No abstract

The podocyte is one of the two cell types that contribute to the formation of the glomerular filtration barrier (GFB). It is a highly specialized cell with a unique structure. The key feature of the podocyte is its foot processes that regularly interdigitate. A structure known as the slit diaphragm can be found bridging the interdigitations. This molecular sieve comprises the final layer of the GFB. It is well accepted that the podocyte is the target cell in the pathogenesis of nephrotic syndrome. In nephrotic syndrome, the GFB no longer restricts the passage of macromolecules and protein is lost into the urine. A number of phenotypic and morphological changes are seen in the diseased podocyte and in the literature these have been described as an epithelial–mesenchymal transition (EMT). However, there is a growing appreciation that this term does not accurately describe the changes that are seen. Definitions of type-2 EMT are based on typical epithelial cells. While the podocyte is known as a visceral epithelial cell, it is not a typical epithelial cell. Moreover, podocytes have several features that are more consistent with mesenchymal cells. Therefore, we suggest that the term podocyte disease transformation is more appropriate.

The specific pathogenesis of idiopathic nephrotic syndrome (NS) is poorly understood, and the role of immune mediators remains contentious. However, there is good evidence for the role of a circulating factor, and we recently postulated circulating proteases as candidate factors. Immunosuppressive therapy with glucocorticoids (GCs) and T cell inhibitors are widely used in the clinical treatment of NS. Given that T helper (CD4+) cells expressing IL-17A (so-called Th17 cells) have recently been reported to be resistant to GC treatment, and GC resistance remains a major challenge in the management of NS, we hypothesized that Th17 cells produce a circulating factor that is capable of signaling to the podocyte and inducing deleterious phenotypic changes. To test this, we generated human Th17 cells from healthy volunteers and added the supernatants from these T cell cultures to conditionally immortalized human podocytes in vitro. This demonstrated that podocytes treated with Th17 cell culture supernatant, as well as with patient disease plasma, showed significant stimulation of JNK and p38 MAPK pathways and an increase in motility, which was blocked using a JNK inhibitor. We have previously shown that nephrotic plasma elicits a podocyte response via protease-activated receptor-1 (PAR-1). Stimulation of PAR-1 in podocytes elicited the same signaling response as Th17 cell culture supernatant treatment. Equally, protease inhibitors with Th17 cell culture treatment blocked the signaling response. This was not replicated by the reagents added to Th17 cell cultures or by IL-17A. Hence, we conclude that an undefined soluble mediator produced by Th17 cells mimics the deleterious effect of PAR-1 activation in vitro. Given the association between pathogenic subsets of Th17 cells and GC resistance, these observations have potential therapeutic relevance for patients with NS.

SUMMARY The paper is based on 595 foetal electrocardiograph traces, made from 33 mares. Foetal electrocardiography is a simple technique for the detection of singleton and twin pregnancies. It is also of value for monitoring foetuses in difficult or induced parturitions, and in circumstances where positive evidence of a live foetus is required. Although the foetal heart rate shows periods of intermittent tachycardia, the mean foetal heart rate decreases and mean maternal heart rate increases gradually from 150 days gestation to term. The foetal heart rate in the first stage of induced parturition is found to be related to the duration of first stage labour. Foetal cardiac arrhythmia is most common in abnormal pregnancies. Tachycardia, followed by bradycardia, with slurring of the foetal QRS complex has been seen in a dying foetus. The amplitude of the foetal electrocardiograph (FECG) may vary considerably and rapidly, with the mean amplitude increasing from 150 days to term. Between 220 and 280 days a period of increased variance above and below the mean occurs, lasting for about 3 weeks for any individual animal. Changes in polarity of the foetal deflection are frequent, and may be due to vector changes arising in the myocardium, as well as to differences in foetal position. No positive deflections were recorded from mule foetuses before 300 days. RÉSUMÉ 595 ECG foetaux ont été enregistrés sur 33 juments. L'ECG foetal offre une méthode simple de diagnostic des gémelliparités avancées. II est également utile pour surveiller les foetus en difficulté ou lors de mises bas provoquées et dans les circonstances où l'on souhaite vérifier la présence d'un foetus en vie. Le rythme cardiaque foetal peut montrer des périodes de tachycardie transitoire. Mais d'une manière plus générale on constate qu'à partir de 150 jours de gestation jusqu'au terme, le rythme foetal moyen décroit comme celui de la poulinière s'accélère. Le rythme cardiaque foetal lors de mise bas provoquée parait être en relation avec la durée de la première phase du poulinage. Des arythmies cardiaques foetales sont fréquentes lors des gestations anormales. On a rencontré chez un foetus agonisant une tachycardie suivie par une bradycardie avec étalement du complexe QRS. L'amplitude de l'ECG foetal peut varier considérablement et rapidement. L'amplitude moyenne s'accroit de 150 jours au terme. Entre 220 et 280 jours une période de variations marquées au dessous et au dessus de la moyenne a été constatée: elle dure environ 3 semaines pour chaque individu. Les changements de polarité des déflexions foetales sont fréquentes, dûs sans douteà des modifications du vecteur myocardique età des variations dans la position du foetus. Aucune déflexion positive n'a pu être enregistrée sur le mulet foetal avant 300 jours de gestation. ZUSAMMENFASSUNG Dieser Artikel bezieht sich auf 595 Aufnahmen foetaler Elektrocardiogramme bei 35 Stuten. Die foetale Elektrocardiographie ist eine einfache Methode zur Erkennung von Einlings‐ oder Zwillingsträchtigkeiten. Sie ist auch wert...

Background: Understanding podocyte biology is key to deciphering the pathogenesis of numerous glomerular diseases. However, cultivation of primary podocytes results in de-differentiation with loss of specialised architecture. Human conditionally immortalised podocytes partly overcome this problem, utilising a temperature-sensitive transgene. Conditionally immortalised murine podocytes exist, but are derived from the Immortomouse. Methods: Using retroviral temperature-sensitive SV40 transfection, we created a conditionally immortalised podocyte cell line from wild-type mice. Results: These cells develop characteristic mature podocyte morphology and robustly express slit diaphragm proteins. Functionally, these cells demonstrate comparable responses in motility and glucose uptake to human conditionally immortalised podocytes. Conclusion: Podocyte-specific transgenic mice are extensively used to study glomerular disease and this technique could be used to make podocyte cell lines from any mouse, allowing study at the cellular level. This will help characterise these disease models and add to the laboratory resources used to study podocytopathies and glomerular disease.