Intrinsically accurate sensing with an optomechanical accelerometer.

We demonstrate a microfabricated optomechanical accelerometer that is capable of percent-level accuracy without external calibration. To achieve this capability, we use a mechanical model of the device behavior that can be characterized by the thermal noise response along with an optical frequency comb readout method that enables high sensitivity, high bandwidth, high dynamic range, and SI-traceable displacement measurements. The resulting intrinsic accuracy was evaluated over a wide frequency range by comparing to a primary vibration calibration system and local gravity. The average agreement was found to be 2.1 % for the calibration system between 0.1 kHz and 15 kHz and better than 0.2 % for the static acceleration. This capability has the potential to replace costly external calibrations and improve the accuracy of inertial guidance systems and remotely deployed accelerometers. Due to the fundamental nature of the intrinsic accuracy approach, it could be extended to other optomechanical transducers, including force and pressure sensors.

Identification of an Altered Matrix Signature in Kidney Aging and Disease.

BACKGROUND: Accumulation of extracellular matrix in organs and tissues is a feature of both aging and disease. In the kidney, glomerulosclerosis and tubulointerstitial fibrosis accompany the decline in function, which current therapies cannot address, leading to organ failure. Although histologic and ultrastructural patterns of excess matrix form the basis of human disease classifications, a comprehensive molecular resolution of abnormal matrix is lacking. METHODS: Using mass spectrometry-based proteomics, we resolved matrix composition over age in mouse models of kidney disease. We compared the changes in mice with a global characterization of human kidneymatrix during aging and to existing kidney disease datasets to identify common molecular features. RESULTS: Ultrastructural changes in basement membranes are associated with altered cell adhesion and metabolic processes and with distinct matrix proteomes during aging and kidney disease progression in mice. Within the altered matrix, basement membrane components (laminins, type IV collagen, type XVIII collagen) were reduced and interstitial matrix proteins (collagens I, III, VI, and XV; fibrinogens; and nephronectin) were increased, a pattern also seen in human kidney aging. Indeed, this signature of matrix proteins was consistently modulated across all age and disease comparisons, and the increase in interstitial matrix was also observed in human kidney disease datasets. CONCLUSIONS: This study provides deep molecular resolution of matrix accumulation in kidney aging and disease, and identifies a common signature of proteins that provides insight into mechanisms of response to kidney injury and repair.

Mechanisms and cell lineages in lymphatic vascular development.

Lymphatic vessels have critical roles in both health and disease and their study is a rapidly evolving area of vascular biology. The consensus on how the first lymphatic vessels arise in the developing embryo has recently shifted. Originally, they were thought to solely derive by sprouting from veins. Since then, several studies have uncovered novel cellular mechanisms and a diversity of contributing cell lineages in the formation of organ lymphatic vasculature. Here, we review the key mechanisms and cell lineages contributing to lymphatic development, discuss the advantages and limitations of experimental techniques used for their study and highlight remaining knowledge gaps that require urgent attention. Emerging technologies should accelerate our understanding of how lymphatic vessels develop normally and how they contribute to disease.

Near-infrared cavity ring-down spectroscopy measurements of nitrous oxide in the (4200)←(0000) and (5000)←(0000) bands.

Using frequency-agile rapid scanning cavity ring-down spectroscopy, we measured line intensities and line shape parameters of 14N2 16O in air in the (4200)←(0000) and (5000)←(0000) bands near 1.6 µm. The absorption spectra were modeled with multi-spectrum fits of Voigt and speed-dependent Voigt profiles. The measured line intensities and air-broadening parameters exhibit deviations of several percent relative to values provided in HITRAN 2016. Our measured intensities for these two bands have relative combined standard uncertainties of ∼1% which is approximately five times smaller than literature values. Comparison of the present air-broadening and speed-dependent broadening parameters to experimental literature values for other rotation-vibration bands of N2O indicates significant differences in magnitude and J-dependence. For applications requiring high spectral fidelity, these results suggest that the assumption of band-independent line shape parameters is not appropriate.

Air-broadening in near-infrared carbon dioxide line shapes: Quantifying contributions from O2, N2, and Ar.

We measured air broadening in the (30012) ← (00001) carbon dioxide (CO2) band up to J″=50 using frequency-agile rapid scanning cavity ring-down spectroscopy. By using synthetic air samples with varying levels of nitrogen, oxygen, and argon, multi-spectrum fitting allowed for the collisional broadening terms of each major air component to be simultaneously determined in addition to advanced line shape parameters at atmospherically relevant CO2 mixing ratios. These values were compared to broadener-specific line shape parameters from the literature. Fits to measured spectra were also constrained with results from requantized classical molecular dynamic simulations. We show that this approach enables differentiation between narrowing mechanisms in advanced line shape parameters retrieved from experimental spectra of limited signal-to-noise ratio.

Improvement of the spectroscopic parameters of the air- and self-broadened N2O and CO lines for the HITRAN2020 database applications.

This paper outlines the major updates of the line-shape parameters that were performed for the nitrous oxide (N2O) and carbon monoxide (CO) molecules listed in the HITRAN2020 database. We reviewed the collected measurements for the air- and self-broadened N2O and CO spectra to determine proper values for the spectroscopic parameters. Careful comparisons of broadening parameters using the Voigt and speed-dependent Voigt line-shape profiles were performed among various published results for both N2O and CO. Selected data allowed for developing semi-empirical models, which were used to extrapolate/interpolate existing data to update broadening parameters of all the lines of these molecules in the HITRAN database. In addition to the line broadening parameters (and their temperature dependences), the pressure shift values were revised for N2O and CO broadened by air and self for all the bands. The air and self speed-dependence of the broadening parameter for these two molecules were added for every transition as well. Furthermore, we determined the first-order line-mixing parameters using the Exponential Power Gap (EPG) scaling law. These new parameters are now available at HITRAN online.

Beyond a Passive Conduit: Implications of Lymphatic Biology for Kidney Diseases.

The kidney contains a network of lymphatic vessels that clear fluid, small molecules, and cells from the renal interstitium. Through modulating immune responses and via crosstalk with surrounding renal cells, lymphatic vessels have been implicated in the progression and maintenance of kidney disease. In this Review, we provide an overview of the development, structure, and function of lymphatic vessels in the healthy adult kidney. We then highlight the contributions of lymphatic vessels to multiple forms of renal pathology, emphasizing CKD, transplant rejection, and polycystic kidney disease and discuss strategies to target renal lymphatics using genetic and pharmacologic approaches. Overall, we argue the case for lymphatics playing a fundamental role in renal physiology and pathology and treatments modulating these vessels having therapeutic potential across the spectrum of kidney disease.

Free 25-hydroxyvitamin-D concentrations are lower in children with renal transplant compared with chronic kidney disease.

BACKGROUND: Total serum 25-hydroxyvitamin D [25(OH)D] is considered the best marker of vitamin D status and used routinely in clinical practice. However, 25(OH)D is predominantly bound to vitamin D-binding protein (VDBP), and it has been reported that the free-25(OH)D and 25(OH)D loosely bound to albumin fraction correlates better with clinical outcomes. METHODS: We assessed total-25(OH)D, measured free-25(OH)D, and calculated free-25(OH)D and their relationship with VDBP and biomarkers of mineral metabolism in 61 children (22 CKD 2-3, 18 dialysis, and 21 post-transplant). RESULTS: Total-25(OH)D concentrations were comparable across the three groups (p = 0.09), but free- and bioavailable-25(OH)D (free- and albumin-25(OH)D) were significantly lower in the transplant group (both: p = 0.01). Compared to CKD and dialysis patients, the transplant group had significantly higher VDBP concentrations (p = 0.03). In all three groups, total-25(OH)D concentrations were positively associated with measured free-, calculated free-, and bioavailable-25(OH)D. Multivariable regression analysis showed that total-25(OH)D was the only predictor of measured free-25(OH)D concentrations in the dialysis group (ß = 0.9; R2 = 90%). In the transplant group, measured free-25(OH)D concentrations were predicted by both total-25(OH)D and VDBP concentrations (ß = 0.6, - 0.6, respectively; R2 = 80%). Correlations between parathyroid hormone with total-25(OH)D and measured and calculated free-25(OH)D were only observed in the transplant group (all: p < 0.001). CONCLUSIONS: In transplanted patients, VDBP concentrations were significantly higher compared to CKD and dialysis patients, and consequently, free-25(OH)D concentrations were lower, despite a comparable total-25(OH)D concentration. We suggest that free-25(OH)D measures may be required in children with CKD, dialysis, and transplant, with further research required to understand its association with markers of mineral metabolism.

Arterial "inflammaging" drives vascular calcification in children on dialysis.

Children on dialysis have a cardiovascular mortality risk equivalent to older adults in the general population, and rapidly develop medial vascular calcification, an age-associated pathology. We hypothesized that premature vascular ageing contributes to calcification in children with advanced chronic kidney disease (CKD). Vessels from children with Stage 5 CKD with and without dialysis had evidence of increased oxidative DNA damage. The senescence markers p16 and p21 were also increased in vessels from children on dialysis. Treatment of vessel rings ex vivo with calcifying media increased oxidative DNA damage in vessels from children with Stage 5 CKD, but not in those from healthy controls. Vascular smooth muscle cells cultured from children on dialysis exhibited persistent DNA damage, impaired DNA damage repair, and accelerated senescence. Under calcifying conditions vascular smooth muscle cells from children on dialysis showed increased osteogenic differentiation and calcification. These changes correlated with activation of the senescence-associated secretory phenotype (SASP), an inflammatory phenotype characterized by the secretion of proinflammatory cytokines and growth factors. Blockade of ataxia-telangiectasia mutated (ATM)-mediated DNA damage signaling reduced both inflammation and calcification. Clinically, children on dialysis had elevated circulating levels of osteogenic SASP factors that correlated with increased vascular stiffness and coronary artery calcification. These data imply that dysregulated mineral metabolism drives vascular "inflammaging" by promoting oxidative DNA damage, premature senescence, and activation of a pro-inflammatory SASP. Drugs that target DNA damage signaling or eliminate senescent cells may have the potential to prevent vascular calcification in patients with advanced CKD.

Twenty-Five-Fold Reduction in Measurement Uncertainty for a Molecular Line Intensity.

To accurately attribute sources and sinks of molecules like CO_{2}, remote sensing missions require line intensities (S) with relative uncertainties u_{r}(S)<0.1%. However, discrepancies in S of ≈1% are common when comparing different experiments, thus limiting their potential impact. Here we report a cavity ring-down spectroscopy multi-instrument comparison which revealed that the hardware used to digitize analog ring-down signals caused variability in spectral integrals which yield S. Our refined approach improved measurement accuracy 25-fold, resulting in u_{r}(S)=0.06%.

Vangl2, a planar cell polarity molecule, is implicated in irreversible and reversible kidney glomerular injury.

Planar cell polarity (PCP) pathways control the orientation and alignment of epithelial cells within tissues. Van Gogh-like 2 (Vangl2) is a key PCP protein that is required for the normal differentiation of kidney glomeruli and tubules. Vangl2 has also been implicated in modifying the course of acquired glomerular disease, and here, we further explored how Vangl2 impacts on glomerular pathobiology in this context. Targeted genetic deletion of Vangl2 in mouse glomerular epithelial podocytes enhanced the severity of not only irreversible accelerated nephrotoxic nephritis but also lipopolysaccharide-induced reversible glomerular damage. In each proteinuric model, genetic deletion of Vangl2 in podocytes was associated with an increased ratio of active-MMP9 to inactive MMP9, an enzyme involved in tissue remodelling. In addition, by interrogating microarray data from two cohorts of renal patients, we report increased VANGL2 transcript levels in the glomeruli of individuals with focal segmental glomerulosclerosis, suggesting that the molecule may also be involved in certain human glomerular diseases. These observations support the conclusion that Vangl2 modulates glomerular injury, at least in part by acting as a brake on MMP9, a potentially harmful endogenous enzyme. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

In vivo three-dimensional photoacoustic imaging of the renal vasculature in preclinical rodent models.

Noninvasive imaging of the kidney vasculature in preclinical murine models is important for the assessment of renal development, studying diseases and evaluating new therapies but is challenging to achieve using existing imaging modalities. Photoacoustic imaging is a promising new technique that is particularly well suited to visualizing the vasculature and could provide an alternative to existing preclinical imaging methods for studying renal vascular anatomy and function. To investigate this, an all-optical Fabry-Perot-based photoacoustic scanner was used to image the abdominal region of mice. High-resolution three-dimensional, noninvasive, label-free photoacoustic images of the mouse kidney and renal vasculature were acquired in vivo. The scanner was also used to visualize and quantify differences in the vascular architecture of the kidney in vivo due to polycystic kidney disease. This study suggests that photoacoustic imaging could be utilized as a novel preclinical imaging tool for studying the biology of renal disease.

Vascular Endothelial Growth Factor C for Polycystic Kidney Diseases.

Polycystic kidney diseases (PKD) are genetic disorders characterized by progressive epithelial cyst growth leading to destruction of normally functioning renal tissue. Current therapies have focused on the cyst epithelium, and little is known about how the blood and lymphatic microvasculature modulates cystogenesis. Hypomorphic Pkd1(nl/nl) mice were examined, showing that cystogenesis was associated with a disorganized pericystic network of vessels expressing platelet/endothelial cell adhesion molecule 1 and vascular endothelial growth factor receptor 3 (VEGFR3). The major ligand for VEGFR3 is VEGFC, and there were lower levels of Vegfc mRNA within the kidneys during the early stages of cystogenesis in 7-day-old Pkd1(nl/nl) mice. Seven-day-old mice were treated with exogenous VEGFC for 2 weeks on the premise that this would remodel both the VEGFR3(+) pericystic vascular network and larger renal lymphatics that may also affect the severity of PKD. Treatment with VEGFC enhanced VEGFR3 phosphorylation in the kidney, normalized the pattern of the pericystic network of vessels, and widened the large lymphatics in Pkd1(nl/nl) mice. These effects were associated with significant reductions in cystic disease, BUN and serum creatinine levels. Furthermore, VEGFC administration reduced M2 macrophage pericystic infiltrate, which has been implicated in the progression of PKD. VEGFC administration also improved cystic disease in Cys1(cpk/cpk) mice, a model of autosomal recessive PKD, leading to a modest but significant increase in lifespan. Overall, this study highlights VEGFC as a potential new treatment for some aspects of PKD, with the possibility for synergy with current epithelially targeted approaches.

Aging-associated renal disease in mice is fructokinase dependent.

Aging-associated kidney disease is usually considered a degenerative process associated with aging. Recently, it has been shown that animals can produce fructose endogenously, and that this can be a mechanism for causing kidney damage in diabetic nephropathy and in association with recurrent dehydration. We therefore hypothesized that low-level metabolism of endogenous fructose might play a role in aging-associated kidney disease. Wild-type and fructokinase knockout mice were fed a normal diet for 2 yr that had minimal (<5%) fructose content. At the end of 2 yr, wild-type mice showed elevations in systolic blood pressure, mild albuminuria, and glomerular changes with mesangial matrix expansion, variable mesangiolysis, and segmental thrombi. The renal injury was amplified by provision of high-salt diet for 3 wk, as noted by the presence of glomerular hypertrophy, mesangial matrix expansion, and alpha smooth muscle actin expression, and with segmental thrombi. Fructokinase knockout mice were protected from renal injury both at baseline and after high salt intake (3 wk) compared with wild-type mice. This was associated with higher levels of active (phosphorylated serine 1177) endothelial nitric oxide synthase in their kidneys. These studies suggest that aging-associated renal disease might be due to activation of specific metabolic pathways that could theoretically be targeted therapeutically, and raise the hypothesis that aging-associated renal injury may represent a disease process as opposed to normal age-related degeneration.

Loss of endogenous thymosin ß4 accelerates glomerular disease.

Glomerular disease is characterized by morphologic changes in podocyte cells accompanied by inflammation and fibrosis. Thymosin ß4 regulates cell morphology, inflammation, and fibrosis in several organs and administration of exogenous thymosin ß4 improves animal models of unilateral ureteral obstruction and diabetic nephropathy. However, the role of endogenous thymosin ß4 in the kidney is unknown. We demonstrate that thymosin ß4 is expressed prominently in podocytes of developing and adult mouse glomeruli. Global loss of thymosin ß4 did not affect healthy glomeruli, but accelerated the severity of immune-mediated nephrotoxic nephritis with worse renal function, periglomerular inflammation, and fibrosis. Lack of thymosin ß4 in nephrotoxic nephritis led to the redistribution of podocytes from the glomerular tuft toward the Bowman capsule suggesting a role for thymosin ß4 in the migration of these cells. Thymosin ß4 knockdown in cultured podocytes also increased migration in a wound-healing assay, accompanied by F-actin rearrangement and increased RhoA activity. We propose that endogenous thymosin ß4 is a modifier of glomerular injury, likely having a protective role acting as a brake to slow disease progression.

Planar cell polarity genes Celsr1 and Vangl2 are necessary for kidney growth, differentiation, and rostrocaudal patterning.

The mammalian kidney contains nephrons comprising glomeruli and tubules joined to ureteric bud-derived collecting ducts. It has a characteristic bean-like shape, with near-complete rostrocaudal symmetry around the hilum. Here we show that Celsr1, a planar cell polarity (PCP) gene implicated in neural tube morphogenesis, is required for ureteric tree growth in early development and later in gestation prevents tubule overgrowth. We also found an interaction between Celsr1 and Vangl2 (another PCP gene) in ureteric tree growth, most marked in the caudal compartment of the kidneys from compound heterozygous mutant mice with a stunted rump. Furthermore, these genes together are required for the maturation of glomeruli. Interestingly, we demonstrated patients with CELSR1 mutations and spina bifida can have significant renal malformations. Thus, PCP genes are important in mammalian kidney development and have an unexpected role in rostrocaudal patterning during organogenesis.

Coherent cavity-enhanced dual-comb spectroscopy.

Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers or via sophisticated signal processing algorithms, and therefore, long integration times of phase coherent signals are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The dual combs were generated by driving the phase modulators with step-recovery diodes where each comb consisted of > 250 teeth with 203 MHz spacing and spanned > 50 GHz region in the near-infrared. The step-recovery diodes are passive devices that provide low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO2, CO, HDO, and H2O in a single spectral region at a maximum acquisition rate of 150 kHz. Robust, compact, low-cost and widely tunable dual-comb systems could enable a network of distributed multiplexed optical sensors.

Genetic Background is a Key Determinant of Glomerular Extracellular Matrix Composition and Organization.

Glomerular disease often features altered histologic patterns of extracellular matrix (ECM). Despite this, the potential complexities of the glomerular ECM in both health and disease are poorly understood. To explore whether genetic background and sex determine glomerular ECM composition, we investigated two mouse strains, FVB and B6, using RNA microarrays of isolated glomeruli combined with proteomic glomerular ECM analyses. These studies, undertaken in healthy young adult animals, revealed unique strain- and sex-dependent glomerular ECM signatures, which correlated with variations in levels of albuminuria and known predisposition to progressive nephropathy. Among the variation, we observed changes in netrin 4, fibroblast growth factor 2, tenascin C, collagen 1, meprin 1-α, and meprin 1-ß. Differences in protein abundance were validated by quantitative immunohistochemistry and Western blot analysis, and the collective differences were not explained by mutations in known ECM or glomerular disease genes. Within the distinct signatures, we discovered a core set of structural ECM proteins that form multiple protein-protein interactions and are conserved from mouse to man. Furthermore, we found striking ultrastructural changes in glomerular basement membranes in FVB mice. Pathway analysis of merged transcriptomic and proteomic datasets identified potential ECM regulatory pathways involving inhibition of matrix metalloproteases, liver X receptor/retinoid X receptor, nuclear factor erythroid 2-related factor 2, notch, and cyclin-dependent kinase 5. These pathways may therefore alter ECM and confer susceptibility to disease.

Vascular growth factors play critical roles in kidney glomeruli.

Kidney glomeruli ultrafilter blood to generate urine and they are dysfunctional in a variety of kidney diseases. There are two key vascular growth factor families implicated in glomerular biology and function, namely the vascular endothelial growth factors (VEGFs) and the angiopoietins (Angpt). We present examples showing not only how these molecules help generate and maintain healthy glomeruli but also how they drive disease when their expression is dysregulated. Finally, we review how manipulating VEGF and Angpt signalling may be used to treat glomerular disease.

Targeted glomerular angiopoietin-1 therapy for early diabetic kidney disease.

Vascular growth factors play an important role in maintaining the structure and integrity of the glomerular filtration barrier. In healthy adult glomeruli, the proendothelial survival factors vascular endothelial growth factor-A (VEGF-A) and angiopoietin-1 are constitutively expressed in glomerular podocyte epithelia. We demonstrate that this milieu of vascular growth factors is altered in streptozotocin-induced type 1 diabetic mice, with decreased angiopoietin-1 levels, VEGF-A upregulation, decreased soluble VEGF receptor-1 (VEGFR1), and increased VEGFR2 phosphorylation. This was accompanied by marked albuminuria, nephromegaly, hyperfiltration, glomerular ultrastructural alterations, and aberrant angiogenesis. We subsequently hypothesized that restoration of angiopoietin-1 expression within glomeruli might ameliorate manifestations of early diabetic glomerulopathy. Podocyte-specific inducible repletion of angiopoietin-1 in diabetic mice caused a 70% reduction of albuminuria and prevented diabetes-induced glomerular endothelial cell proliferation; hyperfiltration and renal morphology were unchanged. Furthermore, angiopoietin-1 repletion in diabetic mice increased Tie-2 phosphorylation, elevated soluble VEGFR1, and was paralleled by a decrease in VEGFR2 phosphorylation and increased endothelial nitric oxide synthase Ser(1177) phosphorylation. Diabetes-induced nephrin phosphorylation was also reduced in mice with angiopoietin-1 repletion. In conclusion, targeted angiopoietin-1 therapy shows promise as a renoprotective tool in the early stages of diabetic kidney disease.