PACE: randomized, controlled, multicentre, multinational, phase III study of PLX-PAD for critical limb ischaemia in patients unsuitable for revascularization: randomized clinical trial.

BACKGROUND: Revascularization is the primary treatment modality for chronic limb-threatening ischaemia (CLTI), but is not feasible in all patients. PLX-PAD is an off-the-shelf, placental-derived, mesenchymal stromal cell-like cell therapy. This study aimed to evaluate whether PLX-PAD would increase amputation-free survival in people with CLTI who were not candidates for revascularization. METHODS: People with CLTI and minor tissue loss (Rutherford 5) who were unsuitable for revascularization were entered into a randomized, parallel-group, placebo-controlled, multinational, blinded, trial, in which PLX-PAD was compared with placebo (2 : 1 randomization), with 30 intramuscular injections (0.5 ml each) into the index leg on days 0 and 60. Planned follow-up was 12-36 months, and included vital status, amputations, lesion size, pain and quality-of-life assessments, haemodynamic parameters, and adverse events. RESULTS: Of 213 patients enrolled, 143 were randomized to PLX-PAD and 70 to placebo. Demographics and baseline characteristics were balanced. Most patients were Caucasian (96.2%), male (76.1%), and ambulatory (85.9%). Most patients (76.6%) reported at least one adverse event, which were mostly expected events in CLTI, such as skin ulcer or gangrene. The probability of major amputation or death was similar for placebo and PLX-PAD (33 and 28.6% respectively; HR 0.93, 95% c.i. 0.53 to 1.63; P = 0.788). Revascularization and complete wound healing rates were similar in the two groups. A post hoc analysis of a subpopulation of 121 patients with a baseline haemoglobin A1c level below 6.5% showed improved 12-month amputation-free survival (HR 0.46, 0.21 to 0.99; P = 0.048). CONCLUSION: Although there was no evidence that PLX-PAD reduced amputation-free survival in the entire study population, benefit was observed in patients without diabetes mellitus or whose diabetes was well controlled; this requires confirmation in further studies. Trial registration: NCT03006770 (http://www.clinicaltrials.gov); 2015-005532-18 (EudraCT Clinical Trials register - Search for 2015-005532-18).

Autologous Blood-Derived Products (ABDPs) for the Treatment of Chronic Wounds.

Autologous blood-derived therapies have emerged as a unique and promising treatment option for chronic wounds. From whole blood clots to spun-down clot constituents, these therapies are highly versatile and tend to have a lower cost profile, allow for point-of-service preparation, and inherently carry minimal to no risk of rejection or allergic reaction when compared to many alternative cellular and matrix-like products. Subsequently, a diversity of processing systems, devices, and kits have surfaced on the market for preparing autologous blood-derived products (ABDPs) and many have demonstrated preclinical and clinical efficacy in facilitating chronic wound healing. However, not all ABDPs are created equal, and the lack of standardization among product formulations and cell concentrations as well as varying complexities in preparation protocols has led to unreliable substrate viabilities and overall inconsistent conclusions on efficacy. Additionally, external factors, such as the ease of drawing blood, the health of a patient's blood, and the reimbursement landscape have dissuaded some practitioners from incorporating ABDPs into an algorithm of care for recalcitrant wounds. Here, we attempt to categorize ABDPs into "classes" and examine their efficacy, advantages, and limitations when used as both a primary therapy and an adjunct for treating chronic wounds as well as comment on some potential considerations that may help gear future product development and application.

Circulating endothelial precursor cells are associated with a healed diabetic foot ulcer evaluated in a prospective cohort study.

The goal of this multicentre study was to evaluate whether circulating endothelial precursor cells and microparticles can predict diabetic foot ulcer healing by the 16th week of care. We enrolled 207 subjects, and 40.0% (28.4, 41.5) healed by the 16th week of care. Using flow cytometry analysis, several circulating endothelial precursor cells measured at the first week of care were associated with healing after adjustment for wound area and wound duration. For example, CD34+ CD45dim , the univariate odds ratio was 1.19 (95% confidence interval: 0.88, 1.61) and after adjustment for wound area and wound duration, the odds ratio was (1.67 (1.16, 2.42) p = 0.006). A prognostic model using CD34+ CD45dim , wound area, and wound duration had an area under the curve of 0.75 (0.67, 0.82) and CD34+ CD45dim per initial wound area, an area under the curve of 0.72 (0.64, 0.79). Microparticles were not associated with a healed wound. Previous studies have indicated that circulating endothelial precursor cells measured at the first office visit are associated with a healed diabetic foot ulcer. In this multicentred prospective study, we confirm this finding, show the importance of adjusting circulating endothelial precursor cells measurements by wound area, and show circulating endothelial precursor cells per wound area is highly predictive of a healed diabetic foot ulcer by 16th week of care.

Acellular Fish Skin for Tissue Replacement.

In modern practice, xenografts play a crucial role in wound management due to their regenerative properties. Of the various xenografts currently available on the market, acellular fish skin (AFS) grafts have emerged as a more effective alternative to existing xenografts and other standard of care (SOC) treatments for wound healing. Since AFS grafts require minimal processing, they maintain their structural integrity and natural properties, including an abundance of Omega-3 fatty acids, which is a distinctive, pro-regenerative feature. AFS grafts are also unique in that they are not derived from mammalian tissue, so there is no risk of viral transmission and no cultural or religious barriers to use. AFS grafts have been shown to be more cost-effective in the treatment of diabetic foot ulcers (DFUs) and result in a higher percentage of healed wounds, fewer amputations, and better patient quality of life. Several studies and case reports have highlighted the versatility of AFS in not only acute and chronic wound healing, but also for burn wound skin regeneration. Additionally, AFS may have promise as an implantable biologic matrix for suture line reinforcement in hernia repairs or breast and dura reconstruction.

Implantable Biologics for Soft Tissue Surgery Reinforcement.

Soft tissue reinforcement focuses on medical grafts that are designed to support and regenerate soft tissue under or near suture lines. Soft tissue is defined as areas of similarly specialized cells that function to connect, support, and surround other structures and organs of the body. These tissues include skin, subcutaneous tissue, fascia, ligaments, tendons, fibrous tissues, fat, synovial membranes, and muscle. Most of the implantable devices used for this purpose are made of collagen, the most abundant protein in mammals and a key component of the extracellular matrix of soft tissues that allows for tissue repair. For suture line reinforcement, exogenous collagen from various sources is implanted under or in continuity with the suture line to allow for increased strength and better healing. First introduced in the field of breast reconstruction, this practice is now also used in hernia repair, dural repair, vaginal slings, amputation reinforcement, tendon repair reinforcement, and even dental soft tissue regeneration.

The Shift to Synthetics: A Review of Novel Synthetic Matrices for Wound Closure.

Since the late 1990s, a growing number of "skin substitutes" have become available to practitioners seeking to heal large surface wounds. These extracellular matrices were originally from xenograft sources, and then from very highly engineered living human cellular tissues. More recently, they consist of biosynthetic materials that are combinations of silicone, collagen and chondroitin. The list of xenograft materials as well as minimally manipulated human tissues, such as human skin-, amniotic- and placental-based products, has grown exponentially. Over the last 5 years, truly synthetic materials have become part of the armamentarium available for closing large wounds. The first notable product in this category was made of polyurethane. These purely synthetic products do not have any components made of naturally occurring structures, such as collagen. In this review, we seek to create a rudimentary framework in which to understand these synthetic products and to review the current literature that supports the use of these novel yet intriguing therapies.

Further evidence that wound size and duration are strong prognostic markers of diabetic foot ulcer healing.

Diabetic foot ulcers (DFU) are a critical problem for those with diabetes mellitus. Predicting the healing likelihood of a DFU is important to implementing appropriate care, allocating resources, having access to advanced therapies, having successful clinical trials, calibrating clinical trial results, and providing information to administrative entities on patient and provider outcomes. Prognostic modelling can also be important when attempting to compare results across trials or care centres. In a prospective cohort study, we demonstrate and replicate that simple wound characteristics like wound area and wound duration can be used to predict wound healing by the 16th week of care. The models were based on previous literature and replicated using a machine learning algorithm. The use of wound duration and wound area in a prognostic model continues to be important when comparing study results, centre-based outcomes, as well as designing clinical trials.

Skin Expansion Technology in Acute Burns and Chronic Wounds.

The ability to grow skin has long been a topic of study and therapeutic interest. Currently, the main ways of doing this are 1) by placing tissue-expansion devices in the subcutaneous space and expanding skin over time, which can then be moved to cover contiguous structures, and 2) via processes that require relatively long (30 days) incubation periods to grow the patient's autogenous skin into laminar sheets. Over the past five years, there have been significant developments in the ability to expand skin cells, either at the bedside or in the laboratory, but much more rapidly than with previous methods. We explore and discuss the current skin cell-expansion techniques, focusing on point-of-care therapeutic interventions that can be used in the burn population as well as the chronic wound population, hair follicle stem-cell incubation techniques and studies supporting this therapy, as well as micro bullae grafting, and morcellated skin cell therapy. The current data supporting these therapeutic interventions and their current direction are outlined in detail.

Fetal bovine acellular dermal matrix for the closure of diabetic foot ulcers: a prospective randomised controlled trial.

AIM: The purpose of this clinical trial was to evaluate the safety and efficacy of a fetal bovine acellular dermal matrix (FBADM) plus standard of care (SOC) for treating hard-to-heal diabetic foot ulcers (DFUs). METHOD: A prospective, multi-centre, randomised controlled trial was carried out. The study included a 2-week run-in period, a 12-week treatment phase and a 4-week follow-up phase. The primary endpoint was complete wound closure at 12 weeks. RESULTS: Twenty-one US sites enrolled and randomised 226 patients with hard-to-heal DFUs. The study was terminated early due to the COVID-19 pandemic, which led to a modified intent-to-treat (mITT) population of 207 patients, with 103 in the FBADM group and 104 in the SOC group. Of these participants, 161 completed the study per protocol (mPP population), with 79 receiving FBADM, and 82 without. At the first analysis point, patients treated with FBADM were found to be significantly more likely to achieve complete wound closure compared with SOC alone (mITT: 45.6% versus 27.9% p=0.008; mPP: 59.5% versus 35.6% p=0.002). The difference in outcome yielded an odds ratio of 2.2 (95% confidence interval (CI): 1.2, 3.9; p=0.008). Median time to closure within 12 weeks was 43 days for the FBADM group compared to 57 days for the SOC group (p=0.36). The median number of applications of FBADM to achieve closure was one. Adverse events were similar between groups and no product-related serious adverse events occurred. CONCLUSIONS: These results indicate that in many cases a single application of FBADM in conjunction with SOC offers a safe, faster and more effective treatment of DFUs than SOC alone.

Effect of Topical Oxygen Therapy on Chronic Wounds.

Over the past three decades, there has been a growing interest in the use of oxygen therapy to promote wound healing. Although the most commonly recognized oxygen therapy for the treatment of chronic wounds is hyperbaric oxygen therapy, topical oxygen therapy has a greater level of evidence supporting its use in chronic wound care. Still, it is imperative that these two treatment modalities be recognized not merely as competitors, but as distinct therapeutic entities. Through personal experience and a thorough literature review, we investigated the use of topical oxygen therapy in the management of chronic wounds. The benefits of using topical oxygen therapy have been demonstrated in patients with diabetic foot ulcers, ischemic ulcers, post-revascularization ulcers, and pressure ulcers. There are several topical oxygen devices currently on the market that are versatile, relatively low-risk, and generally well-tolerated by patients. While these devices have been used in the treatment of chronic wounds at different locations and of different etiologies, other uses of these devices are still being investigated. Topical oxygen therapy is yet another tool in our arsenal to be used in treating difficult to heal chronic wounds and could potentially be used more readily.

The Role of Intermittent Pneumatic Compression in the Treatment of Lower Extremity Chronic Wounds.

Intermittent pneumatic compression devices (IPC) are often used as noninvasive adjuncts in patients with lymphedema, and more recently with venous stasis disease, to promote flow and reduce the adverse effects of interstitial edema associated with both disorders. We will be focusing on lower extremity wounds associated with venous and/or lymphatic disease, the combination often referred to as "lymphophlebitic" disease, and the treatment effect of IPC on this disease process and its sequelae. The function and purpose of pneumatic compression is closely examined along with a variety of pneumatic compression devices that currently exist in the market. A thorough review of the literature was conducted to evaluate the utility of intermittent pneumatic compression in the treatment of lower extremity venous stasis ulcers. Additionally, the author describes personal experience with the use of pneumatic compression on 10 patients with venous stasis ulcers at a single center. There is significant data supporting the use of IPC in patients with lymphophlebitic disease. Overall, ideal patient selection may be crucial. Previous data has shown that patients with high body mass index (>33 kg/m2) and poor functional status (walking less than 200m a day) are related to poor ulcer healing. Therefore, a study that looks primarily at this group (as our small quality assurance [QA] project did) may show increased benefit in this population. It is clear that IPC is of benefit to some patient cohorts with lymphophlebitic disease. This advanced therapy would help patients who have failure of their calf muscle pump and an inability to improve it through other means. However, it is only part of an algorithm that includes: direct wound bed management, moisture control, possible primary venous disease intervention, physical therapy, weight loss, and improved nutrition.

The Evidence for Antimicrobial and Hard to Infect Regenerative Matrices.

Preparation of the wound bed is a key step in the use of cell- and tissue-based therapy (CTP). In particular, good pre-application debridement is an essential component of CTP. However, there are many situations in which the wound bed is not adequately debrided, including trauma, burn, and in cases of chronic wounds with significant biofilm. In the setting of inadequate wound bed preparation, the use of a CTP that has either added or intrinsic antimicrobial properties is attractive. Some CTPs include added antimicrobial agents such as PHMB or silver, while others have intrinsic antimicrobial components, such as Omega 3 fatty acids. In addition, some wound-covering dressings are completely synthetic, and therefore simply do not become infected. A full understanding of the basic science and clinical data supporting the use of these therapies is important for the advanced wound care practitioner.

Fish skin grafts compared to human amnion/chorion membrane allografts: A double-blind, prospective, randomized clinical trial of acute wound healing.

Chronic, nonhealing wounds consume a great deal of healthcare resources and are a major public health problem, associated with high morbidity and significant economic costs. Skin grafts are commonly used to facilitate wound closure. The grafts can come from the patient's own skin (autograft), a human donor (allograft), or from a different species (xenograft). A fish skin xenograft from cold-water fish (Atlantic cod, Gadus morhua) is a relatively recent option that shows promising preclinical and clinical results in wound healing. Chronic wounds vary greatly in etiology and nature, requiring large cohorts for effective comparison between therapeutic alternatives. In this study, we attempted to imitate the status of a freshly debrided chronic wound by creating acute full-thickness wounds, 4 mm in diameter, on healthy volunteers to compare two materials frequently used to treat chronic wounds: fish skin and dHACM. The purpose is to give an indication of the efficacy of the two therapeutic alternatives in the treatment of chronic wounds in a simple, standardized, randomized, controlled, double-blind study. All volunteers were given two identical punch biopsy wounds, one of which was treated with a fish skin graft and the other with dehydrated human amnion/chorion membrane allograft (dHACM). In the study, 170 wounds were treated (85 wounds per group). The primary endpoint was defined as time to heal (full epithelialization) by blinded assessment at days 14, 18, 21, 25, and 28. The superiority hypothesis was that the fish skin grafts would heal the wounds faster than the dHACM. To evaluate the superiority hypothesis, a mixed Cox proportional hazard model was used. Wounds treated with fish skin healed significantly faster (hazard ratio 2.37; 95% confidence interval: (1.75-3.22; p = 0.0014) compared with wounds treated with dHACM. The results show that acute biopsy wounds treated with fish skin grafts heal faster than wounds treated with dHACM.

One-year safety, healing and amputation rates of Wagner 3-4 diabetic foot ulcers treated with cryopreserved umbilical cord (TTAX01).

An open label, multicenter 16-week trial of cryopreserved human umbilical cord (TTAX01) was previously undertaken in 32 subjects presenting with a Wagner grade 3 or 4 diabetic foot ulcer, with 16 (50%) of these having confirmed closure following a median of one product application (previous study). All but two subjects (30/32; 94%) consented to participate in this follow-up study to 1-year postexposure. No restrictions were placed on treatments for open wounds. At 8-week intervals, subjects were evaluated for adverse events (AEs) and wound status (open or closed). Average time from initial exposure to end of follow-up was 378 days (range 343-433), with 29 of 30 (97%) subjects completing a full year. AEs were all typical for the population under study, and none were attributed to prior exposure to TTAX01. One previously healed wound re-opened, one previously unconfirmed closed wound remained healed, and nine new wound closures occurred, giving 25 of 29 (86.2%) healed in the ITT population. Three of the new closures followed the use of various tissue-based products. Three subjects whose wounds were healed required subsequent minor amputations due to osteomyelitis, one of which progressed to a major amputation (1/29; 3.4%). One additional subject underwent two minor amputations prior to healing. Overall, the study found TTAX01 to be safe in long-term follow-up and associated with both a low rate of major amputation and a higher than expected rates of healing.

A dual compression system: preliminary clinical insights from the US.

There is growing evidence on an interconnection between the venous and lymphatic systems in venous leg ulceration, and the possible effects of prolonged oedema and lymphatic impairment in delayed wound healing. Compression therapy is a widely accepted treatment for venous and lymphatic disorders, as it decreases recurrence rates and prolongs the interval between recurrences. Compression bandages improve venous return, increase the volume and rate of venous flow, reduce oedema and stimulate anti-inflammatory processes. The pressure at the interface (IP) of the bandage and the skin is related to the elastic recoil of the product used and its resistance to expansion. The pressure difference between the IP in the supine and standing positions is called the static stiffness index (SSI). Elastic materials provide little resistance to muscle expansion during physical activity, resulting in small pressure differences between resting and activity, with an SSI <10mmHg. Stiff, inelastic materials with a stretch of <100% resist the increase of muscle volume during physical activity, producing higher peak pressures, an SSI of >10mmHg and a greater haemodynamic benefit than elastic systems. UrgoK2 is a novel dual-layer high-compression system consisting of an inelastic (short stretch) and elastic (long stretch) bandage, resulting in sustained tolerable resting pressure and elevated working pressures over extended wear times. It is indicated for the treatment of active venous leg ulcers and the reduction of chronic venous oedema. Each bandage layer has a visual aid to enable application at the correct pressure level. Published European studies have assessed this compression system, exploring its consistency of application, tolerability and efficacy. This article presents the first reports of health professionals' clinical experience of using the compression system in the US, where it has been recently launched. Initial feedback is promising.

Cryopreserved Allograft Use in Vascular Surgery.

In vascular surgery, bypass procedures are standard treatments for many arterial and venous diseases. The choice of conduit for the bypass operation is fundamental in planning for the appropriate intervention for each individual patient. Although an autogenous conduit is superior, this option is not available in many patients, and prosthetic grafts have been the preferred conduit in a variety of clinical situations. However, since prosthetic graft infections are seen in all realms of vascular surgery, from arteriovenous access to aortic graft infections and lower-extremity bypass infections, cryopreserved arterial and venous allografts, which are relatively resistant to infection, have become the conduit of choice. This discussion will focus on the clinical applications of cryopreserved allografts in vascular surgery, specifically lower-extremity peripheral bypass, aortic disease, and dialysis access.

An open-label trial of cryopreserved human umbilical cord in the treatment of complex diabetic foot ulcers complicated by osteomyelitis.

Clinical trials of potential new therapies for diabetic foot ulcers rarely enroll patients whose wounds extend to muscle, fascia, or bone with clinical and radiographic evidence of underlying osteomyelitis. An open-label, multicenter trial of cryopreserved human umbilical cord (TTAX01) was undertaken in 32 subjects presenting with such complex wounds with a mean duration of 6.1 ± 9.0 (range: 0.2-47.1) months and wound area at screening of 3.8 ± 2.9 (range: 1.0-9.6) cm2 . Aggressive surgical debridement at baseline resulted in 17 minor amputations and an increase in mean wound area to 7.4 ± 5.8 (range: 1.1-28.6) cm2 . All subjects were placed on systemic antibiotics for at least 6 weeks in conjunction with baseline application of TTAX01. Repeat applications were made at no less than 4-week intervals over the 16-week trial. Initial closure occurred in 18 of 32 (56%) wounds, with 16 (50%) of these having confirmed closure in 16 weeks with a median of one-product application. Cases with biopsy confirmed osteomyelitis (n = 20) showed initial closure in 12 (60%) wounds and confirmed closure in 10 (50%) wounds. Four of the five ulcers presenting as recurrences experienced confirmed closure. Mean overall time to healing was 12.8 ± 4.3 weeks. Mean wound area reduction from baseline was 91% for all wounds. Of the 16 wounds without confirmed closure during the 16-week treatment period, five (31.3%) achieved 99-100% wound area reduction by their final visit. The product was well tolerated. Two minor amputations occurred during the study period due to recurrent or persistent osteomyelitis; however, there were no major amputations.

PLX-PAD Cell Treatment of Critical Limb Ischaemia: Rationale and Design of the PACE Trial.

BACKGROUND: Critical limb ischaemia (CLI) is a life threatening condition with a considerable risk of major amputation and death. Besides revascularisation, no treatment has been proven to reduce the risks. Therapeutic angiogenesis by gene or cell therapy has not demonstrated definitive evidence in randomised controlled trials. PLX-PAD is an "off the shelf" allogeneic placental derived, mesenchymal like cell therapy, which, in preclinical studies, has shown pro-angiogenic, anti-inflammatory, and regenerative properties. Favourable one year amputation free survival (AFS), and trends in reduction of pain scores and increase of tissue perfusion have been shown in two small, open label, phase I trials. METHODS: The PACE study is a phase III randomised, double blind, multicentre, multinational placebo controlled, parallel group study to evaluate the efficacy, tolerability, and safety of intramuscular injections of PLX-PAD cells to treat patients with atherosclerotic CLI with minor tissue loss (Rutherford Category 5) up to the ankle level, who are unsuitable for revascularisation or carry an unfavourable risk benefit for that treatment. The study will enroll 246 patients, who after screening are randomised in a ratio of 2:1 to treatment with intramuscular injections of PLX-PAD 300 × 106 cells or placebo on two occasions, eight weeks apart. The primary efficacy endpoint is time to major amputation or death (amputation free survival), which will be assessed in follow up of at least 12 months and up to 36 months. CONCLUSIONS: Based on favourable pre-clinical and initial clinical study results, the PACE phase III randomised controlled trial will evaluate placenta derived PLX-PAD cell treatment in patients with critical limb ischaemia, with an unfavourable risk benefit for revascularisation. Clinicaltrials.gov: NCT03006770.