Guiding cell adhesion and motility by modulating cross-linking and topographic properties of microgel arrays

ITIH5 as a multifaceted player in pancreatic cancer suppression, impairing tyrosine kinase signaling, cell adhesion and migration

Inter-alpha-trypsin inhibitor heavy chain 5 (ITIH5) has been identified as a metastasis suppressor gene in pancreatic cancer. Here, we analyzed ITIH5 promoter methylation and protein expression in The Cancer Genome Atlas (TCGA) dataset and three tissue microarray cohorts (n = 618), respectively. Cellular effects, including cell migration, focal adhesion formation and protein tyrosine kinase activity, induced by forced ITIH5 expression in pancreatic cancer cell lines were studied in stable transfectants. ITIH5 promoter hypermethylation was associated with unfavorable prognosis, while immunohistochemistry demonstrated loss of ITIH5 in the metastatic setting and worsened overall survival. Gain-of-function models showed a significant reduction in migration capacity, but no alteration in proliferation. Focal adhesions in cells re-expressing ITIH5 exhibited a smaller and more rounded phenotype, typical for slow-moving cells. An impressive increase of acetylated alpha-tubulin was observed in ITIH5-positive cells, indicating more stable microtubules. In addition, we found significantly decreased activities of kinases related to focal adhesion. Our results indicate that loss of ITIH5 in pancreatic cancer profoundly affects its molecular profile: ITIH5 potentially interferes with a variety of oncogenic signaling pathways, including the PI3K/AKT pathway. This may lead to altered cell migration and focal adhesion formation. These cellular alterations may contribute to the metastasis-inhibiting properties of ITIH5 in pancreatic cancer.

Mimicking the neural stem cell niche: An engineer’s view of cell: material interactions

Neural stem cells have attracted attention in recent years to treat neurodegeneration. There are two neurogenic regions in the brain where neural stem cells reside, one of which is called the subventricular zone (SVZ). The SVZ niche is a complicated microenvironment providing cues to regulate self-renewal and differentiation while maintaining the neural stem cell’s pool. Many scientists have spent years understanding the cellular and structural characteristics of the SVZ niche, both in homeostasis and pathological conditions. On the other hand, engineers focus primarily on designing platforms using the knowledge they acquire to understand the effect of individual factors on neural stem cell fate decisions. This review provides a general overview of what we know about the components of the SVZ niche, including the residing cells, extracellular matrix (ECM), growth factors, their interactions, and SVZ niche changes during aging and neurodegenerative diseases. Furthermore, an overview will be given on the biomaterials used to mimic neurogenic niche microenvironments and the design considerations applied to add bioactivity while meeting the structural requirements. Finally, it will discuss the potential gaps in mimicking the microenvironment.

Structure-Related Mechanical Properties and Bioactivity of Silica-Gelatin Hybrid Aerogels for Bone Regeneration

We report the synthesis of mesoporous silica-gelatin hybrid aerogels with 15, 25, and 30 wt. % gelatin contents, using 3-glycidoxypropyl trimethoxysilane (GPTMS) as a coupling agent, for tissue-engineering applications. Aerogels were obtained using a one-step sol-gel process followed by CO₂ supercritical drying, resulting in crack-free monolith samples with bulk densities ranging from 0.41 g cm^-3 to 0.66 g cm^-3. Nitrogen adsorption measurements revealed an interconnected mesopore network and a general decrease in the textural parameters: specific surface areas (651-361 m² g^-1), pore volume (1.98-0.89 cm³ g^-1), and pore sizes (10.8-8.6 nm), by increasing gelatin content. Thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy and uniaxial compression experiments confirmed that the structure, thermal properties and mechanical behavior of these aerogels changed significantly when the concentration of gelatin reached 25 wt.%, suggesting that this composition corresponds to the percolation threshold of the organic phase. In addition, the samples exhibited hydrophilic behavior and extremely fast swelling in phosphate-buffered saline (PBS), with swelling ratios from 2.32 to 3.32. Furthermore, in vitro bioactivity studies revealed a strong relationship between the kinetics of the nucleation and growth processes of hydroxyapatite in simulated body fluid (SBF) and the gelatin content. The live/dead assay revealed no cytotoxicity in HOB^® osteoblasts in vitro and a positive influence on cell growth, focal adhesion development, and cytoskeletal arrangement for cell adhesion. Mineralization assays confirmed the positive effects of the samples on osteoblast differentiation. The biomaterials described are versatile, can be easily sterilized and are suitable for a wide range of applications in bone tissue-engineering, either alone or in combination with bioactive-reinforced phases.

4D Printing of Extrudable and Degradable Poly(Ethylene Glycol) Microgel Scaffolds for Multidimensional Cell Culture

Granular synthetic hydrogels are useful bioinks for their compatibility with a variety of chemistries, affording printable, stimuli-responsive scaffolds with programmable structure and function. Additive manufacturing of microscale hydrogels, or microgels, allows for the fabrication of large cellularized constructs with percolating interstitial space, providing a platform for tissue engineering at length scales that are inaccessible by bulk encapsulation where transport of media and other biological factors are limited by scaffold density. Herein, synthetic microgels with varying degrees of degradability are prepared with diameters on the order of hundreds of microns by submerged electrospray and UV photopolymerization. Porous microgel scaffolds are assembled by particle jamming and extrusion printing, and semi-orthogonal chemical cues are utilized to tune the void fraction in printed scaffolds in a logic-gated manner. Scaffolds with different void fractions are easily cellularized post printing and microgels can be directly annealed into cell-laden structures. Finally, high-throughput direct encapsulation of cells within printable microgels is demonstrated, enabling large-scale 3D culture in a macroporous biomaterial. This approach provides unprecedented spatiotemporal control over the properties of printed microporous annealed particle scaffolds for 2.5D and 3D tissue culture.