Die Entwicklung eines Embryos und Fetus beeinflusst die Anfälligkeit für kardiovaskuläre Erkrankungen im weiteren Verlauf des Lebens entscheidend. Zugrundeliegende Mechanismen sind jedoch weitestgehend unbekannt. Unter Zuhilfenahme eines neuen Mausmodells für intrauterine kardiale Wachstumsretardierung zielt die vorliegende Dissertation auf die Identifikation adaptiver Wachstumsmechanismen ab, welche die Anpassung der Organgröße und die Aufrechterhaltung einer normalen Herzfunktion ermöglichen. Vielzählige Gene des Aminosäure (AS)-Metabolismus und der Proteinhomeostase zeigten eine vermehrte Expression in neugeborenen Mausherzen nach gestörter Embryonalentwicklung. Es wurde angenommen, dass sowohl die AS-Verfügbarkeit als auch die Aktivität der mechanistic target of rapamycin (mTOR) Signalkaskade entscheidend für eine normale Herzentwicklung und postnatales kompensatorisches Wachstum sind. Der mTOR Komplex 1 (mTORC1) wurde in prä- und perinatalen Mäusen mittels Rapamycin-Behandlung trächtiger Weibchen inhibiert. Die Auswirkungen einer prä- und postnatalen AS-Restriktion wurden anhand einer Niedrigproteindiät untersucht. Rapamycin-behandelte Neugeborene zeichneten sich durch vermindertes Gesamtwachstum sowie Entwicklungsverzögerung aus. Dabei war die kardiale Entwicklung besonders betroffen. Kardiale Proliferationsraten waren nicht verändert, die verminderte Herzgröße wurde jedoch auf eine verringerte Kardiomyozytengröße sowie eine erhöhte Apoptoserate zurückgeführt. Die intrauterine AS-Restriktion wurde überraschend gut von den Mausherzen toleriert. Zusammenfassend konnte gezeigt werden, dass die mTOR Signalkaskade essentiell für eine normale Herzentwicklung sowie kompensatorisches kardiales Wachstum ist. Darüber hinaus stellt die pränatale Rapamycin-Behandlung möglicherweise ein neues Modell der intrauterinen Wachstumsretardierung dar, welches Untersuchungen von Programmierungs-Mechanismen vor allem während der fötalen und perinatalen Herzentwicklung ermöglicht. / Intrauterine development influences the susceptibility to cardiovascular disease in adulthood, although the underlying molecular mechanisms are vastly unknown. Utilizing a new mouse model of impaired heart development, this thesis aims at identifying pre- and postnatal adaptive growth mechanisms to restore organ size and allow normal cardiac function. Unbiased functional annotation of genes differentially expressed in neonatal hearts after impaired intrauterine development revealed numerous gene clusters involved in amino acid (AA) metabolism and protein homeostasis. It was hypothesized that both AA availability and mechanistic target of rapamycin (mTOR) pathway activation are crucial for normal heart development and compensatory cardiac growth. mTOR complex 1 (mTORC1) was inhibited in fetal and neonatal mice by rapamycin treatment of pregnant dams. The effects of pre- and postnatal AA restriction were studied by feeding dams a low protein diet (LPD) throughout pregnancy and keeping the offspring on LPD postnatally. Rapamycin treated neonates were characterized by overall growth restriction and developmental delay, where cardiac development was especially affected (reduction of heart size, weight and heart weight to body weight ratio, severe thinning and noncompaction of the ventricular myocardium as well as immature myocardial morphology). While proliferation rates were unaffected, the reduced neonatal heart size was attributed to decreased cardiomyocyte size and increased apoptosis. Strikingly, the murine heart appeared to be surprisingly resistant to intrauterine AA restriction. In conclusion, the data revealed mTOR being essential for normal as well as compensatory cardiac development and growth. Moreover, prenatal rapamycin treatment might represent a new model of intrauterine growth restriction, which potentially allows the investigation of developmental programming mechanisms within the heart particularly in the fetal and neonatal phase of development.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / O desenvolvimento da programação fetal é considerado um importante fator de risco para doenças não-transmissíveis da vida adulta, incluindo doença cardíaca coronariana. Com o objetivo de investigar a associação entre nutrição materna e o desenvolvimento das artérias coronárias (AC) em embriões de camundongos estadiados; embriões de camundongos C57BL/6 nos estádios de 16-23 foram retirados de mães alimentadas com dietas de proteína normal (NP) ou de baixa proteína (LP), e as AC foram estudadas. Embora os embriões LP possuam massa corporal menor, entretanto tinham taxas de crescimento cardíaco maior, quando comparados com os embriões NP. O Plexo subepicárdico foi observado no início do período pós-somítico (estádio 16) de embriões NP, enquanto que nos embriões LP apenas no estádio 17 (P <0,01), persistindo até o estádio 18 (P <0,01). As artérias coronárias foram detectadas inicialmente no estádio18 dos embriões NP, já nos embriões LP foram encontradas a partir do estádio 19 (P <0,01). Núcleos apoptóticos foram observados em torno do anel aórtico peritruncal no estádio 18 em embriões NP e LP. Células FLK1+ (Fetal Liver Kinase 1 = VEGFr2 = Vascular Endothelial Growth Factor Receptor 2) apresentaram uma distribuição homogênea nos embriões NP já no estádio 18, enquanto uma distribuição semelhante nos embriões LP foi visto apenas nos estádios 22 e 23. A restrição proteica materna em camundongos leva a um atraso no crescimento do coração no período embrionário modificando o desenvolvimento do plexo peritruncal subepicárdica e diminuindo a taxa de apoptose na região do futuro orifício coronariano. / Programming of fetal development is considered to be an important risk factor for non-communicable diseases of adulthood, including coronary heart disease (CHD). Aiming to investigate the association between maternal nutrition and the development of the coronary arteries (CA) in staged mice embryos, C57BL/6 mice embryos from stages 16 to 23 were taken from mothers fed a normal protein (NP) or low protein (LP) diet, and the CA were studied. Although the LP embryos had lower masses, they had faster heart growth rates when compared to the NP embryos. The subepicardial plexuses were observed earlier in the NP embryos (stage 20) than in the LP ones (stage 22) (P<0.01). Apoptotic nuclei were seen around the aortic peritruncal ring beginning at stage 18 in the NP and LP embryos. FLK1+ (fetal liver kinase 1 = VEGFr2 or vascular endothelial growth factor receptor 2) cells had a homogeneous distribution in the NP embryos as early as stage 18, whereas a similar distribution in the LP embryos was only seen at stages 22 and 23. Maternal protein restriction in mice leads to a delay in the growth of the heart in the embryonic period modifying the development of the subepicardial peritruncal plexus and the apoptosis in the future coronary orifice region.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / O desenvolvimento da programação fetal é considerado um importante fator de risco para doenças não-transmissíveis da vida adulta, incluindo doença cardíaca coronariana. Com o objetivo de investigar a associação entre nutrição materna e o desenvolvimento das artérias coronárias (AC) em embriões de camundongos estadiados; embriões de camundongos C57BL/6 nos estádios de 16-23 foram retirados de mães alimentadas com dietas de proteína normal (NP) ou de baixa proteína (LP), e as AC foram estudadas. Embora os embriões LP possuam massa corporal menor, entretanto tinham taxas de crescimento cardíaco maior, quando comparados com os embriões NP. O Plexo subepicárdico foi observado no início do período pós-somítico (estádio 16) de embriões NP, enquanto que nos embriões LP apenas no estádio 17 (P <0,01), persistindo até o estádio 18 (P <0,01). As artérias coronárias foram detectadas inicialmente no estádio18 dos embriões NP, já nos embriões LP foram encontradas a partir do estádio 19 (P <0,01). Núcleos apoptóticos foram observados em torno do anel aórtico peritruncal no estádio 18 em embriões NP e LP. Células FLK1+ (Fetal Liver Kinase 1 = VEGFr2 = Vascular Endothelial Growth Factor Receptor 2) apresentaram uma distribuição homogênea nos embriões NP já no estádio 18, enquanto uma distribuição semelhante nos embriões LP foi visto apenas nos estádios 22 e 23. A restrição proteica materna em camundongos leva a um atraso no crescimento do coração no período embrionário modificando o desenvolvimento do plexo peritruncal subepicárdica e diminuindo a taxa de apoptose na região do futuro orifício coronariano. / Programming of fetal development is considered to be an important risk factor for non-communicable diseases of adulthood, including coronary heart disease (CHD). Aiming to investigate the association between maternal nutrition and the development of the coronary arteries (CA) in staged mice embryos, C57BL/6 mice embryos from stages 16 to 23 were taken from mothers fed a normal protein (NP) or low protein (LP) diet, and the CA were studied. Although the LP embryos had lower masses, they had faster heart growth rates when compared to the NP embryos. The subepicardial plexuses were observed earlier in the NP embryos (stage 20) than in the LP ones (stage 22) (P<0.01). Apoptotic nuclei were seen around the aortic peritruncal ring beginning at stage 18 in the NP and LP embryos. FLK1+ (fetal liver kinase 1 = VEGFr2 or vascular endothelial growth factor receptor 2) cells had a homogeneous distribution in the NP embryos as early as stage 18, whereas a similar distribution in the LP embryos was only seen at stages 22 and 23. Maternal protein restriction in mice leads to a delay in the growth of the heart in the embryonic period modifying the development of the subepicardial peritruncal plexus and the apoptosis in the future coronary orifice region.