SHELL Part of Nucleus Accumbens and Its Laterality Has Important Role in Response to Chronic Stress in Female Rats

Abstract The nucleus accumbens shell (NAcSh) plays a role in appetitive and negative motivation with sex differences in responses. NAcSh and its laterality in metabolic and hormonal responses to chronic stress in female rats is evaluated via transient inactivation of this nucleus during stress induction. Animals in the stress groups received consecutive stress for four days and transient inactivation of NAcSh was performed by administrating lidocaine (0.2%) unilaterally or bilaterally in the nucleus for five minutes before electric foot shock induction. After stress termination, food and water intake, latency to eat, plasma glucose, corticosterone, estradiol and progesterone were measured in all groups. Results showed that stress increased food intake and blood glucose level, but there were no change in the latency to eat and the amount of water intake. The right side, the left side, and both sides of NAcSh may be dominant in latency to eat, food intake, and both water intake and plasma glucose level, respectively. Although chronic stress included no changes for corticosterone and progesterone, it increased estradiol level in plasma. Also, bilateral and right sides of NAcSh may have modulatory effects on stress in corticosterone and progesterone, respectively, without affecting estradiol. It can be concluded that the NAc shell plays a pivotal role in metabolic and hormonal responses to chronic stress in a laterality manner in female rats.

Differentiation of stem cells from the apical papilla into osteoblasts by the elastic modulus of porous silk fibroin scaffolds.

In addition to traditional approach for differentiation (biochemical factors), physical properties (elastic modulus) of the matrix will be becoming an important factor in differentiation of stem cells into different lineages. The porous scaffolds were prepared from the silk fibroin solutions 4%, 5%, 6%, 7% and 8.4% weight per volume (w/v) by freeze drying which produced scaffolds with the minimal changes in the pore size (96-160 µm) but with a ≈ 8-fold range of modulus (16 -131 kPa) in the wet condition. After isolation and characterization, stem cells of the apical papilla (SCAP) were seeded on the scaffolds and the osteogenic differentiation was evaluated by alizerin red staining, alkaline phosphatase test, real time PCR and immunohistochemistry. Results demonstrated modulus-dependent osteogenic differentiation of the apical papilla stem cells from 4% w/v (16 kPa) to 7% w/v (83 kPa) and then a sudden decrease of differentiation was observed in the 8.4% w/v (131 kPa). The highest differentiation was happened in the 7 % w/v (83 kPa). The stem cells can respond to elasticity ranged from 0.1 to 100 kPa and then differentiate into different lineages in terms of the amount of elastic modulus. This is probably the reason why bone differentiation potential of the SCAP decreases in the modulus over 100 kPa.

Evaluation of Novel Mouse-Specific Germ Cell Gene Expression in Embryonic Stem Cell-Derived Germ Cell-Like Cells In Vitro with Retinoic Acid Treatment.

We designed a study to induce differentiation of Oct4-GFP (expression of Green Fluorescent Protein of oct4) embryonic stem cells (ESCs) by embryoid body (EB) culture system into germ cells (GCs) using retinoic acid (RA) and evaluated the expression level of (Fkbp6, Mov10l1, 4930432K21Rik, and Tex13) in differentiated cells. The expression levels of four GC-related genes, Oct4, Mvh, Scp3, and Stra8, was determined by quantitative real-time polymerase chain reaction (q-RT-PCR). Immunostaining and flow cytometry were used as additional tests to confirm q-RT-PCR findings. A significant increase occurred in the expression of meiotic markers and specific genes, Fkbp6 (p = 0.00), Mov10l1 (p = 0.01), and Tex13 (p = 0.00) in ESCs treated with RA (+RA) compared with the controls (-RA). Oct4 expression was decreased in all studied groups. The expression levels of 4930432K21Rik, Mvh, Stra8, and Scp3 in the +RA group was higher than that of the -RA group. Flow cytometry analysis showed that mean number of Mvh-positive cells in the +RA group was greater as compared with ESCs, -RA and EB7 groups (p = 0.00). Downregulation of Oct4 as a pluripotency factor as well as the expression of meiosis markers, this hypothesis is raised that ESCs are differentiated by RA, and have been introduced into the zygote/pachytene of first meiosis as GC-like cells.

Auto-fluorescence of a silk fibroin-based scaffold and its interference with fluorophores in labeled cells.

Silk fibroin is increasingly emerging as an important biomaterial for tissue engineering applications. The ability to fluorescently image silk matrices under a microscope would be helpful in differentiating embedded labeled cells from background signal, critical for the study of silk-based engineered tissues. In this study, we fabricated a scaffold using freeze drying and confirmed its structure by X-ray diffraction and Fourier transform infrared spectroscopy. We then examined the fluorescence of the silk fibroin scaffold using confocal microscopy, both before and after cell seeding and fluorescent labeling. We subsequently investigated the fluorescent signature of the silk fibroin scaffold chemically. Fluorophore-labeled cells seeded into the scaffold showed the same fluorescent color as the scaffold itself when excited by the same wavelength of light. UV-Vis and fluorescence spectroscopy of a silk fibroin solution indicated absorption and emission maxima at 277 and 345 nm, respectively, which is a typical protein-derived signal. HPLC and GC-MS were used to detect quercetin and quercetin derivatives, without success. We therefore conclude that unlike silk cocoons, the fluorescent behavior of silk fibroin scaffolds does not derive from quercetin and its derivatives but from the intrinsic fluorescence of fibroin protein. We also find that the fluorescent signals deriving from a scaffold and from labeled cells embedded in it can be distinguished when the different optical channels are merged.

Impact of pre-incubation time of silk fibroin scaffolds in culture medium on cell proliferation and attachment.

Cell behaviours such as proliferation and attachment can be affected by the length of pre-incubation period of the scaffolds in the culture medium for long term. The aim of this study was to investigate the long term pre-incubation of 3D silk fibroin scaffolds in complete culture medium on cell attachment and proliferation. After the preparation of silk fibroin scaffolds by the technique of freeze drying, the scaffolds were pre-incubated in complete culture medium for 2 d, 6 d or 10 d before apical papilla stem cells (SCAP) seeding. Modifications of the scaffold surface and wettability were examined by FE-SEM and water contact angle, respectively. Results showed a decrease both in roughness and water contact angle as pre-incubation time increases. DNA measurement after 18h and 10 d cell seeding showed a significant increase of DNA concentration which represents better attachment and proliferation with pre-incubation time increase. Qualitative examination, live&dead assay or H&E staining method after 30h and 10 d cell seeding respectively, indicated that pre-incubation of scaffolds has time dependent effect on cell proliferation and attachment. This suggests that improvement of cell attachment and proliferation may be mediated by differences in the amount of wettability (decreased water contact angle) after exposure of scaffold to culture medium for long term which, in turn, causes more protein adsorption in the surface of silk fibroin scaffold (decreased roughness).