Wound healing of experimental equine skin wounds and concurrent microbiota in wound dressings following topical propylene glycol gel treatment

Raphael Labens; Sharanne Raidal; Cathrine Borgen-Nielsen; Stephen Pyecroft; Sameer D Pant; Thomas De Ridder

doi:10.3389/fvets.2023.1294021

Wound healing of experimental equine skin wounds and concurrent microbiota in wound dressings following topical propylene glycol gel treatment

Front Vet Sci. 2023 Dec 14:10:1294021. doi: 10.3389/fvets.2023.1294021. eCollection 2023.

Authors

Raphael Labens^{1

2}, Sharanne Raidal¹, Cathrine Borgen-Nielsen¹, Stephen Pyecroft³, Sameer D Pant^{1

4}, Thomas De Ridder²

Affiliations

¹ School of Agricultural, Environmental and Veterinary Sciences, Faculty of Science, Charles Sturt University, Wagga Wagga, NSW, Australia.
² QBiotics Group Ltd., Yungaburra, QLD, Australia.
³ School of Animal and Veterinary Sciences, Faculty of Sciences, Engineering and Technology, University of Adelaide, Roseworthy, SA, Australia.
⁴ Gulbali Institute, Charles Sturt University, Wagga Wagga, NSW, Australia.

Abstract

Introduction: Topical wound treatments rely on carrier formulations with little to no biological impact. The potential for a common vehicle, a propylene glycol (PG) gel, to affect wound healing measures including microbiota is not known. Microbiome characterization, based on next generation sequencing methods is typically performed on tissue or directly obtained wound fluid samples. The utility for primary wound dressings to characterize equine wound microbiota in the context of topical treatments is currently unknown. This investigation reports the topical effect of an 80% PG based gel on wound healing and microbiota in wound dressings.

Methods: Experiments were performed in six mature horses utilizing a surgical, distal limb wound model, histology of sequential wound biopsies, photographic wound measurements and microbiota profiling via 16s rRNA sequencing of wound dressing samples. Experimental wounds were surveyed for 42 days and either treated (Day 7, 14, 21 and 28; at 0.03 ml/cm²) or unexposed to the PG gel. Wound surface area, relative and absolute microbial abundances, diversity indices and histologic parameters were analyzed in the context of the experimental group (treatment; control) using qualitative or quantitative methods depending on data characteristics.

Results: Compared to controls, treatment slowed the wound healing rate (17.17 ± 4.27 vs. 18.56 ± 6.3 mm²/day), delayed the temporal decline of polymorphonucleated cells in wound beds and operational taxonomic units (OTU) in wound dressings and lowered alpha-diversity indices for microbiota in primary wound dressing. Relative abundances of OTUs were in line with those previously reported for equine wounds. Clinical outcomes 42 days post wounding were considered similar irrespective of PG gel exposure.

Discussion: Results highlight the potential for vehicle exposure to alter relevant wound outcome measures, imposing the need for stringent experimental control measures. Primary wound dressings may represent an alternate sample source for characterization of the wound microbiome alleviating the need for additional interventions. Further studies are warranted to contrast the microbiome in wound dressings against that present on wound surfaces to conclude on the validity of this approach.

Keywords: 16S-rRNA gene sequencing; NGS; healing; horse; microbiome; wound model.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This study was funded by QBiotics Group Ltd., to explore the therapeutic effects of a potential drug candidate. Treatment data specific to the drug candidate is not included in this manuscript.