Biology subjects

Levesque, J.-P.

Publications and source records attributed to Levesque, J.-P..

4 recordsLinked to original sources

bioRxiv2021

Spinal cord injury reprograms muscle fibro-adipogenic progenitors to formheterotopic bones within muscles

The cells-of-origin of neurogenic heterotopic ossifications (NHO), which develop frequently in the periarticular muscles following spinal cord injuries (SCI) and traumatic brain injuries, remain unclear because the skeletal muscle harbors two progenitor cell populations: satellite cells (SCs) which are myogenic, and fibro-adipogenic progenitors (FAPs) which are mesenchymal. Lineage-tracing experiments using the Cre recombinase /LoxP system were performed in two mouse strains with the fluorescent protein ZsGreen specifically expressed in either SCs or FAPs in the skeletal muscles under the control of the Pax7 or Prrx1 gene promotors respectively. These experiments demonstrate that following a muscle injury, SCI causes the upregulation of PDGFR on FAPs but not SCs and the failure of SCs to regenerate myofibers in the injured muscle, with instead reduced apoptosis and continued proliferation of muscle resident FAPs enabling their osteogenic differentiation into NHO. No cells expressing ZsGreen under the Prrx1 promoter were detected in the blood after injury suggesting that the cells-of-origin of NHO are locally derived from the injured muscle. We validated these findings in the human pathology using human NHO biopsies. PDGFR+ mesenchymal cells isolated from the muscle surrounding NHO biopsies could develop ectopic human bones when transplanted into immunocompromised mice whereas CD56+ myogenic cells had a much lower potential. Therefore, NHO is a pathology of the injured muscle in which SCI reprograms FAPs to uncontrolled proliferation and differentiation into osteoblasts.

pathology↗

bioRxiv2021

Interleukin-1 is overexpressed in injured muscles following spinal cord injury and promotes neurogenic heterotopic ossification

Neurogenic heterotopic ossifications (NHOs) form in periarticular muscles following severe spinal cord (SCI) and traumatic brain injuries. The pathogenesis of NHO is poorly understood with no effective preventive treatment. The only curative treatment remains surgical resection of pathological NHOs. In a mouse model of SCI-induced NHO that involves a transection of the spinal cord combined with a muscle injury, a differential gene expression analysis revealed that genes involved in inflammation such as interleukin-1{beta} (IL-1{beta}) were overexpressed in muscles developing NHO. Using mice knocked-out for the gene encoding IL-1 receptor (IL1R1) and neutralizing antibodies for IL-1 and IL-1{beta}, we show that IL-1 signaling contributes to NHO development following SCI in mice. Interestingly, other proteins involved in inflammation that were also overexpressed in muscles developing NHO, such as colony-stimulating factor-1, tumor necrosis factor or C-C chemokine ligand-2 did not promote NHO development. Finally using NHO biopsies from SCI and TBI patients, we show that IL-1{beta} is expressed by CD68+ macrophages. IL-1 and IL-1{beta} produced by activated human monocytes promote calcium mineralization of fibro-adipogenic progenitors isolated from muscles surrounding NHOs. Altogether these data suggest that interleukin-1 promotes NHO development in both humans and mice.

physiology↗

bioRxiv2021

Fragmentation of macrophages during isolation confounds analysis of single cell preparations from mouse hematopoietic tissues

Mouse hematopoietic tissues contain abundant and heterogeneous populations of tissue-resident macrophages attributed trophic functions in control of immunity, hematopoiesis and bone homeostasis. A systematic strategy to characterise macrophage subsets in mouse bone marrow (BM), spleen and lymph node, unexpectedly revealed macrophage surface marker staining typically emanated from membrane-bound subcellular remnants associated with unrelated cell types. Remnant-restricted macrophage-specific membrane markers, cytoplasmic fluorescent reporters and mRNA were all detected in non-macrophage cell populations including isolated stem and progenitor cells. The profile of macrophage remnant association reflects adhesive interactions between macrophages and other cell types in vivo. Applying this knowledge, reduced macrophage remnant attachment to BM granulocytes in Siglec1 deficient mice was associated with compromised emergency granulocytosis, revealing a function for Siglec1-dependent granulocyte-macrophage interactions. Analysis of published RNA-seq data for purified macrophage and non-macrophage populations indicates that macrophage fragmentation is a general phenomenon that confounds bulk and single cell analysis of disaggregated tissues.

immunology↗

bioRxiv2020

Stable colony stimulating factor 1 fusion protein treatment increases HSC pool and enhances their mobilisation in mice.

Prior chemotherapy and/or underlying morbidity commonly leads to poor mobilisation of hematopoietic stem cells (HSC) for transplantation in cancer patients. Increasing the number of available HSC prior to mobilisation is a potential strategy to overcome this deficiency. Resident bone marrow (BM) macrophages are essential for maintenance of niches that support HSC and enable engraftment in transplant recipients. Here we examined potential of donor treatment with colony stimulating factor-1 (CSF1) to modify the BM niche and expand the potential HSC pool for autologous transplantation. We administrated CSF1 Fc fusion protein (CSF1-Fc) to naive C57Bl/6 mice and assessed the impacts on HSC number and function and overall haematopoiesis. Outcomes were assessed by in situ imaging and ex vivo flow cytometry with functional validation by colony formation and competitive transplantation assay. CSF1-Fc treatment caused a transient expansion of monocyte-macrophage cells within BM and spleen at the expense of BM B lymphopoiesis and hematopoietic stem and progenitor cell (HSPC) homeostasis. During the recovery phase after cessation of CSF1-Fc treatment, normalisation of haematopoiesis was accompanied by an increase in the total available HSPC pool. In the spleen, increased HSC was associated with expression of the BM niche marker CD169 in red pulp macrophages. Pre-treatment with CSF1-Fc increased the number and reconstitution potential of HSPC in blood following a HSC mobilising regimen of granulocyte colony stimulating factor (G-CSF) treatment. These results indicate that CSF1-Fc conditioning could represent a therapeutic strategy to overcome poor HSC mobilisation and subsequently improve autologous or heterologous HSC transplantation outcomes. Key points1) Recovery from Fc-modified colony stimulating factor-1 (CSF1-Fc) treatment was accompanied by an increase in total haematopoietic stem cells. 2) Pre-conditioning with CSF1-Fc increased the reconstitution potential of blood after haematopoietic stem cell mobilisation.

cell biology↗