Zebrafish have the ability to regenerate skeletal structures, including the fin, skull roof, and jaw. Although fin regeneration proceeds by epimorphic regeneration, it remains unclear whether this process is involved in other skeletal regeneration in zebrafish. Initially in epimorphic regeneration, the wound epidermis covers the wound surface. Subsequently, the blastema, an undifferentiated mesenchymal mass, forms beneath the epidermis. In the present study, we re-examined the regeneration of the zebrafish lower jaw in detail, and investigated whether epimorphic regeneration is involved in this process. We performed amputation of the lower jaw at two different positions; the proximal level (presence of Meckel's cartilage) and the distal level (absence of Meckel's cartilage). In both manipulations, a blastema-like cellular mass was initially formed. Subsequently, cartilaginous aggregates were formed in this mass. In the proximal amputation, the cartilaginous aggregates were then fused with Meckel's cartilage and remained as a skeletal component of the regenerated jaw, whereas in the distal amputation, the cartilaginous aggregates disappeared as regeneration progressed. Two molecules that were observed during epimorphic regeneration, Laminin and msxb, were expressed in the regenerating lower jaw, although the domain of msxb expression was out of the main plain of the aggregate formation. Administration of an inhibitor of Wnt/β-catenin signaling, a pathway associated with epimorphic regeneration, showed few effects on lower jaw regeneration. Our finding suggests that skeletal regeneration of the lower jaw mainly progresses through tissue regeneration that is dependent on the position in the jaw, and epimorphic regeneration plays an adjunctive role in this regeneration.

中文翻译：

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斑马鱼下颌修复过程中的组织再生表现出表观再生的某些特征。

斑马鱼具有再生骨骼结构的能力，包括鳍，颅骨顶和颌骨。尽管鳍的再生是通过表观再生进行的，但尚不清楚该过程是否参与了斑马鱼的其他骨骼再生。最初在表观再生中，伤口表皮覆盖伤口表面。随后，表皮下形成胚泡，即未分化的间充质。在本研究中，我们详细地检查了斑马鱼下颌的再生，并研究了表观再生是否与该过程有关。我们在两个不同的位置截肢了下颌；近端水平（存在Meckel软骨）和远端水平（不存在Meckel软骨）。在这两种操作中，最初形成胚泡样细胞团。随后，在该团块中形成软骨聚集体。然后在近端截肢中，将软骨聚集体与梅克尔软骨融合，并保留为再生颌骨的骨骼成分，而在远端截肢中，随着再生的进行，软骨聚集体消失。尽管msxb表达域不在聚集体形成的主要平原上，但在表观再生期间观察到的两个分子层粘连蛋白和msxb在再生的下颌中表达。Wnt /β-catenin信号传导抑制剂（一种与表观再生有关的途径）的给药对下颌再生几乎没有影响。