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. ⋯ 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.