An epigenome-wide association study of posttraumatic stress disorder in US veterans implicates several new DNA methylation loci

Background Previous studies using candidate gene and genome-wide approaches have identified epigenetic changes in DNA methylation (DNAm) associated with posttraumatic stress disorder (PTSD). Methods In this study, we performed an EWAS of PTSD in a cohort of Veterans (n = 378 lifetime PTSD cases and 135 controls) from the Translational Research Center for TBI and Stress Disorders (TRACTS) cohort assessed using the Illumina EPIC Methylation BeadChip which assesses DNAm at more than 850,000 sites throughout the genome. Our model included covariates for ancestry, cell heterogeneity, sex, age, and a smoking score based on DNAm at 39 smoking-associated CpGs. We also examined in EPIC-based DNAm data generated from pre-frontal cortex (PFC) tissue from the National PTSD Brain Bank (n = 72). Results The analysis of blood samples yielded one genome-wide significant association with PTSD at cg19534438 in the gene G0S2 (p = 1.19 x 10(-7), p(adj) = 0.048). This association was replicated in an independent PGC-PTSD-EWAS consortium meta-analysis of military cohorts (p = 0.0024). We also observed association with the smoking-related locus cg05575921 in AHRR despite inclusion of a methylation-based smoking score covariate (p = 9.16 x 10(-6)), which replicates a previously observed PGC-PTSD-EWAS association (Smith et al. 2019), and yields evidence consistent with a smoking-independent effect. The top 100 EWAS loci were then examined in the PFC data. One of the blood-based PTSD loci, cg04130728 in CHST11, which was in the top 10 loci in blood, but which was not genome-wide significant, was significantly associated with PTSD in brain tissue (in blood p = 1.19 x 10(-5), p(adj) = 0.60, in brain, p = 0.00032 with the same direction of effect). Gene set enrichment analysis of the top 500 EWAS loci yielded several significant overlapping GO terms involved in pathogen response, including "Response to lipopolysaccharide" (p = 6.97 x 10(-6), p(adj) = 0.042). Conclusions The cross replication observed in independent cohorts is evidence that DNA methylation in peripheral tissue can yield consistent and replicable PTSD associations, and our results also suggest that that some PTSD associations observed in peripheral tissue may mirror associations in the brain.Stress-related psychiatric disorders across the life spa

Translational challenges in bone tissue engineering

The research performed for this thesis focused at strategies to improve bone graft substitutes for future clinical applicability. We started by investigating the value of cell based tissue engineered constructs. First we showed that at the ectopic location, bone formation was only present when BLI signal was present until the end of the implantation period, indicating that living MSCs were necessary for bone formation. By immunohistochemistry we showed, that the implanted MSCs were present in the newly formed bone as bone cell. For the spinal fusion location the question whether the implanted MSCs contribute to the bone regeneration remained unanswered. Next, we created hybrid constructs by using allogeneic MSCs as off-the-shelf components, and showed their effectivity in goat models both at the ectopic as well as the orthotopic location. Before allogeneic MSCs can be used in clinical practice further studies need to be performed to analyze safety in man. In other studies performed in goats we found that location has great influence on the effectiveness of MSCs. They show an additive value in enhancing bone formation at the ectopic location, e.g. in rats, but at the orthotopic location this beneficial effect is only present during the first few weeks, and not after implantation of 3-4 months. From this we can conclude that MSC seeding is not necessary for bone formation at clinically relevant orthotopic locations. Furthermore, early EPCs were coseeded with MSC to stimulate vasculogenesis, which is a prerequisite for osteogenesis. We found that in spite of the positive effect that both cell types (MSCs and EPCs) exerted on proliferation of the other in vitro, co-seeding of MSCs and EPCs did not improve bone formation. Bone-marrow-derived EPCs alone did reveal enhanced bone formation as compared to control implants without cells. The second aspect of this thesis emphasized on construct optimization, involving material improvement and investigation of bioactives. PLG, containing growth factors, was used in three studies in combination with (allogeneic) MSCs and EPCs to enhance bone formation. Results were highly variable, which was also reported in animal and human studies in the literature, making PLG in our current opinion an unreliable component for bone tissue engineering purposes. Next, the value of timing of sequentially released BMP-2 and VEGF was analyzed at ectopic and orthotopic sites in dogs. A positive effect of growth factors on bone formation was seen at both locations, which is in agreement with reports from literature. With respect to timing of the growth factors, we were the first to show that a differential timing of dual VEGF and BMP-2 delivery did not influence orthotopic bone regeneration, whereas at the ectopic site early release of BMP-2 significantly enhanced bone formation. Finally we performed an instrumented posterolateral fusion, using a new TCP, and demonstrated that the cell-free TCP constructs and MSC-seeded TCP implants performed not different from autograft, implying a future role for osteoinductive materials such as the TCP for spinal fusion. From preclinical studies we conclude that cell seeding is almost never needed in bone regeneration

No added value of 2-year radiographic follow-up of fusion surgery for adolescent idiopathic scoliosis.

PURPOSE: For fusion surgery in adolescent idiopathic scoliosis (AIS) consensus exists that a 2-year radiographic follow-up assessment is needed. This standard lacks empirical evidence. The purpose of this study was to investigate the radiographic follow-up after corrective surgery in AIS, from pre-until 2 years postoperative. METHODS: In this historical cohort study, 63 patients surgically treated for AIS, age ≤ 25 years, with 2-year radiographic follow-up, were enrolled. The primary outcome measure was the major Cobb angle. Secondary outcomes were coronal and sagittal spino-pelvic parameters, including proximal junction kyphosis (PJK) and distal adding-on. Change over time was analyzed using a repeated measures ANOVA. RESULTS: The major curve Cobb angle showed a statistically significant change for pre- to 1 year postoperative, but not for 1- to 2-year follow-up. Seven out of 63 patients did show a change exceeding the error of measurement (5°) from 1- to 2-year follow-up (range -8° to +7°), of whom 2 patients showed curve progression and 5 showed improvement. PJK or distal adding-on was not observed. CONCLUSIONS: No statistically significant changes in major curve Cobb angle were found during postsurgical follow-up, or in adjacent non-fused segments. The findings of this study are not supportive for routine radiographs 2 years after fusion surgery in AIS patients

Synaptic assembly of the brain in the absence of neurotransmitter secretion

Brain function requires precisely orchestrated connectivity between neurons. Establishment of these connections is believed to require signals secreted from outgrowing axons, followed by synapse formation between selected neurons. Deletion of a single protein, Munc18-1, in mice leads to a complete loss of neurotransmitter secretion from synaptic vesicles throughout development. However, this does not prevent normal brain assembly, including formation of layered structures, fiber pathways, and morphologically defined synapses. After assembly is completed, neurons undergo apoptosis, leading to widespread neurodegeneration. Thus, synaptic connectivity does not depend on neurotransmitter secretion, but its maintenance does. Neurotransmitter secretion probably functions to validate already established synaptic connections