A Pilot Study to Evaluate the Effects of Perfusion-decellularized Porcine Hepatic-derived Wound Matrix on Difficult-to-heal Diabetic Foot Ulcers

Objective. The purpose of this prospective pilot study is to evaluate the effects of a novel perfusion-decellularized porcine hepatic-derived wound matrix (PDPHD-WM) on very difficult-to-heal diabetic foot ulcers (DFUs). Materials and Methods. For the intent of this study, a very difficult-to-heal DFU is one with a duration > 3 months despite using at least 1 advanced healing modality. Seven patients were enrolled in the study for a length of 14 weeks, including a 2-week run-in phase of standard-of-care therapy with saline gel and offloading in a CAM walker. Average wound duration was 25.5 months (range, 5–48 months). The PDPHD-WM was applied after the run-in phase and assessed weekly by the investigator. An average of 2.1 applications of the graft were performed (range, 1-4) over the study period. Results. Three patients (42.9%) reached complete wound closure, 2 had partial wound closure (28.6%), 1 (14.3%) had worsening of his wound, and 1 (14.3%) was removed from the study due to osteomyelitis. Average percent wound closure over the 12-week treatment period was 56% for all patients and 77% when only those wounds that improved were included in the data. In addition, a bimodal population distribution was noted in this small series. Patients who demonstrated an early response continued on to closure or near-closure (4 patients), while those who showed little or no early response remained unclosed at the end of the study. Conclusions. These results suggest that PDPHD-WM may be an appropriate modality to treat difficult-to-heal DFUs, and a larger randomized placebo-controlled trial should be performed to investigate these findings. To the best of the authors’ knowledge, this is the first collected data on using PDPHD-WM to treat DFUs.

Diabetes mellitus has become a global epidemic, with about 422 million people affected worldwide,¹ including 30.3 million people in the United States.² Patients with diabetes may have up to a 25% lifetime risk of developing a diabetic foot ulcer (DFU).³ Currently, the standard of care (SOC) for initial DFU treatment is debridement, offloading, tight glycemic control, appropriate antimicrobial management, and imaging when needed.⁴- A meta-analysis⁵ of patients studied in controlled trials demonstrated an average healing rate of 31% at 20 weeks with SOC.  A substantial portion of DFUs will become infected over time, resulting in minor and major lower extremity amputations.⁶ As the main reason for diabetes-related hospitalizations, DFUs create an economic burden on the health care system and considerably impair quality of life.-⁷ In cases where a wound fails to decrease in size by 50% within 4 weeks with SOC, advanced care is commonly employed to attempt to close the wound and limit complications.⁸ Advance care may include topical platelet-derived growth factor (PDGF),⁹ hyperbaric oxygen therapy (HBOT),¹⁰ and bioengineered alternative tissues (BAT).^11-15 

This pilot study evaluates the effects of a perfusion-decellularized porcine hepatic-derived wound matrix (PDPHD-WM; Miroderm; Miromatrix Medical Inc, Eden Prairie, MN) on very difficult-to-heal DFUs. For the intent of this pilot study, a very difficult-to-heal DFU is one with > 3 months’ duration despite using at least 1 advanced healing modality.

The pilot study lasted 14 weeks. All patients were treated and assessed by the first author in an outpatient setting. Informed written consent was obtained from all patients prior to enrollment in the trial. Patients were selected to receive PDPHD-WM as a treatment for their DFU based on qualifications of the inclusion/exclusion criteria. 

Inclusion criteria
Patients ≥ 18 years of age, who had type 1 or 2 diabetes mellitus and glycosylated hemoglobin < 12% within 3 months of PDPHD-WM application, with adequate vascular perfusion of the affected limb as determined by ankle-brachial index (≥ 0.9), willing and able to maintain required offloading of the affected limb and perform necessary dressing changes, with a Wagner grade I or II DFU (full thickness) > 1 cm², and was present for > 30 days prior to time of screening, and who experienced previous failure of ≥ 1 advanced therapies (PDGF, HBOT, or BAT) to close the wound comprised the inclusion criteria for this study.

Exclusion criteria
Patients were excluded due to the following factors: suspected or confirmed signs of infection of the study ulcer/limb; sensitivity to porcine products; pregnancy; receiving medication or treatment known to affect wound healing within 30 days of treatment visit; excessive lymphedema that could interfere with wound healing; Charcot foot with a bony deformity; Chopart’s amputation; history of bone cancer of the affected limb; treatment with PDGF, HBOT, or BAT within 30 days of treatment visit; or if the size of the ulcer following debridement improved by > 30% during the run-in phase.

The DFU was assessed clinically, photographed, and measured via planimetric tracing software (ImageJ Version 1.50; National Institutes of Health, Bethesda, MD) at the screening visit (day 0 [-14 ± 3 days]). Each wound tracing was scanned into a digital image. Each pixel length was calibrated, and then the polygon tool was used to define the contour of each wound tracing. Finally, the area defined by the polygon was calculated within the software using the measure function. A 2-week run-in period was then allotted, where all wounds were treated with SOC alone. This included sharp surgical debridement, a saline-gel sterile gauze dressing that was changed once daily by the patient, and offloading with a removable CAM boot. At the treatment visit (day 0 ± 3 days), the wound was assessed again. If there was < 30% improvement in wound size, the patient qualified for application of PDPHD-WM. The ulcer was debrided to healthy tissue, and the wound matrix was secured to the wound with adhesive strips, benzoin, sutures, staples, or a combination of these methods. Saline gel was applied to the outside of the graft and a nonadherent contact layer was secured to the wound using a multilayer compression bandage that was left intact until the next treatment visit. Continued offloading with a CAM boot was maintained throughout the study. Thereafter, weekly office assessments were made for the next 11 weeks (12 study weeks in total), and the wounds were photographed, traced, and assessed. If deemed appropriate by the treating physician, additional PDPHD-WMs were applied at subsequent visits for lack of healing, graft loss from shearing, or minimal visible reepithelialization. At the end of the 12-week treatment phase, data on percentage of complete closure and rates of closure were compiled. 

Product
The PDPHD-WM is derived from the highly vascular porcine liver utilizing perfusion decellularization. It retains an intact extracellular matrix (ECM) with unique properties such as an epithelial-basement membrane, an open collagen matrix, and vascular ECM. Perfusion decellularization is a new technology used to decellularize whole organs and vascularized tissues, which has enabled numerous advances in tissue engineering of whole organs (heart, lung, liver, and kidney).^16-19 This is in contrast to previous methods based on immersion decellularization, which is limited to thin, dense tissues (dermis, small intestine submucosa, urinary bladder, or pericardial tissue) that comprise many advanced wound care products. 

A total of 7 patients were screened from January 2016 to May 2016. The patient pool was from the primary author’s existing patient population. All 7 patients met inclusion criteria for enrollment in the study. Demographics and patient data are presented in the Table. Average patient age was 62.6 years, with an average wound duration of 25.5 months. Patient 6 was removed from the trial due to infection and osteomyelitis developing about 6 weeks into the study. Of the 6 remaining patients, 3 demonstrated complete wound closure by 56 ± 21 days. Figure 1 demonstrates a bimodal population with patients 2, 4, 5, and 7 demonstrating a ≥ 50% reduction in wound area, while the remaining patients were ≤ 35% reduction. Those patients who demonstrated an early response (patients 2, 4, 5 and 7) continued to closure or near closure, while those who demonstrated little or no response early (patients 1 and 3) remained unclosed at the end of the study. The average percent wound closure over the 12-week study period was 56% ± 63% for all patients; if patient 1 was removed from analysis, the average percent wound closure would be 77% ± 30%, given the increase in wound area observed over the 12-week period. For patient 4, Figures 2, 3, 4, 5, and 6 serially show the application of PDPHD-WM and healing of a DFU sub-fifth metatarsal that had previously failed 6 advanced therapies and offloading.

Adverse events
Patient 6 was removed from the trial due to infection and osteomyelitis, which necessitated resection of bone and administration of antibiotics.

In a meta-analysis of controlled trails,⁵ SOC has been shown to heal DFUs at an average of 31%. Sheehan et al⁸ found the initial 4 weeks of DFU care have a significant predictive value in that if the percentage area reduction (PAR) is > 50%, the wound has a 60% chance of healing in 12 weeks. Conversely, if the PAR is < 50% in 4 weeks, the wound has a 10% chance of healing in 12 weeks. It is imperative to heal DFUs before infection develops, which may lead to lower extremity amputation.¹⁷ 

A number of advanced treatment modalities have been shown to augment and accelerate healing rates in DFUs. Wieman et al²⁰ showed topically applied recombinant human PDGF significantly increased the incidence of complete wound closure by 43% and decreased the time to achieve complete wound closure by 32% as compared with placebo-controlled gel. Veves et al²¹ demonstrated 56% of treatment patients had complete DFU closure at 12 weeks with Apligraf (Orgranogenesis Inc, Canton, MA) as compared with 38% in the control group. Marston et al¹¹ studied the effects of Dermagraft (Organogenesis Inc) on DFUs and reported 30% had complete wound closure by week 12 as compared with 18.3% of control patients. Driver et al¹³ evaluated the effects of Integra Dermal Regeneration Template (Integra LifeSciences, Plainsboro, NJ) on DFUs and found that complete DFU closure during the treatment phase was significantly greater with the dermal regeneration product (51%) than the control (32%). In addition, the rate of wound size reduction was 7.2% per week for the dermal regeneration product subjects versus 4.8% per week for control subjects.¹³ 

A major limitation of this pilot study was the small number of patients included in the trial. In addition, there was only 1 study site and 1 physician who administered all care. 

To the authors’ best knowledge, this study is the first published data on PDPHD-WM for difficult-to-heal DFUs. In this initial clinical pilot trial, 3 of 7 (42.9%) patients healed within 12 weeks with the PDPHD-WM. This is noteworthy as all of these wounds had been present for an average of > 2 years (range, 12–48 months) and had previously failed at least 1 advanced treatment modality with the primary author as the treating physician. Interestingly, the data demonstrated a bimodal distribution, which may be an indicator for which wounds will heal and which will not using this matrix. These results suggest that PDPHD-WM may be an appropriate modality to treat difficult-to-heal DFUs. A larger randomized placebo-controlled trial should be performed to investigate these findings.