Continuity With Patients, Preceptors, and Peers Improves Primary Care Training: A Randomized Medical Education Trial

PURPOSE

Infusing continuity of care into medical student clerkships may accelerate professional development, preserve patient-centered attitudes, and improve primary care training. However, prospective, randomized studies of longitudinal curricula are lacking.

METHOD

All entering Northwestern University Feinberg School of Medicine students in 2015 and 2016 were randomized to the Education Centered Medical Home (ECMH), a 4-year, team-based primary care clerkship; or a mentored individual preceptorship (IP) for 2 years followed by a traditional 4-week primary care clerkship. Students were surveyed 4 times (baseline, M1, M2, and M3 year [through 2018]); surveys included the Maslach Burnout Inventory (MBI); the Communication, Curriculum, and Culture (C3) survey assessing the hidden curriculum; and the Attitudes Toward Health Care Teams (ATHCT) scale. The authors analyzed results using an intent-to-treat approach.

RESULTS

Three hundred twenty-nine students were randomized; 316 (96%) participated in surveys. Seventy percent of all respondents would recommend the ECMH to incoming first-year students. ECMH students reported a more positive learning environment (overall quality, 4.4 ECMH vs 4.0 IP, P < .001), greater team-centered attitudes (ATHCT scale, 3.2 vs 3.0, P = .007), less exposure to negative aspects of the hidden curriculum (C3 scale, 4.6 vs 4.3, P < .001), and comparable medical knowledge acquisition. ECMH students established more continuity relationships with patients (2.2 vs 0.3, P < .001) and reported significantly higher professional efficacy (MBI-PE, 4.1 vs 3.9, P = .02).

CONCLUSIONS

In this randomized medical education trial, the ECMH provided superior primary care training across multiple outcomes compared with a traditional clerkship-based model, including improved professional efficacy.

Origin and functional heterogeneity of fibroblasts

The inherent plasticity and resiliency of fibroblasts make this cell type a conventional tool for basic research. But where do they come from, are all fibroblasts the same, and how do they function in disease? The first fibroblast lineages in mammalian development emerge from the ooze of primary mesenchyme during gastrulation. They are cells that efficiently create and negotiate the extracellular matrix of the mesoderm in order to migrate and meet their developmental fate. Mature fibroblasts in epithelial tissues live in the interstitial spaces between basement membranes that spatially delimit complex organ structures. While the function of resident fibroblasts in healthy tissues is largely conjecture, the accumulation of fibroblasts in pathologic lesions offers insight into biologic mechanisms that control their function; fibroblasts are poised to coordinate fibrogenesis in tissue injury, neoplasia, and aging. Here, we examine the developmental origin and plasticity of fibroblasts, their molecular and functional definitions, the epigenetic control underlying their identity and activation, and the evolution of their immune regulatory functions. These topics are reviewed through the lens of fate mapping using genetically engineered mouse models and from the perspective of single-cell RNA sequencing. Recent observations suggest dynamic and heterogeneous functions for fibroblasts that underscore their complex molecular signatures and utility in injured tissues.

S100A4 Is a Biomarker and Regulator of Glioma Stem Cells That Is Critical for Mesenchymal Transition in Glioblastoma

Glioma stem cells (GSC) and epithelial-mesenchymal transition (EMT) are strongly associated with therapy resistance and tumor recurrence, but the underlying mechanisms are incompletely understood. Here, we show that S100A4 is a novel biomarker of GSCs. S100A4⁺ cells in gliomas are enriched with cancer cells that have tumor-initiating and sphere-forming abilities, with the majority located in perivascular niches where GSCs are found. Selective ablation of S100A4-expressing cells was sufficient to block tumor growth in vitro and in vivo We also identified S100A4 as a critical regulator of GSC self-renewal in mouse and patient-derived glioma tumorspheres. In contrast with previous reports of S100A4 as a reporter of EMT, we discovered that S100A4 is an upstream regulator of the master EMT regulators SNAIL2 and ZEB along with other mesenchymal transition regulators in glioblastoma. Overall, our results establish S100A4 as a central node in a molecular network that controls stemness and EMT in glioblastoma, suggesting S100A4 as a candidate therapeutic target. Cancer Res; 77(19); 5360-73. ©2017 AACR.

Phosphatidylinositol 3-kinase signaling determines kidney size

Kidney size adaptively increases as mammals grow and in response to the loss of 1 kidney. It is not clear how kidneys size themselves or if the processes that adapt kidney mass to lean body mass also mediate renal hypertrophy following unilateral nephrectomy (UNX). Here, we demonstrated that mice harboring a proximal tubule-specific deletion of Pten (Pten(ptKO)) have greatly enlarged kidneys as the result of persistent activation of the class I PI3K/mTORC2/AKT pathway and an increase of the antiproliferative signals p21(Cip1/WAF) and p27(Kip1). Administration of rapamycin to Pten(ptKO) mice diminished hypertrophy. Proximal tubule-specific deletion of Egfr in Pten(ptKO) mice also attenuated class I PI3K/mTORC2/AKT signaling and reduced the size of enlarged kidneys. In Pten(ptKO) mice, UNX further increased mTORC1 activation and hypertrophy in the remaining kidney; however, mTORC2-dependent AKT phosphorylation did not increase further in the remaining kidney of Pten(ptKO) mice, nor was it induced in the remaining kidney of WT mice. After UNX, renal blood flow and amino acid delivery to the remaining kidney rose abruptly, followed by increased amino acid content and activation of a class III PI3K/mTORC1/S6K1 pathway. Thus, our findings demonstrate context-dependent roles for EGFR-modulated class I PI3K/mTORC2/AKT signaling in the normal adaptation of kidney size and PTEN-independent, nutrient-dependent class III PI3K/mTORC1/S6K1 signaling in the compensatory enlargement of the remaining kidney following UNX.

EGFR signaling promotes TGFβ-dependent renal fibrosis

The mechanisms by which angiotensin II (Ang II) promotes renal fibrosis remain incompletely understood. Ang II both stimulates TGFβ signaling and activates the EGF receptor (EGFR), but the relative contribution of these pathways to renal fibrogenesis is unknown. Using a murine model with EGFR-deficient proximal tubules, we demonstrate that upstream activation of EGFR-dependent ERK signaling is critical for mediating sustained TGFβ expression in renal fibrosis. Persistent activation of the Ang II receptor stimulated ROS-dependent phosphorylation of Src, leading to sustained EGFR-dependent signaling for TGFβ expression. Either genetic or pharmacologic inhibition of EGFR significantly decreased TGFβ-mediated fibrogenesis. We conclude that TGFβ-mediated tissue fibrosis relies on a persistent feed-forward mechanism of EGFR/ERK activation through an unexpected signaling pathway, highlighting EGFR as a potential therapeutic target for modulating tissue fibrogenesis.

Body fluid dynamics: back to the future

Pioneering investigations conducted over a half century ago on tonicity, transcapillary fluid exchange, and the distribution of water and solute serve as a foundation for understanding the physiology of body fluid spaces. With passage of time, however, some of these concepts have lost their connectivity to more contemporary information. Here we examine the physical forces determining the compartmentalization of body fluid and its movement across capillary and cell membrane barriers, drawing particular attention to the interstitium operating as a dynamic interface for water and solute distribution rather than as a static reservoir. Newer work now supports an evolving model of body fluid dynamics that integrates exchangeable Na(+) stores and transcapillary dynamics with advances in interstitial matrix biology.

Effect of recommendations from reviewers suggested or excluded by authors

The Journal of the American Society of Nephrology (JASN) gives authors submitting original research the option of suggesting qualified reviewers or those they wish to exclude. This historical habit often leaves us wondering whether author preferences correlate with reviewer recommendations and whether differences related to reviewer selection affect decisions by editors. In a self-study presented here, we found that author-suggested reviewers, as a group, make more positive recommendations than editor-suggested reviewers (P = 0.01), although the difference disappears when recommendations are compared with those of editor-suggested reviewers of the same manuscript (P = 0.081). The distribution of recommendations by author-excluded reviewers, as a group, did not differ from those by editor-suggested reviewers; however, author-excluded reviewers impart significantly more negative recommendations than other reviewers of the same manuscript (P = 0.029). We further explored whether such differences result from individual reviewer tendencies to give generally more positive or more negative recommendations than editor-suggested reviewers and found no such tendency. Finally, editorial decisions on manuscripts reviewed by author-suggested or author-excluded reviewers do not differ from those decisions on manuscripts assigned but not reviewed by them. JASN's policy of editors making decisions independent from individual reviewer recommendations minimizes the effect of selection bias on publication decisions.

Volume depletion versus dehydration: how understanding the difference can guide therapy

Although often used interchangeably, dehydration and volume depletion are not synonyms. Dehydration refers to loss of total-body water, producing hypertonicity, which now is the preferred term in lieu of dehydration, whereas volume depletion refers to a deficit in extracellular fluid volume. In particular, hypertonicity implies intracellular volume contraction, whereas volume depletion implies blood volume contraction. Using a case of hyperglycemic hypertonic nonketosis as an example, we examine the changing composition of body fluid spaces to explore the distinction between dehydration and hypertonicity from volume depletion.

Mechanisms of tubulointerstitial fibrosis

The pathologic paradigm for renal progression is advancing tubulointerstitial fibrosis. Whereas mechanisms underlying fibrogenesis have grown in scope and understanding in recent decades, effective human treatment to directly halt or even reverse fibrosis remains elusive. Here, we examine key features mediating the molecular and cellular basis of tubulointerstitial fibrosis and highlight new insights that may lead to novel therapies. How to prevent chronic kidney disease from progressing to renal failure awaits even deeper biochemical understanding.

Fibroblast expression of an IκB dominant-negative transgene attenuates renal fibrosis

It is not clear whether interstitial fibroblasts or tubular epithelial cells are primarily responsible for the profibrotic effects of NF-κB activation during renal fibrogenesis. Here, we crossed mice carrying a conditional IκB dominant-negative transgene (IκBdN) with mice transgenic for cell-specific FSP1.Cre (FSP1(+) fibroblasts) or γGT.Cre (proximal tubular epithelia) and challenged all progeny with unilateral ureteral obstruction. We determined NF-κB activation by nuclear localization of phosphorylated p65 ((p)p65) in renal tissues after 7 days. We observed inhibition of NF-κB activation in interstitial cells and tubular epithelia in obstructed kidneys of FSP1.Cre;IκBdN and γGT.Cre;IκBdN mice, respectively, compared with IκBdN controls (P < 0.05). Deposition of extracellular matrix, however, was significantly lower in the obstructed kidneys of FSP1.Cre;IκBdN mice but not in γGT.Cre;IκBdN mice (P < 0.05). In addition, levels of mRNA encoding the profibrotic PAI-1, fibronectin-EIIIA, and type I (α1) procollagen were significantly lower in obstructed kidneys of FSP1.Cre;IκBdN mice compared with γGT.Cre;IκBdN mice (P < 0.05). Taken together, these data support a profibrotic role for fibroblasts, but not proximal tubular epithelial cells, in modulating NF-κB activation during renal fibrogenesis.

Molecular architecture of the Goodpasture autoantigen in anti-GBM nephritis

BACKGROUND

In Goodpasture's disease, circulating autoantibodies bind to the noncollagenous-1 (NC1) domain of type IV collagen in the glomerular basement membrane (GBM). The specificity and molecular architecture of epitopes of tissue-bound autoantibodies are unknown. Alport's post-transplantation nephritis, which is mediated by alloantibodies against the GBM, occurs after kidney transplantation in some patients with Alport's syndrome. We compared the conformations of the antibody epitopes in Goodpasture's disease and Alport's post-transplantation nephritis with the intention of finding clues to the pathogenesis of anti-GBM glomerulonephritis.

METHODS

We used an enzyme-linked immunosorbent assay to determine the specificity of circulating autoantibodies and kidney-bound antibodies to NC1 domains. Circulating antibodies were analyzed in 57 patients with Goodpasture's disease, and kidney-bound antibodies were analyzed in 14 patients with Goodpasture's disease and 2 patients with Alport's post-transplantation nephritis. The molecular architecture of key epitope regions was deduced with the use of chimeric molecules and a three-dimensional model of the alpha345NC1 hexamer.

RESULTS

In patients with Goodpasture's disease, both autoantibodies to the alpha3NC1 monomer and antibodies to the alpha5NC1 monomer (and fewer to the alpha4NC1 monomer) were bound in the kidneys and lungs, indicating roles for the alpha3NC1 and alpha5NC1 monomers as autoantigens. High antibody titers at diagnosis of anti-GBM disease were associated with ultimate loss of renal function. The antibodies bound to distinct epitopes encompassing region E(A) in the alpha5NC1 monomer and regions E(A) and E(B) in the alpha3NC1 monomer, but they did not bind to the native cross-linked alpha345NC1 hexamer. In contrast, in patients with Alport's post-transplantation nephritis, alloantibodies bound to the E(A) region of the alpha5NC1 subunit in the intact hexamer, and binding decreased on dissociation.

CONCLUSIONS

The development of Goodpasture's disease may be considered an autoimmune "conformeropathy" that involves perturbation of the quaternary structure of the alpha345NC1 hexamer, inducing a pathogenic conformational change in the alpha3NC1 and alpha5NC1 subunits, which in turn elicits an autoimmune response. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases.)

The Jeremiah Metzger lecture. The origin of fibroblasts and the terminality of epithelial differentiation

For 142 years the fibroblast has lived a nomadian existence among the interstitial spaces of the metazoan body plan. The cell surface of fibroblasts lacks specific identifying markers and its parental lineage has been shrouded in mystery. Over the last 15 years much has changed. We know now that fibroblasts derive from non-motile epithelial or endothelial cells through a process called epithelial-mesenchymal transition (EMT). In this lecture I discuss the mechanisms of EMT producing fibroblasts, and the inevitable conclusion that epithelia and endothelia, rather than being terminally differentiated, are in a state of nuclear diapause and ready to change phenotype in response to the demands of tissue repair.

Abstract B23: Distinct roles for cancer-associated fibroblasts in breast cancer progression and metastasis

Cancer-associated fibroblasts (CAFs) are commonly identified and studied as an alpha-smooth muscle actin positive (αSMA+) population of myofibroblasts. However, recent work from our laboratory has shown that there are CAFs in the tumor microenvironment, which do not express αSMA. Most notably, fibroblast specific protein 1 (FSP1) marks a population of CAFs distinct from αSMA+ CAFs, as 90% of FSP1+ CAFs in the tumor microenvironment of the 4T1 murine breast cancer model are αSMA-negative. The functional heterogeneity of these subpopulations of CAFs remains unexplored. By using transgenic mice, which express viral thymidine kinase under control of the CAF promoters αSMA or FSP1 to selectively ablate either αSMA+ CAFs or FSP1+ CAFs in the context of breast cancer, we have identified distinct roles for the two CAF subpopulations in tumorigenesis and metastasis. While αSMA+ CAFs play a role in primary tumor growth and angiogenesis without affecting metastasis, FSP1+ CAFs do not contribute to primary tumor progression but facilitate the formation of macrometastases.

Citation Information: Cancer Res 2009;69(23 Suppl):B23.

Dystroglycan in the diagnosis of FSGS

BACKGROUND AND OBJECTIVES

alpha- and beta-dystroglycan (DG), which link the actin cytoskeleton of the podocyte to the glomerular basement membrane, are maintained in FSGS but decreased in minimal change disease (MCD). Fibrosis has been linked to increased fibroblast-specific protein-1 (FSP1) and epithelial-mesenchymal transition. We studied DG, FSP1, and podocyte differentiation in FSGS variants and cases of suspected FSGS.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied renal biopsies with FSGS, not otherwise specified (NOS), tip lesion, or collapsing variants (COLL), versus secondary FSGS or cases without segmental sclerotic lesions where a diagnosis of MCD versus FSGS could not be established (undefined [UNDEF]) and compared the expression of DG, FSP1, and podocyte Wilms' tumor antigen (WT1).

RESULTS

WT1 is markedly decreased in NOS versus normal and correlates with the extent of sclerosis. alpha- and beta-DG are maintained in most primary and secondary FSGS cases. In contrast, alpha-DG is significantly decreased in UNDEF, supporting a diagnosis of MCD. Furthermore, follow-up shows remission or decreased proteinuria in four of six of these UNDEF cases in response to therapy. Interstitial FSP1 is numerically highest in COLL but is only rarely found in tubules or podocytes in any other forms of FSGS.

CONCLUSIONS

We conclude that increased FSP1 may be a marker of the aggressive course of collapsing FSGS. Furthermore, DG staining is a useful adjunct to assist in distinction of FSGS versus MCD in biopsies without defining lesions.

Epithelial-mesenchymal transition as a potential explanation for podocyte depletion in diabetic nephropathy

BACKGROUND

Depletion of glomerular podocytes is an important feature of progressive diabetic nephropathy. Although the most plausible explanation for this podocyte depletion is detachment from the glomerular basement membrane after cellular apoptosis, the mechanism is unclear. Fibroblast-specific protein 1 (FSP1; encoded by the S100A4 gene) is a member of the S100 family of calcium-binding proteins and is constitutively expressed in the cytoplasm of tissue fibroblasts or epithelial cells converted into fibroblasts by means of epithelial-mesenchymal transition.

STUDY DESIGN

Retrospective cross-sectional analysis.

SETTINGS & PARTICIPANTS

109 patients with type 2 diabetes mellitus, of whom 43 (39%) underwent kidney biopsy.

PREDICTOR

Clinical stage (4 categories) and histological grade (5 categories) of diabetic nephropathy.

OUTCOME

FSP1 expression in podocytes in urine and glomeruli in kidney biopsy specimens.

MEASUREMENTS

Immunohistochemistry, real-time polymerase chain reaction, and in situ hybridization.

RESULTS

38 of 109 patients (35%) were normoalbuminuric, 16 (15%) had microalbuminuria, 8 (7%) had macroalbuminuria, and 47 (43%) had decreased kidney function. Approximately 95% of podocytes in urine sediment were not apoptotic, and 86% expressed FSP1. The number of FSP1-positive podocytes in urine sediment was significantly larger in patients with macroalbuminuria than in those with normoalbuminuria (P = 0.03). Intraglomerular expression of FSP1 occurred almost exclusively in podocytes from patients with diabetes, and the number of FSP1-positive podocytes was larger in glomeruli showing diffuse mesangiopathy than in those showing focal mesangiopathy (P = 0.01). The number also was larger in glomeruli with nodular lesions than in those without nodular lesions (P < 0.001). FSP1-positive podocytes selectively expressed Snail1 and integrin-linked kinase, a known trigger for epithelial-mesenchymal transition.

LIMITATIONS

Nonrepresentative study population.

CONCLUSIONS

These results suggest that the appearance of FSP1 in podocytes of patients with diabetes is associated with more severe clinical and pathological findings of diabetic nephropathy, perhaps because of induction of podocyte detachment through epithelial-mesenchymal transition-like phenomena.

Contribution of epithelial-derived fibroblasts to bleomycin-induced lung fibrosis

RATIONALE

Lung fibroblasts are key mediators of fibrosis resulting in accumulation of excessive interstitial collagen and extracellular matrix, but their origins are not well defined.

OBJECTIVES

We aimed to elucidate the contribution of lung epithelium-derived fibroblasts via epithelial-mesenchymal transition (EMT) in the intratracheal bleomycin model.

METHODS

Primary type II alveolar epithelial cells were cultured from Immortomice and exposed to transforming growth factor-beta(1) and epidermal growth factor. Cell fate reporter mice that permanently mark cells of lung epithelial lineage with beta-galactosidase were developed to study EMT, and bone marrow chimeras expressing green fluorescent protein under the control of the fibroblast-associated S100A4 promoter were generated to examine bone marrow-derived fibroblasts. Mice were given intratracheal bleomycin (0.08 unit). Immunostaining was performed for S100A4, beta-galactosidase, green fluorescent protein, and alpha-smooth muscle actin.

MEASUREMENTS AND MAIN RESULTS

In vitro, primary type II alveolar epithelial cells undergo phenotypic changes of EMT when exposed to transforming growth factor-beta(1) and epidermal growth factor with loss of prosurfactant protein C and E-cadherin and gain of S100A4 and type I procollagen. In vivo, using cell fate reporter mice, approximately one-third of S100A4-positive fibroblasts were derived from lung epithelium 2 weeks after bleomycin administration. From bone marrow chimera studies, one-fifth of S100A4-positive fibroblasts were derived from bone marrow at this same time point. Myofibroblasts rarely derived from EMT or bone marrow progenitors.

CONCLUSIONS

Both EMT and bone marrow progenitors contribute to S100A4-positive fibroblasts in bleomycin-induced lung fibrosis. However, neither origin is a principal contributor to lung myofibroblasts.

Biomarkers for epithelial-mesenchymal transitions

Somatic cells that change from one mature phenotype to another exhibit the property of plasticity. It is increasingly clear that epithelial and endothelial cells enjoy some of this plasticity, which is easily demonstrated by studying the process of epithelial-mesenchymal transition (EMT). Published reports from the literature typically rely on ad hoc criteria for determining EMT events; consequently, there is some uncertainty as to whether the same process occurs under different experimental conditions. As we discuss in this Personal Perspective, we believe that context and various changes in plasticity biomarkers can help identify at least three types of EMT and that using a collection of criteria for EMT increases the likelihood that everyone is studying the same phenomenon - namely, the transition of epithelial and endothelial cells to a motile phenotype.

Stromal transforming growth factor-beta signaling mediates prostatic response to androgen ablation by paracrine Wnt activity

Mechanisms of androgen dependence of the prostate are critical to understanding prostate cancer progression to androgen independence associated with disease mortality. Transient elevation of transforming growth factor-beta (TGF-beta) occurs after androgen ablation. To determine the role of TGF-beta on prostate response to androgen ablation, conditional TGF-beta type II receptor knockout mouse models of the epithelia (Tgfbr2(NKX3.1KO)) and stromal fibroblasts (Tgfbr2(fspKO)) were used. After castration, the prostates of Tgfbr2(NKX3.1KO) mice had apoptosis levels similar to those expected for control Tgfbr2(floxE2/floxE2) mice. Prostates of Tgfbr2(fspKO) mice, however, had reduced regression and high levels of proliferation associated with canonical Wnt activity throughout the glandular epithelia regardless of androgen status. In contrast, Tgfbr2(floxE2/floxE2) prostates had epithelial canonical Wnt activity only in the surviving proximal ducts after castration. In vitro studies showed that androgen antagonist, bicalutamide, transiently elevated both Tgfbr2(floxE2/floxE2) and Tgfbr2(fspKO) stromal expression of Wnt-2, Wnt-3a, and Wnt-5a. The neutralization of Wnt signaling by the expression of secreted frizzled related protein-2 (SFRP-2) resulted in decreased LNCaP prostate epithelial cell proliferation in stromal conditioned media transfer experiments. In vivo tissue recombination studies using Tgfbr2(fspKO) prostatic stromal cells in combination with wild-type or SV40 large T antigen expressing epithelia resulted in prostates that were refractile to androgen ablation. The expression of SFRP-2 restored the Tgfbr2(fspKO)-associated prostate responsiveness to androgen ablation. These studies reveal a novel TGF-beta, androgen, and Wnt paracrine signaling axis that enables prostatic regression of the distal ducts after androgen ablation while supporting proximal duct survival.

Stable expression of HIF-1alpha in tubular epithelial cells promotes interstitial fibrosis

Chronic hypoxia accelerates renal fibrosis. The chief mediator of the hypoxic response is hypoxia-inducible factor 1 (HIF-1) and its oxygen-sensitive component HIF-1alpha. HIF-1 regulates a wide variety of genes, some of which are closely associated with tissue fibrosis. To determine the specific role of HIF-1 in renal fibrosis, we generated a knockout mouse in which tubular epithelial expression of von Hippel-Lindau tumor suppressor (VHL), which acts as a ubiquitin ligase to promote proteolysis of HIF-1alpha, was targeted. We investigated the effect of VHL deletion (i.e., stable expression of HIF-1alpha) histologically and used the anti-HIF-1alpha agent [3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole] (YC-1) to test whether inhibition of HIF-1alpha could represent a novel approach to treating renal fibrosis. The area of renal fibrosis was significantly increased in a 5/6 renal ablation model of VHL-/- mice and in all VHL-/- mice at least 60 wk of age. Injection of YC-1 inhibited the progression of renal fibrosis in unilateral ureteral obstruction model mice. In conclusion, HIF-1alpha appears to be a critical contributor to the progression of renal fibrosis and could be a useful target for its treatment.

A mouse model for polycystic kidney disease through a somatic in-frame deletion in the 5' end of Pkd1

Autosomal dominant polycystic kidney disease, a leading cause of end-stage renal disease in adults, is characterized by progressive focal cyst formation in the kidney. Embryonic lethality of Pkd1-targeted mice limits the use of these mice. Here we developed a floxed allele of Pkd1 exons 2-6. Global deletion mutants developed polyhydramnios, hydrops fetalis, polycystic kidney and pancreatic disease. Somatic Pkd1 inactivation in the kidney was achieved by crossing Pkd1(flox) mice with transgenic mice expressing Cre controlled by a gamma-glutamyltranspeptidase promoter. These mutants developed cysts in both proximal and distal nephron segments and survived for about 4 weeks. Somatic loss of heterozygosity was shown in a reporter mouse strain to cause cystogenesis. Some cysts in young mice are positive for multiple tubular markers and a mesenchymal marker, suggesting a delay in tubular epithelial differentiation. A higher cell proliferation rate was observed in distal nephron segments probably accounting for the faster growth rate of distal cysts. Although we observed an overall increase in apoptosis in cystic kidneys, there was no difference between proximal or distal nephron segments. We also found increased cyclic AMP, aquaporin 2 and vasopressin type 2 receptor mRNA levels, and apical membrane translocation of aquaporin 2 in cystic kidneys, all of which may contribute to the differential cyst growth rate observed. The accelerated polycystic kidney phenotype of these mice provides an excellent model for studying molecular pathways of cystogenesis and to test therapeutic strategies.

Increased hospital mortality in patients with bedside hippus

BACKGROUND

Hippus is a prominent, repetitive oscillation of the pupils. Although regarded by some as a normal variant of pupillary unrest, the clinical importance of hippus has not been investigated systematically in hospitalized patients.

METHODS

We conducted a retrospective cohort study of 117 hospitalized patients demonstrating hippus. To mitigate observer bias, 486 control patients were selected using 2 adjacent admissions by the same attending physician before and after each index case. The primary outcomes were mortality during the admission and within 30 days of discharge.

RESULTS

Patients with bedside hippus were more likely to die within 30 days of observation (P <.00005). Independent risk factors for death by 30 days were altered mental status (odds ratio [OR] 4.11; 95% confidence interval [CI], 2.05-8.25, P <.001), hippus (OR 2.99; 95% CI, 1.46-6.11, P = .003), cirrhosis (P = .029), and renal disease (P = .054); angiotensin-system inhibitors were protective (P = .012). Patients with hippus were more likely to have altered mental status (OR 11.23; 95% CI, 6.27-20.09, P <.001), a history of trauma (OR 3.76; 95% CI, 1.65-8.59, P = .002), cirrhosis (P = .038), renal disease (P = .051), and a history of using iron supplements (P = .016).

CONCLUSION

The recognition of hippus in hospitalized patients is a clinically important predictor of early mortality.

Therapeutic immune regulation in experimental interstitial nephritis with suppressor T cells and their soluble factors

The therapeutic application of immune regulation and suppressor T cells to the control and modulation of autoimmune disease is an area of growing experimental interest. Our group has been studying experimental interstitial nephritis, both to better understand the disease process itself and to test immunoregulatory strategies for their inhibitory and protective effects. This report gives a brief overview of this work.

Endothelial-to-mesenchymal transition contributes to cardiac fibrosis

Cardiac fibrosis, associated with a decreased extent of microvasculature and with disruption of normal myocardial structures, results from excessive deposition of extracellular matrix, which is mediated by the recruitment of fibroblasts. The source of these fibroblasts is unclear and specific anti-fibrotic therapies are not currently available. Here we show that cardiac fibrosis is associated with the emergence of fibroblasts originating from endothelial cells, suggesting an endothelial-mesenchymal transition (EndMT) similar to events that occur during formation of the atrioventricular cushion in the embryonic heart. Transforming growth factor-beta1 (TGF-beta1) induced endothelial cells to undergo EndMT, whereas bone morphogenic protein 7 (BMP-7) preserved the endothelial phenotype. The systemic administration of recombinant human BMP-7 (rhBMP-7) significantly inhibited EndMT and the progression of cardiac fibrosis in mouse models of pressure overload and chronic allograft rejection. Our findings show that EndMT contributes to the progression of cardiac fibrosis and that rhBMP-7 can be used to inhibit EndMT and to intervene in the progression of chronic heart disease associated with fibrosis.

A proximal activator of transcription in epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is an important mechanism for phenotypic conversion in normal development and disease states such as tissue fibrosis and metastasis. While this conversion of epithelia is under tight transcriptional control, few of the key transcriptional proteins are known. Fibroblasts produced by EMT express a gene encoding fibroblast-specific protein 1 (FSP1), which is regulated by a proximal cis-acting promoter element called fibroblast transcription site-1 (FTS-1). In mass spectrometry, chromatin immunoprecipitation, and siRNA studies, we used FTS-1 as a unique probe for mediators of EMT and identified a complex of 2 proteins, CArG box-binding factor-A (CBF-A) and KRAB-associated protein 1 (KAP-1), that bind this site. Epithelial cells engineered to conditionally express recombinant CBF-A (rCBF-A) activate the transcription of FSP1 and undergo EMT. The FTS-1 response element also exists in the promoters modulating a broader EMT transcriptome, including Twist, and Snail, as well as E-cadherin, beta-catenin, ZO 1, vimentin, alpha1(I) collagen, and alpha-smooth muscle actin, and the induction of rCBF-A appropriately alters their expression as well. We believe formation of the CBF-A/KAP-1/FTS-1 complex is sufficient for the induction of FSP1 and a novel proximal activator of EMT.

Mechanisms of disease: Fibroblasts--a new look at an old problem

Fibroblasts are one of the most important and episodically active cell types in the kidney. Under normal conditions, these cells provide a delicate collagenous matrix that partitions the interstitial spaces between nephrons, blood vessels and the renal capsule. Fibroblasts also remodel the interstitium as kidneys grow with age. This episodic activity of various fibroblast populations has a biological basis. Most fibroblasts are created locally through a process called epithelial-mesenchymal transition (EMT) and, once formed, they can proliferate in response to local mitogens. EMT is driven by an alteration in the balance of local cytokine concentrations that reverses the differentiation of selected epithelia along tubular nephrons. During persistent injury and inflammation, fibroblasts further increase their numbers and secrete excess interstitial collagens, and EMT is particularly aggressive in this setting. The mechanisms by which fibroblasts simultaneously destroy normal interstitial architecture and disable epithelial nephrons are more comprehensible today. Recent therapeutic clues for attenuating fibroblast formation during renal fibrogenesis also suggest an advantage in shifting local cytokine balance to favor mesenchymal-epithelial transition. This review examines these issues and identifies new targets for the treatment of one of the most difficult problems facing clinical nephrology.

Role of EGF Receptor Activation in Angiotensin II–Induced Renal Epithelial Cell Hypertrophy

For determination of the molecular mechanisms underlying the induction of epithelial cell hypertrophy by angiotensin II (Ang II), a well-characterized porcine renal proximal tubular cell line LLCPKcl4, which does not express endogenous Ang II receptor subtypes, was transfected with cDNA encoding Ang II subtype 1 receptor (AT1R/Cl4). Ang II transactivated the EGF receptor (EGFR) in these AT1R/Cl4 cells, which was blocked by the selective AT1R antagonist losartan but not by the selective AT2R antagonist PD123319. Ang II did not transactivate EGFR in empty vector-transfected LLCPKcl4 cells (Vector/Cl4). Ang II elicited release of soluble heparin-binding EGF-like growth factor (HB-EGF) from AT1R/Cl4 cells, and Ang II-induced EGFR activation was prevented by pretreatment with the specific HB-EGF inhibitor CRM197 or the metalloproteinase inhibitors batimastat or phenanthroline, none of which had any effect on EGFR activation by exogenously administered EGF. Ang II stimulated protein synthesis and cell hypertrophy in AT1R/Cl4 cells without increasing cell number, and signaling studies revealed that Ang II stimulated phosphorylation of the 40S ribosomal protein S6 and the eukaryotic translation initiation factor 4E-binding protein 1, the two downstream target proteins of the mammalian target of rapamycin, which is a central regulator of protein synthesis and cell size. Ang II-induced mammalian target of rapamycin activation, [3H]leucine incorporation, and cellular hypertrophy were inhibited by pretreatment with either batimastat or CRM197 or by pretreatment with rapamycin or the EGFR tyrosine kinase inhibitor AG1478. Ang II also stimulated Smad 2/3 phosphorylation, which was blocked by a selective TGF-beta receptor I kinase inhibitor but not by CRM197. With blockade of TGF-beta receptor, Ang II-mediated hypertrophy was converted into cell proliferation, which was blocked by CRM197. In summary, this is the first demonstration that HB-EGF shedding-dependent EGFR transactivation, along with activation of TGF-beta signaling pathways, mediates Ang II-induced renal tubular epithelial cell hypertrophy.

Toward a Unified Theory of Renal Progression

Various disciplines within nephrology investigate the mechanisms by which kidneys fail. Progress in the areas of glomerular hemodynamics, proteinuria, tubular biology, interstitial nephritis, fibroblast formation, and fibrosis have added kernels of information that together support a unified theory of renal progression. Prevention of progression to end-stage disease has largely focused on control of systemic and glomerular hypertension. Current success in delaying a decline in glomerular filtration rate underlines the promise of a more comprehensive approach. New knowledge about the cell biology of progression also suggests that other adjunctive therapies may be possible. We describe the progress and highlight those spheres where new-targeted interventions may arise.

Immunolocalization of fibroblast growth factor-1 (FGF-1), its receptor (FGFR-1), and fibroblast-specific protein-1 (FSP-1) in inflammatory renal disease

BACKGROUND

The fibroblast growth factor (FGF) family has functions in development, cell proliferation, migration, and differentiation. While FGF-2 induces fibrosis, the role of FGF-1 in inflammation and fibrosis is less defined. We examined the expression of FGF-1 and FGF receptor (FGFR-1) to determine if renal diseases with varying etiologies of inflammation, including lupus nephritis (LN), acute interstitial nephritis (AIN) and acute rejection superimposed on chronic allograft nephropathy (CAN), showed varying patterns of expression. We also examined the expression of fibroblast-specific protein-1 (FSP-1), which has been linked to epithelial-mesenchymal transition (EMT) and fibrosis, to determine whether it was linked to potential profibrotic and inflammatory FGF-1 mechanisms.

METHODS

Proliferative LN (PLN) (N= 12), nonproliferative lupus nephritis (NPLN) (N= 5), AIN (N= 6), CAN (N= 4), and normal kidneys (N= 3) were studied. FGF, FGFR-1, and FSP-1 were localized by immunohistochemistry, and intensity scored on a 0 to 3+ scale. Double staining with CD68 and separate immunohistochemical staining for CD4 and CD8 with serial sections analysis were done to identify if T lymphocytes or macrophages showed staining for FGF-1 and FGFR-1 or FSP-1.

RESULTS

In normal kidneys, FGF-1 was expressed in mesangial cells (0.67 +/- 0.58), glomerular endothelial (0.67 +/- 0.58), visceral, and parietal epithelial cells (1.67 +/- 0.58). FGFR-1 showed a similar pattern of staining but also was expressed in tubular epithelium, and arterial endothelium and smooth muscle. Expression of FGF-1 was increased over normal in glomerular parenchymal cells only in CAN in podocytes (2.30 +/- 0.58 vs. 3.00 +/- 0.00) (P < 0.05) and parietal epithelial cells (1.67 +/- 0.58 vs. 2.25 +/- 0.50) (P < 0.05). Infiltrating glomerular and interstitial inflammatory cells in diseased glomeruli also expressed FGF-1 and FGFR-1. Tubular cells expressed slightly increased FGFR-1 in renal diseases vs. normal, whereas tubules remained negative for FGF-1 in diseased kidneys. FSP-1 expression was prominent in the interstitium in all kidneys with interstitial inflammation, and most prominent in CAN. Interstitial FSP-1+ cells were consistent with a myofibroblast-type morphology, and did not stain with CD-68. FSP-1 expression was closely associated with inflammatory cells expressing FGF-1 and FGFR-1. FSP-1 also showed positivity within crescents and occasional podocytes in PLN.

CONCLUSION

The expression of FGF-1 and FGFR-1 in infiltrating lymphocytes and macrophages, and of FGFR-1 in tubules, is supportive, but does not prove causality, of the possibility that FGF-1 might have both autocrine and paracrine functions in renal inflammation. However, the initial stimulus for renal inflammation, whether immune complex, hypersensitivity or rejection, did not alter expression patterns of FGF-1 or its receptor. The colocalization of inflammatory infiltrates with interstitial fibrosis supports the possibility of a contribution of FGF-1 for chemotaxis and associated fibrosis, further supported by interstitial FSP-1 expression closely associated with these inflammatory cells expressing FGF-1 and FGFR-1.

Fibroblast-specific protein 1 is a specific prognostic marker for renal survival in patients with IgAN

BACKGROUND

There is little direct evidence that fibroblasts are involved in the progression of the renal interstitial fibrosis in human glomerulonephritis. With the availability of a new specific marker for fibroblasts, we determined the presence of fibroblasts in kidneys with IgA nephropathy (IgAN) and correlated their numbers with various clinical parameters. In particular, we also prospectively asked if the number of fibroblasts in the renal interstitium correlates with prognosis.

METHODS

Cells positive for fibroblast-specific protein 1 (FSP1) were localized in renal biopsy specimens using immunohistochemistry with anti-FSP1 antibody. Clinical features were analyzed by one-way analysis of variance (ANOVA) with the Bonferroni correction. To assess the prognostic impact of the number of FSP1+ fibroblasts on renal survival in 142 patients with normal serum creatinine, the relationship between covariates to renal survival were evaluated univariately using the log-rank test and multivariately using Cox proportional hazards.

RESULTS

Fibroblasts identified by their expression of FSP1 accumulate in areas showing severe interstitial fibrosis. Some tubular epithelial cells undergoing epithelial-mesenchymal transition (EMT) in fibrotic areas also express FSP1. Numbers of FSP1+ fibroblasts directly correlate with serum creatinine (r = 0.74, P < 0.0001) and inversely correlate with estimated creatinine clearance (r = -0.54, P < 0.0001), and by multivariate analysis, the clinical factors influencing renal survival are urinary protein excretion [> or = 1.0 g/day, relative risk (RR) = 4.20, P= 0.032], hypertension (RR 5.85, P = 0.0027), and > or = 20 FSP1+ fibroblasts per high power field (HPF) (RR 7.39, P = 0.0015). Staining for FSP1+ fibroblasts is largely nonoverlapping with alpha-smooth muscle actin+ (alpha-SMA) cells in the interstitium.

CONCLUSION

The target protein FSP1 identifies human fibroblasts and tubular epithelium undergoing EMT, and distinguishes them from the diaspora of alpha-SMA+ vascular smooth muscle cells. FSP1+ fibroblasts are critically related to the progression of IgAN; consequently, staining FSP1 in renal biopsy specimens provides a valuable histologic index of progression.