Biology subjects

Pospori, C.

Publications and source records attributed to Pospori, C..

8 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

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↗

bioRxiv2025

A subset of Haematopoietic Stem Cells resists Plasmodium infection-induced stress by uncoupling interferon sensing and metabolic activation

Hematopoietic stem cells (HSCs) sustain lifelong haematopoiesis as their progeny differentiate into all blood cell lineages. Homeostatic HSCs are mostly quiescent and only rarely divide, however their proliferation and differentiation rates can be modulated by external factors. Acute and chronic infections from a wide range of pathogens are known to challenge HSCs at the population level, being forced to respond to inflammation-mediated organismal demand to replenish the myeloid cell pool. However, less is known about the degree of heterogeneity in the HSCs response to inflammation at the single cell level. Here, using a natural murine malaria model and an NHS-ester biotin dilution assay we identify two subsets of HSCs, BiotinLo and BiotinHi, with distinct proliferation kinetics. Using combined functional, single-cell transcriptomics and phenotypic analyses, we uncover that BiotinHi HSCs remain highly functional despite expressing strong interferon response signatures. These infection-resistant HSCs express high levels of MHC II and are metabolically distinct from the remaining HSCs as they maintain less active mitochondria. These findings demonstrate that a likely reserve pool of HSCs remains highly functional during Plasmodium infection not because cells are shielded, but because they maintain a stemness associated metabolic profile despite effectively sensing inflammation.

cell biology↗

bioRxiv2024

SIRPalpha+ PD-L1+ bone marrow macrophages aid AML growth by modulating T cell function

Acute myeloid leukemia (AML) continues to have a poor prognosis due to its ability to relapse following initial response to chemotherapy. While immunotherapies hold the promise to revolutionize cancer treatment, AML has been particularly challenging to target. It is therefore important to better understand the relationship between AML cells and immune cells within the bone marrow (BM) microenvironment, where this disease grows. Here we focus on non-malignant BM macrophages, and using a combination of intravital microscopy, flow cytometry, transcriptomics and functional analyses we identify a subpopulation of immunomodulatory BM macrophages (IMMs) with a unique profile and function during AML progression. While the majority of macrophages are already being lost at early infiltration, IMMs are locally enriched. They are capable of efferocytosis and support AML growth through inhibition of T cells. Enrichment of IMMs in the BM of patients developing early relapse indicates that future development of interventions that target IMMs development and function may improve AML patients outcome.

cancer 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

Dynamic regulation of hierarchical heterogeneity in Acute Myeloid Leukemia serves as a tumor immunoevasion mechanism

Acute Myeloid Leukemia, a hematological malignancy with poor clinical outcome, is composed of hierarchically heterogeneous cells. We examine the contribution of this heterogeneity to disease progression in the context of anti-tumor immune responses and investigate whether these responses regulate the balance between stemness and differentiation in AML. Combining phenotypic analysis with proliferation dynamics and fate-mapping of AML cells in a murine AML model, we demonstrate the presence of a terminally differentiated, chemoresistant population expressing high levels of PDL1. We show that PDL1 upregulation in AML cells, following exposure to IFN{gamma} from activated T cells, is coupled with AML differentiation and the dynamic balance between proliferation, versus differentiation and immunosuppression, facilitates disease progression in the presence of immune responses. This microenvironment-responsive hierarchical heterogeneity in AML may be key in facilitating disease growth at the population level at multiple stages of disease, including following bone marrow transplantation and immunotherapy.

cancer biology↗