Sharaby Ashraf El, Ueda Katsura, Honma Shiho, Wakisaka Satoshi
Department of Oral Anatomy and Developmental Biology, Osaka University Graduate School of Dentistry, Japan.
Arch Histol Cytol. 2006 Dec;69(4):257-72. doi: 10.1679/aohc.69.257.
We studied the earliest stages of the palate in rat embryos using scanning electron microscopy and immunohistochemistry of growth-associated protein-43 (GAP-43) to investigate the role of nerves in the development of the palatal taste buds. Chronological sequences of the palatal gustatory structures revealed characteristic several stages: 1) At embryonic day 13.5 (E13.5), the palatal shelves were widely separated, and no nerves could be observed in the vicinity of their epithelium which was formed of an undifferentiated single cell layer. 2) At E14, intraepithelial GAP-43-immunoreactive fine nerves were first observed along the medial border of the palatal shelves which became several layers thick but still separate along their entire length. 3) At E15, the fusion process resulted in the formation of cranial parts of the soft palate, the epithelium of which was heavily innervated and revealed small fungiform-like papillae devoid of nerves. 4) As the fusion process continued more caudally at E15, there was a substantial increase in palatal innervation and number of fungiform-like papillae. Primordial stages of taste buds were first distinguished in the papillae where they coincided with sparsely distributed GAP-43-immunoreactive nerve fibers. 5) At E16, the whole soft palate was eventually differentiated and attained its definitive morphology. Different stages of taste buds (i.e. pored and non-pored) were recognized, and an extensive subgemmal plexus characteristic for the adult palatal taste buds was observed. 6) Mature taste buds with alpha-gustducin-immunopositive cells were observed at E18, and their numbers increased gradually with age. The present study reveals that the gustatory nerves preceded the development of taste buds in the palate of rats, and therefore may have some roles in the initial induction of taste buds as proposed in lingual taste buds.
我们使用扫描电子显微镜和生长相关蛋白-43（GAP-43）免疫组织化学方法研究了大鼠胚胎腭部的最早阶段，以探讨神经在腭部味蕾发育中的作用。腭部味觉结构的时间序列显示出几个特征阶段：1）在胚胎第13.5天（E13.5），腭突广泛分开，在其由未分化的单细胞层形成的上皮附近未观察到神经。2）在E14时，首次沿着腭突的内侧边缘观察到上皮内GAP-43免疫反应性细神经，此时腭突已增厚至几层，但在其整个长度上仍分开。3）在E15时，融合过程导致软腭头部形成，其上皮有大量神经支配，并显示出无神经的小蘑菇状乳头。4）随着E15时融合过程向更尾侧继续，腭部神经支配和蘑菇状乳头数量大幅增加。味蕾的原始阶段首先在乳头中被区分出来，它们与稀疏分布的GAP-43免疫反应性神经纤维重合。5）在E16时，整个软腭最终分化并达到其确定的形态。识别出了不同阶段的味蕾（即有孔和无孔），并观察到了成年腭部味蕾特有的广泛的味蕾下丛。6）在E18时观察到具有α-味导素免疫阳性细胞的成熟味蕾，其数量随年龄逐渐增加。本研究表明，味觉神经在大鼠腭部味蕾发育之前出现，因此可能在味蕾的初始诱导中发挥一些作用，就像舌部味蕾所提出的那样。
