Wound healing in Atlantic spiny dogfish sharks.

Field observations and limited experimental studies indicate that elasmobranchs can repair substantial skin injuries, but the temporal course and cellular composition of wound healing in Atlantic spiny dogfish remain poorly characterized. We conducted an exploratory laboratory study in 20 female Atlantic spiny dogfish (Squalus acanthias) using standardized full-thickness skin wounds monitored by serial photography for 35 days, histological analysis at defined post-injury time points, and pooled single-nucleus RNA sequencing of intact and wounded skin. A continuous neoepithelial layer covered all examined wound beds by Day 1, whereas macroscopic wound area decreased progressively over 35 days and dermal denticles remained absent from the repaired surface. Histological examination showed progressive neoepidermal maturation, basement-membrane reformation, collagen deposition, and granulation-tissue organization, indicating that epithelial coverage preceded restoration of normal skin architecture. Single-nucleus RNA sequencing identified epithelial, stromal, vascular, pigment, neural, and immune-cell populations. T and B cells were detected in intact skin, and their relative abundance, together with that of several other leukocyte populations, increased at Day 1 and generally declined by Day 14. Because samples were pooled by time point, these transcriptomic changes are descriptive. These findings characterize rapid early reepithelialization followed by slower tissue remodeling in Atlantic spiny dogfish and provide a foundation for future comparative studies of elasmobranch skin repair.