Biology subjects

Donsante, S.

Publications and source records attributed to Donsante, S..

4 recordsLinked to original sources

bioRxiv2025

Inheritance entropy quantifies epigenetic regulation of cell-cycle exit in human bone marrow stromal cells

Human bone marrow stromal cells (BMSC) include skeletal stem cells with ground-breaking the-rapeutic potential. However, BMSC colonies have very heterogeneous in vivo behaviour, due to their different potency; this unpredictability is the greatest hurdle to the development of skeletal regeneration therapies. Colony-level heterogeneity urges a fundamental question: how is it possible that one colony as a collective unit behaves differently from another one? If cell-to-cell variability were just an uncorrelated random process, a million cells in a transplant-bound colony would be enough to yield statistical homogeneity, hence washing out any colony-level traits. A possible answer is that the differences between two originating cells are transmitted to their progenies and collectively persist through an hereditary mechanism. But non-genetic inheritance remains an elusive notion, both at the experimental and at the theoretical level. Here, we prove that heterogeneity in the lineage topology of BMSC clonal colonies is determined by heritable traits that regulate cell-cycle exit. The cornerstone of this result is the definition of a novel entropy of the colony, which measures the hereditary ramifications in the distribution of inactive cells across different branches of the proliferation tree. We measure the entropy in 32 clonal colonies, obtained from single-cell lineage tracing experiments, and show that in the greatest majority of clones this entropy is decisively smaller than that of the corresponding non-hereditary lineage. This result indicates that hereditary epigenetic factors play a major role in determining cycle exit of bone marrow stromal cells.

biophysics↗

bioRxiv2025

Exploring the mechanism and pattern of bone formation during RANKL inhibition in a mouse model of fibrous dysplasia

Fibrous dysplasia (FD) of bone is a genetic fibro-osseous disorder with increased bone remodeling activity. Inhibition of RANKL modifies FD lesions by inducing the replacement of the fibrous tissue with bone. This effect was observed in FD murine models receiving anti-mouse RANKL antibodies or small molecule RANKL inhibitors and in FD patients treated with denosumab. However, in neither case the mechanism and pattern of deposition of the newly formed bone were clarified. We performed radiographic, morphological and molecular analyses on EF1-GsR201C (FD) mice receiving an anti-mouse RANKL antibody. We observed that RANKL inhibition caused a decrease in the expression of genes involved in osteogenesis, osteoclastogenesis, matrix remodeling and osteoblast-osteoclast cross-talk in affected skeletal segments. Nonetheless, intra-lesional bone surfaces were covered by a continuous layer of osteoid, indicating that bone formation was actively ongoing in the pathological tissue in spite of the treatment. Accordingly, all bone surfaces within FD lesions showed calcein labeling which was never detected in the fibrous tissue far from bone. These results indicate that in the absence of RANKL activity, bone formation in FD tissue does not occur diffusely or stochastically. In contrast, it is restricted to bone surfaces where osteoprogenitor cells are orderly recruited from the adjacent fibrosis, progressively converting it into bone. Clinically, this suggests that the volume of pre-treatment bone in FD lesions may be a determinant of the skeletal improvement that individual patients may achieve during the same denosumab treatment course. As a consequence, it may also be a determinant of the severity of the rebound effect that they can experience upon treatment discontinuation.

pathology↗

bioRxiv2025

Topology, Kinetics and Inheritance in Clonal Colonies of Bone Marrow Stromal Cells

Bone marrow stromal cells (BMSC) - which include skeletal stem cells - are a promising tool in regenerative medicine. However, their heterogeneous and unpredictable in vivo behaviour remains a critical barrier preventing the development of standardized therapeutic approaches for skeletal tissue regeneration. Several studies have attempted to identify in vitro features that could correlate with the in vivo differentiation properties, yet the mechanisms ruling BMSC heterogeneity remain poorly understood. Here, using time-lapse imaging, we lineage-trace 32 single-cell-derived BMSC colonies through seven generations. We observe significant inter-colony and intra-colony heterogeneity in lineage topology (determined by the number of senescent or apoptotic cells) and in replicative kinetics (measured from proliferating cells only). Interestingly, topology and kinetics result strongly correlated, suggesting the existence of regulatory factors linking the non-dividing/apoptotic subpopulations with proliferating cells. Furthermore, BMSCs display highly synchronized cell cycles during early generations, indicating stage-specific regulatory mechanisms through which cells influence each other. By employing a non-interacting population growth model, we demonstrate that the observed synchronisation cannot be explained by an uncorrelated branching process; instead, cell-to-cell correlation of division times must exist. Our findings reveal fundamental mechanisms governing BMSC heterogeneity and growth dynamics that may inform strategies to control their regenerative potential.

biophysics↗

bioRxiv2024

Bone pain in Fibrous dysplasia does not rely on aberrant sensory nerve sprouting or neuroma formation

Bone pain is a major symptom of many skeletal disorders. Fibrous dysplasia (FD) is a genetic disease with mono or polyostotic skeletal phenotype due to the post-zygotic occurrence of the causative Gs mutation. Bone pain in FD often associates with skeletal deformities and fractures or nerve impingement by the pathological tissue. However, even in the absence of complications, FD patients often complain of a chronic pain that does not correlate with their disease burden. Multiple hypotheses have been made to explain this pain. However, its pathogenetic mechanisms remain, as yet, largely unexplored. In this study, we first demonstrate that the FD mouse model EF1-GsR201C develops a painful-like behavior and an altered response to nociceptive stimuli that, as in FD patients, do not correlate with the severity of their phenotype, thus providing a reliable model to study bone pain in FD. Then, we show that in EF1-GsR201C mice, the overall pattern of skeletal innervation is preserved and that within FD lesions, sensory fibers are variably and focally distributed, mainly at perivascular sites. Finally, we provide the first analysis of a series of human FD bone biopsies showing that sensory nerve fibers are rarely detected within the pathological tissue. These data confirm that bone pain is an intrinsic and reproducible feature of FD. They also show that, albeit sensory nerve fibers are found within FD lesions and may contribute to the unpleasant sensation that accompanies the disease, pathological sensory nerve sprouting or formation of neuromas are not detected in the Gs-mutated skeleton.

pathology↗