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OBJECTIVE While intraventricular hemorrhage (IVH) is associated with posthemorrhagic ventricular dilation (PHVD), not all infants affected by high-grade IVH develop PHVD. The authors aimed to determine clot-associated predictors of PHVD in a porcine model by varying the amount and rate of direct intraventricular injection of whole autologous blood. METHODS Seven 1-week-old piglets underwent craniectomy and injection of autologous blood into the right lateral ventricle. They survived for a maximum of 28 days. MRI was performed prior to injection, immediately postoperatively, and every 7 days thereafter. T1-weighted, T2-weighted, and susceptibility-weighted imaging (SWI) sequences were used to segment ventricular and clot volumes. Spearman correlations were used to determine the relationship between blood and clot volumes and ventricular volumes over time. RESULTS The maximum ventricular volume was up to 12 times that of baseline. One animal developed acute hydrocephalus on day 4. All other animals survived until planned endpoints. The interaction between volume of blood injected and duration of injection was significantly associated with clot volume on the postoperative scan (p = 0.003) but not the amount of blood injected alone (p = 0.38). Initial postoperative and day 7 clot volumes, but not volume of blood injected, were correlated with maximum (p = 0.007 and 0.014) and terminal (p = 0.014 and 0.036) ventricular volumes. Initial postoperative ventricular volume was correlated with maximum and terminal ventricular volume (p = 0.007 and p = 0.014). CONCLUSIONS Initial postoperative, maximum, and terminal ventricular dilations were associated with the amount of clot formed, rather than the amount of blood injected. This supports the hypothesis that PHVD is determined by clot burden rather than the presence of blood products and allows further testing of early clot lysis to minimize PHVD risk.

Intraventricular hemorrhage (IVH) affects approximately 50% of premature births where 50% further develop post-hemorrhagic ventricular dilation (PHVD). Patients face significant impact to long-term development if PHVD is not managed. Unfortunately, there is no accepted treatment to remove the thrombus caused by IVH. This paper describes an acute and chronic IVH model for use with magnetic resonance-guided focused ultrasound (MRgFUS) thrombolysis. A total of 12 pigs (~ 1 month in age) were used in the model (eight acute and four chronic). A pre-operative brain MRI was obtained for ventricular targeting. 1.25 cm3/kg of autologous blood was injected through a burr hole lateral to the midline and anterior of the coronal suture at a rate of 0.6 cm3/min. A craniotomy was performed to simulate a “fontanelle”. Post-operative MRI was used to calculate the clot volume. Chronic piglets were recovered, monitored daily with a neurological scoring system (NSS), and MRI scanned for 21 days. The clot injection was well tolerated. The average clot size was 3987 mm3 (median = 4330 mm, standard deviation = 739 mm3). Postmortem examination validated the presence of the clot. In the chronic animals, there was an increase in ventricular volume of 30%. Transient neurological impairment immediately followed clot injection and with onset of hydrocephalus in the chronic animals. This model establishes a measurable and targetable IVH clot in an MRI-based neonatal porcine model. The progressive post-hemorrhagic ventricular dilation in the chronic model is a potential alterable outcome from MRgFUS thrombolysis.

OBJECTIVE Magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) is a potential noninvasive therapy for fetal conditions. In utero MRgHIFU delivery and proton resonance frequency shift (PRFS) thermometry monitoring will control accuracy of HIFU ablation and confirm in situ tissue heating in a rabbit model. METHODS High-resolution 3T MR images were acquired in late-gestation rabbits (approximately 30 days, n = 5). HIFU sonications, using magnetic resonance (MR) thermometry as a guide, were delivered to achieve necrosis in relevant fetal targets. Thermometry, posttreatment magnetic resonance imaging (MRI), and follow-up histology confirmed ablation. RESULTS Placentas (n = 14) were treated with 127 ± 34 Wac; thermometry-indicated temperatures reached 67°C. Lungs (n = 8) were treated with 85 ± 15 Wac and reached 73°C, livers (n = 6) with 80 ± 15 Wac and reached 74°C, and kidneys (n = 5) with 100 Wac and reached 66°C. Histological changes showed focal areas of necrosis with circumferential hemorrhage and/or vasodilation, which transitioned abruptly to healthy tissue. CONCLUSION MRgHIFU therapy can effectively target and thermally treat specific in utero organs in this acute fetal rabbit model. PRFS gives in situ temperature control of therapy on tissues. Conceivably, MRgHIFU therapy may be applicable to specific fetal organ anomalies clinically and has the potential to improve the overall fetal outcome over traditional invasive surgical procedures.

This study examines aberrant synaptogenesis and myelination of neuronal connections as possible links to neurological sequelae in growth-restricted fetuses. Pregnant guinea pig sows were subjected to uterine blood flow restriction or sham surgeries at midgestation. The animals underwent necropsy at term with fetuses grouped according to body weight and brain-to-liver weight ratios as follows: appropriate for gestational age (n = 12); asymmetrically fetal growth restricted (aFGR; n = 8); symmetrically fetal growth restricted (sFGR; n = 8), and large for gestational age (n = 8). Fetal brains were perfusion fixed and paraffin embedded to determine immunoreactivity for synaptophysin and synaptopodin as markers of synaptic development and maturation, respectively, and for myelin basic protein as a marker for myelination, which was further assessed using Luxol fast blue staining. The most pertinent findings were that growth-restricted guinea pig fetuses exhibited reduced synaptogenesis and synaptic maturation as well as reduced myelination, which were primarily seen in subareas of the hippocampus and associated efferent tracts. These neurodevelopmental changes were more pronounced in the sFGR compared to the aFGR animals. Accordingly, altered hippocampal development involving synaptogenesis and myelination may represent a mechanism by which cognitive deficits manifest in human growth-restricted offspring in later life.

An increasing number of applications use the postnatal piglet model in neuroimaging studies, however, these are based primarily on T1 weighted image templates. There is a growing need for a multimodal structural brain template for a comprehensive depiction of the piglet brain, particularly given the growing applications of diffusion weighted imaging for characterizing tissue microstructures and white matter organization. In this study, we present the first multimodal piglet structural brain template which includes a T1 weighted image with tissue segmentation probability maps, diffusion weighted metric templates with multiple diffusivity maps, and population-based whole-brain fiber tracts for postnatal piglets. These maps provide information about the integrity of white matter that is not available in T1 images alone. The availability of this diffusion weighted metric template will contribute to the structural imaging analysis of the postnatal piglet brain, especially models that are designed for the study of white matter diseases. Furthermore, the population-based whole-brain fiber tracts permit researchers to visualize the white matter connections in the piglet brain across subjects, guiding the delineation of a specific white matter region for structural analysis where current diffusion data is lacking. Researchers are able to augment the tracts by merging tracts from their own data to the population-based fiber tracts and thus improve the confidence of the population-wise fiber distribution.

Key points Suboptimal intrauterine conditions and consequent intrauterine growth reduction (IUGR), resulting in low birth weight (LBW), increase the risk for hypertension and cardiovascular disease in adulthood. LBW offspring who experience an accelerated growth in childhood have a higher risk of cardiovascular disease than those who grow more slowly, suggesting that the postnatal environment interacts with programmed deficits in organ function to influence disease risk. We show here that arterial stiffening in LBW guinea pig offspring is exacerbated with postnatal feeding of a Western diet, suggesting that IUGR confers heightened vascular susceptibility to postnatal risk factors and thus may contribute to an individual's total risk score. Our results also demonstrate that the independent effect of the intrauterine environment on vascular function in young adult guinea pigs is greater than the effect of a postnatal Western diet, thus highlighting the importance of prenatal factors on long-term vascular health. Abstract The association between intrauterine growth restriction (IUGR) and hypertension is well established, yet the interaction between IUGR and other pathogenic contributors remains ill-defined. This study examined the independent and interactive effects of fetal growth reduction resulting in low birth weight (LBW), and postnatal Western diet (WD) on vascular function. Growth reduction was induced in pregnant guinea pigs by uterine artery ablation. LBW and normal birth weight (NBW) offspring were randomly assigned to a control diet (CD) or a WD. In young adulthood, length–tension curves were generated in aortic rings and responses to methacholine (MCh) were evaluated in the carotid and aorta using wire myography. Relative to NBW/CD, aortae of NBW/WD offspring were stiffer, as determined by a leftward shift in the length–tension curve, yet the shift in the LBW/CD curve was considerably greater. Aortic stiffening was most severe in LBW/WD (slope: NBW/CD, 1.97 ± 0.04; NBW/WD, 2.16 ± 0.04; LBW/CD, 2.28 ± 0.05; LBW/WD, 2.34 ± 0.07). Maximal responses (Emax) to MCh were significantly blunted in the aorta of LBW/CD vs. NBW/CD (P

This study determined the effect of chronic intrauterine hypoxia on collagen deposition in the fetal sheep heart. Moderate or severe hypoxia was induced by placental embolization in chronically catheterized fetal sheep for 15 days starting at gestational day 116 ± 2 (term ∼147 days). The fetal right and left ventricle were evaluated for collagen content using a Sirius red dye and for changes in signaling components of pathways involved in collagen synthesis and remodeling using quantitative polymerase chain reaction and Western blot. In severely hypoxic fetuses (n = 6), there was a two-fold increase (P < 0.05) in the percentage staining for collagen in the right ventricle, compared with control (n = 6), whereas collagen content was not altered in the moderate group (n = 4). Procollagen I and III mRNA levels were increased in the right ventricle, two-fold (P < 0.05) and three-fold (P < 0.05), respectively, in the severe group relative to control. These changes were paralleled by a two-fold increase (P < 0.05) in mRNA levels of the pro-fibrotic cytokine, transforming growth factor β (TGF-β1), in the right ventricle. In the right ventricle, the mRNA levels of matrix metalloproteinase 2 (MMP-2) and its activator, membrane-type MMP (MTI-MMP) were increased five-fold (P = 0.06) and three-fold (P < 0.05), respectively, relative to control. Protein levels of TGF-β were increased in the left ventricle (P < 0.05). Thus, up-regulated collagen synthesis leading to increased collagen content occurs in the chronically hypoxic fetal heart and may contribute to the right ventricular diastolic and systolic dysfunction reported in human intrauterine growth restriction fetuses.

This study examined perturbed aortic development and subsequent wall stiffening as a link to later cardiovascular disease. Placental insufficiency was induced in pregnant guinea pigs at midgestation by uterine artery ligation. Near term, fetuses were killed and defined as normal birth weight (NBW), low birth weight (LBW), and intrauterine growth restricted (IUGR). Offspring were classified according to birth weight and killed in adulthood. Collagen and elastin content of aortas were analyzed using Sirius red and orcein staining, respectively. Immunofluorescence was used for detection of α-actin and nonmuscle myosin heavy chain (MHC-B), a marker of synthetic-type vascular smooth muscle cells (VSMCs). Ex vivo generation of length-tension curves was performed with aortic rings from adult offspring. Relative elastic fiber content was decreased by 10% in LBW and 14% in IUGR compared with NBW fetuses. In adulthood, relative elastic fiber content was 51% lower in LBW vs. NBW, and the number of elastic laminae adjusted for wall thickness was 25% lower in LBW ( P < 0.01). The percent area stained for MHC-B was sixfold higher in LBW vs. NBW fetuses ( P < 0.0001) and threefold higher in LBW vs. NBW adult offspring ( P < 0.05). The increase in MHC-B in LBW offspring concurred with a 41% increase in total collagen content and a 33 and 56% increase in relative and total α-actin content, respectively ( P < 0.05). Thus aortic wall stiffening in adulthood can be traced to altered matrix composition established under suboptimal intrauterine conditions that is amplified postnatally by the activity of synthetic VSMCs.