Assessment of the Inflammatory Effects of Gut Microbiota from Human Twins Discordant for Ulcerative Colitis on Germ-free Mice

Disturbances in gut microbiota are prevalent in inflammatory bowel disease (IBD), which includes ulcerative colitis (UC). However, whether these disturbances contribute to development of the disease or are a result of the disease is unclear. In pairs of human twins discordant for IBD, the healthy twin has a higher risk of developing IBD and a gut microbiota that is more similar to that of IBD patients as compared with healthy individuals. Furthermore, appropriate medical treatment may mitigate these disturbances. To study the correlation between microbiota and IBD, we transferred stool samples from a discordant human twin pair: one twin being healthy and the other receiving treatment for UC. The stool samples were transferred from the disease-discordant twins to germ-free pregnant dams. Colitis was induced in the offspring using dextran sodium sulfate. As compared with offspring born to mice dams inoculated with stool from the healthy cotwin, offspring born to dams inoculated with stool from the UC-afflicted twin had a lower disease activity index, less gut inflammation, and a microbiota characterized by higher α diversity and a more antiinflammatory profile that included the presence and higher abundance of antiinflammatory species such as Akkermansia spp., Bacteroides spp., and Parabacteroides spp. These findings suggest that the microbiota from the healthy twin may have had greater inflammatory properties than did that of the twin undergoing UC treatment.

Effect of Spironolactone on Kidney Function in Kidney Transplant Recipients: A Randomized Placebo-Controlled Clinical Trial

BACKGROUND

Long-term kidney allograft survival is hampered by progressive interstitial fibrosis and tubular atrophy. The SPIREN trial tested the hypothesis that the mineralocorticoid receptor antagonist spironolactone stabilizes kidney function and attenuates glomerular barrier injury in kidney transplant patients treated with calcineurin inhibitors.

METHODS

Randomized, placebo-controlled, double blind clinical trial including 188 prevalent kidney transplant patients. Patients were randomized to spironolactone or placebo for three years. Glomerular filtration rate was measured along with proteinuria and kidney fibrosis. The primary endpoint was change in measured glomerular filtration rate. Secondary outcomes were 24h proteinuria, kidney allograft fibrosis and cardiovascular events. Measured glomerular filtration rates, 24h proteinuria and blood pressure were determined yearly. Kidney biopsies were collected at baseline and after two years (n=48). Fibrosis was evaluated by quantitative stereology and classified according to Banff.

RESULTS

The groups were comparable at baseline except for slightly older allografts in the spironolactone group. Spironolactone reduced measured glomerular filtration rates (up to -7.6 (95% CI -10.9;-4.3) ml/min compared to placebo) independently of time since transplantation and blood pressure with no impact on the kidney function curve over time and reduced 24h proteinuria after one year. There was no significant effect of spironolactone on the development of interstitial fibrosis.

CONCLUSION

Spironolactone added to standard therapy for three years in kidney transplant patients did not improve kidney function, long-term proteinuria or interstitial fibrosis.

Diagnostic utility of combining PRAME and HMB-45 stains in primary melanocytic tumors

BACKGROUND

Pathologists face ongoing challenges distinguishing between benign and malignant melanocytic tumors. PRAME (PReferentially expressed Antigen in Melanoma) has a demonstrated value distinguishing between these types of lesions. However, the sensitivity of single immunohistochemistry is variable. HMB-45 is another valuable marker, but on its own, has a limited ability in setting of primary melanocytic tumors. This study sought to evaluate the diagnostic potential of a dual panel combining PRAME and HMB-45 in the assessment of primary melanocytic tumors.

METHODS

259 tumors, of which 141 were benign nevi, 31 dysplastic nevi (either low- or high grade dysplasia), and further 87 malignant melanomas, were retrieved from the department's archives and assessed by two experienced dermatopathologists. New sections were stained with PRAME and HMB-45, respectively. For PRAME, a nuclear, and for HMB-45, a cytoplasmic staining, was considered positive and scored as described in the literature on a scale from 0 to 4+. Only dermal component was assessed on HMB-45 stain.

RESULTS

PRAME was diffusely expressed in only 1 benign nevus, with focal expression in further 28 compared to 22 diffusely and 103 focally HMB-45-positive benign nevi. 5 high-grade dysplastic nevi showed diffuse PRAME expression in epidermal component, with varying degree of positivity in adjacent dermal compartment, and further 8 dysplastic nevi showed only focal expression. HMB-45 was diffusely expressed in only 2, with focal expression in 23, and no apparent positivity in remaining 6 dysplastic nevi. In invasive melanoma group, PRAME stained >75 % cells in 64/87 tumors, however, 10/87 melanomas were completely negative. HMB-45 was captured diffusely in 49/87 melanomas, 32 showed patchy expression, and 6 tumors were blank negative. Diffuse 4+ PRAME positivity showed superior sensitivity and specificity of 73,6 % and 96,5 %, respectively, compared to HMB-45, 56,3 % and 86,0 %, respectively. No nevi showed double 4+ positivity, however, the sensitivity for double positivity was only 49,4 %.

CONCLUSION

Our results confirm the superiority of PRAME over HMB-45 in the differential diagnosis of melanocytic tumors. However, combined staining can significantly increase specificity, rendering a benign diagnosis more unlikely in a double 4+ diffuse positivity setting.

[Digital pathology]

Digitalisation of pathology slides allows pathologists to make diagnoses using a high-resolution computer screen instead of a conventional microscope. In 2020/21, the four pathology departments in the Region of Southern Denmark implemented digital pathology for all histologic samples. Going digital necessitated optimisation of workflows and training of pathologists, avoiding a reduction in diagnostic quality. This review describes the process for realisation of digital pathology and its future perspectives, including artificial intelligence algorithms to be implemented.

Prior to Implementation of Digital Pathology-Assessment of Expectations among Staff by Means of Normalization Process Theory

The Region of Southern Denmark is the first in Denmark to implement digital pathology (DIPA), starting at the end of 2020. The DIPA process involves changes in workflow, and the pathologist will have to diagnose based on digital whole slide imaging instead of through the traditional use of the conventional light microscope and glass slides. In addition, in the laboratory, the employees will have to implement one more step to their workflow—scanning of tissue. The aim of our study was to assess the expectations and readiness among employees and management towards the implementation of DIPA, including their thoughts and motivations for starting to use DIPA. We used a mixed-method approach. Based on the findings derived from 18 semi-structured interviews with employees from the region’s departments of pathology, we designed a questionnaire, including questions from the normalization measure development tool. The questionnaires were e-mailed to 181 employees. Of these employees, 131 responded to the survey. Overall, they reported feeling sufficiently tech-savvy to be able to use DIPA, and they had high expectations as well as motivation and readiness for the upcoming changes. However, the employees were skeptical regarding the allocation of resources, and few were aware of reports about the effects of DIPA. Based on the findings, it seems to be important to provide not only a thorough introduction to the new intervention and the changes it will entail, but also to continue to ensure that the staff know how it works and why it is necessary to implement.

On the Road to Digital Pathology in Denmark-National Survey and Interviews

Digital pathology (DP) is changing pathology departments dramatically worldwide, yet globally, few departments are presently digitalized for the full diagnostic workflow. Denmark is also on the road to full digitalization countrywide, and this study aim to cover experiences during the implementation process in a national context. Thus, quantitative questionnaires were distributed to all pathology departments in Denmark (n = 13) and distributed to all professions including medical clinical directors, medical doctors (MD) and biomedical laboratory scientists (BLS). For a qualitative perspective, we interviewed four employees representing four professions. Data were collected in 2019–2020. From the questionnaire and interviews, we found strategies differed at the Danish departments with regards to ambitions, technological equipment, workflows, and involvement of type of professions. DP education was requested by personnel. Informants were in general positive toward the digital future but mainly had concerns regarding the political pressure to integrate DP before technological advances are sufficient for maintaining rational budgets, workflows, and for sustaining diagnostic quality. This study is a glance on the Danish implementation process in its early stages from personnel’s point of view. It shows the complexity when large new workflow processes are to be implemented countrywide and with a large diversity of stakeholders like managers, MD, BLS, IT-professionals, and authorities. To ensure best technological and economical solutions and to maintain—or even optimize—diagnostic quality with DP and workflow alignment, we suggest superior inter- and intradepartmental communication. When implementing DP countrywide, a national working group is warranted with the variety of stakeholders represented.

FC 118: The Effect of Spironolactone on Calcineurin Inhibitor Induced Nephrotoxicity—The Spiren Trial

BACKGROUND AND AIMS

Improving long-term allograft survival has been a challenge for nephrologists for decades. A common feature in late allograft failure is progressive interstitial fibrosis and tubular atrophy.[1] Increasing evidence points towards the mineralocorticoid hormone aldosterone to contribute to renal fibrosis.[2] The SPIREN trial was designed to test the hypothesis that the mineralocorticoid receptor antagonist spironolactone attenuates renal injury in kidney transplant patients treated with calcineurin inhibitors evaluated as measured glomerular filtration rate, proteinuria and renal fibrosis.[3]

METHOD

The SPIREN trial was a randomized, placebo-controlled, double-blind clinical trial including 188 prevalent renal transplant patients from four Danish sites. Patients were randomized 1:1 to spironolactone 25–50 mg daily or placebo for 3 years. At baseline and yearly hereafter, we performed chrome-EDTA clearance, 24-h urine samples, ambulatory blood pressure measurements, and blood and urine samples. In a subgroup, an allograft biopsy was made at baseline and after 2 years (n = 48). Numeric data were analysed using mixed-effects linear regressions. Biopsies were scored according to the Banff classification and the extent of fibrosis was additionally evaluated using point counting. All analyses were performed as intention to treat.

RESULTS

In total, 180 patients were randomized to spironolactone (n = 90) or placebo (n = 90). The groups were comparable at baseline (Table 1) except a difference in the age of the allograft [median 4.4 (IQR 1.1–10.0) versus 2.0 (0.7–6.6) years]. There was a significant reduction in chrome-EDTA clearance in the spironolactone group after 1 year independently of time since transplantation and blood pressure. This persisted throughout the trial. This reduction corresponded to a reduction of eGFR after 1 week of treatment as evaluated by the CKD-EPI formula. The renal function of the placebo group remained stable. Twenty-four-hour proteinuria was reduced significantly after 1 year in the spironolactone group, but this difference was not significant after 2 and 3 years. Ambulatory systolic blood pressure was reduced to 1–2 mmHg in the spironolactone group and increased to 1–4 mmHg in the placebo group (P < 0.05). Data regarding urine albumin/creatinine ratio and quantitative biopsy data are pending.

CONCLUSION

Spironolactone added to standard therapy for three years in renal transplant patients did not improve renal function or long-term proteinuria. The reduction of chrome-EDTA clearance in the spironolactone group occurred within the first year of treatment and was most likely due to the well-known, reversible and presumed hemodynamic adverse effect of spironolactone on renal function. Whether spironolactone reduced progression of interstitial fibrosis remains to be analysed.

MFAP4 Deficiency Attenuates Angiotensin II-Induced Abdominal Aortic Aneurysm Formation Through Regulation of Macrophage Infiltration and Activity

Objective: Abdominal aortic aneurysm (AAA) is a common age-related vascular disease characterized by progressive weakening and dilatation of the aortic wall. Microfibrillar-associated protein 4 (MFAP4) is an extracellular matrix (ECM) protein involved in the induction of vascular remodeling. This study aimed to investigate if MFAP4 facilitates the development of AAA and characterize the underlying MFAP4-mediated mechanisms.

Approach and Results: Double apolipoprotein E- and Mfap4-deficient (ApoE^−/−Mfap4^−/−) and control apolipoprotein E-deficient (ApoE^−/−) mice were infused subcutaneously with angiotensin II (Ang II) for 28 days. Mfap4 expression was localized within the adventitial and medial layers and was upregulated after Ang II treatment. While Ang II-induced blood pressure increase was independent of Mfap4 genotype, ApoE^−/−Mfap4^−/− mice exhibited significantly lower AAA incidence and reduced maximal aortic diameter compared to ApoE^−/− littermates. The ApoE^−/−Mfap4^−/− AAAs were further characterized by reduced macrophage infiltration, matrix metalloproteinase (MMP)-2 and MMP-9 activity, proliferative activity, collagen content, and elastic membrane disruption. MFAP4 deficiency also attenuated activation of integrin- and TGF-β-related signaling within the adventitial layer of AAA tissues. Finally, MFAP4 stimulation promoted human monocyte migration and significantly upregulated MMP-9 activity in macrophage-like THP-1 cells.

Conclusion: This study demonstrates that MFAP4 induces macrophage-rich inflammation, MMP activity, and maladaptive remodeling of the ECM within the vessel wall, leading to an acceleration of AAA development and progression. Collectively, our findings suggest that MFAP4 is an essential aggravator of AAA pathology that acts through regulation of monocyte influx and MMP production.

Surgically induced ischemia has no impact on protein expression levels of HIF-1α and related biomarkers in renal cell carcinoma

The increasing demands for personalized targeted therapy directed against renal cell carcinoma have driven a search for predictive markers. Novel therapies targeting HIF-1α in renal cell carcinoma have been developed, and HIF-1α has been suggested as a novel predictive marker of response to therapy. The surgical resection of a kidney tumor induces tissue ischemia, and HIF-1α is an oxygen-sensitive transcription factor, which is known to be upregulated during hypoxia. This study investigated the impact of intra-surgical and post-surgical ischemia on protein expression levels of HIF-1α and three related biomarkers (VEGF, GLUT-1, and CAIX) in 20 patients with renal cell carcinoma with immunohistochemistry and Western blotting. Surgical ischemia did not have a significant impact on protein expression levels of any of the investigated markers. Long-post-surgical ischemia resulted in reduced expression levels of HIF-1α, probably due to autolysis. Our results suggest that HIF-1α is a stable protein, with expression levels not affected by intra-surgical ischemia, and hence, HIF-1α is suited for marker analysis.

Differential localization patterns of claudin 10, 16, and 19 in human, mouse, and rat renal tubular epithelia

Functional properties of the paracellular pathway depend critically on the set of claudins (CLDN) expressed at the tight junction. Two syndromes are causally linked to loss-of-function mutations of claudins: hypohidrosis, electrolyte imbalance, lacrimal gland dysfunction, ichthyosis, and xerostomia (HELIX) syndrome caused by genetic variations in the CLDN10 gene and familial hypomagnesemia with hypercalciuria and nephrocalcinosis caused by genetic variations in the CLDN16 or CLDN19 genes. All three genes are expressed in the kidney, particularly in the thick ascending limb (TAL). However, localization of these claudins in humans and rodents remains to be delineated in detail. We studied the segmental and subcellular expression of CLDN10, CLDN16, and CLDN19 in both paraffin-embedded and frozen kidney sections from the adult human, mouse, and rat using immunohistochemistry and immunofluorescence, respectively. Here, CLDN10 was present in a subset of medullary and cortical TAL cells, localizing to basolateral domains and tight junctions in human and rodent kidneys. Weak expression was detected at the tight junction of proximal tubular cells. CLDN16 was primarily expressed in a subset of TAL cells in the cortex and outer stripe of outer medulla, restricted to basolateral domains and tight junctional structures in both human and rodent kidneys. CLDN19 predominantly colocalized with CLDN16 in tight junctions and basolateral domains of the TAL but was also found in basolateral and junctional domains in more distal sites. CLDN10 expression at tight junctions almost never overlapped with that of CLND16 and CLDN19, consistent with distinct junctional pathways with different permeation profiles in both human and rodent kidneys.NEW & NOTEWORTHY This study used immunohistochemistry and immunofluorescence to investigate the distribution of claudin 10, 16, and 19 in the human, mouse, and rat kidney. The findings showed distinct junctional pathways in both human and rodent kidneys, supporting the existence of different permeation profiles in all species investigated.

Coding practice in national and regional kidney biopsy registries

Background

Kidney biopsy registries all over the world benefit research, teaching and health policy. Comparison, aggregation and exchange of data is however greatly dependent on how registration and coding of kidney biopsy diagnoses are performed. This paper gives an overview over kidney biopsy registries, explores how these registries code kidney disease and identifies needs for improvement of coding practice.

Methods

A literature search was undertaken to identify biopsy registries for medical kidney diseases. These data were supplemented with information from personal contacts and from registry websites. A questionnaire was sent to all identified registries, investigating age of registries, scope, method of coding, possible mapping to international terminologies as well as self-reported problems and suggestions for improvement.

Results

Sixteen regional or national kidney biopsy registries were identified, of which 11 were older than 10 years. Most registries were located either in Europe (10/16) or in Asia (4/16). Registries most often use a proprietary coding system (12/16). Only a few of these coding systems were mapped to SNOMED CT (1), older SNOMED versions (2) or ERA-EDTA PRD (3). Lack of maintenance and updates of the coding system was the most commonly reported problem.

Conclusions

There were large gaps in the global coverage of kidney biopsy registries. Limited use of international coding systems among existing registries hampers interoperability and exchange of data. The study underlines that the use of a common and uniform coding system is necessary to fully realize the potential of kidney biopsy registries.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02365-3.

The Mechanism Switching the Osteoclast From Short to Long Duration Bone Resorption

The current models of osteoclastic bone resorption focus on immobile osteoclasts sitting on the bone surface and drilling a pit into the bone matrix. It recently appeared that many osteoclasts also enlarge their pit by moving across the bone surface while resorbing. Drilling a pit thus represents only the start of a resorption event of much larger amplitude. This prolonged resorption activity significantly contributes to pathological bone destruction, but the mechanism whereby the osteoclast engages in this process does not have an answer within the standard bone resorption models. Herein, we review observations that lead to envision how prolonged resorption is possible through simultaneous resorption and migration. According to the standard pit model, the “sealing zone” which surrounds the ruffled border (i.e., the actual resorption apparatus), “anchors” the ruffled border against the bone surface to be resorbed. Herein, we highlight that continuation of resorption demands that the sealing zone “glides” inside the cavity. Thereby, the sealing zone emerges as the structure responsible for orienting and displacing the ruffled border, e.g., directing resorption against the cavity wall. Importantly, sealing zone displacement stringently requires thorough collagen removal from the cavity wall - which renders strong cathepsin K collagenolysis indispensable for engagement of osteoclasts in cavity-enlargement. Furthermore, the sealing zone is associated with generation of new ruffled border at the leading edge, thereby allowing the ruffled border to move ahead. The sealing zone and ruffled border displacements are coordinated with the migration of the cell body, shown to be under control of lamellipodia at the leading edge and of the release of resorption products at the rear. We propose that bone resorption demands more attention to osteoclastic models integrating resorption and migration activities into just one cell phenotype.

The Utility of 18F-FDG PET/CT in Patients With Clinical Suspicion of Polymyalgia Rheumatica and Giant Cell Arteritis: A Prospective, Observational, and Cross-sectional Study

Objective

To define the proportions of agreement between fluorine‐18‐fluorodeoxyglucose (18F‐FDG) positron emission tomography/computed tomography (PET/CT), clinical diagnosis, and temporal artery biopsy (TAB) in patients with polymyalgia rheumatica (PMR) and giant cell arteritis (GCA). Furthermore, the association of 18F‐FDG PET/CT uptake patterns and clinical presentation of newly diagnosed PMR and GCA was investigated.

Methods

Eighty patients newly suspected of having PMR, GCA, or concomitant PMR and GCA were included and followed for 40 weeks. Every patient underwent an 18F‐FDG PET/CT scan before or within 3 days of initiation of steroids in case of GCA. FDG uptakes in 8 paired articular/periarticular sites and 14 arterial segments were evaluated based on a 4‐point visual grading scale.

Results

Of the 80 patients (female: 50 [62.5%]; mean age ± SD: 72.0 ± 7.9), 64 (80.0%) patients were diagnosed with pure PMR, 3 (3.7%) with pure GCA, and 10 (12.5%) with concomitant PMR and GCA. Additionally, three (3.7%) patients were diagnosed with seronegative rheumatoid arthritis during the follow‐up period. For the diagnosis of PMR, 18F‐FDG PET/CT had a proportion of agreement of 75.3 (64.2‐84.4), compared with clinical diagnosis. When comparing findings of 18F‐FDG PET/CT with TAB, 18F‐FDG PET/CT had a proportion of agreement of 93.0 (84.3‐97.7) in all included patients and 69.2 (38.6‐90.9) in the subgroup of patients with vasculitis. C‐reactive protein was significantly higher in patients with PMR activity on 18F‐FDG PET/CT compared with those without 18F‐FDG PET/CT activity (P value = 0.006).

Conclusions

18F‐FDG PET/CT is a powerful imaging technique in PMR and GCA that was in good agreement with clinical diagnosis and TAB.

Low-intensity shockwave therapy in the treatment of diabetic nephropathy: a prospective Phase 1 study

BACKGROUND

Low-intensity shockwave therapy (LI-SWT) is suggested as a therapy for promoting tissue regeneration. In pigs, it was recently found that LI-SWT improved renal function after ischaemic injury. Our objectives were to study glomerular filtration rate (GFR) and albuminuria in diabetic nephropathy (DN) after treatment with LI-SWT. The present pilot study reports on the clinical safety of LI-SWT in DN.

METHODS

A total of 14 patients with diabetes mellitus and Stage 3 chronic kidney disease were recruited for this prospective, one-arm Phase 1 study. The patients were treated with six sessions of LI-SWT during a 3-week period. At each session, 3000 shockwaves were applied to each kidney with 0.265 mJ/mm2, extended focal size and 4 Hz. Follow-up visits were performed at 1, 3 and 6 months.

RESULTS

In general, the treatment was well tolerated. Transient macroscopic haematuria was observed in three patients immediately after LI-SWT. The majority of patients experienced lower back tenderness lasting up to 2 days after treatment. There was no need for analgesic treatment. LI-SWT showed no negative effect on GFR and albuminuria. At baseline, median (interquartile range) GFR was 33.5 mL/min/1.73 m2 (27.8-43.8) compared with 36.0 mL/min/1.73 m2 (27.5-52.0) at 6 months follow-up. In parallel, median albuminuria was 256 mg/24 h (79-619) at baseline and tended to decrease to 137 mg/24 h (41-404) 6 months after LI-SWT. There was no statistical difference between baseline and follow-up results.

CONCLUSIONS

LI-SWT is a safe treatment for DN. Inclusion of more patients is needed to determine whether LI-SWT can improve renal functional outcomes.

Prevalence of Newly Diagnosed Malignancies in Patients with Polymyalgia Rheumatica and Giant Cell Arteritis, Comparison of 18F-FDG PET/CT Scan with Chest X-ray and Abdominal Ultrasound: Data from a 40 Week Prospective, Exploratory, Single Centre Study

The aim of the study was to identify the prevalence of newly diagnosed malignancies in patients with polymyalgia rheumatica (PMR) and giant cell arteritis (GCA), with the aid of 18F-FDG PET/CT scan compared to conventional imaging techniques: Chest X-ray (CXR) and abdominal ultrasound (US). Secondarily, to examine the relative diagnostic accuracy of these two imaging modalities for the detection of cancer. Eighty consecutive patients with newly diagnosed PMR, GCA, or concomitant PMR and GCA, were included and followed up for 40 weeks. All patients underwent an 18F-FDG PET/CT scan, CXR, and abdominal US at diagnosis. Imaging findings were dichotomously categorized into malignant or benign. Among 80 patients, three patients were diagnosed with seronegative rheumatoid arthritis and were excluded from the analysis. Of the remaining 77, 64 (83.1%) patients were diagnosed with pure PMR, 3 (3.9%) with pure GCA, and 10 (13.0%) with concomitant PMR and GCA. Five types of cancer that were more prevalent than the one-year prevalence of 1.2% among the background population were found in four (5.2%; 95%CI: 1.4-12.8%) patients. CXR/abdominal US could detect the solid cancer in one patient, whereas 18F-FDG PET/CT could identify all four solid cancers. Furthermore, four (5.2%; 95%CI: 1.4-12.8%) cases of monoclonal gammopathy of undetermined significance (MGUS) were found. An increase in C reactive protein (CRP) implicated an increased risk for cancer of 2.4% (OR: 1.024, 95%CI: 1.001-1.047; p = 0.041). 18F-FDG PET/CT can reveal occult cancers at an early stage with a high negative predictive value, and it is specifically beneficial in PMR/GCA patients with nonspecific symptoms.

Histo-molecular differentiation of renal cancer subtypes by mass spectrometry imaging and rapid proteome profiling of formalin-fixed paraffin-embedded tumor tissue sections

Pathology differentiation of renal cancer types is challenging due to tissue similarities or overlapping histological features of various tumor (sub) types. As assessment is often manually conducted outcomes can be prone to human error and therefore require high-level expertise and experience. Mass spectrometry can provide detailed histo-molecular information on tissue and is becoming increasingly popular in clinical settings. Spatially resolving technologies such as mass spectrometry imaging and quantitative microproteomics profiling in combination with machine learning approaches provide promising tools for automated tumor classification of clinical tissue sections.

In this proof of concept study we used MALDI-MS imaging (MSI) and rapid LC-MS/MS-based microproteomics technologies (15 min/sample) to analyze formalin-fixed paraffin embedded (FFPE) tissue sections and classify renal oncocytoma (RO, n = 11), clear cell renal cell carcinoma (ccRCC, n = 12) and chromophobe renal cell carcinoma (ChRCC, n = 5). Both methods were able to distinguish ccRCC, RO and ChRCC in cross-validation experiments. MSI correctly classified 87% of the patients whereas the rapid LC-MS/MS-based microproteomics approach correctly classified 100% of the patients.

This strategy involving MSI and rapid proteome profiling by LC-MS/MS reveals molecular features of tumor sections and enables cancer subtype classification. Mass spectrometry provides a promising complementary approach to current pathological technologies for precise digitized diagnosis of diseases.

The frequency of cardiac amyloidosis in 182 patients receiving carpal tunnel release surgery

Introduction

Retrospective studies have suggested that a significant proportion of patients with cardiac amyloidosis received surgical treatment for carpal tunnel syndrome (CTS) 5–10 years before diagnosis of their cardiac condition. So far, one cross-sectional study has investigated the presence of localized and systemic amyloidosis in 98 patients undergoing carpal tunnel release surgery (CTRS). Ten percent were shown to have amyloid deposits in the carpal tunnel while two had cardiac involvement caused by either AL amyloidosis or wild-type transthyretin amyloidosis (ATTR).

Purpose

To investigate the prevalence of cardiac amyloidosis among unselected and consecutive patients undergoing CTRS.

Methods

Tissue samples from the carpal tunnel of 182 CTRS patients were stained with Congo Red. Amyloid positive samples were subtyped by immunoelectron microscopy and mass spectrometry.

Amyloid positive patients underwent investigations for cardiac amyloidosis including ECG-recording, echocardiography and strain imaging, cardiac magnetic resonance imaging and whole-body scintigraphy (99m-tc-DPD). Genetic investigation of the gene for TTR was performed in patients with ATTR amyloidosis or an undetermined subtype. Patients were also investigated by measurements of NT-proBNP, troponins, immunoglobulins, M-protein in serum and urine, and free light kappa and lambda chains in serum.

Results

In total, 16% (29/182) of the patients had amyloid positive biopsies. They were significantly older than amyloid negative patients (73 years vs 53 years, p<0.001). The prevalence of males was significantly higher in the amyloid positive group (66% vs 25%, p<0.001). The presence of bilateral CTS was not associated with amyloid deposits.

The subtype of amyloid was shown to be (a) ATTR in 86% (n=25) of patients, (b) localized light-chain amyloidosis in 3% (n=1), and (c) fibrinogen alpha amyloidosis in 3% (n=1), while the amount of tissue did not allow subtyping in 7% (n=2). All ATTR patients had a normal genetic investigation.

So far, 24 of the 29 amyloid positive patients have completed all clinical investigations and no one fulfilled diagnostic criteria of cardiac amyloidosis.

Conclusion

A significant number of CTRS patients, (14%), had wild-type ATTR amyloidosis confined to the carpal tunnel. None of these had cardiac involvement. These findings were different from the results in the previous prospective study and were likely to be explained by differences in the patient cohorts investigated. We investigated unselected patients in contrast to the highly selected cohort in the previous study.

Based on the findings in the current study the proportion of CTRS patients with localized amyloidosis who may develop systemic disease is unknown. Therefore, it is necessary to perform long term follow-up of these patients before routine investigations for amyloidosis may be recommended.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Financial support was obtained by an unrestricted research grant from Alnylam Pharmaceuticals

Human kidney graft survival correlates with structural parameters in baseline biopsies: a quantitative observational cohort study with more than 14 years' follow-up

This prospective cohort study evaluates associations between structural and ultrastructural parameters in baseline biopsies from human kidney transplants and long-term graft survival after more than 14 years' follow-up. Baseline kidney graft biopsies were obtained prospectively from 54 consecutive patients receiving a kidney transplant at a single institution. Quantitative measurements were performed on the baseline biopsies by computer-assisted light microscopy and electron microscopy. Stereology-based techniques estimated the fraction of interstitial tissue, the volume of glomeruli, mesangial fraction, and basement membrane thickness of glomerular capillaries. The fraction of occluded glomeruli and scores according to the Banff classification were achieved. Kidney graft survival was analyzed by Kaplan-Meier estimates and Cox regression. Association to long-term kidney function was also analyzed. The long-term surviving kidney transplants were characterized at implantation by less arteriolar hyaline thickening (P < 0.001) and less interstitial fibrosis (P = 0.001), as well as a lower fraction of occluded glomeruli (P = 0.004) and lower glomerular volume (P = 0.03). At the latest follow-up, eGFR was decreased by 12 ml/min/1.73 m² per unit increase in the score for arteriolar hyalinosis at implantation (P = 0.02), and eGFR was decreased by 19 ml/min/1.73 m² per 10⁶ μm³ increase in glomerular volume at baseline (P = 0.03). The unbiased Cavalieri estimate of glomerular volume and the ultrastructural parameters are the first to be evaluated in a cohort study with prospective follow-up for more than 14 years. The study shows that baseline biopsies from human kidney grafts contain extraordinary long-term prognostic information, and it highlights the importance of these intrinsic graft factors.

FRI0203 A SINGLE-CENTER INVESTIGATION ON THE PREVALENCE OF MALIGNANCIES IN PATIENTS WITH POLYMYALGIA RHEUMATICA AND GIANT CELL ARTERITIS BY WAY OF 18F-FDG PET/CT: A PROSPECTIVE COHORT STUDY

Background:

Several chronic inflammatory diseases are associated with a higher risk of cancer.[1] Whether, this is the case in Polymyalgia Rheumatica (PMR) and Giant Cell Arteritis (GCA) is still a matter of debate.

Objectives:

To identify the prevalence of newly diagnosed cancers in patients with PMR and GCA by means of 18F-FDG PET/CT. Moreover, to compare the characteristics of the patients with and without cancer.

Methods:

Eighty consecutive patients with newly diagnosed PMR/GCA were studied. Diagnosis of PMR/GCA was confirmed by a 40-weeks follow up. A unilateral temporal artery biopsy (TAB) was also performed at the time of diagnosis. All included patients underwent an 18F-FDG PET/CT before, or in case of GCA, within 3 days of initiation of high dose oral glucocorticoid (40-75mg). All cancer-suspicious 18F-FDG-PET/CT findings were assessed thoroughly and malignant diseases were confirmed by histology. Total PMR and GCA scores were defined as the sum of a 4-point visual grading scale in each articular/periarticular site as well as arterial segment.

Results:

Of the 80 patients, 64 (83.1%) were diagnosed with pure PMR, 10 (13.0%) with concomitant GCA with PMR and 3 (3.9%) with pure GCA. Three patients were diagnosed with rheumatoid arthritis during follow up and excluded from the study. Five types of cancer in 4 (5.2%;95% CI:1.4-12.8%) patients were found. Two patients had breast cancer, one patient had adenocarcinoma of colon and one patient had adenocarcinoma of colon together with skin cancer. Besides, 4 (5.2%;95% CI:1.4-12.8%) patients had Monoclonal Gammopathy of Unknown Significance (MGUS). Age and C-reactive protein were significantly higher among those with solid cancers (p:0.049) and MGUS (p:0.017), respectively (Table1).

Table 1.

Characteristics of the patients with and without solid cancer ae well as MGUS

VariablesCancer –,n=73Cancer +,n=4P-valueMGUS -, n =73MGUS +,n =4P-valueAge, mean±SD71.4±7.879.7±7.50.04971.9±8.070.2±9.20.79Gender, n(%)Female46(59.7%)3(3.9%)0.9947(61.0%)2(2.6%)0.62Constitutional symptoms, n(%)70(90.9%)4(5.2%)0.9970(90.9%)4(5.2%)0.99Shoulder girdle symptoms, n(%)68(88.3%)4(5.2%)0.9968(88.3%)4(5.2%)0.99Hip girdle symptoms, n(%)65(84.4%)3(3.9%)0.4064(83.1%)4(5.2%)0.99Cranial symptoms, n(%)19(24.7%)0(0%)0.5717(22.1%)2(2.6%)0.25Patients pain VAS75(50-85)62.5(50-75)0.5372.5(50 -80)87.5(77.5-95)0.07Patients global VAS80(60-90)62.5(50-75)0.3780(60-90)89.5(79.5-95)0.23Physician global VAS30(25-40)24.5(20-29)0.1530(22.5-40)37.5(32.5-45)0.17Erythrocyte sedimentation rate, mm[2-20]54(38-79)62.5(37.5-76)0.9354(38-77.5)57.5(39 -73.5)0.94C-reactive protein, mg/L[<6.0]37(17-64)34(17.0-76)0.8033(17-60)98(68 -115)0.017TAB positive7(9.1%)0(0%)0.997(9.1%)0(0%)0.99Total PMR score14(10-17)12(5-15)0.3914(10-17)13(6-15.5)0.64Total GCA score0(0-0)0(0-0.5)0.890(0-0)0(0-0)0.34Clinical diagnosis, n(%)0.990.53 Pure PMR60(77.9%)4(5.2%)61(79.2%)3(3.9%) Pure GCA3(3.9%)0(0%)3(3.9%)0(0%) Concomitant PMR and GCA10(13.0%)0(0%)9(11.7%)1(1.3%)

VAS: Visual analogue scale

Conclusion:

The prevalence of cancers in this cohort was higher, compared to the 1-year prevalence of all cancer sites of 1.2% among age-, gender- and region-matched background population in 2016. Occult malignancies are important and relatively prevalent findings in newly diagnosed PMR/GCA patients.

References:

[1]Hemminki K, et al. Cancer risk in hospitalized rheumatoid arthritis patients. Rheumatology (Oxford) 2008;47:698-701.

Disclosure of Interests:

None declared

Proteomic Analysis of Renal Biomarkers of Kidney Allograft Fibrosis-A Study in Renal Transplant Patients

Renal transplantation is the preferred treatment of end stage renal disease, but allograft survival is limited by the development of interstitial fibrosis and tubular atrophy in response to various stimuli. Much effort has been put into identifying new protein markers of fibrosis to support the diagnosis. In the present work, we performed an in-depth quantitative proteomics analysis of allograft biopsies from 31 prevalent renal transplant patients and correlated the quantified proteins with the volume fraction of fibrosis as determined by a morphometric method. Linear regression analysis identified four proteins that were highly associated with the degree of interstitial fibrosis, namely Coagulation Factor XIII A chain (estimate 18.7, adjusted p < 0.03), Uridine Phosphorylase 1 (estimate 19.4, adjusted p < 0.001), Actin-related protein 2/3 subunit 2 (estimate 34.2, adjusted p < 0.05) and Cytochrome C Oxidase Assembly Factor 6 homolog (estimate -44.9, adjusted p < 0.002), even after multiple testing. Proteins that were negatively associated with fibrosis (p < 0.005) were primarily related to normal metabolic processes and respiration, whereas proteins that were positively associated with fibrosis (p < 0.005) were involved in catabolic processes, cytoskeleton organization and the immune response. The identified proteins may be candidates for further validation with regards to renal fibrosis. The results support the notion that cytoskeleton organization and immune responses are prevalent processes in renal allograft fibrosis.

Immunoelectron microscopy and mass spectrometry for classification of amyloid deposits

Amyloidosis is a shared name for several rare, complex and serious diseases caused by extra-cellular deposits of different misfolded proteins. Accurate characterization of the amyloid protein is essential for patient care. Immunoelectron microscopy (IEM) and laser microdissection followed by tandem mass spectrometry (LMD-MS) are new gold standards for molecular subtyping. Both methods perform superiorly to immunohistochemistry, but their complementarities, strengths and weaknesses across amyloid subtypes and organ biopsy origin remain undefined. Therefore, we performed a retrospective study of 106 Congo Red positive biopsies from different involved organs; heart, kidney, lung, gut mucosa, skin and bone marrow. IEM, performed with gold-labelled antibodies against kappa light chains, lambda light chains, transthyretin and amyloid A, identified specific staining of amyloid fibrils in 91.6%; in six biopsies amyloid fibrils were not identified, and in two, the fibril subtype could not be established. LMD-MS identified amyloid protein signature in 98.1%, but in nine the amyloid protein could not be clearly identified. MS identified protein subtype in 89.6%. Corresponding specificities ranged at organ level from 94-100%. Concordance was 89.6-100% for different amyloid subtypes. Importantly, combined use of both methods increased the diagnostic classification to 100%. Some variety in performances at organ level was observed.

Coordination of Fusion and Trafficking of Pre-osteoclasts at the Marrow-Bone Interface

Fusion is the final osteoclast differentiation step leading to bone resorption. In healthy trabecular bone, osteoclast fusion is restricted to bone surfaces undergoing resorption, and necessarily requires site-specific recruitment of mononucleated pre-osteoclasts originating from the bone marrow. However, the spatiotemporal mechanism coordinating recruitment and fusion is poorly investigated. Herein we identify a collagen/vascular network as a likely structure supporting this mechanism. We therefore used multiplex immunohistochemistry and electron microscopy on human iliac crest bone samples, in combination with functional assays performed in vitro with osteoclasts generated from healthy blood donors. First, we found that putative pre-osteoclasts are in close vicinity of a network of collagen fibers associated with vessels and bone remodeling compartment canopies. Based on 3D-reconstructions of serial sections, we propose that this network may serve as roads leading pre-osteoclasts to resorption sites, as reported for cell migration in other tissues. Importantly, almost all these bone marrow pre-osteoclasts, but only some osteoclasts, express the collagen receptor OSCAR, which is reported to induce fusion competence. Furthermore, differentiating osteoclasts cultured on collagen compared to mineral show higher fusion rates, higher expression of fusogenic cytokines, and a CD47 plasma membrane distribution pattern reported to be typical of a pre-fusion state-thus collectively supporting collagen-induced fusion competence. Finally, these in vitro assays show that collagen induces high cell mobility. The present data lead to a model where collagen fibers/vasculature support the coordination between traffic and fusion of pre-osteoclasts, by serving as a physical road and inducing fusion competence as well as cell mobility.

Nephrotic syndrome is associated with increased plasma K+ concentration, intestinal K+ losses, and attenuated urinary K+ excretion: a study in rats and humans

The present study tested the hypotheses that nephrotic syndrome (NS) leads to renal K⁺ loss because of augmented epithelial Na⁺ channel (ENaC) activity followed by downregulation of renal K⁺ secretory pathways by suppressed aldosterone. The hypotheses were addressed by determining K⁺ balance and kidney abundance of K⁺ and Na⁺ transporter proteins in puromycin aminonucleoside (PAN)-induced rat nephrosis. The effects of amiloride and angiotensin II type 1 receptor and mineralocorticoid receptor (MR) antagonists were tested. Glucocorticoid-dependent MR activation was tested by suppression of endogenous glucocorticoid with dexamethasone. Urine and plasma samples were obtained from pediatric patients with NS in acute and remission phases. PAN-induced nephrotic rats had ENaC-dependent Na⁺ retention and displayed lower renal K⁺ excretion but elevated intestinal K⁺ secretion that resulted in less cumulated K⁺ in NS. Aldosterone was suppressed at day 8. The NS-associated changes in intestinal, but not renal, K⁺ handling responded to suppression of corticosterone, whereas angiotensin II type 1 receptor and MR blockers and amiloride had no effect on urine K⁺ excretion during NS. In PAN-induced nephrosis, kidney protein abundance of the renal outer medullary K⁺ channel and γ-ENaC were unchanged, whereas the Na⁺-Cl^- cotransporter was suppressed and Na⁺-K⁺-ATPase increased. Pediatric patients with acute NS displayed suppressed urine Na⁺-to-K⁺ ratios compared with remission and elevated plasma K⁺ concentration, whereas fractional K⁺ excretion did not differ. Acute NS is associated with less cumulated K⁺ in a rat model, whereas patients with acute NS have elevated plasma K⁺ and normal renal fractional K⁺ excretion. In NS rats, K⁺ balance is not coupled to ENaC activity but results from opposite changes in renal and fecal K⁺ excretion with a contribution from corticosteroid MR-driven colonic secretion.

Colonic Epithelial Surfactant Protein D Expression Correlates with Inflammation in Clinical Colonic Inflammatory Bowel Disease

BACKGROUND

Inflammatory bowel diseases (IBD) are chronic disorders of the gastrointestinal tract. Surfactant protein D (SP-D) is expressed in the intestinal epithelium and is essential for innate host defense and regulation of inflammatory responses. Genetic variations of SP-D are associated with IBD, but the effects of SP-D in clinical disease development have not been clarified. We hypothesized that colonic epithelial SP-D expression is increased in parallel with intestinal inflammation with the capacity to dampen deleterious effects.

METHODS

Surgical specimens from IBD patients including Crohn's disease (n = 9) and ulcerative colitis (n = 18) were scored for expression of SP-D and inflammatory activity. Cohoused Sftpd+/+ and Sftpd-/- mouse littermates were subjected to dextran sodium sulfate (DSS) for 7 days to induce colitis. Colonic tissue was scored for histologic damage and analyzed for inflammatory markers and expression of SP-D.

RESULTS

Surgical specimens from IBD patients showed a strong positive correlation between immunoscore for SP-D and inflammatory activity (R2 = 0.78, P < 0.0001). In mice, colonic epithelial SP-D expression was very low, and DSS-induced colitis was unaffected by SP-D deficiency, although DSS induced transcription of colonic SP-D to a mild degree.

CONCLUSIONS

A strong positive correlation between inflammatory activity and epithelial expression of SP-D was observed in surgical specimens from IBD patients supporting a role for SP-D in clinical disease. The in vivo study was inconclusive due to very low intestinal SP-D expression in the mouse. Further studies are warranted to support that increased SP-D expression in the human colonic epithelium is protective against intestinal inflammation.

The effect of two exercise modalities on skeletal muscle capillary ultrastructure in individuals with type 2 diabetes

Type 2 diabetes is associated with microvascular dysfunction, but little is known about how capillary ultrastructure is affected by exercise training. To investigate the effect of two types of exercise training on skeletal muscle capillary ultrastructure and capillarization in individuals with type 2 diabetes, 21 individuals with type 2 diabetes were allocated (randomized controlled trial) to 11 weeks of aerobic exercise training consisting of either moderate-intensity endurance training (END; n = 10) or low-volume high-intensity interval training (HIIT; n = 11). Skeletal muscle biopsies (m vastus lateralis) were obtained before and after the training intervention. At baseline, there was no difference in capillarization, capillary structure, and exercise hyperemia between the two groups. After the training intervention, capillary-to-fiber ratio increased by 8% ± 3% in the END group (P < 0.05) and was unchanged in the HIIT group with no difference between groups. Endothelium thickness increased (P < 0.05), basement membrane thickness decreased (P < 0.05), and the capillary lumen tended (P = 0.07) to increase in the END group, whereas these structural indicators were unchanged after HIIT. In contrast, skeletal muscle endothelial nitric oxide synthase (eNOS) increased after HIIT (P < 0.05), but not END, whereas there was no change in vascular endothelial growth factor (VEGF), superoxide dismutase (SOD)-2, or NADPH oxidase after both training protocols. In contrast to END training, HIIT did not alter capillarization or capillary structure in individuals with type 2 diabetes. In conclusion, HIIT appears to be a less effective strategy to treat capillary rarefaction and reduce basement thickening in type 2 diabetes.

Seminal human papillomavirus originates from the body surface and is not a frequent aetiological factor in azoospermia

Human papillomavirus (HPV) DNA has been detected in the testis tissue of 6.5% of 185 men with non‐obstructive azoospermia (NOA). Others have suggested that seminal HPV originates from contamination from the genital skin and mucosa. One hundred unselected azoospermic men and 43 normal men undergoing vasectomy were recruited. Testicular biopsies for HPV examination were collected from all the men. Additionally, the normal men undergoing vasectomy delivered a semen sample and had a swab for HPV examination taken from the genital skin before vasectomy. A piece of each Vas deferens obtained during the vasectomy was examined for the presence of HPV. Two of the primarily azoospermic men were shown to have cryptozoospermia. It was not possible to detect HPV in the testis tissue of any of the included 98 azoospermic men or the 43 proven fertile men. In the proven fertile men, HPV DNA was detected in the semen of 15 men (35%), on the genital skin of 28 men (65%), and in the Vas deferens in three cases (7%). In 13 (87%) men with HPV‐positive semen samples, HPV DNA was also detected in the skin swabs, and in 11 men (73%), identical HPV genotypes were found in the two locations.

Periarterial fat from two human vascular beds is not a source of aldosterone to promote vasoconstriction

Mouse adipocytes have been reported to release aldosterone and reduce endothelium-dependent relaxation. It is unknown whether perivascular adipose tissue (PVAT) releases aldosterone in humans. The present experiments were designed to test the hypothesis that human PVAT releases aldosterone and induces endothelial dysfunction. Vascular reactivity was assessed in human internal mammary and renal segmental arteries obtained at surgery. The arteries were prepared with/without PVAT, and changes in isometric tension were measured in response to the vasoconstrictor thromboxane prostanoid receptor agonist U46619 and the endothelium-dependent vasodilator acetylcholine. The effects of exogenous aldosterone and of mineralocorticoid receptor (MR) antagonist eplerenone were determined. Aldosterone concentrations were measured by ELISA in conditioned media incubated with human adipose tissue with/without angiotensin II stimulation. Presence of aldosterone synthase and MR mRNA was examined in perirenal, abdominal, and mammary PVAT by PCR. U46619 -induced tension and acetylcholine-induced relaxation were unaffected by exogenous and endogenous aldosterone (addition of aldosterone and MR blocker) in mammary and renal segmental arteries, both in the presence and absence of PVAT. Aldosterone release from incubated perivascular fat was not detectable. Aldosterone synthase expression was not consistently observed in human adipose tissues in contrast to that of MR. Thus, exogenous aldosterone does not affect vascular reactivity and endothelial function in ex vivo human arterial segments, and the tested human adipose tissues have no capacity to synthesize/release aldosterone. In perspective, physiologically relevant effects of aldosterone on vascular function in humans are caused by systemic aldosterone originating from the adrenal gland.

Exercise Hemodynamics After Aortic Valve Replacement for Severe Aortic Stenosis

BACKGROUND

Severe aortic stenosis (AS) is often accompanied by diastolic dysfunction. After aortic valve replacement (AVR), the left ventricle often undergoes considerable reverse remodeling. Despite this, diastolic dysfunction may persist after AVR. The aims of this study were to determine the incidence of elevated left ventricular (LV) filling pressure at rest and during exercise among patients with severe AS after AVR and to describe factors related to elevated LV filling pressure, especially its association with LV and left atrial remodeling and myocardial fibrosis.

METHODS

Thirty-seven patients undergoing AVR were included. Echocardiography, cardiac computed tomography, and magnetic resonance imaging were performed before AVR. An LV biopsy sample was obtained during AVR and analyzed for collagen fraction. One year after AVR, right heart catheterization with exercise was performed. A mean pulmonary capillary wedge pressure (PCWP) ≥ 28 mm Hg during exercise was considered elevated.

RESULTS

Twelve patients (32%) had elevated exercise PCWP 1 year after AVR. Exercise PCWP was highest among patients undergoing concomitant coronary artery bypass graft surgery (30 ± 7 vs 25 ± 6 mm Hg, P = .04) and among patients with preoperative stroke volume index < 35 mL/m² (28 ± 8 vs 23 ± 4 mm Hg, P < .05). Baseline LV ejection fraction was lower among patients with elevated PCWP (56 ± 8% vs 64 ± 8%, P = .01), and coronary calcium score was significantly higher (median 870 AU [interquartile range, 454-2,491 AU] vs 179 AU [interquartile range, 63-513 AU], P = .02). Conversely, exercise PCWP was not related to the presence of high LV wall mass or to the severity of AS. Among patients undergoing isolated AVR, there was a correlation between LV interstitial volume fraction and PCWP (r = 0.57, P = .01) and mean pulmonary artery pressure (r = 0.51, P = .03) during exercise.

CONCLUSIONS

Elevated filling pressure during exercise was seen in one third of patients after AVR in this population and was seen primarily among patients with coexisting ischemic heart disease or diffuse myocardial fibrosis but was unrelated to preoperative severity of AS and LV remodeling.

H+-ATPase B1 subunit localizes to thick ascending limb and distal convoluted tubule of rodent and human kidney

The vacuolar-type H⁺-ATPase B1 subunit is heavily expressed in the intercalated cells of the collecting system, where it contributes to H⁺ transport, but has also been described in other segments of the renal tubule. This study aimed to determine the localization of the B1 subunit of the vacuolar-type H⁺-ATPase in the early distal nephron, encompassing thick ascending limbs (TAL) and distal convoluted tubules (DCT), in human kidney and determine whether the localization differs between rodents and humans. Antibodies directed against the H⁺-ATPase B1 subunit were used to determine its localization in paraffin-embedded formalin-fixed mouse, rat, and human kidneys by light microscopy and in sections of Lowicryl-embedded rat kidneys by electron microscopy. Abundant H⁺-ATPase B1 subunit immunoreactivity was observed in the human kidney. As expected, intercalated cells showed the strongest signal, but significant signal was also observed in apical membrane domains of the distal nephron, including TAL, macula densa, and DCT. In mouse and rat, H⁺-ATPase B1 subunit expression could also be detected in apical membrane domains of these segments. In rat, electron microscopy revealed that the H⁺-ATPase B1 subunit was located in the apical membrane. Furthermore, the H⁺-ATPase B1 subunit colocalized with other H⁺-ATPase subunits in the TAL and DCT. In conclusion, the B1 subunit is expressed in the early distal nephron. The physiological importance of H⁺-ATPase expression in these segments remains to be delineated in detail. The phenotype of disease-causing mutations in the B1 subunit may also relate to its presence in the TAL and DCT.

Endothelial mineralocorticoid receptor ablation does not alter blood pressure, kidney function or renal vessel contractility

Aldosterone blockade confers substantial cardiovascular and renal protection. The effects of aldosterone on mineralocorticoid receptors (MR) expressed in endothelial cells (EC) within the renal vasculature have not been delineated. We hypothesized that lack of MR in EC may be protective in renal vasculature and examined this by ablating the Nr3c2 gene in endothelial cells (EC-MR) in mice. Blood pressure, heart rate and PAH clearance were measured using indwelling catheters in conscious mice. The role of the MR in EC on contraction and relaxation was investigated in the renal artery and in perfused afferent arterioles. Urinary sodium excretion was determined by use of metabolic cages. EC-MR transgenics had markedly decreased MR expression in isolated aortic endothelial cells as compared to littermates (WT). Blood pressure and effective renal plasma flow at baseline and following AngII infusion was similar between groups. No differences in contraction and relaxation were observed between WT and EC-MR KO in isolated renal arteries during baseline or following 2 or 4 weeks of AngII infusion. The constriction or dilatations of afferent arterioles between genotypes were not different. No changes were found between the groups with respect to urinary excretion of sodium after 4 weeks of AngII infusion, or in urinary albumin excretion and kidney morphology. In conclusion, deletion of the EC-MR does not confer protection towards the development of hypertension, endothelial dysfunction of renal arteries or renal function following prolonged AngII-infusion.

Nuclear localization of the CK2α-subunit correlates with poor prognosis in clear cell renal cell carcinoma

Protein kinase CK2α, one of the two catalytic isoforms of the protein kinase CK2 has been shown to contribute to tumor development, tumor proliferation and suppression of apoptosis in various malignancies. We conducted this study to investigate CK2 expression in different subtypes of Renal Cell Carcinoma (RCC) and in the benign oncocytoma. qRT-PCR, immunohistochemistry and Western blot analyses revealed that CK2α expression was significantly increased at the mRNA and protein levels in clear cell RCC (ccRCC). Also the kinase activity of CK2 was significantly increased in ccRCC compared to normal renal cortex. Nuclear protein expression of CK2α correlated in univariate analysis with poor Progression Free Survival (HR = 8.11, p = 0.016). Functional analyses (cell proliferation assay) revealed an inhibitory effect of Caki-2 cell growth following CK2 inhibition with CX-4945. Our results suggest that CK2α promotes migration and invasion of ccRCC and therefore could serve as a novel prognostic biomarker and molecular therapeutic target in this type of cancer.

Immunohistochemical Localization of Fibrinogen C Domain Containing 1 on Epithelial and Mucosal Surfaces in Human Tissues

Fibrinogen C domain containing 1 (FIBCD1) is a transmembrane receptor that binds chitin and other acetylated compounds with high affinity. FIBCD1 has previously been shown to be present in the epithelium of the gastrointestinal tract. In the present study, we performed a detailed analysis of normally structured human tissues for the expression of FIBCD1 by quantitative PCR and immunohistochemistry. We find that FIBCD1 is expressed in epithelial cells derived from all three germ layers. Endodermal-derived epithelial cells throughout the gastrointestinal tract and the respiratory system showed high expression of FIBCD1 and also mesodermal-derived cells in the genitourinary system and ectodermal-derived epidermis and sebaceous glands cells expressed FIBCD1. In some columnar epithelial cells, for example, in the salivary gland and gall bladder, the FIBCD1 expression was clearly polarized with strong apical reaction, while other columnar cells, for example, in small and large intestine and in bronchi, the staining was equally strong apically and basolaterally. In keratinocytes in skin, tongue, and oral cavity, the FIBCD1 staining was granular. This expression pattern together with the known binding properties supports that FIBCD1 plays a role in innate immunity in the skin and at mucosal surfaces.

Two brothers with identical variants of the CLCN5 gene-one developing Dent's disease

Dent’s disease is characterized by manifestations of proximal tubule dysfunction including hypercalciuria, kidney stones, proteinuria, rickets and progressively declining kidney function. The diagnosis is based on the presence of low-molecular-weight proteinuria, hypercalciuria and at least one of the following: nephrocalcinosis, kidney stones, haematuria, hypophosphataemia or renal insufficiency. Dent’s disease is a hereditary condition that is caused by variants in the CLCN5 gene or the OCRL1 gene and affects only males. Herein, we report on two brothers who were found to have a previously reported disease-causing variant in the CLCN5 gene. One sibling had nephrocalcinosis, proteinuria and hypercalciuria, whereas the other sibling was asymptomatic and had normal laboratory findings.

Incidence, Frequency, and Clinical Characteristics of Type 3 Myocardial Infarction in Clinical Practice

OBJECTIVES

Cardiac death in a patient with symptoms and electrocardiographic changes indicative of myocardial ischemia but without available measurements of cardiac biomarkers is designated a type 3 myocardial infarction. We wanted to investigate the incidence, the frequency, and the characteristics of patients diagnosed as type 3 myocardial infarction.

METHODS

The occurrence of deaths in a well-defined geographic region was retrieved from the Danish Civil Registration System during a 1-year period from 2010 to 2011. Complementary data concerning causes of deaths were obtained from the Danish Register of Causes of Death, and ambulance and hospital patient files. Adjudication of the diagnosis was done by 2 local experts and one external senior cardiologist.

RESULTS

A total of 2766 of the 246,723 adult residents in the region had died. A type 3 myocardial infarction was diagnosed in 18 individuals, corresponding to an annual incidence of 7.3/100,000 person-years. During the same 1-year period, 488 patients had other types of myocardial infarction implying a 3.6% frequency of type 3 myocardial infarction (18 of 506) among all myocardial infarctions.

CONCLUSION

Type 3 myocardial infarction is a rare observation in clinical practice with an annual incidence below 10/100,000 person-years and a frequency of 3%-4% among all types of myocardial infarction. If autopsy data are included, the number of type 3 myocardial infarctions will increase.

Heterogeneity of miRNA expression in localized prostate cancer with clinicopathological correlations

INTRODUCTION

In the last decade microRNAs (miRNAs) have been widely investigated in prostate cancer (PCa) and have shown to be promising biomarkers in diagnostic, prognostic and predictive settings. However, tumor heterogeneity may influence miRNA expression. The aims of this study were to assess the impact of tumor heterogeneity, as demonstrated by a panel of selected miRNAs in PCa, and to correlate miRNA expression with risk profile and patient outcome.

MATERIAL AND METHODS

Prostatectomy specimens and matched, preoperative needle biopsies from a retrospective cohort of 49 patients, who underwent curatively intended surgery for localized PCa, were investigated with a panel of 6 miRNAs (miRNA-21, miRNA-34a, miRNA-125b, miRNA-126, miRNA-143, and miRNA-145) using tissue micro-array (TMA) and in situ hybridization (ISH). Inter- and intra-patient variation was assessed using intra-class correlation (ICC).

RESULTS

Four miRNAs (miRNA-21, miRNA-34a, miRNA-125, and miRNA-126) were significantly upregulated in PCa compared to benign prostatic hyperplasia (BPH), and except for miRNA-21 these miRNAs documented a positive correlation between the expression level in PCa cores and their matched BPH cores, (r > 0.72). The ICC varied from 0.451 to 0.764, with miRNA-34a showing an intra-tumoral heterogeneity accounting for less than 50% of the total variation. Regarding clinicopathological outcomes, only miRNA-143 showed potential as a prognostic marker with a higher expression correlating with longer relapse-free survival (p = 0.016).

CONCLUSION

The present study documents significant upregulation of the expression of miRNA-21, miRNA-34a, miRNA-125, and miRNA-126 in PCa compared to BPH and suggests a possible prognostic value associated with the expression of miRNA-143. The results, however, document intra-tumoral heterogeneity in the expression of various miRNAs calling for caution when using these tumor tissue biomarkers in prognostic and predictive settings.

Polymyalgia rheumatica and giant cell arteritis-three challenges-consequences of the vasculitis process, osteoporosis, and malignancy: A prospective cohort study protocol

INTRODUCTION

Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are common inflammatory conditions. The diagnosis of PMR/GCA poses many challenges since there are no specific diagnostic tests. Recent literature emphasizes the ability of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) to assess global disease activity in inflammatory diseases. 18F-FDG PET/CT may lead to the diagnosis at an earlier stage than conventional imaging and may also assess response to therapy. With respect to the management of PMR/GCA, there are 3 significant areas of concern as follows: vasculitis process/vascular stiffness, malignancy, and osteoporosis.

METHODS AND ANALYSIS

All patients with suspected PMR/GCR referred to the Rheumatology section of Medicine Department at Svendborg Hospital, Denmark. The 4 separate studies in the current protocol focus on: the association of clinical picture of PMR/GCA with PET findings; the validity of 18F-FDG PET/CT scan for diagnosis of PMR/GCA compared with temporal artery biopsy; the prevalence of newly diagnosed malignancies in patients with PMR/GCA, or PMR-like syndrome, with the focus on diagnostic accuracy of 18F-FDG PET/CT scan compared with conventional workup (ie, chest X-ray/abdominal ultrasound); and the impact of disease process, and also steroid treatment on bone mineral density, body composition, and vasculitis/vascular stiffness in PMR/GCA patients.

ETHICS AND DISSEMINATION

The study has been approved by the Regional Ethics Committee of the Region of Southern Denmark (identification number: S-20160098) and Danish Data Protection Agency (J.nr 16/40522). Results of the study will be disseminated via publications in peer-reviewed journals, and presentation at national and international conferences.

Vitamin D Depletion in Pregnancy Decreases Survival Time, Oxygen Saturation, Lung Weight and Body Weight in Preterm Rat Offspring

Animal studies suggest a role of vitamin D in fetal lung development although not studied in preterm animals. We tested the hypothesis that vitamin D depletion aggravates respiratory insufficiency in preterm rat offspring. Furthermore, the effects of vitamin D depletion on growth and lung surfactant were investigated. Female Sprague-Dawley rats were randomly assigned low vitamin D (VD_L) or control diet before mating and followed with serum 25-hydroxyvitamin D (s-25(OH)D) determinations. After cesarean section at gestational day 19 (E19) or day 22 (E22), placental weight, birth weight, crown-rump-length (CRL), oxygenation (SaO₂) at 30 min and survival time were recorded. The pup lungs were analyzed for phospholipid levels, surfactant protein A-D mRNA and the expression of the vitamin D receptor (VDR). S-25(OH)D was significantly lower in the VD_L group at cesarean section (12 vs. 30nmol/L, p<0.0001). Compared to the controls, E19 VD_L pups had lower birth weight (2.13 vs. 2.29g, p<0.001), lung weight (0.09 vs. 0.10g, p = 0.002), SaO₂(54% vs. 69%, p = 0.002) as well as reduced survival time (0.50 vs. 1.25h, p<0.0001). At E22, the VD_L-induced pulmonary differences were leveled out, but VD_L pups had lower CRL (4.0 vs. 4.5cm, p<0.0001). The phospholipid levels and the surfactant protein mRNA expression did not differ between the dietary groups. In conclusion, Vitamin D depletion led to lower oxygenation and reduced survival time in the preterm offspring, associated with reduced lung weight and birth weight. Further studies of vitamin D depletion in respiratory insufficiency in preterm neonates are warranted.

High-NaCl Diet Aggravates Cardiac Injury in Rats with Adenine-Induced Chronic Renal Failure and Increases Serum Troponin T Levels

AIMS

To examine the effects of 2 weeks of high-NaCl diet on left ventricular (LV) morphology and serum levels of cardiac troponin T (cTnT) in rats with adenine-induced chronic renal failure (ACRF).

METHODS

Male Sprague-Dawley rats either received chow containing adenine or were pair-fed an identical diet without adenine [controls (C)]. Approximately 10 weeks after the beginning of the study, the rats were randomized to either remain on a normal NaCl diet (NNa; 0.6%) or to be switched to high-NaCl chow (HNa; 4%) for 2 weeks, after which acute experiments were performed.

RESULTS

Rats with ACRF showed statistically significant increases (p < 0.001) in arterial pressure (AP), LV weight and fibrosis, and serum cTnT levels compared to controls. Two weeks of high-NaCl intake augmented the increases in AP, LV weight and fibrosis, and serum cTnT concentrations only in ACRF rats (p < 0.05 for group × NaCl intake interaction). Compared to group C-NNa, cTnT levels were elevated approximately 6-fold in group ACRF-NNa and 24-fold in group ACRF-HNa. Focal LV injury with cardiomyocyte necrosis, scarring, and fibrinoid necrosis of small arteries were only detected in group ACRF-HNa. There was a strong correlation between the degree of LV fibrosis and serum cTnT levels in ACRF rats (r = 0.81, p < 0.01).

CONCLUSION

Two weeks of high-NaCl diet in rats with ACRF produces LV injury and aggravates increases in serum cTnT levels, presumably by causing hypertension-induced small artery lesions leading to myocardial ischemia. This model may be suitable for studying pathophysiological mechanisms in chronic renicardiac syndromes.

MFAP4: a candidate biomarker for hepatic and pulmonary fibrosis?

BACKGROUND

Several comparable mechanisms have been identified for hepatic and pulmonary fibrosis. The human microfibrillar associated glycoprotein 4 (MFAP4), produced by activated myofibroblasts, is a ubiquitous protein playing a potential role in extracellular matrix (ECM) turnover and was recently identified as biomarker for hepatic fibrosis in hepatitis C patients. The current study aimed to evaluate serum levels of MFAP4 in patients with pulmonary fibrosis in order to test its potential as biomarker in clinical practice. A further aim was to determine whether MFAP4 deficiency in mice affects the formation of pulmonary fibrosis in the bleomycin model of lung fibrosis.

METHODS

91 patients with idiopathic pulmonary fibrosis (IPF), 23 with hypersensitivity pneumonitis (HP) and 31 healthy subjects were studied. In the mouse model, C57BL/6 Mfap4+/+ and Mfap4-/- mice between 6-8 weeks of age were studied. Serum levels of MFAP4 were measured by ELISA in patients and in mice. Surfactant protein D (SP-D) and LDH were measured as comparison biomarkers in patients with pulmonary fibrosis. Morphometric assessment and the Sircol kit were used to determine the amount of collagen in the lung tissue in the mouse model.

RESULTS

Serum levels of MFAP4 were not elevated in lung fibrosis - neither in the patients with IPF or HP nor in the animal model. Furthermore no significant correlations with pulmonary function tests of IPF patients could be found for MFAP4. MFAP4 levels were increased in BAL of bleomycin treated mice with pulmonary fibrosis.

CONCLUSIONS

MFAP4 is not elevated in sera of patients with pulmonary fibrosis or bleomycin treated mice with pulmonary fibrosis. This may be due to different pathogenic mechanisms of liver and lung fibrogenesis. MFAP4 seems to be useful as serum biomarker for hepatic but not for lung fibrosis.

Early reversal cells in adult human bone remodeling: osteoblastic nature, catabolic functions and interactions with osteoclasts

The mechanism coupling bone resorption and formation is a burning question that remains incompletely answered through the current investigations on osteoclasts and osteoblasts. An attractive hypothesis is that the reversal cells are likely mediators of this coupling. Their nature is a big matter of debate. The present study performed on human cancellous bone is the first one combining in situ hybridization and immunohistochemistry to demonstrate their osteoblastic nature. It shows that the Runx2 and CD56 immunoreactive reversal cells appear to take up TRAcP released by neighboring osteoclasts. Earlier preclinical studies indicate that reversal cells degrade the organic matrix left behind by the osteoclasts and that this degradation is crucial for the initiation of the subsequent bone formation. To our knowledge, this study is the first addressing these catabolic activities in adult human bone through electron microscopy and analysis of molecular markers. Periosteoclastic reversal cells show direct contacts with the osteoclasts and with the demineralized resorption debris. These early reversal cells show (1) ¾-collagen fragments typically generated by extracellular collagenases of the MMP family, (2) MMP-13 (collagenase-3) and (3) the endocytic collagen receptor uPARAP/Endo180. The prevalence of these markers was lower in the later reversal cells, which are located near the osteoid surfaces and morphologically resemble mature bone-forming osteoblasts. In conclusion, this study demonstrates that reversal cells colonizing bone surfaces right after resorption are osteoblast-lineage cells, and extends to adult human bone remodeling their role in rendering eroded surfaces osteogenic.

Incidental finding of multiple well-differentiated papillary mesotheliomas in peritoneum

We present a case of multiple well-differentiated papillary mesotheliomas (WDPM) in the peritoneum found incidentally in a 63-year-old man with urothelial carcinoma of the bladder. When multiple tumors are seen, malignant mesothelioma should be excluded by histopathological examination as this may have a similar focal appearance to WDPM. True stromal invasion is by far the most reliable criterion of mesothelial malignancy. In doubtful cases, a conservative diagnostic approach has been recommended. Compared to malignant mesotheliomas, WDPMs are rare and have a relatively indolent clinical course with a good prognosis. Great care is needed when diagnosing mesothelial proliferations, given the crucial nature of a benign vs malignant diagnosis. No standardized treatment has yet been established.

Protective effects of surfactant protein D treatment in 1,3-β-glucan-modulated allergic inflammation

Surfactant protein D (SP-D) is a pulmonary collectin important in lung immunity. SP-D-deficient mice (Sftpd(-/-)) are reported to be susceptible to ovalbumin (OVA)- and fungal allergen-induced pulmonary inflammation, while treatment with exogenous SP-D has therapeutic effects in such disease models. β-Glucans are a diverse group of polysaccharides previously suggested to serve as fungal ligands for SP-D. We set out to investigate if SP-D could interact with 1,3-β-glucan and attenuate allergic pulmonary inflammation in the presence of 1,3-β-glucan. Allergic airway disease was induced in Sftpd(-/-) and Sftpd(+/+) mice by OVA sensitization and subsequent challenge with OVA, 1,3-β-glucan, or OVA/1,3-β-glucan together. Mice in the combined treatment group were further treated with a high dose of recombinant fragment of human SP-D (rfhSP-D). We demonstrated direct interaction between SP-D and 1,3-β-glucan. OVA-induced mucous cell metaplasia was increased in Sftpd(-/-) mice, supporting previously reported protective effects of endogenous SP-D in allergy. OVA-induced parenchymal CCL11 levels and eosinophilic infiltration in bronchoalveolar lavage were unaffected by 1,3-β-glucan, but were reversed with rfhSP-D treatment. 1,3-β-Glucan treatment did, however, induce pulmonary neutrophilic infiltration and increased TNF-α levels in bronchoalveolar lavage, independently of OVA-induced allergy. This infiltration was also reversed by treatment with rfhSP-D. 1,3-β-Glucan reduced OVA-induced mucous cell metaplasia, T helper 2 cytokines, and IFN-γ production. rfhSP-D treatment further reduced mucous metaplasia and T helper 2 cytokine secretion to background levels. In summary, rfhSP-D treatment resulted in attenuation of both allergic inflammation and 1,3-β-glucan-mediated neutrophilic inflammation. Our data suggest that treatment with high-dose SP-D protects from mold-induced exacerbations of allergic asthma.

Testicular Sperm Sampling by Subcapsular Orchiectomy in Klinefelter Patients: A New Simplified Treatment Approach

OBJECTIVE

To evaluate subcapsular orchiectomy as a method to retrieve spermatozoa from minute testicular foci in men with Klinefelter syndrome (KS).

METHODS

Fourteen men with KS were consecutively recruited to unilateral subcapsular orchiectomy. Testicular tissue was dissected mechanically and enzymatically to identify possible sperm. Previous testosterone replacement therapy was interrupted for 10 months (range: 9-12 months) to minimize a possible effect on the spermatogenesis. Two men with high estrogen/testosterone ratios were treated with aromatase inhibitor (letrozol, 2.5 mg/d for 3 months) before operation.

RESULTS

Testicular sperm were detected in 5 of 14 KS men giving an overall success rate of 36%. The success rate was 50% (5 of 10 men) after exclusion of the 4 men previous treated with androgen substitution. So far, 3 (21%) clinical pregnancies and 2 live births or ongoing pregnancies (14%) have been obtained. Testicular sperm could not be detected in the 2 men treated with aromatase inhibitor before operation. The maximum operative time was 20 minutes, and none had surgical complications such as pain, fever, or hematomas. The mean testosterone level, measured 1-4 months after orchiectomy, decreased to 72% (7.9 ± 2.4 nmol/L) of the preoperative level.

CONCLUSION

Subcapsular orchiectomy appears to be easy and quick compared with conventional microtesticular sperm extraction. However, in this pilot study, it has not been possible to demonstrate pregnancy and live birth rates as high as that reported with microtesticular sperm extraction, and further studies are needed before the procedure should be used routinely for sperm retrieval in patients with KS.

The giraffe kidney tolerates high arterial blood pressure by high renal interstitial pressure and low glomerular filtration rate

BACKGROUND

The tallest animal on earth, the giraffe (Giraffa camelopardalis) is endowed with a mean arterial blood pressure (MAP) twice that of other mammals. The kidneys reside at heart level and show no sign of hypertension-related damage. We hypothesized that a species-specific evolutionary adaption in the giraffe kidney allows normal for size renal haemodynamics and glomerular filtration rate (GFR) despite a MAP double that of other mammals.

METHODS

Fourteen anaesthetized giraffes were instrumented with vascular and bladder catheters to measure glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). Renal interstitial hydrostatic pressure (RIHP) was assessed by inserting a needle into the medullary parenchyma. Doppler ultrasound measurements provided renal artery resistive index (RI). Hormone concentrations as well as biomechanical, structural and histological characteristics of vascular and renal tissues were determined.

RESULTS

GFR averaged 342 ± 99 mL min(-1) and ERPF 1252 ± 305 mL min(-1) . RIHP varied between 45 and 140 mmHg. Renal pelvic pressure was 39 ± 2 mmHg and renal venous pressure 32 ± 4 mmHg. A valve-like structure at the junction of the renal and vena cava generated a pressure drop of 12 ± 2 mmHg. RI was 0.27. The renal capsule was durable with a calculated burst pressure of 600 mmHg. Plasma renin and AngII were 2.6 ± 0.5 mIU L(-1) and 9.1 ± 1.5 pg mL(-1) respectively.

CONCLUSION

In giraffes, GFR, ERPF and RI appear much lower than expected based on body mass. A strong renal capsule supports a RIHP, which is >10-fold that of other mammals effectively reducing the net filtration pressure and protecting against the high MAP.

Ultrastructural and immunohistochemical localization of plasma membrane Ca2+-ATPase 4 in Ca2+-transporting epithelia

Plasma membrane Ca(2+)-ATPases (PMCAs) participate in epithelial Ca(2+) transport and intracellular Ca(2+) signaling. The Pmca4 isoform is enriched in distal nephron isolates and decreased in mice lacking the epithelial transient receptor potential vanilloid 5 Ca(2+) channel. We therefore hypothesized that Pmca4 plays a significant role in transcellular Ca(2+) flux and investigated the localization and regulation of Pmca4 in Ca(2+)-transporting epithelia. Using antibodies directed specifically against Pmca4, we found it expressed only in the smooth muscle layer of mouse and human intestines, whereas pan-specific Pmca antibodies detected Pmca1 in lateral membranes of enterocytes. In the kidney, Pmca4 showed broad localization to the distal nephron. In the mouse, expression was most abundant in segments coexpressing the epithelial ransient receptor potential vanilloid 5 Ca(2+) channel. Significant, albeit lower, expression was also evident in the region encompassing the cortical thick ascending limbs, macula densa, and early distal tubules as well as smooth muscle layers surrounding renal vessels. In the human kidney, a similar pattern of distribution was observed, with the highest PMCA4 expression in Na(+)-Cl(-) cotransporter-positive tubules. Electron microscopy demonstrated Pmca4 localization in distal nephron cells at both the basolateral membrane and intracellular perinuclear compartments but not submembranous vesicles, suggesting rapid trafficking to the plasma membrane is unlikely to occur in vivo. Pmca4 expression was not altered by perturbations in Ca(2+) balance, pointing to a housekeeping function of the pump in Ca(2+)-transporting epithelia. In conclusion, Pmca4 shows a divergent expression pattern in Ca(2+)-transporting epithelia, inferring diverse roles for this isoform not limited to transepithelial Ca(2+) transport.