FXa-Responsive Hydrogels to Craft Corneal Endothelial Lamellae.

Cell-instructive polymer hydrogels are instrumental in tissue engineering for regenerative therapies. Implementing defined and selective responsiveness to external stimuli is a persisting challenge that critically restricts their functionality. Addressing this challenge, this study introduces a versatile, modular hydrogel system composed of four-arm poly(ethylene glycol)(starPEG)-peptide and glycosaminoglycan(GAG)-maleimide conjugates.

A Tumor Microenvironment Model of Pancreatic Cancer to Elucidate Responses toward Immunotherapy.

Pancreatic cancer is a devastating malignancy with minimal treatment options. Standard-of-care therapy, including surgery and chemotherapy, is unsatisfactory, and therapies harnessing the immune system have been unsuccessful in clinical trials. Resistance to therapy and disease progression are mediated by the tumor microenvironment, which contains excessive amounts of extracellular matrix and stromal cells, acting as a barrier to drug delivery.

Customizing biohybrid cryogels to serve as ready-to-use delivery systems of signaling proteins.

Macroporous cryogels have recently gained increasing interest for the controlled administration of signaling proteins in tissue engineering due to an advantageous combination of material properties. However, most of the previously reported cryogel systems did not allow for tunable, sustained protein release. We therefore designed a set of ready-to-use multi-armed polyethylene glycol (starPEG)-heparin cryogel systems containing different amounts of the protein-affine glycosaminoglycan component heparin to enable systematically tunable long-term delivery of different signaling proteins without affecting other cell-instructive properties.

The significance of Gerta Vrbová's low-frequency stimulation experiment.

An inspiring scientific cooperation has come to an end, when Gerta Vrbová, an internationally renowned researcher in the field of neuromuscular interactions, passed away on October 2, 2020. Comparative EMG studies had led Gerta to suggest that different contractile properties of fast- and slow-twitch muscle fibers relate to specific firing patterns of their motoneurones. In support of her hypothesis, long term stimulation of fast-twitch muscles with a stimulus pattern resembling that of slow motoneurones, were shown to induce a pronounced fast-to-slow shift in contractile properties.

Poly(ethylene glycol) based nanotubes for tuneable drug delivery to glioblastoma multiforme.

Glioblastoma multiforme (GBM) is the most aggressive type of malignant brain tumour, which is associated with a poor two-year survival rate and a high rate of fatal recurrence near the original tumour. Focal/local drug delivery devices hold promise for improving therapeutic outcomes for GBM by increasing drug concentrations locally at the tumour site, or by facilitating the use of potent anti-cancer drugs that are poorly permeable across the blood brain barrier (BBB). For inoperable tumours, stereotactic delivery to the tumour necessitates the development of nanoscale/microscale injectable drug delivery devices.

Focal drug administration via heparin-containing cryogel microcarriers reduces cancer growth and metastasis.

Developing drug delivery systems that release anticancer drugs in a controlled and sustained manner remains challenging. We hypothesized that highly sulfated heparin-based microcarriers would allow electrostatic drug binding and controlled release. In silico modelling showed that the anticancer drug doxorubicin has affinity for the heparin component of the microcarriers.

Static and dynamic 3D culture of neural precursor cells on macroporous cryogel microcarriers.

Neural precursor cells have been much studied to further our understanding of the far-reaching and controversial question of adult neurogenesis. Currently, differentiation of primary neural precursor cells from the mouse dentate gyrus via 2-dimentional culture yields low numbers of neurons, a major hindrance to the field of study. 3-dimentional "neurosphere" culture allows better 3D cell-cell contact, but control over cell differentiation is poor because nutrition and oxygen restrictions at the core of the sphere causes spontaneous differentiation, predominantly to glial cells, not neurons.

Macroporous heparin-based microcarriers allow long-term 3D culture and differentiation of neural precursor cells.

Adult neurogenesis and the neurogenic niche in the dentate gyrus are subjects of much research interest. Enhancing our knowledge of this niche process and the role played by this unique microenvironment would further our understanding of plasticity and its relevance for cognition in health and disease. The complex three-dimensional (3D) nature of the niche microenvironment is poorly recapitulated in current cell culture experimental procedures.

Soft and flexible poly(ethylene glycol) nanotubes for local drug delivery.

Nanotubes are emerging as promising materials for healthcare applications but the selection of clinically relevant starting materials for their synthesis remains largely unexplored. Here we present, for the first time, the synthesis of poly(ethylene glycol) (PEG) based nanotubes via the photopolymerization of poly(ethylene glycol) diacrylate and other diacrylate derivatives within the pores of anodized aluminum oxide templates. Template-assisted synthesis allowed the manufacture of a diverse set of polymeric nanotubes with tunable physical characteristics including diameter (∼200-400 nm) and stiffness (405-902 kPa).

Thermospheric Nitric Oxide Response to Shock-led Storms.

We present a multi-year superposed epoch study of the Sounding of the Atmosphere using Broadband Emission Radiometry nitric oxide (NO) emission data. NO is a trace constituent in the thermosphere that acts as cooling agent via infrared (IR) emissions. The NO cooling competes with storm time thermospheric heating resulting in a thermostat effect.

The Contribution of Neuromuscular Stimulation in Elucidating Muscle Plasticity Revisited.

Studies carried out during the past 45 years on the effects of chronic low-frequency stimulation on skeletal muscle have revealed a multiplicity of adaptive changes of muscle fibres in response to increased activity. As reflected by induced changes in the metabolic properties, protein profiles of the contractile machinery and elements of the Ca-regulatory system, all essential components of the muscle fibre undergo pronounced changes in their properties that ultimately lead to their reversible transformation from fast-to-slow phenotype. The chronic low-frequency stimulation experiment thus allows exploring many aspects of the plasticity of mammalian skeletal muscle.

Thermo-responsive cell culture carriers based on poly(vinyl methyl ether)-the effect of biomolecular ligands to balance cell adhesion and stimulated detachment.

Two established material systems for thermally stimulated detachment of adherent cells were combined in a cross-linked polymer blend to merge favorable properties. Through this approach poly(-isopropylacrylamide) (PNiPAAm) with its superior switching characteristic was paired with a poly(vinyl methyl ether)-based composition that allows adjusting physico-chemical and biomolecular properties in a wide range. Beyond pure PNiPAAm, the proposed thermo-responsive coating provides thickness, stiffness and swelling behavior, as well as an apposite density of reactive sites for biomolecular functionalization, as effective tuning parameters to meet specific requirements of a particular cell type regarding initial adhesion and ease of detachment.

Alpha-catalytic subunits of 5'AMP-activated protein kinase display fiber-specific expression and are upregulated by chronic low-frequency stimulation in rat muscle.

5'-AMP-activated protein kinase (AMPK) signaling initiates adaptive changes in skeletal muscle fibers that restore homeostatic energy balance. The purpose of this investigation was to examine, in rats, the fiber-type protein expression patterns of the alpha-catalytic subunit isoforms in various skeletal muscles, and changes in their respective contents within the tibialis anterior (TA) after chronic low-frequency electrical stimulation (CLFS; 10 Hz, 10 h daily), applied for 4 +/- 1.2 or 25 +/- 4.

Effect of satellite cell ablation on low-frequency-stimulated fast-to-slow fibre-type transitions in rat skeletal muscle.

The purpose of this study was to determine whether satellite cell ablation within rat fast-twitch muscles exposed to chronic low-frequency stimulation (CLFS) would limit fast-to-slow fibre-type transitions. Twenty-nine male Wistar rats were randomly assigned to one of three groups. Satellite cells of the left tibialis anterior were ablated by weekly exposure to a 25 Gy dose of gamma-irradiation during 21 days of CLFS (IRR-Stim), whilst a second group received only 21 days of CLFS (Stim).

Chronic low-frequency stimulation upregulates uncoupling protein-3 in transforming rat fast-twitch skeletal muscle.

The purpose of this investigation was to examine the temporal changes in uncoupling protein (UCP)-3 expression, as well as related adaptive changes in mitochondrial density and fast-to-slow fiber type transitions during chronically enhanced contractile activity. We examined the effects of 1-42 days of chronic low-frequency electrical stimulation (CLFS), applied to rat tibialis anterior (TA) for 10 h/day, on the expression of UCP-3 and concomitant changes in myosin heavy chain (MHC) protein expression and increases in oxidative capacity. UCP-3 protein content increased from 1 to 12 days, reaching 1.

Contractile properties, fiber types, and myosin isoforms in fast and slow muscles of hyperactive Japanese waltzing mice.

This study focuses on the effects of neuromuscular hyperactivity on the contractile properties, fiber type composition, and myosin heavy chain (MHC) isoform expression of fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles in Japanese waltzing mice (JWM) of the C57BL/6J-v2J strain. The same properties were studied in the homologous muscle of control CBA/J mice (CM). In comparison to CM, the JWM exhibited (i) longer activity periods, prolonged bouts of running and a higher food intake, (ii) slower twitch and tetanic contractions of both EDL and SOL muscles, decreased cold and post-tetanic potentiation of the EDL, as well as increased cold and post-tetanic depressions of the SOL.

Beneficial effects of chronic low-frequency stimulation of thigh muscles in patients with advanced chronic heart failure.

Aims: Patients with chronic heart failure (CHF) exhibit detrimental changes in skeletal muscle that contribute to their impaired physical performance. This study investigates the possibility of counteracting these changes by chronic low-frequency electrical stimulation (CLFS) of left and right thigh muscles.

Methods And Results: (mean+/-SD) 32 CHF patients (53+/-10 years) with an LVEF of 22+/-5%, NYHA II-IV, undergoing optimized drug therapy, were randomized in a CLFS group (CLFSG) or a control group (controls).

AMPK activation increases uncoupling protein-3 expression and mitochondrial enzyme activities in rat muscle without fibre type transitions.

The present study examined the effect of chronic activation of 5'-AMP-activated protein kinase (AMPK) on the metabolic profile, including uncoupling protein-3 (UCP-3) and myosin heavy chain (MHC)-based fibre phenotype of rodent fast-twitch tibialis anterior muscle. Sprague-Dawley rats were given daily injections of 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), a known activator of AMPK, or vehicle (control) for 28 days. After AICAR treatment, UCP-3 expression at the mRNA level was elevated 1.

Functional and biochemical properties of chronically stimulated human skeletal muscle.

The present study was undertaken to investigate in a randomized controlled trial the effects of chronic (10 weeks, 4 h per day, 7 days per week) low-frequency (15 Hz) stimulation (CLFS) of the knee extensor and hamstring muscles of both legs in healthy volunteers via surface electrodes. A control group (n=10) underwent the same treatment (sham stimulation) as the CLFS-treated group (n=10), except that stimulation intensity was kept at a level which did not evoke contractions. Biopsy samples were taken before the onset and after cessation of stimulation from the right vastus lateralis muscle of all subjects.

Increased expression of the nicotinic acetylcholine receptor in stimulated muscle.

Chronic low-frequency stimulation has been used as a model for investigating responses of skeletal muscle fibres to enhanced neuromuscular activity under conditions of maximum activation. Fast-to-slow isoform shifting of markers of the sarcoplasmic reticulum and the contractile apparatus demonstrated successful fibre transitions prior to studying the effect of chronic electro-stimulation on the expression of the nicotinic acetylcholine receptor. Comparative immunoblotting revealed that the alpha- and delta-subunits of the receptor were increased in 10-78 day stimulated specimens, while an associated component of the surface utrophin-glycoprotein complex, beta-dystroglycan, was not drastically changed in stimulated fast skeletal muscle.

Partial fast-to-slow conversion of regenerating rat fast-twitch muscle by chronic low-frequency stimulation.

Chronic low-frequency stimulation (CLFS) of rat fast-twitch muscles induces sequential transitions in myosin heavy chain (MHC) expression from MHCIIb --> MHCIId/x --> MHCIIa. However, the 'final' step of the fast-to-slow transition, i.e.

Kinetic properties of cardiac myosin heavy chain isoforms in rat.

The head portion of the myosin heavy chain (MHC) is essential in force generation. As previously shown, Ca2+-activated fibres of mammalian skeletal muscle display a strong correlation between their MHC isoform complement and the kinetics of stretch activation, suggesting isoform-specific differences in kinetic properties of myosin heads. Using the same methodology on muscle strips of atria and ventricles of hyper- and hypothyroid rats, this study showed that the kinetics of cardiac alphaMHC are 3 times faster than those of cardiac betaMHC under isometric conditions and maximal Ca2+ activation.

The adaptive potential of skeletal muscle fibers.

Mammalian skeletal muscle fibers display a great adaptive potential. This potential results from the ability of muscle fibers to adjust their molecular, functional, and metabolic properties in response to altered functional demands, such as changes in neuromuscular activity or mechanical loading. Adaptive changes in the expression of myofibrillar and other protein isoforms result in fiber type transitions.