A comparative study of glial and non‐neural cell properties for transplant‐mediated repair of the injured spinal cord

Cell transplantation is one strategy for encouraging regeneration after spinal cord injury and a range of cell types have been investigated for their repair potential. However, variations in study design complicate determination of which cells are most effective. In this study we have carried out a direct comparison of the regenerative and integrative properties of several cell preparations following transplantation into the lesioned rat spinal cord. Transplants included: (i) purified olfactory ensheathing cells (OECs) and (ii) fibroblast‐like cells, from olfactory bulb (OBFB‐L), (iii) a 50:50 mixture of (i) and (ii) (OEC/OBFB‐L), (iv) dissociated nasal mucosa (OM), (v) purified peripheral nerve Schwann cells (SCs), (vi) peripheral nerve fibroblasts, and (vii) skin fibroblasts (SF). All transplants supported axonal regeneration: OECs and SCs promoted the greatest regeneration while OBFB‐like cells were least efficient and mixed cell populations were less effective than purified populations. Tract‐tracing experiments demonstrated that none of the cell types promoted regeneration beyond the lesion. Although all cell types prevented cavity formation, the extent of astrocytic hypertrophy [GFAP immunoreactivity (IR) at the transplant/lesion site] differed markedly. OECs and SCs were associated with the least GFAP‐IR, fibroblasts and fibroblast‐like cells resulted in greater GFAP‐IR while hypertrophy surrounding transplants of OM was most extensive. These differences in host‐transplant reactivity were confirmed by transplanting cells into normal spinal cord where the cellular interaction is not complicated by injury. Thus, purified glial cells have advantages for transplant‐mediated repair, combining maximal support for axonal regeneration with a minimal astrocytic reaction around the transplant site. © 2013 Wiley Periodicals, Inc.     

Galanin gene transfer curtails generalized seizures in kindled rats without altering hippocampal synaptic plasticity

Gene therapy–based overexpression of endogenous seizure-suppressing molecules represents a promising treatment strategy for epilepsy. Viral vector–based overexpression of the neuropeptide galanin has been shown to effectively suppress generalized seizures in various animal models of epilepsy. However, it has not been explored whether such treatment can also prevent the epileptogenesis. Using a recombinant adeno-associated viral (rAAV) vector, we induced hippocampal galanin overexpression under the neuron specific enolase promoter in rats. Here we report that in animals with galanin overexpression, the duration of electrographic afterdischarges was shortened and initiation of convulsions was delayed at generalized seizure stages. However, the hippocampal kindling development was unchanged. Short-term plasticity of mossy fiber–cornu ammonis (CA) 3 synapses was unaltered, as assessed by paired-pulse and frequency facilitation of field excitatory postsynaptic potentials (fEPSPs) in hippocampal slices, suggesting that despite high transgene galanin expression, overall release probability of glutamate in these synapses was unaffected. These data indicate that hippocampal rAAV-based galanin overexpression is capable of mediating anticonvulsant effects by lowering the seizure susceptibility once generalized seizures are induced, but does not seem to affect kindling development or presynaptic short-term plasticity in mossy fibers.     

ERG Protein Expression in Diagnostic Specimens Is Associated with Increased Risk of Progression During Active Surveillance for Prostate Cancer

Background

Compelling biomarkers identifying prostate cancer patients with a high risk of progression during active surveillance (AS) are needed.

Objective

To examine the association between ERG expression at diagnosis and the risk of progression during AS.

Design, setting, and participants

This study included 265 patients followed on AS with prostate-specific antigen (PSA) measurements, clinical examinations, and 10–12 core rebiopsies from 2002 to 2012 in a prospectively maintained database. ERG immunohistochemical staining was performed on diagnostic paraffin-embedded formalin-fixed sections with a ready-to-use kit (anti-ERG, EPR3864). Men were characterised as ERG positive if a minimum of one tumour focus demonstrated ERG expression.

Outcome measurements and statistical analysis

Overall AS progression was defined as clinical progression: increased clinical tumour category ≥cT2b by digital rectal examination and ultrasound, and/or histopathologic progression: upgrade of Gleason score, more than three positive cores or bilateral positive cores, and/or PSA progression: PSA doubling time <3 yr. Risk of progression was analysed using multiple cause-specific Cox regression and stratified cumulative incidences (Aalen-Johansen method). Curatively intended treatment, watchful waiting, and death without progression were treated as competing events.

Results and limitations

A total of 121 of 142 ERG-negative and 96 of 123 ERG-positive patients had complete diagnostic information. In competing risk models, the ERG-positive group showed significantly higher incidences of overall AS progression (p < 0.0001) and of the subgroups PSA progression (p < 0.0001) and histopathologic progression (p < 0.0001). The 2-yr cumulative incidence of overall AS progression was 21.7% (95% confidence interval [CI], 14.3–29.1) in the ERG-negative group compared with 58.6% (95% CI, 48.7–68.5) in the ERG-positive group. ERG positivity was a significant predictor of overall AS progression in multiple Cox regression (hazard ratio: 2.45; 95% CI, 1.62–3.72; p < 0.0001). The main limitation of this study is its observational nature.

Conclusions

In our study, ERG positivity at diagnosis can be used to estimate the risk of progression during AS. If confirmed, ERG status can be used to individualise AS programmes.

Patient summary

The tissue biomarker ERG identifies active surveillance patients with an increased risk of disease progression.     

Bedside Diagnosis of Mitochondrial Dysfunction After Malignant Middle Cerebral Artery Infarction

Background

The study explores whether the cerebral biochemical pattern in patients treated with hemicraniectomy after large middle cerebral artery infarcts reflects ongoing ischemia or non-ischemic mitochondrial dysfunction.

Methods

The study includes 44 patients treated with decompressive hemicraniectomy (DCH) due to malignant middle cerebral artery infarctions. Chemical variables related to energy metabolism obtained by microdialysis were analyzed in the infarcted tissue and in the contralateral hemisphere from the time of DCH until 96 h after DCH.

Results

Reperfusion of the infarcted tissue was documented in a previous report. Cerebral lactate/pyruvate ratio (L/P) and lactate were significantly elevated in the infarcted tissue compared to the non-infarcted hemisphere (p < 0.05). From 12 to 96 h after DCH the pyruvate level was significantly higher in the infarcted tissue than in the non-infarcted hemisphere (p < 0.05).

Conclusion

After a prolonged period of ischemia and subsequent reperfusion, cerebral tissue shows signs of protracted mitochondrial dysfunction, characterized by a marked increase in cerebral lactate level with a normal or increased cerebral pyruvate level resulting in an increased LP-ratio. This biochemical pattern contrasts to cerebral ischemia, which is characterized by a marked decrease in cerebral pyruvate. The study supports the hypothesis that it is possible to diagnose cerebral mitochondrial dysfunction and to separate it from cerebral ischemia by microdialysis and bed-side biochemical analysis.     

Adult height and risk of ischemic heart disease,atrial fibrillation,stroke, venous thromboembolism,and premature death: a population based 36-year follow-up study

Few studies have associated height with cardiovascular diseases other than myocardial infarction. We conducted a population-based 36-year cohort study of 12,859 men born in 1955 or 1965 whose fitness for military service was assessed by Draft Boards in Northern Denmark. Hospital diagnoses for ischemic heart diseases, atrial fibrillation, stroke, and venous thromboembolism were obtained from the Danish National Patient Registry, covering all Danish hospitals since 1977. Mortality data were obtained from the Danish Civil Registration System. We began follow-up on the 22nd birthday of each subject and continued until occurrence of an outcome, emigration, death, or 31 December 2012, whichever came first. We used Cox regression to compute hazard ratios (HRs) with 95 % confidence intervals (CIs). Compared with short stature, the education-adjusted HR among tall men was 0.67 (95 % CI 0.54–0.84) for ischemic heart disease (similar for myocardial infarction, angina pectoris, and heart failure), 1.60 (95 % CI 1.11–2.33) for atrial fibrillation, 1.05 (95 % CI 0.75–1.46) for stroke, 1.04 (95 % CI 0.67–1.64) for venous thromboembolism, and 0.70 (95 % CI 0.58–0.86) for death. In conclusion, short stature was a risk factor for ischemic heart disease and premature death, but a protective factor for atrial fibrillation. Stature was not substantially associated with stroke or venous thromboembolism.     

Preservation of genetic and regulatory robustness in ancient gene duplicates of Saccharomyces cerevisiae

Biological systems remain robust against certain genetic and environmental challenges. Robustness allows the exploration of ecological adaptations. It is unclear what factors contribute to increasing robustness. Gene duplication has been considered to increase genetic robustness through functional redundancy, accelerating the evolution of novel functions. However, recent findings have questioned the link between duplication and robustness. In particular, it remains elusive whether ancient duplicates still bear potential for innovation through preserved redundancy and robustness. Here we have investigated this question by evolving the yeast Saccharomyces cerevisiae for 2200 generations under conditions allowing the accumulation of deleterious mutations, and we put mechanisms of mutational robustness to a test. S. cerevisiae declined in fitness along the evolution experiment, but this decline decelerated in later passages, suggesting functional compensation of mutated genes. We resequenced 28 genomes from experimentally evolved S. cerevisiae lines and found more mutations in duplicates—mainly small-scale duplicates—than in singletons. Genetically interacting duplicates evolved similarly and fixed more amino acid–replacing mutations than expected. Regulatory robustness of the duplicates was supported by a larger enrichment for mutations at the promoters of duplicates than at those of singletons. Analyses of yeast gene expression conditions showed a larger variation in the duplicates’ expression than that of singletons under a range of stress conditions, sparking the idea that regulatory robustness allowed a wider range of phenotypic responses to environmental stresses, hence faster adaptations. Our data support the persistence of genetic and regulatory robustness in ancient duplicates and its role in adaptations to stresses.Biological systems are inherently robust to perturbations, maintaining the same phenotypes in the face of environmental and genetic challenges (Gu et al. 2003; Stelling et al. 2004; Wagner 2005b). Robustness is key to the emergence of biological complexity and diversification as more robust systems can explore a larger set of phenotypes, allowing greater potential for evolving novel adaptations (Draghi et al. 2010; Payne and Wagner 2014). Determining the factors that provide systems with robustness would pave the way for a more complete understanding of the origin of adaptations and biological complexity. However, despite major efforts in understanding robustness (Wagner 2012), the factors that increase robustness of biological systems and their characterization remain to be determined.Gene duplication has been considered to have a major role in genetic robustness (Lynch and Conery 2000), as the presence of two copies performing identical or overlapping functions confers immunity to the deleterious effects of mutations occurring in one of the gene copies. Additionally, gene duplication has been credited with great importance in generating evolutionary novelties (Ohno 1999) because the selection-free exploration of the genotype space, due to genetic redundancy, allows one gene copy to probe a wider range of phenotypes (Payne and Wagner 2014). Arguably, gene duplication provides an invaluable opportunity to explore the link between genetic robustness and evolvability. Indeed, a number of studies have shown that major gene duplication events, such as whole-genome duplication (WGD) in angiosperms (Wendel 2000; Blanc and Wolfe 2004a) and animals (Otto and Whitton 2000; Hoegg et al. 2004), are concomitant with the emergence of morphological, metabolic, and physiological innovations (Otto and Whitton 2000; Holub 2001; Lespinet et al. 2002; Hoegg et al. 2004; Kim et al. 2004; Maere et al. 2005).Despite the apparent causal link between gene duplication and evolutionary innovation, the neutral exploration of genotype space by a duplicated gene requires the persistence of both gene copies for long periods. This clashes with the evolutionary instability of genetic redundancy, illustrated by the fact that 92% of duplicates in Saccharomyces cerevisiae, originated through WGD roughly 100 million years ago (Mya) (Wolfe and Shields 1997), have returned to single gene copies in extant S. cerevisiae. The rate of preservation of genes in duplicate varies, however, among organisms, with some exhibiting up to 30% of their genes in duplicate (Blanc and Wolfe 2004b; Cui et al. 2006). Genetic robustness, along with other factors such as selection for increasing gene dosage (Conant and Wolfe 2008) and gene balance (Birchler et al. 2005; Freeling and Thomas 2006), has been proposed to allow the persistence of genes in duplicate for longer periods of time, thereby providing opportunity for innovation through mutation (Gu et al. 2003; Fares et al. 2013). This claim is supported by larger fitness effects associated with the deletion of singletons compared to duplicates in yeast (Gu et al. 2003), functional compensation of deleted gene copies (VanderSluis et al. 2010), higher robustness of duplicates to transient gene knockdowns in Caenorhabditis elegans (Conant and Wagner 2004), and the contribution of gene duplicates to provide functional back-up against deleterious human mutations (Hsiao and Vitkup 2008). Recent studies have challenged, however, the link between gene duplication and genetic robustness, revealing a more complex relationship between duplicate preservation, genetic redundancy, and robustness. For example, using synthetic lethality genetic maps, Ihmels et al. (2007) found that duplicates, although exhibiting functional compensation, account for only 25% of the mutational robustness of a system. Furthermore, Wagner (2000) analyzed a number of duplicated genes and found no evidence of compensatory effects for null mutations between gene copies with high sequence or expression similarities. Moreover, a recent study has shown that in natural populations of yeast, close duplicates are unlikely to provide substantial functional compensation (Plata and Vitkup 2013). Thus, it is unresolved whether gene duplication provides mutational robustness through genetic redundancy. Since genetic redundancy and robustness are directly linked to evolvability, finding whether or not gene duplication provides sufficient genetic robustness to overcome the energetic and metabolic cost of maintaining additional genetic material is crucial to link gene duplication with the evolution of novel traits. Also, finding appreciable genetic redundancy between the copies of ancient duplicates would support their potential for future biological innovations.The studies conducted so far to probe the link between gene duplication, genetic redundancy, and mutational robustness have been obscured by the complex mixture of the genomic signatures of natural selection and genetic drift. These mixed signatures make it difficult to disentangle the role of genetic redundancy and mutational robustness in the emergence of novel functions from that of selection favoring adaptive mutations. Moreover, most studies ignore the role of the mechanism of duplication, WGD versus small-scale duplication (SSD), in providing mutational robustness and thus opportunity for innovation (Carretero-Paulet and Fares 2012; Fares et al. 2013). It is expected that the present genetic robustness and incomplete functional compensation of today’s duplicates are the remainders of an ancient larger genetic robustness that emerged at the time of gene duplication. Owing to the functional diversification of duplicates, quantification of preserved genetic robustness is complex and requires a direct test of the robustness of current, long-term preserved duplicates to deleterious mutations. Therefore, a definitive resolution of the controversy of whether ancient gene duplicates provide genetic robustness must come from testing the impact of deleterious mutations on duplicates in comparison with singletons. In this study, we resolved the controversy by conducting an experiment that allows the accumulation of deleterious mutations in the genome of S. cerevisiae. Using experimental evolution allows disentangling adaptive mutations from deleterious and neutral mutations and testing hypotheses under tightly controlled experimental conditions, which are not possible in comparative genomics studies. We test, for the first time, whether duplicates tolerate more deleterious mutations in their coding and regulatory regions than expected under the assumption of no genetic robustness.     

Racial Differences in the Frequencies of Scleroderma-Related Autoantibodies

Objective. To determine demographic differences in scleroderma-related autoantibodies. Methods. One hundred fifty-six patients with systemic sclerosis were prospectively examined for anticentromere antibodies (ACA), anti—topoisomerase I (anti—topo I, or Scl-70), antinucleolar, and anti—U1 RNP autoantibodies. Results. ACA was found in 36% of Caucasians and 4% of American blacks (P = 0.002, odds ratio [OR] 15). Anti—topo I was found in 37% of American blacks, compared with 17% of Caucasians (P = 0.04, OR 3). No significant differences in the frequencies of antinucleolar and anti—U1 RNP autoantibodies were found. Conclusion. These data suggest important demographic differences in scleroderma-associated autoantibodies.     

Has Omicron Changed the Evolution of the Pandemic?

BackgroundVariants of the SARS-CoV-2 virus carry differential risks to public health. The Omicron (B.1.1.529) variant, first identified in Botswana on November 11, 2021, has spread globally faster than any previous variant of concern. Understanding the transmissibility of Omicron is vital in the development of public health policy.ObjectiveThe aim of this study is to compare SARS-CoV-2 outbreaks driven by Omicron to those driven by prior variants of concern in terms of both the speed and magnitude of an outbreak.MethodsWe analyzed trends in outbreaks by variant of concern with validated surveillance metrics in several southern African countries. The region offers an ideal setting for a natural experiment given that most outbreaks thus far have been driven primarily by a single variant at a time. With a daily longitudinal data set of new infections, total vaccinations, and cumulative infections in countries in sub-Saharan Africa, we estimated how the emergence of Omicron has altered the trajectory of SARS-CoV-2 outbreaks. We used the Arellano-Bond method to estimate regression coefficients from a dynamic panel model, in which new infections are a function of infections yesterday and last week. We controlled for vaccinations and prior infections in the population. To test whether Omicron has changed the average trajectory of a SARS-CoV-2 outbreak, we included an interaction between an indicator variable for the emergence of Omicron and lagged infections.ResultsThe observed Omicron outbreaks in this study reach the outbreak threshold within 5-10 days after first detection, whereas other variants of concern have taken at least 14 days and up to as many as 35 days. The Omicron outbreaks also reach peak rates of new cases that are roughly 1.5-2 times those of prior variants of concern. Dynamic panel regression estimates confirm Omicron has created a statistically significant shift in viral spread.ConclusionsThe transmissibility of Omicron is markedly higher than prior variants of concern. At the population level, the Omicron outbreaks occurred more quickly and with larger magnitude, despite substantial increases in vaccinations and prior infections, which should have otherwise reduced susceptibility to new infections. Unless public health policies are substantially altered, Omicron outbreaks in other countries are likely to occur with little warning.