Maarten B. Rookmaaker

Bone-Marrow-Derived Cells Contribute to Glomerular Endothelial Repair in Experimental Glomerulonephritis

Glomerular endothelial injury plays an important role in the pathogenesis of renal diseases and is centrally involved in renal disease progression. Glomerular endothelial repair may help maintain renal function. We examined whether bone-marrow (BM)-derived cells contribute to glomerular repair. A rat allogenic BM transplant model was used to allow tracing of BM-derived cells using a donor major histocompatibility complex class-I specific mAb. In glomeruli of chimeric rats we identified a small number of donor-BM-derived endothelial and mesangial cells, which increased in a time-dependent manner. Induction of anti-Thy-1.1-glomerulonephritis (transient mesangial and secondary glomerular endothelial injury) caused a significant, more than fourfold increase in the number of BM-derived glomerular endothelial cells at day 7 after anti-Thy-1.1 injection compared to chimeric rats without glomerular injury. The level of BM-derived endothelial cells remained high at day 28. We also observed a more than sevenfold increase in the number of BM-derived mesangial cells at day 28. BM-derived endothelial and mesangial cells were fully integrated in the glomerular structure. Our data show that BM-derived cells participate in glomerular endothelial and mesangial cell turnover and contribute to microvascular repair. These findings provide novel insights into the pathogenesis of renal disease and suggest a potential role for stem cell therapy.

Lgr5+ve Stem/Progenitor Cells Contribute to Nephron Formation during Kidney Development

Multipotent stem cells and their lineage-restricted progeny drive nephron formation within the developing kidney. Here, we document expression of the adult stem cell marker Lgr5 in the developing kidney and assess the stem/progenitor identity of Lgr5(+ve) cells via in vivo lineage tracing. The appearance and localization of Lgr5(+ve) cells coincided with that of the S-shaped body around embryonic day 14. Lgr5 expression remained restricted to cell clusters within developing nephrons in the cortex until postnatal day 7, when expression was permanently silenced. In vivo lineage tracing identified Lgr5 as a marker of a stem/progenitor population within nascent nephrons dedicated to generating the thick ascending limb of Henles loop and distal convoluted tubule. The Lgr5 surface marker and experimental models described here will be invaluable for deciphering the contribution of early nephron stem cells to developmental defects and for isolating human nephron progenitors as a prerequisite to evaluating their therapeutic potential.

Eligibility for percutaneous renal denervation: the importance of a systematic screening.

Objective: Percutaneous renal denervation (pRDN) is a new and promising therapy for resistant hypertension. Among patients suspected of having resistant hypertension, the actual presence of this condition needs to be well established; pseudoresistant hypertension and significant white-coat effect (WCE) should be excluded. This analysis presents the results of a standardized screening programme for patients referred for pRDN. Methods: All patients referred to our centre for pRDN underwent a standardized stepwise screening and were subsequently discussed in a multidisciplinary team. The screening included a 24-h ambulatory blood pressure measurement (ABPM), collection of plasma, urine and saliva, and finally imaging of the renal arteries. Results: From August 2010 till October 2012, 181 patients were referred for pRDN. Mean blood pressure (BP) was 182/100 mmHg, and median use was three antihypertensives. Ultimately, 121 patients (67%) were excluded from pRDN. Main reasons for exclusion were BP-related. Twenty-three patients (19%) had an office SBP less than 160 mmHg and 26 patients (22%) showed a WCE. Fourteen patients (12%) had a so far undetected underlying cause of hypertension, the majority being primary aldosteronism (n = 11). Nine patients had an ineligible renal anatomy. Conclusion: A high percentage of patients were excluded from treatment with pRDN due to secondary causes of hypertension, WCE or a BP below the currently advised thresholds. Treatment of these excluded patients would lead to inappropriate use of pRDN, leading most likely to little benefit for the patients and a burden to healthcare. Therefore, it is recommended to use a standardized screening before treatment with pRDN.

Endothelial Progenitor Cells: Mainly Derived From the Monocyte/Macrophage–Containing CD34− Mononuclear Cell Population and Only in Part From the Hematopoietic Stem Cell–Containing CD34+ Mononuclear Cell Population

To the Editor: In their very interesting paper, Rehman et al1 demonstrate that the vast majority of peripheral blood–derived acLDL+ Ulex-lectin+ cells in culture—often referred to as endothelial progenitor cells (EPC)—express monocyte/macrophage markers, indicating that they originate mainly from the monocyte/macrophage lineage. They suggest that only a small population of true stem cells/progenitor cells and endothelial cells exists that may originate directly from the hemangioblast or from hematopoietic stem cells. Our recent observations support their findings that the majority of EPC are derived from the monocyte/macrophage–containing CD34− mononuclear cell population. Nevertheless, we could also identify and quantify a minor proportion of EPC that has its origin in the hematopoietic stem …

CD34+ Cells Home, Proliferate, and Participate in Capillary Formation, and in Combination With CD34− Cells Enhance Tube Formation in a 3-Dimensional Matrix

Objective—Emerging evidence suggests that human blood contains bone marrow (BM)-derived endothelial progenitor cells that contribute to postnatal neovascularization. Clinical trials demonstrated that administration of BM-cells can enhance neovascularization. Most studies, however, used crude cell populations. Identifying the role of different cell populations is important for developing improved cellular therapies. Methods and Results—Effects of the hematopoietic stem cell–containing CD34+ cell population on migration, proliferation, differentiation, stimulation of, and participation in capillary-like tubule formation were assessed in an in vitro 3-dimensional matrix model using human microvascular endothelial cells. During movement over the endothelial monolayer, CD34+ cells remained stuck at sites of capillary tube formation and time- and dose-dependently formed cell clusters. Immunohistochemistry confirmed homing and proliferation of CD34+ cells in and around capillary sprouts. CD34+ cells were transduced with the LNGFR marker gene to allow tracing. LNGFR gene–transduced CD34+ cells integrated in the tubular structures and stained positive for CD31 and UEA-1. CD34+ cells alone stimulated neovascularization by 17%. Coculture with CD34− cells led to 68% enhancement of neovascularization, whereas CD34− cells displayed a variable response by themselves. Cell–cell contact between CD34+ and CD34− cells facilitated endothelial differentiation of CD34+ cells. Conclusions—Our data suggest that administration of CD34+-enriched cell populations may significantly improve neovascularization and point at an important supportive role for (endogenous or exogenous) CD34− cells.

Development and application of human adult stem or progenitor cell organoids

Adult stem or progenitor cell organoids are 3D adult-organ-derived epithelial structures that contain self-renewing and organ-specific stem or progenitor cells as well as differentiated cells. This organoid culture system was first established in murine intestine and subsequently developed for several other organs and translated to humans. Organoid cultures have proved valuable for basic research and for the study of healthy tissue homeostasis and the biology of disease. In addition, data from proof-of-principle experiments support promising clinical applications of adult stem or progenitor cell organoids. Although renal organoids have many potential applications, an adult stem or progenitor cell organoid culture system has not yet been developed for the kidney. The development of such a system is likely to be challenging because of the intricate renal architecture. Differentiated 3D cultures and stem or progenitor cell 3D sphere cultures are, however, available for the kidney. These cultures indicate the feasibility of renal organoid culture and provide a solid basis for its development. In this Review, we discuss the state-of-the-art of human adult stem or progenitor cell organoid culture and the potential of renal organoids as tools in basic and clinical research.

RANTES is required for ischaemia-induced angiogenesis, which may hamper RANTES-targeted anti-atherosclerotic therapy.

RANTES is required for ischaemia-induced angiogenesis, which may hamper RANTES-targeted anti-atherosclerotic therapy -

Solid renal tumours of collecting duct origin in patients on chronic lithium therapy

Background Lithium (Li) is an invaluable drug for the treatment of bipolar disorder. Long-term Li use is associated with renal complications including the formation of uncomplicated renal cysts caused by proliferation and expansion of collecting duct (CD) cells. We report six patients with complicated renal cysts in the context of Li nephropathy. Methods Over a time period of 15 years, we have identified six patients with one or more solid renal tumours in our population of approximately 50 patients with chronic Li nephropathy. In this study we describe the clinical and pathological characteristics of these Li-related tumours. Results All patients were on Li therapy for over 10 years and suffered from varying degrees of Li nephropathy. The tumours were all of CD origin and comprised both oncocytomas and collecting duct carcinomas. The CD carcinomas differed from the very rare “classical” CD cell carcinomas in histological appearance, multifocal presentation and non-aggressive clinical behaviour Conclusions The increased incidence of CD derived tumours and atypical presentation of CD cell carcinomas in patients with chronic Li nephropathy suggests that Li predisposes to the development of these tumours. We hypothesize that prolonged stimulation of CD cell proliferation and expansion by Li not only causes cyst formation, but can eventually induce the formation of adenomas and carcinomas. Increased awareness of a possible relationship between chronic Li therapy and renal neoplasms, will enhance the knowledge on epidemiology, clinical behavior and optimal therapy for the Li-related renal neoplasms.

Pluripotent stem cell-derived kidney organoids: An in vivo-like in vitro technology.

Organoids are self-organizing, multicellular structures that contain multiple cell types, represent organ structure and function, and can be used to model organ development, maintenance and repair ex vivo. Organoids, derived from embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) or adult stem cells, are cultured in extracellular matrix (ECM). Organoid cultures have been developed for multiple organs and for the kidney, pluripotent stem cell (PSCs) derived organoid technology has rapidly developed in the last three years. Here, we review available PSC differentiation protocols, focusing on the pluripotent stem cells to initiate the organoid culture, as well as on growth factors and ECM used to regulate differentiation and expansion. In addition, we will discuss the read out strategies to evaluate organoid phenotype and function. Finally, we will indicate how the choice of both culture parameters and read out strategy should be tailored to specific applications of the organoid culture.

ACE Inhibition in Anti-Thy1 Glomerulonephritis Limits Proteinuria but Does Not Improve Renal Function and Structural Remodeling.

Background/Aims: ACE inhibitor (ACE-I) treatment effectively inhibits proteinuria and ameliorates the course of various renal diseases. In experimental glomerulonephritis, however, angiotensin II (AngII) infusion has also been shown to be renoprotective. We evaluated the long-term (28 days) course of anti-Thy1 glomerulonephritis in animals with suppressed AngII formation by ACE-I treatment. Methods: Brown Norway rats received perindopril (2.8 mg/kg/day, n = 12), dihydropyridine calcium-antagonist amlodipine (Ca-A; 13 mg/kg/day, n = 6) or were left untreated (n = 14). All animals were monitored for blood pressure, proteinuria, and creatinine clearance after anti-Thy1 injection. Renal histology was assessed at day 7 and 28. Results: Systolic blood pressure was equally reduced by ACE-I and Ca-A treatment. AngII suppression prevented development of proteinuria, but did not protect against glomerular microaneurysm formation or reduction in creatinine clearance. After resolution of the microaneurysms, animals with suppressed AngII production showed a modest increase in glomerulosclerosis and vasculopathic thickening of intrarenal vessels. Conclusions: In anti-Thy1 glomerulonephritis, suppression of AngII formation does not protect against the induction of glomerular damage and is associated with mild aggravation of adverse renal fibrotic remodeling. Proteinuria, however, is effectively prevented by ACE-I treatment. Ca-A treatment did not affect the course of glomerulonephritis, indicating that ACE-I effects are blood pressure independent.