Bioceramic-collagen scaffolds loaded with human adipose-tissue derived stem cells for bone tissue engineering

The combination of bioceramics and stem cells has attracted the interest of research community for bone tissue engineering applications. In the present study, a combination of Bio-Oss^® and type 1 collagen gel as scaffold were loaded with human adipose-tissue derived mesenchymal stem cells (AT-MSCs) after isolation and characterization, and the capacity of them for bone regeneration was investigated in rat critical size defects using digital mammography, multi-slice spiral computed tomography imaging and histological analysis. 8 weeks after implantation, no mortality or sign of inflammation was observed in the site of defect. According to the results of imaging analysis, a higher level of bone regeneration was observed in the rats receiving Bio-Oss^®-Gel compared to untreated group. In addition, MSC-seeded Bio-Oss-Gel induced the highest bone reconstruction among all groups. Histological staining confirmed these findings and impressive osseointegration was observed in MSC-seeded Bio-Oss-Gel compared with Bio-Oss-Gel. On the whole, it was demonstrated that combination of AT-MSCs, Bio-Oss and Gel synergistically enhanced bone regeneration and reconstruction and also could serve as an appropriate structure to bone regenerative medicine and tissue engineering application.     

Sly-miR166 and Sly-miR319 are components of the cold stress response in Solanum lycopersicum

MicroRNAs (miRNAs) are a class of small endogenous non-coding RNAs that modulate gene expression in both plants and animals and are involved in several biological processes, ranging from organ differentiation to biotic and abiotic stress responses. We identified two cold stress response microRNAs that showed differential expression in Solanum lycopersicum plants subjected to cold stress. We observed that Sly-miR166 and Sly-miR319 were up-regulated by cold treatments. The up-regulation of Sly-miR166 and Sly-miR319 in cold stress-treated S. lycopersicum seedlings and the down-regulation of their respective targets, HD-Zip III and GAMyb-like that validate by 5′-RACE technique, suggests that these miRNAs play a critical role in regulating S. lycopersicum responses to cold stress.     

MC-Net: a method for the construction of phylogenetic networks based on the Monte-Carlo method

Background  

A phylogenetic network is a generalization of phylogenetic trees that allows the representation of conflicting signals or alternative evolutionary histories in a single diagram. There are several methods for constructing these networks. Some of these methods are based on distances among taxa. In practice, the methods which are based on distance perform faster in comparison with other methods. The Neighbor-Net (N-Net) is a distance-based method. The N-Net produces a circular ordering from a distance matrix, then constructs a collection of weighted splits using circular ordering. The SplitsTree which is a program using these weighted splits makes a phylogenetic network. In general, finding an optimal circular ordering is an NP-hard problem. The N-Net is a heuristic algorithm to find the optimal circular ordering which is based on neighbor-joining algorithm.     

Long-term cyclical in vivo loading increases cartilage proteoglycan content in a spatially specific manner: an infrared microspectroscopic imaging and polarized light microscopy study

Understanding the changes in collagen and proteoglycan content of cartilage due to physical forces is necessary for progress in treating joint disorders, including those due to overuse. Physical forces in the chondrocyte environment can affect the cellular processes involved in the biosynthesis of extracellular matrix. In turn, the biomechanical properties of cartilage depend on its collagen and proteoglycan content. To understand changes due to physical forces, this study examined the effect of 80 cumulative hours of in vivo cyclical joint loading on the cartilage content of proteoglycan and collagen in the rabbit metacarpophalangeal joint. The forepaw digits of six anesthetized New Zealand White adult female rabbits were repetitively flexed at 1 Hz with an estimated joint contact pressure of 1 to 2 MPa. Joints were collected from loaded and contralateral control specimens, fixed, decalcified, embedded, and thin-sectioned. Sections were examined under polarized light microscopy to identify and measure superficial and mid zone thicknesses of cartilage. Fourier Transform Infrared microspectroscopy was used to measure proteoglycan and collagen contents in the superficial, mid, and deep zones. Loading led to an increase in proteoglycan in the cartilage of all six rabbits. Specifically, there was a 46% increase in the cartilage deep zone (p = 0.003). The collagen content did not change with loading. Joint loading did not change the superficial and mid zone mean thicknesses. We conclude that long-term (80 cumulative hours) cyclical in vivo joint loading stimulates proteoglycan synthesis. Furthermore, stimulation is localized to cartilage regions of high hydrostatic pressure. These data may be useful in developing interventions to prevent overuse injuries or in developing therapies to improve joint function.     

Plant dehydrins: shedding light on structure and expression patterns of dehydrin gene family in barley

Dehydrins, an important group of late embryogenesis abundant proteins, accumulate in response to dehydration stresses and play protective roles under stress conditions. Herein, phylogenetic analysis of the dehydrin family was performed using the protein sequences of 108 dehydrins obtained from 14 plant species based on plant taxonomy and protein subclasses. Sub-cellular localization and phosphorylation sites of these proteins were also predicted. The protein features distinguishing these dehydrins categories were identified using various attribute weighting and decision tree analyses. The results revealed that the presence of the S motif preceding the K motif (Y_nSK_n, SK_n, and S_nKS) was more evident and the Y_nSK_n subclass was more frequent in monocots. In barley, as one of the most drought-tolerant crops, there are ten members of Y_nSK_n out of 13 HvDhns. In promoter regions, six types of abiotic stress-responsive elements were identified. Regulatory elements in UTR sequences of HvDhns were infrequent while only four miRNA targets were found. Furthermore, physiological parameters and gene expression levels of HvDhns were studied in tolerant (HV1) and susceptible (HV2) cultivars, and in an Iranian tolerant wild barley genotype (Spontaneum; HS) subjected to gradual water stress and after recovery duration at the vegetative stage. The results showed the significant impact of dehydration on dry matter, relative leaf water, chlorophyll contents, and oxidative damages in HV2 compared with the other studied genotypes, suggesting a poor dehydration tolerance, and incapability of recovering after re-watering in HV2. Under severe drought stress, among the 13 HvDhns genes, 5 and 10 were exclusively induced in HV1 and HS, respectively. The gene and protein structures and the expression patterns of HvDhns as well as the physiological data consistently support the role of dehydrins in survival and recovery of barley plants from drought particularly in HS. Overall, this information would be helpful for functional characterization of the Dhn family in plants.     

The effects of stretch activation on ionic selectivity of the TREK-2 K2P K+ channel

The TREK-2 (KCNK10) K2P potassium channel can be regulated by variety of polymodal stimuli including pressure. In a recent study, we demonstrated that this mechanosensitive K⁺ channel responds to changes in membrane tension by undergoing a major structural change from its ‘down’ state to the more expanded ‘up’ state conformation. These changes are mostly restricted to the lower part of the protein within the bilayer, but are allosterically coupled to the primary gating mechanism located within the selectivity filter. However, any such structural changes within the filter also have the potential to alter ionic selectivity and there are reports that some K2Ps, including TREK channels, exhibit a dynamic ionic selectivity. In this addendum to our previous study we have therefore examined whether the selectivity of TREK-2 is altered by stretch activation. Our results reveal that the filter remains stable and highly selective for K⁺ over Na⁺ during stretch activation, and that permeability to a range of other cations (Rb⁺, Cs⁺ and NH₄⁺) also does not change. The asymmetric structural changes that occur during stretch activation therefore allow the channel to respond to changes in membrane tension without a loss of K⁺ selectivity.     

Derivation of male germ cells from induced pluripotent stem cells by inducers: A review

Induced pluripotent stem cells (iPSCs) refer to stem cells that are artificially produced using a new technology known as cellular reprogramming, which can use gene transduction in somatic cells. There are numerous potential applications for iPSCs in the field of stem cell biology becauase they are able to give rise to several different cell features of lineages such as three-germ layers. Primordial germ cells, generated via in vitro differentiation of iPSCs, have been demonstrated to produce functional gametes. Therefore, in this review we discussed past and recent advances in the in vitro differentiation of germ cells using pluripotent stem cells with an emphasis on iPSCs. Although this domain of research is still in its infancy, exploring development mechanisms of germ cells is promising, especially in humans, to promote future reproductive and developmental engineering technologies. While few studies have evaluated the ability and efficiency of iPSCs to differentiate toward male germ cells in vitro by different inducers, the given effect was investigated in this review.