancy;Rheos Therapeutics:Consultancy;Gilead:Consultancy;Kiadis:Membership on an entity’s Board of Directors or advisory committees.Baron:Genetech:Consultancy;Merck:Consultancy.Pagliuca:Jazz Pharmaceuticals:Membership on an entity’s Board of Directors or advisory committees.Richardson:Celgene/BMS, Oncopeptides, Takeda, Karyopharm:Research Funding.OffLabel Disclosure:Defibrotide used for the treatment of endotheliitis complicating SARS-Cov-2 infection

The ins-and-outs of podocyte lipid metabolism

Obesity and hyperlipidemia are the most prevalent independent risk factors of ESRD, suggesting that lipid accumulation is detrimental to renal function. The origin of lipid accumulation (a common feature in podocyte injury) and its pathophysiological relevance are unknown. This commentary discusses the finding by Liu etal. that deficiency of the endoplasmic reticulum enzyme SOAT1, which metabolizes cholesterol to cholesterol esters, attenuates renal/podocyte injury in murine models of diabetes and Alport's syndrome.

Mammalian Target of Rapamycin Complex 2 Signaling Is Required for Liver Regeneration in a Cholestatic Liver Injury Murine Model

Cholestatic liver injury may lead to a series of hepatobiliary syndromes, which can progress to cirrhosis and impaired liver regeneration, eventually resulting in liver-related death. Mammalian target of rapamycin complex 2 (mTORC2) is a major regulator of liver metabolism and tumor development. However, the role of mTORC2 signaling in cholestatic liver injury has not been characterized to date. In this study, we generated liver-specific Rictor knockout mice to block the mTORC2 signaling pathway. Mice were treated with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) to induce cholestatic liver injury. DDC feeding induced cholestatic liver injury and ductular reaction as well as activation of the mTORC2/Akt signaling pathway in wild-type mice. Loss of mTORC2 led to significantly decreased oval cell expansion after DDC feeding. Mechanistically, this phenotype was independent of mTORC1/fatty acid synthase cascade (Fasn) or yes-associated protein (Yap) signaling. Notch pathway was instead strongly inhibited during DDC-induced cholestatic liver injury in liver-specific Rictor knockout mice. Furthermore, mTORC2 deficiency in adult hepatocytes did not inhibit ductular reaction in this cholestatic live injury mouse model. Our results indicated that mTORC2 signaling effectively regulates liver regeneration by inducing oval cell proliferation. Liver progenitor cells or bile duct cells, rather than mature hepatocytes, would be the major source of ductular reaction in DDC-induced cholestatic liver injury.

Therapeutic Interventions to Reduce Radiation Induced Dermal Injury in a Murine Model of Tissue Expander Based Breast Reconstruction.

Radiation therapy (XRT) induced dermal injury disrupts type I collagen architecture. This impairs cutaneous viscoelasticity, which may contribute to the high rate of complications in expander-based breast reconstruction with adjuvant XRT. The objective of this study was to further elucidate the mechanism of radiation-induced dermal injury and to determine if amifostine (AMF) or deferoxamine (DFO) mitigates type I collagen injury in an irradiated murine model of expander-based breast reconstruction. Female Lewis rats (n = 20) were grouped: expander (control), expander-XRT (XRT), expander-XRT-AMF (AMF), and expander-XRT-DFO (DFO). Expanders were surgically placed. All XRT groups received 28 Gy of XRT. The AMF group received AMF 30 minutes before XRT, and the DFO group used a patch for delivery 5 days post-XRT. After a 20-day recovery period, skin was harvested. Atomic force microscopy and Raman spectroscopy were performed to evaluate type I collagen sheet organization and tissue compositional properties, respectively. Type I collagen fibril disorganization was significantly increased in the XRT group compared with the control (83.8% vs 22.4%; P = 0.001). Collagen/matrix ratios were greatly reduced in the XRT group compared with the control group (0.49 ± 0.09 vs 0.66 ± 0.09; P = 0.017). Prophylactic AMF demonstrated a marked reduction in type I collagen fibril disorganization on atomic force microscopy (15.9% vs 83.8%; P = 0.001). In fact, AMF normalized type I collagen organization in irradiated tissues to the level of the nonirradiated control (P = 0.122). Based on Raman spectroscopy, both AMF and DFO demonstrated significant differential protective effects on expanded-irradiated tissues. Collagen/matrix ratios were significantly preserved in the AMF group compared with the XRT group (0.49 ± 0.09 vs 0.69 ± 0.10; P = 0.010). β-Sheet/α-helix ratios were significantly increased in the DFO group compared with the XRT group (1.76 ± 0.03 vs 1.86 ± 0.06; P = 0.038). Amifostine resulted in a significant improvement in type I collagen fibril organization and collagen synthesis, whereas DFO mitigated abnormal changes in collagen secondary structure in an irradiated murine model of expander-based breast reconstruction. These therapeutics offer the ability to retain the native microarchitecture of type I collagen after radiation. Amifostine and DFO may offer clinical utility to reduce radiation induced dermal injury, potentially decreasing the high complication rate of expander-based breast reconstruction with adjuvant XRT and improving surgical outcomes.

Dual assessment of kidney perfusion and pH by exploiting a dynamic CEST-MRI approach in an acute kidney ischemia-reperfusion injury murine model.

Several factors can lead to acute kidney injury, but damage following ischemia and reperfusion injuries is the main risk factor and usually develops into chronic disease. MRI has often been proposed as a method with which to assess renal function. It does so by measuring the renal perfusion of an injected Gd-based contrast agent. The use of pH-responsive agents as part of the CEST (chemical exchange saturation transfer)-MRI technique has recently shown that pH homeostasis is also an important indicator of kidney functionality. However, there is still a need for methods that can provide more than one type of information following the injection of a single contrast agent for the characterization of renal function. Herein we propose, for the first time, dynamic CEST acquisition following iopamidol injection to quantify renal function by assessing both perfusion and pH homeostasis. The aim of this study is to assess renal functionality in a murine unilateral ischemia-reperfusion injury model at two time points (3 and 7 days) after acute kidney injury. The renal-perfusion estimates measured with iopamidol were compared with those obtained with a gadolinium-based agent, via a dynamic contrast enhanced (DCE)-MRI approach, to validate the proposed method. Compared with the contralateral kidneys, the clamped ones showed a significant decrease in renal perfusion, as measured using the DCE-MRI approach, which is consistent with reduced filtration capability. Dynamic CEST-MRI findings provided similar results, indicating that the clamped kidneys displayed significantly reduced renal filtration that persisted up to 7 days after the damage. In addition, CEST-MRI pH imaging showed that the clamped kidneys displayed significantly increased pH values, reflecting the disturbance to pH homeostasis. Our results demonstrate that a single CEST-MRI contrast agent can provide multiple types of information related to renal function and can discern healthy kidneys from pathological ones by combining perfusion measurements with renal pH mapping.

Factor VIIa Induces Biased Cytoprotective Signaling through the Cleavage of Protease Activated Receptor 1 at Canonical Arg41 Site

Endothelial cell protein C receptor (EPCR) interacts with diverse ligands, in addition to its known ligands protein C and activated protein C (APC). We reported earlier that procoagulant clotting factor VIIa (FVIIa) binds EPCR with the same affinity as APC. FVIIa binding to EPCR leads to the down regulation of the EPCR-mediated anticoagulation pathway. Our recent studies showed that FVIIa, like APC, induces EPCR-dependent cytoprotective signaling through activation of protease activated receptor 1 (PAR1). Recent studies of Griffin, Mosnier and their colleagues revealed that APC noncanonical cleavage of PAR1 at Arg46 site that generates a novel tethered ligand is responsible for APC-induced β-arrestin2-dependent PAR1 biased signaling. It is unknown at present whether FVIIa follows a similar mechanism as APC in inducing PAR1 biased signaling. PAR1 reporter constructs - wild-type and cleavage site-specific mutants - were routinely used to investigate PAR1 cleavage by thrombin, APC, or other proteases, and to determine protease-specific cleavage sites in PAR1. Unfortunately, this approach was not useful in determining any FVIIa cleavage site in PAR1. In contrast to thrombin or APC, FVIIa treatment failed to show a detectable cleavage (over the background) of transfected wild-type PAR1 reporter constructs expressed in cultured endothelial cells. However, in other studies, FVIIa was shown to cleave endogenous PAR1 in endothelial cells as assessed by the loss of cleavage-specific PAR1 mAb binding. The recent generation of transgenic mice strains carrying R41Q or R46Q homozygous point mutations in PAR1 has allowed us in the present study to investigate in vivo mechanisms for PAR1-dependent cytoprotective signaling of FVIIa. We employed two murine injury models, LPS-induced inflammation and VEGF-induced barrier disruption. Murine brain endothelial cells isolated from the PAR1 mutated strains and primary human endothelial cells were used to validate in vivo findings and extend the mechanistic studies. Our studies show that administration of rFVIIa (250 µg/kg body weight) reduced LPS-induced cytokine elaboration and neutrophil infiltration in the lung tissues of wild-type (WT) PAR1 and QQ46-PAR1 mice but not in QQ41-PAR1 mice. Similarly, FVIIa suppression of the VEGF-induced barrier disruption was abolished in the QQ41-PAR1 mice but not in WT and the QQ46-PAR1 mice. Parallel experiments conducted with APC showed, as expected, that it protected WT and QQ41-PAR1 mice but not QQ46-PAR1 mice against LPS-induced inflammation and VEGF-mediated barrier destabilization. In vitro signaling studies performed with brain endothelial cells isolated from WT, QQ41-PAR1 and QQ46-PAR1 mice showed that FVIIa activation of Akt in endothelial cells required Arg41 in PAR1. Additional studies showed that FVIIa-cleaved endogenous PAR1 was readily internalized, whereas APC-cleaved PAR1 remained on the cell surface. Very low concentrations of thrombin (< 1 nM) mimicked FVIIa in inducing PAR1-dependent cytoprotective signaling. However, very low concentration thrombin-induced cytoprotective signaling differed from EPCR-FVIIa-induced cytoprotective signaling in the isoform of ß-arrestin required for the protective effect. EPCR-FVIIa-induced PAR1-mediated cytoprotective signaling was soley mediated via the β-arrestin1-dependent pathway whereas very low dose thrombin-induced cytoprotective effects appear to be mediated by either β-arrestin1 or β-arrestin2. Silencing of ß-arrestin1 or ß-arrestin2 alone did not affect the protective effects of very low doses of thrombin, but the silencing both ß-arrestin1 and ß-arrestin2 together completely prevented a low dose of thrombin-induced protective effect. In summary, our data strongly support the hypothesis that the in vivo mechanism of action for FVIIa's pharmacologic benefits in curbing inflammation and endothelial barrier disruption involves biased signaling of PAR1 due to cleavage at Arg41. Moreover, our studies demonstrate that very low concentrations of thrombin are also capable of inducing PAR1 biased beneficial -cytoprotective signaling by coupling to either ß-arrestin1 or 2. These results emphasize the striking diversity of PAR1's conformational states and interactomes that initiate canonical and biased signaling. Disclosures No relevant conflicts of interest to declare.

Visfatin Exerts Immunotherapeutic Effects in Lipopolysaccharide-Induced Acute Lung Injury in Murine Model.

Visfatin acts as a significant regulator of inflammatory cytokines. However, the immunological response and therapeutic effects of visfatin under bacterial stress in murine lung tissue are still not clear. To investigate the role of visfatin on lipopolysaccharide (LPS)-induced acute lung injury (ALI), thirty Kunming mice were divided into Saline, LPS, and LPS + visfatin groups. After routine blood examination, the effects of visfatin on inflammatory cytokines, lung tissue structure, and expression of inflammatory mediators were explored through hematoxylin-eosin (H&E), Masson and immunohistochemical staining, quantitative polymerase chain reaction (Q-PCR), and Western blotting. Compared with the Saline group, neutrophil percentage, peripheral blood neutrophil count, and the ratio of lymphocyte count (NLR) were upregulated in LPS group. Moreover, Masson staining showed alterations in lung tissue structure; the mRNA level of different cytokines (IL-6, IL-1β, TNF-α, IL-10, TLR4, IFN-γ) was upregulated; and the protein expression of interleukin (IL)-6, myeloperoxidase (MPO), and transforming growth factor-β1 (TGF-β) was significantly (p < 0.05) different in LPS group. Compared with LPS group, neutrophil percentage significantly decreased (p < 0.01), the numbers of lymphocytes significantly (p < 0.05) increased, NLR decreased, Masson staining of the lung was extremely different (p < 0.01), the structure of the lung was slightly damaged, and the myeloperoxidase values of lung showed no differences in LPS + visfatin. Hence, visfatin inhibits the lung inflammation induced by ALI. During the ALI, visfatin acts by decreasing NLR, downregulated the expression of MPO, enhanced antioxidant capacity, and regulated the inflammatory factors IL-1β, IL-6, IL-10, and TNF-α to reduce the lung injury.

17β-estradiol alters mRNA co-expression after murine muscle injury and mild hypobaria.

Here, we assessed the effects of 17β-estradiol exposure on mRNA co-expression patterns of muscle tissue during recovery in a closed muscle crush injury and hypobaria exposure murine model. Eighteen ovariectomized placebo-treated and 18 ovariectomized 17β-estradiol-treated female mice underwent closed muscle crush injury and hypobaric simulated flight. The mice recovered for 32, 96, or 192 h, and then were euthanized. Their harvested injured lateral gastrocnemius muscles underwent microarray analysis. We used weighted gene co-expression network analysis to construct a co-expression network for the control mice, and then applied the same network to the estrogen-treated mice. We compared the relationships between co-expression in gene modules over time between the two experimental groups. Enriched functional cluster analyses of significant co-expression network modules document a variety of different pathways of interest. Some of the functional cluster enrichments within several of the significantly correlated modules are related to the formation and function of microtubules. Our findings demonstrate that following a closed muscle crush injury in a murine model, the presence of 17β-estradiol alters mRNA co-expression patterns over time. It appears that estrogen promotes the expression of mRNA related to microtubule activity within the cytoskeleton of myofibers and in movement of organelles and receptors. Further study is needed, but the enrichment of these microtubule-related pathways may be integral in the muscle tissue regeneration process, and thus suggests that the presence of estrogen may promote muscle recovery through the work of the microtubules. Impact statement This study uses a murine model to address the clinical situation of transporting soldiers or civilians who have sustained skeletal muscle trauma by air. Our findings show that crush-injured muscle tissue of ovariectomized, 17β-estradiol-treated mice exposed to mild hypobaric hypoxia exhibited mRNA co-expression patterns among pathways associated with microtubule-dependent processes. Palmitoylation and other pathways necessary for movement of estrogen receptors to the cell membrane were also differentially enriched in the estrogen-treated mice. These first findings reframe the discussion regarding estrogen effects during muscle recovery from an inflammation-oriented inquiry to that of a structural, cytoskeletal inquiry and support additional research to understand the non-inflammation-related influences of estrogen during muscle recovery. Also, these results may suggest a role for estrogen or estrogen-like substances to treat muscle trauma.

Accelerated post traumatic osteoarthritis in a dual injury murine model

Joint injury involving destabilisation of the joint and damage to the articular cartilage (e.g., sports-related injury) can result in accelerated post-traumatic osteoarthritis (PTOA). Destabilised medial meniscotibial ligament (DMM) surgery is one of the most commonly used murine models and whilst it recapitulates Osteoarthritis (OA) pathology, it does not necessarily result in multi-tissue injury, as occurs in PTOA. We hypothesised that simultaneous cartilage damage and joint destabilisation would accelerate the onset of OA pathology. OA was induced in C57BL/6 mice via (a) DMM, (b) microblade scratches of articular cartilage (CS) or (c) combined DMM and cartilage scratch (DCS). Mice were culled 7, 14 and 28 days post-surgery. Microcomputed tomography (μCT) and histology were used to monitor bone changes and inflammation. Dynamic weight bearing, an indirect measure of pain, was assessed on day 14. Osteophytogenesis analysis via μCT revealed that osteophytes were present in all groups at days 7 and 14 post-surgery. However, in DCS, osteophytes were visually larger and more numerous when compared with DMM and cartilage scratch (CS). Histological assessment of cartilage at day 14 and 28, revealed significantly greater damage in DCS compared with DMM and CS. Furthermore, a significant increase in synovitis was observed in DCS. Finally, at day 14 osteophyte numbers correlated with changes in dynamic weight bearing. Joint destabilisation when combined with simultaneous cartilage injury accelerates joint deterioration, as seen in PTOA. Thus, DCS provides a novel and robust model for investigating multiple pathological hallmarks, including osteophytogenesis, cartilage damage, synovitis and OA-related pain.

Kidney Injury in Murine Models of Hematopoietic Stem Cell Transplantation.

Acute graft-versus-host disease (GVHD) affects different organs, including the skin, liver, and gastrointestinal tract. Although kidneys are not among the organs commonly known to be the target of acute GVHD, kidney damage is frequently reported after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We have studied the effect of bone marrow transplantation (BMT) on the kidneys in different murine models of GVHD. We found that glomerular damage in the kidneys is a common pathological finding in mice after BMT. The histopathological features of glomeruli damage included mesengiolysis, mesangial proliferation and edema, subendothelial and endothelial thickening, splitting of capillary walls in glomeruli, narrowing and collapsing of capillary lumens, fibrinoid necrosis of afferent arterioles, intimal hyperplasia, and microthrombi. These pathological features are similar to those detected in kidneys of patients with thrombotic microangiopathy (TMA) after allo-HSCT. We previously showed that activation of the complement system plays a role in GVHD-induced tissue injury in mice. Here we report the presence of complement activation products in the kidney specimens of mice after BMT. We also report that complement deficiency reduced the extent and severity of post-BMT glomerular damage in mice. We conclude that BMT in mice is associated with glomerular injury and tubulointerstitial nephritis, and that kidney damage is at least partially mediated by activation of the complement system.

Vascular Smooth Muscle Cell Plasticity and Autophagy in Dissecting Aortic Aneurysms.

Objective- Recent studies suggested the occurrence of phenotypic switching of vascular smooth muscle cells (VSMCs) during the development of aortic aneurysm (AA). However, lineage-tracing studies are still lacking, and the behavior of VSMCs during the formation of dissecting AA is poorly understood. Approach and Results- We used multicolor lineage tracing of VSMCs to track their fate after injury in murine models of Ang II (angiotensin II)-induced dissecting AA. We also addressed the direct impact of autophagy on the response of VSMCs to AA dissection. Finally, we studied the relevance of these processes to human AAs. Here, we show that a subset of medial VSMCs undergoes clonal expansion and that VSMC outgrowths are observed in the adventitia and borders of the false channel during Ang II-induced development of dissecting AA. The clonally expanded VSMCs undergo phenotypic switching with downregulation of VSMC differentiation markers and upregulation of phagocytic markers, indicative of functional changes. In particular, autophagy and endoplasmic reticulum stress responses are activated in the injured VSMCs. Loss of autophagy in VSMCs through deletion of autophagy protein 5 gene ( Atg5) increases the susceptibility of VSMCs to death, enhances endoplasmic reticulum stress activation, and promotes IRE (inositol-requiring enzyme) 1α-dependent VSMC inflammation. These alterations culminate in increased severity of aortic disease and higher incidence of fatal AA dissection in mice with VSMC-restricted deletion of Atg5. We also report increased expression of autophagy and endoplasmic reticulum stress markers in VSMCs of human dissecting AAs. Conclusions- VSMCs undergo clonal expansion and phenotypic switching in Ang II-induced dissecting AAs in mice. We also identify a critical role for autophagy in regulating VSMC death and endoplasmic reticulum stress-dependent inflammation with important consequences for aortic wall homeostasis and repair.

Mitochondrial DNA-Induced Inflammatory Responses and Lung Injury in Thermal Injury Murine Model: Protective Effect of Cyclosporine-A.

Burn trauma is generally associated with profound inflammation and organ injuries, especially the lung. Damage-associated molecular patterns (DAMPs), such as mitochondrial DNA (mtDNA), released after tissue injuries, play a crucial role in the development of the inflammation. The aim of our study was to investigate the protective profiles of cyclosporine-A (CsA) in murine models with thermal injury. We studied 24 C57BL/6 mice which were randomly subjected to four groups: a sham-operation group (SO group, n = 6), an experiment group (a full-thickness thermal injury covered 30% of the TBSA, n = 6), a low-CsA group (injection of 2.5 mg/kg of CsA 15 min before the thermal injury, n = 6) and a high-CsA group (injection of 25 mg/kg of CsA 15 min before the thermal injury, n = 6). Systemic inflammatory mediators and plasma mtDNA were measured while lung injury was evaluated pathologically and cytosolic cytochrome c and mtDNA were detected. Noticeable increases in concentration of mtDNA and inflammatory mediators were obtained in the experiment group and two CsA groups comparing with the SO group (P < .05). There were significant decreases in the concentrations of mtDNA and inflammatory mediators with increasing doses of CsA (P < .05). Similarly, severity of lung injury was mitigated with increasing doses of CsA. Meanwhile, CsA also attenuated oxidative stress and release of cytochrome c and mtDNA in the lung tissue on a dose-dependent manner (P < .05). Our results suggested mtDNA contributes to the development of thermal injury-induced inflammation and lung injury. CsA might exert dual protective effects, reducing the release of mtDNA and limiting the mtDNA-induced mitochondrial dysfunction in the lung, on the thermal injury-induced acute lung injury.

Histone Methylation Directs Myeloid TLR4 Expression and Regulates Wound Healing following Cutaneous Tissue Injury.

Myeloid cells are critical for orchestrating regulated inflammation during wound healing. TLRs, particularly TLR4, and its downstream-signaling MyD88 pathway play an important role in regulating myeloid-mediated inflammation. Because an initial inflammatory phase is vital for tissue repair, we investigated the role of TLR4-regulated, myeloid-mediated inflammation in wound healing. In a cutaneous tissue injury murine model, we found that TLR4 expression is dynamic in wound myeloid cells during the course of normal wound healing. We identified that changes in myeloid TLR4 during tissue repair correlated with increased expression of the histone methyltransferase, mixed-lineage leukemia 1 (MLL1), which specifically trimethylates the histone 3 lysine 4 (H3K4me3) position of the TLR4 promoter. Furthermore, we used a myeloid-specific Mll1 knockout (Mll1f/fLyz2Cre+ ) to determine MLL1 drives Tlr4 expression during wound healing. To understand the critical role of myeloid-specific TLR4 signaling, we used mice deficient in Tlr4 (Tlr4-/- ), Myd88 (Myd88 -/-), and myeloid-specific Tlr4 (Tlr4f/fLyz2Cre+) to demonstrate delayed wound healing at early time points postinjury. Furthermore, in vivo wound myeloid cells isolated from Tlr4-/- and Myd88 -/- wounds demonstrated decreased inflammatory cytokine production. Importantly, adoptive transfer of monocyte/macrophages from wild-type mice trafficked to wounds with restoration of normal healing and myeloid cell function in Tlr4-deficient mice. These results define a role for myeloid-specific, MyD88-dependent TLR4 signaling in the inflammatory response following cutaneous tissue injury and suggest that MLL1 regulates TLR4 expression in wound myeloid cells.

Fish oil protects the liver from parenteral nutrition-induced injury via GPR120-mediated PPARγ signaling

Intravenous fish oil lipid emulsions (FOLE) can prevent parenteral nutrition (PN)-induced liver injury in murine models and reverse PN-induced cholestasis in pediatric patients. However, the mechanisms by which fish oil protects the liver are incompletely characterized. Fish oil is rich in omega-3 fatty acids, which are ligands for the G-protein coupled receptor 120 (GPR120), expressed on hepatic Kupffer cells. This study tested the hypothesis that FOLE protects the liver from PN-induced injury through GPR120 signaling. Utilizing a previously described murine model of PN-induced liver injury in which mice develop steatosis in response to an oral parenteral nutrition diet, FOLE was able to preserve normal hepatic architecture in wild type mice, but not in congenic GPR120 knockout (gpr120−/−) mice. To further characterize the requirement of intact GPR120 for FOLE-mediated hepatic protection, gene expression profiles of key regulators of fat metabolism were measured. PPARγ was identified as a gene that is up-regulated by the PN diet and normalized with the addition of FOLE in wild type, but not in gpr120−/− mice. This was confirmed at the protein expression level. A PPARγ expression array further identified CD36 and SCD1, both down-stream effectors of PPARγ, to be up-regulated in PN-fed wild type mice yet normalized upon FOLE administration in wild type but not in gpr120−/− mice. Together, these results suggest that FOLE protects the liver, in part, through activation of GPR120 and the downstream effectors PPARγ and CD36. Identification of key genetic determinants of FOLE-mediated hepatic protection may provide targets for small molecule-based hepatic protection strategies.

PECAM/eGFP transgenic mice for monitoring of angiogenesis in health and disease

For the monitoring of vascular growth as well as adaptive or therapeutic (re)vascularization endothelial-specific reporter mouse models are valuable tools. However, currently available mouse models have limitations, because not all endothelial cells express the reporter in all developmental stages. We have generated PECAM/eGFP embryonic stem (ES) cell and mouse lines where the reporter gene labels PECAM+ endothelial cells and vessels with high specificity. Native eGFP expression and PECAM staining were highly co-localized in vessels of various organs at embryonic stages E9.5, E15.5 and in adult mice. Expression was found in large and small arteries, capillaries and in veins but not in lymphatic vessels. Also in the bone marrow arteries and sinusoidal vessel were labeled, moreover, we could detect eGFP in some CD45+ hematopoietic cells. We also demonstrate that this labeling is very useful to monitor sprouting in an aortic ring assay as well as vascular remodeling in a murine injury model of myocardial infarction. Thus, PECAM/eGFP transgenic ES cells and mice greatly facilitate the monitoring and quantification of endothelial cells ex vivo and in vivo during development and injury.

Coagonist of glucagon-like peptide-1 and glucagon receptors ameliorates kidney injury in murine models of obesity and diabetes mellitus.

AIMTo investigate the role of glucagon-like peptide-1 (GLP-1)/glucagon receptors coagonist on renal dysfunction associated with diabetes and obesity.METHODSChronic high-fat diet fed C57BL/6J mice, streptozotocin-treated high-fat diet fed C57BL/6J mice and diabetic C57BLKS/J db/db mice were used as models of diabetes-induced renal dysfunction. The streptozotocin-treated high-fat diet fed mice and db/db mice were treated with the GLP-1 and glucagon receptors coagonist (Aib2 C24 Chimera2, 150 μg/kg, sc) for twelve weeks, while in chronic high-fat diet fed mice, coagonist (Aib2 C24 Chimera2, 150 μg/kg, sc) treatment was continued for forty weeks. Kidney function, histology, fibrosis, inflammation, and plasma biochemistry were assessed at the end of the treatment.RESULTSCoagonist treatment decreased body weight, plasma lipids, insulin resistance, creatinine, blood urea nitrogen, urinary albumin excretion rate and renal lipids. In kidney, expression of lipogenic genes (SREBP-1C, FAS, and SCD-1) was decreased, and expression of genes involved in β-oxidation (CPT-1 and PPAR-α) was increased due to coagonist treatment. In plasma, coagonist treatment increased adiponectin and FGF21 and decreased IL-6 and TNF-α. Coagonist treatment reduced expression of inflammatory (TNF-α, MCP-1, and MMP-9) and pro-fibrotic (TGF-β, COL1A1, and α-SMA) genes and also improved histological derangement in renal tissue.CONCLUSIONCoagonist of GLP-1 and glucagon receptors alleviated diabetes and obesity-induced renal dysfunction by reducing glucose intolerance, obesity, and hyperlipidemia.