Wnt-frizzled planar cell polarity signaling in the regulation of cell motility.

The molecular complexes underlying planar cell polarity (PCP) were first identified in Drosophila through analysis of mutant phenotypes in the adult cuticle and the orientation of associated polarized protrusions such as wing hairs and sensory bristles. The same molecules are conserved in vertebrates and are required for the localization of polarized protrusions such as primary or sensory cilia and the orientation of hair follicles. Not only is PCP signaling required to align cellular structures across a tissue, it is also required to coordinate movement during embryonic development and adult homeostasis. PCP signaling allows cells to interpret positional cues within a tissue to move in the appropriate direction and to coordinate this movement with their neighbors. In this review we outline the molecular basis of the core Wnt-Frizzled/PCP pathway, and describe how this signaling orchestrates collective motility in Drosophila and vertebrates. Here we cover the paradigms of ommatidial rotation and border cell migration in Drosophila, and convergent extension in vertebrates. The downstream cell biological processes that underlie polarized motility include cytoskeletal reorganization, and adherens junctional and extracellular matrix remodeling. We discuss the contributions of these processes in the respective cell motility contexts. Finally, we address examples of individual cell motility guided by PCP factors during nervous system development and in cancer disease contexts.

Therapies targeting Frizzled-7/ß-catenin pathway prevent the development of pathological angiogenesis in an ischemic retinopathy model.

Retinopathies remain major causes of visual impairment in diabetic patients and premature infants. Introduction of anti-angiogenic drugs targeting vascular endothelial growth factor (VEGF) has transformed therapy for these proliferative retinopathies. However, limitations associated with anti-VEGF medications require to unravel new pathways of vessel growth to identify potential drug targets. Here, we investigated the role of Wnt/Frizzled-7 (Fzd7) pathway in a mouse model of oxygen-induced retinopathy (OIR). Using transgenic mice, which enabled endothelium-specific and time-specific Fzd7 deletion, we demonstrated that Fzd7 controls both vaso-obliteration and neovascular phases (NV). Deletion of Fzd7 at P12, after the ischemic phase of OIR, prevented formation of aberrant neovessels into the vitreous by suppressing proliferation of endothelial cells (EC) in tufts. Next we validated in vitro two Frd7 blocking strategies: a monoclonal antibody (mAbFzd7) against Fzd7 and a soluble Fzd7 receptor (CRD). In vivo a single intravitreal microinjection of mAbFzd7 or CRD significantly attenuated retinal neovascularization (NV) in mice with OIR. Molecular analysis revealed that Fzd7 may act through the activation of Wnt/ß-catenin and Jagged1 expression to control EC proliferation in extra-retinal neovessels. We identified Fzd7/ß-catenin signaling as new regulator of pathological retinal NV. Fzd7 appears to be a potent pharmacological target to prevent or treat aberrant angiogenesis of ischemic retinopathies.

The Beneficial Effects of UM206 on Wound Healing After Myocardial Infarction in Mice Are Lost in Follow-Up Experiments.

Introduction: An inadequate wound healing following myocardial infarction (MI) is one of the main etiologies of heart failure (HF) development. Interventions aiming at improving this process may contribute to preserving cardiac function after MI. Our group, as well as others, have demonstrated the crucial role of Wnt/frizzled signaling in post-MI remodeling. In this overview, we provide the results of different studies aimed at confirming an initial study from our group, in which we observed beneficial effects of administration of a peptide fragment of Wnt5a, UM206, on infarct healing in a mouse MI model. Methods: Mice were subjected to permanent left coronary artery ligation, and treated with saline (control) or UM206, administered via osmotic minipumps. Cardiac function was assessed by echocardiography and hemodynamic measurements, while infarct size and myofibroblast content were characterized by (immuno)histochemistry. Results: In total, we performed seven follow-up studies, but we were unable to reproduce the beneficial effects of UM206 on infarct healing in most of them. Variations in dose and timing of UM206 administration, its manufacturer and the genetic background of the mice could not restore the phenotype. An in-depth analysis of the datasets revealed that the absence of effect of UM206 coincided with a lack of adverse cardiac remodeling and HF development in all experimental groups, irrespective of the treatment. Discussion: Irreproducibility of experimental observations is a major issue in biomedical sciences. It can arise from a relatively low number of experimental observations in the original study, a faulty hypothesis or a variation in the experimental model that cannot be controlled. In this case, the lack of adverse cardiac remodeling and lung weight increases in the follow-up studies point out to altered experimental conditions as the most likely explanation.

Neuroprotection mediated by the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage.

The Wnt/Frizzled signaling pathway participates in many inflammation-linked diseases. However, the inflammatory response mediated by the Wnt/Frizzled signaling pathway in experimental subarachnoid hemorrhage has not been thoroughly investigated. Consequently, in this study, we examined the potential role of the Wnt/Frizzled signaling pathway in early brain injury in rat models of subarachnoid hemorrhage. Simultaneously, possible neuroprotective mechanisms were also investigated. Experimental subarachnoid hemorrhage rat models were induced by injecting autologous blood into the prechiasmatic cistern. Experiment 1 was designed to examine expression of the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage. In total, 42 adult rats were divided into sham (injection of equivalent volume of saline), 6-, 12-, 24-, 48-, 72-hour, and 1-week subarachnoid hemorrhage groups. Experiment 2 was designed to examine neuroprotective mechanisms of the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage. Rats were treated with recombinant human Wnt1 (rhwnt1), small interfering Wnt1 (siwnt1) RNA, and monoclonal antibody of Frizzled1 (anti-Frizzled1) at 48 hours after subarachnoid hemorrhage. Expression levels of Wnt1, Frizzled1, ß-catenin, peroxisome proliferator-activated receptor-γ, CD36, and active nuclear factor-κB were examined by western blot assay and immunofluorescence staining. Microglia type conversion and inflammatory cytokine levels in brain tissue were examined by immunofluorescence staining and enzyme-linked immunosorbent assay. Our results show that compared with the sham group, expression levels of Wnt1, Frizzled1, and ß-catenin were low and reduced to a minimum at 48 hours, gradually returning to baseline at 1 week after subarachnoid hemorrhage. rhwnt1 treatment markedly increased Wnt1 expression and alleviated subarachnoid hemorrhage-induced early brain injury (within 72 hours), including cortical cell apoptosis, brain edema, and neurobehavioral deficits, accompanied by increasing protein levels of ß-catenin, CD36, and peroxisome proliferator-activated receptor-γ and decreasing protein levels of nuclear factor-κB. Of note, rhwnt1 promoted M2-type microglia conversion and inhibited release of inflammatory cytokines (interleukin-1ß, interleukin-6, and tumor necrosis factor-α). In contrast, siwnt1 RNA and anti-Frizzled1 treatment both resulted in an opposite effect. In conclusion, the Wnt/Frizzled1 signaling pathway may participate in subarachnoid hemorrhage-induced early brain injury via inhibiting the inflammatory response, including regulating microglia type conversion and decreasing inflammatory cytokine release. The study was approved by the Animal Ethics Committee of Anhui Medical University and First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China (approval No. LLSC-20180202) in May 2017.

Inhibition of α5 GABAA receptors has preventive but not therapeutic effects on isoflurane-induced memory impairment in aged rats.

The α5 subunit-containing gamma-amino butyric acid type A receptors (α5 GABAARs) are a distinct subpopulation that are specifically distributed in the mammalian hippocampus and also mediate tonic inhibitory currents in hippocampal neurons. These tonic currents can be enhanced by low-dose isoflurane, which is associated with learning and memory impairment. Inverse agonists of α5 GABAARs, such as L-655,708, are able to reverse the short-term memory deficit caused by low-dose isoflurane in young animals. However, whether these negative allosteric modulators have the same effects on aged rats remains unclear. In the present study, we mainly investigated the effects of L-655,708 on low-dose (1.3%) isoflurane-induced learning and memory impairment in elderly rats. Young (3-month-old) and aged (24-month-old) Wistar rats were randomly assigned to receive L-655,708 0.5 hour before or 23.5 hours after 1.3% isoflurane anesthesia. The Morris Water Maze tests demonstrated that L-655,708 injected before or after anesthesia could reverse the memory deficit in young rats. But in aged rats, application of L-655,708 only before anesthesia showed similar effects. Reverse transcription-polymerase chain reaction showed that low-dose isoflurane decreased the mRNA expression of α5 GABAARs in aging hippocampal neurons but increased that in young animals. These findings indicate that L-655,708 prevented but could not reverse 1.3% isoflurane-induced spatial learning and memory impairment in aged Wistar rats. All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Academy of Military Medical Science of China (approval No. NBCDSER-IACUC-2015128) in December 2015.