The thymus and tail regenerative capacity in Xenopus laevis tadpoles

2013

Journal of Morphology

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Xenopus froglets can perfectly heal skin wounds without scarring. To explore whether this capacity is maintained as development proceeds, we examined the cellular responses during the repair of skin injury in 8- and 15-month-old Xenopus laevis. The morphology and sequence of healing phases (i.e., inflammation, new tissue formation, and remodeling) were independent of age, while the timing was delayed in older frogs. At the beginning of postinjury, wound re-epithelialization occurred in form of a thin epithelium followed by a multilayered epidermis containing cells with apoptotic patterns and keratinocytes stained by anti-inducible nitric oxide synthase (iNOS) antibody. The inflammatory response, early activated by recruitment of blood cells immunoreactive to anti-tumor necrosis factor (TNF)-α, iNOS, transforming growth factor (TGF)-β1, and matrix metalloproteinase (MMP)-9, persisted over time. The dermis repaired by a granulation tissue with extensive angiogenesis, inflammatory cells, fibroblasts, and anti-α-SMA positive myofibroblasts. As the healing progressed, wounded areas displayed vascular regression, decrease in cellularity, and rearrangement of provisional matrix. The epidermis restored to a prewound morphology while granulation tissue was replaced by a fibrous tissue in a scar-like pattern. The quantitative PCR analysis demonstrated an up-regulated expression of Xenopus suppressor of cytokine signaling 3 (XSOCS-3) and Xenopus transforming growth factor-β2 (XTGF-β2) soon after wounding and peak levels were detected when granulation tissue was well developed with a large number of inflammatory cells. The findings indicate that X. laevis skin wound healing occurred by a combination of regeneration (in epidermis) and repair (in dermis) and, in contrast to froglet scarless wound healing, the growth to a more mature adult stage is associated with a decrease in regenerative capacity with scar-like tissue formation.

Section: Introductionmentioning

confidence: 99%

Skin wound healing in different aged Xenopus laevis

Bertolotti

Malagoli

2013

Journal of Morphology

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“…In Xenopus adults, the thymus activity seemed to be stimulated and T-lymphocytes were detected during tissue maturation T lymphocyte infiltration into wound connective tissue [27]. In contrast, the histological patterns observed in the thymus from tadpoles undergoing metamorphosis, whose potential to regenerate a correctly patterned tail declined, were correlated to a reduced organ functionality [28,29]. It is likely that at different stages of Xenopus development distinct molecular and cellular mechanisms may be involved in the progressive loss of regenerative ability.…”

Section: The Adaptive Immune Response In Tissue Repairmentioning

confidence: 99%

Adaptive immunity and skin wound healing in amphibian adults

2019

Open Life Sciences

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Regeneration and repair with scarring of the skin are two different responses to tissue injury that proceed depending on the animal species. Several studies in multiple organisms have shown that the effectiveness of tissue repair gradually decreases with age in most vertebrates, while the molecular and cellular mechanisms underlying the diverse potentials remain incompletely understood. It is clear, however, that immune system actively participates in the whole process and immune-related activities can mediate both negative and positive roles to influence the quality and diversity of tissue response to damage. Compared with innate immunity, our understanding of the significance of adaptive immune cells in normal repair outcome is limited and deserves further investigation. Here, experimental evidence supporting the contribution of lymphocytes and the involvement of lymphoid organs in skin wound healing are discussed, focusing on the findings emerged in adult amphibians, key animal models for tissue repair and regeneration research.

“…(Franchini and Bertolotti, ). In contrast, the decline of regenerative potential to form a new, complete and correctly patterned tail in tadpoles undergoing metamorphosis was correlated to an impairment in thymic function (Franchini and Bertolotti, ). The findings suggest that distinct pathways and mechanisms could be involved in the decline of regenerative potential during Xenopus development (Franchini and Bertolotti, ).…”

Section: Introductionmentioning

confidence: 99%

The spleen and skin wound healing in Xenopus adults

Rocca

Bertolotti

2016

Journal of Morphology

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In most vertebrates, the regenerative capacity to restore lost/damage tissues to original structure and functionality decreases at some time during ontogenesis. To evaluate the role of the acquired immunity in the decline of regenerative potential, we examined the cellular responses elicited in the spleen during skin repair in Xenopus adults. Modifications in the architecture were found to be induced and were remarkable 14 days postinjury when the spleen increased significantly in size. In white pulp, the periarteriolar lymphoid sheaths were associated with follicles having central light zones, morphologically similar to germinal centers. With the progress of healing, pigment-containing cells were seen to accumulate in both white and red pulp regions. Moreover, compared to controls, the cells immunoreactive to anti-cytokines (TNF-α, TGF-β1) and -iNOS increased from the first days after wounding. The 14th day, the positive cells formed a dense network of reticular cells in central regions of lymphoid follicles and more frequent reactive leukocytes were detected within the red pulp. A higher number of lymphoid cells immunostained with anti-CD3ε were also observed in the perifollicular zone. The results suggest that the spleen of adult frogs is involved in skin wound healing with the expansion of lymphoid compartments. J. Morphol. 277:888-895, 2016. © 2016 Wiley Periodicals, Inc.