Proprotein convertases 1 and 2 (PC1 and PC2) are expressed in neurally differentiated rat bone marrow stromal stem cells (BMSCs)

Exposure to polystyrene microplastics reduces regeneration and growth in planarians

The potential adverse effects of microplastics (MPs) on ecosystems and human health have received much attention in recent years. However, only limited data are available on the mechanisms for the uptake, distribution, and effects of MPs in freshwater organisms, especially with respect to tissue repair, regeneration and impairment of stem cell functions. To address this knowledge gap, we conducted exposure experiments in which planarians (Dugesia japonica) were exposed to polystyrene (PS)-MPs mixed in liver homogenate and examined the tissue growth and regeneration, stem cell functions, and oxidative stress. The body and blastema areas decreased upon exposure to PS-MPs, indicating that the growth and regeneration of planarians were delayed. The proliferation and differentiation processes of stem cells were inhibited, and the proportion of mitotic stem cells decreased, which may be related to the activation of the TGFβ/SMAD4 and Notch signaling pathways. The enhancement of antioxidant enzyme activities and malondialdehyde on the first day of exposure to PS-MPs confirmed the oxidative stress response of planarians to PS-MPs. The present study demonstrated the likelihood of biotoxicity induced by PS-MPs. These results will provide clues for further investigations into the potential risks of PS-MPs to human stem cells.

Investigation of gene expressions in differentiated cell derived bone marrow stem cells during bone morphogenetic protein-4 treatments with Fourier transform infrared spectroscopy

A model was set up to predict the differentiation patterns based on the data extracted from FTIR spectroscopy. For this reason, bone marrow stem cells (BMSCs) were differentiated to primordial germ cells (PGCs). Changes in cellular macromolecules in the time of 0, 24, 48, 72, and 96h of differentiation, as different steps of the differentiation procedure were investigated by using FTIR spectroscopy. Also, the expression of pluripotency (Oct-4, Nanog and c-Myc) and specific genes (Mvh, Stella and Fragilis) were investigated by real-time PCR. However, the expression of genes in five steps of differentiation was predicted by FTIR spectroscopy. FTIR spectra showed changes in the template of band intensities at different differentiation steps. There are increasing changes in the stepwise differentiation procedure for the ratio area of CH2, which is symmetric to CH2 asymmetric stretching. An ensemble of expert methods, including regression tree (RT), boosting algorithm (BA), and generalized regression neural network (GRNN), was the best method to predict the gene expression by FTIR spectroscopy. In conclusion, the model was able to distinguish the pattern of different steps from cell differentiation by using some useful features extracted from FTIR spectra.

Role of injured pancreatic extract promotes bone marrow-derived mesenchymal stem cells efficiently differentiate into insulin-producing cells

Mesenchymal stem cells (MSCs) can be successfully induced to differentiate into insulin-producing cells （IPCs) by a variety of small molecules and cytokines in vitro. However, problems remain, such as low transdifferentiation efficiency and poor maturity of trans-differentiated cells. The damaged pancreatic cells secreted a large amount of soluble proteins, which were able to promote pancreative islet regeneration and MSCs differentiation. In this study, we utilized the rat injured pancreatic tissue extract to modulate rat bone marrow-derived MSCs differentiation into IPCs by the traditional two-step induction. Our results showed that injured pancreatic tissue extract could effectively promote the trans-differentiation efficiency and maturity of IPCs by the traditional induction. Moreover, IPCs were able to release more insulin in a glucose-dependent manner and ameliorate better the diabetic conditions of streptozotocin (STZ)-treated rats. Our study provides a new strategy to induce an efficient and directional differentiation of MSCs into IPCs.

Messenger RNA expression patterns of p75 neurotrophin receptor and tropomyosin-receptor-kinase A following spinal cord injury

BACKGROUND

Induction of p75 neurotrophin receptor (p75NTR) could be one of the first steps that initiate apoptotic cascade after injury, or it may indicate regeneration responses undertaken by the injured system, possibly in collaboration with resident tropomyosin-receptor-kinase (Trk).

OBJECTIVE

To measure quantitative changes in messenger RNA (mRNA) expression levels of p75NTR, Trk A, and caspase-9 in rat's injured spinal cord (SCI). The reciprocal interaction between Trk and p75NTR signaling pathways can dictate cellular responses to neurotrophins. p75NTR can regulate Trk-dependent responses, but the role of Trk in regulating p75NTR-dependent signaling is not well documented.

DESIGN

Using real-time polymerase chain reaction, this study analyzed changes in the mRNA abundance of the mentioned genes at 6, 24, and 72 hours and 7 and 10 days after SCI in adult male rats. SCI was induced at T9 level by transsection.

RESULTS

Results show a complicated temporal and spatial pattern of alteration with different degrees and direction (up- or down-regulation) in p75NTR, Trk A, and caspase-9 mRNA expression levels after SCI. The greatest variation was seen in center regions following SCI. This study shows that alteration in p75NTR, Trk A, and caspase-9 expression starts as early as 6 hours after SCI. Alterations in p75NTR, Trk A, and caspase-9 expression within the spinal cord may play a key role in the apoptotic cell death.

CONCLUSION

Results suggest that the role of p75NTR is to eliminate damaged cells by activating the apoptotic machinery, especially at the center of damage and during first week after injury.

Alpha cells come of age

The alpha cells that coinhabit the islets with the insulin-producing beta cells have recently captured the attention of diabetes researchers because of new breakthrough findings highlighting the importance of these cells in the maintenance of beta cell health and functions. In normal physiological conditions alpha cells produce glucagon but in conditions of beta cell injury they also produce glucagon-like peptide-1 (GLP-1), a growth and survival factor for beta cells. In this review we consider these new findings on the functions of alpha cells. Alpha cells remain somewhat enigmatic inasmuch as they now appear to be important in the maintenance of the health of beta cells, but their production of glucagon promotes diabetes. This circumstance prompts an examination of approaches to coax alpha cells to produce GLP-1 instead of glucagon.

Subtilisin-like proprotein convertase expression, localization, and activity in the human retina and optic nerve head

PURPOSE

Subtilisin-like proprotein convertases (SPCs) are a family of calcium-dependent cleavage enzymes that act on dibasic sites of various peptide/protein substrates. The purpose of this study was to investigate the expression, localization, and activity of SPCs in the human retina and optic nerve head.

METHODS

mRNA expression of the SPC family in the human retina and optic nerve head tissues was evaluated by quantitative reverse transcription polymerase chain reaction (QRT-PCR). Double immunofluorescence staining was performed on paraffin-embedded human posterior sections to localize SPC family members. Western blot analysis was used to identify PACE4 isoform expression within the optic nerve head and retina. In addition, a fluorogenic SPC substrate-based assay was used to elucidate SPC enzyme activity within human retina and optic nerve head (ONH) tissues.

RESULTS

QPCR results indicated that PC1 and PC2 were expressed 4.1- and 5.7-fold higher in retina compared to optic nerve head, whereas PACE4 was expressed 4.1-fold higher in the ONH. PC1 and PC2 were localized primarily in neuronal cells, whereas PACE4 and PC5 were limited to the glia of the retina and optic nerve head. SPC activity in ONH lysate was significantly higher than that of retinal lysate; however, when an SPC inhibitor was added, activity in ONH decreased more than that in retina.

CONCLUSIONS

These results indicate that the SPCs are expressed in distinct patterns throughout the human retina and ONH. PC1 and PC2 were primarily expressed in neurons, whereas PACE4 appeared to be largely restricted to glia. Thus, elevated PACE4 may modulate the bioactivity of proteins secreted in the ONH and retina.

Gene expression alterations of neurotrophins, their receptors and prohormone convertases in a rat model of spinal cord contusion

We have used a semi-quantitative RT-PCR approach to investigate the alterations in the expression of the main regulators of neuronal survival and death, neurotrophins (NTs), NT receptors, and prohormone convertases (PC), in a rat model of spinal cord contusion. Our results revealed that the expression of the members of NT family (Nerve-Growth Factor (NGF), Brain-Derived Neurotrophic Factor (BDNF), and Neurotrophin-3 (NT-3)) is significantly declined in the injured spinal cord, as early as 6h after the induction of the contusion. The expression was recovered afterward to that of the control levels. Furthermore, the expression of all NTs high-affinity Trk receptors decreased severely after the contusion. While the expression of TrkA and TrkC were completely shut down after 6 and 12h after injury respectively, the expression of TrkB receptor declined at 12h after injury and remained at this low level thereafter. In contrast to the pattern of Trk receptor expression, p75NTR receptor showed a significant upregulation after contusion. The expression of PC members functioning in the constitutive secretory pathway, i.e. furin, PACE4 and PC7, increased after damage, while the expression of PC members acting in regulated secretory pathway, PC1 and PC2, reduced after spinal cord injury. All together, the down-regulation of NTs, their designated Trk receptors and PC1/PC2 enzymes along with an upregulation of p75NTR promote neuronal death after injury. Our results suggest that either overexpression of NTs, Trk receptors and PC1/PC2 or interfering with the expression of p75NTR in host and/or grafted cells before transplantation could increase the success of the transplantation.

Knocking-down the expression of nucleostemin significantly decreases rate of proliferation of rat bone marrow stromal stem cells in an apparently p53-independent manner

OBJECTIVES

Nucleostemin (NS) is a recently identified GTP-binding protein, predominantly expressed in embryonic and adult stem cells but not in terminally differentiated cells. NS is expressed in bone marrow-derived mesenchymal stem cells, and its expression ceases upon induction of neural differentiation. The major aim of this study was to determine whether down-regulation of NS expression acts as a promoter, or otherwise as a by-product of differentiation and senescence processes.

MATERIALS AND METHODS

We used RNA interference protocols to specifically knock down NS in rat bone marrow-derived stromal stem cells. Changes in rate of proliferation and cell cycle profile after knocking-down of NS were measured. In addition, changes in expression of associated genes were studied by semiquantitative RT-PCR, Western blotting and immunocytochemistery.

RESULTS

Knocked-down expression of NS caused a significant decrease in the rate of cell proliferation with concomitant shutting off of expression of cyclin D1 and survivin, two other well-known regulators of cell proliferation. Interestingly, we noticed no obvious changes in expression level of p21, the main effector of p53 for its cell cycle repressing function.

CONCLUSION

Our findings revealed a master role for NS in promoting proliferation of rat bone marrow-derived stromal stem cells. Moreover, we suggest that despite previous proposals, the cell cycle arrest/inhibitory role of NS is unlikely to be related to its proposed property of interaction with p53.