The axolotl (Ambystoma mexicanum) is renowned for its remarkable regenerative capabilities, which are not diminished by the transition from a neotenic to a metamorphic state. This study explored the microbiome dynamics in axolotl limb regeneration by examining the microbial communities present in neotenic and metamorphic axolotls at two critical stages of limb regeneration: pre-amputation and during blastema formation. Utilizing 16S rRNA amplicon sequencing, we investigated the variations in microbiome profiles associated with different developmental and regenerative states. Our findings reveal a distinct separation in the microbiome profiles of neotenic and metamorphic samples, with a clear demarcation in microbial composition at both the phylum and genus levels. In neotenic 0DPA samples, Proteobacteria and Firmicutes were the most abundant, whereas in neotenic 7DPA samples, Proteobacteria and Bacteroidetes dominated. Conversely, metamorphic samples displayed a higher abundance of Firmicutes and Bacteroidetes at 0DPA and Proteobacteria and Firmicutes at 7DPA. Alpha and beta diversity analyses, along with dendrogram construction, demonstrated significant variations within and between the sample groups, suggesting a strong influence of both developmental stage and regenerative state on the microbiome. Notably, Flavobacterium and Undibacterium emerged as distinctive microbial entities in neotenic 7DPA samples, highlighting potential key players in the microbial ecology of regeneration. These findings suggest that the axolotl\'s microbiome is dynamically responsive to blastema formation, and they underscore the potential influence of microbial communities on the regeneration process. This study lays the groundwork for future research into the mechanisms by which the microbiome may modulate regenerative capacity.

暂无摘要。

Salamanders show unparalleled capacities of tissue regeneration amongst tetrapods (four-legged vertebrates), being able to repair and renew lost or damage body parts, such as tails, jaws, and limbs in a seemingly perfect fashion. Despite countless studies on axolotl (Ambystoma mexicanum) regeneration, only a few studies have thus far compared gross morphological and histological features of the original and regenerated limb skeleton. Therein, most studies have focused on nerves or muscles, while even fewer have provided detailed information about bones and cartilage. This study compares skeletal tissue structures of original and regenerated limbs with respect to tissue level histology. Histological serial sections of 55 axolotl larvae were generated, including 29 limbs that were severed by conspecifics, and 26 that were subject to targeted amputations. Amputations were executed in several larval stages (48, 52, and 53) and at different limb positions (humeral midshaft, above the mesopod). In addition, 3D reconstructions were prepared based on X-ray microtomography scans. The results demonstrate that regenerated forelimbs show a diversity of limb and digit abnormalities as a result of imperfect regeneration. Furthermore, abnormalities were more severe and more frequent in regenerated forelimbs caused by natural bites as compared with regenerated forelimbs after amputation. The results indicate that abnormalities occur frequently after regeneration in larval axolotls contradicting the notion of regeneration generally resulting in perfect limbs.

Ambystoma mexicanum kept as pets are affected by a variety of diseases. However, no reports regarding the incidence of specific diseases are available. This study aimed to identify the diseases that occur frequently in this species by surveying the incidence of conditions in pet A. mexicanum specimens brought to a veterinary hospital. The sample comprised 97 pet A. mexicanum individuals brought to the authors\' hospital during the 82-month period, i.e., from January 2008 to October 2014. In total, 116 diseases were identified. The most common disease was hydrocoelom (32 cases; 27.5% of all cases). Elucidating the pathogenesis of hydrocoelom, which has a high prevalence rate, is vital to maintaining the long-term health of A. mexicanum pets.

Correct selection of an appropriate animal mode to closely mimic human extremity diseases or to exhibit desirable phenotypes of limb regeneration is the first critical step for all scientists in biomedical and regenerative researches. The commonly-used animals in limb regeneration and repairing studies, such as axolotl, mice, and rats, are discussed in the review and other models including cockroaches, dogs, and horses are also mentioned. The review weighs the general advantages, disadvantages, and precedent uses of each model in the context of limb and peripheral injury and subsequent regeneration. We hope that this review can provide the reader an overview of each model, from which to select one for their specific purpose.