Histology Scoring System for Murine Cutaneous Wounds

Monitoring wound progression over time is a critical aspect for studies focused on in-depth molecular analysis or on evaluating the efficacy of potential novel therapies. Histopathological analysis of wound biopsies can provide significant insight into healing dynamics, yet there is no standardized and reproducible scoring system currently available. The purpose of this study was to develop and statistically validate a scoring system based on parameters in each phase of healing that can be easily and accurately assessed using either Hematoxylin & Eosin (H&E) or Masson's Trichrome (MT) staining. These parameters included re-epithelization, epithelial thickness index, keratinization, granulation tissue thickness, remodeling, and the scar elevation index. The initial phase of the study was to (1) optimize and clarify healing parameters to limit investigator bias and variability; (2) compare the consistency of parameters assessed using H&E versus MT staining. During the validation phase of this study, the accuracy and reproducibility of this scoring system was independently iterated upon and validated in four different types of murine skin wound models (Excisional; punch biopsy; pressure ulcers; burn wounds). A total of n = 54 histology sections were randomized, blinded, and assigned to two groups of independent investigators (n = 5 per group) for analysis. The sensitivity of each parameter (ranging between 80% and 95%) is reported with illustrations on the appropriate assessment method using ImageJ software. In the validated scoring system, the lowest score (score:0) is associated with an open/unhealed wound as is evident immediately and within the first day postinjury, whereas the highest score (score:12) is associated with a completely closed and healed wound without excessive scarring. This study defines and describes the minimum recommended criteria for assessing wound healing dynamics using the SPOT skin wound score. The acronym SPOT refers to the academic and scientific institutions that were involved in the development of the scoring system, namely, Stellenbosch University, Polish Academy of Sciences, Obatala Sciences, and the University of Texas Southwestern.