{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/390950"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/390950","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Myc and Cyclin T1 co-expression as a therapeutic strategy for cardiac repair following myocardial infarction","abstract":"Background and Aims The inability of the heart to regenerate itself by promoting endogenous cardiomyocyte proliferation after myocardial infarction (MI), leads to scarring, cell hypertrophy, and loss of contractility in the left ventricle. Driving endogenous cardiomyocyte proliferation is a promising avenue for heart remuscularisation in the context of ischaemic damage. Overexpression of Ccnt1 creates a permissive molecular environment for Myc-driven cell cycle reactivation in organs with limited regenerative capacity, such as the adult mammalian heart. The overarching goal of this study is to elucidate whether the co-expression of Myc and Cyclin T1 in a genetic mouse model setting and from a bicistronic mRNA vector could drive adult rodent cardiomyocyte cell-cycle re-entry in the context of injury and lead to functional improvement. Methods Whole-heart single-nuclei RNA sequencing (snRNAseq), in vivo experiments, histology methods, and molecular biology techniques were used to assess Myc and Ccnt1 induced cardiomyocyte-specific gene expression changes, validate cardiomyocyte cell cycle progression, as well as assess the effect on cardiac repair after MI. The study utilised a combination of genetic mouse models of R26-MycER coupled with Myh6-Cre and Cre mRNA cassette excision and with AVV9-cTnT-Ccnt1 treatment at 4 weeks of age, as well as modified mRNA transfection in adult CD1 mice and Lewis rats. Assessment of the therapeutic efficacy of Myc and Ccnt1 co-expression was based on long-term cardiac function studies in the context of both genetic expression as well as acute and delayed treatment with Myc-Ccnt1 mRNA after permanent LAD ligation in mice and rats. Cardiac function was assessed by echocardiography in 2D B-mode and M-mode for ejection fraction (EF%) primary endpoint and related LV function parameters. Results Activation of MycER for 48 hours triggered cardiomyocyte cell cycle re-entry in both non-injured 8-week animals and LAD P/L injured animals with greater effects observed near the infarct border zone. snRNAseq analysis of healthy juvenile, healthy adult and MI-injured adult whole hearts confirmed the transcriptional reprogramming of cardiomyocytes and identified a population of proliferative cardiomyocytes as well as changes to cell-cell interactions in the cardiac niche. Cre mRNA localised transient activation of MycER leads to over 13% improvement in ejection fraction (EF%) and scar size reduction 28 days post-MI in mice. To translate the findings into a proto-therapeutic strategy, in collaboration we developed Myc-Ccnt1 modified mRNA as a transient and non-integrating modality for cardiac repair. A single dose of Myc-Ccnt1 mRNA is sufficient to drive cardiomyocyte cell cycle re-entry, which was validated in vitro in ESC-derived cardiomyocyte culture. snRNAseq analysis of whole mouse hearts at 24h post-injection with Myc-Ccnt1 mRNA showed both Myc-dependent and exogenous RNA-driven responses, including in non-cardiomyocyte cells such as fibroblasts. To address the ability of Myc-Ccnt1 to drive cardiac repair in a delayed administration setting, low and high doses of mRNA-LNP formulation were delivered to rats in a chest reopening model 7 days post-MI. The follow-up at 28 days post-treatment showed EF% improvement with the low-dose treatment, as well as changes in collagen deposition, scar remuscularisation and cardiomyocyte proliferation with the high-dose treatment. Conclusion The novel body of research strongly indicates feasibility of further development of Myc and Ccnt1 co-expression as a therapeutic modality for cardiac repair after myocardial infarction. Transient co-expression of Myc and Cyclin T1 drives substantial adult cardiomyocyte cell-cycle re-entry and promotes cardiac repair after injury both acutely and in a clinically relevant setting of established pathology. Collectively, these findings indicate that Myc-Ccnt1 modRNA has undeniable potential to be an effective approach for cardiac regeneration.","abstract_html":"Background and Aims The inability of the heart to regenerate itself by promoting endogenous cardiomyocyte proliferation after myocardial infarction (MI), leads to scarring, cell hypertrophy, and loss of contractility in the left ventricle. Driving endogenous cardiomyocyte proliferation is a promising avenue for heart remuscularisation in the context of ischaemic damage. Overexpression of Ccnt1 creates a permissive molecular environment for Myc-driven cell cycle reactivation in organs with limited regenerative capacity, such as the adult mammalian heart. The overarching goal of this study is to elucidate whether the co-expression of Myc and Cyclin T1 in a genetic mouse model setting and from a bicistronic mRNA vector could drive adult rodent cardiomyocyte cell-cycle re-entry in the context of injury and lead to functional improvement. Methods Whole-heart single-nuclei RNA sequencing (snRNAseq), in vivo experiments, histology methods, and molecular biology techniques were used to assess Myc and Ccnt1 induced cardiomyocyte-specific gene expression changes, validate cardiomyocyte cell cycle progression, as well as assess the effect on cardiac repair after MI. The study utilised a combination of genetic mouse models of R26-MycER coupled with Myh6-Cre and Cre mRNA cassette excision and with AVV9-cTnT-Ccnt1 treatment at 4 weeks of age, as well as modified mRNA transfection in adult CD1 mice and Lewis rats. Assessment of the therapeutic efficacy of Myc and Ccnt1 co-expression was based on long-term cardiac function studies in the context of both genetic expression as well as acute and delayed treatment with Myc-Ccnt1 mRNA after permanent LAD ligation in mice and rats. Cardiac function was assessed by echocardiography in 2D B-mode and M-mode for ejection fraction (EF%) primary endpoint and related LV function parameters. Results Activation of MycER for 48 hours triggered cardiomyocyte cell cycle re-entry in both non-injured 8-week animals and LAD P/L injured animals with greater effects observed near the infarct border zone. snRNAseq analysis of healthy juvenile, healthy adult and MI-injured adult whole hearts confirmed the transcriptional reprogramming of cardiomyocytes and identified a population of proliferative cardiomyocytes as well as changes to cell-cell interactions in the cardiac niche. Cre mRNA localised transient activation of MycER leads to over 13% improvement in ejection fraction (EF%) and scar size reduction 28 days post-MI in mice. To translate the findings into a proto-therapeutic strategy, in collaboration we developed Myc-Ccnt1 modified mRNA as a transient and non-integrating modality for cardiac repair. A single dose of Myc-Ccnt1 mRNA is sufficient to drive cardiomyocyte cell cycle re-entry, which was validated in vitro in ESC-derived cardiomyocyte culture. snRNAseq analysis of whole mouse hearts at 24h post-injection with Myc-Ccnt1 mRNA showed both Myc-dependent and exogenous RNA-driven responses, including in non-cardiomyocyte cells such as fibroblasts. To address the ability of Myc-Ccnt1 to drive cardiac repair in a delayed administration setting, low and high doses of mRNA-LNP formulation were delivered to rats in a chest reopening model 7 days post-MI. The follow-up at 28 days post-treatment showed EF% improvement with the low-dose treatment, as well as changes in collagen deposition, scar remuscularisation and cardiomyocyte proliferation with the high-dose treatment. Conclusion The novel body of research strongly indicates feasibility of further development of Myc and Ccnt1 co-expression as a therapeutic modality for cardiac repair after myocardial infarction. Transient co-expression of Myc and Cyclin T1 drives substantial adult cardiomyocyte cell-cycle re-entry and promotes cardiac repair after injury both acutely and in a clinically relevant setting of established pathology. Collectively, these findings indicate that Myc-Ccnt1 modRNA has undeniable potential to be an effective approach for cardiac regeneration.","abstract_has_math":false,"creators":["Boikova, Aleksandra"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Wilson, Catherine H"],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-01-13","date_published":"2025-01-13","updated_at":"2026-07-22T22:24:20Z","subjects":["cardiac regeneration","Myc","Cyclin T1","cardiomyocyte proliferation","modified mRNA","myocardial infarction"],"languages":["eng"],"rights":[],"rights_urls":["https://www.repository.cam.ac.uk/bitstreams/21dd9c58-c12f-43c2-900a-4993763143e9/download","http://purl.org/NET/rdflicense/allrightsreserved"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.122280","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Wilson, Catherine H"]},{"key":"dc:contributor.sponsor","label":"Sponsor","values":["AstraZeneca PhD Studentship"]},{"key":"dc:creator","label":"Author","values":["Boikova, Aleksandra"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2025-01-13"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/390950"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["cardiac regeneration","Myc","Cyclin T1","cardiomyocyte proliferation","modified mRNA","myocardial infarction"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://www.repository.cam.ac.uk/bitstreams/21dd9c58-c12f-43c2-900a-4993763143e9/download","http://purl.org/NET/rdflicense/allrightsreserved"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.17863/CAM.122280"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://www.repository.cam.ac.uk/bitstreams/46cecd32-156f-414e-8a22-8c6de1a2b635/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Background and Aims The inability of the heart to regenerate itself by promoting endogenous cardiomyocyte proliferation after myocardial infarction (MI), leads to scarring, cell hypertrophy, and loss of contractility in the left ventricle. Driving endogenous cardiomyocyte proliferation is a promising avenue for heart remuscularisation in the context of ischaemic damage. Overexpression of Ccnt1 creates a permissive molecular environment for Myc-driven cell cycle reactivation in organs with limited regenerative capacity, such as the adult mammalian heart. The overarching goal of this study is to elucidate whether the co-expression of Myc and Cyclin T1 in a genetic mouse model setting and from a bicistronic mRNA vector could drive adult rodent cardiomyocyte cell-cycle re-entry in the context of injury and lead to functional improvement. Methods Whole-heart single-nuclei RNA sequencing (snRNAseq), in vivo experiments, histology methods, and molecular biology techniques were used to assess Myc and Ccnt1 induced cardiomyocyte-specific gene expression changes, validate cardiomyocyte cell cycle progression, as well as assess the effect on cardiac repair after MI. The study utilised a combination of genetic mouse models of R26-MycER coupled with Myh6-Cre and Cre mRNA cassette excision and with AVV9-cTnT-Ccnt1 treatment at 4 weeks of age, as well as modified mRNA transfection in adult CD1 mice and Lewis rats. Assessment of the therapeutic efficacy of Myc and Ccnt1 co-expression was based on long-term cardiac function studies in the context of both genetic expression as well as acute and delayed treatment with Myc-Ccnt1 mRNA after permanent LAD ligation in mice and rats. Cardiac function was assessed by echocardiography in 2D B-mode and M-mode for ejection fraction (EF%) primary endpoint and related LV function parameters. Results Activation of MycER for 48 hours triggered cardiomyocyte cell cycle re-entry in both non-injured 8-week animals and LAD P/L injured animals with greater effects observed near the infarct border zone. snRNAseq analysis of healthy juvenile, healthy adult and MI-injured adult whole hearts confirmed the transcriptional reprogramming of cardiomyocytes and identified a population of proliferative cardiomyocytes as well as changes to cell-cell interactions in the cardiac niche. Cre mRNA localised transient activation of MycER leads to over 13% improvement in ejection fraction (EF%) and scar size reduction 28 days post-MI in mice. To translate the findings into a proto-therapeutic strategy, in collaboration we developed Myc-Ccnt1 modified mRNA as a transient and non-integrating modality for cardiac repair. A single dose of Myc-Ccnt1 mRNA is sufficient to drive cardiomyocyte cell cycle re-entry, which was validated in vitro in ESC-derived cardiomyocyte culture. snRNAseq analysis of whole mouse hearts at 24h post-injection with Myc-Ccnt1 mRNA showed both Myc-dependent and exogenous RNA-driven responses, including in non-cardiomyocyte cells such as fibroblasts. To address the ability of Myc-Ccnt1 to drive cardiac repair in a delayed administration setting, low and high doses of mRNA-LNP formulation were delivered to rats in a chest reopening model 7 days post-MI. The follow-up at 28 days post-treatment showed EF% improvement with the low-dose treatment, as well as changes in collagen deposition, scar remuscularisation and cardiomyocyte proliferation with the high-dose treatment. Conclusion The novel body of research strongly indicates feasibility of further development of Myc and Ccnt1 co-expression as a therapeutic modality for cardiac repair after myocardial infarction. Transient co-expression of Myc and Cyclin T1 drives substantial adult cardiomyocyte cell-cycle re-entry and promotes cardiac repair after injury both acutely and in a clinically relevant setting of established pathology. Collectively, these findings indicate that Myc-Ccnt1 modRNA has undeniable potential to be an effective approach for cardiac regeneration."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["9255a0631551d557193add6a35bb306b","87eda9de84448d1f82354d60eee3eb5f"]},{"key":"dc:title","label":"Title","values":["Myc and Cyclin T1 co-expression as a therapeutic strategy for cardiac repair following myocardial infarction"]}]}],"canonical_facts":{"dc:contributor.advisor":["Wilson, Catherine H"],"dc:contributor.sponsor":["AstraZeneca PhD Studentship"],"dc:creator":["Boikova, Aleksandra"],"dc:date.issued":["2025-01-13"],"dc:description.abstract":["Background and Aims The inability of the heart to regenerate itself by promoting endogenous cardiomyocyte proliferation after myocardial infarction (MI), leads to scarring, cell hypertrophy, and loss of contractility in the left ventricle. Driving endogenous cardiomyocyte proliferation is a promising avenue for heart remuscularisation in the context of ischaemic damage. Overexpression of Ccnt1 creates a permissive molecular environment for Myc-driven cell cycle reactivation in organs with limited regenerative capacity, such as the adult mammalian heart. The overarching goal of this study is to elucidate whether the co-expression of Myc and Cyclin T1 in a genetic mouse model setting and from a bicistronic mRNA vector could drive adult rodent cardiomyocyte cell-cycle re-entry in the context of injury and lead to functional improvement. Methods Whole-heart single-nuclei RNA sequencing (snRNAseq), in vivo experiments, histology methods, and molecular biology techniques were used to assess Myc and Ccnt1 induced cardiomyocyte-specific gene expression changes, validate cardiomyocyte cell cycle progression, as well as assess the effect on cardiac repair after MI. The study utilised a combination of genetic mouse models of R26-MycER coupled with Myh6-Cre and Cre mRNA cassette excision and with AVV9-cTnT-Ccnt1 treatment at 4 weeks of age, as well as modified mRNA transfection in adult CD1 mice and Lewis rats. Assessment of the therapeutic efficacy of Myc and Ccnt1 co-expression was based on long-term cardiac function studies in the context of both genetic expression as well as acute and delayed treatment with Myc-Ccnt1 mRNA after permanent LAD ligation in mice and rats. Cardiac function was assessed by echocardiography in 2D B-mode and M-mode for ejection fraction (EF%) primary endpoint and related LV function parameters. Results Activation of MycER for 48 hours triggered cardiomyocyte cell cycle re-entry in both non-injured 8-week animals and LAD P/L injured animals with greater effects observed near the infarct border zone. snRNAseq analysis of healthy juvenile, healthy adult and MI-injured adult whole hearts confirmed the transcriptional reprogramming of cardiomyocytes and identified a population of proliferative cardiomyocytes as well as changes to cell-cell interactions in the cardiac niche. Cre mRNA localised transient activation of MycER leads to over 13% improvement in ejection fraction (EF%) and scar size reduction 28 days post-MI in mice. To translate the findings into a proto-therapeutic strategy, in collaboration we developed Myc-Ccnt1 modified mRNA as a transient and non-integrating modality for cardiac repair. A single dose of Myc-Ccnt1 mRNA is sufficient to drive cardiomyocyte cell cycle re-entry, which was validated in vitro in ESC-derived cardiomyocyte culture. snRNAseq analysis of whole mouse hearts at 24h post-injection with Myc-Ccnt1 mRNA showed both Myc-dependent and exogenous RNA-driven responses, including in non-cardiomyocyte cells such as fibroblasts. To address the ability of Myc-Ccnt1 to drive cardiac repair in a delayed administration setting, low and high doses of mRNA-LNP formulation were delivered to rats in a chest reopening model 7 days post-MI. The follow-up at 28 days post-treatment showed EF% improvement with the low-dose treatment, as well as changes in collagen deposition, scar remuscularisation and cardiomyocyte proliferation with the high-dose treatment. Conclusion The novel body of research strongly indicates feasibility of further development of Myc and Ccnt1 co-expression as a therapeutic modality for cardiac repair after myocardial infarction. Transient co-expression of Myc and Cyclin T1 drives substantial adult cardiomyocyte cell-cycle re-entry and promotes cardiac repair after injury both acutely and in a clinically relevant setting of established pathology. Collectively, these findings indicate that Myc-Ccnt1 modRNA has undeniable potential to be an effective approach for cardiac regeneration."],"dc:format.checksum.md5":["9255a0631551d557193add6a35bb306b","87eda9de84448d1f82354d60eee3eb5f"],"dc:identifier.doi":["https://doi.org/10.17863/CAM.122280"],"dc:identifier.uri":["https://www.repository.cam.ac.uk/bitstreams/46cecd32-156f-414e-8a22-8c6de1a2b635/download"],"dc:language":["eng"],"dc:publisher.institution":["University of Cambridge"],"dc:relation.isreferencedby.uri":["https://www.repository.cam.ac.uk/handle/1810/390950"],"dc:rights":["https://www.repository.cam.ac.uk/bitstreams/21dd9c58-c12f-43c2-900a-4993763143e9/download","http://purl.org/NET/rdflicense/allrightsreserved"],"dc:subject":["cardiac regeneration","Myc","Cyclin T1","cardiomyocyte proliferation","modified mRNA","myocardial infarction"],"dc:title":["Myc and Cyclin T1 co-expression as a therapeutic strategy for cardiac repair following myocardial infarction"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-22T22:24:20Z"}