{"id":{"repo_id":"buffalo","oai_identifier":"oai:ubir.buffalo.edu:10477/86728"},"canonical_url":"https://search.dev.ndltd.org/etd/buffalo/oai:ubir.buffalo.edu:10477/86728","repository":{"repo_id":"buffalo","name":"Buffalo","base_url":"https://ubir.buffalo.edu/oai/request"},"display":{"title":"Species-Specific Regulation of Human Oligodendrocyte Precursor Cells Homeostasis","abstract":"M.S.","abstract_html":"M.S.","abstract_has_math":false,"creators":["Elhossiny, Ahmed"],"institution":"State University of New York at Buffalo","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Sim, Fraser","Genetics, Genomics and Bioinformatics"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-02-21T21:36:55Z","date_published":"2025-02-21T21:36:55Z","updated_at":"2026-07-27T19:05:34Z","subjects":["genetics","neurosciences"],"languages":["eng"],"rights":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10477/86728","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Sim, Fraser","Genetics, Genomics and Bioinformatics"]},{"key":"dc:creator","label":"Author","values":["Elhossiny, Ahmed"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-02-21T21:36:55Z","2020"]},{"key":"dc:publisher","label":"Institution","values":["State University of New York at Buffalo"]},{"key":"dc:type","label":"Dc Type","values":["Text","Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["genetics","neurosciences"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/10477/86728"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["M.S.","Oligodendrocyte precursor cells (OPCs) represent the most numerous population of stem/progenitor cells in the adult human brain. Upon activation, adult OPCs divide and generate new oligodendrocytes in response to neuronal activity and following demyelination. The molecular mechanisms that govern OPC homeostasis remain poorly defined, but in vivo imaging studies have revealed that these processes are governed by their local environment such that differentiation or death of an OPC is followed by compensatory division of a neighboring OPC. However following transplantation, human OPCs (hOPCs) continuing to divide in the presence of murine OPCs (mOPC). This suggests the presence of a species-specific signal that regulates hOPC proliferation and implicates species-mismatch as a mechanism underlying the success of xenografted OPCs for myelin repair. In order to characterize the molecular mechanisms, we developed an in vitro model in which mCherry-expressing primary hOPCs were cultured either alone or in the presence of mOPCs or hOPCs (Chapter 3). As observed following transplantation, hOPC proliferation was inhibited by coculture with hOPCs but not by mOPCs. Conversely, mOPC proliferation was halted by coculture with either species OPCs. The species-specific inhibition of proliferation was dependent on cell-cell signaling as coculture with fixed hOPCs relieved the inhibitory effect. Importantly, reduced hOPC proliferation was not associated with oligodendrocyte differentiation. This cell-cell signal exhibited cell-type specificity as coculture with human astrocytes-like cells did not substantially block hOPC proliferation. We next established that the hOPC-derived signal was likely soluble using discontinuous transwell cultures and conditioned media. Proteome analysis (LC-MS and IonStar) was utilized to identify several candidates that may mediate this inhibitory effect (Chapter 4). We identified six candidate proteins which were relatively enriched in hOPC conditioned media and predicted to be actively secreted (SignalP). To determine whether these proteins could influence hOPC proliferation, we exposed hOPCs to individual recombinant proteins as well as the combination of all of the candidates. IGFBP2 was the sole recombinant protein capable of reducing hOPC proliferation and individually exerted an equivalent effect to the combination of all candidates. Interestingly, IGFBP2 exhibited a species-specific effect, in that human IGFBP2 (hIGFBP2) blocked proliferation but mouse IGFBP2 did not. Moreover, following infection with a lentivirus encoding the GCaMP6s calcium reporter, we observed that only hIGFBP2 induced increased calcium oscillations in a similar manner to high-density hOPC culture. While additional loss-of-function experiments are necessary, these findings strongly suggest that IGFBP2 released by hOPC exerts an anti-proliferative effect in high-density culture. In Chapter 5, to investigate the specific downstream signaling pathways that are influenced by hOPC coculture, we performed RNA-seq of mCherry+ hOPCs following coculture and FACS isolation. The expression profile of mCherry+ hOPCs indicated that coculture with either hOPCs, mOPCs, or human astrocyte-like cells exhibited a distinct transcriptional profile. Consistent with our earlier results, co-culture with hOPC induced genes associated with inhibition of proliferation. Intriguingly, while coculture did not induce O4+ oligodendrocyte differentiation in mCherry+ cells, we noted significant upregulation of several genes associated with both oligodendrocyte and astrocyte differentiation. These changes were associated with the downregulation of several negative regulators of the MAP kinase pathway, suggesting possible activation of this pathway. Notably, coculture regardless of cell identity induced a profound downregulation of cholesterol biosynthesis pathways. The successful characterization of homeostatic signals that regulate hOPC proliferation will allow us to define novel therapeutic strategies to promote cell engraftment in the context of human demyelination and, potentially, overcome the inhibitory environment that prevents efficient endogenous remyelination in multiple sclerosis.","**To request an accessible version of the file(s) associated with this item, contact library@buffalo.edu. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.**"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Species-Specific Regulation of Human Oligodendrocyte Precursor Cells Homeostasis"]}]}],"canonical_facts":{"dc:contributor":["Sim, Fraser","Genetics, Genomics and Bioinformatics"],"dc:creator":["Elhossiny, Ahmed"],"dc:date":["2025-02-21T21:36:55Z","2020"],"dc:description":["M.S.","Oligodendrocyte precursor cells (OPCs) represent the most numerous population of stem/progenitor cells in the adult human brain. Upon activation, adult OPCs divide and generate new oligodendrocytes in response to neuronal activity and following demyelination. The molecular mechanisms that govern OPC homeostasis remain poorly defined, but in vivo imaging studies have revealed that these processes are governed by their local environment such that differentiation or death of an OPC is followed by compensatory division of a neighboring OPC. However following transplantation, human OPCs (hOPCs) continuing to divide in the presence of murine OPCs (mOPC). This suggests the presence of a species-specific signal that regulates hOPC proliferation and implicates species-mismatch as a mechanism underlying the success of xenografted OPCs for myelin repair. In order to characterize the molecular mechanisms, we developed an in vitro model in which mCherry-expressing primary hOPCs were cultured either alone or in the presence of mOPCs or hOPCs (Chapter 3). As observed following transplantation, hOPC proliferation was inhibited by coculture with hOPCs but not by mOPCs. Conversely, mOPC proliferation was halted by coculture with either species OPCs. The species-specific inhibition of proliferation was dependent on cell-cell signaling as coculture with fixed hOPCs relieved the inhibitory effect. Importantly, reduced hOPC proliferation was not associated with oligodendrocyte differentiation. This cell-cell signal exhibited cell-type specificity as coculture with human astrocytes-like cells did not substantially block hOPC proliferation. We next established that the hOPC-derived signal was likely soluble using discontinuous transwell cultures and conditioned media. Proteome analysis (LC-MS and IonStar) was utilized to identify several candidates that may mediate this inhibitory effect (Chapter 4). We identified six candidate proteins which were relatively enriched in hOPC conditioned media and predicted to be actively secreted (SignalP). To determine whether these proteins could influence hOPC proliferation, we exposed hOPCs to individual recombinant proteins as well as the combination of all of the candidates. IGFBP2 was the sole recombinant protein capable of reducing hOPC proliferation and individually exerted an equivalent effect to the combination of all candidates. Interestingly, IGFBP2 exhibited a species-specific effect, in that human IGFBP2 (hIGFBP2) blocked proliferation but mouse IGFBP2 did not. Moreover, following infection with a lentivirus encoding the GCaMP6s calcium reporter, we observed that only hIGFBP2 induced increased calcium oscillations in a similar manner to high-density hOPC culture. While additional loss-of-function experiments are necessary, these findings strongly suggest that IGFBP2 released by hOPC exerts an anti-proliferative effect in high-density culture. In Chapter 5, to investigate the specific downstream signaling pathways that are influenced by hOPC coculture, we performed RNA-seq of mCherry+ hOPCs following coculture and FACS isolation. The expression profile of mCherry+ hOPCs indicated that coculture with either hOPCs, mOPCs, or human astrocyte-like cells exhibited a distinct transcriptional profile. Consistent with our earlier results, co-culture with hOPC induced genes associated with inhibition of proliferation. Intriguingly, while coculture did not induce O4+ oligodendrocyte differentiation in mCherry+ cells, we noted significant upregulation of several genes associated with both oligodendrocyte and astrocyte differentiation. These changes were associated with the downregulation of several negative regulators of the MAP kinase pathway, suggesting possible activation of this pathway. Notably, coculture regardless of cell identity induced a profound downregulation of cholesterol biosynthesis pathways. The successful characterization of homeostatic signals that regulate hOPC proliferation will allow us to define novel therapeutic strategies to promote cell engraftment in the context of human demyelination and, potentially, overcome the inhibitory environment that prevents efficient endogenous remyelination in multiple sclerosis.","**To request an accessible version of the file(s) associated with this item, contact library@buffalo.edu. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.**"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/10477/86728"],"dc:language":["eng"],"dc:publisher":["State University of New York at Buffalo"],"dc:rights":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."],"dc:subject":["genetics","neurosciences"],"dc:title":["Species-Specific Regulation of Human Oligodendrocyte Precursor Cells Homeostasis"],"dc:type":["Text","Thesis"]},"updated_at":"2026-07-27T19:05:34Z"}