Biotechnology and Bioengineering最新文献

Adeno-associated virus (AAV) is a promising delivery system for gene therapy. However, current manufacturing of AAV suffers from very low yields compared to other biotherapeutics. The AAV dose per patient ranges between 10¹¹and 10¹⁵ viral genomes (vg), requiring an average of 10 to 30 L production/dose. As a consequence, production costs are prohibitive for most indications. Our recent studies revealed that only 10% of the HEK293 cells that have received the AAV encoding DNA produce assembled AAV capsids. This observation prompts the question: Why would cells that have been successfully transfected, be unable to produce AAV. To answer this question, we undertook a detailed study to characterize the two sub-populations from the same transfection, the cells that were making assembled capsids and those that were not. We found that the two populations had distinct cell cycle profiles, with a block in cell cycle progression characterizing the producer population. RNA-seq analysis of the two populations reveals differences in the molecular pathways impacted and provides a basis for making changes to improve productivity.

Epithelial tissues actively deform their surrounding extracellular matrix mechanically. Traction forces represent an intrinsic mechanism by which cells actively sense and adapt to their extracellular environment, which has been increasingly recognized to play a crucial role in cancer progression, metastasis, and treatment failure. However, current traction force research has predominantly concentrated at the single-cell level, overlooking the multicellular spatio-temporal dynamics and collective effects inherent in cancer as an integrated multi-cellular system. Herein, the collective-level traction forces of cancer spheroids were mapped using traction force microscopy. Our results revealed an inherent spatial distribution pattern of cancer spheroid traction force at the spheroid–substrate contact plane, with peaks concentrated along the periphery of the contact interface. Besides, the cancer spheroid traction force was regulated by the spheroid size when the spheroid did not undergo dispersion, which was positively correlated with the spheroid dispersion ability. Moreover, there existed an inherent temporal correlation between the spheroid traction force and dispersion. The onset of cancer spheroid dispersion was accompanied with a marked suppression of the traction force dynamics. Furthermore, the traction force of cancer spheroids was validated to hold potential as a biomechanics-related phenotypic readout for anticancer drug testing.

Clostridioides difficile infection presents an escalating clinical challenge due to the proliferation of hypervirulent and antibiotic-resistant strains. The primary symptoms of disease, namely colitis and diarrhea, are induced by the release of two toxins: TcdA and TcdB. Targeting these toxins with peptide inhibitors provides an attractive therapeutic strategy that can be used alone or synergistically with standard antibiotic treatments to alleviate severe symptoms and reduce the risk of resistance development. In this study, we present the rational discovery and optimization of potent TcdB peptide inhibitors. The lead sequences effectively inhibit TcdB glucosyltransferase activity, the crucial enzymatic process leading to disease symptoms, by directly competing with the toxin's molecular targets, Rho proteins. Detailed enzymatic studies also elucidate distinct Michaelis constants, K_M, for each substrate, UDP-glucose and Rho-proteins, for multiple TcdB GTD subtypes. The selected peptides demonstrated broad efficacy against the three most common TcdB subtypes, which are used in over 90% of clinical isolates. Additionally, the peptides delayed TcdB-induced loss of barrier integrity and decreased apoptosis in a primary human colon epithelial monolayer model. This study highlights a novel therapeutic avenue with significant potential to enhance the treatment and management of C. difficile infections.

Opportunistic colonization and recurring infection by Pseudomonas aeruginosa are substantial risks to lung functionality for people with underlying respiratory diseases such as cystic fibrosis and chronic obstructive pulmonary disease. The complex metabolic and phenotypic adaptations P. aeruginosa exhibits in response to its environmental conditions make relevant in vitro models of pathogenic populations crucial for identifying and evaluating effective antimicrobial targets. However, an extracellular component that is rarely integrated into these experimental platforms is a spatially extensive, semisolid gel medium representative of biological respiratory mucus layers that P. aeruginosa propagates through via active motility. In this investigation, we examine the applicability of swim plate assays, a qualitative methodology for measuring flagellar swimming motility, as an in vitro platform to study the spatiotemporal development of P. aeruginosa strain PA14. The propagation behavior of PA14 was tracked through time-lapse microscopy and studied under different agar gel compositions incorporating methylcellulose as well as native MUC5AC mucin. To aid quantitative characterization of PA14 population expansion, we paired this experimental workflow with a continuum model that would fit density profile fluctuations to changes in PA14 swimming motility and growth kinetics. We observed higher extracellular concentration and production of the phenazine pyocyanin when PA14 populations were grown in swim plate assays, supporting the emergence of heterogeneous growth environments within the microbial population. PA14 swim plates exhibited a significantly lower spreading velocity in gels containing 0.30% w/v MUC5AC, which model-to-experiment fitting results determined to be driven by reductions in PA14 swimming motility. Continuum model parameters additionally portrayed PA14 expansion in mucin gels, having cell growth outcompeting cell motility, which aligned with experimental assay observations of macrocolonies rapidly developing to high biomass density states. In contrast, PA14 did not show spreading velocity differences in gels containing 0.30% methylcellulose, and fitted parameters did not identify major growth and motility differences when compared to agar-only gels. Combined with the resource accessibility of this experimental platform, the swim plate assay as an in vitro model is well suited to investigations of pathogenic community dynamics in gel conditions over more extensive spatial and time scales.

Microglia are critical regulators of brain homeostasis and immune responses in the central nervous system (CNS). However, existing human-based models fail to reproduce the early and complex microglia-neural cell interactions. The differentiation of human induced pluripotent stem cells (hiPSCs) into specialized cell types offers promising avenues for understanding human development and disease modeling. Herein, a methodology for the differentiation of hiPSC-derived erythromyeloid progenitors (iEMPs) and their 3D co-culture with hiPSC-derived neurospheres were explored, utilizing the Ambr 250 Modular stirred-tank bioreactor (STB) system. The aim of this study was to build a complex co-culture model between iEMP and neurospheres in a scalable and controlled environment. Our results demonstrate that the STB effectively supports the co-culture process, with iEMP integration into the neurospheres, exhibiting cell density, aggregate morphology, and concentration similar to the neurosphere cultures. The co-culture environment induced the upregulation of transcription factors critical for microglial lineage commitment. iEMP-neurospheres displayed a unique secretory profile, releasing proteins involved in extracellular matrix remodeling and neuronal differentiation, essential for microenvironment remodeling. In conclusion, this study underscores the role of iEMPs in CNS development and presents a robust platform for preclinical research.

Hydrogels are commonly used to immobilize mammalian cells, offering mechanical support in 3D cultures and acting as barriers for immunoprotection in transplantation, such as islet encapsulation for diabetes therapy. Cell immobilization restricts bulk fluid motion, resulting in diffusion-limited molecular transport and nutrient concentration gradients, particularly for oxygen consumed by immobilized cells. Oxygen mass transport models are essential for designing immobilization strategies but often rely on assumed diffusion coefficients due to a lack of experimental data. We propose a cost-effective, accessible system for experimentally measuring oxygen diffusion coefficients in cell-laden hydrogels, tested on alginate-immobilized pancreatic beta cells (MIN6). Compared to water, oxygen diffusivity was significantly lower in alginate gels and inversely correlated with the dynamic loss modulus. Diffusivity also decreased with increasing alginate concentration from 2% to 5%. Cell viability depended heavily on gel concentration and cell density, as predicted by Thiele modulus and effectiveness factor values calculated from the measured diffusion coefficients. This platform, combining a simple experimental setup with dimensionless numbers, offers a practical way to predict maximal diffusion distances in cell immobilization strategies. The proposed approach can support rational design of cell encapsulation, immobilized cell culture, and tissue engineering strategies.