Biology subjects

Passini, F. S.

Publications and source records attributed to Passini, F. S..

4 recordsLinked to original sources

bioRxiv2025

Matrix maturation and cytoskeletal tension define strain thresholds for stretch-induced calcium signaling in human tendon cells

The extracellular matrix (ECM) and mechanical loading shape cellular behavior, yet their interaction remains obscure. We developed a dynamic proto-tissue model using human tendon cells and live-cell calcium imaging to study how ECM and cell mechanics regulate mechanotransduction. Stretch-induced calcium signaling served as a functional readout. We discovered that ascorbic acid-dependent ECM deposition is essential for proto-tissue maturation and stretch-induced calcium signaling at physiological strains. Proto-tissue maturation enhanced stretch sensitivity, reducing the strain needed to trigger a calcium response from [~]40% in isolated cells to [~]5% in matured proto-tissues. A strong correlation between tissue rupture and calcium signaling suggests a mechanistic link to ECM damage. Disrupting ECM integrity, cell alignment, or cytoskeletal tension reduced mechanosensitivity, showcasing the influence of ECM and cytoskeletal mechanics on stretch-induced calcium signaling. Fundamentally, our work replicates calcium signaling observed in rodent tendon explants in vitro and bridges the gap between cell-scale and tissue-scale mechanotransduction. TeaserMatrix matters: tendon cells tune their response to stretch as their mechanical environment develops.

bioengineering↗

bioRxiv2025

HIF1α gates tendon response to overload and drives tendinopathy independently of vascular recruitment

Tendons are mostly avascular dense connective tissues that link muscles to bones, withstanding some of the highest mechanical stresses in the body. Mechanical overload and tissue hypervascularity are implicated in tendinopathy, a common musculoskeletal disorder, but mechanistic understanding of their roles is largely lacking. Here, we identify HIF1 not only as a marker but as a driver of tendinopathy. Initial histological and multi-omics evaluation of human tendinopathic samples revealed extensive extracellular matrix remodeling, including pathological collagen crosslinking coinciding with active hypoxic signaling. Hypothesizing a causal contribution of hypoxia signaling, we generated mice with tenocyte-targeted deletions of the Von Hippel-Lindau (VHL) gene, which controls hypoxia signaling by regulating HIF degradation. We demonstrated that VHL inactivation suffices to induce pathological hallmarks of tendinopathy, such as collagen matrix disorganization, crosslinking, altered mechanics and neuro-vascular ingrowth. This phenotype was HIF1-dependent, since co-deleting HIF1 rescued tendon morphology and mechanics. Moreover, deleting vascular endothelial growth factor A (VEGFA) alongside VHL effectively decoupled the effects of vascular ingrowth from persistently aberrant extracellular matrix remodeling and mechanical dysfunction, emphasizing a direct role of HIF1 in driving tendon disease that is independent of angiogenesis. Mechanistically, we linked tendon mechanical overload to the onset of HIF1 signaling in primary cultured human tendon cells. Furthermore, genetically removing HIF1 from tenocytes prevented aberrant tendon remodeling in response to chronic overload. These findings position HIF1 signaling as a central driver of tendinopathy that acts through a maladaptive tissue response to chronic overload, providing mechanistic insights that could be leveraged for improved therapeutic approaches. One Sentence SummaryHIF1 activation promotes tendinopathy and its inhibition prevents overload-induced maladaptation, suggesting therapeutic potential.

cell biology↗

bioRxiv2024

Wnt/β-Catenin coordinates muscle spindle development by regulating capsule differentiation, intrafusal fiber nuclei aggregation and proprioceptive nerve endings

Proprioception is essential for the regulation of posture, movement, and musculoskeletal integrity. The muscle spindle, a mechanosensory organ composed of multiple specialized tissues, detects stretch and provides proprioceptive feedback. Despite its importance, the molecular mechanisms that orchestrate the development of the spindle components remain poorly understood. Here, we reveal the involvement of the Wnt/{beta}-catenin pathway in muscle spindle development. We show that Wnt ligands and their Frizzled receptors are expressed in the developing spindle and that {beta}-catenin is active throughout development in capsule cells and in bag2 intrafusal fibers. Embryonic deletion of {beta}-catenin from capsule and intrafusal fibers induced widespread transcriptomic changes, which led to significant malformations, including impaired capsule cell differentiation, disrupted nuclear organization in intrafusal fibers, and disorganized proprioceptive nerve endings. Postnatal deletion of {beta}-catenin from intrafusal fibers resulted in abnormal nerve endings and impaired proprioceptive function, indicating that the development of proprioceptive afferents is regulated by {beta}-catenin through a non-cell-autonomous mechanism acting in bag2 fibers. Collectively, our findings position the Wnt/{beta}-catenin pathway as a central regulator that acts through both cell-autonomous and non-cell-autonomous mechanisms to coordinate the development of the various spindle tissues into a functional organ.

developmental biology↗

bioRxiv2024

Piezo2 in sensory neurons influences systemic and adipose tissue metabolism

Systemic metabolism ensures energy homeostasis through inter-organ crosstalk regulating thermogenic adipose tissue. Unlike the well-described inductive role of the sympathetic system, the inhibitory signal ensuring energy preservation remains poorly understood. Here, we show that, via the mechanosensor Piezo2, sensory neurons regulate morphological and physiological properties of brown and beige fat and prevent systemic hypermetabolism. Targeting Runx3/PV sensory neurons in independent genetic mouse models resulted in a systemic metabolic phenotype characterized by reduced body fat and increased insulin sensitivity and glucose tolerance. Deletion of Piezo2 in PV sensory neurons reproduced the phenotype, protected against high-fat diet-induced obesity and caused adipose tissue browning and beiging, likely driven by elevated norepinephrine levels. Finding that brown and beige fat are innervated by Runx3/PV sensory neurons expressing Piezo2, suggests a model where mechanical signals sensed by Piezo2 in sensory neurons protect energy storages and prevent a systemic metabolic phenotype. HighlightsLack of Runx3/PV sensory neurons reduces body fat and fasting glucose levels and increases glucose tolerance in mice Mechanosensitive ion channel PIEZO2 in PV sensory neurons plays an important role in systemic metabolism under physiological and pathological conditions PIEZO2 in PV sensory neurons regulates thermogenic programs and glucose uptake in brown and beige adipose tissues Brown and beige adipose tissues are innervated by Runx3/PV sensory neurons

physiology↗