Biology subjects

Batoon, L.

Publications and source records attributed to Batoon, L..

4 recordsLinked to original sources

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↗

bioRxiv2021

Osteomacs support osteoclast-mediated resorption and contribute to bone pathology in a postmenopausal osteoporosis mouse model

Osteal macrophages (osteomacs) support osteoblast function and promote bone anabolism, but their contribution to osteoporosis has not been explored. While mouse ovariectomy models have been repeatedly used, variation in strain, experimental design and assessment modalities, have contributed to no single model being confirmed as comprehensively replicating the full gamut of osteoporosis pathological manifestations. We validated an ovariectomy model in adult C3H/HeJ mice and demonstrated that it presents with human post-menopausal osteoporosis features, including reduced bone volume in axial and appendicular bone and bone loss in both trabecular and cortical bone including increased cortical porosity. Bone loss was associated with increased osteoclasts on trabecular and endocortical bone and decreased osteoblasts on trabecular bone. Importantly, this OVX model was characterised by delayed fracture healing. Using this validated model, we demonstrated that osteomacs are increased post-ovariectomy on both trabecular and endocortical bone. Dual F4/80 (pan-macrophage marker) and TRAP staining revealed osteomacs frequently located near TRAP+ osteoclasts and containing TRAP+ intracellular vesicles. Using an in vivo inducible macrophage depletion model that does not simultaneously deplete osteoclasts, we observed that osteomac loss was associated with elevated extracellular TRAP in bone marrow interstitium and increased serum TRAP. Using in vitro high-resolution confocal imaging of mixed osteoclast-macrophage cultures on bone substrate, we observed macrophages juxtaposed to osteoclast basolateral functional secretory domains scavenging degraded bone by-products. These data demonstrate a role for osteomacs in supporting osteoclastic bone resorption through phagocytosis and sequestration of resorption by-products. Finally, using Siglec1 knockout mice, we demonstrated that loss of the macrophage-restricted molecule Siglec-1/CD169 is sufficient to cause age-associated low bone mass, emphasizing the macrophages, independent of osteoclasts, contribute to optimal skeletal health. Overall, our data expose a novel role for osteomacs in supporting osteoclast function and provide the first evidence of their involvement in osteoporosis pathogenesis.

immunology↗

bioRxiv2020

CSF1R-dependent macrophages control postnatal somatic growth and organ maturation.

Homozygous mutation of the Csf1r locus (Csf1rko) in mice, rats and humans leads to multiple postnatal developmental abnormalities. To enable analysis of the mechanisms underlying the phenotypic impacts of Csf1r mutation, we bred a rat Csf1rko allele to the inbred dark agouti (DA) genetic background and to a Csf1r-mApple reporter transgene. The Csf1rko led to almost complete loss of embryonic macrophages and ablation of most adult tissue macrophage populations. We extended previous analysis of the Csf1rko phenotype to early postnatal development to reveal impacts on musculoskeletal development and proliferation and morphogenesis in multiple organs. Expression profiling of 3-week old wild-type (WT) and Csf1rko livers identified 2760 differentially expressed genes associated with the loss of macrophages, severe hypoplasia, delayed hepatocyte maturation, disrupted lipid metabolism and the IGF1/IGF binding protein system. Older Csf1rko rats developed severe hepatic steatosis. Consistent with the developmental delay in the liver Csf1rko rats had greatly-reduced circulating IGF1. Transfer of WT bone marrow (BM) cells at weaning without conditioning repopulated resident macrophages in all organs, including microglia in the brain and reversed the mutant phenotypes enabling long term survival and fertility. WT BM transfer restored osteoclasts, eliminated osteopetrosis, restored bone marrow cellularity and architecture and reversed granulocytosis and B cell deficiency. Csf1rko rats had an elevated circulating CSF1 concentration which was rapidly reduced to WT levels following BMT. However, CD43hi non-classical monocytes, absent in the Csf1rko, were not rescued and bone marrow progenitors remained unresponsive to CSF1. The results demonstrate that the Csf1rko phenotype is autonomous to BM-derived cells and indicate that BM contains a progenitor of tissue macrophages distinct from hematopoietic stem cells. The model provides a unique system in which to define the pathways of development of resident tissue macrophages and their local and systemic roles in growth and organ maturation.

developmental biology↗

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↗