# Transcriptional Evaluation of Neuropeptides, Hormones, and Tissue Repair Modulators in the Skin of Gilthead Sea Bream (Sparus aurata L.) Subjected to Mechanical Damage

## TL;DR

This study examines how gilthead sea bream skin heals after mechanical damage, finding faster and stronger healing in the ventral region compared to the dorsal region.

## Contribution

The study identifies specific neuroendocrine and tissue repair gene markers modulated by mechanical damage location in gilthead sea bream skin.

## Key findings

- Ventral lesions showed a stronger and faster neuroendocrine and tissue repair response than dorsal lesions.
- Genes like crh, pomca, and penkb were upregulated in ventral injuries but not in dorsal injuries.
- The ventral region's proximity to vital organs may explain its enhanced healing response.

## Abstract

The fish’s skin is the tissue whose total area is in permanent contact with the aquatic environment. Despite its relevance, there are currently very few studies aimed at evaluating tissue repair mechanisms. In this study, we assessed the tissue repair response to mechanical damage in the skin of gilthead sea bream (Sparus aurata), revealing differences in the modulation of neuroimmune–endocrine response gene markers depending on the location of the lesion. Furthermore, wound healing in the ventral region was observed to be higher in magnitude and faster than in the dorsal region. We registered an increase in the expressions of hormone-related genes compared to the dorsal lesion. This research improves our understanding of the neuroendocrine and tissue repair response to mechanical damage in S. aurata. This study provides biologically relevant molecular markers for future studies of tissue repair.

The skin of bony fish is the first physical barrier and is responsible for maintaining the integrity of the fish. Lesions make the skin vulnerable to potential infection by pathogens present in the aquatic environment. In this way, wound repair has barely been studied in gilthead sea bream. Thus, this study investigated the modulation of peripheral neuro-endocrine and tissue repair markers at the transcriptional level in the skin of teleost fish subjected to mechanical damage above or below the lateral line (dorsal and ventral lesions, respectively). Samples were evaluated using RT-qPCR at 2-, 4-, and 20-days post-injury. Fish with a ventral lesion presented a trend of progressive increase in the expressions of corticotropin-releasing hormone (crh), pro-opiomelanocortin-A (pomca), proenkephalin-B (penkb), cholecystokinin (cck), oxytocin (oxt), angiotensinogen (agt), and (less pronounced) somatostatin-1B (sst1b). By contrast, fish with a dorsal lesion registered no significant increase or biological trend for the genes evaluated at the different sampling times. Collectively, the results show a rapid and more robust response of neuro-endocrine and tissue repair markers in the injuries below than above the lateral line, which could be attributable to their proximity to vital organs.