UBC Theses and Dissertations
Characterization of the human first trimester placental protease landscape using single-cell RNA sequencing Waechter, Jasmin
The metzincin family of metalloproteases coordinates cell and tissue developmental processes through regulation of growth factor availability, receptor signaling potential, and cell-cell/cell-matrix adhesion. During placental development, metzincin proteases are crucial for successful trophoblast differentiation and invasion. While distinct roles for metzincin proteases in controlling specific trophoblast functions have been described, a comprehensive assessment of metzincins in trophoblasts during discrete stages of differentiation has yet to be performed. In this thesis, I investigate the function of metzincin proteases in the novel human trophoblast stem cell lines with the use of the broad protease inhibitor Batimastat. I show that Batimastat leads to decreased size and invasive outgrowth of organoids cultured in regenerative and extravillous differentiation media respectively. I further undertake a comprehensive single cell transcriptomic assessment of metzincin protease expression in diverse states of human trophoblasts from 11 first trimester placentas. In the 8 distinct trophoblasts states categorized [four progenitor cytotrophoblast (CTB), one syncytiotrophoblast precursor (SCTp), two column CTB (cCTB), and one extravillous trophoblast (EVT) state], I identify 24 metzincin proteases, including 12 adamalysins, 2 pappalysins, 3 astacins and 7 matrixins. Our follow-up cell trajectory modeling shows that most (19/24) metzincins increase along the EVT pathway, though multiple proteases also increase along the villous pathway as CTB fuse into syncytiotrophoblast. Within the CTB niche, single-cell velocity ordering identifies 11 metzincin proteases (ADAM10, -17, MMP14, -15, -19, -23B, ADAMTS1, -6, -19, TLL-1, -2) expressed in progenitors proximal to the predicted origin. To elucidate factors governing CTB maintenance, I analyze metzincin-substrate interactions within the CTB niche. This reveals ~150 substrates and binding partners, including FBN2 as an ADAMTS6-specific substrate preferentially expressed in trophoblast progenitors. Lastly, I undertake a single cell RNA sequencing analysis of metzincin protease dynamics in the human trophoblast stem cell derived organoids which reveal a high degree of overlap with our in vivo dataset. Together, this work characterizes the metzincin transcriptomic landscape in human first trimester trophoblasts and establishes insight into the roles specific proteases perform within distinct trophoblast niches and during differentiation. This thesis serves as a guide for future investigations into the roles of metzincin proteases in placental development.
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