Nociceptive and Transcriptomic Responses in a Swine Diabetic Wound Model Treated with a Topical AT1R Antagonist

Abstract

Background:

Painful, treatment-resistant wounds are prevalent among diabetic patients and significantly affect health-related quality of life (HRQOL). Topical treatments may help alleviate pain without risk of dependence or side effects. However, there is a lack of topical wound compounds targeting pain-specific receptors. One possible target is proinflammatory angiotensin 1 receptor (AT1R), which is upregulated in diabetic skin and has been implicated in nociception.

Objectives:

We investigated the effects of topical valsartan, an AT1R antagonist, on pain (nociceptive thresholds) and gene expression changes (transcriptomics) in a swine model of diabetic wounds.

Methods:

Eight wounds were surgically induced in diabetic, hyperglycemic Yucatan miniature swine (n = 4). Topical AT1R antagonist was applied to wounds on one side and vehicle on the other side. Nocifensive testing was conducted at baseline, then weekly beginning 7 days after wound induction. Mechanical and thermal stimuli were applied to the wound margins until a nocifensive reaction was elicited or a predetermined cutoff was reached. After 7 weeks of testing, tissue from the dorsal horn, dorsal root ganglion, and wounds were sequenced and analyzed with DESeq2. Unbiased pathway analyses using Metascape were conducted on differentially expressed genes.

Results:

There was no significant difference in mechanical tolerance threshold between AT1R antagonist- and vehicle-treated wounds (p = .106). Thermal tolerance was significantly higher in AT1R antagonist-treated wounds as compared to vehicle-treated wounds (p = .015). Analysis of differentially expressed genes revealed enriched pathways of interest: Interleukin–18 signaling in dorsal horn laminae IV–V and sensory perception of mechanical stimulus in wound tissue.

Discussion:

In this study, wounds modeling diabetic ulcers were created in hyperglycemic swine and treated with a topical AT1R antagonist. AT1R antagonist-treated wounds had a higher tolerance threshold than vehicle-treated wounds for thermal hyperalgesia, but not mechanical allodynia. Pathway analyses of differentially expressed genes revealed several pathways of interest for future pain research. Although further studies are needed to confirm the findings, this study can improve nursing care by providing information about a potential future treatment that may be used to decrease pain and improve HRQOL in patients with diabetic wounds.

Diabetic wounds are a prevalent and serious complication associated with chronic type 2 diabetes mellitus. Approximately one quarter of diabetic patients will develop a treatment-resistant wound at some point during the disease process at an annual cost of over $7 billion in the United States alone (Burgess et al., 2021) Up to 60% of patients complain of stinging, pricking, pulsing, sore, or burning pain in the wound area (Bengtsson et al., 2008). The pain significantly affects health-related quality of life (HRQOL), causing emotional distress, insomnia, discomfort during dressing changes, and difficulty performing activities of daily living (ADLs; Obilor & Adejumo, 2015; Ribu et al., 2008)

Diabetic wound pathology involves a variety of factors, including numbness from diabetic neuropathy masking the initial injury, poor circulation in extremities, and delaying healing (Frescos & Copnell, 2020; Oliver & Mutluoglu, 2019) Nerve damage associated with poor circulation can lead to a prolonged proinflammatory state and excessive inflammation, which are hallmarks of diabetic wounds (Bengtsson et al., 2008; Ribu et al., 2008). Characteristics of inflammation, such as secretion of proinflammatory cytokines by macrophages, release of cytotoxic enzymes and inflammatory mediators by neutrophils, and miRNA dysregulation are present in diabetic wounds (Burgess et al., 2021; Dasari et al., 2021). The presence of inflammation leads to peripheral sensitization, pain in the wound area, and decreased tolerance threshold to mechanical and thermal stimuli (Vasko, 2009). Lowered mechanical tolerance threshold, or mechanical allodynia, refers to the point at which an innocuous touch sensation causes pain in affected individuals. Lowered thermal tolerance threshold, or thermal hyperalgesia, refers to the point at which a thermal stimulus that would ordinarily cause minor discomfort causes pain in affected individuals (Sandkühler, 2009).

While systemic oral medications such as opioids are often prescribed to mitigate these symptoms, they may result in side effects and dependence (Purcell et al., 2020). Use of topical treatments may enable pain alleviation without these risks (Purcell et al., 2020). However, while many studies investigate topical compounds for diabetic wound healing, few address pain relief (White & McIntosh, 2008). Previously studied agents for diabetic wound treatment and pain relief include topical morphine (Graham et al., 2013), ibuprofen-releasing foam (Sibbald et al., 2007), and eutectic mixture of local anesthetics (EMLA) cream (Purcell et al., 2017). However, these treatments have proved ineffective (Graham et al., 2013), were tested only while changing dressings (Purcell et al., 2017), or are not available in the U.S. (Woo et al., 2008). Furthermore, there are few, if any, topical treatments that target specific pain receptors, necessitating further development and testing of targeted treatment for diabetic wound pain.

One possible target is angiotensin 1 receptor (AT1R), the expression of which is increased in diabetic skin (Abadir et al., 2018). Evidence suggests that AT1R, primarily known for its role in blood pressure regulation, has receptors implicated in nociception and neuroinflammatory responses (Bali et al., 2014; Kukkar et al., 2013). Administration of an AT1R inhibitor, losartan, to paclitaxel-treated rats delayed the onset and reduced the intensity of chemotherapy-induced peripheral neuropathy through reduction of inflammatory cytokine levels in the dorsal root ganglia (Kim et al., 2019).

Valsartan, an AT1R inhibitor, has been used topically for wound healing in pig models of diabetic wounds. Wounds treated with a 1% valsartan compound healed faster than wounds treated with a placebo (Abadir et al., 2018). Although valsartan is an antihypertensive medication, only low concentrations of 1–50 nanomoles of the drug were found in blood samples at the beginning of the study. Later in the treatment course, they were undetectable. By contrast, blood valsartan levels are 4,000–5,000 nanomoles after being taken orally. This suggests that a topical valsartan compound works locally at the site of application rather than systemically (Abadir et al., 2018). Given the role of AT1R in inflammation and pain, topical valsartan applied to the wound site may have a local effect on pain sensation and inflammatory pain caused by diabetic wounds.

Because topical valsartan for pain sensation is an off-label use, it cannot be tested in human participants. Furthermore, there are many confounding variables in wound pain, including patient demographics, other treatments they may have used or are using, and the wound’s size, depth, and age. Since optimal experimentation requires identical wounds that cannot be ethically induced in humans, testing the compound necessitates a translational model of diabetic wounds. While rodents are most commonly used in pain research, swine are ideal models for studying wound healing and nociception (Castel et al., 2017; Sullivan et al., 2001). Unlike rodents, swine skin shares myriad characteristics with that of humans. Humans and swine have comparable nociceptive C-fiber classes, an epithelium that is firmly affixed to the lower dermal layers and skin that heals through reepithelialization (Castel et al., 2017; Obreja & Schmelz, 2010; Sullivan et al., 2001). Diabetic swine and humans share a similar pathology and response to insulin (Stricker-Krongrad et al., 2016), and swine exhibit highly individualized nociceptive responses that correlate well with those of humans (Castel et al., 2017; Ison et al., 2016). Creation and validation of a swine model of diabetic wound pain could be advantageous for future research.

In this study, we used a diabetic wound model in hyperglycemic Yucatan miniature swine to test the effect of an AT1R antagonist topical compound formulated with 1% valsartan on pain sensation in diabetic wounds. We then conducted transcriptomic analyses using RNA from dorsal root ganglion, dorsal horn laminae, and wound tissue. The results of the analyses identified differentially expressed genes and relevant biological signaling pathways that may be implicated in diabetic wound pain.

Methods

Animal Care

Four 8-month-old Yucatan miniature swine were obtained from Sinclair Research Center (Auxvasse, MO) for this blinded controlled trial. Type 1 diabetes had been induced with alloxan when the animals were 7 months of age. Upon arrival, the animals were housed in separate pens in the same room and acclimated to the facility for 1 week on a 12:12 light–dark cycle with water ad libitum. Blood glucose levels were checked in the morning and evening by pricking the edge of the ear with a 25G hypodermic needle after the site had been numbed with lidocaine (2.5%) and prilocaine (2.5%) cream (Akorn Hi-Tech Pharmacal Co., Inc., Amityville, NY). Depending on their weight, animals were then fed 500–700g of specialized swine feed (Purina, Gray Summit, MO). Novalin insulin was administered 15 min after feeding. Dose was determined using a sliding scale to maintain a hyperglycemic range of 200–400mg/dL (Table 1). Swine were monitored for signs of hypo- and hyperglycemia outside the acceptable range, such as tremors or lethargy. All animal care and procedures were approved by the institutional animal care and use committee of the University of Maryland, Baltimore.

Table 1.

Sliding scale used for twice daily insulin administration

Blood Glucose	Normal Behavior Insulin Dose (IU/kg)	Lethargic Behavior Insulin Dose (IU/kg)
>500	0.3	0.4
450–499	0.2	0.3
401–449	0.1	0.2
300–400*	0.1	0.2
100–299	0.1	0.2
40–99	None	None

^*Note. Target range

Wound Induction and Treatment

Swine were sedated using Telazol (3–5 mg/kg) and Xylazine (1–2.2 mg/kg) and then intubated. Anesthesia was maintained via face mask with 1%–3% isoflurane in 100% oxygen. Eight full-thickness 2.5-cm diameter excisional wounds were created with a scalpel, four on either side of the spinal column (Figure 1). Immediately following surgery, the wounds were dressed in 10 ml of Surgilube vehicle (1% dimethylsulfoxide), sterile gauze pads, and adhesive bandages. For the five postoperative days, the wounds were re-dressed in the same manner daily. Animals received buprenorphine (0.01–0.05 mg/kg) preoperatively for pain control. Carprofen 4–4.4 mg/kg IM was administered immediately postoperatively and for 4 days following surgery.

Figure 1.

Visual representation the eight surgically induced full-thickness 2.5-centimeter diameter wounds on the dorsal region of a diabetic Yucatan miniature swine. The left side (Gel A) was treated with a topical AT1R antagonist (1% valsartan) compound and the right side (Gel B) was given vehicle only. Each side of the wound beds were marked with a blue dot, where a mechanical stimulus was applied, or a red dot, where a thermal stimulus was applied. Drawing is adapted from Designs CAD (Pig Animal Standing Top View Plan 2D DWG Block For AutoCAD, n.d.).

Starting on postoperative day 6, the beginning of the wound proliferation and remodeling phase of wound healing, 10 ml of the AT1R antagonist compound was applied to wounds on the left side of the spinal column, while the right side continued to receive 10 ml of Surgilube vehicle. This procedure was repeated daily for the duration of the experiment. Experimenters were blinded as to which side received the treatment and which received the vehicle. Both were stored in identical jars labeled only as “A” and “B.” Experimenters applied the contents of jar “A” to the wounds on the left side and the contents of jar “B” to the wounds on the right side without knowing which jar contained the actual treatment.

Because topical valsartan acts locally rather than systemically (Abadir et al., 2018), monitoring for changes in blood pressure or pulse was not necessary. Wounds were subjectively assessed for exudate, rate of healing, and granulation tissue formation during daily dressing changes. Swine wore nylon jackets secured with Velcro (Lomir Biomedical, Malone, NY) and were housed singly to prevent dressings from being dislodged.

Wound Pain Assessment

Swine were placed in a restraint sling (Lomir Biomedical; Malone, NY) for pain assessment testing. Prior to baseline testing, the animals were acclimated to the sling in daily 5-min increments until they could tolerate 20 min without struggling. Mechanical and thermal nocifensive tolerance testing was conducted at baseline prior to surgery and then once per week beginning 7 days after wound induction.

Mechanical allodynia testing was conducted using a Pressure Application Measurement (PAM) device (Ugo Basile; Varese, Italy). Pressure was applied 1.5 cm from the outer margins of the wound and steadily increased at the rate of 5 kPa/s until it reached 1500 g of force or until a nocifensive reaction was elicited. Nocifensive behavior was defined as any noxious response to unpleasant stimuli, including ear flattening, nostril-flaring, facial or body muscle tension, abrupt movement, tail lashing, or vocalization. The gram force needed to induce the reaction was recorded, or if no reaction was present, the 1,500 g cutoff was used to prevent tissue damage. The procedure was repeated three times for each wound with a 5-min break between trials, and the results were averaged.

Thermal hyperalgesia was tested via a focused beam CO₂ laser applied 1.5 cm from the outer margin of each wound and 180° from the site of mechanical testing. The thermal stimulus was applied for a maximum of 25 s or until a nocifensive reaction was elicited. The time in seconds needed to induce the reaction was recorded, or if no reaction was present, the 25 s cutoff was used to prevent tissue damage. The procedure was repeated three times for each wound with a 5-min break between trials, and the results were averaged.

Statistical Analysis

Wound pain assessment data were analyzed using a linear mixed effect model accommodating the correlations between the repeated measures and between wounds within each animal. The fixed effects included time in weeks (categorical), treatment, and the interaction terms between time and treatment. The model also included individual swine as a covariate adjustment to control possible confounding effects between animals. The wounds were considered a random effect, accommodating the correlations between the repeated measures. The differences in changes of outcome variables from baseline to each follow-up week were compared between the treatment groups. The outcome variable for mechanical allodynia was gram force required to elicit a reaction, while the outcome for thermal hyperalgesia was time in seconds to respond to the focused laser beam. SAS 9.4 was used to analyze the data.

Tissue Harvest and Histology

At the conclusion of the study, swine were euthanized and a 3mm section of skin was removed from the center of each wound bed. Dorsal root ganglia and dorsal horn tissue from laminae I–II and IV–V were harvested from the right and left sides. Tissue samples were flash-frozen on dry ice, then preserved in TRIzol (Thermofisher, Waltham, MA), and stored in a -80° freezer.

RNA-Sequencing and Pathway Analysis

Gene expression profiles were analyzed using RNA sequencing. Tissue was prepared using a homogenizer (Pro-Scientific 200, Oxford, CT), and RNA was purified and extracted from the samples using Qiagen miRNeasy Mini Kit Cat #217004 (Qiagen, Valencia, CA). The sequencing library was prepared using NEB Ultra II Directional RNA Library Prep Kit for Illumina (Illumina, San Diego, CA) according to the manufacturer’s protocol. Sequencing was done using the Illumina NovaSeq 6000 (Illumina, San Diego, CA) on an S4 flow cell. A FastQ format database of 150-base pair paired-end reads per sample was generated, and FastQC was used to evaluate the quality of the files.

Salmon was used to quantify transcript abundance, saving significant computational time compared to the traditional alignment-based methods. Salmon applies a quasimapping approach to match sequences to a transcript reference, followed by a two-step inference phase that respectively estimates and refines the transcript expression levels (Patro et al., 2017). Our reference transcript was Sus scrofa.Sscrofa11.1.cdna, which includes all transcripts of Ensembl genes, excluding ncRNA. Next, we performed the following steps: transcripts abundance estimates were imported into R environment using Tximport R package (Soneson et al., 2016), annotated to The Swine Genome Sequencing Consortium (SGSC [GCA_000003025.6 GCF_000003025.6]), normalized to perform quality control checks at sample-level and gene-level, and eventually analyzed for differential expression across AT1R antagonist- and vehicle-treated tissue using DESeq2 (Love et al., 2014). We removed low abundance genes (base mean < 50) and considered genes with absolute log₂ fold change > 1 and p < .05 as significantly differentially expressed.

Pathway analyses of significant differentially expressed genes (DEGs) were conducted using Metascape Gene Ontology. Because the Metascape platform does not include specific genomic information for sus scrofa, homo sapiens was used as the reference genome for the unbiased pathway analyses (Zhou et al., 2019). The genomes of homo sapiens and sus scrofa are 84.1% matched (Fang et al., 2012). Cytoscape was used to create a network of enriched terms, each represented by a colored node that identifies its cluster ID (Shannon et al., 2003).

Results

Behavioral Testing

Thermal hyperalgesia was measured by time in seconds to withdraw from focused laser heat application with a maximum of 25 s—a shorter time to withdraw indicated heightened sensitivity to thermal stimuli (Figure 2a). At Weeks 0 and 1, prior to AT1R compound application, there was no significant difference between right and left sides. At Weeks 5 and 6, the AT1R antagonist-treated wounds (M = 19.77 s, SD = 6.20; M = 17.79 s, SD = 6.15) showed significantly higher tolerance to application of heat than the vehicle-only wounds (M = 14.90 s, SD = 7.18; M = 13.56 s, SD = 7.09). Overall, wounds treated with the compound had a higher threshold for heat stimuli than those given vehicles only (p = .015).

Figure 2.

A. CO2 laser stimulation was applied to adjacent areas at the edge of each wound bed for 25 seconds or until a nocifensive response was observed. Shorter time to withdrawal represents a shift to the left in sensitivity. Results indicated that wounds treated with AT1R antagonist had significantly higher tolerance to thermal stimulation at study weeks 5 and 6.

B. A pressure algometer was applied to adjacent areas at the edge of each wound bed with steadily increasing pressure until 1500g of pressure was reached seconds or until a nocifensive response was observed. Lower pressure of withdrawal represents a shift to the left in sensitivity. While week 1 appears to show significance, the AT1R antagonist treatment had not yet begun when those measurements were taken. Thus, no significant difference was observed between wounds treated with AT1R antagonist and those treated with vehicle in mechanical sensitivity testing. All data are presented as means of the responses in n=4 pigs with n=8 wounds each. Analyses were conducted using a mixed effect model using the pigs as fixed effects, including random wound effect, and using Gauss-Hermite quadrature. (*p<.05)

Mechanical allodynia was measured in gram force using a pressure algometer with a maximum threshold of 1,500 g. Lower pressure at withdrawal indicated heightened sensitivity to mechanical stimuli (Figure 2b). At baseline (Week 0), all animals tolerated the maximum force without withdrawal or other indication of discomfort. The week following surgery (Week 1), there was a significant decrease in threshold tolerance as compared to the previous week (p < 0.001). Although the threshold of the wounds in the AT1R antagonist group (M = 1076.83g, SD = 208.82) was significantly lower than those in the vehicle-only group (M = 1357.59g, SD = 121.42), the Week 1 measurements were taken prior to the first administration of the experimental compound. There was no significant difference in overall changes between the pressure tolerance of the wounds treated with AT1R antagonist as opposed to those treated with vehicle only (p = .106).

Differential Gene Expression and Pathway Analysis

Dorsal horn laminae I–II and IV–V, dorsal root ganglion, and wound tissue were assessed for differential gene expression between those treated with the AT1R antagonist compound versus vehicle only. An average of 130 million reads were obtained for each sample. Genes with a log2 fold change of > 1 or < -1, a base mean of > 50, and a p-value of < .05 were considered differentially expressed and selected for term cluster analysis via Metascape.

The dorsal horn laminae I–II on the AT1R antagonist-treated side had 58 differentially expressed genes as compared to the dorsal horn laminae on the vehicle-treated side, with 18 upregulated and 40 downregulated. Metascape pathway analysis showed the expression of 12 enriched term clusters. The dorsal horn laminae IV–V on the AT1R antagonist-treated side had a total of 101 differentially expressed genes as compared to the vehicle-treated side (Figure 3b). Of those, 55 were upregulated, and 46 were downregulated. Pathway analysis revealed a total of 23 enriched term clusters for treated versus vehicle. The dorsal root ganglion on the treated side had 191 differentially expressed genes, 183 upregulated and 8 downregulated (Figure 3c). There were 47 enriched term clusters in the dorsal root ganglion on the treated side. AT1R antagonist-treated wounds had a total of 108 differentially expressed genes as compared to vehicle-treated wounds, 24 of which were upregulated and 84 of which were downregulated (Figure 3d). There were 23 enriched term clusters in treated wound tissue.

Figure 3.

A. Volcano plot of significantly expressed genes in the dorsal horn lamina I-II.

B. Volcano plot of significantly expressed genes in the dorsal horn lamina IV-V.

C. Volcano plot of significantly expressed genes in the dorsal root ganglion.

D. Volcano plot of significantly expressed genes in wound tissue.

Of the four tissue types analyzed, only dorsal horn laminae IV–V and wound tissue had enriched term clusters relevant to pain sensation. Interleukin–18 signaling showed significant expression in the former, and sensory perception of mechanical stimulus was expressed in the latter. Cytoscape was used to create cluster networks of the pathway interactions for these samples (Figures 4a and 4b).

Figure 4.

A. Color-coded network of enriched terms in dorsal horn IV-V organized by similar cluster ID. Genes groups with particular relevance to nociception are identified within the red box.

B. Color-coded network of enriched terms in wound tissue organized by similar cluster ID. Genes groups with particular relevance to nociception are identified within the red box.

Discussion

In this study, we investigated the behavioral and transcriptomic effects of the topical application of a valsartan compound—an AT1R antagonist—on cutaneous wounds in diabetic swine. Humans and swine share similar physiological and pathological characteristics, making them ideal for translational studies of diabetes and wound pain (Stricker-Krongrad et al., 2016; Sullivan et al., 2001). Because patients with hyperglycemia are most likely to get diabetic wounds, the swines’ blood glucose levels were maintained between 200–400 mg/dL to model poorly controlled diabetes in humans.

In humans, verbal reporting is the gold standard for pain assessment (Fink, 2000), but pain measurement in animals must employ alternate methods. Most pain studies in swine examine pain during routine livestock procedures, such as castration. However, the few translational pain studies in swine employed similar methods of nociceptive testing, namely mechanical and thermal sensitivity (Di Giminiani et al., 2013, 2014). In our study, mechanical and thermal stimuli were applied to the area just outside of the wound to observe tolerance of noxious sensations. When the noxious sensations were felt, animals manifested nocifensive responses comparable to those seen in humans—most notably vocalization and muscle twitching.

Mechanical tolerance threshold was not significantly different between the two groups. A possible reason for the lack of significance may have been the existence of a ceiling effect. The swine tolerated the full 1,500 g of force at nearly all time points except for the first week after surgery. For future studies, it would be advantageous to raise the threshold. The anomalous Week 1 result, which appeared to show higher tolerance to pressure in the vehicle versus treated groups, was measured prior to the initial application of the compound. The result may be partially attributable to the testing environment, as the room in which the testing was conducted was loud at times and may have been distracting to the animals. Thermal hyperalgesia testing showed a higher overall heat threshold tolerance in wounds treated with the AT1R antagonist versus those given vehicle only, specifically on Weeks 5 and 6 of treatment. Weeks 2, 3, and 7 showed a positive trend toward significance.

RNA-sequencing of nervous system and wound tissue identified differentially expressed genes in the treated versus vehicle-treated sides of the animals. The most significantly upregulated gene in dorsal horn lamina IV–V tissue was autophagy and beclin 1 regulator (AMBRA1). One study found that mice with AMBRA1 alterations resulting in defective autophagy had increased allodynia and neuropathic pain (Coccurello et al., 2018). This suggests a possible role for AMBRA1 in neuropathy.

Pathway analyses of the differentially expressed genes revealed expression of pain-relevant pathways. Interleukin–18 (IL–18) signaling was the most abundantly expressed pathway in dorsal horn lamina IV–V tissue. IL–18 is a proinflammatory cytokine that is upregulated in the presence of tissue damage and nerve injury (Pilat et al., 2016). It has also been implicated as a pain-related biomarker in certain cancer types (Heitzer et al., 2012). Rats injected with IL–18 manifested allodynic responses comparable to those observed post-nerve injury. Moreover, attenuation of IL–18 via anti-IL–18 antibodies in a nerve injury model reduced tactile allodynia (Miyoshi et al., 2008). This suggests a difference in proinflammatory pathways between the treated and vehicle-treated sides at the level of dorsal horn lamina IV–V.

In wound tissue, the enrichment of the sensory perception of mechanical stimulus pathways is of particular interest. This group includes several genes implicated in detecting stimuli involved in sensory perception of pain and sensory perception of temperature stimulus Expression of this group in wound tissue may imply a difference in sensory pain perception between treated and vehicle-treated wounds. Pathway analysis for dorsal horn lamina I–II and dorsal root ganglion did not reveal any pathways related to nociception or sensation.

While Abadir et al. (2018) reported that AT1R antagonist-treated wounds healed better than placebo-treated wounds, we did not observe any significant differences between the treatment and control wounds. This may be related to the size of the wounds; Abadir et al. (2018) used 5-cm diameter wounds, while our study used 2.5-cm diameter wounds. The primary limitation of this study was the small sample size. Each of the four animals had eight wounds, bringing the total number of wounds to 32. Because the swine served as their own controls, four of their wounds were treated with the AT1R antagonist, while the other four received Surgilube vehicle. Thus, the total number of treated wounds was 16. Further research with a larger sample size would be beneficial.

The study results have implications for nursing practice in terms of caring for diabetic wounds and improving associated symptoms. While further trials in animals and human participants are necessary to determine efficacy, the topical AT1R antagonist shows potential to reduce thermal pain in diabetic wounds. Nurses could apply the treatment prior to dressing changes to minimize pain during the procedure and teach patients to apply it themselves. This could improve patients’ HRQOL, decrease emotional distress, and allow them to engage in ADLs.

Conclusion

Diabetic wound pain is a significant health concern that could benefit from a targeted receptor treatment. Topical AT1R antagonist shows evidence of alleviating thermal-induced hypersensitivity in a swine model of diabetic wounds, albeit in a small sample size that needs further investigation in a larger study. Pathway analyses of the spinal and wound tissue revealed several pathways of interest that indicate pain-specific downstream alterations in treated versus vehicle-treated wounds. Findings from this study shed light on a potential treatment that nurses can use to decrease pain and improve HRQOL in patients suffering from diabetic wounds.