Biology subjects

Guimaraes, S. C.

Publications and source records attributed to Guimaraes, S. C..

4 recordsLinked to original sources

bioRxiv2025

Matrix stress-relaxation and stiffness modulate oligodendrocyte differentiation

Impaired remyelination capacity, observed not only in demyelinating diseases of the central nervous system (CNS) but also in the aging brain, features a critical challenge in neural repair. Dysfunctional oligodendrocytes (OLs) are not able to efficiently restore myelin sheaths leading to increased axonal susceptibility to degeneration. Inhibitory cues to OL myelination have been described but strategies promoting remyelination keep failing. Recently acknowledged as key regulators of cellular fate and behavior, physical properties are emerging as novel potential targets in remyelination. Yet, the full extent of this impact is unknown. So far, the viscoelastic properties of the brain have been overlooked, with studies assuming that it only possesses an elastic behavior. Here, we engineered mechanically tunable 3D alginate hydrogels for culturing OLs. While being structurally biologically relevant, our matrices can be modelled in terms of elastic and viscoelastic properties. For the first time, we proved that, in addition to elasticity, viscoelasticity highly impacts the behavior of OLs. High stress-relaxation and shear moduli hydrogels lead to impaired differentiation, branching ability and metabolic activity of OLs, without visible effects on cellular viability. We showed that tuning alginate stress-relaxation properties while maintaining the stiffness triggers activation of mechanotransduction genes. Alterations were seen in genes involved in the focal adhesion kinase pathway as well as in the transcriptional factors Yap 1 and Taz and at the level of nuclear mechanotransduction (Hdac1). Understanding how microenvironmental cues support OL viability and myelination might lead to the design of improved therapies promoting remyelination. Our tunable hydrogels are not only relevant to study OL mechanobiology but can also function as a relevant model to test novel therapeutic interventions in remyelination context.

neuroscience↗

bioRxiv2025

Engineered micropillars to unveil oligodendrocyte responses to physical cues

Destruction of myelin internodes, oligodendrocyte (OL) apoptosis, and axonal degeneration characterize diseased or aged central nervous systems. While OLs can partially regenerate myelin sheaths, the remyelination process ultimately fails. Tissue mechanical and physical properties, such as stiffness and axonal curvature, play a role in this process. However, the complexity of existing models has hindered studies of OL mechanobiology. Here, a tissue-engineered model is presented to investigate the impact of stiffness and axonal diameter on OL myelination. The model consists of poly(dimethylsiloxane) micropillars with biologically relevant diameters (1-5 {micro}m), tunable rigidity, and amenable for surface functionalization. The optimized method enables the production of high-aspect-ratio, transparent micropillar arrays, in a reproducible and scalable system, serving as surrogate axons. Additionally, new protocols for quantifying myelin formation are introduced, which can be adapted to any myelination studies. Softer micropillars accelerate OL differentiation, while rigid ones promote the maintenance of mature OL states. Wrapping of OLs increased with micropillar diameter on rigid substrates, but not on softer ones, suggesting a complex interplay between curvature and rigidity. These processes involve calcium-sensitive channels, histone deacetylases, and microtubules dynamics. The proposed platform constitutes a versatile and user-friendly system, with applications from fundamental myelin research to drug discovery.

bioengineering↗

bioRxiv2024

Engineered chitosan-derived nanocarrier for efficient siRNA delivery to peripheral and central neurons

Gene therapy using small interfering RNA (siRNA) holds promise for treating neurological disorders by silencing specific genes, such as the phosphatase and tensin homolog (PTEN) gene, which restricts axonal growth. Yet, delivering siRNA to neurons efficiently is challenging due to premature degradation and unspecific delivery. Chitosan-based delivery systems have shown great potential due to their well-established biocompatibility. However, their limited transfection efficiency and lack of neuronal tropism require further modification. Building on our previous successes with neuron-targeted DNA delivery using chitosan, a novel approach for siRNA delivery aimed at PTEN downregulation is proposed. This involves using thiolated trimethyl chitosan (TMCSH)-based siRNA nanoparticles functionalized with the neurotropic C-terminal fragment of the tetanus neurotoxin heavy chain (HC) for efficient delivery to both peripheral and central neurons. These polyplexes demonstrated suitable physicochemical properties, biocompatibility, and no adverse effects on neuronal electrophysiology. Diverse neuronal models, including 3D ex vivo cultures and microfluidics, confirmed polyplexes efficiency and neurospecificity. HC targeting significantly enhanced nanoparticle neuronal binding, and live cell imaging revealed five times faster retrograde transport along axons. Furthermore, siRNA delivery targeting PTEN promoted axonal outgrowth in embryonic cortical neurons. Thus, these polyplexes represent a promising platform for siRNA delivery, offering potential for clinical translation and therapeutic applications.

bioengineering↗

bioRxiv2024

Unveiling the potential of neuron-targeted dendriplexes for siRNA delivery using a PNS-CNS-on-Chip

Neurological disorders, a leading global cause of death, encompass conditions affecting the peripheral and central nervous systems (PNS and CNS, respectively). Limited axon regeneration is a significant challenge in these disorders, and it is linked to proteins like PTEN. RNA-based therapeutics, particularly siRNAs, hold potential for silencing these inhibitory pathways, but their clinical application is hindered by poor stability and cellular uptake. Our study addressed this challenge with the development of novel, fully biodegradable dendritic nanoparticles designed specifically for neuron targeting. These nanoparticles were functionalized with the neurotropic binding domain of tetanus toxin, enhancing selective neuronal targeting and cellular internalization. We demonstrated that these dendriplexes not only maintain biocompatibility and efficient siRNA delivery in neuronal cultures but also significantly enhance axonal growth, as shown in microfluidic models. In a groundbreaking PNS-CNS-on-Chip, dendriplexes exhibited effective migration from PNS to CNS neurons, highlighting their potential for targeted therapeutic delivery. This study pioneers the application of microfluidics to demonstrate the CNS targeting of dendriplexes, paving the way for innovative treatments in the field of nanomedicine.

bioengineering↗