Center for Cellular and Molecular Engineering, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219.
Medical Scientist Training Program, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213.
Proc Natl Acad Sci U S A. 2018 Aug 28;115(35):E8256-E8265. doi: 10.1073/pnas.1803780115. Epub 2018 Aug 13.
While lizards and salamanders both exhibit the ability to regenerate amputated tails, the outcomes achieved by each are markedly different. Salamanders, such as , regenerate nearly identical copies of original tails. Regenerated lizard tails, however, exhibit important morphological differences compared with originals. Some of these differences concern dorsoventral patterning of regenerated skeletal and spinal cord tissues; regenerated salamander tail tissues exhibit dorsoventral patterning, while regrown lizard tissues do not. Additionally, regenerated lizard tails lack characteristically roof plate-associated structures, such as dorsal root ganglia. We hypothesized that differences in neural stem cells (NSCs) found in the ependyma of regenerated spinal cords account for these divergent regenerative outcomes. Through a combination of immunofluorescent staining, RT-PCR, hedgehog regulation, and transcriptome analysis, we analyzed NSC-dependent tail regeneration. Both salamander and lizard Sox2 NSCs form neurospheres in culture. While salamander neurospheres exhibit default roof plate identity, lizard neurospheres exhibit default floor plate. Hedgehog signaling regulates dorsalization/ventralization of salamander, but not lizard, NSCs. Examination of NSC differentiation potential in vitro showed that salamander NSCs are capable of neural differentiation into multiple lineages, whereas lizard NSCs are not, which was confirmed by in vivo spinal cord transplantations. Finally, salamander NSCs xenogeneically transplanted into regenerating lizard tail spinal cords were influenced by native lizard NSC hedgehog signals, which favored salamander NSC floor plate differentiation. These findings suggest that NSCs in regenerated lizard and salamander spinal cords are distinct cell populations, and these differences contribute to the vastly different outcomes observed in tail regeneration.
虽然蜥蜴和蝾螈都具有再生断尾的能力，但它们所达到的结果却明显不同。蝾螈，如 ，再生出与原尾几乎完全相同的复制品。然而，与原尾相比，再生的蜥蜴尾表现出重要的形态差异。其中一些差异涉及再生骨骼和脊髓组织的背腹模式；再生的蝾螈尾组织表现出背腹模式，而再生的蜥蜴组织则没有。此外，再生的蜥蜴尾缺乏与顶盖板相关的特征结构，如背根神经节。我们假设，再生脊髓的室管膜中神经干细胞（NSC）的差异导致了这些不同的再生结果。通过免疫荧光染色、RT-PCR、刺猬调控和转录组分析，我们分析了 NSC 依赖的尾巴再生。蜥蜴和蝾螈的 Sox2 NSCs 在培养中均形成神经球。虽然蝾螈神经球表现出默认的顶盖板特征，但蜥蜴神经球表现出默认的基板特征。刺猬信号调控蝾螈，但不调控蜥蜴 NSCs 的背腹化。体外 NSC 分化潜能的研究表明，蝾螈 NSCs 能够分化为多种神经谱系，而蜥蜴 NSCs 则不能，这通过体内脊髓移植得到了证实。最后，将蝾螈 NSCs 异种移植到再生的蜥蜴尾巴脊髓中，受到了本地蜥蜴 NSC 刺猬信号的影响，这有利于蝾螈 NSCs 基板的分化。这些发现表明，再生的蜥蜴和蝾螈脊髓中的 NSCs 是不同的细胞群体，这些差异导致了尾巴再生中观察到的截然不同的结果。
