Cell Biology and Toxicology

Expression of OPA1 and Mic60 genes and their association with mitochondrial cristae morphology in Tibetan sheep Abstract In order to investigate the relationship between the expression of OPA1 and Mic60 genes and the shape of mitochondrial cristae and to explore the mechanism of Tibetan sheep adapting to a high altitude hypoxia environment, we investigate respiratory rate, mitochondrial cristae and the expression of OPA1 and Mic60 in four different tissues (myocardial, skeletal muscle, spleen and kidney) in Tibetan sheep and Small Tail Han sheep. Tibetan sheep had a higher respiratory rate than Small Tail Han sheep (p < 0.01). In the same tissue, the expression of OPA1 and Mic60 was higher (p < 0.05) in Tibetan sheep than Small Tail Han sheep. Between tissues, the expression of OPA1 and Mic60 was found to be lower (p < 0.05) in spleen than the other three tissues in both breeds. Mitochondrial cristae was dense and clear in myocardial and skeletal muscle but was relatively sparse and slightly swollen in kidney. In spleen, cristae was least and swollen and the gap between the cristae was large. The width of the mitochondrial cristae in the spleen was significantly larger than the width between the inner and outer membranes; however, it had little difference in the other three tissues. The width of mitochondrial cristae was significantly larger in the spleen than that in other tissues (p < 0.05). The numbers of mitochondrial cristae in the four tissues of Tibetan sheep were larger than those in Small Tail Han sheep (p < 0.05). The unique characters of the mitochondrial cristae in Tibetan sheep may be related to its adaption to a high altitude hypoxia environment.

Identification of calretinin-expressing retinal ganglion cells projecting to the mouse superior colliculus Abstract In mice, retinal ganglion cells (RGCs), which consist of around 30 subtypes, exclusively transmit retinal information to the relevant brain systems through parallel visual pathways. The superior colliculus (SC) receives the vast majority of this information from several RGC subtypes. The objective of the current study is to identify the types of calretinin (CR)-expressing RGCs that project to the SC in mice. To label RGCs, we performed CR immunoreactivity in the mouse retina after injections of fluorescent dye, dextran into mouse SC. Subsequently, the neurons double-labeled for dextran and CR were iontophoretically injected with the lipophilic dye, DiI, to characterize the detailed morphological properties of these cells. The analysis of various morphological parameters, including dendritic arborization, dendritic field size and stratification, indicated that, of the ten different types of CR-expressing RGCs in the retina, the double-labeled cells consisted of at least eight types of RGCs that projected to the SC. These cells tended to have small-medium field sizes. However, except for dendritic field size, the cells did not exhibit consistent characteristics for the other morphometric parameters examined. The combination of a tracer and single-cell injections after immunohistochemistry for a particular molecule provided valuable data that confirmed the presence of distinct subtypes of RGCs within multiple-labeled RGCs that projected to specific brain regions.

Oxidative stress modulates the expression of apoptosis-associated microRNAs in bovine granulosa cells in vitro Abstract Despite its essential role in ovulation, oxidative stress (OS) has been found to be cytotoxic to cells, while microRNAs (miRNAs) are known as a major regulator of genes involved in cellular defense against cytotoxicity. However, a functional link between OS and miRNA expression changes in granulosa cells (GCs) remains to be investigated. Here, we investigate the OS modulation of apoptosis-associated miRNAs and their biological relevance in bovine GCs. Following the evaluation of cell viability, accumulation of reactive oxygen species (ROS), cytotoxicity and mitochondrial activity, we used a ready-to-use miRNA PCR array to identify differentially regulated miRNAs. The results showed that exposure to 150 μM H2O2 for 4 h creates remarkable signs of OS in GCs characterized by more than 50% loss of cell viability, higher nuclear factor erythroid 2–related factor 2 (NRF2) nuclear translocation, significantly (p < 0.05) higher abundance of antioxidant genes, significantly (p < 0.001) higher accumulation of ROS, lower mitochondrial activity and a higher (p < 0.001) number of apoptotic nuclei compared to that of the control group. miRNA expression analysis revealed that a total of 69 miRNAs were differentially regulated in which 47 and 22 miRNAs were up- and downregulated, respectively, in stressed GCs. By applying the 2-fold and p < 0.05 criteria, we found 16 miRNAs were upregulated and 10 miRNAs were downregulated. Target prediction revealed that up- and downregulated miRNAs potentially targeted a total of 6210 and 3575 genes, respectively. Pathway analysis showed that upregulated miRNAs are targeting the genes involved mostly in cell survival, intracellular communication and homeostasis, cellular migration and growth control and disease pathways. Our results showed that OS modulates the expression of apoptosis-associated miRNAs that might have effects on cellular or molecular damages.

Dental pulp stem cell transplantation ameliorates motor function and prevents cerebellar atrophy in rat model of cerebellar ataxia Abstract Cerebellar ataxias (CA) include a range of neurodegenerative disorders hallmarked by deterioration of the cerebellum. Cell replacement therapy (CRT) offers a potential remedy for the diseases associated with the central nervous system (CNS). This study was designed to assess the neurorestorative/protective effects of dental pulp stem cell (DPSC) implantation on a rat model of CA induced by 3-acetylpyridine (3-AP) as a neurotoxin. To begin, human DPSCs were extracted, cultured and phenotypically characterized. Then, experimental ataxia was induced in 20 male adult rats by a single injection of 3-AP and bilateral DPSC transplantation was performed 3 days after 3-AP administration, followed by stereological analysis of cerebellar layers along with assessment of motor skills and inflammatory response. The findings showed that transplantation of DPSCs in a 3-AP model of ataxia ameliorated motor coordination and muscle activity, increased cerebellar volumes of molecular and granular layers plus white matter, reduced the levels of inflammatory cytokines and thwarted the degeneration of Purkinje cells against 3-AP toxicity. Taken together, human DPSCs could be considered as a suitable candidate for CRT-based therapies with a specific focus on CA.

Human umbilical cord blood mesenchymal stem cells expansion via human fibroblast-derived matrix and their potentials toward regenerative application Abstract Large expansion of human mesenchymal stem cells (MSCs) is of great interest for clinical applications. In this study, we examine the feasibility of human fibroblast-derived extracellular matrix (hFDM) as an alternative cell expansion setting. hFDM is obtained from decellularized extracellular matrix (ECM) derived from in vitro cultured human lung fibroblasts. Our study directly compares conventional platforms (tissue culture plastic (TCP), fibronectin (FN)-coated TCP) with hFDM using umbilical cord blood-derived MSCs (UCB-MSCs). Early cell morphology shows a rather rounded shape on TCP but highly elongated morphology on hFDM. Cell proliferation demonstrates that MSCs on hFDM were significantly better compared to the others in both 10 and 2% serum condition. Cell migration assay suggests that cell motility was improved and a cell migration marker CXCR4 was notably up-regulated on hFDM. MSCs differentiation into osteogenic lineage on hFDM was also very effective as examined via gene expression, von Kossa staining and alkaline phosphatase activity. In addition, as the MSCs were expanded on each substrate, transferred to 3D polymer mesh scaffolds and then cultivated for a while, the data found better cell proliferation and more CXCR4 expression with MSCs pre-conditioned on hFDM. Moreover, higher gene expression of stemness and engraftment-related markers was noticed with the hFDM group. Furthermore when UCB-MSCs expanded on TCP or hFDM were injected into emphysema (a lung disease) animal model, the results indicate that MSCs pre-conditioned on hFDM (with 2% serum) retain more advanced therapeutic efficacy on the improvement of emphysema than those on TCP. Current works demonstrate that compared to the conventional platforms, hFDM can be a promising source of cell expansion with a naturally derived biomimetic ECM microenvironment and may find some practical applications in regenerative medicine.

A novel serotonin-containing tuft cell subpopulation in mouse intestine Abstract In this study, a novel subset of doublecortin-like kinase 1 (DCLK1)-immunoreactive (IR) tuft cells that also contain serotonin (5-hydroxytryptamine, 5HT) is described, in terms of their number, regional distribution, possible synthesis or reuptake of 5HT and proximity to 5-HT-containing enterochromaffin (EC) cells. The small intestine from C57BL/6J mice was divided into five segments while the large intestine was kept undivided. Double immunostaining was used to estimate numbers and topographic distribution of 5HT-IR (DCLK1/5HT) tuft cells and their possible expression of tryptophan hydroxylase (TPH) and serotonin transporter (SERT). Also, possible contacts between tuft cells and 5HT-IR EC cells were studied. In the small intestine, up to 80% of all tuft cells were identified as DCLK1/5HT-IR; in the large intestine, such cells were rare. The highest number of DCLK1/5HT-IR cells was found in the upper small intestine. The numbers of DCLK1/5HT-IR cells gradually decreased distally. DCLK1-IR tuft cells were not found to contain TPH, the rate-limiting enzyme in 5HT synthesis. SERT, the selective transporter for 5HT reuptake, could not convincingly be demonstrated in tuft cells. In villi and crypts, 3% and 10%, respectively, of all DCLK1-IR cells were in close proximity to EC cells. EC cells in close proximity to DCLK1-IR cells were, in villi and crypts, 3 and 8%, respectively. We conclude that DCLK1/5HT-IR cells constitute a novel subset of tuft cells that may have unique roles in the GI tract.

Vascularized composite allograft rejection is delayed by infusion of IFN-γ-conditioned BMSCs through upregulating PD-L1 Abstract Mesenchymal stromal cells (MSCs) have been applied in prevention from allograft rejection based on their immunomodulatory effects. However, conflicting results have been presented among recent studies, for which one possibility being acknowledged is that the exact effect is determined by the microenvironment when MSCs are applied in vivo. Using a hind limb composite tissue allograft model, we investigate the influence of IFN-γ-preconditioning on the immunomodulatory effects of MSCs and the subsequent allograft survival. Firstly, different doses of IFN-γ were respectively used to incubate with bone marrow–derived MSCs (BMSCs). We found that IFN-γ altered the expression of PD-L1, a major suppressor gene in the immune system during allograft rejection, in a strictly dose-dependent manner in BMSCs. Ten nanograms per milliliter IFN-γ-incubated BMSCs significantly stimulated PD-L1 expression and suppressed T cell proliferation and differentiation, while 50 ng/mL IFN-γ-incubated BMSCs sharply reduced PD-L1 expression. Moreover, we observed that, in contrast to the naive BMSC transplantation group, BMSCs pre-conditioned with 10 ng/mL IFN-γ (BMSCs-IFN-γ) significantly delayed the allograft rejection in vivo. In vitro mixed lymphocyte reaction (MLR) indicated that BMSCs-IFN-γ inhibited T lymphocyte proliferation and activation via PD-L1. Moreover, BMSCs-IFN-γ did not influence the proliferation and activation of T lymphocytes when PD-L1 protein was neutralized by the PD-L1 antibody. These data collectively reveal a role of recipient ongoing immune microenviroment in BMSC-based immunesuppressive therapy. Graphical abstract ᅟ

Sox11-modified mesenchymal stem cells accelerate cartilage defect repair in SD rats Abstract Cartilage has a limited capacity to heal. Previously, we have shown that overexpression of Sox11 in rMSCs (Rat Mesenchymal Stem Cells) by lentivirus-mediated gene transfer leads to enhanced tri-lineage differentiation and accelerated bone formation in fracture model of rats. We observed that the fracture repair in the rats that received Sox11-modified rMSCs injection proceeded through an endochondral ossification process much faster than those in the control groups. However, the detailed role of Sox11 in rMSCs chondrogenic differentiation, as well as cartilage defect, is still not clearly clarified. Therefore, this study tests the hypothesis that Sox11 promotes chondrogenesis and cartilage defect repair by regulating β-catenin. Sox11 was transduced into rMSCs using lentiviruses. The expression levels of β-catenin and its downstream genes were evaluated by quantitative RT-PCR. The transcriptional activation of β-catenin was proved by dual-luciferase reporter assay and co-immunoprecipitation was performed to evaluate Sox11-β-catenin interaction. In addition, a cartilage defect model in SD rats was used to evaluate the cartilage regeneration ability of Sox11-modified rMSCs in vivo. We found that Sox11 transcriptionally activated β-catenin expression and discovered the core promoter region (from − 242 to − 1414) of β-catenin gene for Sox11 binding. In addition, Sox11 might regulate β-catenin at the post-transcriptional level by protein-protein interaction. Finally, using a cartilage defect model in rats, we found Sox11-modified rMSCs could improve cartilage regeneration. Taken together, our study shows that Sox11 is an important regulator of chondrogenesis and Sox11-modified rMSCs may have clinical implication for accelerating cartilage defect healing.

Salutary effect of fenofibrate on type 1 diabetic retinopathy via inhibiting oxidative stress–mediated Wnt/β-catenin pathway activation Abstract Fenofibrate has been shown to have therapeutic effects on diabetic retinopathy (DR). Our previous studies demonstrated that the oxidative stress–activated Wnt/β-catenin pathway plays a pathogenic role in diabetic complications. In the present study, we evaluate the effect and mechanism of fenofibrate on regulating the oxidative stress–activated Wnt/β-catenin pathway by using the genetic type 1 diabetes model of C57BL/6J-Ins2Akitamice and high glucose (HG)–treated ARPE-19. Our results demonstrated that retinal phosphorylation of LRP6 and nuclear β-catenin were increased in C57BL/6J-Ins2Akita mice suggesting activation of Wnt/β-catenin signaling. Meanwhile, C57BL/6J-Ins2Akita showed upregulation of oxidant enzyme Nox4 and Nox2 and downregulation of antioxidant enzyme SOD1 and SOD2. All these alterations were reversed in C57BL/6J-Ins2Akitamice with fenofibrate treatment. Moreover, fenofibrate significantly ameliorated diabetes-induced retinal vascular leakage in C57BL/6J-Ins2Akita mice. In cultured ARPE-19, fenofibrate decreased HG-induced Nox2 and Nox4 upregulation, attenuated SOD1 and SOD2 downregulation and inhibited LRP6 phosphorylation. Moreover, activation of Wnt/β-catenin by Wnt3a conditional medium (WCM) reduced SOD1 and SOD2 and did not affect Nox2 and Nox4. Fenofibrate suppressed WCM-induced LRP6 phosphorylation and reversed SOD downregulation. Importantly, Nox4 overexpression directly phosphorylated LPR6 in ARPE19; conversely, Nox4 knockdown suppressed HG-induced LPR6 phosphorylation. Taken together, Nox-mediated oxidative stress contributes to Wnt/β-catenin activation in DR. Fenofibrate ameliorated DR through coordinate attenuation of oxidative stress and blockade of Wnt/β-catenin signaling.

Early injection of human adipose tissue-derived mesenchymal stem cell after inflammation ameliorates dextran sulfate sodium-induced colitis in mice through the induction of M2 macrophages and regulatory T cells Abstract Inflammatory bowel diseases (IBDs) are sometimes refractory to current therapy or associated with severe adverse events during immunosuppressive therapy; thus, new therapies are urgently needed. Recently, mesenchymal stem cells (MSCs) have attracted attention based on their multitude of functions including anti-inflammatory effects. However, proper timing of MSC therapy and the mechanisms underlying the therapeutic effects of MSCs on colitis are not fully elucidated. Human adipose tissue-derived mesenchymal stem cells (hAdMSCs; 1 × 106) were administrated via the tail vein on day 3 (early) or 11 (delayed) using a 7-day dextran sulfate sodium (DSS)-induced mouse model of colitis. The effects were evaluated based on colon length, disease activity index (DAI) and histological score. Cytokine-encoding mRNA levels T cells and macrophages were evaluated by real-time PCR and flow cytometry. Regarding the timing of administration, early (day 3) injection significantly ameliorated DSS-induced colitis in terms of both DAI and histological score, compared to those parameters with delayed (day 11) injection. With early cell injection, the tissue mRNA levels of anti-inflammatory cytokine genes (Il10, Tgfb) increased, whereas those of inflammatory cytokine genes (Il6, Tnfa and Il17a) decreased significantly. Regarding the associated mechanism, hAdMSCs suppressed T cell proliferation and activation in vitro, increased the number of regulatory T cells in vivo and changed the polarity of macrophages (into the anti-inflammatory M2 phenotype) in vitro. Timing of injection is critical for the effective therapeutic effects of hAdMSCs. Furthermore, part of the associated mechanism includes T cell activation and expansion and altered macrophage polarization.