Research Institute of Human Morphology, 117418, Tsyurupy St., 3, Moscow, Russia.
Moscow Regional Research Institute of Obstetrics and Gynecology, 101000, Pokrovka St., 22A, Moscow, Russia.
J Chem Neuroanat. 2018 Oct;92:61-70. doi: 10.1016/j.jchemneu.2018.06.002. Epub 2018 Jun 9.
The prepiriform cortex is a part of the phylogenetically oldest pallial division (paleocortex) representing the primary olfactory cortex. While olfactory centers in laboratory animals have been extensively investigated, the developmental timetable of the human prepiriform area is poorly understood. Thus, in the present study we aim to examine the prepiriform cortex in human fetuses from eight postconceptional weeks to birth. Based on cytoarchitecture and immunohistochemistry analysis (NeuN-, SYP-, NSE-, TH-, GFAP-, MBP-) four main periods of the prepiriform cortex fetal development are suggested: the beginning of prefetal stage (the eighth week from conception), the period from the ending of prefetal stage (9-12 postconceptional weeks) to 17 weeks of gestation, 18-27 weeks of gestation and the late fetal period (29-40 gestational weeks). We found that the initial layer differentiation took place before the ninthtenth weeks from conception and by ten weeks the paleocortical plate of the prepiriform cortex was shaped. Both total cell density and NeuN-immunoreactive cell density peaked in the early fetuses and started to decrease after 17 gestational weeks, attaining intermediate values at 18-27 weeks and becoming significantly lower in the late fetuses. In contrast, the NeuN-immunoreactive cell ratio gradually increased over the whole examined period. The prepiriform cortex was defined as approaches the state at birth at 30 gestational weeks. The same developmental periods were observed with SYP- and NSE-assays. No significant distribution of TH immunoreactivity was described in the prepiriform cortex of human fetuses. The prior paleocortex development was demonstrated using glial markers: GFAPimmunoreactivity appeared in the prepiriform cortex at the middle of the early fetal period, ahead of the neocortex and insular cortex. The earlier rates of GFAP-immunoreactivity expansion in the prepiriform cortex, as compared to other pallial regions, persisted in the later fetuses. The first MBP-immunoreactive fibres within pallium were detected in the lateral olfactory tract at 30 weeks. Therefore, the prepiriform cortex approaches a level of maturation similar to that at birth already at the beginning of the late fetal period and matures prior to other pallial regions.
梨状皮层是系统发生上最古老的大脑皮层（古皮层）的一部分，代表主要的嗅觉皮层。虽然实验室动物的嗅觉中枢已经得到了广泛的研究，但人类梨状区的发育时间表还知之甚少。因此，在本研究中，我们旨在检查从受孕后 8 周到出生的人类胎儿的梨状皮层。基于细胞构筑和免疫组织化学分析（NeuN、SYP、NSE、TH、GFAP、MBP-），我们提出了梨状皮层胎儿发育的四个主要时期：前胎儿期的开始（受孕后第 8 周）、前胎儿期结束（受孕后 9-12 周）到 17 周妊娠、18-27 周妊娠和晚期胎儿期（29-40 周妊娠）。我们发现，初始层分化发生在受孕后第 9-10 周之前，到第 10 周时，梨状皮层的古皮层板已经形成。总细胞密度和 NeuN 免疫反应性细胞密度在早期胎儿中达到峰值，然后在 17 孕周后开始下降，在 18-27 孕周时达到中间值，在晚期胎儿中显著降低。相反，NeuN 免疫反应性细胞的比例在整个检查期间逐渐增加。在 30 孕周时，梨状皮层接近出生时的状态。用 SYP 和 NSE 检测也观察到了相同的发育时期。在人类胎儿的梨状皮层中没有描述到 TH 免疫反应的显著分布。使用神经胶质标记物证明了前古皮层的发育：GFAP 免疫反应性在早期胎儿的中期出现在梨状皮层中，早于新皮层和岛叶皮层。与其他大脑皮层区域相比，在晚期胎儿中，GFAP 免疫反应性扩张的早期速度持续存在。在 30 孕周时，在外侧嗅束中首次检测到有髓鞘纤维的 MBP 免疫反应性。因此，梨状皮层在晚期胎儿期开始时已经接近出生时的成熟水平，并比其他大脑皮层区域更早成熟。
