Herein we employ Myh11-CreERT2 ROSA floxed STOP eYFP Apoe−/− smooth muscle cell (SMC) lineage tracing mice to show that traditional methods for detecting SMCs based on immuno-staining fail to detect > 80% of SMC-derived cells within advanced atherosclerotic lesions. These unidentified SMC-derived cells exhibit phenotypes of other cell lineages including macrophages (Mϕs), and mesenchymal stem cells (MSCs). SMC-specific conditional knockout (KO) of Krüppel-like factor 4 (KLF4) resulted in reduced numbers of SMC-derived MSC-, and Mϕ-like cells, marked reductions in lesion size, and increases in multiple indices of plaque stability, including an increase in fibrous cap thickness. Results of in vivo KLF4 ChIP-Seq analyses, and studies in cultured SMC treated with cholesterol identified > 800 KLF4 target genes including many that regulate pro-inflammatory responses of SMC. Results indicate that the contribution of SMCs within atherosclerotic plaques has been greatly underestimated, and that KLF4-dependent transitions in SMC phenotype are critical in lesion pathogenesis.

There are controversial claims that the embryonic stem cell (ESC) pluripotency factor OCT4 is activated in somatic cells, but there is no evidence it plays a functional role in these cells. Herein we demonstrate that smooth muscle cell (SMC)-specific conditional knockout of Oct4 within Apoe−/− mice resulted in increased lesion size and changes consistent with decreased plaque stability including a thinner fibrous cap, increased necrotic core, and increased intra-plaque hemorrhage. Results of SMC-lineage tracing studies showed that these changes were likely due to marked reductions in SMC number within lesions including impaired SMC migration and investment within the fibrous cap. Re-activation of Oct4 within SMCs was associated with hydroxymethylation of the Oct4 promoter and was HIF1α- and KLF4-dependent. Results provide the first direct evidence that OCT4 plays a functional role in somatic cells and highlight the importance of further investigation of possible OCT4 functions in normal and diseased somatic cells.

Rationale We previously identified conserved G/C Repressor elements in the promoters of most SMC marker genes, and demonstrated that mutation of this element within the SM22α promoter nearly abrogated repression of this transgene following vascular wire injury or within lesions of ApoE−/− mice. However, the mechanisms regulating the activity of the G/C Repressor are unknown, although we have previously shown that phenotypic switching of cultured SMC is dependent on Krupple-Like Factor 4. Objective The goals of the present studies were to: 1) injury-induced repression of SM22α gene following vascular injury is mediated through KLF4 binding to the G/C Repressor element; and 2) the transcriptional repressor activity of KLF4 on SMC marker genes is dependent on cooperative binding with pELK-1 and subsequent recruitment of HDAC2 which mediates epigenetic gene silencing. Methods and Results Chromatin immunoprecipitation (ChIP) assays were performed on chromatin derived from carotid arteries of mice having either a wildtype or G/C Repressor mutant SM22α promoter-LacZ transgene. KLF4 and pELK-1 binding to the SM22α promoter was markedly increased following vascular injury and was G/C Repressor dependent. Sequential ChIP assays and proximity ligation analyses in cultured SMC treated with PDGF BB or oxidized phospholipids showed formation of a KLF4, pELK-1, and HDAC2 multi-protein complex dependent upon the SM22α G/C Repressor element. Conclusions Silencing of SMC marker genes during phenotypic switching is partially mediated by sequential binding of pELK-1, and KLF4 to G/C Repressor elements. The pELK-1-KLF4 complex in turn recruits HDAC2 leading to reduced histone acetylation and epigenetic silencing.

High environmental temperature has strong adverse effects on poultry production, welfare, and sustainability and, thereby, constitutes one of the most challenging stressors. Although colossal information has been published on the effects of heat stress on poultry productivity and gut health, the fundamemntal mechanisms associated with heat stress responses and intestinal barrier function are still not well defined. The aim of the present study was, therefore, to determine the effects of acute (2 h) heat stress on growth performance, gut integrity, and intestinal expression of heat shock and tight junction proteins in slow-(broilers of the 1950's, ACRB), moderate-(broilers of 1990's, 95RAN), rapid-(modern broilers, MRB) growing birds, and their ancestor wild jungle fowl (JF). Heat stress exposure significantly increased the core body temperature of 95RAN and MRB chickens by ∼0.5-1 • C, but not that of JF and ACRB compared to their counterparts maintained at thermoneutral conditions. Heat stress also depressed feed intake and increased serum fluorescein isothiocyanate-dextran (FITC-D) levels (P < 0.05) in modern broilers (95RAN and MRB) but not in JF and ACRB, indicating potential leaky gut syndrome. Molecular analyses showed that heat stress exposure significantly up regulated the duodenal expression of occludin (OCLN) and lipocalin (LCN2) in ACRB, zonula occludens (ZO-2), villin1 (VIL1), and calprotectin (CALPR) in 95 RAN, and only CALPR in MRB compared to their TN counterparts. In the jejunum however, heat stress down regulated the expression of PALS1-associated tight junction protein (PATJ) in ACRB, 95RAN, and MRB, and that of cadherin1 (CDH1) in MRB. In the ileum, heat stress significantly down regulated the expression of OCLN in 95 RAN, ZO-1 in MRB, gap junction protein alpha1 (GJA1) in JF, and VIL1 in ACRB compared to their TN counterparts. In summary, this is the first report, to our knowledge, showing that tight junction protein expression is environmental-, genotype-, and intestinal segment-dependent and identifying molecular signatures, such as CDH1, CALPR, and ZO-1, potentially involved in leaky gut syndrome-induced by heat stress in MRB.

UTM and LTM training are equally capable of improving aerobic fitness and body composition in physically inactive overweight individuals, but UTM training may induce increases in LBM.