{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T08:40:00Z","timestamp":1785400800247,"version":"3.56.0"},"reference-count":31,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2026,7,24]],"date-time":"2026-07-24T00:00:00Z","timestamp":1784851200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010447","name":"German Center for Cardiovascular Research","doi-asserted-by":"publisher","award":["MA-HEI1"],"award-info":[{"award-number":["MA-HEI1"]}],"id":[{"id":"10.13039\/100010447","id-type":"DOI","asserted-by":"publisher"}]},{"award":["MA-HEI1"],"award-info":[{"award-number":["MA-HEI1"]}],"id":[{"id":"https:\/\/ror.org\/031t5w623","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["CRC1366\/2"],"award-info":[{"award-number":["CRC1366\/2"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["CRC1550\/1"],"award-info":[{"award-number":["CRC1550\/1"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["HE 3658\/16-3"],"award-info":[{"award-number":["HE 3658\/16-3"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"award":["CRC1366\/2"],"award-info":[{"award-number":["CRC1366\/2"]}],"id":[{"id":"https:\/\/ror.org\/018mejw64","id-type":"ROR","asserted-by":"publisher"}]},{"award":["CRC1550\/1"],"award-info":[{"award-number":["CRC1550\/1"]}],"id":[{"id":"https:\/\/ror.org\/018mejw64","id-type":"ROR","asserted-by":"publisher"}]},{"award":["HE 3658\/16-3"],"award-info":[{"award-number":["HE 3658\/16-3"]}],"id":[{"id":"https:\/\/ror.org\/018mejw64","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Cells"],"abstract":"<jats:p>Cardiac fibrosis plays a crucial role in heart failure, but research in this field remains challenging due to heterogeneity of cardiac fibroblast populations. In the past years, several Cre-drivers have been proposed for cardiac fibroblast-specific deletion of floxed genes in adult mouse research models. Here, we evaluated whether Tcf21-iCre, a tamoxifen-inducible Cre recombinase (iCre) under the endogenous Tcf21 promoter, was able to successfully target two floxed loci (Hypoxia inducible factor 1a (Hif1a) and the fluorescent reporter locus mTmG) after intraperitoneal tamoxifen injections. Six-week-old mice received intraperitoneal tamoxifen injections on five consecutive days to induce Cre activity, and the recombination efficiency was measured in isolated fibroblasts via qPCR, Western Blot and fluorescence microscopy. Recombination efficiency was very low, with minimal reduction in expression of Hif1a. For the mTmG locus, both bi-allelic and mono-allelic recombination was detected, with mono-allelic events suggesting low Cre activity even within Tcf21-expressing fibroblasts. The addition of experimental models of heart failure with reduced or preserved ejection fraction as pro-fibrotic stimuli or an inclusion of an additional round or higher doses of tamoxifen injections did not improve recombination efficiency of the targeted alleles. Thus, Tcf21-iCre targets only a small proportion of fibrogenic fibroblasts following i.p. tamoxifen injection, limiting its usability in loss-of-function studies that require broad fibroblast coverage and highlighting the need for alternative Cre-drivers or delivery strategies to facilitate antifibrotic therapy development.<\/jats:p>","DOI":"10.3390\/cells15151326","type":"journal-article","created":{"date-parts":[[2026,7,27]],"date-time":"2026-07-27T01:26:23Z","timestamp":1785115583000},"page":"1326","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Reassessing Tcf21-iCre for Adult Cardiac Fibroblast Gene Deletion: Limited Recombination Efficiency Following Tamoxifen Injections"],"prefix":"10.3390","volume":"15","author":[{"given":"Amelie S.","family":"Schober","sequence":"first","affiliation":[{"name":"Department of Cardiovascular Physiology, European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Stra\u00dfe 7\u201311, 68167 Mannheim, Germany"},{"name":"German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg\/Mannheim, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-2906-9915","authenticated-orcid":false,"given":"Lukas","family":"M\u00fcller","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Physiology, European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Stra\u00dfe 7\u201311, 68167 Mannheim, Germany"},{"name":"German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg\/Mannheim, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3128-6278","authenticated-orcid":false,"given":"Rhys","family":"Wardman","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Physiology, European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Stra\u00dfe 7\u201311, 68167 Mannheim, Germany"},{"name":"German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg\/Mannheim, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manuela","family":"Fuhrmann","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Physiology, European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Stra\u00dfe 7\u201311, 68167 Mannheim, Germany"},{"name":"German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg\/Mannheim, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-2897-1721","authenticated-orcid":false,"given":"Karla","family":"Vollmerig","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Physiology, European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Stra\u00dfe 7\u201311, 68167 Mannheim, Germany"},{"name":"German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg\/Mannheim, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3513-4362","authenticated-orcid":false,"given":"Felix A.","family":"Trogisch","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Physiology, European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Stra\u00dfe 7\u201311, 68167 Mannheim, Germany"},{"name":"German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg\/Mannheim, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4814-9416","authenticated-orcid":false,"given":"Gergana","family":"Dobreva","sequence":"additional","affiliation":[{"name":"German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg\/Mannheim, 69120 Heidelberg, Germany"},{"name":"Department of Cardiovascular Genomics and Epigenomics, European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Stra\u00dfe 7\u201311, 68167 Mannheim, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1541-3030","authenticated-orcid":false,"given":"Joerg","family":"Heineke","sequence":"additional","affiliation":[{"name":"Department of Cardiovascular Physiology, European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Stra\u00dfe 7\u201311, 68167 Mannheim, Germany"},{"name":"German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg\/Mannheim, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1123","DOI":"10.1016\/j.jacc.2013.11.053","article-title":"The global health and economic burden of hospitalizations for heart failure: Lessons learned from hospitalized heart failure registries","volume":"63","author":"Ambrosy","year":"2014","journal-title":"J. Am. Coll. Cardiol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1401","DOI":"10.1007\/s00204-015-1477-x","article-title":"Pathophysiology of cardiac hypertrophy and heart failure: Signaling pathways and novel therapeutic targets","volume":"89","author":"Tham","year":"2015","journal-title":"Arch. Toxicol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1016\/j.exer.2015.07.009","article-title":"Myofibroblasts","volume":"142","author":"Hinz","year":"2016","journal-title":"Exp. Eye Res."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1450","DOI":"10.1093\/cvr\/cvaa324","article-title":"Cardiac fibrosis","volume":"117","author":"Frangogiannis","year":"2021","journal-title":"Cardiovasc. Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"376","DOI":"10.1097\/FJC.0b013e3182116e39","article-title":"Fibroblasts and myofibroblasts: What are we talking about?","volume":"57","author":"Baum","year":"2011","journal-title":"J. Cardiovasc Pharmacol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"705","DOI":"10.1016\/j.devcel.2012.08.017","article-title":"A TRPC6-Dependent Pathway for Myofibroblast Transdifferentiation and Wound Healing In Vivo","volume":"23","author":"Davis","year":"2012","journal-title":"Dev. Cell"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"766","DOI":"10.1038\/s41586-025-08945-9","article-title":"Selective inhibition of stromal mechanosensing suppresses cardiac fibrosis","volume":"642","author":"Cho","year":"2025","journal-title":"Nature"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"549","DOI":"10.1161\/CIRCULATIONAHA.116.026238","article-title":"Fibroblast-Specific Genetic Manipulation of p38 Mitogen-Activated Protein Kinase In Vivo Reveals Its Central Regulatory Role in Fibrosis","volume":"136","author":"Molkentin","year":"2017","journal-title":"Circulation"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"484","DOI":"10.1038\/nrcardio.2017.57","article-title":"Redefining the identity of cardiac fibroblasts","volume":"14","author":"Tallquist","year":"2017","journal-title":"Nat. Rev. Cardiol."},{"key":"ref_10","first-page":"2269","article-title":"Defining the Cardiac Fibroblast","volume":"80","author":"Ivey","year":"2016","journal-title":"Circ. J. Off. J. Jpn. Circ. Soc."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"eadk8501","DOI":"10.1126\/sciadv.adk8501","article-title":"Integration mapping of cardiac fibroblast single-cell transcriptomes elucidates cellular principles of fibrosis in diverse pathologies","volume":"10","author":"Patrick","year":"2024","journal-title":"Sci. Adv."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2139","DOI":"10.1242\/dev.079970","article-title":"The bHLH transcription factor Tcf21 is required for lineage-specific EMT of cardiac fibroblast progenitors","volume":"139","author":"Acharya","year":"2012","journal-title":"Development"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1016\/j.yjmcc.2013.10.005","article-title":"Differential expression of embryonic epicardial progenitor markers and localization of cardiac fibrosis in adult ischemic injury and hypertensive heart disease","volume":"65","author":"Braitsch","year":"2013","journal-title":"J. Mol. Cell Cardiol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"12260","DOI":"10.1038\/ncomms12260","article-title":"Genetic lineage tracing defines myofibroblast origin and function in the injured heart","volume":"7","author":"Kanisicak","year":"2016","journal-title":"Nat. Commun."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"147","DOI":"10.5625\/lar.2018.34.4.147","article-title":"Mouse Cre-LoxP system: General principles to determine tissue-specific roles of target genes","volume":"34","author":"Kim","year":"2018","journal-title":"Lab. Anim. Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"103965","DOI":"10.1016\/j.isci.2022.103965","article-title":"Analysis of myocardial cellular gene expression during pressure overload reveals matrix based functional intercellular communication","volume":"25","author":"Froese","year":"2022","journal-title":"iScience"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"870","DOI":"10.1002\/dvg.20750","article-title":"Efficient inducible Cre-mediated recombination in Tcf21 cell lineages in the heart and kidney","volume":"49","author":"Acharya","year":"2011","journal-title":"Genesis"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"eabq4581","DOI":"10.1126\/scitranslmed.abq4581","article-title":"Endothelial cells drive organ fibrosis in mice by inducing expression of the transcription factor SOX9","volume":"16","author":"Trogisch","year":"2024","journal-title":"Sci. Transl. Med."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1038\/s41586-019-1100-z","article-title":"Nitrosative stress drives heart failure with preserved ejection fraction","volume":"568","author":"Schiattarella","year":"2019","journal-title":"Nature"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"400","DOI":"10.1161\/CIRCRESAHA.115.307778","article-title":"Revisiting Cardiac Cellular Composition","volume":"118","author":"Pinto","year":"2016","journal-title":"Circ. Res."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"466","DOI":"10.1038\/s41586-020-2797-4","article-title":"Cells of the adult human heart","volume":"588","author":"Maatz","year":"2020","journal-title":"Nature"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"H330","DOI":"10.1152\/ajpheart.00054.2019","article-title":"Platelet-derived growth factor receptor-\u03b1 is essential for cardiac fibroblast survival","volume":"317","author":"Ivey","year":"2019","journal-title":"Am. J. Physiol.-Heart Circ. Physiol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1491","DOI":"10.1101\/gad.329763.119","article-title":"Hippo pathway deletion in adult resting cardiac fibroblasts initiates a cell state transition with spontaneous and self-sustaining fibrosis","volume":"33","author":"Xiao","year":"2019","journal-title":"Genes Dev."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1443","DOI":"10.1161\/CIRCRESAHA.125.326480","article-title":"YAP-Induced Glycolysis Drives Fibroinflammation and Disrupts Fibroblast Fidelity","volume":"137","author":"Tsai","year":"2025","journal-title":"Circ. Res."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1161\/CIRCRESAHA.124.325527","article-title":"Transcription Factor 21 Regulates Cardiac Myofibroblast Formation and Fibrosis","volume":"136","author":"Johansen","year":"2025","journal-title":"Circ. Res."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"712","DOI":"10.1038\/s41467-017-00840-w","article-title":"Loss of \u03b2-catenin in resident cardiac fibroblasts attenuates fibrosis induced by pressure overload in mice","volume":"8","author":"Xiang","year":"2017","journal-title":"Nat. Commun."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"e128722","DOI":"10.1172\/jci.insight.128722","article-title":"Cell-specific ablation of Hsp47 defines the collagen-producing cells in the injured heart","volume":"4","author":"Khalil","year":"2019","journal-title":"JCI Insight"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"931","DOI":"10.1016\/j.jacbts.2020.07.009","article-title":"Blockade of Fibroblast YAP Attenuates Cardiac Fibrosis and Dysfunction Through MRTF-A Inhibition","volume":"5","author":"Francisco","year":"2020","journal-title":"JACC Basic Transl. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1161\/CIRCRESAHA.121.320324","article-title":"P53 Regulates the Extent of Fibroblast Proliferation and Fibrosis in Left Ventricle Pressure Overload","volume":"133","author":"Liu","year":"2023","journal-title":"Circ. Res."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1161\/CIRCRESAHA.109.198416","article-title":"Avoidance of Transient Cardiomyopathy in Cardiomyocyte-Targeted Tamoxifen-Induced MerCreMer Gene Deletion Models","volume":"105","author":"Koitabashi","year":"2009","journal-title":"Circ. Res."},{"key":"ref_31","first-page":"1459","article-title":"Moderate and high amounts of tamoxifen in \u03b1MHC-MerCreMer mice induce a DNA damage response, leading to heart failure and death","volume":"6","author":"Bersell","year":"2013","journal-title":"Dis. Model Mech."}],"container-title":["Cells"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4409\/15\/15\/1326\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,27]],"date-time":"2026-07-27T01:29:34Z","timestamp":1785115774000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4409\/15\/15\/1326"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,24]]},"references-count":31,"journal-issue":{"issue":"15","published-online":{"date-parts":[[2026,8]]}},"alternative-id":["cells15151326"],"URL":"https:\/\/doi.org\/10.3390\/cells15151326","relation":{},"ISSN":["2073-4409"],"issn-type":[{"value":"2073-4409","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,24]]}}}