Copper-Binding Domain Variation in a Novel Murine Lysyl Oxidase Model Produces Structurally Inferior Aortic Elastic Fibers Whose Failure Is Modified by Age, Sex, and Blood Pressure.

Lysyl oxidase (LOX) is a copper-binding enzyme that cross-links elastin and collagen. The dominant LOX variation contributes to familial thoracic aortic aneurysm. Previously reported murine Lox mutants had a mild phenotype and did not dilate without drug-induced provocation. Here, we present a new, more severe mutant, Loxb2b370.2Clo (c.G854T; p.Cys285Phe), whose mutation falls just N-terminal to the copper-binding domain. Unlike the other mutants, the C285F Lox protein was stably produced/secreted, and male C57Bl/6J Lox+/C285F mice exhibit increased systolic blood pressure (BP; p < 0.05) and reduced caliber aortas (p < 0.01 at 100mmHg) at 3 months that independently dilate by 6 months (p < 0.0001). Multimodal imaging reveals markedly irregular elastic sheets in the mutant (p = 2.8 × 10−8 for breaks by histology) that become increasingly disrupted with age (p < 0.05) and breeding into a high BP background (p = 6.8 × 10−4). Aortic dilation was amplified in males vs. females (p < 0.0001 at 100mmHg) and ameliorated by castration. The transcriptome of young Lox mutants showed alteration in dexamethasone (p = 9.83 × 10−30) and TGFß-responsive genes (p = 7.42 × 10−29), and aortas from older C57Bl/6J Lox+/C285F mice showed both enhanced susceptibility to elastase (p < 0.01 by ANOVA) and increased deposition of aggrecan (p < 0.05). These findings suggest that the secreted Lox+/C285F mutants produce dysfunctional elastic fibers that show increased susceptibility to proteolytic damage. Over time, the progressive weakening of the connective tissue, modified by sex and blood pressure, leads to worsening aortic disease.

Inhibition of NOX1 Mitigates Blood Pressure Increases in Elastin Insufficiency.

Elastin (ELN) insufficiency leads to the cardiovascular hallmarks of the contiguous gene deletion disorder, Williams-Beuren syndrome, including hypertension and vascular stiffness. Previous studies showed that Williams-Beuren syndrome deletions, which extended to include the NCF1 gene, were associated with lower blood pressure (BP) and reduced vascular stiffness. NCF1 encodes for p47phox, the regulatory component of the NOX1 NADPH oxidase complex that generates reactive oxygen species (ROS) in the vascular wall. Dihydroethidium and 8-hydroxyguanosine staining of mouse aortas confirmed that Eln heterozygotes (Eln+/- ) had greater ROS levels than the wild-types (Eln+/+ ), a finding that was negated in vessels cultured without hemodynamic stressors. To analyze the Nox effect on ELN insufficiency, we used both genetic and chemical manipulations. Both Ncf1 haploinsufficiency (Ncf1+/- ) and Nox1 insufficiency (Nox1-/y ) decreased oxidative stress and systolic BP in Eln+/- without modifying vascular structure. Chronic treatment with apocynin, a p47phox inhibitor, lowered systolic BP in Eln+/- , but had no impact on Eln+/+ controls. In vivo dosing with phenylephrine (PE) produced an augmented BP response in Eln+/- relative to Eln+/+ , and genetic modifications or drug-based interventions that lower Nox1 expression reduced the hypercontractile response to PE in Eln+/- mice to Eln+/+ levels. These results indicate that the mechanical and structural differences caused by ELN insufficiency leading to oscillatory flow can perpetuate oxidative stress conditions, which are linked to hypertension, and that by lowering the Nox1-mediated capacity for vascular ROS production, BP differences can be normalized.

Bacillus anthracis edema toxin inhibits hypoxic pulmonary vasoconstriction via edema factor and cAMP-mediated mechanisms in isolated perfused rat lungs.

Bacillus anthracis edema toxin (ET) inhibited lethal toxin-stimulated pulmonary artery pressure (Ppa) and increased lung cAMP levels in our previous study. We therefore examined whether ET inhibits hypoxic pulmonary vasoconstriction (HPV). Following baseline hypoxic measures in isolated perfused lungs from healthy rats, compared with diluent, ET perfusion reduced maximal Ppa increases (mean ± SE percentage of maximal Ppa increase with baseline hypoxia) during 6-min hypoxic periods (FIO2 = 0%) at 120 min (16 ± 6% vs. 51 ± 6%, P = 0.004) and 180 min (11.4% vs. 55 ± 6%, P = 0.01). Protective antigen-mAb (PA-mAb) and adefovir inhibit host cell edema factor uptake and cAMP production, respectively. In lungs perfused with ET following baseline measures, compared with placebo, PA-mAb treatment increased Ppa during hypoxia at 120 and 180 min (56 ± 6% vs. 10 ± 4% and 72 ± 12% vs. 12 ± 3%, respectively, P ≤ 0.01) as did adefovir (84 ± 10% vs. 16.8% and 123 ± 21% vs. 26 ± 11%, respectively, P ≤ 0.01). Compared with diluent, lung perfusion with ET for 180 min reduced the slope of the relationships between Ppa and increasing concentrations of endothelin-1 (ET-1) (21.12 ± 2.96 vs. 3.00 ± 0.76 × 108 cmH2O/M, P < 0.0001) and U46619, a thromboxane A2 analogue (7.15 ± 1.01 vs. 3.74 ± 0.31 × 107 cmH2O/M, P = 0.05) added to perfusate. In lungs isolated from rats after 15 h of in vivo infusions with either diluent, ET alone, or ET with PA-mAb, compared with diluent, the maximal Ppa during hypoxia and the slope of the relationship between change in Ppa and ET-1 concentration added to the perfusate were reduced in lungs from animals challenged with ET alone (P ≤ 0.004) but not with ET and PA-mAb together (P ≥ 0.73). Inhibition of HPV by ET could aggravate hypoxia during anthrax pulmonary infection.NEW & NOTEWORTHY The most important findings here are edema toxin's potent adenyl cyclase activity can interfere with hypoxic pulmonary vasoconstriction, an action that could worsen hypoxemia during invasive anthrax infection with lung involvement. These findings, coupled with other studies showing that lethal toxin can disrupt pulmonary vascular integrity, indicate that both toxins can contribute to pulmonary pathophysiology during infection. In combination, these investigations provide a further basis for the use of antitoxin therapies in patients with worsening invasive anthrax disease.

Definitive hematopoietic stem/progenitor cells from human embryonic stem cells through serum/feeder-free organoid-induced differentiation.

BACKGROUND: Ex vivo production of hematopoietic stem/precursor cells (HSPCs) represents a promising versatile approach for blood disorders. METHODS: To derive definitive HSPCs from human embryonic stem cells (ESCs), we differentiated mesodermally specified embryoid bodies (EBs) on gelatin-coated plates in serum/feeder-free conditions. RESULTS: Seven-day EB maturation followed by an 8-day differentiation period on OP9 cells provided the highest number of definitive (CD34+ CD235a-, 69%, p < 0.01) and lowest number of primitive (CD34- CD235a+, 1.55%, p < 0.01) precursor cells along with the highest colony-forming units (149.8 ± 11.6, p < 0.01) in feeder-free conditions. Maximal HSPC fraction (CD34+ CD38- CD45RA- CD49f+ CD90+) was 7.6-8.9% after 10 days of hematopoietic differentiation with 14.5% adult ß-globin expression following RBC differentiation. Myeloid and erythroid colonies were restricted strictly to the CD34+ CD43+ fraction (370.5 ± 65.7, p < 0.001), while the CD34- CD43+ fraction produced only a small number of colonies (21.6 ± 11.9). In addition, we differentiated the CD34+ CD43+ cells towards T-lymphocytes using the OP9/DLL1 co-culture system demonstrating double-positive T cells (CD4+ CD8+) with CD3+ expression displaying a broad T cell receptor (TCR) repertoire. Confocal imaging of organoid-like structures revealed a close association of CD31+ cells with CD34+ and CD43+ cells, suggesting a potential emergence of HSPCs through endothelial to hematopoietic transition. Furthermore, fluorescently labeled organoids exhibited the emergence of spherical non-attached cells from rare progenitors at the border of the organoid center. CONCLUSIONS: In summary, definitive HSPCs can be derived from ESCs through a dynamic cellular process from an organoid-like structure, where erythroid progeny are capable of producing adult hemoglobin and lymphoid progeny shows a diverse TCR repertoire.

Acetylation-mediated remodeling of the nucleolus regulates cellular acetyl-CoA responses.

The metabolite acetyl-coenzyme A (acetyl-CoA) serves as an essential element for a wide range of cellular functions including adenosine triphosphate (ATP) production, lipid synthesis, and protein acetylation. Intracellular acetyl-CoA concentrations are associated with nutrient availability, but the mechanisms by which a cell responds to fluctuations in acetyl-CoA levels remain elusive. Here, we generate a cell system to selectively manipulate the nucleo-cytoplasmic levels of acetyl-CoA using clustered regularly interspaced short palindromic repeat (CRISPR)-mediated gene editing and acetate supplementation of the culture media. Using this system and quantitative omics analyses, we demonstrate that acetyl-CoA depletion alters the integrity of the nucleolus, impairing ribosomal RNA synthesis and evoking the ribosomal protein-dependent activation of p53. This nucleolar remodeling appears to be mediated through the class IIa histone deacetylases (HDACs). Our findings highlight acetylation-mediated control of the nucleolus as an important hub linking acetyl-CoA fluctuations to cellular stress responses.

Tissue-Resident PDGFRα+ Progenitor Cells Contribute to Fibrosis versus Healing in a Context- and Spatiotemporally Dependent Manner.

PDGFRα+ mesenchymal progenitor cells are associated with pathological fibro-adipogenic processes. Conversely, a beneficial role for these cells during homeostasis or in response to revascularization and regeneration stimuli is suggested, but remains to be defined. We studied the molecular profile and function of PDGFRα+ cells in order to understand the mechanisms underlying their role in fibrosis versus regeneration. We show that PDGFRα+ cells are essential for tissue revascularization and restructuring through injury-stimulated remodeling of stromal and vascular components, context-dependent clonal expansion, and ultimate removal of pro-fibrotic PDGFRα+-derived cells. Tissue ischemia modulates the PDGFRα+ phenotype toward cells capable of remodeling the extracellular matrix and inducing cell-cell and cell-matrix adhesion, likely favoring tissue repair. Conversely, pathological healing occurs if PDGFRα+-derived cells persist as terminally differentiated mesenchymal cells. These studies support a context-dependent "yin-yang" biology of tissue-resident mesenchymal progenitor cells, which possess an innate ability to limit injury expansion while also promoting fibrosis in an unfavorable environment.

Rapamycin is highly effective in murine models of immune-mediated bone marrow failure.

Acquired aplastic anemia, the prototypical bone marrow failure disease, is characterized by pancytopenia and marrow hypoplasia. Most aplastic anemia patients respond to immunosuppressive therapy, usually with anti-thymocyte globulin and cyclosporine, but some relapse on cyclosporine withdrawal or require long-term administration of cyclosporine to maintain blood counts. In this study, we tested efficacy of rapamycin as a new or alternative treatment in mouse models of immune-mediated bone marrow failure. Rapamycin ameliorated pancytopenia, improved bone marrow cellularity, and extended animal survival in a manner comparable to the standard dose of cyclosporine. Rapamycin effectively reduced Th1 inflammatory cytokines interferon-γ and tumor necrosis factor-α, increased the Th2 cytokine interleukin-10, stimulated expansion of functional regulatory T cells, eliminated effector CD8+ T cells (notably T cells specific to target cells bearing minor histocompatibility antigen H60), and preserved hematopoietic stem and progenitor cells. Rapamycin, but not cyclosporine, reduced the proportion of memory and effector T cells and maintained a pool of naïve T cells. Cyclosporine increased cytoplasmic nuclear factor of activated T-cells-1 following T-cell receptor stimulation, whereas rapamycin suppressed phosphorylation of two key signaling molecules in the mammalian target of rapamycin pathway, S6 kinase and protein kinase B. In summary, rapamycin was an effective therapy in mouse models of immune-mediated bone marrow failure, acting through different mechanisms to cyclosporine. Its specific expansion of regulatory T cells and elimination of clonogenic CD8+ effectors support its potential clinical utility in the treatment of aplastic anemia.

A fluorescence-based imaging method to measure in vitro and in vivo mitophagy using mt-Keima.

Mitophagy is a cellular process that selectively removes damaged, old or dysfunctional mitochondria. Defective mitophagy is thought to contribute to normal aging and to various neurodegenerative and cardiovascular diseases. Previous methods used to detect mitophagy in vivo were cumbersome, insensitive and difficult to quantify. We created a transgenic mouse model that expresses the pH-dependent fluorescent protein mt-Keima in order to more readily assess mitophagy. Keima is a pH-sensitive, dual-excitation ratiometric fluorescent protein that also exhibits resistance to lysosomal proteases. At the physiological pH of the mitochondria (pH 8.0), the shorter-wavelength excitation predominates. Within the acidic lysosome (pH 4.5) after mitophagy, mt-Keima undergoes a gradual shift to longer-wavelength excitation. In this protocol, we describe how to monitor mitophagic flux in living cells over an 18-h time frame, as well as how to quantify mitophagy using the mt-Keima probe. This protocol also describes how to use confocal microscopy to visualize mitophagy in living tissues obtained from mt-Keima transgenic mice. With this protocol, the mt-Keima probe can reliably be imaged within the first 60 min after tissue collection. We also describe how to apply mt-Keima with stimulated emission depletion (STED) microscopy, which can potentially provide substantially higher-resolution images. Typically, the approximate time frame for time-lapse fluorescence imaging of mt-Keima is 20 h for living cells. For confocal analysis of tissue from an mt-Keima mouse, the whole procedure generally takes no longer than 60 min, and the STED imaging usually takes <2 h.

Direct visualization of the arterial wall water permeability barrier using CARS microscopy.

The artery wall is equipped with a water permeation barrier that allows blood to flow at high pressure without significant water leak. The precise location of this barrier is unknown despite its importance in vascular function and its contribution to many vascular complications when it is compromised. Herein we map the water permeability in intact arteries, using coherent anti-Stokes Raman scattering (CARS) microscopy and isotopic perfusion experiments. Generation of the CARS signal is optimized for water imaging with broadband excitation. We identify the water permeation barrier as the endothelial basolateral membrane and show that the apical membrane is highly permeable. This is confirmed by the distribution of the AQP1 water channel within endothelial membranes. These results indicate that arterial pressure equilibrates within the endothelium and is transmitted to the supporting basement membrane and internal elastic lamina macromolecules with minimal deformation of the sensitive endothelial cell. Disruption of this pressure transmission could contribute to endothelial cell dysfunction in various pathologies.

In Vivo Cell Tracking Using Two-Photon Microscopy.

Recently we have explored and developed approaches imaging using confocal/two-photon microscopy, which enables simultaneous high-resolution assessment of specifically fluorescently marked cells in conjunction with structural components of the tissues visualized via harmonic generated signals. This approach uses commercially available confocal and two-photon laser microscope and automated user-interactive image analysis methods based on commercially available software packages allowing easy implementation in usual microscopy facilities.

PPARγ antagonist attenuates mouse immune-mediated bone marrow failure by inhibition of T cell function.

Acquired aplastic anemia is an immune-mediated disease, in which T cells target hematopoietic cells; at presentation, the bone marrow is replaced by fat. It was reported that bone marrow adipocytes were negative regulators of hematopoietic microenvironment. To examine the role of adipocytes in bone marrow failure, we investigated peroxisomal proliferator-activated receptor gamma, a key transcription factor in adipogenesis, utilizing an antagonist of this factor called bisphenol-A-diglycidyl-ether. While bisphenol-A-diglycidyl-ether inhibited adipogenesis as expected, it also suppressed T cell infiltration of bone marrow, reduced plasma inflammatory cytokines, decreased expression of multiple inflammasome genes, and ameliorated marrow failure. In vitro, bisphenol-A-diglycidyl-ether suppressed activation and proliferation, and reduced phospholipase C gamma 1 and nuclear factor of activated T-cells 1 expression, as well as inhibiting calcium flux in T cells. The in vivo effect of bisphenol-A-diglycidyl-ether on T cells was confirmed in a second immune-mediated bone marrow failure model, using different strains and non-major histocompatibility antigen mismatched: bisphenol-A-diglycidyl-ether ameliorated marrow failure by inhibition of T cell infiltration of bone marrow. Our data indicate that peroxisomal proliferator-activated receptor gamma antagonists may attenuate murine immune-mediated bone marrow failure, at least in part, by suppression of T cell activation, which might hold implications in the application of peroxisomal proliferator-activated receptor gamma antagonists in immune-mediated pathophysiologies, both in the laboratory and in the clinic. Genetically "fatless" mice developed bone marrow failure with accumulation of marrow adipocytes in our model, even in the absence of body fat, suggesting different mechanisms of systematic and marrow adipogenesis and physiologic versus pathophysiologic fat accumulation.

Measuring In Vivo Mitophagy.

Alterations in mitophagy have been increasingly linked to aging and age-related diseases. There are, however, no convenient methods to analyze mitophagy in vivo. Here, we describe a transgenic mouse model in which we expressed a mitochondrial-targeted form of the fluorescent reporter Keima (mt-Keima). Keima is a coral-derived protein that exhibits both pH-dependent excitation and resistance to lysosomal proteases. Comparison of a wide range of primary cells and tissues generated from the mt-Keima mouse revealed significant variations in basal mitophagy. In addition, we have employed the mt-Keima mice to analyze how mitophagy is altered by conditions including diet, oxygen availability, Huntingtin transgene expression, the absence of macroautophagy (ATG5 or ATG7 expression), an increase in mitochondrial mutational load, the presence of metastatic tumors, and normal aging. The ability to assess mitophagy under a host of varying environmental and genetic perturbations suggests that the mt-Keima mouse should be a valuable resource.

Mitochondrial reticulum for cellular energy distribution in muscle.

Intracellular energy distribution has attracted much interest and has been proposed to occur in skeletal muscle via metabolite-facilitated diffusion; however, genetic evidence suggests that facilitated diffusion is not critical for normal function. We hypothesized that mitochondrial structure minimizes metabolite diffusion distances in skeletal muscle. Here we demonstrate a mitochondrial reticulum providing a conductive pathway for energy distribution, in the form of the proton-motive force, throughout the mouse skeletal muscle cell. Within this reticulum, we find proteins associated with mitochondrial proton-motive force production preferentially in the cell periphery and proteins that use the proton-motive force for ATP production in the cell interior near contractile and transport ATPases. Furthermore, we show a rapid, coordinated depolarization of the membrane potential component of the proton-motive force throughout the cell in response to spatially controlled uncoupling of the cell interior. We propose that membrane potential conduction via the mitochondrial reticulum is the dominant pathway for skeletal muscle energy distribution.

Cooperative interactions of LPPR family members in membrane localization and alteration of cellular morphology.

The lipid phosphate phosphatase-related proteins (LPPRs), also known as plasticity-related genes (PRGs), are classified as a new brain-enriched subclass of the lipid phosphate phosphatase (LPP) superfamily. They induce membrane protrusions, neurite outgrowth or dendritic spine formation in cell lines and primary neurons. However, the exact roles of LPPRs and the mechanisms underlying their effects are not certain. Here, we present the results of a large-scale proteome analysis to determine LPPR1-interacting proteins using co-immunoprecipitation coupled to mass spectrometry. We identified putative LPPR1-binding proteins involved in various biological processes. Most interestingly, we identified the interaction of LPPR1 with its family member LPPR3, LPPR4 and LPPR5. Their interactions were characterized by co-immunoprecipitation and colocalization analysis using confocal and super-resolution microscopy. Moreover, co-expressing two LPPR members mutually elevated their protein levels, facilitated their plasma membrane localization and resulted in an increased induction of membrane protrusions as well as the phosphorylation of S6 ribosomal protein. Taken together, we revealed a new functional cooperation between LPPR family members and discovered for the first time that LPPRs likely exert their function through forming complex with its family members.

Increased plasma cholesterol esterification by LCAT reduces diet-induced atherosclerosis in SR-BI knockout mice.

LCAT, a plasma enzyme that esterifies cholesterol, has been proposed to play an antiatherogenic role, but animal and epidemiologic studies have yielded conflicting results. To gain insight into LCAT and the role of free cholesterol (FC) in atherosclerosis, we examined the effect of LCAT over- and underexpression in diet-induced atherosclerosis in scavenger receptor class B member I-deficient [Scarab(-/-)] mice, which have a secondary defect in cholesterol esterification. Scarab(-/-)×LCAT-null [Lcat(-/-)] mice had a decrease in HDL-cholesterol and a high plasma ratio of FC/total cholesterol (TC) (0.88 ± 0.033) and a marked increase in VLDL-cholesterol (VLDL-C) on a high-fat diet. Scarab(-/-)×LCAT-transgenic (Tg) mice had lower levels of VLDL-C and a normal plasma FC/TC ratio (0.28 ± 0.005). Plasma from Scarab(-/-)×LCAT-Tg mice also showed an increase in cholesterol esterification during in vitro cholesterol efflux, but increased esterification did not appear to affect the overall rate of cholesterol efflux or hepatic uptake of cholesterol. Scarab(-/-)×LCAT-Tg mice also displayed a 51% decrease in aortic sinus atherosclerosis compared with Scarab(-/-) mice (P < 0.05). In summary, we demonstrate that increased cholesterol esterification by LCAT is atheroprotective, most likely through its ability to increase HDL levels and decrease pro-atherogenic apoB-containing lipoprotein particles.

The Human ABCG1 Transporter Mobilizes Plasma Membrane and Late Endosomal Non-Sphingomyelin-Associated-Cholesterol for Efflux and Esterification.

We have previously shown that GFP-tagged human ABCG1 on the plasma membrane (PM) and in late endosomes (LE) mobilizes sterol on both sides of the membrane lipid bilayer, thereby increasing cellular cholesterol efflux to lipid surfaces. In the present study, we examined ABCG1-induced changes in membrane cholesterol distribution, organization, and mobility. ABCG1-GFP expression increased the amount of mobile, non-sphingomyelin(SM)-associated cholesterol at the PM and LE, but not the amount of SM-associated-cholesterol or SM. ABCG1-mobilized non-SM-associated-cholesterol rapidly cycled between the PM and LE and effluxed from the PM to extracellular acceptors, or, relocated to intracellular sites of esterification. ABCG1 increased detergent-soluble pools of PM and LE cholesterol, generated detergent-resistant, non-SM-associated PM cholesterol, and increased resistance to both amphotericin B-induced (cholesterol-mediated) and lysenin-induced (SM-mediated) cytolysis, consistent with altered organization of both PM cholesterol and SM. ABCG1 itself resided in detergent-soluble membrane domains. We propose that PM and LE ABCG1 residing at the phase boundary between ordered (Lo) and disordered (Ld) membrane lipid domains alters SM and cholesterol organization thereby increasing cholesterol flux between Lo and Ld, and hence, the amount of cholesterol available for removal by acceptors on either side of the membrane bilayer for either efflux or esterification.

Cellular Localization and Trafficking of the Human ABCG1 Transporter.

We have developed a suitable heterologous cell expression system to study the localization, trafficking, and site(s) of function of the human ABCG1 transporter. Increased plasma membrane (PM) and late endosomal (LE) cholesterol generated by ABCG1 was removed by lipoproteins and liposomes, but not apoA-I. Delivery of ABCG1 to the PM and LE was required for ABCG1-mediated cellular cholesterol efflux. ABCG1 LEs frequently contacted the PM, providing a collisional mechanism for transfer of ABCG1-mobilized cholesterol, similar to ABCG1-mediated PM cholesterol efflux to lipoproteins. ABCG1-mobilized LE cholesterol also trafficked to the PM by a non-vesicular pathway. Transfer of ABCG1-mobilized cholesterol from the cytoplasmic face of LEs to the PM and concomitant removal of cholesterol from the outer leaflet of the PM bilayer by extracellular acceptors suggests that ABCG1 mobilizes cholesterol on both sides of the lipid bilayer for removal by acceptors. ABCG1 increased uptake of HDL into LEs, consistent with a potential ABCG1-mediated cholesterol efflux pathway involving HDL resecretion. Thus, ABCG1 at the PM mobilizes PM cholesterol and ABCG1 in LE/LYS generates mobile pools of cholesterol that can traffic by both vesicular and non-vesicular pathways to the PM where it can also be transferred to extracellular acceptors with a lipid surface.

In vivo clonal tracking of hematopoietic stem and progenitor cells marked by five fluorescent proteins using confocal and multiphoton microscopy.

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and temporal resolution to study in vivo hematopoiesis using the murine bone marrow transplant experimental model. Genetic combinatorial marking using lentiviral vectors encoding fluorescent proteins (FPs) enabled cell fate mapping through advanced microscopy imaging. Vectors encoding five different FPs: Cerulean, EGFP, Venus, tdTomato, and mCherry were used to concurrently transduce HSPCs, creating a diverse palette of color marked cells. Imaging using confocal/two-photon hybrid microscopy enables simultaneous high resolution assessment of uniquely marked cells and their progeny in conjunction with structural components of the tissues. Volumetric analyses over large areas reveal that spectrally coded HSPC-derived cells can be detected non-invasively in various intact tissues, including the bone marrow (BM), for extensive periods of time following transplantation. Live studies combining video-rate multiphoton and confocal time-lapse imaging in 4D demonstrate the possibility of dynamic cellular and clonal tracking in a quantitative manner.

Nuclear localization of vascular endothelial growth factor-D and regulation of c-Myc-dependent transcripts in human lung fibroblasts.

Lymphangiogenesis and angiogenesis are processes that are, in part, regulated by vascular endothelial growth factor (VEGF)-D. The formation of lymphatic structures has been implicated in multiple lung diseases, including pulmonary fibrosis. VEGF-D is a secreted protein produced by fibroblasts and macrophages, which induces lymphangiogenesis by signaling via VEGF receptor-3, and angiogenesis through VEGF receptor-2. VEGF-D contains a central VEGF homology domain, which is the biologically active domain, with flanking N- and C-terminal propeptides. Full-length VEGF-D (∼ 50 kD) is proteolytically processed in the extracellular space, to generate VEGF homology domain that contains the VEGF-D receptor-binding sites. Here, we report that, independent of its cell surface receptors, full-length VEGF-D accumulated in nuclei of fibroblasts, and that this process appears to increase with cell density. In nuclei, full-length VEGF-D associated with RNA polymerase II and c-Myc. In cells depleted of VEGF-D, the transcriptionally regulated genes appear to be modulated by c-Myc. These findings have potential clinical implications, as VEGF-D was found in fibroblast nuclei in idiopathic pulmonary fibrosis, a disease characterized by fibroblast proliferation. These findings are consistent with actions of full-length VEGF-D in cellular homeostasis in health and disease, independent of its receptors.