Regeneration of bone defects remains a critical challenge in orthopaedics. Mesenchymal stromal cells (MSC) with biomaterials show huge promise for bone regeneration. However, MSC die shortly after implantation and act as mediators, by secretion of paracrine factors (PF), rather than effectors of bone formation. Importantly, it seems that delivery of cells themselves may not be required for therapeutic benefit. When MSC are cultured in vitro they release PF into their conditioned media (MSC-CM) including cytokines and extracellular vesicles. The goal of this project is to prepare novel biomaterials which are loaded with MSC-CM for in situ bone tissue engineering. PF secreted into MSC-CM during normoxia, hypoxia, and cell death will be measured. Biomaterials (biphasic calcium phosphate ceramics) will be functionalized with MSC-CM by using the polyelectrolyte multi-layering (PEM) method. The biocompatibility, release kinetics, and potential of MSC-CM loaded biomaterials for bone regeneration will be tested in vitro on cells involved in bone formation (MSC, monocytes, osteoclasts, macrophages, and endothelial cells) and in vivo by implanting the biomaterials in subcutis sites and segmented femoral defects in nude mice. Importantly, the delivery of MSC-CM can overcome the donor-dependent variability in bone formation associated with MSC cell therapy and permits a more straightforward transfer of this therapy to clinical treatment. Since MSC-CM is devoid of cells and doesn’t carry patient rejection risk, autologous MSC are not required. Therefore, selected MSC that successfully induce bone formation can be used to collect potent MSC-CM which can be loaded onto biomaterials for therapeutic use in countless patients. An ‘off-the-shelf’ product that could harness the benefits of MSC therapy but circumvent the costly and time consuming multi-step procedures involved with MSC implantation would be of immense interest to the bone regeneration field.

Amyotrophic Lateral Sclerosis (ALS) is the most common adult-onset neurodegenerative disease of the motor system, with a prevalence of 2-3/100 000. In spite of intensive research efforts, ALS remains an incurable disease and presents with a very severe prognosis, leading to patient death within 2 to 5 years following diagnosis. At the cellular level, ALS is characterized by the combined degeneration of both upper motor neurons (UMN, or corticospinal motor neurons) whose cell bodies are located in the cerebral cortex, and that extend axons to the medulla and spinal cord, and lower motor neurons (LMN, or spinal motor neurons) whose cell bodies are located in the medulla and spinal cord, and that connect to the skeletal muscles. This dual impairment allows to discriminate ALS from other, less severe diseases affecting either UMN or LMN. Despite this precise clinical description, it is striking to note that preclinical studies have so far mostly concentrated on LMN, leaving aside the role of UMN in ALS. This project aims at shedding light on the contribution of the dysfunction and/or the loss of UMN in ALS, in order to design and test new therapeutic strategies based on the protection and/or the replacement of this exact neuronal type. This innovative question has never been directly asked so far. Our working hypothesis is that specific neurodegeneration of UMN, in the course of ALS, does not represent an isolated side effect, but rather actively contributes to the onset and progression of the disease. Based on the discovery of new molecular players, and the development of alternative therapies, this original thematic has the ambition to provide clinicians and patients with new answers and new therapeutic assets.

Proteins hosting regions highly enriched in one or few amino acids, the so-called Low-Complexity Regions (LCR), are very common in eukaryotes and play crucial roles in biology. Homorepeats, a subfamily of LCR that present stretches of the same amino acid, perform very specialized functions facilitated by the localized enrichment of the same physicochemical property. In contrast, numerous severe pathologies have been associated to abnormally long repetitions. Despite the relevance of homorepeats, their high-resolution characterization by traditional structural biology techniques is hampered by the degeneracy of the amino acid environments and their intrinsic flexibility. In chemREPEAT, I will develop strategies to incorporate isotopically labelled and unnatural amino acids at specific positions within homorepeats that will overcome present limitations. These labelled positions will be unique probes to investigate for first time the structure and dynamics of homorepeats at atomic level using complementary biophysical techniques. Computational tools will be specifically developed to derive three-dimensional conformational ensembles of homorepeats by synergistically integrating experimental data. chemREPEAT strategies will be developed on huntingtin (Htt), the prototype of repetitive protein. Htt hosts a glutamine tract that is linked with Huntington’s disease (HD), a deadly neuropathology appearing in individuals with more than 35 consecutive Glutamine residues that represent a pathological threshold. The application of the developed approaches to several Htt constructions with different number of Glutamines will reveal the structural bases of the pathological threshold in HD and the role played by the regions flanking the Glutamine tract. The strategies designed in chemREPEAT will expand present frontiers of structural biology to unveil the structure/function relationships for LCRs. This capacity will pave the way for a rational intervention in associated diseases.

Our understanding of ion channel operation is limited to inferences based on functional data and to static snapshots of their structures where they are available. Cyclic nucleotide-modulated channels and calcium-activated K+ channels play crucial roles in a myriad of physiological processes ranging from signal transduction to neuronal excitability. The binding of ligands to specialized intracellular domains modulates the opening/closing (gating) equilibrium of these channels. Both the high resolution structures - in open and closed conformation - of these channels and the precise mechanism of ligand-mediated channel activation are unknown. The present proposal aims to understand the mechanism of ion channel modulation by ligands. To accomplish this goal we will utilize prokaryotic homologues of these channels reconstituted in artificial membranes. High-speed atomic force microscopy (HS-AFM) will allow us to directly observe individual ion channel molecules in action at high spatiotemporal resolution and in physiological conditions. Through UV-laser pulses caged ligands (caged-Ca2+ or caged-cAMP) will be liberated during HS-AFM imaging and the conformational changes associated to ligand binding monitored in real time. Differences between liganded and unliganded channel structures will provide insight into the mechanism of ligand gating. The obtained data will be compared to single channel current recordings under comparable conditions.

The metabolic syndrome (MetS) represents one of the major public health challenges worldwide. It reflects a combination of medical disorders that, when occurring together, increase the risk of developing diabetes and cardiovascular disease. The prevalence in the USA is estimated at 30% of the population and the European community follows this trajectory. It is now recognized that the state of chronic low-grade inflammation may favor the onset and progression of the MetS. While the notion of metabolic flexibility in hematopoietic cells has recently emerged in several inflammatory diseases, the origin of this immunometabolic alteration in the MetS remains elusive. There is a growing appreciation that the apportioning of nutrients into different metabolic pathways can support or direct functional immune and hematopoietic changes. Glutamine is the most abundant amino acid in the plasma and an important energy source through glutaminolysis. Despite its potential proliferative and/or immunosuppressive function and the strong association between high glutamine-to-glutamate ratio with cardiometabolic traits, the underlying mechanisms are poorly understood. Thus, there is a considerable therapeutic interest in better understanding the mechanisms linking glutamine to cardiometabolic risks and in particular cardiometabolic inflammation. In PROGLUTASIS, we will investigate the metabolic and immune regulation of glutamine homeostasis in the metabolic syndrome. We will validate the contribution of glutaminolysis in cardiometabolic inflammation, including obesity, diabetes and atherosclerosis through its role on hematopoiesis and macrophage dynamics. Given the ubiquitous association between glutamine and chronic metabolic stress, we expect that identifying the underlying molecular mechanism will offer novel therapeutic perspective on how to intervene in this pathway. This will ultimately allow for tailored strategies aimed at dampening cardiometabolic inflammation in the MetS.