An Evolving Understanding of the Genetic Causes of Abdominal Aortic Aneurysm Disease.

Aneurysms of the abdominal aorta (AAA) are relatively common - affecting as many as 8% of men and 1% of women over the age of 65. AAAs are characterized by a 50% increase in the diameter of the aneurysmal aorta compared with the normal vessel. Degeneration of structural components of the aortic wall is believed to be central in the pathogenesis of AAAs. The exact mechanism of degeneration is not well characterized, although degradation of elastin and collagen has been clearly shown. At least six genetic variants have been associated with AAA in genome-wide association studies: CDKN2BAS1, DAB2IP, LDLR, LRP1, SORT1, and IL6R. These variants reach genome-wide significance; however, they have not been replicated in multiple cohorts, nor have they been clearly shown to be disease causative. AAA is a challenging disease for investigation because it is most often asymptomatic and generally has a late disease onset, making it difficult to diagnose. Determination of the genetic mechanism behind aneurysm formation, progression, and rupture crosses disciplines requiring input from multiple fields of study, larger patient cohorts, and the evolving modalities of genetic testing.

Use of a Pteridine Moiety to Track DNA Uptake in Cells.

Fluorescence labeled oligonucleotides have a long history of being used to monitor nucleic acid transport and uptake. However, it is not known if the fluorescent moiety itself physically limits the number of pathways that can be used by the cell due to steric, hydrophobic, or other chemical characteristics. Here, we report a method for comparing the uptake kinetics of oligonucleotides labeled either with the fluorescent pteridine, 3-methyl-8-(2-deoxy-ß-D-ribofuranosyl) isoxanthopterin (3MI), or the common fluorophore 5-carboxyfluorescein (5-FAM). We use a multiphoton microscopic technique to monitor nucleic acid uptake LLC-PK1, a pig renal tubular cell line that is known to have multiple uptake pathways. We find that the two fluorophores enter the cells at different rates, suggesting that choice of fluorescent moiety influences the uptake pathway used by a cell. Finally, we reconstituted an LLC-PK1 membrane channel that is selective for nucleic acids in planar lipid bilayers, and tested the ability of the labeled nucleic acids to permeate the channel. We find that 3MI, and not 5-FAM labeled oligonucleotides can traverse the plasma membrane through the channel. These results have implications for future studies aimed at delivering pteridine moieties to cells and for tracking nucleic acid transport into tissues.

Implementation of an Online Reporting System to Identify Unprofessional Behaviors and Mistreatment Directed at Trainees at an Academic Medical Center.

Importance: Unprofessional behaviors and mistreatment directed at trainees continue to challenge the learning environment. Academic medical institutions should encourage reports of inappropriate behavior and address such reports directly to create a safe learning environment. Objective: To determine the feasibility of creating and implementing an online reporting system for receiving and reviewing complaints of unprofessional behavior directed toward or experienced by students, postdoctoral trainees, and residents. Design, Setting, and Participants: This cohort study assessed implementation of an online reporting system (feedback form) with a method for triaging reports, providing both positive and negative feedback, as well as adjudication and transparent public disclosure of aggregate data. The system was launched at a large urban academic medical center with numerous trainees that is fully integrated with a health system of 8 hospitals. Participants included faculty who interact with trainees, medical students, graduate students and postdoctoral fellows, and residents and clinical fellows. Follow-up began in October 2019 (at the time of tool launch) and lasted through December 2021. Data were analyzed from January to March 2022. Main Outcomes and Measures: The primary outcomes were the numbers and types of reports according to the reporter and the person reported about. Results: Participants included 2900 faculty who interact with trainees, 600 medical students, more than 1000 graduate students and postdoctoral fellows, and 2600 residents and clinical fellows. Trainees submitted 196 reports, 173 (88.3%) of which described unprofessional interactions. Among the reports describing unprofessional behavior, 60 (34.7%) were from medical students, 96 (55.5%) were from residents and fellows, 17 (9.8%) were from graduate students or postdoctoral trainees, and 78 (45.1%) were from men. The majority of negative reports described behaviors by faculty (106 [61.3%]), followed by residents and fellows (24 [13.9%]). Twenty faculty (<1.0%) accounted for 52 (50.0%) of the 104 reports describing unprofessional behaviors. Since implementation, most trainees are aware of this process. An increasing number have reported instances of mistreatment, and those who shared concerns through the online system report satisfaction with the outcome of the response to the report. Conclusions and Relevance: In this cohort study, the new reporting mechanism facilitated identification of the small number of individuals associated with unprofessional behaviors toward trainees and increased awareness of the school's commitment to creating a safe learning environment.

Investigating a Quantitative Measure of Student Self-authorship for Undergraduate Medical Education.

CONSTRUCT: In this study, the authors investigated the validity of a quantitative measure of self-authorship among medical students. Self-authorship is a cognitive-structural theory incorporating the ability to define one's beliefs, identity, and social relations to operate in a complex, ambiguous environment. BACKGROUND: Competency-based medical education (CBME) provides learners with the opportunity to self-direct their education at an appropriate pace to develop and exhibit required behaviors while incorporating functioning relationships with supervisors and trainers. Students must develop skills to adjust and succeed in this educational climate. Self-authorship is a theoretical lens that is relevant to identifying the development of the skills necessary to succeed in a CBME curriculum. Understanding the level of attained self-authorship by medical students can provide important information about which professional characteristics are more prevalent among those who are more self-authored and about how students succeed in medical school. Although there are calls in the extant literature for the application of self-authorship in medical education, there is no quantitative measure to assess its development among medical students. APPROACH: The authors developed a survey to measure self-authorship, including a free text question regarding the thought process around a hypothetical ethical situation during training. Data were collected in 2014 and 2015 from undergraduate medical students and analyzed using factor analysis and qualitative analysis of the free text. Validity evidence was sought regarding content, internal structure, and relationships to other variables. RESULTS: Analysis supports the use of a 22-item instrument to assess 3 constructs of self-authorship: asserting independence and autonomy, knowledge processing, and sense of self in ethical situations. Content analysis of text responses supported the ability of the instrument to separate development, or a lack thereof, of self-authorship. CONCLUSIONS: The authors identified an instrument that measures multidimensional, higher-order characteristics that intersect with self-authorship. This instrument can be useful at a macro level for curricular and student assessment of self-authorship. Development of these characteristics can help foster success in a CBME environment and support curricular efforts in this regard. Understanding a student's level of self-authorship can help identify areas for support as well as allow for comparisons of different student characteristics.

An update on the etiology of abdominal aortic aneurysms: implications for future diagnostic testing.

Abdominal aortic aneurysm (AAA) disease is multifactorial with both environmental and genetic risk factors. The current research in AAA revolves around genetic profiles and expression studies in both human and animal models. Variants in genes involved in extracellular matrix degradation, inflammation, the renin-angiotensin system, cell growth and proliferation and lipid metabolism have been associated with AAA using a variety of study designs. However, the results have been inconsistent and without a standard animal model for validation. Thus, despite the growing body of knowledge, the specific variants responsible for AAA development, progression and rupture have yet to be determined. This review explores some of the more significant genetic studies to provide an overview of past studies that have influenced the current understanding of AAA etiology. Expanding our understanding of disease pathogenesis will inform research into novel diagnostics and therapeutics and ultimately to improve outcomes for patients with AAA.

Lentiviral gene transduction of kidney.

Gene transfer into kidney holds great potential as a novel therapeutic approach. We have studied the transduction of kidney in vivo after delivery of lentiviral vectors by various routes of administration. A lentiviral vector expressing the bacterial lacZ gene from the cytomegalovirus early promoter was used. The lentiviral vector was delivered into the kidneys of BALB/c mice by retrograde infusion into the ureter, by injection into the renal vein or artery, or by direct injection into the renal parenchyma. Expression of the reporter gene was achieved independently of the route of administration, although it appeared more efficient after parenchymal or ureteral administration. After parenchymal or ureteral infusion, expression of the transgene was localized to the outer medulla and corticomedullary junction. In the case of parenchymal injection, expression of the reporter gene extended to the cortex. Detection of the transgene in the renal proximal tubules was confirmed by in situ polymerase chain reaction after parenchymal or ureteral infusion. On delivery of the lentiviral vector through the renal artery or vein, expression of the reporter gene was markedly lower than was observed with parenchymal or ureteral infusion and was limited to the inner medullary collecting ducts. No apparent histological abnormality was observed after virus administration and transgene expression was stable for at least 3 months. These results provide the first evidence that lentiviral vectors can stably transduce renal cells in vivo and may be effective vehicles for gene delivery to the kidney.

Wicking: a rapid method for manually inserting ion channels into planar lipid bilayers.

The planar lipid bilayer technique has a distinguished history in electrophysiology but is arguably the most technically difficult and time-consuming method in the field. Behind this is a lack of experimental consistency between laboratories, the challenges associated with painting unilamellar bilayers, and the reconstitution of ion channels into them. While there has be a trend towards automation of this technique, there remain many instances where manual bilayer formation and subsequent membrane protein insertion is both required and advantageous. We have developed a comprehensive method, which we have termed "wicking", that greatly simplifies many experimental aspects of the lipid bilayer system. Wicking allows one to manually insert ion channels into planar lipid bilayers in a matter of seconds, without the use of a magnetic stir bar or the addition of other chemicals to monitor or promote the fusion of proteoliposomes. We used the wicking method in conjunction with a standard membrane capacitance test and a simple method of proteoliposome preparation that generates a heterogeneous mixture of vesicle sizes. To determine the robustness of this technique, we selected two ion channels that have been well characterized in the literature: CLIC1 and α-hemolysin. When reconstituted using the wicking technique, CLIC1 showed biophysical characteristics congruent with published reports from other groups; and α-hemolysin demonstrated Type A and B events when threading single stranded DNA through the pore. We conclude that the wicking method gives the investigator a high degree of control over many aspects of the lipid bilayer system, while greatly reducing the time required for channel reconstitution.

Localization of the nucleic acid channel regulatory subunit, cytosolic malate dehydrogenase.

NACh is a nucleic acid-conducting channel found in apical membrane of rat kidney proximal tubules. It is a heteromultimeric complex consisting of at least two proteins: a 45-kDa pore-forming subunit and a 36-kDa regulatory subunit. The regulatory subunit confers ion selectivity and influences gating kinetics. The regulatory subunit has been identified as cytosolic malate dehydrogenase (cMDH). cMDH is described in the literature as a soluble protein that is not associated with plasma membrane. Yet a role for cMDH as the regulatory subunit of NACh requires that it be present at the plasma membrane. To resolve this conflict, studies were initiated to determine whether cMDH could be found at the plasma membrane. Before performing localization studies, a suitable model system that expressed NACh was identified. A channel was identified in LLC-PK(1) cells, a line derived from pig proximal tubule, that is selective for nucleic acid and has a conductance of approximately 10 pS. It exhibits dose-dependent blockade by heparan sulfate or L-malate. These characteristics are similar to what has been reported for NACh from rat kidney and indicate that NACh is present in LLC-PK(1) cells. LLC-PK(1) cells were therefore used as a model system for immunolocalization of cMDH. Both immunofluorescence and immunoelectron microscopy demonstrated cMDH at the plasma membrane of LLC-PK(1) cells. This finding supports prior functional data that describe a role for cMDH as the regulatory subunit of NACh.

Presence of the nucleic acid channel in renal brush-border membranes: allosteric modulation by extracellular calcium.

We have previously described a cell surface channel complex that is highly selective for nucleic acid (6, 7). The channel complex was purified to homogeneity by solubilizing renal brush-border membranes (BBM) with CHAPS and separation by liquid chromatography. It was characterized by reconstitution in planar lipid bilayers. The channel consists of a pore-forming subunit that is blocked by heparan sulfate and a regulatory subunit that is blocked by L-malate (7). The current studies were performed to compare the characteristics of the nucleic acid-conducting channel in native BBM with the characteristics that have been determined for the complex reconstituted from purified proteins. BBM were purified by differential centrifugation and reconstituted in lipid bilayers. Current was not observed until oligodeoxynucleotide (ODN) was added. Conductance was 9.1 +/- 0.9 pS; rectification and voltage dependence were not observed. Reversal potential (E(rev)) shifted to +14 +/- 0.1 mV by a 10-fold gradient for ODN but was not altered when gradients were created for any other ion. Open probability increased significantly with an increase in Ca(2+) on the trans chamber of the bilayer apparatus. Changes in cis Ca(2+) were without effect. Addition of L-malate to the cis chamber or heparan sulfate to the trans chamber significantly reduced the open probability of the channel. These data demonstrate that the nucleic acid channel in BBM is electrophysiologically and pharmacologically identical to that previously reported for purified protein and demonstrate that a nucleic acid-conducting channel is a component of renal BBM.

Applications of gene therapy to kidney disease.

PURPOSE OF REVIEW: This review summarizes recent applications of somatic cell gene therapy to the treatment of monogenetic renal diseases, renal cell carcinoma, and for the induction of tolerance in solid organ transplantation. In addition, several new gene therapy techniques will be discussed including gene and messenger RNA repair strategies, as well as methods designed to modify the expression of normal genes that may have application in the treatment of multigenetic disorders. RECENT FINDINGS: Animal studies have demonstrated prolonged graft survival after the successful induction of tolerance to alloantigens via hematopoietic molecular chimerism. Ongoing clinical trials for renal cell carcinoma are encouraging, in that IL-2 gene therapy using non-viral vector systems can reduce the tumor burden. However, limited progress has been made towards applying gene therapy for the most common genetic disorders of the kidney, autosomal dominant polycystic kidney disease and Alport syndrome. Basic research on novel gene repair and expression modulation techniques provide additional gene therapy options for the treatment of viral infections such as HIV-1 and monogenetic disorders. SUMMARY: Gene therapy holds enormous potential for the treatment of genetic and acquired diseases. Current pre-clinical studies and clinical trials provide encouraging results that gene therapy can become a useful treatment option. However, before gene therapy has widespread application, technical progress must be made in all aspects of treatment design, including optimizing vector and delivery systems and the ability to modify long-term cell populations such as stem cells.

Podocan, a novel small leucine-rich repeat protein expressed in the sclerotic glomerular lesion of experimental HIV-associated nephropathy.

Growing evidence suggests that human immunodeficiency virus (HIV)-1 infection of podocytes plays a central role in the glomerular disease of HIV-associated nephropathy (HIVAN). As an approach to identify host genes involved in the pathogenesis of the sclerotic glomerular lesion in HIVAN, representational difference analysis of cDNA was used to identify differentially expressed genes in HIV-1 transgenic and nontransgenic podocytes. We isolated a novel member of the small leucine-rich repeat (SLR) protein family, podocan, that is expressed at high levels in the HIV-1 transgenic podocytes. In normal embryonic kidney, a 3.2-kb podocan transcript was detected at low levels, and expression increased dramatically within 24 h following birth. Expression of a 2.3-kb transcript became evident after birth and gradually increased to 50% of the total podocan RNA in the mature kidney. Phylogenetically, podocan represents a new class in the SLR protein gene family, an expanding protein family sharing homology with the small leucine-rich repeat proteoglycans. The 3.2-kb transcript encodes a predicted 611-amino acid secretory protein with 20 leucine-rich repeats, a unique N-terminal cysteine-rich cluster pattern and a highly acidic C-terminal domain. In situ hybridization of normal kidney revealed podocan mRNA expression in podocytes and likely vascular endothelial cells within the glomerulus. The immunohistochemical staining pattern of podocan protein in normal kidney glomeruli was consistent with that of the glomerular basement membrane, and staining was markedly increased in sclerotic glomerular lesions in the transgenic HIVAN model. Thus, podocan defines a new class within the SLR protein family and is a previously unrecognized component of the sclerotic glomerular lesion that develops in the course of experimental HIVAN.

Cytosolic malate dehydrogenase confers selectivity of the nucleic acid-conducting channel.

We have described previously a cell surface channel that is highly selective for nucleic acids. Nucleic acid conductance is 10 pS and the channel is at least 10,000-fold more selective for oligodeoxynucleotides than any anion tested (1). Herein we provide evidence that the nucleic acid-conducting channel (NACh) is a heteromultimeric complex of at least two proteins; a 45-kDa pore-forming subunit (p45) and a 36-kDa regulatory subunit (p36). Reconstitution of p45 in planar lipid bilayers resulted in formation of a channel which gated in the absence of nucleic acid and which was more selective for anions (including oligonucleotide) than cations. This channel exhibited transitions from one level of current to another (or to the closed state); however the incidence of transitions was rare. Channel activity was not observed when p36 was reconstituted alone. Reconstitution of p36 with p45 restored nucleic acid dependence and selectivity to the channel. Protein sequence analysis identified p36 as cytosolic malate dehydrogenase (cMDH). Experiments were performed to prove that cMDH is a regulatory subunit of NACh. Selective activity was observed when p45 was reconstituted with pig heart cMDH but not with mitochondrial MDH. Both the enzyme substrate l-malate and antiserum raised against cMDH block NACh activity. These data demonstrate that a nucleic acid conducting channel is a complex of at least two proteins, p45 and cMDH. Furthermore, these data establish that cMDH confers nucleic acid selectivity of the channel.