How do Olfactory Reserve Stem Cells Differentiate into Neuronal Cells? – A Combined in vitro/in vivo Approach

与年龄相关的嗅觉功能障碍影响着80岁以上人口的70%。嗅觉上皮具有独特的再生潜力，因为有两种干细胞：(1)球状基底细胞是再生的第一级细胞，通过不断的神经发生来更新嗅觉上皮；(2)水平基底细胞是休眠的储备干细胞，只有在嗅觉上皮严重损伤时才被激活。在老年性痴呆中，嗅觉感觉神经元和球状基底细胞的丧失导致神经源性衰竭。然而，休眠的水平基底细胞群不能被激活。因此，有意激活水平基底细胞原位是一个有吸引力的治疗目标，在年龄相关的嗅觉功能障碍。先前的研究表明水平基底细胞可以通过下调转录因子p63而被激活。这可以通过外源性维甲酸的管理来实现。然而，即使在成功激活后，活化的乙肝病毒也可以采用四种不同的命运。其中只有一种导致神经元分化为球状基底细胞和嗅觉神经元细胞。因此，这种激活水平基底细胞的治疗方法也需要将干细胞储备推向神经元谱系。随后神经元分化为球状基底细胞和嗅觉神经元细胞的潜在机制在很大程度上仍然是难以捉摸的。这应该通过以下体外/体内联合的方法来阐明：首先，利用免疫组织化学方法评估不同因素对培养的小鼠水平基底细胞分化的影响。在第二步，这种神经源性分化的嗅觉组织将被移植到小鼠宿主嗅觉上皮中。结果也将使用免疫组织化学进行评估。目的是建立体外再生嗅上皮的最佳培养条件，然后将其移植到受损的宿主嗅上皮中。

Age-related olfactory dysfunction affects up to 70% of the population over the age of 80 years. The olfactory epithelium has a distinctive potential to regenerate due to two kinds of stem cells: (1) Globose basal cells which are the first level of regeneration and undergo constant neurogenesis to renew the olfactory epithelium, and (2) horizontal basal cells which are dormant reserve stem cells and only activated in severe damage of the olfactory epithelium. In presbyosmia, the loss of olfactory sensory neurons and globose basal cells leads to a neurogenic exhaustion. However, the population of dormant horizontal basal cells fails to activate. Hence, the deliberate activation of horizontal basal cells in situ is an attractive therapeutic goal in age-related olfactory dysfunction. Previous studies have showed that horizontal basal cells can be activated by downregulation of the transcription factor p63. This can be achieved by the exogenous administration of retinoic acid. However, even after successful activation, the activated HBCs can adopt four different fates. Of them, only one leads to neuronal differentiation into globose basal cells and olfactory neuronal cells. Thus, this therapeutic approach to activate horizontal basal cells also necessitates driving the stem cell reserve toward a neuronal lineage. The underlying mechanisms of the subsequent neuronal differentiation into globose basal cells and olfactory neuronal cells are still largely elusive. This should be elucidated in the following combined in vitro/in vivo approach: First, the effect of different factors on the differentiation will be assessed in cultured murine horizontal basal cells using immunohistochemistry. In a second step this neurogenically differentiated olfactory tissue will be transplanted into a murine host olfactory epithelium. The outcome will also be assessed using immunohistochemistry, too. The aim is to establish optimal culture conditions to regenerate olfactory epithelium in vitro which then can be transplanted into a damaged host olfactory epithelium.