An Attenuated Variant of the GDVII Strain of Theiler’s Virus Does Not Persist and Does Not Infect the White Matter of the Central Nervous System

The DA strain of Theiler’s virus causes a persistent and demyelinating infection of the white matter of spinal cord, whereas the GDVII strain causes a fatal gray-matter encephalomyelitis. Studies with recombinant viruses showed that this difference in phenotype is controlled mainly by the capsid. However, conflicting results regarding the existence of determinants of persistence in the capsid of the GDVII strain have been published. Here we show that a GDVII virus whose neurovirulence has been attenuated by an insertion in the 5′ noncoding region does not persist in the central nervous systems of mice. Furthermore, this virus infects the gray matter efficiently, but not the white matter. These results confirm the absence of determinants of persistence in the GDVII capsid. They suggest that the DA capsid controls persistence by allowing the virus to infect cells in the white matter of the spinal cord.     

MCP/CCR2 Signaling Is Essential for Recruitment of Mesenchymal Progenitor Cells during the Early Phase of Fracture Healing

Objective

The purpose of this study was to investigate chemokine profiles and their functional roles in the early phase of fracture healing in mouse models.

Methods

The expression profiles of chemokines were examined during fracture healing in wild-type (WT) mice using a polymerase chain reaction array and histological staining. The functional effect of monocyte chemotactic protein-1 (MCP-1) on primary mouse bone marrow stromal cells (mBMSCs) was evaluated using an in vitro migration assay. MCP-1^−/− and C-C chemokine receptor 2 (CCR2)^−/− mice were fractured and evaluated by histological staining and micro-computed tomography (micro-CT). RS102895, an antagonist of CCR2, was continuously administered in WT mice before or after rib fracture and evaluated by histological staining and micro-CT. Bone graft exchange models were created in WT and MCP-1^−/− mice and were evaluated by histological staining and micro-CT.

Results

MCP-1 and MCP-3 expression in the early phase of fracture healing were up-regulated, and high levels of MCP-1 and MCP-3 protein expression observed in the periosteum and endosteum in the same period. MCP-1, but not MCP-3, increased migration of mBMSCs in a dose-dependent manner. Fracture healing in MCP-1^−/− and CCR2^−/− mice was delayed compared with WT mice on day 21. Administration of RS102895 in the early, but not in the late phase, caused delayed fracture healing. Transplantation of WT-derived graft into host MCP-1^−/− mice significantly increased new bone formation in the bone graft exchange models. Furthermore, marked induction of MCP-1 expression in the periosteum and endosteum was observed around the WT-derived graft in the host MCP-1^−/− mouse. Conversely, transplantation of MCP-1^−/− mouse-derived grafts into host WT mice markedly decreased new bone formation.

Conclusions

MCP-1/CCR2 signaling in the periosteum and endosteum is essential for the recruitment of mesenchymal progenitor cells in the early phase of fracture healing.     

Xenotransplantation of Human Cardiomyocyte Progenitor Cells Does Not Improve Cardiac Function in a Porcine Model of Chronic Ischemic Heart Failure. Results from a Randomized,Blinded, Placebo Controlled Trial

Background

Recently cardiomyocyte progenitor cells (CMPCs) were successfully isolated from fetal and adult human hearts. Direct intramyocardial injection of human CMPCs (hCMPCs) in experimental mouse models of acute myocardial infarction significantly improved cardiac function compared to controls.

Aim

Here, our aim was to investigate whether xenotransplantation via intracoronary infusion of fetal hCMPCs in a pig model of chronic myocardial infarction is safe and efficacious, in view of translation purposes.

Methods & Results

We performed a randomized, blinded, placebo controlled trial. Four weeks after ischemia/reperfusion injury by 90 minutes of percutaneous left anterior descending artery occlusion, pigs (n = 16, 68.5 ± 5.4 kg) received intracoronary infusion of 10 million fetal hCMPCs or placebo. All animals were immunosuppressed by cyclosporin (CsA). Four weeks after infusion, endpoint analysis by MRI displayed no difference in left ventricular ejection fraction, left ventricular end diastolic and left ventricular end systolic volumes between both groups. Serial pressure volume (PV-)loop and echocardiography showed no differences in functional parameters between groups at any timepoint. Infarct size at follow-up, measured by late gadolinium enhancement MRI showed no difference between groups. Intracoronary pressure and flow measurements showed no signs of coronary obstruction 30 minutes after cell infusion. No premature death occurred in cell treated animals.

Conclusion

Xenotransplantation via intracoronary infusion of hCMPCs is feasible and safe, but not associated with improved left ventricular performance and infarct size compared to placebo in a porcine model of chronic myocardial infarction.     

Reduced Proliferation of Oligodendrocyte Progenitor Cells in the Postnatal Brain of <Emphasis Type="Italic">Dystonia Musculorum</Emphasis> Mice

Dystonia musculorum (dt) mice show sensory neurodegeneration and movement disorder, such as dystonia and cerebellar ataxia. The causative gene Dystonin (Dst) encodes a cytoskeleton linker protein. Although sensory neurodegeneration has been well studied, glial cell responses in the central nervous system (CNS) are poorly understood. Here, we investigated cell proliferation in the CNS of Dst ^Gt homozygous mice using newly generated in situ hybridization (ISH) probes—Ki-67 and proliferating cell nuclear antigen (PCNA) probes—both of which effectively detect proliferating cells. We found that Ki-67-positive cells were significantly decreased in the corpus callosum and thalamus of dt brain at postnatal day 21 (P21). There is a similar but not significant tendency at postnatal day 14 (P14) in the dt brain. We also confirmed the reduced proliferation by PCNA ISH and Ki-67 immunohistochemistry. Double staining with cell-type-specific markers revealed that proliferating cells are oligodendrocyte progenitor cells (OPCs) in both wild-type and dt brain. We also observed a reduced number of Olig2-positive cells in the corpus callosum of Dst ^Gt homozygous mice at P21, indicating that reduced proliferation resulted in a reduced number of OPCs. Our data indicate that OPCs proliferation is reduced in the dt mouse brain at the postnatal stage and that it subsequently results in the reduced number of OPCs.     

FOXO3a沉默或过表达对内皮祖细胞增殖的影响

观察FOXO3a(forkhead box O3a)沉默或过表达对内皮祖细胞(endothelial progenitorcells,EPCs)增殖的影响。构建了沉默型Ad-shRNA-FOXO3a和突变型Ad-TM(triple mutant)-FOXO3a重组腺病毒载体。密度梯度离心法结合荧光激活细胞分选(fluorescence-activated cell sorting,FACS)分离人脐血来源的EPCs(CD133+CD34+),并进行体外培养及免疫荧光鉴定。将上述重组腺病毒载体转染EPCs并观察转染效率与细胞形态学改变;Western blot分析FOXO3a蛋白表达变化;细胞计数与MTT法分析FOXO3a沉默或过表达对EPCs增殖的影响。成功构建了Ad-shRNA-FOXO3a、Ad-TM-FOXO3a重组腺病毒载体并转染人脐血来源EPCs。Western blot提示,Ad-shRNA-FOXO3a转染EPCs后明显抑制了FOXO3a蛋白的表达;Ad-TM-FOXO3a转染EPCs后明显增加了FOXO3a蛋白的表达。结合细胞形态学改变、细胞计数与MTT法实验结果提示,有效沉默FOXO3a明显促进了EPCs增殖;FOXO3a过表达明显抑制了EPCs增殖。人脐血来源的EPCs中,FOXO3a参与了细胞增殖的调节。     

白鹮胃肠道内分泌细胞的免疫组织化学定位

为了解白的消化生理过程 ,利用ABC免疫组织化学方法 ,对白胃肠道 5种内分泌细胞 :5 -羟色胺 (5 HT)、脑啡肽、P物质、胃动素和抑胃素的分布进行了研究。结果表明 :5 HT细胞主要分布于十二指肠及其以下部位 ,尤其是盲肠和直肠 ;而腺胃、肌胃和幽门中均未发现该类细胞。脑啡肽和P物质细胞数量明显较 5 HT少 ,它们稀疏分布于十二指肠及其以下部位 ,无显著的分布积聚区。抑胃素和胃动素在整个胃肠道中均无分布。分析表明白胃肠道 5种内分泌细胞的分布与其他鸟类相似 ,但与其他脊椎动物明显不同。     

Proliferation of Submesothelial Mesenchymal Cells during Early Phase of Serosal Thickening in the Rabbit Bladder Is Accompanied by Transient Keratin 18 Expression

Partial outlet obstruction of the rabbit bladder induces serosal thickening and smooth muscle (SM) hypertrophy. Within thickened serosa, submesothelial (mesenchymal) cells differentiate into SM cells after 30 days of obstruction [S. Buoroet al. Lab. Invest.69, 589–602, 1993]. Here, we show that submesothelial cells transiently express keratin (K) 18 but not K8 soon after obstruction. We investigated a possible relationship between keratin expression and cell proliferation/differentiationin vivoandin vitro.The results of this study indicate that expression of K18 is spatiotemporally related to the pattern of cell proliferation with respect to the localization of an elastic membrane which divides the thickened serosa into an “extrinsic” and an “intrinsic” region. Moreover, K18 is not present in bladder mesenchyma during early development, indicating that its expression in the adult is not attributable to a dedifferentiation process. However, simultaneous K18, K8, and desmoplakin (DP) expression can be induced in normal and thickened serosa upon treatment with bromo-deoxyuridine. Our results indicate that K18 is a marker of proliferating mesenchymal cells in rabbit serosa, whereas the combined expression of K18, K8, and DP might be related to the hypothesized alterations in the stability of gene expression. A model is proposed in which keratin-containing submesothelial cells can act as a “transit” cell phenotype involved in both regenerating mesothelial cells and formation of SM cells.     

The Niche Factor Syndecan-1 Regulates the Maintenance and Proliferation of Neural Progenitor Cells during Mammalian Cortical Development

Neural progenitor cells (NPCs) divide and differentiate in a precisely regulated manner over time to achieve the remarkable expansion and assembly of the layered mammalian cerebral cortex. Both intrinsic signaling pathways and environmental factors control the behavior of NPCs during cortical development. Heparan sulphate proteoglycans (HSPG) are critical environmental regulators that help modulate and integrate environmental cues and downstream intracellular signals. Syndecan-1 (Sdc1), a major transmembrane HSPG, is highly enriched in the early neural germinal zone, but its function in modulating NPC behavior and cortical development has not been explored. In this study we investigate the expression pattern and function of Sdc1 in the developing mouse cerebral cortex. We found that Sdc1 is highly expressed by cortical NPCs. Knockdown of Sdc1 in vivo by in utero electroporation reduces NPC proliferation and causes their premature differentiation, corroborated in isolated cells in vitro. We found that Sdc1 knockdown leads to reduced levels of β-catenin, indicating reduced canonical Wnt signaling. Consistent with this, GSK3β inhibition helps rescue the Sdc1 knockdown phenotype, partially restoring NPC number and proliferation. Moreover, exogenous Wnt protein promotes cortical NPC proliferation, but this is prevented by Sdc1 knockdown. Thus, Sdc1 in the germinal niche is a key HSPG regulating the maintenance and proliferation of NPCs during cortical neurogenesis, in part by modulating the ability of NPCs to respond to Wnt ligands.     

Physical Condition Does Not Affect Gravity-Induced Loss of Consciousness during Human Centrifuge Training in Well-Experienced Young Aviators

Background

Consensus on whether physical condition affects the risk of gravity-induced loss of consciousness (G-LOC) has not been reached, and most previous studies about the issue did not include well-experienced aviators. We compared the physical conditions of well-experienced young aviators according to the occurrence of G-LOC during human centrifuge training.

Methods

Among 361 young male aviators on active flight duty with experience in high performance aircrafts for at least 2 years, 350 had full data available and were reviewed in this study. We divided the aviators into the G-LOC group and the non-G-LOC group according to their human centrifuge training results. We then compared their basic characteristics, body composition, physical fitness level, and pulmonary function.

Results

Twenty nine aviators (8.3%) who experienced G-LOC during human centrifuge training in their first trials were classified into the G-LOC group. There was no difference in physical condition of aviators between the two groups.

Conclusions

Young aviators with experience in G-LOC showed no difference in physical condition such as muscle mass, strength, and general endurance from the aviators with no such experience. Although more studies are needed, physical condition does not seem to be a significant determinant of G-LOC among the experienced aviators.     

Enhanced PD-1 Expression by T Cells in Cerebrospinal Fluid Does Not Reflect Functional Exhaustion during Chronic Human Immunodeficiency Virus Type 1 Infection

During chronic viral infections, T cells are exhausted due to constant antigen exposure and are associated with enhanced programmed death 1 (PD-1) expression. Deficiencies in the PD-1/programmed death-ligand 1 (PD-L1) pathway are associated with autoimmune diseases, including those of the central nervous system (CNS). To understand the role of PD-1 expression in regulating T-cell immunity in the CNS during chronic infection, we characterized PD-1 expression in cerebrospinal fluid (CSF) and blood of individuals with chronic human immunodeficiency virus type 1 (HIV-1) infection. PD-1 expression was higher on HIV-specific CD8⁺ T cells than on total CD8⁺ T cells in both CSF and blood. PD-1 expression on CSF T cells correlated positively with CSF HIV-1 RNA and inversely with blood CD4⁺ T-cell counts, suggesting that HIV-1 infection drives higher PD-1 expression on CSF T cells. However, in every HIV-positive individual, PD-1 expression was higher on T cells in CSF than on those in blood, despite HIV-1 RNA levels being lower. Among healthy HIV-negative controls, PD-1 expression was higher in CSF than in blood. Furthermore, frequencies of the senescence marker CD57 were lower on CSF T cells than on blood T cells, consistent with our prior observation of enhanced ex vivo functional capacity of CSF T cells. The higher PD-1 expression level on CSF T cells therefore does not reflect cellular exhaustion but may be a mechanism to downregulate immune-mediated tissue damage in the CNS. As inhibition of the PD-1/PD-L1 pathway is pursued as a therapeutic option for viral infections, potential effects of such a blockade on development of autoimmune responses in the CNS should be considered.Programmed death 1 (PD-1; also called CD279) and its ligands, PD-L1 (also called B7-H1 or CD274) and PD-L2 (also known as B7-DC or CD-273), regulate T-cell activation, peripheral tolerance, and autoimmunity (22, 43). PD-1 can be expressed on CD8⁺ and CD4⁺ T cells, B cells, natural killer T cells, and activated monocytes. PD-L1 is expressed on various cells, including T and B cells, dendritic cells, macrophages, mast cells, nonhematopoietic cell types (including vascular endothelial cells, pancreatic islet cells, astrocytes, keratinocytes, and microglial cells), and cells in immune privileged sites, including the placenta and the eye (22). PD-L2 expression is inducible and is restricted to dendritic cells, monocytes, macrophages, and mast cells (22). During chronic infections, the PD-1/PD-L1 pathway inhibits antigen-specific T-cell responses (7, 8, 35, 46). In human immunodeficiency virus type 1 (HIV-1)-infected individuals, PD-1 expression on HIV-specific T cells in peripheral blood is upregulated and correlates positively with plasma viremia and inversely with CD4⁺ T-cell counts (7, 46). PD-1 expression on HIV-specific T cells is also associated with T-cell exhaustion, as defined by a reduced ability to proliferate and produce cytokines (7, 46). Inhibition of the PD-1/PD-L1 pathway augments HIV-specific CD8⁺ and CD4⁺ T-cell function, and antiretroviral therapy is associated with a significant reduction of PD-1 expression on HIV-specific T cells in peripheral blood (8).The PD-1/PD-L1 pathway also limits immune-mediated tissue damage that may be caused by overreactive peripheral T cells, especially in immune privileged sites such as the central nervous system (CNS). In 1999, the importance of PD-1 for peripheral tolerance was first suggested by studies which showed that PD1^−/− mice develop lupus-like autoimmune diseases (32). In humans, polymorphisms in the PDCD1 gene, which encodes PD-1, have been associated with autoimmune diseases, including lupus, diabetes, rheumatoid arthritis, and multiple sclerosis (20, 21, 25). Upregulation of PD-L1 in multiple sclerosis lesions from human brain tissue suggests a role for the PD-1/PD-L1 pathway in regulating T-cell activation and controlling immunopathological damage (33).The CNS is involved by HIV-1 early during primary infection (6, 13), and approximately 40% of patients who develop advanced AIDS without receiving antiretroviral therapy develop cognitive impairment (6, 13, 38). While HIV-1 proteins gp120 (3, 16) and Tat (30) are directly neurotoxic and may contribute to HIV-associated dementia, detrimental neuropathogenic effects have also been postulated for inflammatory and innate immune cells, especially monocytes/macrophages and T cells (11, 19, 49, 50). Immune responses cause neuropathogenesis during other viral infections, and cytotoxic T lymphocytes can worsen the disease through direct cytotoxicity or release of inflammatory cytokines such as gamma interferon (IFN-γ) (14). However, we recently described higher frequencies of functional HIV-specific CD8⁺ T cells in cerebrospinal fluid (CSF) than in blood among asymptomatic HIV-positive individuals with little or no HIV-1 RNA in CSF, suggesting that HIV-1-specific CD8⁺ T cells help to control intrathecal viral replication (40).To understand the role of the PD-1/PD-L1 pathway in regulating T-cell responses during viral infection of the CNS, we characterized PD-1 expression on T cells in CSF and peripheral blood among asymptomatic HIV-positive individuals. We hypothesized that T-cell PD1 expression would be lower in CSF than in blood, since HIV-1 RNA concentrations are lower in CSF than in plasma and the magnitude and breadth of IFN-γ-secreting HIV-specific T cells are greater in CSF than in blood (40). We show that, in CSF, HIV-1 RNA correlates directly with PD-1 expression on CD4⁺, CD8⁺, and HIV-specific CD8⁺ T cells. Unexpectedly, PD-1 expression on all T cells is higher in CSF than in blood in HIV-positive patients and healthy HIV-negative controls. In contrast, expression of the senescence marker CD57 is lower in CSF than in blood. These data suggest that higher PD-1 expression on T cells in CSF may be a mechanism to regulate T-cell immunity in the CNS, rather than indicating T-cell exhaustion, and that this regulation is increased by HIV-1 replication.     

Sirtuin1 Over-Expression Does Not Impact Retinal Vascular and Neuronal Degeneration in a Mouse Model of Oxygen-Induced Retinopathy

Proliferative retinopathy is a leading cause of blindness, including retinopathy of prematurity (ROP) in children and diabetic retinopathy in adults. Retinopathy is characterized by an initial phase of vessel loss, leading to tissue ischemia and hypoxia, followed by sight threatening pathologic neovascularization in the second phase. Previously we found that Sirtuin1 (Sirt1), a metabolically dependent protein deacetylase, regulates vascular regeneration in a mouse model of oxygen-induced proliferative retinopathy (OIR), as neuronal depletion of Sirt1 in retina worsens retinopathy. In this study we assessed whether over-expression of Sirtuin1 in retinal neurons and vessels achieved by crossing Sirt1 over-expressing flox mice with Nestin-Cre mice or Tie2-Cre mice, respectively, may protect against retinopathy. We found that over-expression of Sirt1 in Nestin expressing retinal neurons does not impact vaso-obliteration or pathologic neovascularization in OIR, nor does it influence neuronal degeneration in OIR. Similarly, increased expression of Sirt1 in Tie2 expressing vascular endothelial cells and monocytes/macrophages does not protect retinal vessels in OIR. In addition to the genetic approaches, dietary supplement with Sirt1 activators, resveratrol or SRT1720, were fed to wild type mice with OIR. Neither treatment showed significant vaso-protective effects in retinopathy. Together these results indicate that although endogenous Sirt1 is important as a stress-induced protector in retinopathy, over-expression of Sirt1 or treatment with small molecule activators at the examined doses do not provide additional protection against retinopathy in mice. Further studies are needed to examine in depth whether increasing levels of Sirt1 may serve as a potential therapeutic approach to treat or prevent retinopathy.     

Immunohistochemical Markers of Neural Progenitor Cells in the Early Embryonic Human Cerebral Cortex

The development of the human central nervous system represents a delicate moment of embryogenesis. The purpose of this study was to analyze the expression of multiple immunohistochemical markers in the stem/progenitor cells in the human cerebral cortex during the early phases of development. To this end, samples from cerebral cortex were obtained from 4 human embryos of 11 weeks of gestation. Each sample was formalin-fixed, paraffin embedded and immunostained with several markers including GFAP, WT1, Nestin, Vimentin, CD117, S100B, Sox2, PAX2, PAX5, Tβ4, Neurofilament, CD44, CD133, Synaptophysin and Cyclin D1. Our study shows the ability of the different immunohistochemical markers to evidence different zones of the developing human cerebral cortex, allowing the identification of the multiple stages of differentiation of neuronal and glial precursors. Three important markers of radial glial cells are evidenced in this early gestational age: Vimentin, Nestin and WT1. Sox2 was expressed by the stem/progenitor cells of the ventricular zone, whereas the postmitotic neurons of the cortical plate were immunostained by PAX2 and NSE. Future studies are needed to test other important stem/progenitor cells markers and to better analyze differences in the immunohistochemical expression of these markers during gestation.Key words: Cerebral cortex, human embryo, human development, immunohistochemistry, fetal stem cells     

Loss of Bace1 in Mice Does Not Alter the Severity of Caerulein Induced Pancreatitis

ContextBeta-site alpha-amyloid protein cleaving enzyme1 (BACE1) plays a key role in the pathogenesis of Alzheimer’s disease. Additional to its moderate expression in the brain, high levels of BACE1 mRNA were found in the pancreas. Murine Bace1 has been immunohistochemicaly detected at the apical pole of acinar cells within the exocrine pancreas of mice and Bace1 activity was observed in pancreatic juice. In vitro experiments revealed enteropeptidase as a putative substrate for Bace1 suggesting a role in acute pancreatitis.ObjectiveThe aim of this study was to address a protective mechanism of Bace1 in acute experimental pancreatitis in mice.MethodsAcute experimental pancreatitis was induced by intraperitoneal injection of caerulein in homozygote Bace1^-/- mice and wild type mice. Serum and tissue analyses were carried out after 4 h, 8 h and 24 h. Measurement of plasma amylase and lipase was performed to confirm pancreatitis induction. In order to assess the severity of pancreatitis H&E stained pancreatic sections were examined regarding edema, inflammation and apoptosis. Immunohistochemical detection of myeloperoxidase (MPO) positive cells was carried out to further quantify the extent of inflammation. Expression of Bace2 within the pancreas was analyzed by immunohistochemistry and RT-qPCR.ResultsWe demonstrate that total loss of Bace1 in mice leads to no alterations in the course of acute experimental caerulein-pancreatitis. Bace1^-/- mice develop a moderate pancreatitis that is comparable in histomorphological and serological features with those seen in wild type mice.DiscussionWe discuss the results in the context of the applied caerulein induced edematous pancreatitis model and possible compensatory mechanisms via Bace2 that might be responsible for the observed results.     

The Selective Vulnerability of Retinal Ganglion Cells in Rat Chronic Ocular Hypertension Model at Early Phase

Glutamate neurotoxicity has been postulated to play a prominent role in glaucoma. In this study the possible roles of two subunits of glutamate receptors during the early phase of retinal ganglion cell (RGC) loss in a rat chronic ocular hypertension (COH) model were investigated. COH was induced by applying argon laser to the episcleral and limbal veins of the right eye of rats, the observation times were at 4, 14 and 28 days after the first laser. RGCs were retrogradely labeled by putting Fluoro-Gold (FG) on the surface of both side superior colliculus. Immunohistochemical staining using specific antibodies against N-methyl-d-aspartate receptor 1 (NR1) or glutamate receptor 2/3 (GluR2/3) was performed on the retinal sections of normal and COH eyes. Fluorescent images were captured using confocal laser scanning microscope and the number of NR1 and GluR2/3 labeled cells were counted and cell size was measured using Stereo Investigator. During the observation period, the numbers of NR1 and GluR2/3 positive RGCs in the RGC layer were reduced parallel to the loss of RGC. The dramatic loss of GluR2/3 immunoreactive neurons occurred starting immediately after the first laser to 4 days while the dramatic loss of NR1 immunoreactive neurons occurred from 14 to 28 days after the first laser. Size difference was detected in NR1 immunoreactive RGCs, large ones were more sensitive to the high ocular pressure. These results suggest that both NR1 and GluR2/3 are involved in the mediation of RGC death in the early stage of COH.     

Systemic Compensatory Response to Neonatal Estradiol Exposure Does Not Prevent Depletion of the Oocyte Pool in the Rat

The formation of ovarian follicles is a finely tuned process that takes place within a narrow time-window in rodents. Multiple factors and pathways have been proposed to contribute to the mechanisms triggering this process but the role of endocrine factors, especially estrogens, remains elusive. It is currently hypothesized that removal from the maternal hormonal environment permits follicle formation at birth. However, experimentally-induced maintenance of high 17β-estradiol (E2) levels leads to subtle, distinct, immediate effects on follicle formation and oocyte survival depending on the species and dose. In this study, we examined the immediate effects of neonatal E2 exposure from post-natal day (PND) 0 to PND2 on the whole organism and on ovarian follicle formation in rats. Measurements of plasma E2, estrone and their sulfate conjugates after E2 exposure showed that neonatal female rats rapidly acquire the capability to metabolize and clear excessive E2 levels. Concomitant modifications to the mRNA content of genes encoding selected E2 metabolism enzymes in the liver and the ovary in response to E2 exposure indicate that E2 may modify the neonatal maturation of these organs. In the liver, E2 treatment was associated with lower acquisition of the capability to metabolize E2. In the ovary, E2 depleted the oocyte pool in a dose dependent manner by PND3. In 10 µg/day E2-treated ovaries, apoptotic oocytes were observed in newly formed follicles in addition to areas of ovarian cord remodeling. At PND6, follicles without any visible oocyte were present and multi-oocyte follicles were not observed. Our study reveals a major species-difference. Indeed, neonatal exposure to E2 depletes the oocyte pool in the rat ovary, whereas in the mouse it is well known to increase oocyte survival.     

TGF-beta1 Does Not Induce Senescence of Multipotent Mesenchymal Stromal Cells and Has Similar Effects in Early and Late Passages

Transforming growth factor-beta 1 (TGF-β1) stimulates a broad range of effects which are cell type dependent, and it has been suggested to induce cellular senescence. On the other hand, long-term culture of multipotent mesenchymal stromal cells (MSCs) has a major impact on their cellular physiology and therefore it is well conceivable that the molecular events triggered by TGF-β1 differ considerably in cells of early and late passages. In this study, we analyzed the effect of TGF-β1 on and during replicative senescence of MSCs. Stimulation with TGF-β1 enhanced proliferation, induced a network like growth pattern and impaired adipogenic and osteogenic differentiation. TGF-β1 did not induce premature senescence. However, due to increased proliferation rates the cells reached replicative senescence earlier than untreated controls. This was also evident, when we analyzed senescence-associated DNA-methylation changes. Gene expression profiles of MSCs differed considerably at relatively early (P 3 - 5) and later passages (P 10). Nonetheless, relative gene expression differences provoked by TGF-β1 at individual time points or in a time course dependent manner (stimulation for 0, 1, 4 and 12 h) were very similar in MSCs of early and late passage. These results support the notion that TGF-β1 has major impact on MSC function, but it does not induce senescence and has similar molecular effects during culture expansion.     

Identifying MicroRNAs Involved in Degeneration of the Organ of Corti during Age-Related Hearing Loss

MicroRNAs (miRNAs), a class of short non-coding RNAs that regulate the expression of mRNA targets, are important regulators of cellular senescence and aging. We questioned which miRNAs are involved in age-related degeneration of the organ of Corti (OC), the auditory sensory epithelium that transduces mechanical stimuli to electrical activity in the inner ear. Degeneration of the OC is generally accepted as the main cause of age-related hearing loss (ARHL), a progressive loss of hearing in individuals as they grow older. To determine which miRNAs are involved in the onset and progression of ARHL, miRNA gene expression in the OC of two mouse strains, C57BL/6J and CBA/J, was compared at three different ages using GeneChip miRNA microarray and was validated by real-time PCR. We showed that 111 and 71 miRNAs exhibited differential expression in the C57 and CBA mice, respectively, and that downregulated miRNAs substantially outnumbered upregulated miRNAs during aging. miRNAs that had approximately 2-fold upregulation included members of miR-29 family and miR-34 family, which are known regulators of pro-apoptotic pathways. In contrast, miRNAs that were downregulated by about 2-fold were members of the miR-181 family and miR-183 family, which are known to be important for proliferation and differentiation, respectively. The shift of miRNA expression favoring apoptosis occurred earlier than detectable hearing threshold elevation and hair cell loss. Our study suggests that changes in miRNA expression precede morphological and functional changes, and that upregulation of pro-apoptotic miRNAs and downregulation of miRNAs promoting proliferation and differentiation are both involved in age-related degeneration of the OC.