Three‐dimensional micro‐MRI analysis of cerebral artery development in mouse embryos

Abstract

Vascular system development involves a complex, three-dimensional branching process that is critical for normal embryogenesis. In the brain, the arterial systems appear to develop in a stereotyped fashion, but no detailed quantitative analyses of the mouse embryonic cerebral arteries have been described. In this study, a gadolinium-based contrast perfusion method was developed to selectively enhance the cerebral arteries in fixed mouse embryos. Three-dimensional magnetic resonance micro-imaging (micro-MRI) data were acquired simultaneously from multiple embryos staged between 10 During mammalian embryogenesis, the vasculature forms as a highly complex three-dimensional (3D) system of interconnected blood vessels that provide the developing tissues with essential nutrients, growth factors, and oxygen. Studies using genetically engineered mice have provided critical data on the genetic and molecular factors controlling vascular development during embryogenesis and also during disease progression involving abnormal formation of blood vessels. In these studies, quantitative 3D analysis of vascular patterns is seldom performed since commonly used histologic methods are inherently two dimensional and prone to sectioning artifacts, making 3D reconstructions difficult. Volumetric imaging methods such as magnetic resonance micro-imaging (micro-MRI) could provide powerful new tools to study vascular patterning in both normal and mutant mouse embryos.Vascular development during embryogenesis can be divided into two key processes: vasculogenesis and angiogenesis. The earliest step, vasculogenesis, involves the recruitment and assembly of endothelial-cell precursors, called angioblasts, into a primary vascular plexus (1). These primitive blood vessels are then extended and elaborated by the process of angiogenesis, which involves cell proliferation, differentiation of the arterial and venous components, and the establishment of the final 3D patterns of the vascular networks (2). While vasculogenesis is a process that occurs only during early embryonic development, angiogenesis is an ongoing process that can also occur after birth, depending on the needs of different tissues, which can be advantageous, as in angiogenesis after ischemia (3), or pathologic, as in tumor angiogenesis (4).The development of the mammalian vasculature results in apparently stereotypical patterns in a number of vascular subsystems, including the cerebral arteries. However 3D vascular patterning during brain development has not been investigated in detail, in large part due to the lack of analytical tools. We are particularly interested in analyzing the 3D patterns of the cerebral arterial inputs and how these patterns change during normal development, and in mouse mutants after genetic alterations that disrupt vascular patterning. The primary vascular inputs into the developing brain are the basilar artery that perfuses the more posterior parts of the brain and the carotid arteries that supply blood to the more anterior brain regions. In this report...

Quantitative T2 Changes and Susceptibility-Weighted Magnetic Resonance Imaging in Murine Pregnancy

“…Traditionally, visualization of the embryonic vascular development using MRI has been accomplished with external contrast agents [66, 67], usually in the ex vivo setting [67–69]. More recently, high-resolution 3-D imaging based on T2* differences as exogenous contrast have been applied to highlight such vasculature [37, 70].…”

High-frequency annular array with coaxial illumination for dual-modality ultrasonic and photoacoustic imaging

“…MRI is the gold standard technique frequently employed to obtain fine-resolution, high-contrast images of the vasculature of the embryonic mouse, but the protocol typically entails injection of MR contrast agents, fixation of the embryo, and scan times that exceed 2 h. Recently, an in vivo MRI protocol was demonstrated to produce vascular maps of relatively good contrast but the scan time lasted approximately 3 h. 23 Aside from their long scan times, MRI systems are cost prohibitive and they require the use of MR-compatible equipment. Our HFU system can acquire single-plane data in <0.2 s and is only limited by the low repetition rate of our laser (10 Hz).…”

Genes into geometry: imaging for mouse development in 3D

“…Figure 7. Vascular-specific developmental time series have also been reported both with MRI [40] and OPT [45 ]. In addition, in vivo measures of physiological function, such as blood velocity and flow pattern have been recorded with UBM, from E14.5 to adulthood, showing developmental changes in ventricular cardiac function [61].…”

“…MRI and CT have been the standard for vascular imaging over large FOVs for sometime. Perfusion of a vascular contrast agent enables vascular phenotyping in the brain [40], kidney [41], placenta [42,43] and lung [44 ] (Figure 4). OPT of the mouse vasculature provides sufficient resolution for visualization of the most dynamic stages of vascular development, between E8.0 and E10.0 in the mouse embryo, showing progression from isolated vascular cells to a complex vascular plexus with subsequent vessel pruning [45 ,46].…”