RESUMO
Angiogenesis is a multistep process that requires highly regulated endothelial cell (EC) behavior. The transcription factor Krüppel-like factor 4 (KLF4) is a critical regulator of several basic EC functions; we have recently shown that KLF4 disturbs pathological (tumor) angiogenesis by mediating the expression of members of VEGF and Notch signaling pathways. Notch signaling is central to orchestration of sprouting angiogenesis but little is known about the upstream regulation of Notch itself. To determine the role of KLF4 in normal (developmental) angiogenesis, we used a mouse retinal angiogenesis model. We found that endothelial-specific overexpression of KLF4 in transgenic mice (EC-K4 Tg) leads to increased vessel density, branching and number of tip cell filopodia as assessed on postnatal day 6 (P6). The hypertrophic vasculature seen with sustained KLF4 overexpression is not stable and undergoes prominent remodeling during P7-P12 resulting in a normal appearing retinal vasculature in adult EC-K4 Tg mice. We find that KLF4 inhibits Delta-like 4 (DLL4) expression in the angiogenic front during retinal vascular development. Furthermore, in an oxygen-induced retinopathy model, overexpression of KLF4 results in decreased vaso-obliteration and neovascular tuft formation that is similar to genetic or pharmacologic DLL4 inhibition. Mechanistically, we show that KLF4 disables the activity of the essential Notch transcriptional activator RBP-J by interfering with binding of co-activators NICD and MAML at intron 3 of the Notch ligand DLL4. In summary, our experimental results demonstrate a regulatory role of KLF4 in developmental angiogenesis through regulation of DLL4 transcription.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas de Ligação ao Cálcio/genética , Fatores de Transcrição Kruppel-Like/fisiologia , Neovascularização Fisiológica/genética , Vasos Retinianos/crescimento & desenvolvimento , Fatores de Transcrição/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Proteínas de Ligação a DNA/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Células Endoteliais da Veia Umbilical Humana , Humanos , Proteína de Ligação a Sequências Sinal de Recombinação J de Imunoglobina/metabolismo , Inteínas/genética , Fator 4 Semelhante a Kruppel , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Complexos Multiproteicos/metabolismo , Ligação Proteica , Estabilidade Proteica , Receptor Notch1/metabolismo , Ativação Transcricional/genéticaAssuntos
Comportamento de Escolha , Coerção , Apego ao Objeto , Psicologia do Self , Comportamento Aditivo/psicologia , Humanos , Relações Interpessoais , Vida , Masculino , Modelos Psicológicos , Autonomia Pessoal , Relações Profissional-Paciente , Teoria Psicanalítica , Terapia Psicanalítica , Processos PsicoterapêuticosRESUMO
RATIONALE: Exogenous stem cell delivery is under investigation to prevent and treat cardiac dysfunction. It is less studied as to the extent endogenous bone marrow derived stem cells contribute to cardiac homeostais in response to stress and the affects of aging on this stress response. OBJECTIVE: To determine the role of bone marrow (BM) derived stem cells on cardiac homeostasis in response to pressure overload (PO) and how this response is altered by aging. METHODS AND RESULTS: Young (8 weeks) and old (>40 weeks) C57/b6 mice underwent homo- and heterochronic BM transplantation prior to transverse aortic constriction (TAC). We found that older BM is associated with decreased cardiac function following TAC. This decreased function is associated with decrease in BM cell engraftment, increased myocyte apoptosis, decreased myocyte hypertrophy, increased myocardial fibrosis and decreased cardiac function. Additionally, there is a decrease in activation of resident cells within the heart in response to PO in old mice. Interestingly, these effects are not due to alterations in vascular density or inflammation in response to PO or differences in ex vivo stem cell migration between young and old mice. CONCLUSIONS: BM derived stem cells are activated in response to cardiac PO, and the recruitment of BM derived cells are involved in cardiac myocyte hypertrophy and maintenance of function in response to PO which is lost with aging.