Investigating contributions of trisomy 21 in Down syndrome to Alzheimer disease phenotypes in a novel mouse cross

Down syndrome (DS) is a common, complex disorder caused by having an extra copy of human chromosome 21 (trisomy 21). While clinical presentation varies extensively, Alzheimer disease (AD) pathology is found in brains of virtually all people with DS by 40 years. This increases their dementia risk such that one third of the DS population develops AD by 60 years. Therefore DS allows the investigation of pathogenetic mechanisms underlying its clear genetic form of early-onset AD. To model DS in mice, a ‘transchromosomic’ model, Tc1, was generated carrying a freely segregating copy of human chromosome 21 (Hsa21), which is trisomic for ~75% of Hsa21 genes. However, Tc1 is not functionally trisomic for APP. By crossing Tc1 with the J20 model, a transgenic mouse overexpressing mutant human APP that models amyloid deposition, it is possible to compare contributions of trisomy 21 and APP/Aβ overexpression to phenotypes in the genotypically different offspring. The work presented in this thesis therefore characterises AD-related phenotypes in progeny of the Tc1xJ20 cross. I first established a primary cortical culture model from early postnatal Tc1xJ20 pups, which would allow the in vitro observation and manipulation of cortical neurons in a more accessible system compared to in vivo study. To assess the validity and utility of these cultures, they were characterized for APP expression, Aβ production, proportion of neuronal cells in culture and levels of mosaicism for the Hsa21 chromosome. These in vitro phenotypes obtained were compared with relevant in vivo observations in Tc1xJ20 mice. Secondly, to study neuroinflammation and glial reactivity, I developed a digital analysis protocol to systematically quantify morphological characteristics of microglia and astrocytes visualized by immunohistochemistry in Tc1xJ20 brain sections. To further identify AD-related phenotypes that may be differentially influenced by genotype, I annotated data obtained from a pilot RNA sequencing study of Tc1xJ20 hippocampal tissues, identified gene candidates of interest, and explored functions that may be altered by genotype by clustering differentially expressed genes by associated functions. These results therefore allow for discussion and evaluation of the novel Tc1xJ20 model for identifying novel genetic contributions of trisomy 21 on AD phenotypes, apart from APP

Haemodynamic changes in visceral hybrid repairs of type III and type V thoracoabdominal aortic aneurysms

The visceral hybrid procedure combining retrograde visceral bypass grafting and completion endovascular stent grafting is a feasible alternative to conventional open surgical or wholly endovascular repairs of thoracoabdominal aneurysms (TAAA). However, the wide variability in visceral hybrid configurations means that a priori prediction of surgical outcome based on haemodynamic flow profiles such as velocity pattern and wall shear stress post repair remain challenging. We sought to appraise the clinical relevance of computational fluid dynamics (CFD) analyses in the setting of visceral hybrid TAAA repairs. Two patients, one with a type III and the other with a type V TAAA, underwent successful elective and emergency visceral hybrid repairs, respectively. Flow patterns and haemodynamic parameters were analysed using reconstructed pre- and post-operative CT scans. Both type III and type V TAAAs showed highly disturbed flow patterns with varying helicity values preoperatively within their respective aneurysms. Low time-averaged wall shear stress (TAWSS) and high endothelial cell action potential (ECAP) and relative residence time (RRT) associated with thrombogenic susceptibility was observed in the posterior aspect of both TAAAs preoperatively. Despite differing bypass configurations in the elective and emergency repairs, both treatment options appear to improve haemodynamic performance compared to preoperative study. However, we observed reduced TAWSS in the right iliac artery (portending a theoretical risk of future graft and possibly limb thrombosis), after the elective type III visceral hybrid repair, but not the emergency type V repair. We surmise that this difference may be attributed to the higher neo-bifurcation of the aortic stent graft in the type III as compared to the type V repair. Our results demonstrate that CFD can be used in complicated visceral hybrid repair to yield potentially actionable predictive insights with implications on surveillance and enhanced post-operative management, even in patients with complicated geometrical bypass configurations

Dissecting Alzheimer disease in Down syndrome using mouse models

Down syndrome (DS) is a common genetic condition caused by the presence of three copies of chromosome 21 (trisomy 21). This greatly increases the risk of Alzheimer disease (AD), but although virtually all people with DS have AD neuropathology by 40 years of age, not all develop dementia. To dissect the genetic contribution of trisomy 21 to DS phenotypes including those relevant to AD, a range of DS mouse models has been generated which are trisomic for chromosome segments syntenic to human chromosome 21. Here, we consider key characteristics of human AD in DS (AD-DS), and our current state of knowledge on related phenotypes in AD and DS mouse models. We go on to review important features needed in future models of AD-DS, to understand this type of dementia and so highlight pathogenic mechanisms relevant to all populations at risk of AD

Pigment epithelium-derived factor as an anticancer drug and new treatment methods following the discovery of its receptors: A patent perspective

Traditional forms of cancer therapy, which include chemotherapy, have largely been overhauled due to the significant degree of toxicity they pose to normal, otherwise healthy tissue. It is hoped that the use of biological agents, most of which are endogenously present in the body, will lead to safer treatment outcomes, without sacrificing efficacy. The finding that pigment epithelium-derived factor (PEDF), a naturally-occurring protein, is a potent angiogenesis inhibitor has become the basis for studying the role of PEDF in tumours that are highly resistant to chemotherapy. The determination of the direct role of PEDF against cancer paves the way for understanding and developing PEDF as a novel drug. This review focuses on the patent applications behind testing the anticancer therapeutic effect of PEDF via its receptors as an antiangiogenic agent and as a direct anticancer agent. The majority of the PEDF patents describe the antiangiogenic ability and usage of recombinant vectors as the mode of treatment delivery. PEDF's therapeutic potential against different diseases and the discovery of its receptors open possibilities for improving PEDF-based peptide design and drug delivery modes

Efficient and rapid generation of large genomic variants in rats and mice using CRISMERE

Modelling Down syndrome (DS) in mouse has been crucial for the understanding of the disease and the evaluation of therapeutic targets. Nevertheless, the modelling so far has been limited to the mouse and, even in this model, generating duplication of genomic regions has been labour intensive and time consuming. We developed the CRISpr MEdiated REarrangement (CRISMERE) strategy, which takes advantage of the CRISPR/Cas9 system, to generate most of the desired rearrangements from a single experiment at much lower expenses and in less than 9 months. Deletions, duplications, and inversions of genomic regions as large as 24.4 Mb in rat and mouse founders were observed and germ line transmission was confirmed for fragment as large as 3.6 Mb. Interestingly we have been able to recover duplicated regions from founders in which we only detected deletions. CRISMERE is even more powerful than anticipated it allows the scientific community to manipulate the rodent and probably other genomes in a fast and efficient manner which was not possible before