Organ-on-chip models: Implications in drug discovery and clinical applications

Before a lead compound goes through a clinical trial, preclinical studies utilize two-dimensional (2D) in vitro models and animal models to study the pharmacodynamics and pharmacokinetics of that lead compound. However, these current preclinical studies may not accurately represent the efficacy and safety of a lead compound in humans, as there has been a high failure rate of drugs that enter clinical trials. All of these failures and the associated costs demonstrate a need for more representative models of human organ systems for screening in the preclinical phase of drug development. In this study, we review the recent advances in in vitro modeling including three-dimensional (3D) organoids, 3D microfabrication, and 3D bioprinting for various organs including the heart, kidney, lung, gastrointestinal tract (intestine-gut-stomach), liver, placenta, adipose, retina, bone, and brain as well as multiorgan models. The availability of organ-on-chip models provides a wealth of opportunities to understand the pathogenesis of human diseases and provide a potentially better model to screen a drug, as these models utilize a dynamic 3D environment similar to the human body. Although there are limitations of organ-on-chip models, the emergence of new technologies have refined their capability for translational research as well as precision medicine.

Transvenous Lead Extractions: Current Approaches and Future Trends

The use of cardiac implantable electronic devices (CIEDs) has continued to rise along with indications for their removal. When confronted with challenging clinical scenarios such as device infection, malfunction or vessel occlusion, patients often require the prompt removal of CIED hardware, including associated leads. Recent advancements in percutaneous methods have enabled physicians to face a myriad of complex lead extractions with efficiency and safety. Looking ahead, emerging technologies hold great promise in making extractions safer and more accessible for patients worldwide. This review will provide the most up-to-date indications and procedural approaches for lead extractions and insight on the future trends in this novel field.

Planar cell polarity-dependent and independent functions in the emergence of tissue-scale hair follicle patterns

Hair follicles of the mammalian epidermis display local order and global alignment, a complex pattern instructed by the core planar cell polarity (PCP) pathway. Here we address the contributions of core PCP genes, Van Gogh-like and Frizzled, to the establishment, local refinement, and global order of embryonic and postnatal hair follicles. We find that, similar to Fz6 mutants, the disordered hair patterns of Vangl2 mutants are refined over time and eventually corrected. In both mutants, we find that tissue-level reorientation occurs through locally coordinated follicle rotation at stereotyped locations. Strikingly, Vangl2 and Fz6 mutant follicles collectively rotate with opposing directionalities, suggesting that redundant core PCP signals contribute to their directed realignment. Consistently, global follicle alignment is not restored upon conditional ablation of both Vangl1 and Vangl2 genes. Instead, spatially distinct patterns of whorls and crosses emerge and persist even after a complete cycle of hair follicle regeneration. Thus, local refinement of hair follicles into higher order patterns can occur independently of the core PCP system, however, their global alignment with the body axes requires PCP function throughout morphogenesis, growth and regeneration.

Enhanced biological phosphorus removal in the retrofitting from an anoxic selector to an anaerobic selector in a full-scale activated sludge process in Singapore

This paper presents the investigation results of retrofitting an anoxic selector to an anaerobic selector through stepwise reduction of air supply in a full-scale activated sludge process with a focus on enhanced biological phosphorus removal (EBPR). The process experienced gradual shift from a Ludzack-Ettinger (LE) to an anaerobic-anoxic-oxic (A(2)O) process and subsequently, an anaerobic-oxic (A/O) process. The major findings are: (i) the average influent-based PO(4) (3-)-P release in the anaerobic selector compartment was 16.3 mg P l(-1) and that in the secondary clarifier was 1.7 mg P l(-1). 75% of the SCOD and 93% of the acetic acid in the primary effluent were taken up in the anaerobic selector compartment, respectively; (ii) PO(4) (3-)-P uptake contributed by both aerobic and denitrifying phosphorus accumulating organisms (DPAOs) occurred mainly in the first and second aerobic lanes together with simultaneous nitrification and denitrification (SND) while there was not much contribution from the last aerobic lane; (iii) The average PO(4) (3-)-P concentration of the final effluent was 2.4 mg P l(-1) corresponding to a removal efficiency of 85%; (iv) the SVI was satisfactory after retrofitting; and (v) the increase of NH(4) (+)-N in the final effluent from the commencement to the completion of the retrofitting resulted in an approximate 40-50% reduction in oxygen demand and a significant aeration energy saving was achieved.