Biology subjects

Lo Celso, C.

Publications and source records attributed to Lo Celso, C..

9 recordsLinked to original sources

bioRxiv2026

Intravital microscopy and statistical image analysis of early engraftment of haematopoietic stem cells reveal dynamic and evolving cellular behaviours linked to progressive differentiation.

Haematopoietic stem cells (HSCs) have long been used in the clinic for bone marrow transplantation applications, critical for the survival of an increasingly wide range of patients with haematological, oncological and immunological pathologies. Despite this, little is known about the mechanisms through which relatively few stem cells are able to regenerate the entire haematopoietic tissue of transplant recipients. To gain insights on this biological process, we used intravital microscopy of calvarium bone marrow, collecting tissue-wide images and a total of 850 hours of tracks of engrafting haematopoietic stem and progenitor cells from 24 hours to 8 days following injection in lethally irradiated recipients. Analysis of the data revealed that regenerating HSCs and their immediate progeny are highly dynamic, migrating through the parenchyma at both the microscopic and near-macroscopic scales, i.e. within and in-and-out of fields of view. HSC-derived cell clusters, expanded locally between day 2 and day 4 post-transplant, leading to patches of densely populated bone marrow by day 8. Single cell level analysis highlighted increasingly heterogenous cellular behaviours over time. Track clustering based on migration and niche interaction parameters combined with post-tracking whole mount immunostaining revealed that persistence in the vicinity of nestin-GFP perivascular cells and relatively slow movement correlated with stemness, while more heterogeneous niche interactions coupled with slowest or faster migration correlated with differentiation, validated through flow cytometry analysis and functional studies. The findings presented here shed light on the fundamental principles driving haematopoietic regeneration in transplantation settings.

developmental biology↗

bioRxiv2026

A combined program of induced stemness and differentiation in response to interferon gamma drives acute myeloid leukaemia growth

How inflammation shapes acute myeloid leukaemia (AML) has come under scrutiny, as it may explain the disease resistance to immunotherapy approaches. IFNg has emerged as a key cytokine with paradoxical roles in suppressing and supporting AML growth, and the fundamental question of how leukemic stem cells (LSCs) respond to IFNg and whether IFNg signaling influences LSC quiescence and their capacity to regenerate disease over the long term remains unanswered. Here, we study primary human AML cells and murine models and combine bioinformatics analyses and functional assays to show that AML hierarchical heterogeneity is responsive to IFNg challenge. We uncover that IFNg triggers parallel stemness and differentiation programs; HSC/MPP-like cells enter deeper stemness, associated with quiescence and high leukaemia regeneration potential, while the surviving pool of progenitor-like cells divides faster but produces progeny that is quickly lost. Finally, with murine models we show that exposure to inflammation in vivo results in only transient impairment of leukaemia propagating capacity. This mechanism is driven by a previously unrecognised intraclonal fate bifurcation, relevant for the development of more effective therapeutic approaches.

cancer biology↗

bioRxiv2025

A new double reporter strategy reveals a subset of non-migratory hematopoietic stem cells localized in a dynamic bone marrow niche.

Interactions of hematopoietic stem cells (HSCs) with the bone marrow microenvironment are critical to regulate stem cell function in homeostasis, emergency hematopoiesis and ageing. The dynamic behavior of endogenous HSCs in their niches has been challenging to study due to the complexity of markers required to define pure HSCs. Multiple recently developed reporter strategies advanced our capacity to identify HSCs in situ. Yet, they provide different levels of HSC enrichment and are frequently not stable in situations of perturbed hematopoiesis, leading to contradictory observations of HSC migratory behavior. Here we employed a new double reporter strategy by combining the Hoxb5-mKO2 and Vwf-GFP reporters, that are stably expressed in homeostasis, stress and ageing. Hoxb5+Vwf+ cells represent a subset of highly pure and potent long-term HSCs with a platelet-biased pattern of differentiation, that are included in the populations identified by other reporter strategies. Intravital microscopy revealed Hoxb5+Vwf+ cells to be non-migratory in homeostasis, following platelet depletion when these cells are actively proliferating, and during ageing. This non-migratory behavior of HSCs in homeostasis and stress indicates that their activation does not inherently depend on relocation to alternative niches eliciting proliferation, as previously proposed. We found Hoxb5+Vwf+ HSCs in direct contact with vasculature and LepR+ perivascular cells but not preferentially closer to megakaryocytes. Nevertheless, increased megakaryopoiesis following platelet depletion brings megakaryocytes into close proximity of Hoxb5+Vwf+ HSCs, revealing previously unrecognized niche dynamics in HSC regulation during regeneration. DATA SHARING STATEMENTOriginal data will be made available upon reasonable request. The RNA sequencing data used in this study has been published before35 and is available from GEO (GSE81682). The code used for analysis is available from https://github.com/loversaber/Secchi_Paper_RNAseq_Analysis.git. KEY POINTSO_LICombined expression of Hoxb5-mKO2 and Vwf-GFP reporters defines a population of highly enriched long-term HSCs in situ and in vivo. C_LIO_LIHoxb5+Vwf+ HSCs are non-migratory in homeostasis, stress hematopoiesis and ageing, while their niche is highly dynamic. C_LI

cell biology↗

bioRxiv2025

Optimizing scheduling in dual-pulse nucleoside labeling experiments for cell cycle analysis

All eukaryotic cells go though a universal sequence of phases during their division cycle, where the phase timings vary according to cell type and state. Dual-pulse nucleoside labeling (DPNL) is a standard, widely applicable experimental technique to probe cell cycle kinetics at the population level, including in living organisms. In such an experimental protocol, a key scheduling parameter is the choice of waiting time between the two labeling pulses. Here, we use simulation to show that the waiting time can be optimized with regards to the signal-to-noise ratio of the cycle parameters as inferred from experimental outputs, which is of particular importance in DPNL experiments with small numbers of cells and repeats. We further discuss the procedure to perform such a task in an experimentally relevant setting.

biophysics↗

bioRxiv2025

Clonal memory of cell division in humans diverges between healthy haematopoiesis and acute myeloid leukaemia

Clonal memory, a cellular property inherited across at least two divisions, has emerged as a key driver of cell heterogeneity. To uncover its roles in human haematopoiesis, we developed high-resolution ex vivo tools that track both division and fate commitment of individual primary human haematopoietic stem and progenitor cells (HSPCs). We show that human HSPCs display a clonal memory of division, as cells descending from the same ancestor cell divide synchronously over multiple generations. In parallel, HSPCs inherit a clonal memory of fate commitment, independently of lineage identity. Both forms of clonal memory persist over at least two divisions, across different HSPC commitment stages and cell culture conditions. In contrast, malignant haematopoiesis exhibits lower synchronicity, revealing a disruption of clonal memory in leukemic cells. Epigenetic remodelling using a bromodomain inhibitor partially restores the clonal memory in division in leukemic HSPCs, highlighting the plasticity of this trait and its potential for therapeutic modulation. Our findings position clonal memory as a key regulator of human haematopoietic stem cell behaviour. Demonstrating that clonal memory can be modulated opens new avenues for tuning cell heterogeneity in healthy and pathological tissues.

cell biology↗

bioRxiv2022

A practical extraction and spatial statistical pipeline for large 3D bioimages

ABSTRACT/SUMMARYDespite much being known about the molecular regulation of hematopoiesis, little is understood about how hematopoietic cells are organized within bone marrow (BM) tissue. Recent advances in microscopy have led to the creation of increasingly detailed images of murine hematopoietic tissue. Accurate, efficient, and informative methodologies to extract and analyze the large amount of data generated are, however, still lacking. Indeed, cells are very densely packed in the bone marrow and therefore difficult to efficiently and accurately segment. In addition, currently employed statical analyses of cellular localization are generally unsuitable for the investigation of interactions between more than two cell types. To overcome these limitations, we developed PACESS, a readily applicable method based on neural network classification of hundreds of thousands of cells in thick 3D bone marrow samples, and a combination of statistical techniques to assess the spatial interactions between multiple cell types. To validate this approach, we used it to investigate the spatial organization of T cells, megakaryocytes and leukemic cells. We demonstrate that the presence of large clusters of leukemic cells affects the distribution of both T cells and megakaryocytes, albeit differently, resulting in the generation of previously unrecognized, unique microenvironments adjacent to each other within the same bone marrow cavity. We believe that this approach can contribute to unravel the BM cellular organization. MOTIVATIONThe organization of diverse hematopoietic cells within bone marrow tissue remains unclear. Recently developed tissue clearing methods enable the generation of large, 3D, single cell resolution microscopy images datasets, but the bottleneck in their analysis lies in both the identification and classification of cells, and in statistical analyses to probe their spatial relationships. We present a workflow (PACESS) that takes advantage of a convoluted neural network to identify and classify cells in 2D coupled with an automated method that extrapolates to 3D, followed by a combination of spatial statistics to classify tissue regions based on each cell types density, and logistic regression to test whether the relative abundance of cell types may be explained by reciprocal dependencies. Finally, we provide a combined measurement of the abundance of all cell types in a 3D map, highlighting regional variations found within the tissue. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC="FIGDIR/small/521787v3_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@4bcae8org.highwire.dtl.DTLVardef@1f676bcorg.highwire.dtl.DTLVardef@1ed38d3org.highwire.dtl.DTLVardef@12de53b_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2021

Heterogeneous run-and-tumble motion accounts for transient non-Gaussian super-diffusion in haematopoietic multi-potent progenitor cells

Multi-potent progenitor (MPP) cells act as a key intermediary step between haematopoietic stem cells and the entirety of the mature blood cell system. Their eventual fate determination is thought to be achieved through migration in and out of spatially distinct niches. Here we first analyze statistically MPP cell trajectory data obtained from a series of long time-course 3D in-vivo imaging experiments on irradiated mouse calvaria, and report that MPPs display transient super-diffusion with apparent non-Gaussian displacement distributions. Second, we explain these experimental findings using a run-and-tumble model of cell motion which incorporates the observed dynamical heterogeneity of the MPPs. Third, we use our model to extrapolate the dynamics to time-periods currently inaccessible experimentally, which enables us to quantitatively estimate the time and length scales at which super-diffusion transitions to Fickian diffusion. Our work sheds light on the potential importance of motility in early haematopoietic progenitor function.

biophysics↗

bioRxiv2020

The metalloproteinase inhibitor Prinomastat reduces AML growth,prevents stem cell loss and improves chemotherapy effectiveness

Acute myeloid leukemia (AML) is a blood cancer of the myeloid lineage. Its prognosis remains poor, highlighting the need for new therapeutic and precision medicine approaches. AML symptoms often include cytopenias, linked to loss of healthy hematopoietic stem and progenitor cells (HSPCs). The mechanism behind HSPC decline is complex and still poorly understood. Here, intravital microscopy (IVM) of a well-established experimental model of AML allows direct observation of the interactions between healthy and malignant cells in the bone marrow (BM), suggesting that physical dislodgment of healthy cells by AML through damaged vasculature may play an important role. Numerous human leukemia types, particularly MLL-AF9 samples, show high expression levels of multiple matrix metalloproteinases (MMPs). Therefore, we evaluate the therapeutic potential of the MMP inhibitor (MMPI) prinomastat. IVM analyses of treated mice reveal reduced vascular permeability and healthy cell clusters in circulation, and lower AML cell speed. Furthermore, treated mice have decreased BM infiltration, increased retention of healthy HSPCs in the BM and increased survival following chemotherapy. Overall, our results suggest that MMPIs could be a promising complementary therapy to reduce AML growth and limit the loss of HSPC and BM vascular damage caused by MLL-AF9 and possibly other AML subtypes.

cancer biology↗

bioRxiv2018

Malaria-induced remodelling of the bone marrow microenvironment mediates loss of haematopoietic stem cell function

Severe infections are a major source of stress on haematopoiesis, where consequences for haematopoietic stem cells (HSCs) have only recently started to emerge. HSC function critically depends on the integrity of complex bone marrow niches, which have been shown to be altered during ageing and haematopoietic malignancies. Whether the bone marrow (BM) microenvironment plays a role in mediating the effects of infection on HSCs remains an open question. Here we used an murine model of malaria coupled with intravital microscopy, single cell RNA-Seq, mathematical modelling and transplantation assays to obtain a quantitative understanding of the proliferation dynamics of haematopoietic stem and progenitor cells (HSPCs) during Plasmodium infection. We uncovered that during Plasmodium infection the HSC compartment turns over significantly faster than in steady state, and that a global interferon response and loss of functional HSCs are linked to alterations in BM endothelium function and osteoblasts number. Interventions that targeted osteoblasts uncoupled HSC proliferation and function, thus opening up new avenues for therapeutic interventions that may improve the health of survivors of severe infections.

cell biology↗