Papp Tamas, Ferenczi Zsuzsanna, Szilagyi Bernadette, Petro Matyas, Varga Angelika, Kókai Eva, Berenyi Ervin, Olah Gabor, Halmos Gabor, Szucs Peter, Meszar Zoltan
Department of Medical Imaging, University of Debrecen, Debrecen, Hungary.
Department of Anatomy, Histology and Embryology, University of Debrecen, Debrecen, Hungary.
Front Neurosci. 2022 Mar 17;16:803356. doi: 10.3389/fnins.2022.803356. eCollection 2022.
Neuronal differentiation and synaptogenesis are regulated by precise orchestration of intrinsic and extrinsic chemical and mechanical factors throughout all developmental steps critical for the assembly of neurons into functional circuits. While ultrasound is known to alter neuronal migration and activity acutely, its chronic effect on neuronal behavior or morphology is not well characterized. Furthermore, higher-frequency (3-5 MHz) ultrasound (HFU) is extensively used in gynecological practice for imaging, and while it has not been shown harmful for the developing brain, it might be associated with mild alterations that may have functional consequences. To shed light on the neurobiological effects of HFU on the developing brain, we examined cortical pyramidal cell morphology in a transgenic mouse model, following a single and short dose of high-frequency ultrasound. Layer V neurons in the retrosplenial cortex of mouse embryos were labeled with green and red fluorescent proteins by electroporation at the time of their appearance (E14.5). At the time of their presumptive arrival to layer V (E18.5), HFU stimulation was performed with parameters matched to those used in human prenatal examinations. On the third postnatal day (P3), basic morphometric analyses were performed on labeled neurons reconstructed with Neurolucida. Low-intensity HFU-treated cells showed significantly increased dendritic branching compared to control (non-stimulated) neurons and showed elevated c-fos immunoreactivity. Labeled neurons were immunopositive for the mechanosensitive receptor TRPC4 at E18.5, suggesting the role of this receptor and the associated signaling pathways in the effects of HFU stimulation.
神经元分化和突触形成在神经元组装成功能回路的所有关键发育步骤中，受到内在和外在化学及机械因素的精确调控。虽然已知超声波会急性改变神经元迁移和活动，但其对神经元行为或形态的慢性影响尚未得到充分表征。此外，高频（3 - 5兆赫）超声波（HFU）在妇科实践中广泛用于成像，虽然尚未显示对发育中的大脑有害，但它可能与一些可能产生功能后果的轻微改变有关。为了阐明HFU对发育中大脑的神经生物学影响，我们在转基因小鼠模型中，在单次短剂量高频超声处理后，检查了皮质锥体细胞形态。在小鼠胚胎脾后皮质的V层神经元出现时（E14.5），通过电穿孔用绿色和红色荧光蛋白进行标记。在它们预计到达V层时（E18.5），以与人类产前检查所用参数匹配的参数进行HFU刺激。在出生后第三天（P3），对用Neurolucida重建的标记神经元进行基本形态计量分析。与对照（未刺激）神经元相比，低强度HFU处理的细胞显示树突分支显著增加，并且c-fos免疫反应性升高。在E18.5时，标记神经元对机械敏感受体TRPC4呈免疫阳性，表明该受体及相关信号通路在HFU刺激效应中的作用。
