Extent Of Network Formation Research Articles

Network formation through active migration of human vascular endothelial cells in a multilayered skeletal myoblast sheet

Autologous transplantation of myoblast sheet has attracted attention as a new technique for curing myocardial infarction. Myoblast sheet has the ability to secret cytokines that improve heart function via the facilitation of angiogenesis on affected part. To mimic the in vivo angiogenesis in the myoblast sheet after transplantation, a five-layered cell sheet of human skeletal muscle myoblasts (HSMMs) was overlaid on human umbilical vein endothelial cells (HUVECs) which enables evaluation of dynamic HUVEC behavior. HUVECs existing initially at the bottom of the sheet changed to be a stretched shape and migrated upward compared with the surrounding HSMMs in the sheet. Prolonged incubation resulted in network formation of HUVECs in the middle of the sheet, although non-networked HUVECs continued to migrate to the top of the sheet, which meant the spatial habitation of HUVECs in the cell sheet. Image processing was performed to determine the variation in the extent of network formation at different HUVEC densities. It was found that the extent of formed network depended on the frequency of encounters among HUVECs in the middle of the sheet. The present system, which can evaluate network formation, is considered to be a promising in vitro angiogenesis model.

The early mouse 3D osteocyte network in the presence and absence of mechanical loading

Osteocytes are considered to act as mechanosensory cells in bone. They form a functional synctia in which their processes become interconnected to constitute a three-dimensional (3D) network. Previous studies reported that in mice, the two-dimensional osteocyte network becomes progressively more regular as they grow, although the key factors governing the arrangement of the osteocyte network during bone growth remain unknown. In this study, we characterized the 3D formation of the osteocyte network during bone growth.Morphological skeletal changes have been reported to occur in response to mechanical loading and unloading. In order to evaluate the effect of mechanical unloading on osteocyte network formation, we subjected newborn mice to sciatic neurectomy in order to immobilize their left hind limb as an unloading model. The osteocyte network was visualized by staining osteocyte cell bodies and processes with fluorescently labeled phalloidin. First, we compared the osteocyte network in the femora of embryonic and 6-week-old mice in order to understand the morphological changes that occur with normal growth and mechanical loading. In embryonic mice, the osteocyte network in the femur cortical bone displayed a random cell body distribution, non-directional orientation of cell processes, and irregularly shaped cells. In 6-week-old mice, the 3D network contained spindle-shaped osteocytes, which were arranged parallel to the longitudinal axis of the femur. In addition, more and longer cell processes radiated from each osteocyte. Second, we compared the cortical osteocyte networks of 6-week-old mice that had or had not undergone sciatic neurectomy in order to evaluate the effect of unloading on osteocyte network formation. The osteocyte network formation in both cortical bone and cancellous bone was affected by mechanical loading. However, there were differences in the extent of network formation between cortical bone and cancellous bone in response to mechanical loading with regard to the orientation, nuclear shape and branch formation.

Mesoscale Simulation of the Effect of a Lactide Segment on the Nanostructure of Star Poly(ethylene glycol-co-lactide)-Acrylate Macromonomers in Aqueous Solution

The distribution of reactive groups and micelle formation in amphiphilic macromonomers and the extent of network formation in aqueous solution depend on the segment length of the hydrophobic monomer. The objective of this work was to simulate by dissipative particle dynamics (DPD) the structure of the four-arm star poly(ethylene glycol-co-lactide)-acrylate (SPELA) macromonomer in aqueous solution. The effect of lactide segment length (n) in each arm and macromonomer concentration on the distribution and size of the micelles was investigated. In the absence of lactide, the reactive acrylate groups were uniformly distributed in the aqueous solution. With the addition of lactide segments, micelles formed with a hydrophobic core containing lactide and acrylate beads and a hydrophilic corona of ethylene oxide beads. The size and average number of macromonomers (aggregation number) of the micelles increased with n while the number density of micelles decreased. Furthermore, the fraction of macromonomer arms incorporated in the micelles as either loops or intermicellar bridges increased with increasing n. The macromonomer bridge fraction showed a biphasic behavior with a maximum at n = 4. The accumulation of water beads around acrylates decreased with increasing n. The aggregation of acrylates initially increased with n, and then, it decreased for n > 4 due to the decrease in size and distance between the micelles. The fraction of acrylates in the core surface layer of the micelles decreased from 66 to 19% when n increased from 4 to 16 with a higher fraction of acrylates trapped in the micelles' core. Macromonomer concentration increased the number density of micelles, but it did not have a significant effect on the micelle size or distribution of the acrylates. The simulation results indicate that SPELA macromers with <4 lactide segment length can potentially produce degradable PEG-based hydrogels with the highest network density.

Synthesis and properties of urea porphyrinosilica

The synthesis of a hybrid network consisting of alternating porphyrin as optical active agent and siloxane units (porphyrinosilica) can be achieved by sol–gel process. Due to several applications of these hybrids, we search for new methods to prepare them. A porphyrinosilica with a urea linker was synthesized through the reaction of NH 2 groups present in the phenyl rings of mesotetrakis p-aminophenyl porphyrin (TAMPPH 2) with 3-isocyanatopropyltriethoxysilane (IPTES) followed by condensation with tetraethoxysilane (TEOS). The polymerization reactions were carried out in ethanol or dimethylformamide using acidic or basic catalysis. The formation of urea bonds was confirmed by infrared spectroscopy. The absorption and luminescence spectra confirmed the presence of porphyrin in the network and were also established by thermal analysis. Nuclear magnetic resonance 29Si data for the porphyrinosilica addressed the degree of condensation and the extent of network formation.

MECHANICAL AND WATER‐HOLDING PROPERTIES OF HEAT‐INDUCED SOY PROTEIN GELS AS RELATED TO THEIR STRUCTURAL ASPECTS

AbstractThe dependence of mechanical and water‐holding properties of soy protein gels upon their structures was examined. Gels varying in extent of network formation were prepared by heating 20% paste of the isolated soy protein (ISP) containing L‐cysteine hydrochloride (CySH) which has an ability to cleave intermolecular disulfide bonds. A rapid decrease in gel hardness and cohesiveness was observed with the increase in added amount of CySH up to 2.5 times 10‐5 mole/g ISP, and then a gradual decrease to 5.0 times 10‐5 mole/g ISP. The changes in these mechanical parameters appeared to depend on the degree of the network formation interpreted from the solubility changes of gels in the phosphate buffer containing 6 M urea. The relaxation time, estimated by compression stress relaxation, was also dependent on the degree of the network formation, while the modulus of elasticity was hardly affected. On the other hand, there was an inverse correlation between the NMR line width of the water proton and expressible water by the pressure method as an index of water‐holding properties of the gel; the broader the former, the lesser the latter. The change in the water‐holding capacity estimated from expressible water was also associated with that in the degree of the network formation. This confirms that both mechanical and water‐holding properties of the gel are qualitatively governed by the extent of the structure formation controlled by the intermolecular disulfide bonds.