Modeling the Interplay Between Neurons and Astrocytes in Autism Using Human Induced Pluripotent Stem Cells.

BACKGROUND: Autism spectrum disorder (ASD) is a neurodevelopmental disorder with unclear etiology and imprecise genetic causes. The main goal of this work was to investigate neuronal connectivity and the interplay between neurons and astrocytes from individuals with nonsyndromic ASD using induced pluripotent stem cells. METHODS: Induced pluripotent stem cells were derived from a clinically well-characterized cohort of three individuals with nonsyndromic ASD sharing common behaviors and three control subjects, two clones each. We generated mixed neural cultures analyzing synaptogenesis and neuronal activity using a multielectrode array platform. Furthermore, using an enriched astrocyte population, we investigated their role in neuronal maintenance. RESULTS: ASD-derived neurons had a significant decrease in synaptic gene expression and protein levels, glutamate neurotransmitter release, and, consequently, reduced spontaneous firing rate. Based on co-culture experiments, we observed that ASD-derived astrocytes interfered with proper neuronal development. In contrast, control-derived astrocytes rescued the morphological neuronal phenotype and synaptogenesis defects from ASD neuronal co-cultures. Furthermore, after identifying interleukin-6 secretion from astrocytes in individuals with ASD as a possible culprit for neural defects, we were able to increase synaptogenesis by blocking interleukin-6 levels. CONCLUSIONS: Our findings reveal the contribution of astrocytes to neuronal phenotype and confirm previous studies linking interleukin-6 and autism, suggesting potential novel therapeutic pathways for a subtype of individuals with ASD. This is the first report demonstrating that glial dysfunctions could contribute to nonsyndromic autism pathophysiology using induced pluripotent stem cells modeling disease technology.

XPC deficiency is related to APE1 and OGG1 expression and function.

Oxidative DNA damage is considered to be a major cause of neurodegeneration and internal tumors observed in syndromes that result from nucleotide excision repair (NER) deficiencies, such as Xeroderma Pigmentosum (XP) and Cockayne Syndrome (CS). Recent evidence has shown that NER aids in removing oxidized DNA damage and may interact with base excision repair (BER) enzymes. Here, we investigated APE1 and OGG1 expression, localization and activity after oxidative stress in XPC-deficient cells. The endogenous APE1 and OGG1 mRNA levels were lower in XPC-deficient fibroblasts. However, XPC-deficient cells did not show hypersensitivity to oxidative stress compared with NER-proficient cells. To confirm the impact of an XPC deficiency in regulating APE1 and OGG1 expression and activity, we established an XPC-complemented cell line. Although the XPC complementation was only partial and transient, the transfected cells exhibited greater OGG1 expression and activity compared with XPC-deficient cells. However, the APE1 expression and activity did not significantly change. Furthermore, we observed a physical interaction between the XPC and APE1 proteins. Together, the results indicate that the responses of XPC-deficient cells under oxidative stress may not only be associated with NER deficiency per se but may also include new XPC functions in regulating BER proteins.

Treadmill exercise induces age-related changes in aversive memory, neuroinflammatory and epigenetic processes in the rat hippocampus.

It has been described that exercise can modulate both inflammatory response and epigenetic modifications, although the effect of exercise on these parameters during the normal brain aging process yet remains poorly understood. Here, we investigated the effect of aging and treadmill exercise on inflammatory and epigenetic parameters specifically pro and anti-inflammatory cytokines levels, activation of NF-kB and histone H4 acetylation levels in hippocampus from Wistar rats. Additionally, we evaluated aversive memory through inhibitory avoidance task. Rats of 3 and 20 months of age were assigned to non-exercised (sedentary) and exercised (running daily for 20 min for 2 weeks) groups. The effect of daily forced exercise in the treadmill was assessed. The levels of inflammatory and epigenetic parameters were determined 1h, 18 h, 3 days or 7 days after the last training session of exercise. It was observed an age-related decline on aversive memory, as well as aged rats showed increased hippocampal levels of inflammatory markers, such as TNFα, IL1-ß and NF-kB and decreased IL-4 levels, an anti-inflammatory cytokine. Moreover, lower levels of global histone H4 acetylation were also observed in hippocampi from aged rats. Interestingly, there was a significant correlation between the biochemical markers and the inhibitory avoidance test performance. The forced exercise protocol ameliorated aging-related memory decline, decreased pro-inflammatory markers and increased histone H4 acetylation levels in hippocampi 20-months-old rats, while increased acutely IL-4 levels in hippocampi from young adult rats. Together, these results suggest that an imbalance of inflammatory markers might be involved to the aging-related aversive memory impairment. Additionally, our exercise protocol may reverse aging-related memory decline through improving cytokine profile.

A quantitative proteomic and transcriptomic comparison of human mesenchymal stem cells from bone marrow and umbilical cord vein.

Human mesenchymal stem cells (hMSCs) are adult multipotent cells that have high therapeutic potential due to their immunological properties. They can be isolated from several different tissues with bone marrow (BM) being the most common source. Because the isolation procedure is invasive, other tissues such as human umbilical cord vein (UCV) have been considered. However, their interchangeability remains unclear. In the present study, total protein extracts of BM-hMSCs and UCV-hMSCs were quantitatively compared using gel-LC-MS/MS. Previous SAGE analysis of the same cells was re-annotated to enable comparison and combination of these two data sets. We observed a more than 63% correlation between proteomic and transcriptomic data. In silico analysis of highly expressed genes in cells of both origins suggests that they can be modulated by microRNA, which can change protein abundance. Our results showed that MSCs from both tissues shared high similarity in metabolic and functional processes relevant to their therapeutic potential, especially in the immune system process, response to stimuli, and processes related to the delivery of the hMSCs to a given tissue, such as migration and adhesion. Hence, our results support the idea that the more accessible UCV could be a potentially less invasive source of MSCs.

Autophagy in stem cell maintenance and differentiation.

Autophagy is a lysosome-dependent degradation pathway that allows cells to recycle damaged or superfluous cytoplasmic content, such as proteins, organelles, and lipids. As a consequence of autophagy, the cells generate metabolic precursors for macromolecular biosynthesis or ATP generation. Deficiencies in this pathway were associated to several pathological conditions, such as neurodegenerative and cardiac diseases, cancer, and aging. The aim of this review is to summarize recent discoveries showing that autophagy also plays a critical role in stem cell maintenance and in a variety of cell differentiation processes. We also discuss a possible role for autophagy during cellular reprogramming and induced pluripotent stem (iPS) cell generation by taking advantage of ATP generation for chromatin remodeling enzyme activity and mitophagy. Finally, the significance of autophagy modulation is discussed in terms of augmenting efficiency of iPS cell generation and differentiation processes.

Células-tronco pluripotentes e doenças neurológicas / Pluripotent stem cells and neurological diseases

Grande parte do conhecimento atual dos fenótipos celulares relacionados a doenças neurológicas foi obtida a partir de estudos de tecidos cerebrais coletados após a morte do indivíduo. Essas amostras geralmente representam os estágios finais da doença e, portanto, não servem como fiel representação de como os sintomas aparecem. Além disso, nessas circunstâncias, a patologia observada pode muito bem ser um efeito secundário do processo patológico ou mesmo da deterioração do tecido em vez de um fenótipo celular autêntico. Da mesma forma, modelos animais nem sempre recapitulam exatamente a patologia das doenças em humanos. Neste artigo, pretendo apresentar uma visão crítica dos recentes avanços obtidos a partir da modelagem de doenças neurológicas humanas, utilizando células-tronco pluripotentes. O foco na reprogramação celular de células somáticas, gerando células-tronco pluripotentes induzidas, justifica-se em razão do grande potencial experimental não só para a modelagem de doenças humanas, mas também como ferramenta biotecnológica para triagem de novas drogas, contribuindo para uma futura medicina personalizada.

Most of our current knowledge about cellular phenotypes related to neurological diseases was gathered from studies performed in brain tissue collected postmortem. These samples often represent the end-stage of the disease process and may not represent a fair picture of how the disease developed over time. Futhermore, under these conditions, the pathology may as well be a secundary effect of the disease process or even due to the poor tissue condition and may not represent an authentic cellular phenotype. Likewise, animal models not always recapitulate the pathology from human disorders. In this article, I will present a critical view on the recent advances obtained from disease modeling using human pluripotent stem cells. The focus on cellular reprogramming as tool to generate patient-specific induced pluripotent stem cells is justified by the great experimental potential, not only for disease modeling, but also as a biotecnological tool for future drug-screening platforms and personalized medicine.

Skeletal muscle cells expressing VEGF induce capillary formation and reduce cardiac injury in rats.

BACKGROUND: We tested a preemptive combined cell/gene therapy strategy of skeletal myoblasts transfected with Ad(5)RSVVEGF-165 in an ischemia/reperfusion rat model to increase collateral blood flow to nonischemic heart tissue. METHODS: Lewis rats were injected with placebo (Control), 10(6) skeletal myoblasts (SkM), or 10(6) skeletal myoblasts transfected with Ad(5)RSVVEGF-165 (SkM(+)) into the left ventricle 1week before ischemia. Left ventricle end-diastolic pressure, scar area, and capillary density were assessed 4weeks later. RESULTS: Local expression of human vascular endothelial growth factor was accompanied by an increase in capillary density in the SkM(+) group compared with that in the SkM and Control groups (700+/-40 vs. 289+/-18 and 318+/-59capillaries/mm(2), respectively; p<0.05). After 3weeks, the myocardial scar area was reduced in SkM(+) vs. Control (5.3+/-0.4% and 14.8+/-1.6%, p<0.05), while injected cells alone (SkM) did not cause improvement compared with Control (11.8+/-2.1% vs. 14.8+/-1.6%, p>0.05). The decrease in the scar area in SkM(+) was accompanied by an increase in the capillary density compared with that in SkM and Control 30days after cell injection (1005+/-108 vs. 524+/-16 and 528+/-26capillaries/mm(2), respectively; p<0.05). The scar areas were discrete (5.3-14.8%) and left ventricle end-diastolic pressure in all groups were comparable (p>0.05). CONCLUSIONS: The combined cell/gene therapy strategy of genetically modified myoblast cells expressing angiogenic factors injected into the myocardium induced capillary formation and prevented the extension and development of cardiac damage associated with ischemia/reperfusion in rats.

Restoring DNA repair capacity of cells from three distinct diseases by XPD gene-recombinant adenovirus.

The nucleotide excision repair (NER) is one of the major human DNA repair pathways. Defects in one of the proteins that act in this system result in three distinct autosomal recessive syndromes: xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD). TFIIH is a nine-protein complex essential for NER activity, initiation of RNA polymerase II transcription and with a possible role in cell cycle regulation. XPD is part of the TFIIH complex and has a helicase function, unwinding the DNA in the 5' --> 3' direction. Mutations in the XPD gene are found in XP, TTD and XP/CS patients, the latter exhibiting both XP and CS symptoms. Correction of DNA repair defects of these cells by transducing the complementing wild-type gene is one potential strategy for helping these patients. Over the last years, adenovirus vectors have been largely used in gene delivering because of their efficient transduction, high titer, and stability. In this work, we present the construction of a recombinant adenovirus carrying the XPD gene, which is coexpressed with the EGFP reporter gene by an IRES sequence, making it easier to follow cell infection. Infection by this recombinant adenovirus grants full correction of SV40-transformed and primary skin fibroblasts obtained from XP-D, TTD and XP/CS patients.

Complementation of the DNA repair deficiency in human xeroderma pigmentosum group a and C cells by recombinant adenovirus-mediated gene transfer.

Nucleotide excision repair (NER) is one of the most versatile DNA repair mechanisms, ensuring the proper functioning and trustworthy transmission of genetic information in all living cells. The phenotypic consequences caused by NER defects in humans are autosomal recessive diseases such as xeroderma pigmentosum (XP). This syndrome is the most sun-sensitive disorder leading to a high frequency of skin cancer. The majority of patients with XP carry mutations in the XPA or XPC genes that encode proteins involved in recognition of DNA damage induced by UV light at the beginning of the NER process. Cells cultured from XPA and XPC patients are hypersensitive to UV light, as a result of malfunctioning DNA repair. So far there is no effective long-term treatment for these patients. Skin cancer prevention can only be achieved by strict avoidance of sunlight exposure or by the use of sunscreen agents. We have constructed recombinant adenoviruses carrying the XPA and XPC genes that were used to infect XP-A and XP-C immortalized and primary fibroblast cell lines. UV survival curves and unscheduled DNA synthesis confirmed complete phenotypic reversion in XP DNA repair deficient cells with no trace of cytotoxicity. Moreover, transgene expression is stable for at least 60 days after infection. This efficient adenovirus gene delivery approach may be an important tool to better understand XP deficiency and the causes of DNA damage induced skin cancer.