The Cell Tracking Challenge is an ongoing benchmarking initiative that has become a reference in cell segmentation and tracking algorithm development. Here, we present a significant number of improvements introduced in the challenge since our 2017 report. These include the creation of a new segmentation-only benchmark, the enrichment of the dataset repository with new datasets that increase its diversity and complexity, and the creation of a silver standard reference corpus based on the most competitive results, which will be of particular interest for data-hungry deep learning-based strategies. Furthermore, we present the up-to-date cell segmentation and tracking leaderboards, an in-depth analysis of the relationship between the performance of the state-of-the-art methods and the properties of the datasets and annotations, and two novel, insightful studies about the generalizability and the reusability of top-performing methods. These studies provide critical practical conclusions for both developers and users of traditional and machine learning-based cell segmentation and tracking algorithms. This updated analysis of the Cell Tracking Challenge explores how algorithms for cell segmentation and tracking in both 2D and 3D have advanced in recent years, pointing users to high-performing tools and developers to open challenges.

The blood-brain barrier is a unique physiological structure acting as a filter for every molecule reaching the brain through the blood. For this reason, an effective pharmacologic treatment supplied to a patient by systemic circulation should first be capable of crossing the barrier. Standard cell cultures (or those based on microfluidic devices) and animal models have been used to study the human blood-brain barrier. Unfortunately, these tools have not yet reached a state of maturity because of the complexity of this physiological process aggravated by a high heterogeneity that is not easily recapitulated experimentally. In fact, the extensive research that has been performed and the preclinical trials carried out provided sometimes contradictory results, and the functionality of the barrier function is still not fully understood. In this study, we have combined tissue clarification, advanced microscopy and image analysis to develop a one-dimensional computational model of the microvasculature hemodynamics inside the mouse brain. This model can provide information about the flow regime, the pressure field and the wall shear stress among other fluid dynamics variables inside the barrier. Although it is a simplified model of the cerebral microvasculature, it allows a first insight on into the blood-brain barrier hemodynamics and offers several additional possibilities to systematically study the barrier microcirculatory processes.

Unraveling the mechanisms of 5-HT neuron control might provide new insights into depression pathophysiology. In addition to the inhibitory 5-HT1A autoreceptors, cortico-raphe glutamatergic descending pathways are suggested to modulate 5-HT activity in the DRN. Here we studied how decreased VGLUT1 levels in the brain stem affect glutamate regulation of 5-HT function. VGLUT1+/- mice (C57BL/6) and wild type (WT) littermates were used. VGLUT1 expression in the DRN, 5-HT turnover and immuno histochemical analysis of neuronal activity in different areas was studied. Moreover, the functionality of the inhibitory 5-HT1A autoreceptor was assessed using electrophysiological, biochemical and pharmacological approaches. VGLUT1 immunoreactivity was markedly lower in the DRN of the VGLUT1+/- mice and specifically, in the surroundings of GABA and 5-HT cell bodies. These mice showed decreased induced neuronal activity in 5-HT cells bodies and in different forebrain areas, as well as decreased hippocampal cell proliferation and 5-HT turnover. Further, 5-HT1A autoreceptor desensitization was evidenced by electrophysiological studies, GTP-¿-S coupling to 5-HT1A autoreceptor and a lower hypothermic response to 5-HT1A activation. This study shows first time that VGLUT1 dependent glutamate innervation of the DRN could modulate 5-HT function.