Search Results (6)

Segment regeneration in earthworms is a remarkable example of postembryonic morphogenesis, yet its fidelity and cellular mechanisms remain incompletely understood. The present study investigated posterior segment regeneration in adult specimens of the earthworm model Eisenia andrei from wound closure to the 5th postoperative week using anatomical, histological, and ultrastructural approaches. Rapid wound closure occurred through fusion of the cut edges of the body wall and midgut without direct involvement of coelomocytes. The regeneration blastema consisted of dedifferentiated epithelial and muscle cells, innervated by fibers from the last intact ventral nerve cord ganglion. Coelomocytes accumulated in the last intact segments and were primarily involved in debris clearance. Notably, early regenerating tissues lacked collagen fibers, which appeared only after the third postoperative week and remained sparse until the fifth week, whereas original segments exhibited intense, region-specific collagen deposition. Transmission electron microscopy revealed characteristic cytological changes in distinct stages of body wall regeneration, including muscle dedifferentiation and the emergence of collagen-producing fibroblasts. These findings indicate that early cell migration, proliferation, and orientation in the blastema proceed independently of collagen and that collagen functions as a delayed structural scaffold, supporting tissue integrity without impeding regeneration. Importantly, no scar formation was observed between old and new tissues, resembling scarless fetal wound healing. Overall, we clarified previously controversial cellular mechanisms and propose a new, comprehensive model for the early stages of segment regeneration. Our results highlight that coordinated dedifferentiation, spatiotemporal extracellular remodeling, and delayed collagen deposition underlie effective, scar-free regeneration in earthworms, offering insights into conserved mechanisms of regenerative repair across metazoans and potential strategies for enhancing tissue regeneration in mammals. Full article

Appendage autotomy frequently occurs during the cultivation of Exopalaemon carinicauda, which severely impacts its survival and economic benefits. To investigate the molecular mechanism underlying appendage regeneration in E. carinicauda, this study presents a comparative transcriptome analysis on samples from different stages of appendage regeneration in individuals of the same family of E. carinicauda. A total of 6460 differentially expressed genes (DEGs) were identified between the samples collected at 0 h post-autotomy (D0) and those collected at 18 h post-autotomy (D18h). Additionally, 7740 DEGs were identified between D0 and 14 d post-autotomy (D14d), with 3382 DEGs identified between D18h and D14d. Among them, differentially expressed genes such as EcR, RXR, BMP1, and Smad4 are related to muscle growth or molting and may be involved in the regeneration process. qRT-PCR results revealed that EcBMPR2 was expressed at relatively high levels in the gonad and ventral nerve cord tissues and that the highest level of expression was detected in the regenerative basal tissue at 24 h post-autotomy. In situ hybridization results indicated strong signals of this gene in the cells at the wound site at 72 h post-autotomy. Following knockdown of EcBMPR2, the expression levels of both EcBMPR1B and EcSmad1 were significantly downregulated, and long-term interference with the EcBMPR2 gene resulted in a significantly slower appendage regeneration process compared to the control group. When the downstream transcription factor EcSmad1 was knocked down, the two receptor genes EcBMPR2 and EcBMPR1B were downregulated, whereas EcBMP7 was upregulated. After inhibiting the BMP signaling pathway, the degree of cell aggregation at the autotomy site in the experimental group was significantly lower than that in the control group, the wound healing rate was delayed, and the blastema regeneration time was prolonged from 5 d to 7 d. Collectively, these results indicate that the BMP signaling pathway plays a critical role in the early stages of appendage regeneration in E. carinicauda. This study provides important theoretical insights for understanding limb regeneration in crustaceans. Full article

Newts are excellent vertebrate models for investigating tissue regeneration due to their remarkable regenerative capabilities. To investigate the mRNA and microRNAs (miRNAs) profiles within the blastema niche of regenerating newt limbs, we amputated the limbs of Chinese fire belly newts (Cynops orientalis) and conducted comprehensive analyses of the transcriptome and microRNA profiles at five distinct time points post-amputation (0 hours, 1 day, 5 days 10 days and 20 days). We identified 24 significantly differentially expressed (DE) genes and 20 significantly DE miRNAs. Utilizing weighted gene co-expression network analysis (WGCNA) and gene ontology (GO) enrichment analysis, we identified four genes likely to playing crucial roles in the early stages of limb regeneration: Cemip, Rhou, Gpd2 and Pcna. Moreover, mRNA–miRNA integration analysis uncovered seven human miRNAs (miR-19b-1, miR-19b-2, miR-21-5p, miR-127-5p, miR-150-5p, miR-194-5p, and miR-210-5p) may regulate the expression of these four key genes. The temporal expression patterns of these key genes and miRNAs further validated the robustness of the identified mRNA-miRNA landscape. Our study successfully identified candidate key genes and elucidated a portion of the genetic regulatory mechanisms involved in newt limb regeneration. These findings offer valuable insights for further exploration of the intricate processes of tissue regeneration. Full article

Across the animal kingdom, lizards are the only amniotes capable of regenerating their lost tail through epimorphosis. Of the many reptiles, the northern house gecko, Hemidactylus flaviviridis, is an excellent model system that is used for understanding the mechanism of epimorphic regeneration. A stage-specific transcriptome profile was generated in the current study following an autotomized tail with the HiSeq2500 platform. The reads obtained from de novo sequencing were filtered and high-quality reads were considered for gene ontology (GO) annotation and pathway analysis. Millions of reads were recorded for each stage upon de novo assembly. Up and down-regulated transcripts were categorized for early blastema (EBL), blastema (BL) and differentiation (DF) stages compared to the normal tail (NT) by differential gene expression analysis. The transcripts from developmentally significant pathways such as FGF, Wnt, Shh and TGF-β/BMP were present during tail regeneration. Additionally, differential expression of transcripts was recorded from biological processes, namely inflammation, cell proliferation, apoptosis and cell migration. Overall, the study reveals the stage-wise transcriptome analysis in conjunction with cellular processes as well as molecular signaling pathways during lizard tail regeneration. The knowledge obtained from the data can be extrapolated to configure regenerative responses in other amniotes, including humans, upon loss of a complex organ. Full article

In humans, injuries and diseases can result in irreversible tissue or organ loss. This well-known fact has prompted several basic studies on organisms capable of adult regeneration, such as amphibians, bony fish, and invertebrates. These studies have provided important biological information and helped to develop regenerative medicine therapies, but important gaps concerning the regulation of tissue and organ regeneration remain to be elucidated. To this aim, new models for studying regenerative biology could prove helpful. Here, the description of the cephalic tentacle regeneration in the adult of the freshwater snail Pomacea canaliculata is presented. In this invasive mollusk, the whole tentacle is reconstructed within 3 months. Regenerating epithelial, connective, muscular and neural components are already recognizable 72 h post-amputation (hpa). Only in the early phases of regeneration, several hemocytes are retrieved in the forming blastema. In view of quantifying the hemocytes retrieved in regenerating organs, granular hemocytes present in the tentacle blastema at 12 hpa were counted, with a new and specific computer-assisted image analysis protocol. Since it can be applied in absence of specific cell markers and after a common hematoxylin-eosin staining, this protocol could prove helpful to evidence and count the hemocytes interspersed among regenerating tissues, helping to unveil the role of immune-related cells in sensory organ regeneration. Full article

Previous studies indicated that Fibroblast Growth Factors (FGFs) are present during tail and early limb regeneration in lizards, but FGFs disappear in the limb that turns into a scar and does not regenerate at 25–40 days post-amputation. Based on these indications, the aim of the present study was to evaluate the influence of administered FGFs on limb regeneration in lizards by injections of FGF1–2 into amputated hind-limbs that were studied between 40 and 70 days post-amputation. Outgrowths of 2.0 to 3.5 mm were produced but they did not develop an autopodium during this period. The skin remained most un-scaled, resembling that of a tail blastema. Four hours before sacrifice, the animals were injected with 5BrdU to study cell proliferation using microscopic and immunofluorescent methods. Histological examination of the outgrowths at 40–70 days of regeneration showed the presence a rod of cartilage (femur), or partially or completely sub-divided into two parts likely corresponding to a tibia and fibula. The regenerated cartilage was in continuity with the transected long bones and was surrounded by a perichondrium and a dense connective tissue, sparse nerves while muscles were reduced or absent. Qualitative observations on 5BrdU-immunolabeling indicated that most proliferating cells were present in the apical wound epidermis, the apical-most perichondrium and in the regenerating scales at 40–60 days post-amputation, but decreased at 70 days. Few 5BrdU-labeled cells were seen in other tissues, including in the regenerated cartilages. The present study indicates that FGF1-2 treatment in lizards mainly stimulate cartilage regeneration and the formation of a thick epidermis with an Apical Epidermal Peg, the epidermal micro-region that favors regeneration. In summary, these results suggest that FGFs treatments on amputated limbs could also be attempted in others amniotes, including mammals. However FGFs are not capable to induce an autopodium, which requires further signaling factors for its formation. Full article