PGE2 facilitates tail regeneration via activation of Wnt signaling in Gekko japonicus

The expression pattern of Wnt6, Wnt10A, and HOXA13 during regenerating tails of Gekko Japonicus

Wnt signal is crucial to correctly regenerate tissues along the original axis in many animals. Lizards are able to regenerate their tails spontaneously, while the anterior-posterior axis information required for the successful regeneration is still elusive. In this study, we investigated the expression pattern of Wnt ligands and HOX genes during regeneration. The results of in situ hybridization revealed that Wnt6 and Wnt10A mRNA levels are higher in wound epithelium (WE) than that in blastema during regeneration. In addition, we showed that Wnt agonist positively regulated the expression of HOXA13 in cultured blastema cells, while did not show similar effect on that of HOXB13, HOXC13 and HOXD13. Finally, we found that HOXA13 showed a gradient level along the anterior-posterior axis of regenerated blastema, with higher level at the caudal end. These data proposed that Wnt6, Wnt10A and HOXA13 might play an important role in establishing distal position for regeneration.

Partial in vivo reprogramming enables injury-free intestinal regeneration via autonomous Ptgs1 induction

Tissue regeneration after injury involves the dedifferentiation of somatic cells, a natural adaptive reprogramming that leads to the emergence of injury-responsive cells with fetal-like characteristics. However, there is no direct evidence that adaptive reprogramming involves a shared molecular mechanism with direct cellular reprogramming. Here, we induced dedifferentiation of intestinal epithelial cells using OSKM (Oct4, Sox2, Klf4, and c-Myc) in vivo. The OSKM-induced forced dedifferentiation showed similar molecular features of intestinal regeneration, including a transition from homeostatic cell types to injury-responsive-like cell types. These injury-responsive-like cells, sharing gene signatures of revival stem cells and atrophy-induced villus epithelial cells, actively assisted tissue regeneration following damage. In contrast to normal intestinal regeneration involving Ptgs2 induction, the OSKM promotes autonomous production of prostaglandin E2 via epithelial Ptgs1 expression. These results indicate prostaglandin synthesis is a common mechanism for intestinal regeneration but involves a different enzyme when partial reprogramming is applied to the intestinal epithelium.

Osteoimmunology of Spondyloarthritis

The mechanisms underlying the development of bone damage in the context of spondyloarthritis (SpA) are not completely understood. To date, a considerable amount of evidence indicates that several developmental pathways are crucially involved in osteoimmunology. The present review explores the biological mechanisms underlying the relationship between inflammatory dysregulation, structural progression, and osteoporosis in this diverse family of conditions. We summarize the current knowledge of bone biology and balance and the foundations of bone regulation, including bone morphogenetic protein, the Wnt pathway, and Hedgehog signaling, as well as the role of cytokines in the development of bone damage in SpA. Other areas surveyed include the pathobiology of bone damage and systemic bone loss (osteoporosis) in SpA and the effects of pharmacological treatment on focal bone damage. Lastly, we present data relative to a survey of bone metabolic assessment in SpA from Italian bone specialist rheumatology centers. The results confirm that most of the attention to bone health is given to postmenopausal subjects and that the aspect of metabolic bone health may still be underrepresented. In our opinion, it may be the time for a call to action to increase the interest in and focus on the diagnosis and management of SpA.

Red LED light therapy associated with epidermal growth factor on wound repair process in rats

Epidermal growth factor (EGF) and light-emitting diode (LED) are currently deployed as promissory treatments for skin repair; however, the mechanisms of their association are not yet evidenced. Thus, the present study aimed to evaluate the effects of combined treatment with EGF and red LED on the wound healing processes in rats. Adult Wistar rats were randomized in control group (CG) wounds without treatment; wounds submitted to EGF treatment (EGF); wounds submitted to LED treatment (LED); wounds submitted to EGF associated with LED treatments (EGF/LED). Treatments were performed immediately after the surgical procedure and each 24 h, totaling 8 sessions. Moreover, LED was applied before EGF treatment at a single point in the center of the wound. Morphological characteristics and the immunoexpression of COX-2, VEGF, and TGF-β were measured. The results demonstrated that EGF/LED group presented a higher wound healing index. Additionally, all experimental groups presented similar findings in the histological evaluation, the degree of inflammation, and the area of dermis-like tissue. However, for EGF-treated animals (with or without LED), neoepithelial length was higher. Furthermore, all the treated groups decreased COX-2 and increased VEGF immunoexpression, and only EGF/LED group enhanced the TGF-β protein expression when compared to the untreated group. This research shows that EGF and LED modulate inflammatory process and increase the vascularity. In addition, treatment of EGF associated with LED promoted a more evident positive effect for increasing TGF-β expression and may be promising resources in the clinical treatment of cutaneous wounds.

Akt/mTOR integrate energy metabolism with Wnt signal to influence wound epithelium growth in Gekko Japonicus

The formation of wound epithelium initiates regeneration of amputated tail in Gekko japonicus. Energy metabolism is indispensable for the growth of living creatures and typically influenced by temperature. In this study, we reveal that low temperature lowers energy metabolism level and inhibits the regeneration of amputated tails of Gekko japonicus. We further find that low temperature attenuates the activation of protein kinase B (Akt) and mammalian target of rapamycin (mTOR) in regenerated tissues upon injury signals, and the inhibition of Akt hinders proliferation of the wound epithelium. Additionally, wingless/integrated (Wnt) inhibition suppresses epithelium proliferation and formation by inhibiting Akt activation. Finally, low temperature elevates the activity of adenylate-activated kinase (AMPK) pathway and in turn attenuates wound epithelium formation. Meanwhile, either mTOR downregulation or AMPK upregulation is associated with worse wound epithelium formation. Summarily, low temperature restricts wound epithelium formation by influencing energy sensory pathways including Akt/mTOR and AMPK signaling, which is also modulated by injury induced Wnt signal. Our results provide a mechanism that incorporates the injury signals with metabolic pathway to facilitate regeneration.

Low temperature inhibits the regeneration of amputated tails of Gekko japonicus by influencing the energy sensory Akt/mTOR pathway, which is also modulated by injury-induced Wnt signal.

Bacterial lipopolysaccharides can initiate regeneration of the Xenopus tadpole tail

Tadpoles of the frog Xenopus laevis can regenerate tails except for a short "refractory" period in which they heal rather than regenerate. Rapid and sustained production of ROS by NADPH oxidase (Nox) is critical for regeneration. Here, we show that tail amputation results in rapid, transient activation of the ROS-activated transcription factor NF-κB and expression of its direct target cox2 in the wound epithelium. Activation of NF-κB is also sufficient to rescue refractory tail regeneration. We propose that bacteria on the tadpole's skin could influence tail regenerative outcomes, possibly via LPS-TLR4-NF-κB signaling. When raised in antibiotics, fewer tadpoles in the refractory stage attempted regeneration, whereas addition of LPS rescued regeneration. Short-term activation of NF-κB using small molecules enhanced regeneration of tadpole hindlimbs, but not froglet forelimbs. We propose a model in which host microbiome contributes to creating optimal conditions for regeneration, via regulation of NF-κB by the innate immune system.

The vascularization, innervation and myogenesis of early regenerated tail in Gekko japonicus

Many species of lizards are capable of tail regeneration. There has been increased interest in the study of lizard tail regeneration in recent years as it is an amenable regeneration model for amniotes. In this study, Gekko japonicus was used as a model to investigate the initiation of vascularization, innervation and myogenesis during tail regeneration. We found that angiogenesis and axon regeneration occurred almost simultaneously within 4 days post amputation. The results showed that the endothelial cells of the original vasculature proliferated and extended into the blastema as capillary vessels, which inter-connected to form a capillary network. The nerve fibers innervated the regenerated tissue from the original spinal cord and dorsal root ganglia, and the fiber bundles increased during 14 days. Regenerating muscle tissues emerged 2 weeks after amputation. PAX3 and PAX7 expression were detected during myogenesis, with PAX7 showing a continuous increase in expression from day 3 until the day 14, whereas PAX3 reached a peak level on day 10 day post amputation, and then declined quickly to level as normal control on day 14. PCNA and PAX3 double-positive satellite cells were observed in the original rostral tissues, indicating the involvement of satellite cell proliferation during tail regeneration. Taken together, these data suggest that tail regeneration in Gekko japonicus involved rapid angiogenesis from the beginning to the day 10 and followed by capillary remodeling. The innervation of regenerated tail was significant on day 4 and increased gradually during regeneration, while the regenerated muscle tissues was obvious on day 14 after amputation.