The Least Mating Pathway: Synthetically Refactoring a Familiar Signaling System for New Applications.

Synthetic refactoring makes naturally occurring regulatory systems more amenable to manipulation by removing or recoding their natural genetic complexity. Shaw et al. apply this technique to the yeast mating response pathway, creating a simplified, highly engineerable signaling module that can be used to construct precisely optimized, application-specific GPCR biosensors.

Hyaluronan Hydrogels for a Biomimetic Spongiosa Layer of Tissue Engineered Heart Valve Scaffolds.

Advanced tissue engineered heart valves must be constructed from multiple materials to better mimic the heterogeneity found in the native valve. The trilayered structure of aortic valves provides the ability to open and close consistently over a full human lifetime, with each layer performing specific mechanical functions. The middle spongiosa layer consists primarily of proteoglycans and glycosaminoglycans, providing lubrication and dampening functions as the valve leaflet flexes open and closed. In this study, hyaluronan hydrogels were tuned to perform the mechanical functions of the spongiosa layer, provide a biomimetic scaffold in which valve cells were encapsulated in 3D for tissue engineering applications, and gain insight into how valve cells maintain hyaluronan homeostasis within heart valves. Expression of the HAS1 isoform of hyaluronan synthase was significantly higher in hyaluronan hydrogels compared to blank-slate poly(ethylene glycol) diacrylate (PEGDA) hydrogels. Hyaluronidase and matrix metalloproteinase enzyme activity was similar between hyaluronan and PEGDA hydrogels, even though these scaffold materials were each specifically susceptible to degradation by different enzyme types. KIAA1199 was expressed by valve cells and may play a role in the regulation of hyaluronan in heart valves. Cross-linked hyaluronan hydrogels maintained healthy phenotype of valve cells in 3D culture and were tuned to approximate the mechanical properties of the valve spongiosa layer. Therefore, hyaluronan can be used as an appropriate material for the spongiosa layer of a proposed laminate tissue engineered heart valve scaffold.

Ultra-high throughput mapping of genetic design space.

Massively parallel genetic screens have been used to map sequence-to-function relationships for a variety of genetic elements. However, because these approaches only interrogate short sequences, it remains challenging to perform high throughput (HT) assays on constructs containing combinations of sequence elements arranged across multi-kb length scales. Overcoming this barrier could accelerate synthetic biology; by screening diverse gene circuit designs, "composition-to-function" mappings could be created that reveal genetic part composability rules and enable rapid identification of behavior-optimized variants. Here, we introduce CLASSIC, a generalizable genetic screening platform that combines long- and short-read next-generation sequencing (NGS) modalities to quantitatively assess pooled libraries of DNA constructs of arbitrary length. We show that CLASSIC can measure expression profiles of >10 5 drug-inducible gene circuit designs (ranging from 6-9 kb) in a single experiment in human cells. Using statistical inference and machine learning (ML) approaches, we demonstrate that data obtained with CLASSIC enables predictive modeling of an entire circuit design landscape, offering critical insight into underlying design principles. Our work shows that by expanding the throughput and understanding gained with each design-build-test-learn (DBTL) cycle, CLASSIC dramatically augments the pace and scale of synthetic biology and establishes an experimental basis for data-driven design of complex genetic systems.

Comparison of the contractile properties, oxidative capacities and fibre type profiles of the voluntary sphincters of continence in the rat.

The external urethral sphincter (EUS) and external anal sphincter (EAS) are the principal voluntary striated muscles that sustain continence of urine and faeces. In light of their common embryological origin, shared tonic sphincteric action and synchronized electrical activity in vivo, it was expected that they would exhibit similar physiological and structural properties. However, the findings of this study using paired observations of both sphincters isolated from the rat show clearly that this is not the case. The anal sphincter is much more fatigable than the urethral sphincter. On completion of a fatigue protocol, the amplitude of the last twitch of the EAS had declined to 42 +/- 3% of the first twitch, whereas the last twitch of the EUS was almost identical to that of the first (95 +/- 3%). Immunocytochemical detection of myosin heavy-chain isoforms showed that this difference was not due to the presence of more slow-twitch oxidative type 1 fibres in the EUS compared with the EAS (areal densities 4 +/- 1% and 5 +/- 1%, respectively; P = 0.35). In addition, the fatigue difference was not explained by a greater contribution to force production by fast oxidative type 2A fibres in the urethral sphincter. In fact, the anal sphincter contained a higher areal density of type 2A fibres (56 +/- 5% vs. 37 +/- 4% in the EUS, P = 0.017). The higher oxidative capacity of the EUS, measured histochemically, explained its fatigue resistance. These results were surprising because the fatigue-resistant urethral muscle exhibited faster single-twitch contraction times compared with the anal sphincter (56 +/- 0.87 ms vs. 72.5 +/- 1.16 ms, P < 0.001). Neither sphincter expressed the type 2X myosin isoform but the fast-twitch isoform type 2B was found exclusively in the EUS (areal density 16 +/- 2%). The type 2B fibres of the EUS were small (diameter 19.5 +/- 0.4 mum) in comparison to typical type 2B fibres of other muscles. As a whole the EUS is a more oxidative than glycolytic muscle. In conclusion, analysis of the twitch mechanics and fatigue of two sphincters showed that the EUS contained more fatigue-resistant muscle fibres compared with the EAS.

Inclusion of the Mesentery in Ileocolic Resection for Crohn's Disease is Associated With Reduced Surgical Recurrence.

BACKGROUND AND AIMS: Inclusion of the mesentery during resection for colorectal cancer is associated with improved outcomes but has yet to be evaluated in Crohn's disease. This study aimed to determine the rate of surgical recurrence after inclusion of mesentery during ileocolic resection for Crohn's disease. METHODS: Surgical recurrence rates were compared between two cohorts. Cohort A [n = 30] underwent conventional ileocolic resection where the mesentery was divided flush with the intestine. Cohort B [n = 34] underwent resection which included excision of the mesentery. The relationship between mesenteric disease severity and surgical recurrence was determined in a separate cohort [n = 94]. A mesenteric disease activity index was developed to quantify disease severity. This was correlated with the Crohn's disease activity index and the fibrocyte percentage in circulating white cells. RESULTS: Cumulative reoperation rates were 40% and 2.9% in cohorts A and B [P = 0.003], respectively. Surgical technique was an independent determinant of outcome [P = 0.007]. Length of resected intestine was shorter in cohort B, whilst lymph node yield was higher [12.25 ± 13 versus 2.4 ± 2.9, P = 0.002]. Advanced mesenteric disease predicted increased surgical recurrence [Hazard Ratio 4.7, 95% Confidence Interval: 1.71-13.01, P = 0.003]. The mesenteric disease activity index correlated with the mucosal disease activity index [r = 0.76, p < 0.0001] and the Crohn's disease activity index [r = 0.70, p < 0.0001]. The mesenteric disease activity index was significantly worse in smokers and correlated with increases in circulating fibrocytes. CONCLUSIONS: Inclusion of mesentery in ileocolic resection for Crohn's disease is associated with reduced recurrence requiring reoperation.

A Joint Mechanism of Action for Sacral Neuromodulation for Bladder and Bowel Dysfunction?

Sacral neuromodulation (SNM) is a clinically effective intervention for treatment of urinary and bowel disorders. The aim is to establish the hypothesis that there is a common mechanism of action for SNM in both systems. Current knowledge includes the following: (1) Therapeutic parameters may be different for the 2 efficacy measures. (2) SNM invokes neural circuits that can be observed as neurochemical changes in specific neuroanatomic structures downstream from the therapy delivery site. (3) There are important central nervous system effects for both therapies. (4) Clinical observations regarding normal continence sensations as well as physiological measures of continence are different for the 2 therapy areas.

3-Dimensional spatially organized PEG-based hydrogels for an aortic valve co-culture model.

Physiologically relevant in vitro models are needed to study disease progression and to develop and screen potential therapeutic interventions for disease. Heart valve disease, in particular, has no early intervention or non-invasive treatment because there is a lack of understanding the cellular mechanisms which lead to disease. Here, we establish a novel, customizable synthetic hydrogel platform that can be used to study cell-cell interactions and the factors which contribute to valve disease. Spatially localized cell adhesive ligands bound in the scaffold promote cell growth and organization of valve interstitial cells and valve endothelial cells in 3D co-culture. Both cell types maintained phenotypes, homeostatic functions, and produced zonally localized extracellular matrix. This model extends the capabilities of in vitro research by providing a platform to perform direct contact co-culture with cells in their physiologically relevant spatial arrangement.

Screening to prevent heart failure (STOP-HF): expanding the focus beyond asymptomatic left ventricular systolic dysfunction.

AIMS: We evaluated the extent to which left ventricular diastolic dysfunction (LVDD) contributes to the high false-positive rates observed when natriuretic peptides (NPs) are used to screen for left ventricular systolic dysfunction (LVSD), and the use of NPs in combination with electrocardiogram (ECG) to screen for pre-clinical ventricular dysfunction (PCVD). METHODS AND RESULTS: Eight hundred and fourteen patients over 40 years of age and with at least one cardiovascular risk factor were recruited. Screening strategies for LVSD included brain natriuretic peptide (BNP) alone at cut-offs of 20, 50, and 100 pg/mL, and BNP and abnormal ECG combined. Systolic and diastolic function was assessed by Doppler echocardiography. A left ventricular ejection fraction (LVEF) of <50% was present in 33 (4.1%) of subjects, while 11 (1.4%) had LVEF <40%. At a cut-off of 20, 50, and 100 pg/mL, sensitivity for BNP alone when screening for LVSD was 88, 70, and 45%, and specificity 46, 77, and 90%, respectively. Of those labelled 'false positive' in the 20, 50, and 100 pg/mL cut-off groups, 26, 46, and 65%, respectively, were found to have significant LVDD (left atrial volume index >34 mL/m(2)). Optimal sensitivity (80%) and specificity (72%) for PCVD was obtained when BNP at a cut-off of 50 pg/mL or an abnormal ECG were defined as a positive screen so that only this group would be sent for Doppler echocardiography. CONCLUSIONS: A significant number of patients at risk for LVSD and labelled false positive with screening were found to have LVDD. Identifying this at-risk cohort may improve outcomes, but the clinical and economic benefit of this screening strategy requires formal assessment.

[Multimodal surgical intervention to improve outcome after colon cancer]. / Multimodal kirurgisk indsats til forbedring af resultaterne efter coloncancer.

Surgeons have focused their efforts towards improving outcome following surgical treatment of rectal cancer by implementation of the total mesorectal excision technique, among others. Great progress has been made, and in Denmark and Sweden survival rates for rectal cancer now exceed those for colon cancer. Recently, the significance of complete mesocolic excision in colonic cancer has been acknowledged. Treatment of colon cancer is challenging in patients with locally advanced disease, peritoneal carcinomatosis, and emergency presentation, all of which are described.