Systematic identification of cancer cell vulnerabilities to natural killer cell-mediated immune surveillance.

Only a subset of cancer patients respond to T-cell checkpoint inhibitors, highlighting the need for alternative immunotherapeutics. We performed CRISPR-Cas9 screens in a leukemia cell line to identify perturbations that enhance natural killer effector functions. Our screens defined critical components of the tumor-immune synapse and highlighted the importance of cancer cell interferon-γ signaling in modulating NK activity. Surprisingly, disrupting the ubiquitin ligase substrate adaptor DCAF15 strongly sensitized cancer cells to NK-mediated clearance. DCAF15 disruption induced an inflamed state in leukemic cells, including increased expression of lymphocyte costimulatory molecules. Proteomic and biochemical analysis revealed that cohesin complex members were endogenous client substrates of DCAF15. Genetic disruption of DCAF15 was phenocopied by treatment with indisulam, an anticancer drug that functions through DCAF15 engagement. In AML patients, reduced DCAF15 expression was associated with improved survival. These findings suggest that DCAF15 inhibition may have useful immunomodulatory properties in the treatment of myeloid neoplasms.

CRISPRi-based genome-scale identification of functional long noncoding RNA loci in human cells.

The human genome produces thousands of long noncoding RNAs (lncRNAs)-transcripts >200 nucleotides long that do not encode proteins. Although critical roles in normal biology and disease have been revealed for a subset of lncRNAs, the function of the vast majority remains untested. We developed a CRISPR interference (CRISPRi) platform targeting 16,401 lncRNA loci in seven diverse cell lines, including six transformed cell lines and human induced pluripotent stem cells (iPSCs). Large-scale screening identified 499 lncRNA loci required for robust cellular growth, of which 89% showed growth-modifying function exclusively in one cell type. We further found that lncRNA knockdown can perturb complex transcriptional networks in a cell type-specific manner. These data underscore the functional importance and cell type specificity of many lncRNAs.

A Multiplexed Single-Cell CRISPR Screening Platform Enables Systematic Dissection of the Unfolded Protein Response.

Functional genomics efforts face tradeoffs between number of perturbations examined and complexity of phenotypes measured. We bridge this gap with Perturb-seq, which combines droplet-based single-cell RNA-seq with a strategy for barcoding CRISPR-mediated perturbations, allowing many perturbations to be profiled in pooled format. We applied Perturb-seq to dissect the mammalian unfolded protein response (UPR) using single and combinatorial CRISPR perturbations. Two genome-scale CRISPR interference (CRISPRi) screens identified genes whose repression perturbs ER homeostasis. Subjecting ∼100 hits to Perturb-seq enabled high-precision functional clustering of genes. Single-cell analyses decoupled the three UPR branches, revealed bifurcated UPR branch activation among cells subject to the same perturbation, and uncovered differential activation of the branches across hits, including an isolated feedback loop between the translocon and IRE1α. These studies provide insight into how the three sensors of ER homeostasis monitor distinct types of stress and highlight the ability of Perturb-seq to dissect complex cellular responses.

Compact and highly active next-generation libraries for CRISPR-mediated gene repression and activation.

We recently found that nucleosomes directly block access of CRISPR/Cas9 to DNA (Horlbeck et al., 2016). Here, we build on this observation with a comprehensive algorithm that incorporates chromatin, position, and sequence features to accurately predict highly effective single guide RNAs (sgRNAs) for targeting nuclease-dead Cas9-mediated transcriptional repression (CRISPRi) and activation (CRISPRa). We use this algorithm to design next-generation genome-scale CRISPRi and CRISPRa libraries targeting human and mouse genomes. A CRISPRi screen for essential genes in K562 cells demonstrates that the large majority of sgRNAs are highly active. We also find CRISPRi does not exhibit any detectable non-specific toxicity recently observed with CRISPR nuclease approaches. Precision-recall analysis shows that we detect over 90% of essential genes with minimal false positives using a compact 5 sgRNA/gene library. Our results establish CRISPRi and CRISPRa as premier tools for loss- or gain-of-function studies and provide a general strategy for identifying Cas9 target sites.

CRISPR Interference Efficiently Induces Specific and Reversible Gene Silencing in Human iPSCs.

Developing technologies for efficient and scalable disruption of gene expression will provide powerful tools for studying gene function, developmental pathways, and disease mechanisms. Here, we develop clustered regularly interspaced short palindromic repeat interference (CRISPRi) to repress gene expression in human induced pluripotent stem cells (iPSCs). CRISPRi, in which a doxycycline-inducible deactivated Cas9 is fused to a KRAB repression domain, can specifically and reversibly inhibit gene expression in iPSCs and iPSC-derived cardiac progenitors, cardiomyocytes, and T lymphocytes. This gene repression system is tunable and has the potential to silence single alleles. Compared with CRISPR nuclease (CRISPRn), CRISPRi gene repression is more efficient and homogenous across cell populations. The CRISPRi system in iPSCs provides a powerful platform to perform genome-scale screens in a wide range of iPSC-derived cell types, dissect developmental pathways, and model disease.

Nucleosomes impede Cas9 access to DNA in vivo and in vitro.

The prokaryotic CRISPR (clustered regularly interspaced palindromic repeats)-associated protein, Cas9, has been widely adopted as a tool for editing, imaging, and regulating eukaryotic genomes. However, our understanding of how to select single-guide RNAs (sgRNAs) that mediate efficient Cas9 activity is incomplete, as we lack insight into how chromatin impacts Cas9 targeting. To address this gap, we analyzed large-scale genetic screens performed in human cell lines using either nuclease-active or nuclease-dead Cas9 (dCas9). We observed that highly active sgRNAs for Cas9 and dCas9 were found almost exclusively in regions of low nucleosome occupancy. In vitro experiments demonstrated that nucleosomes in fact directly impede Cas9 binding and cleavage, while chromatin remodeling can restore Cas9 access. Our results reveal a critical role of eukaryotic chromatin in dictating the targeting specificity of this transplanted bacterial enzyme, and provide rules for selecting Cas9 target sites distinct from and complementary to those based on sequence properties.

Kinetics of Label Retaining Cells in the Developing Rat Kidneys.

BACKGROUND: The kidney is a specialized low-regenerative organ with several different types of cellular lineages. The BrdU label-retaining cell (LRCs) approach has been used as part of a strategy to identify tissue-specific stem cells in the kidney; however, because the complementary base pairing in double-stranded DNA blocks the access of the anti-BrdU antibody to BrdU subunits, the stem cell marker expression in BrdU-labeled cells are often difficult to detect. In this study, we introduced a new cell labeling and detection method in which BrdU was replaced with 5-ethynyl-2-deoxyuridine (EdU) and examined the time-dependent dynamic changes of EdU-labeled cells and potential stem/progenitor markers in the development of kidney. METHODS: Newborn rats were intraperitoneally injected with EdU, and their kidneys were harvested respectively at different time points at 1 day, 3 days, 1 week, 2 weeks, and 6 weeks post-injection. The kidney tissues were processed for EdU and cellular markers by immunofluorescence staining. RESULTS: At the early stage, LRCs labeled by EdU were 2176.0 ± 355.6 cells at day one in each renal tissue section, but dropped to 168 ± 48.4 cells by week 6. As time increased, the numbers of LRCs were differentially expressed in the renal cortex and papilla. At the postnatal day one, nearly twice as many cells in the cortex were EdU-labeled as compared to the papilla (28.6 ± 3.6% vs. 15.6 ± 3.4%, P<0.05), while there were more LRCs within the renal papilla since the postnatal week one, and at the postnatal week 6, one third as many cells in the cortex were EdU-labeled as compared to the papilla (2.5 ± 0.1% vs. 7.7 ± 2.7%, P<0.05). The long-term LRCs at 6-week time point were associated exclusively with the glomeruli in the cortex and the renal tubules in the papilla. At 6 weeks, the EdU-labeled LRCs combined with expression of CD34, RECA-1, Nestin, and Synaptopodin were discretely but widely distributed within the glomeruli; Stro-1 around the glomeruli; and α-smooth muscle actin (SMA) in arteries. Conversely, co-expression of CD34, RECA-1, and Nestin with the long term EdU-labeled LRCs was significantly lower in renal tubules (P<0.01), while Stro-1 and Synaptopodin were not detected. CONCLUSION: Our data found that at 6-week time point, EdU-labeled LRCs existing in the glomeruli expressed undifferentiated podocyte and endothelial markers at high rates, while those in the renal tubules expressed Nestin and vascular markers at low rates. To understand the characterization and localization of these EdU-LRCs, further studies will be needed to test cell lineage tracing, clonogenicity and differentiation potency, and the contributions to the regeneration of the kidney in response to renal injury/repair.

Sex Bias and Maternal Contribution to Gene Expression Divergence in Drosophila Blastoderm Embryos.

Early embryogenesis is a unique developmental stage where genetic control of development is handed off from mother to zygote. Yet the contribution of this transition to the evolution of gene expression is poorly understood. Here we study two aspects of gene expression specific to early embryogenesis in Drosophila: sex-biased gene expression prior to the onset of canonical X chromosomal dosage compensation, and the contribution of maternally supplied mRNAs. We sequenced mRNAs from individual unfertilized eggs and precisely staged and sexed blastoderm embryos, and compared levels between D. melanogaster, D. yakuba, D. pseudoobscura and D. virilis. First, we find that mRNA content is highly conserved for a given stage and that studies relying on pooled embryos likely systematically overstate the degree of gene expression divergence. Unlike studies done on larvae and adults where most species show a larger proportion of genes with male-biased expression, we find that transcripts in Drosophila embryos are largely female-biased in all species, likely due to incomplete dosage compensation prior to the activation of the canonical dosage compensation mechanism. The divergence of sex-biased gene expression across species is observed to be often due to lineage-specific decrease of expression; the most drastic example of which is the overall reduction of male expression from the neo-X chromosome in D. pseudoobscura, leading to a pervasive female-bias on this chromosome. We see no evidence for a faster evolution of expression on the X chromosome in embryos (no "faster-X" effect), unlike in adults, and contrary to a previous study on pooled non-sexed embryos. Finally, we find that most genes are conserved in regard to their maternal or zygotic origin of transcription, and present evidence that differences in maternal contribution to the blastoderm transcript pool may be due to species-specific divergence of transcript degradation rates.

Zelda is differentially required for chromatin accessibility, transcription factor binding, and gene expression in the early Drosophila embryo.

The transition from a specified germ cell to a population of pluripotent cells occurs rapidly following fertilization. During this developmental transition, the zygotic genome is largely transcriptionally quiescent and undergoes significant chromatin remodeling. In Drosophila, the DNA-binding protein Zelda (also known as Vielfaltig) is required for this transition and for transcriptional activation of the zygotic genome. Open chromatin is associated with Zelda-bound loci, as well as more generally with regions of active transcription. Nonetheless, the extent to which Zelda influences chromatin accessibility across the genome is largely unknown. Here we used formaldehyde-assisted isolation of regulatory elements to determine the role of Zelda in regulating regions of open chromatin in the early embryo. We demonstrate that Zelda is essential for hundreds of regions of open chromatin. This Zelda-mediated chromatin accessibility facilitates transcription-factor recruitment and early gene expression. Thus, Zelda possesses some key characteristics of a pioneer factor. Unexpectedly, chromatin at a large subset of Zelda-bound regions remains open even in the absence of Zelda. The GAGA factor-binding motif and embryonic GAGA factor binding are specifically enriched in these regions. We propose that both Zelda and GAGA factor function to specify sites of open chromatin and together facilitate the remodeling of the early embryonic genome.

Next-generation libraries for robust RNA interference-based genome-wide screens.

Genetic screening based on loss-of-function phenotypes is a powerful discovery tool in biology. Although the recent development of clustered regularly interspaced short palindromic repeats (CRISPR)-based screening approaches in mammalian cell culture has enormous potential, RNA interference (RNAi)-based screening remains the method of choice in several biological contexts. We previously demonstrated that ultracomplex pooled short-hairpin RNA (shRNA) libraries can largely overcome the problem of RNAi off-target effects in genome-wide screens. Here, we systematically optimize several aspects of our shRNA library, including the promoter and microRNA context for shRNA expression, selection of guide strands, and features relevant for postscreen sample preparation for deep sequencing. We present next-generation high-complexity libraries targeting human and mouse protein-coding genes, which we grouped into 12 sublibraries based on biological function. A pilot screen suggests that our next-generation RNAi library performs comparably to current CRISPR interference (CRISPRi)-based approaches and can yield complementary results with high sensitivity and high specificity.

The incidence of erectile dysfunction after pelvic fracture urethral injury: A systematic review and meta-analysis.

BACKGROUND: Pelvic fracture urethral injury (PFUI) is associated with a high risk of erectile dysfunction (ED). The effect of the type of posterior urethral disruption repair on erectile function has not been clearly established. We systematically reviewed and conducted a meta-analysis of the proportion of patients with ED at (i) baseline after pelvic fracture with PFUI, (ii) after immediate primary realignment, and (iii) after delayed urethroplasty. METHODS: Using search terms for primary realignment or urethroplasty and urethral disruption, we systematically reviewed PubMed and EMBASE. A meta-analysis of the proportion of patients with ED was conducted assuming a random-effects model. RESULTS: Of 734 articles found, 24 met the inclusion criteria. The estimate of the proportion (95% confidence interval) of patients with ED after (i) PFUI was 34 (25-45)%, after (ii) immediate primary realignment was 16 (8-26)%, and after (iii) delayed urethroplasty was an additional 3 (2-5)% more than the 34% after pelvic fracture in this cohort. CONCLUSIONS: After pelvic fracture, 34% of patients had ED. After primary endoscopic alignment, patients had a lower reported rate of ED (16%). Delayed urethroplasty conferred an additional 3% risk above the 34% associated with PFUI alone, with 37% of patients having de novo ED. The difference in de novo ED after primary endoscopic alignment vs. delayed urethroplasty is probably due to reporting differences in ED and/or patients with less severe injury undergoing primary realignment.

Genome-Scale CRISPR-Mediated Control of Gene Repression and Activation.

While the catalog of mammalian transcripts and their expression levels in different cell types and disease states is rapidly expanding, our understanding of transcript function lags behind. We present a robust technology enabling systematic investigation of the cellular consequences of repressing or inducing individual transcripts. We identify rules for specific targeting of transcriptional repressors (CRISPRi), typically achieving 90%-99% knockdown with minimal off-target effects, and activators (CRISPRa) to endogenous genes via endonuclease-deficient Cas9. Together they enable modulation of gene expression over a ∼1,000-fold range. Using these rules, we construct genome-scale CRISPRi and CRISPRa libraries, each of which we validate with two pooled screens. Growth-based screens identify essential genes, tumor suppressors, and regulators of differentiation. Screens for sensitivity to a cholera-diphtheria toxin provide broad insights into the mechanisms of pathogen entry, retrotranslocation and toxicity. Our results establish CRISPRi and CRISPRa as powerful tools that provide rich and complementary information for mapping complex pathways.

Establishment of regions of genomic activity during the Drosophila maternal to zygotic transition.

We describe the genome-wide distributions and temporal dynamics of nucleosomes and post-translational histone modifications throughout the maternal-to-zygotic transition in embryos of Drosophila melanogaster. At mitotic cycle 8, when few zygotic genes are being transcribed, embryonic chromatin is in a relatively simple state: there are few nucleosome free regions, undetectable levels of the histone methylation marks characteristic of mature chromatin, and low levels of histone acetylation at a relatively small number of loci. Histone acetylation increases by cycle 12, but it is not until cycle 14 that nucleosome free regions and domains of histone methylation become widespread. Early histone acetylation is strongly associated with regions that we have previously shown to be bound in early embryos by the maternally deposited transcription factor Zelda, suggesting that Zelda triggers a cascade of events, including the accumulation of specific histone modifications, that plays a role in the subsequent activation of these sequences.

Sex-specific embryonic gene expression in species with newly evolved sex chromosomes.

Sex chromosome dosage differences between females and males are a significant form of natural genetic variation in many species. Like many species with chromosomal sex determination, Drosophila females have two X chromosomes, while males have one X and one Y. Fusions of sex chromosomes with autosomes have occurred along the lineage leading to D. pseudoobscura and D. miranda. The resulting neo-sex chromosomes are gradually evolving the properties of sex chromosomes, and neo-X chromosomes are becoming targets for the molecular mechanisms that compensate for differences in X chromosome dose between sexes. We have previously shown that D. melanogaster possess at least two dosage compensation mechanisms: the well- characterized MSL-mediated dosage compensation active in most somatic tissues, and another system active during early embryogenesis prior to the onset of MSL-mediated dosage compensation. To better understand the developmental constraints on sex chromosome gene expression and evolution, we sequenced mRNA from individual male and female embryos of D. pseudoobscura and D. miranda, from ∼0.5 to 8 hours of development. Autosomal expression levels are highly conserved between these species. But, unlike D. melanogaster, we observe a general lack of dosage compensation in D. pseudoobscura and D. miranda prior to the onset of MSL-mediated dosage compensation. Thus, either there has been a lineage-specific gain or loss in early dosage compensation mechanism(s) or increasing X chromosome dose may strain dosage compensation systems and make them less effective. The extent of female bias on the X chromosomes decreases through developmental time with the establishment of MSL-mediated dosage compensation, but may do so more slowly in D. miranda than D. pseudoobscura. These results also prompt a number of questions about whether species with more sex-linked genes have more sex-specific phenotypes, and how much transcript level variance is tolerable during critical stages of development.

Extensive divergence of transcription factor binding in Drosophila embryos with highly conserved gene expression.

To better characterize how variation in regulatory sequences drives divergence in gene expression, we undertook a systematic study of transcription factor binding and gene expression in blastoderm embryos of four species, which sample much of the diversity in the 40 million-year old genus Drosophila: D. melanogaster, D. yakuba, D. pseudoobscura and D. virilis. We compared gene expression, measured by mRNA-seq, to the genome-wide binding, measured by ChIP-seq, of four transcription factors involved in early anterior-posterior patterning. We found that mRNA levels are much better conserved than individual transcription factor binding events, and that changes in a gene's expression were poorly explained by changes in adjacent transcription factor binding. However, highly bound sites, sites in regions bound by multiple factors and sites near genes are conserved more frequently than other binding, suggesting that a considerable amount of transcription factor binding is weakly or non-functional and not subject to purifying selection.

Efficacy of BloodSTOP iX, surgicel, and gelfoam in rat models of active bleeding from partial nephrectomy and aortic needle injury.

OBJECTIVE: To compare the bleeding time using 3 different hemostatic agents in a rat model of partial nephrectomy and aortic needle injury. METHODS: Bilateral partial nephrectomy was performed in 20 rats with a total bleeding surface of 1.5 cm(2) without vascular clamping. Surgicel (n = 10) or BloodSTOP iX (n = 10) matrix was applied on each kidney cut surface. Finger pressure was applied to the parenchyma with transparent plastic bubble wrap to allow for visualization of the site and monitor the bleeding time. Pressure was applied until the bleeding stopped and then released to assess the presence of active bleeding for 5 minutes. An additional 24 rats underwent aortic trauma with a 25-gauge needle puncture, and the efficacy of the topical hemostatic agents were compared among Gelfoam (n = 8), Surgicel (n = 8), and BloodSTOP iX (n = 8). RESULTS: After partial nephrectomy, the mean bleeding time with BloodSTOP iX and Surgicel treatment was 83.70 ± 13.73 seconds and 168.8 ± 19.41 seconds, respectively, a statistically significant difference (P = .002). After aortic injury, the mean bleeding time was 157.5 ± 31.44 seconds, 187.5 ± 23.20 seconds, and 66.00 ± 13.74 seconds in the Gelfoam, Surgicel, and BloodSTOP groups, respectively, which was statistically significant (P = .004). CONCLUSION: The BloodSTOP iX hemostatic surgical matrix was more effective in reducing the bleeding time than Surgicel in a rat model of partial nephrectomy. Similarly, in an aortic needle injury model, BloodSTOP iX achieved hemostasis faster than Gelfoam or Surgicel.

Gender differences in academic productivity and academic career choice among urology residents.

PURPOSE: Gender disparities have long existed in medicine but they have not been well examined in urology. We analyzed a large cohort of graduating urology residents to investigate gender disparities in academic productivity, as measured by peer reviewed publications and academic career choice. MATERIALS AND METHODS: We assembled a list of urology residents who graduated from 2002 through 2008 who were affiliated with the top 50 urology hospitals, as ranked by 2009 U.S. News & World Report. PubMed® was queried to determine the publication output of each resident during the last 3 years of residency. We used an Internet search to determine the fellowship training, career choice and academic rank of each subject. Gender effects on each factor were evaluated. RESULTS: A total of 459 male (84.5%) and 84 female (15.5%) residents were included in analysis. During residency women produced fewer total publications (average 3.0 vs 4.8, p = 0.01) and fewer as first author (average 1.8 vs 2.5, p = 0.03) than men. A higher proportion of women than men underwent fellowship training (54.8% vs 48.5%, p = 0.29) and ultimately chose an academic career (40.5% vs 33.3%, p = 0.20), although these differences were not statistically significant. Of residents who chose an academic career a higher proportion of men than women (24.7% vs 2.9%, p = 0.01) obtained associate vs assistant professor rank. CONCLUSIONS: Women produced fewer peer reviewed publications than men during residency but they were equally likely to undergo fellowship training and choose an academic career. During the study period a higher proportion of men achieved associate professor rank.

Effects of intravenous injection of adipose-derived stem cells in a rat model of radiation therapy-induced erectile dysfunction.

INTRODUCTION: Radiation therapy (RT) for prostate cancer is frequently associated with posttreatment erectile dysfunction (ED). AIM: To investigate whether injection of adipose-derived stem cells (ADSCs) can ameliorate RT-associated ED. METHODS: Thirty male rats were divided into three groups. The control + phosphate-buffered saline (PBS) group received tail-vein injection of PBS. The radiation + PBS group received radiation over the prostate and tail-vein injection of PBS. The radiation + ADSC group received radiation over the prostate and tail-vein injection of ADSCs, which were labeled with 5-ethynyl-2-deoxyuridine (EdU). Seventeen weeks later, erectile function was evaluated by intracavernous pressure (ICP) in response to electrostimulation of cavernous nerves (CNs). Penile tissue and major pelvic ganglia (MPG) were examined by immunofluorescence (IF) and EdU staining. MAIN OUTCOME MEASURES: Erectile function was measured by ICP. Protein expression was examined by IF, followed by image analysis and quantification. RESULTS: Radiation over the prostate caused a significant decrease in erectile function and in the expression of neuronal nitric oxide synthase (nNOS) in penis and MPG. Cavernous smooth muscle (CSM) but not endothelial content was also reduced. Injection of ADSCs significantly restored erectile function, nNOS expression, and CSM content in the irradiated rats. EdU-positive cells were visible in MPG. CONCLUSIONS: Radiation appears to cause ED via CN injury. ADSC injection can restore erectile function via CN regeneration.

Evolving practice patterns for the management of small renal masses in the USA.

UNLABELLED: What's known on the subject? and What does the study add? Treatment options for small renal masses include radical nephrectomy (RN), partial nephrectomy (PN), ablation, and surveillance. PN provides equivalent oncological as RN for small tumours, but long-term outcomes for ablation and surveillance are poorly defined. Due to changing techniques and technology, treatment patterns for small renal masses are rapidly developing. Prior studies had analysed utilisation trends for PN and RN to 2006, revealing a relative rise in the rate of PN. However, overall treatment trends including surveillance and ablation had not been studied using a population-based cohort. It has become increasingly clear that RN is associated with greater renal and cardiovascular deterioration than nephron-sparing treatments. Thus, it is important to understand current population-based practice patterns for the treatment of small renal masses to assess whether practitioners are adhering to ever-changing principles in this field. The present study provides up-to-date treatment trends in the USA using a large population-based cohort. OBJECTIVE: To describe the changing practice patterns in the management of small renal masses, including the use of surveillance and ablative techniques. PATIENTS AND METHODS: All patients in the Surveillance, Epidemiology and End Results (SEER) registry treated for renal masses of ≤7 cm in diameter, from 1998 to 2008, were included for analysis. Annual trends in the use of surveillance, ablation, partial nephrectomy (PN), and radical nephrectomy (RN) were calculated. Multinomial logistic regression was used to determine the association of demographic and clinical characteristics with treatment method. RESULTS: In all, 48 148 patients from 17 registry sites with a mean age of 63.4 years were included for analysis. Between 1998 and 2008, for masses of <2 cm and 2.1-4 cm, there was a dramatic increase in the proportion of patients undergoing PN (31% vs 50%, 16% vs 33%, respectively) and ablation (1% vs 11%, 2% vs 9%, respectively). In multivariable analysis, later year of diagnosis, male gender, being married, clinically localised disease, and smaller tumours were associated with increased use of PN vs RN. Later year of diagnosis, male gender, being unmarried, smaller tumour, and the presence of bilateral masses were associated with increased use of ablation and surveillance vs RN. CONCLUSIONS: PN is now used in half of all patients with the smallest renal masses, and its use continues to increase over time. Ablation and surveillance are less common overall, but there is increased usage over time in select populations.

Selective arterial embolization of angiomyolipomas: a comparison of smaller and larger embolic agents.

PURPOSE: Selective transarterial embolization for renal angiomyolipomas is effective in preventing or limiting hemorrhage and preserving normal parenchyma. Data are insufficient regarding the safety and efficacy of embolic agents. We compared transarterial embolization of angiomyolipomas using embolic agents of different sizes. MATERIALS AND METHODS: We performed a retrospective review of all transarterial angiomyolipoma embolizations from 1999 to 2010, and evaluated demographics, procedural data, embolization response and outcomes comparing smaller (less than 150 microns) and larger (more than 150 microns) embolic agents. RESULTS: Overall 48 patients underwent 66 embolization procedures for 72 angiomyolipomas. Smaller agents were used more commonly (58%). Age, gender, indications, pre-embolization angiomyolipoma size and prevalence of tuberous sclerosis were similar between the groups. Angiomyolipomas decreased a mean±SD 25%±18% after embolization with no differences between the groups (p=0.24). There were 10 angiomyolipomas that required 14 repeat embolizations (median 14 months). Repeat embolization of the same mass was almost sixfold more likely in those embolized with smaller agents (OR 5.88, 95% CI 1.64-20.8, p=0.002). Complications were similar between the groups, although 2 of 3 patients with acute respiratory distress underwent embolization with smaller agents. Patients with tuberous sclerosis had similar angiomyolipoma size, decrease in angiomyolipoma size, followup, complications and need for repeat embolization. Practice patterns changed regarding embolization agent size during the study period. CONCLUSIONS: Angioembolization with larger embolic agents is associated with higher long-term efficacy compared to smaller agents. Due to concerns for serious pulmonary complications, we no longer use agents smaller than 150 microns. Prospective studies are necessary to evaluate the optimal embolization technique to achieve durable outcomes without increasing patient morbidity.