Garcia-Suarez O, Germanà G, Naves F J, Ciriaco E, Represa J, Vega J A
Departamento de Morfología y Biología Celular, Facultad de Medicina, Universidad de Oviedo, Spain.
Anat Rec. 1997 Mar;247(3):299-306. doi: 10.1002/(SICI)1097-0185(199703)247:3<299::AID-AR1>3.0.CO;2-Q.
The medial wall of the vomeronasal organ (VNO) is lined with a sensory epithelium that is closely related to the olfactory epithelium, which is developed from the olfactory placode. It undergoes continuous replacement during its life span. In other sensory epithelia, cell proliferation is under the control of some trophic factors. Whether these proteins are involved in the continuous turnover of the VNO epithelium is unknown. This study approaches this topic by analyzing the occurrence of signal-transducing receptor proteins for neurotrophins (Trk proteins) and epidermal growth factor (EGFr).
VNO samples were obtained from adult horses (n = 9) and processed for Western blot or immunohistochemical detection of TrkA, TrkB, TrkC, and EGFr. For immunohistochemistry, both frozen and formalin-fixed, paraffin-embedded sections were used. Antibodies against Trk proteins were polyclonal antibodies that map within the intracytoplasmic domain. Antibodies against EGFr were monoclonal antibodies that map within the external (clone EGFR1) or the cytoplasmic (clone F4) domains.
TrkA-like, but not TrkB- or TrkC-like, protein was detected in the VNO. By using immunoblotting, protein bands of TrkA-like protein with estimated molecular weights of 43-45, 55, and 60 kDa were found. In agreement with these findings, the sensory epithelium lining the VNO displayed strong TrkA-like immunoreactivity. On the other hand, regular protein bands with estimated molecular weights of 100 and 170 kDa, corresponding with immature and full-length EGFr, respectively, were found with the clone F4, whereas the clone EGFR1 was ineffective in detecting EGFr with Western blot analysis. Positive EGFr immunolabelling was observed regularly in the supranuclear pole of the sensory epithelial cells, and the pattern was identical with both antibodies used.
The present results provide evidence for the occurrence of EGFr in the VNO of the adult horse, suggesting a role for their ligands (EGF and transforming growth factor-alpha) in this organ, probably in continuous cell replacement, during the adult life span. However, although immunoreactivity for TrkA-like protein was regularly observed, because the full-length protein was not found, whether or not its putative ligands (nerve growth factor and neurotrophin-3) act on these cells remains to be demonstrated.
犁鼻器（VNO）的内侧壁衬有一层感觉上皮，它与由嗅基板发育而来的嗅上皮密切相关。在其生命周期中，该上皮会不断更新。在其他感觉上皮中，细胞增殖受某些营养因子的控制。这些蛋白质是否参与犁鼻器上皮的持续更新尚不清楚。本研究通过分析神经营养因子（Trk蛋白）和表皮生长因子（EGFr）的信号转导受体蛋白的存在情况来探讨这一话题。
从成年马（n = 9）获取犁鼻器样本，进行蛋白质免疫印迹或免疫组织化学检测TrkA、TrkB、TrkC和EGFr。对于免疫组织化学，使用了冷冻切片和福尔马林固定、石蜡包埋切片。针对Trk蛋白的抗体是在胞质域内定位的多克隆抗体。针对EGFr的抗体是在外部（克隆EGFR1）或细胞质（克隆F4）域内定位的单克隆抗体。
在犁鼻器中检测到TrkA样蛋白，但未检测到TrkB样或TrkC样蛋白。通过蛋白质免疫印迹，发现了估计分子量为43 - 45 kDa、55 kDa和60 kDa的TrkA样蛋白条带。与这些发现一致，犁鼻器内衬的感觉上皮显示出强烈的TrkA样免疫反应性。另一方面，使用克隆F4发现了估计分子量分别为100 kDa和170 kDa的规则蛋白条带，分别对应未成熟和全长的EGFr，而克隆EGFR1在蛋白质免疫印迹分析中无法有效检测到EGFr。在感觉上皮细胞的核上极经常观察到阳性EGFr免疫标记，并且使用的两种抗体的标记模式相同。
目前的结果为成年马犁鼻器中存在EGFr提供了证据，表明其配体（表皮生长因子和转化生长因子-α）在该器官中可能发挥作用，可能参与成年期的持续细胞更新。然而，尽管经常观察到TrkA样蛋白的免疫反应性，但由于未发现全长蛋白，其假定配体（神经生长因子和神经营养因子-3）是否作用于这些细胞仍有待证实。
