Pathology | EPFL Graph Search

Pathology is the study of the causes and effects of disease or injury. The word pathology also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatment, the term is often used in a narrower fashion to refer to processes and tests that fall within the contemporary medical field of "general pathology", an area which includes a number of distinct but inter-related medical specialties that diagnose disease, mostly through analysis of tissue and human cell samples. Idiomatically, "a pathology" may also refer to the predicted or actual progression of particular diseases (as in the statement "the many different forms of cancer have diverse pathologies", in which case a more proper choice of word would be "pathophysiologies"), and the affix pathy is sometimes used to indicate a state of disease in cases of both physical ailment (as in cardiomyopathy) and psychological co

Capturing the heterogeneity of alpha-synuclein pathology in synucleinopathies

Melek Firat Altay

Synucleinopathies such as Parkinson's disease, dementia with Lewy bodies and multiple system atrophy (MSA) are detrimental neurodegenerative diseases. Alpha-synuclein (aSyn), the main aggregating protein found in the pathological inclusions of these ailments, exists in numerous modified forms and conformations, leading to neuropathological heterogeneity in synucleinopathies. The functional, pathological and clinical implications of this heterogeneity remain unclear. Responding this knowledge gap requires the development of novel toolsets capable of capturing the biochemical and structural diversity of aSyn pathology in the brain and peripheral tissues.To address this challenge, we describe in Chapter 2 the development and characterisation of antibodies that cover all three regions and post-translational modifications (PTMs) of aSyn. We assess these antibodies through a comprehensive validation pipeline, and select the best performing antibody subset to capture the neuropathological diversity of aSyn across Lewy body diseases (LBDs). We demonstrate that these antibodies could be used to achieve an in-depth characterization of the biochemical and morphological diversity of aSyn aggregates in the neuronal and in vivo models of aSyn seeding. Our results suggest that aSyn pathology is rich in Serine 129 phosphorylation (pS129) and in previously under-described PTMs, including nitration and phosphorylation at Tyrosine 39 (nY39, pY39) and C-terminal tyrosine phosphorylations (pY133, pY136) across neuronal and glial populations in LBDs. We also report that aSyn is hyperphosphorylated in the cellular and in vivo seeding models. In Chapter 3, we demonstrate the power of our antibodies to achieve an unprecedented analysis of astrocytic aSyn pathology in LBDs. We characterise the biochemical properties, post-translational modifications and the aggregation state of astrocytic aSyn accumulations in the limbic regions across sporadic and familial LBDs. The astrocytic aSyn is revealed distinctively by antibodies against the late amino-terminus (N-terminus) and non-amyloid-beta component (NAC) region of aSyn, but not by the extreme N-terminal or carboxy-terminal (C-terminal) antibodies, suggesting that these aSyn species are truncated at both ends. The astrocytic aSyn accumulations are negative for the key markers of Lewy bodies (aSyn pS129, Amytracker, p62- and ubiquitin-positivity and proteinase K resistance), and positive for aSyn nY39 and pY39. These findings suggest that the astrocytic accumulations may be composed of non-fibrillar, possibly oligomeric conformers of aSyn. Chapter 4 focuses on deciphering the biochemical and morphological signatures of aSyn pathology in MSA. The antibodies described in Chapter 2 are applied to high and low pathology regions of MSA brains by immunohistochemistry (IHC). We also biochemically profile the aSyn species, and report an abundance of aSyn pS129-positive glial and neuronal inclusions that correspond to insoluble high molecular weight species by Western blot. We detect an enrichment of insoluble and truncated aSyn in the MSA cerebellum. By IHC, there is an enhancement of aSyn nY39, pY136 and of other aSyn PTMs.Collectively, the new tools and findings described here may pave the way for future studies elucidating the role of these neuronal and glial aSyn proteoforms in disease pathogenesis and propagation in synucleinopathies.

EPFL2022

Opportunities and challenges of alpha-synuclein as a potential biomarker for Parkinson's disease and other synucleinopathies

Hilal Lashuel, Pedro José Santana Ribeiro Magalhães

Parkinson's disease (PD), the second most common progressive neurodegenerative disease, develops and progresses for 10-15 years before the clinical diagnostic symptoms of the disease are manifested. Furthermore, several aspects of PD pathology overlap with other neurodegenerative diseases (NDDs) linked to alpha-synuclein (aSyn) aggregation, also called synucleinopathies. Therefore, there is an urgent need to discover and validate early diagnostic and prognostic markers that reflect disease pathophysiology, progression, severity, and potential differences in disease mechanisms between PD and other NDDs. The close association between aSyn and the development of pathology in synucleinopathies, along with the identification of aSyn species in biological fluids, has led to increasing interest in aSyn species as potential biomarkers for early diagnosis of PD and differentiate it from other synucleinopathies. In this review, we (1) provide an overview of the progress toward mapping the distribution of aSyn species in the brain, peripheral tissues, and biological fluids; (2) present comparative and critical analysis of previous studies that measured total aSyn as well as other species such as modified and aggregated forms of aSyn in different biological fluids; and (3) highlight conceptual and technical gaps and challenges that could hinder the development and validation of reliable aSyn biomarkers; and (4) outline a series of recommendations to address these challenges. Finally, we propose a combined biomarker approach based on integrating biochemical, aggregation and structure features of aSyn, in addition to other biomarkers of neurodegeneration. We believe that capturing the diversity of aSyn species is essential to develop robust assays and diagnostics for early detection, patient stratification, monitoring of disease progression, and differentiation between synucleinopathies. This could transform clinical trial design and implementation, accelerate the development of new therapies, and improve clinical decisions and treatment strategies.

NATURE PORTFOLIO2022

Bioengineering human bone marrow models to elucidate the triggers of the stem cell niche

Queralt Vallmajó Martín

The bone marrow (BM) microenvironment, or niche, significantly affects behaviors of its resident stem cell populations. Disruptions in the BM niche contribute to a number of severe clinical pathologies. Discovery of novel therapeutic strategies for BM-related diseases necessitates development of superior preclinical models to study parameters affecting BM homeostasis. To address this, a poly(ethylene glycol) hydrogel featuring a particular crosslinking chemistry based on the enzyme transglutaminase factor XIII, dubbed TG-PEG, was utilized to engineer humanized bone marrow models. Its modular nature was exploited throughout this work to systematically evaluate contributions of biophysical, cellular, and biochemical BM niche components to stem cell biology. Stiffness of TG-PEG hydrogels was optimized for each cell type and individual application explored. For bone formation by bone marrow stromal cells (BMSCs), an intermediate stiffness was optimal and significantly improved total bone volume over softer TG-PEG gels or natural materials. Results indicated that stability of the scaffold was more important than their chemical and biological properties. Alternatively, for hematopoietic stem and progenitor cells (HSPCs), softer gels were optimal for preserving multipotency while promoting cell proliferation. A number of BM-specific stem and progenitor cell types with richly diverse functions were explored. Skeletal stem cells (SSCs) encapsulated in TG-PEG hydrogels demonstrated their ability to form de novo bone in healing critically sized calvaria defects in mice. Next, subcutaneous implantation of BMSC-laden gels revealed their significant contribution to formation of ossicles. For some BMSC donors, ossicles could be formed in absence of bone morphogenetic protein (BMP)-2 offering a novel tool to evaluate their intrinsic capacity. Later, titration of BMSC seeding densities and BMP-2 doses yielded optimal conditions for robust BM formation, regardless of donor, enabling reproducibility for follow-on studies involving BM models. In humanized mice, homing of HSPCs to BMSC-laden TG-PEG gels was observed. Finally, humanized xenograft models were employed to determine vulnerability of the BM niche to subversion by cancer cells simulating osteotropism for both leukemia and breast cancer metastasis. Molecular factors known to trigger particular cell reactions within the niche were also investigated. Including RGD cell-adhesion ligands, as well as matrix metalloproteinase (MMP)-susceptible crosslinks to render the gels degradable, were critical for facilitating migration of recruited BM cells from murine hosts in xenograft studies. Hyaluronic acid (HA), when added to the hydrogel backbone, conferred superior engraftment to transplanted BMSCs and afforded reduced immunogenicity. Incorporation of the Notch-signaling ligands Jagged1 or DLL-4 into soft TG-PEG gels during in vitro HSPC expansion substantially stimulated proliferation, but recovered cells could no longer ensure long-term reconstitution. Aging, trauma, or cancer can cause disruptions of the tightly controlled balance between cells and their microenvironment in the BM niche. This body of work presents a number of bioengineered tools optimized for studying how niche components are affected by or contribute to such pathologies. Further work with these or similar models will no doubt highlight key clinically relevant targets and inform novel therapeutic approaches.

EPFL2019