Carpenter, S. L. | Search bioRxiv

bioRxiv2024

Mathematical Modeling of Drug Delivery from Bi-Layered Core-Shell Polymeric Microspheres

Chronic retinal diseases usually require repetitive local dosing. Depending on factors such as dosing frequency, mode of administration, and associated costs, this can result in poor patient compliance. A better alternative involves using controlled release drug delivery systems to reduce the frequency of intravitreal dosing and extend drug release. However, reaching the market stage is a time-consuming process. In this study, we employed two computational approaches to model and estimate the parameters governing the diffusion-controlled drug release of bovine serum albumin and bevacizumab (an agent that slows neovascularization due to retinal disorders) from bi-layered core-shell microspheres composed of chitosan and polycaprolactone (PCL). We used the estimated parameters to simulate the cumulative release under various conditions, optimize device design to guide future experimental efforts and improve the duration of release above a target daily therapeutic release rate from the microspheres. We investigated the effects of polymeric layer sizes on drug release. We provided straightforward computational tools for others to reuse in designing bi-layered microspheres suitable for addressing intravitreal drug delivery needs in the treatment of ocular neovascularization in chronic retinal diseases.

pharmacology and toxicology↗

bioRxiv2023

Macrophage innate immune gene expression requires dynamic regulation of the nuclear paraspeckle

To ensure a robust immune response to pathogens without risking immunopathology, the kinetics and amplitude of inflammatory gene expression in macrophages needs to be exquisitely well-controlled. There is a growing appreciation for stress-responsive membraneless organelles (MLOs) regulating various steps of eukaryotic gene expression in response to extrinsic cues. Here, we implicate the nuclear paraspeckle, a highly ordered biomolecular condensate that nucleates on the Neat1 lncRNA, in tuning innate immune gene expression in murine macrophages. In response to a variety of innate agonists, macrophage paraspeckles rapidly aggregate (0.5 h post-stimulation) and disaggregate (2h post-stimulation). Paraspeckle maintenance and aggregation require active transcription and MAPK signaling whereas paraspeckle disaggregation requires degradation of Neat1 via the nuclear RNA exosome. Expression of a large cohort of cytokines, chemokines, and antimicrobial mediators is compromised in lipopolysaccharide-treated macrophages lacking Neat1, resulting in a failure to express a cohort of pro-inflammatory cytokines, chemokines, and antimicrobial mediators. Consequently, Neat1 KO macrophages cannot control replication of Salmonella enterica serovar Typhimurium or vesicular stomatitis virus. These findings highlight a prominent role for MLOs in orchestrating the macrophage response to pathogens and support a model whereby dynamic assembly and disassembly of paraspeckles reprograms the nuclear RNA binding protein landscape to enable inflammatory gene expression following innate stimuli. SIGNIFICANCE STATEMENTTo mount appropriate immune responses and fight infection, macrophages need to sense and respond to pathogen-associated signals with incredible precision. Membraneless organelles (MLOs) are complexes of RNAs and proteins that change in size, shape, and abundance in response to extracellular signals. We hypothesized that an MLO called the nuclear paraspeckle helps macrophages initiate and calibrate innate immune gene expression during infection. We found that paraspeckles rapidly aggregate and then dissolve in macrophages following pathogen sensing. Macrophages lacking paraspeckles cannot properly induce inflammatory genes, resulting in a failure to control replication of intracellular bacterial and viral pathogens. These data suggest that altered paraspeckle dynamics may dysregulate inflammatory gene expression in a variety of human diseases.

immunology↗