A Cellularized Marine Collagen-based Wound Dressing For The Treatment Of Skin Wounds: Observations In A Rodent Animal Model

*Purpose/Objectives: Skin wound healing is a dynamic process that comprises different overlapping phases that aims to restore the skin integrity. However, a minimal impairment (e.g., infection) may lead to hard-to-heal ulcers or open non-closing wounds in a constant state of inflammation. For this reason, an ideal treatment able to contain inflammation while promoting healing is necessary in the clinic. Wound dressings are materials used to cover and protect the wound from damage along with maintaining its moisture, hence they are one of the gold standard treatments for wound care management in Veterinary Medicine. Besides dressings, cell therapy has also shown promising results, in particular the application of mesenchymal stem cells (MSCs). This cell population can release a plethora of soluble molecules that modulate different biological processes such as inflammation. In this work we describe the application of a marine collagen-based wound dressing (MCDT) alone or in combination with allogeneic adipose-derived MSCs (aMSCs) for the treatment of skin wounds in a rodent model. *Methodology: A total of 48 rats were included in the study. On the back of each animal two round wounds were surgically induced: to one aMSCs or the biomaterial, with or without cells (MCDT or MCDT+aMSCs), was applied (n = 16 per treatment) while one was left untreated. Wounds were checked daily for signs of adverse reactions or infection. After 5 and 10 days, skin samples were collected and processed for histopathological (inflammation and granulation tissue (GT) presence) and gene expression analysis for factors involved in the skin wound healing process (extracellular matrix proteins, growth factors, and pro-inflammatory cytokines). *Results: Clinically, at day 5 wound closure rate was similar among treatments. At day 10, MCDT-treated wounds showed a slightly lower wound closure rate compared to treatment containing cells. At the histological level, the presence of inflammatory cells was comparable among untreated and MCDT-treated wounds while cell-based treatment showed a lower level of inflammation in the healing tissue. This observation is also reflected in the mRNA level of TNF-a and, especially, IL-1b, both well-known pro-inflammatory factors, which was lower in wounds treated with aMSCs and MCDT+aMSCs. All treated wounds also showed a higher amount of GT on day 5 compared to untreated lesions. Moreover, while treated wounds showed a more mature GT at day 10, untreated lesions still displayed a high amount of immature GT. These results are supported by the high expression of collagen type I and III in untreated wounds, while treatments controlled collagen expression to base levels at day 10. Moreover, higher levels of angiogenesis were observed in treated wounds, especially with MCDT+aMSCs, which were also characterized by a higher presence of vessels, especially in the lower layers of the tissue, and higher levels of PDFGb and VEGF. *Conclusion/Significance: In conclusion, all treatments led to better outcomes compared to physiological healing. Indeed, lower inflammation and better deposition of structural proteins are crucial factors to reach a proper level of skin wound healing after wounding and both elements were observed in this work