Gene Expression Analysis Of Diabetic Foot Ulcer Debrided Tissue To Standard And Advanced Treatments
Jessica M. Eager1, Michael S. Weingarten, MD2, Kara L. Spiller, PhD1.
1Drexel University, Philadelphia, PA, USA, 2Drexel University College of Medicine, Philadelphia, PA, USA.
BACKGROUND: Chronic diabetic foot ulcers (DFUs) are notoriously difficult to treat, with a major challenge stemming from the mystery as to why some wounds respond to treatment while others do not. The goal of our study was to determine differences in gene expression within wound tissue of healing vs non-healing DFUs treated with the standard of care (SOC) or advanced biomaterials (amniotic membrane-derived materials). We focused on a custom selected panel of 227 genes related to inflammation, macrophage phenotype, and communication with bacteria.
METHODS: Debrided tissue was collected at two wound care clinics from 29 patients treated with the SOC and 7 patients treated with human amnion derived biomaterials over time for gene expression analysis via Nanostring™. Samples were classified into responders and non-responders based on the status of the wound at 12 weeks following collection. Gene expression values were used in a linear regression model to determine differential gene expression between responders and non-responders to the SOC. Due to sample size, comparisons between SOC and advanced biomaterials could only be made between non-responders at week 4. Genes that were expressed below threshold in more than 50% of samples were excluded, resulting in 189 genes for analysis.
RESULTS: Pro-inflammatory genes EBI3 and CCL1 were upregulated in responders to the SOC compared to non-responders at all time points (adjusted p<0.05). Genes related to the pro-inflammatory macrophage phenotype (M1) and bacterial communication, CXCL9, CCL1, CXCL11, and DEFB4, were significantly upregulated at week 1 in responders. Time alone was not found to be a significant factor. Non-responders to the amniotic membrane-derived biomaterials expressed lower levels of the pro-inflammatory marker PRSS8 compared to non-responders to the SOC at week 4.
CONCLUSIONS: Because responders to the SOC expressed higher levels of genes related to the pro-inflammatory (M1) macrophage phenotype and bacterial communication at early time points, it is possible that these results are capturing the conversion of a chronic to acute wound environment. Additionally, because PRSS8 is an M1 marker, the results from the advanced biomaterials may indicate that these materials have a slight anti-inflammatory effect, but more samples are required for validation.
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