title: Infarcted myocardium-like stiffness contributes to endothelial progenitor lineage commitment of bone marrow mononuclear cells.
abstract: Optimal timing of cell therapy for myocardial infarction (MI) appears during 5 to 14 days after the infarction. However, the potential mechanism requires further investigation. This work aimed to verify the hypothesis that myocardial stiffness within a propitious time frame might provide a most beneficial physical condition for cell lineage specification in favour of cardiac repair. Serum vascular endothelial growth factor (VEGF) levels and myocardial stiffness of MI mice were consecutively detected. Isolated bone marrow mononuclear cells (BMMNCs) were injected into infarction zone at distinct time-points and cardiac function were measured 2 months after infarction. Polyacrylamide gel substrates with varied stiffness were used to mechanically mimic the infarcted myocardium. BMMNCs were plated on the flexible culture substrates under different concentrations of VEGF. Endothelial progenitor lineage commitment of BMMNCs was verified by immunofluorescent technique and flow cytometry. Our results demonstrated that the optimal timing in terms of improvement of cardiac function occurred during 7 to 14 days after MI, which was consistent with maximized capillary density at this time domains, but not with peak VEGF concentration. Percentage of double-positive cells for DiI-labelled acetylated low-density lipoprotein uptake and fluorescein isothiocyanate (FITC)-UEA-1 (ulex europaeus agglutinin I lectin) binding had no significant differences among the tissue-like stiffness in high concentration VEGF. With the decrease of VEGF concentration, the benefit of 42 kPa stiffness, corresponding to infarcted myocardium at days 7 to 14, gradually occurred and peaked when it was removed from culture medium. Likewise, combined expressions of VEGFR2(+) , CD133(+)  and CD45(-)  remained the highest level on 42 kPa substrate in conditions of lower concentration VEGF. In conclusion, the optimal efficacy of BMMNCs therapy at 7 to 14 days after MI might result from non-VEGF dependent angiogenesis, and myocardial stiffness at this time domains was more suitable for endothelial progenitor lineage specification of BMMNCs. The results here highlight the need for greater attention to mechanical microenvironments in cell culture and cell therapy.
authors.affiliation: Shanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan University, Shanghai, China.
authors.forename: Shuning
authors.initials: S
authors.lastname: Zhang
authors.forename: Aijun
authors.initials: A
authors.lastname: Sun
authors.forename: Hong
authors.initials: H
authors.lastname: Ma
authors.forename: Kang
authors.initials: K
authors.lastname: Yao
authors.forename: Ning
authors.initials: N
authors.lastname: Zhou
authors.forename: Li
authors.initials: L
authors.lastname: Shen
authors.forename: Chunyu
authors.initials: C
authors.lastname: Zhang
authors.forename: Yunzeng
authors.initials: Y
authors.lastname: Zou
authors.forename: Junbo
authors.initials: J
authors.lastname: Ge
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000097:blood; D001854:Bone Marrow Cells / Q000166:cytology* / Q000378:metabolism; D016026:Bone Marrow Transplantation; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000166:cytology; D005269:Femur / Q000166:cytology; D006023:Glycoproteins / Q000097:blood; D006321:Heart / Q000503:physiopathology; D006801:Humans; D017493:Leukocyte Common Antigens / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009000:Monocytes / Q000166:cytology*; D009203:Myocardial Infarction / Q000378:metabolism / Q000628:therapy*; D018919:Neovascularization, Physiologic / Q000235:genetics; D010455:Peptides / Q000097:blood; D011930:Reaction Time; D042461:Vascular Endothelial Growth Factor A / Q000097:blood*; D059289:Vascular Stiffness / Q000502:physiology
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D006023:Glycoproteins; D008077:Lipoproteins, LDL; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse; D042461:Vascular Endothelial Growth Factor A; C032629:acetyl-LDL; D017493:Leukocyte Common Antigens; C516770:Ptprc protein, mouse