RESUMEN
The success of cell therapy for the treatment of myocardial infarction depends on finding novel approaches that can substantially implement the engraftment of the transplanted cells. In order to enhance cell engraftment, most studies have focused on the pretreatment of transplantable cells. Here we have considered an alternative approach that involves the preconditioning of infarcted heart tissue to reduce endogenous cell activity and thus provide an advantage to our exogenous cells. This treatment is routinely used in other tissues such as bone marrow and skeletal muscle to improve cell engraftment, but it has never been taken in cardiac tissue. To avoid long-term cardiotoxicity induced by full heart irradiation we developed a rat model of a catheter-based heart irradiation system to locally impact a delimited region of the infarcted cardiac tissue. As proof of concept, we transferred ZsGreen+ iPSCs in the infarcted heart, due to their ease of use and detection. We found a very significant increase in cell engraftment in preirradiated rats. In this study, we demonstrate for the first time that preconditioning the infarcted cardiac tissue with local irradiation can substantially enhance cell engraftment.
Asunto(s)
Braquiterapia/métodos , Precondicionamiento Isquémico/métodos , Infarto del Miocardio/terapia , Trasplante de Células Madre/métodos , Animales , Células Cultivadas , Corazón/efectos de la radiación , Células Madre Pluripotentes Inducidas/trasplante , Masculino , Ratones , Ratas , Ratas Sprague-DawleyRESUMEN
Liver sinusoidal endothelial cells (LSECs) are the first liver cells to encounter waste macromolecules, pathogens, and toxins in blood. LSECs are highly specialized to mediate the clearance of these substances via endocytic scavenger receptors and are equipped with fenestrae that mediate the passage of macromolecules toward hepatocytes. Although some transcription factors (TFs) are known to play a role in LSEC specialization, information about the specialized LSEC signature and its transcriptional determinants remains incomplete.Based on a comparison of liver, heart, and brain endothelial cells (ECs), we established a 30-gene LSEC signature comprising both established and newly identified markers, including 7 genes encoding TFs. To evaluate the LSEC TF regulatory network, we artificially increased the expression of the 7 LSEC-specific TFs in human umbilical vein ECs. Although Zinc finger E-box-binding protein 2, homeobox B5, Cut-like homolog 2, and transcription factor EC (TCFEC) had limited contributions, musculoaponeurotic fibrosarcoma (C-MAF), GATA binding protein 4 (GATA4), and MEIS homeobox 2 (MEIS2) emerged as stronger inducers of LSEC marker expression. Furthermore, a combination of C-MAF, GATA4, and MEIS2 showed a synergistic effect on the increase of LSEC signature genes, including liver/lymph node-specific ICAM-3 grabbing non-integrin (L-SIGN) (or C-type lectin domain family member M (CLEC4M)), mannose receptor C-Type 1 (MRC1), legumain (LGMN), G protein-coupled receptor 182 (GPR182), Plexin C1 (PLXNC1), and solute carrier organic anion transporter family member 2A1 (SLCO2A1). Accordingly, L-SIGN, MRC1, pro-LGMN, GPR182, PLXNC1, and SLCO2A1 protein levels were elevated by this combined overexpression. Although receptor-mediated endocytosis was not significantly induced by the triple TF combination, it enhanced binding to E2, the hepatitis C virus host-binding protein. We conclude that C-MAF, GATA4, and MEIS2 are important transcriptional regulators of the unique LSEC fingerprint and LSEC interaction with viruses. Additional factors are however required to fully recapitulate the molecular, morphological, and functional LSEC fingerprint.NEW & NOTEWORTHY Liver sinusoidal endothelial cells (LSECs) are the first liver cells to encounter waste macromolecules, pathogens, and toxins in the blood and are highly specialized. Although some transcription factors are known to play a role in LSEC specialization, information about the specialized LSEC signature and its transcriptional determinants remains incomplete. Here, we show that Musculoaponeurotic Fibrosarcoma (C-MAF), GATA binding protein 4 (GATA4), and Meis homeobox 2 (MEIS2) are important transcriptional regulators of the unique LSEC signature and that they affect the interaction of LSECs with viruses.
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Células Endoteliales/fisiología , Regulación de la Expresión Génica/fisiología , Hígado/citología , Animales , Marcadores Genéticos , Humanos , Hígado/metabolismo , Masculino , Especificidad de Órganos , Ratas , TranscriptomaRESUMEN
BACKGROUND: Microvascular endothelium in different organs is specialized to fulfill the particular needs of parenchymal cells. However, specific information about heart capillary endothelial cells (ECs) is lacking. METHODS AND RESULTS: Using microarray profiling on freshly isolated ECs from heart, brain, and liver, we revealed a genetic signature for microvascular heart ECs and identified Meox2/Tcf15 heterodimers as novel transcriptional determinants. This signature was largely shared with skeletal muscle and adipose tissue endothelium and was enriched in genes encoding fatty acid (FA) transport-related proteins. Using gain- and loss-of-function approaches, we showed that Meox2/Tcf15 mediate FA uptake in heart ECs, in part, by driving endothelial CD36 and lipoprotein lipase expression and facilitate FA transport across heart ECs. Combined Meox2 and Tcf15 haplodeficiency impaired FA uptake in heart ECs and reduced FA transfer to cardiomyocytes. In the long term, this combined haplodeficiency resulted in impaired cardiac contractility. CONCLUSIONS: Our findings highlight a regulatory role for ECs in FA transfer to the heart parenchyma and unveil 2 of its intrinsic regulators. Our insights could be used to develop new strategies based on endothelial Meox2/Tcf15 targeting to modulate FA transfer to the heart and remedy cardiac dysfunction resulting from altered energy substrate usage.
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Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/fisiología , Células Endoteliales/metabolismo , Proteínas de Unión a Ácidos Grasos/biosíntesis , Ácidos Grasos/metabolismo , Proteínas de Homeodominio/fisiología , Miocardio/metabolismo , Tejido Adiposo/irrigación sanguínea , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/química , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/deficiencia , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Antígenos CD36/biosíntesis , Antígenos CD36/genética , Gasto Cardíaco Bajo/etiología , Gasto Cardíaco Bajo/genética , Gasto Cardíaco Bajo/metabolismo , Células Cultivadas , Vasos Coronarios/citología , Proteínas de Unión a Ácidos Grasos/genética , Glucosa/metabolismo , Heterocigoto , Proteínas de Homeodominio/química , Proteínas de Homeodominio/genética , Humanos , Lipoproteína Lipasa/biosíntesis , Lipoproteína Lipasa/genética , Lipoproteínas VLDL/metabolismo , Ratones , Ratones Endogámicos C57BL , Mapeo de Interacción de Proteínas , ARN Interferente Pequeño/farmacología , Análisis de Matrices Tisulares , TranscriptomaRESUMEN
Endothelial cell (EC) identity is in part genetically predetermined. Transcription factor NR2F2 (also known as chicken ovalbumin upstream promoter transcription factor II, COUP-TFII) plays a key role in EC fate decision making; however, many of the underlying mechanisms remain enigmatic. In the present study, we demonstrate that NR2F2 differentially regulates gene expression of venous versus lymphatic ECs (LECs) and document a novel paradigm whereby NR2F2 homodimers induce a venous EC fate, while heterodimers with the LEC-specific transcription factor PROX1 instruct LEC lineage specification. NR2F2 homodimers inhibit arterial differentiation in venous ECs through direct binding to the promoter regions of the Notch target genes HEY1 and HEY2 (HEY1/2), whereas NR2F2/PROX1 heterodimers lack this inhibitory effect, resulting at least in part in non-canonical HEY1/2 expression in LECs. Furthermore, NR2F2/PROX1 heterodimers actively induce or are permissive for the expression of a major subset of LEC-specific genes. In addition to NR2F2/PROX1 heterodimerisation, the expression of HEY1 and some of these LEC-specific genes is dependent on PROX1 DNA binding. Thus, NR2F2 homodimers in venous ECs and NR2F2/PROX1 heterodimers in LECs differentially regulate EC subtype-specific genes and pathways, most prominently the Notch target genes HEY1/2. This novel mechanistic insight could pave the way for new therapeutic interventions for vascular-bed-specific disorders.
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Factor de Transcripción COUP II/metabolismo , Endotelio Vascular/metabolismo , Proteínas de Homeodominio/metabolismo , Vasos Linfáticos/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Venas/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Western Blotting , Proteínas de Ciclo Celular/genética , Línea Celular , Células Cultivadas , Inmunoprecipitación de Cromatina , Humanos , Multimerización de Proteína , Reacción en Cadena en Tiempo Real de la Polimerasa , Proteínas Represoras/genéticaRESUMEN
Endothelial cells (ECs) lining arteries and veins have distinct molecular/functional signatures. The underlying regulatory mechanisms are incompletely understood. Here, we established a specific fingerprint of freshly isolated arterial and venous ECs from human umbilical cord comprising 64 arterial and 12 venous genes, representing distinct functions/pathways. Among the arterial genes were 8 transcription factors (TFs), including Notch target HEY2, the current "gold standard" determinant for arterial EC (aEC) specification. Culture abrogated differential gene expression in part due to gradual loss of canonical Notch activity and HEY2 expression. Notably, restoring HEY2 expression or Delta-like4-induced Notch signaling in cultured ECs only partially reinstated the aEC gene signature, whereas combined overexpression of the 8 TFs restored this fingerprint more robustly. Whereas some TFs stimulated few genes, others boosted a large proportion of arterial genes. Although there was some overlap and cross-regulation, the TFs largely complemented each other in regulating the aEC gene profile. Finally, overexpression of the 8 TFs in human umbilical vein ECs conveyed an arterial-like behavior upon their implantation in a Matrigel plug in vivo. Thus, our study shows that Notch signaling determines only part of the aEC signature and identifies additional novel and complementary transcriptional players in the complex regulation of human arteriovenous EC identity.
Asunto(s)
Arterias/citología , Células Endoteliales/metabolismo , Factores de Transcripción/genética , Transcriptoma , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Western Blotting , Línea Celular , Células Cultivadas , Análisis por Conglomerados , Redes Reguladoras de Genes , Células Endoteliales de la Vena Umbilical Humana/metabolismo , Humanos , Modelos Genéticos , Análisis de Secuencia por Matrices de Oligonucleótidos , Interferencia de ARN , Receptores Notch/genética , Receptores Notch/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/genética , Factores de Transcripción/metabolismoRESUMEN
BACKGROUND: In mice MEOX2/TCF15 heterodimers are highly expressed in heart endothelial cells and are involved in the transcriptional regulation of lipid transport. In a general population, we investigated whether genetic variation in these genes predicted coronary heart disease (CHD). RESULTS: In 2027 participants randomly recruited from a Flemish population (51.0 % women; mean age 43.6 years), we genotyped six SNPs in MEOX2 and four in TCF15. Over 15.2 years (median), CHD, myocardial infarction, coronary revascularisation and ischaemic cardiomyopathy occurred in 106, 53, 78 and 22 participants. For SNPs, we contrasted CHD risk in minor-allele heterozygotes and homozygotes (variant) vs. major-allele homozygotes (reference) and for haplotypes carriers (variant) vs. non-carriers. In multivariable-adjusted analyses with correction for multiple testing, CHD risk was associated with MEOX2 SNPs (P ≤ 0.049), but not with TCF15 SNPs (P ≥ 0.29). The MEOX2 GTCCGC haplotype (frequency 16.5 %) was associated with the sex- and age-standardised CHD incidence (5.26 vs. 3.03 events per 1000 person-years; P = 0.036); the multivariable-adjusted hazard ratio [HR] of CHD was 1.78 (95 % confidence interval, 1.25-2.56; P = 0.0054). For myocardial infarction, coronary revascularisation, and ischaemic cardiomyopathy, the corresponding HRs were 1.96 (1.16-3.31), 1.87 (1.20-2.91) and 3.16 (1.41-7.09), respectively. The MEOX2 GTCCGC haplotype significantly improved the prediction of CHD over and beyond traditional risk factors and was associated with similar population-attributable risk as smoking (18.7 % vs. 16.2 %). CONCLUSIONS: Genetic variation in MEOX2, but not TCF15, is a strong predictor of CHD. Further experimental studies should elucidate the underlying molecular mechanisms.
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Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Enfermedad de la Arteria Coronaria/epidemiología , Enfermedad de la Arteria Coronaria/genética , Etnicidad/genética , Variación Genética , Proteínas de Homeodominio/genética , Adulto , Bélgica/epidemiología , Comorbilidad , Femenino , Genotipo , Haplotipos , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple , Adulto JovenRESUMEN
Naive human pluripotent stem cells (hPSCs) are defined as the in vitro counterpart of the human preimplantation embryo's epiblast and are used as a model system to study developmental processes. In this study, we report the discovery and characterization of distinct cell populations coexisting with epiblast-like cells in 5iLAF naive human induced PSC (hiPSC) cultures. It is noteworthy that these populations closely resemble different cell types of the human embryo at early developmental stages. While epiblast-like cells represent the main cell population, interestingly we detect a cell population with gene and transposable element expression profile closely resembling the totipotent eight-cell (8C)-stage human embryo, and three cell populations analogous to trophectoderm cells at different stages of their maturation process: transition, early, and mature stages. Moreover, we reveal the presence of cells resembling primitive endoderm. Thus, 5iLAF naive hiPSC cultures provide an excellent opportunity to model the earliest events of human embryogenesis, from the 8C stage to the peri-implantation period.
Asunto(s)
Embrión de Mamíferos , Células Madre Pluripotentes , Humanos , Desarrollo Embrionario/genética , Endodermo , Estratos Germinativos , Diferenciación Celular/genética , BlastocistoRESUMEN
Transthyretin (TTR) amyloid cardiomyopathy (ATTR-CM) is a life-threatening disease caused by the abnormal production of misfolded TTR protein by liver cells, which is then released systemically. Its amyloid deposition in the heart is linked to cardiac toxicity and progression toward heart failure. A human induced pluripotent stem cell (iPSC) line was generated from peripheral blood mononuclear cells (PBMCs) from a patient suffering familial transthyretin amyloid cardiomyopathy carrying a c.128G>A (p.Ser43Asn) mutation in the TTR gene. This iPSC line offers a useful resource to study the disease pathophysiology and a cell-based model for therapeutic discovery.
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Cardiomiopatías , Células Madre Pluripotentes Inducidas , Humanos , Prealbúmina/genética , Leucocitos Mononucleares , Mutación/genética , Cardiomiopatías/genéticaRESUMEN
Generating organs from stem cells through blastocyst complementation is a promising approach to meet the clinical need for transplants. In order to generate rejection-free organs, complementation of both parenchymal and vascular cells must be achieved, as endothelial cells play a key role in graft rejection. Here, we used a lineage-specific cell ablation system to produce mouse embryos unable to form both the cardiac and vascular systems. By mouse intraspecies blastocyst complementation, we rescued heart and vascular system development separately and in combination, obtaining complemented hearts with cardiomyocytes and endothelial cells of exogenous origin. Complemented chimeras were viable and reached adult stage, showing normal cardiac function and no signs of histopathological defects in the heart. Furthermore, we implemented the cell ablation system for rat-to-mouse blastocyst complementation, obtaining xenogeneic hearts whose cardiomyocytes were completely of rat origin. These results represent an advance in the experimentation towards the in vivo generation of transplantable organs.
Asunto(s)
Sistema Cardiovascular , Corazón , Células Madre Pluripotentes , Animales , Ratones , Ratas , Blastocisto , Células Endoteliales , Miocitos Cardíacos , Corazón/embriología , Sistema Cardiovascular/embriologíaRESUMEN
Each year, tens of thousands of people worldwide die of end-stage organ failure due to the limited availability of organs for use in transplantation. To meet this clinical demand, one of the last frontiers of regenerative medicine is the generation of humanized organs in pigs from pluripotent stem cells (PSCs) via blastocyst complementation. For this, organ-disabled pig models are needed. As endothelial cells (ECs) play a critical role in xenotransplantation rejection in every organ, we aimed to produce hematoendothelial-disabled pig embryos targeting the master transcription factor ETV2 via CRISPR-Cas9-mediated genome modification. In this study, we designed five different guide RNAs (gRNAs) against the DNA-binding domain of the porcine ETV2 gene, which were tested on porcine fibroblasts in vitro. Four out of five guides showed cleavage capacity and, subsequently, these four guides were microinjected individually as ribonucleoprotein complexes (RNPs) into one-cell-stage porcine embryos. Next, we combined the two gRNAs that showed the highest targeting efficiency and microinjected them at higher concentrations. Under these conditions, we significantly improved the rate of biallelic mutation. Hence, here, we describe an efficient one-step method for the generation of hematoendothelial-disabled pig embryos via CRISPR-Cas9 microinjection in zygotes. This model could be used in experimentation related to the in vivo generation of humanized organs.
RESUMEN
We generated ATCi-MF1 induced pluripotent stem (iPS) cell line from Macaca fascicularis adult skin fibroblasts using non-integrative Sendai viruses carrying OCT3/4, KLF4, SOX2 and c-MYC. Once established, ATCi-MF1 cells present a normal karyotype, are Sendai virus-free and express pluripotency associated markers. Microsatellite markers analysis confirmed the origin of the iPS cells from the parental fibroblasts. Pluripotency was tested with the in vivo teratoma formation assay. ATCi-MF1 cell line may be a useful primate iPS cell model to test different experimental conditions where the use of human cells can imply ethical issues, as microinjection of pluripotent stem cells in pre-implantational embryos.
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Fibroblastos/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Virus Sendai , Piel/metabolismo , Factores de Transcripción , Transducción Genética , Animales , Línea Celular , Fibroblastos/citología , Células Madre Pluripotentes Inducidas/citología , Factor 4 Similar a Kruppel , Macaca fascicularis , Piel/citología , Factores de Transcripción/biosíntesis , Factores de Transcripción/genéticaRESUMEN
We generated two rat embryonic stem cell (ESC) lines: ATCe-SD7.8 from Sprague-Dawley strain and ATCe-WK1 from Wistar Kyoto strain. Cells were marked with enhanced green fluorescent protein (eGFP) by transduction with a lentiviral vector. Cells present a normal karyotype and express pluripotency-associated markers. Pluripotency was tested in vivo with the teratoma formation assay. Cells maintain eGFP expression upon differentiation to the three-germ layers. These cells can be a useful tool for cell therapy studies and chimera generation as they can be easily tracked by eGFP expression.
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Separación Celular , Células Madre Embrionarias/metabolismo , Proteínas Fluorescentes Verdes/metabolismo , Animales , Células Madre Embrionarias/citología , Proteínas Fluorescentes Verdes/genética , Ratas , Ratas Endogámicas WKY , Ratas Sprague-Dawley , Ratas TransgénicasRESUMEN
We generated a rat iPSC line called ATCi-rSD95 from transgenic Sprague-Dawley GFP fetal fibroblasts. Established ATCi-rSD95 cells present a normal karyotype, silencing of the transgenes and express pluripotency-associated markers. Additionally, ATCi-rSD95 cells are able to form teratoma with differentiated cells derived from the three germ-layers that maintain the GFP expression.
Asunto(s)
Proteínas Fluorescentes Verdes/biosíntesis , Células Madre Pluripotentes Inducidas/metabolismo , Animales , Línea Celular , Proteínas Fluorescentes Verdes/genética , Células Madre Pluripotentes Inducidas/citología , Ratas , Ratas TransgénicasRESUMEN
Collateral remodeling is critical for blood flow restoration in peripheral arterial disease and is triggered by increasing fluid shear stress in preexisting collateral arteries. So far, no arterial-specific mediators of this mechanotransduction response have been identified. We show that muscle segment homeobox 1 (MSX1) acts exclusively in collateral arterial endothelium to transduce the extrinsic shear stimulus into an arteriogenic remodeling response. MSX1 was specifically up-regulated in remodeling collateral arteries. MSX1 induction in collateral endothelial cells (ECs) was shear stress driven and downstream of canonical bone morphogenetic protein-SMAD signaling. Flow recovery and collateral remodeling were significantly blunted in EC-specific Msx1/2 knockout mice. Mechanistically, MSX1 linked the arterial shear stimulus to arteriogenic remodeling by activating the endothelial but not medial layer to a proinflammatory state because EC but not smooth muscle cellMsx1/2 knockout mice had reduced leukocyte recruitment to remodeling collateral arteries. This reduced leukocyte infiltration in EC Msx1/2 knockout mice originated from decreased levels of intercellular adhesion molecule 1 (ICAM1)/vascular cell adhesion molecule 1 (VCAM1), whose expression was also in vitro driven by promoter binding of MSX1.
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Endotelio Vascular/metabolismo , Hemodinámica/fisiología , Factor de Transcripción MSX1/metabolismo , Músculo Liso Vascular/metabolismo , Transducción de Señal/fisiología , Remodelación Vascular/fisiología , Animales , Proteínas Morfogenéticas Óseas/genética , Proteínas Morfogenéticas Óseas/metabolismo , Endotelio Vascular/citología , Molécula 1 de Adhesión Intercelular/genética , Molécula 1 de Adhesión Intercelular/metabolismo , Factor de Transcripción MSX1/genética , Ratones , Ratones Noqueados , Músculo Liso Vascular/citología , Proteínas Smad/genética , Proteínas Smad/metabolismo , Molécula 1 de Adhesión Celular Vascular/genética , Molécula 1 de Adhesión Celular Vascular/metabolismoRESUMEN
BACKGROUND: The intracellular second messenger cGMP protects the heart under pathological conditions. We examined expression of phosphodiesterase 5 (PDE5), an enzyme that hydrolyzes cGMP, in human and mouse hearts subjected to sustained left ventricular (LV) pressure overload. We also determined the role of cardiac myocyte-specific PDE5 expression in adverse LV remodeling in mice after transverse aortic constriction (TAC). METHODOLOGY/PRINCIPAL FINDINGS: In patients with severe aortic stenosis (AS) undergoing valve replacement, we detected greater myocardial PDE5 expression than in control hearts. We observed robust expression in scattered cardiac myocytes of those AS patients with higher LV filling pressures and BNP serum levels. Following TAC, we detected similar, focal PDE5 expression in cardiac myocytes of C57BL/6NTac mice exhibiting the most pronounced LV remodeling. To examine the effect of cell-specific PDE5 expression, we subjected transgenic mice with cardiac myocyte-specific PDE5 overexpression (PDE5-TG) to TAC. LV hypertrophy and fibrosis were similar as in WT, but PDE5-TG had increased cardiac dimensions, and decreased dP/dtmax and dP/dtmin with prolonged tau (P<0.05 for all). Greater cardiac dysfunction in PDE5-TG was associated with reduced myocardial cGMP and SERCA2 levels, and higher passive force in cardiac myocytes in vitro. CONCLUSIONS/SIGNIFICANCE: Myocardial PDE5 expression is increased in the hearts of humans and mice with chronic pressure overload. Increased cardiac myocyte-specific PDE5 expression is a molecular hallmark in hypertrophic hearts with contractile failure, and represents an important therapeutic target.
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Cardiomegalia/enzimología , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 5/metabolismo , Miocitos Cardíacos/enzimología , Remodelación Ventricular , Animales , Estenosis de la Válvula Aórtica/complicaciones , Calcio/metabolismo , Cardiomegalia/etiología , GMP Cíclico/metabolismo , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 5/genética , Matriz Extracelular , Expresión Génica , Ventrículos Cardíacos/enzimología , Hemodinámica , Humanos , Ratones , Miocitos Cardíacos/metabolismo , ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico/genética , ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico/metabolismo , Factores de TiempoRESUMEN
There is a need for comparative studies to determine which cell types are better candidates to remedy ischemia. Here, we compared human AC133(+) cells and multipotent adult progenitor cells (hMAPC) in a mouse model reminiscent of critical limb ischemia. hMAPC or hAC133(+) cell transplantation induced a significant improvement in tissue perfusion (measured by microPET) 15 days posttransplantation compared to controls. This improvement persisted for 30 days in hMAPC-treated but not in hAC133(+)-injected animals. While transplantation of hAC133(+) cells promoted capillary growth, hMAPC transplantation also induced collateral expansion, decreased muscle necrosis/fibrosis, and improved muscle regeneration. Incorporation of differentiated hAC133(+) or hMAPC progeny into new vessels was limited; however, a paracrine angio/arteriogenic effect was demonstrated in animals treated with hMAPC. Accordingly, hMAPC-conditioned, but not hAC133(+)-conditioned, media stimulated vascular cell proliferation and prevented myoblast, endothelial, and smooth muscle cell apoptosis in vitro. Our study suggests that although hAC133(+) cell and hMAPC transplantation both contribute to vascular regeneration in ischemic limbs, hMAPC exert a more robust effect through trophic mechanisms, which translated into collateral and muscle fiber regeneration. This, in turn, conferred tissue protection and regeneration with longer term functional improvement.