Rapid healing of venous ulcers and lack of clinical rejection with an allogeneic cultured human skin equivalent. Human Skin Equivalent Investigators Group

Real-world data analysis of bilayered living cellular construct and fetal bovine collagen dressing treatment for pressure injuries: a comparative effectiveness study

Aim: To determine the effectiveness of bilayered living cellular construct (BLCC) versus a fetal bovine collagen dressing (FBCD) in pressure injuries (PRIs). Methods: A real-world data study was conducted on 1352 PRIs analyzed digitally. 1046 and 306 PRIs were treated with BLCC and FBCD, respectively. Results: Cox healing for BLCC (n = 1046) was significantly greater (p < 0.0001) at week 4 (13 vs 7%), 8 (29 vs 17%), 12 (42 vs 27%), 24 (64 vs 45%), and 36 (73 vs 56%). The probability of healing increased by 66%, (hazard ratio = 1.66 [95% CI (1.38, 2.00)]; p < 0.0001. Time to healing was 162 days for FBCD and 103 days for BLCC showing a 36% reduction in time to healing with BLCC; (p < 0.0001). Conclusion: BLCC significantly improved healing of PRIs versus FBCD.

Macromolecular crowding in human tenocyte and skin fibroblast cultures: A comparative analysis

Although human tenocytes and dermal fibroblasts have shown promise in tendon engineering, no tissue engineered medicine has been developed due to the prolonged ex vivo time required to develop an implantable device. Considering that macromolecular crowding has the potential to substantially accelerate the development of functional tissue facsimiles, herein we compared human tenocyte and dermal fibroblast behaviour under standard and macromolecular crowding conditions to inform future studies in tendon engineering. Basic cell function analysis made apparent the innocuousness of macromolecular crowding for both cell types. Gene expression analysis of the without macromolecular crowding groups revealed expression of tendon related molecules in human dermal fibroblasts and tenocytes. Protein electrophoresis and immunocytochemistry analyses showed significantly increased and similar deposition of collagen fibres by macromolecular crowding in the two cell types. Proteomics analysis demonstrated great similarities between human tenocyte and dermal fibroblast cultures, as well as the induction of haemostatic, anti-microbial and tissue-protective proteins by macromolecular crowding in both cell populations. Collectively, these data rationalise the use of either human dermal fibroblasts or tenocytes in combination with macromolecular crowding in tendon engineering.

Dehydrated human amnion/chorion membrane to treat venous leg ulcers: a cost-effectiveness analysis

OBJECTIVE

To evaluate the cost-effectiveness of dehydrated human amnion/chorion membrane (DHACM) in Medicare enrolees who developed a venous leg ulcer (VLU).

METHOD

This economic evaluation used a four-state Markov model to simulate the disease progression of VLUs for patients receiving advanced treatment (AT) with DHACM or no advanced treatment (NAT) over a three-year time horizon from a US Medicare perspective. DHACM treatments were assessed when following parameters for use (FPFU), whereby applications were initiated 30-45 days after the initial VLU diagnosis claim, and reapplications occurred on a weekly to biweekly basis until completion of the treatment episode. The cohort was modelled on the claims of 530,220 Medicare enrolees who developed a VLU between 2015-2019. Direct medical costs, quality-adjusted life years (QALYs), and the net monetary benefit (NMB) at a willingness-to-pay threshold of $100,000/QALY were applied. Univariate and probabilistic sensitivity analyses (PSA) were performed to test the uncertainty of model results.

RESULTS

DHACM applied FPFU dominated NAT, yielding a lower per-patient cost of $170 and an increase of 0.010 QALYs over three years. The resulting NMB was $1178 per patient in favour of DHACM FPFU over the same time horizon. The rate of VLU recurrence had a notable impact on model uncertainty. In the PSA, DHACM FPFU was cost-effective in 63.01% of simulations at the $100,000/QALY threshold.

CONCLUSION

In this analysis, DHACM FPFU was the dominant strategy compared to NAT, as it was cost-saving and generated a greater number of QALYs over three years from the US Medicare perspective. A companion VLU Medicare outcomes analysis revealed that patients who received AT with a cellular, acellular and matrix-like product (CAMP) compared to patients who received NAT had the best outcomes. Given the added clinical benefits to patients at lower cost, providers should recommend DHACM FPFU to patients with VLU who qualify. Decision-makers for public insurers (e.g., Medicare and Medicaid) and commercial payers should establish preferential formulary placement for reimbursement of DHACM to reduce budget impact and improve the long-term health of their patient populations dealing with these chronic wounds.

DECLARATION OF INTEREST

Support for this analysis was provided by MiMedx Group, Inc., US. JLD, and RAF are employees of MiMedx Group, Inc. WHT, BH, PS, BGC and WVP were consultants to MiMedx Group, Inc. VD, AO, MRK, JAN, NW and GAM served on the MiMedx Group, Inc. Advisory Board. MRK and JAN served on a speaker's bureau. WVP declares personal fees and equity holdings from Stage Analytics, US.

Applications of Scaffolds in Tissue Engineering: Current Utilization and Future Prospective

Current regenerative medicine tactics focus on regenerating tissue structures pathologically modified by cell transplantation in combination with supporting scaffolds and biomolecules. Natural and synthetic polymers, bioresorbable inorganic and hybrid materials, and tissue decellularized were deemed biomaterials scaffolding because of their improved structural, mechanical, and biological abilities.Various biomaterials, existing treatment methodologies and emerging technologies in the field of Three-dimensional (3D) and hydrogel processing, and the unique fabric concerns for tissue engineering. A scaffold that acts as a transient matrix for cell proliferation and extracellular matrix deposition, with subsequent expansion, is needed to restore or regenerate the tissue. Diverse technologies are combined to produce porous tissue regenerative and tailored release of bioactive substances in applications of tissue engineering. Tissue engineering scaffolds are crucial ingredients. This paper discusses an overview of the various scaffold kinds and their material features and applications. Tabulation of the manufacturing technologies for fabric engineering and equipment, encompassing the latest fundamental and standard procedures.

A simple index to predict healing in venous leg ulcers: a secondary analysis from four randomised controlled trials

OBJECTIVE

To investigate whether the use of a simple baseline measurement predicts venous leg ulcer healing at 12 and 24 weeks.

METHOD

This was a secondary analysis of a cohort of four randomised controlled trials (RCTs) of treatments adjuvant to compression. Self-reported ulcer duration, and measured ulcer length and width, to calculate estimated ulcer area, were used to obtain a Margolis index score. The score created three prognostic strata for likelihood to heal within 24 weeks, and the number of participants healed and time-to-healing were compared.

RESULTS

There were a total of 802 participants across the four RCTs-408 (50.9%) in two 12-week trials and 394 (49.1%) in two 24-week trials. The mean age of participants was 63.7±17.6 years, and 372 were female (46.4%). The Margolis index score at baseline was 0 for 320 participants (predicted normal healing); 1 for 334 participants; and 2 for 148 participants (both 1 and 2 predicted slow-to-heal). Overall, 248 (77.5%) of those participants who scored 0 at baseline healed within 24 weeks, compared with 182 (54.5%) of participants who scored 1, and 30 (20.3%) participants who scored 2. The median time-to-healing was 40 (24-62) days, 57 (35-100) days and 86.5 (56-151) days, respectively. The area under the receiver operating characteristic curve was 0.69 and 0.77, respectively, for the 12 and 24 week trials.

CONCLUSION

A simple baseline index identifies participants with normal or slow-to-heal wounds and could be used to demonstrate prognostic balance between treatment groups in trials. This approach could also be used in clinical practice to assist with managing expectations and for early identification of patients who may best benefit from adjuvant treatments.

Skin substitutes as treatment for chronic wounds: current and future directions

Chronic wounds such as diabetic foot ulcers and venous leg ulcers place a significant burden on the healthcare system and in some cases, have 5-year mortality rates comparable to cancer. They negatively impact patients' quality of life due to pain, odor, decreased mobility, and social isolation. Skin substitutes are an advanced therapy recommended for wounds that fail to show decrease in size with standard care. The choice of substitute used should be based on evidence, which often differs based on wound etiology. There are more than 75 skin substitutes currently available, and that number is rising. In this review, we discuss current management and future directions of chronic wounds while providing a review of available randomized control trial data for various skin substitutes.

Allogeneic transplantation of epidermal cell sheets followed by endoscopic submucosal dissection to prevent severe esophageal stricture in a porcine model

Introduction

Endoscopic submucosal dissection (ESD) is a minimally invasive treatment for early esophageal cancer. However, large mucosal defects after esophageal ESD result in refractory strictures. In the present study, we histologically evaluated the endoscopic transplantation of allogeneic epidermal cell sheets (ECSs) as a feasible therapy for preventing esophageal stricture after circumferential ESD in a porcine model.

Methods

Epidermal cells were isolated from the skin tissue of allogeneic pigs and cultured on temperature-responsive cell culture inserts for 2 weeks. Transplantable ECSs were harvested by reducing the temperature and endoscopically transplanting the sheets to ulcer sites immediately after esophageal ESD. The engraftment of transplanted ECSs was then evaluated in two pigs at 7 days after transplantation. Next, ten pigs were divided into two groups to evaluate the endoscopic transplantation of allogeneic ECSs for the prevention of esophageal strictures after ESD. Allogeneic ECSs were transplanted immediately after esophageal ESD in the transplantation group (n = 5), whereas the control group (n = 5) did not undergo transplantation.

Results

Most of the transplanted allogeneic ECSs were successfully engrafted at the ulcer sites in the early phase. Fluorescence in situ hybridization analysis revealed that several allogeneic cells were present in the transplanted area at 7 days after ESD. At 14 days after ESD, significant differences in body weight loss, dysphagia scores, and mucosal strictures were observed between the control and transplantation groups. Transplanting allogeneic ECSs after esophageal ESD promotes mucosal healing and angiogenesis and prevents excessive inflammation and granulation tissue formation.

Conclusions

Endoscopic and histological analyses revealed that allogeneic ECSs promoted artificial ulcer healing after ESD, preventing esophageal strictures after ESD.

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Large mucosal defects of the esophagus cause severe strictures.

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Allogeneic epidermal cell sheets promote esophageal mucosal healing.

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Allogeneic epidermal cell sheets induce angiogenesis in esophageal ulcers.

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Allogeneic epidermal cell sheets prevent excessive inflammation in esophageal ulcers.

A Multicenter, Randomized, Controlled, Clinical Trial Evaluating Dehydrated Human Amniotic Membrane in the Treatment of Venous Leg Ulcers

BACKGROUND

This randomized controlled trial evaluated the safety and effectiveness of weekly and biweekly applications of dehydrated human amnion and chorion allograft (dHACA) plus standard of care compared to standard of care alone on chronic venous leg ulcers.

METHODS

This open-label randomized controlled trial included patients with chronic venous leg ulcers at eight wound care centers across the United States. The primary endpoint was the proportion of healed ulcers at 12 weeks. Secondary endpoints included the proportion of ulcers achieving 40 percent closure at 4 weeks and the incidence of adverse events.

RESULTS

Among 101 patients screened for eligibility, 60 were eligible and enrolled. At 12 weeks, significantly more venous leg ulcers healed in the two dHACA-treated groups (75 percent) than in the standard-of-care group (30 percent) ( p = 0.001) even after adjustment for wound area ( p = 0.002), with an odds ratio of 8.7 (95 percent CI, 2.2 to 33.6). There were no significant differences in the proportion of wounds with percentage area reduction greater than or equal to 40 percent at 4 weeks among all groups. The adverse event rate was 63.5 percent. Among the 38 adverse events, none were graft or procedure related, and all were resolved with appropriate treatment.

CONCLUSIONS

dHACA and standard of care, either applied weekly or biweekly, significantly healed more venous leg ulcers than standard of care alone, suggesting that the use of aseptically processed dHACA is advantageous and a safe and effective treatment option in the healing of chronic venous leg ulcers.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, I.

[Beyond esthetics-Regenerative medicine for severe diseases of the adnexa oculi]

BACKGROUND

Restoration of eyelid and lacrimal functions are important steps on the way to an intact ocular surface. Clinically available substitute tissues or therapeutic options for eyelid reconstruction and lacrimal gland regeneration often reach their limits in patients with severe diseases of the adnexa oculi. Several approaches in regenerative medicine have been intensively researched and clinically tested in recent years. These range from reconstructive approaches with novel tissue matrices in the field of eyelid surgery to stem cell therapies to regenerate lacrimal gland function.

MATERIAL AND METHODS

The state of the art in the current literature is presented and an overview of clinically applied or currently researched tissues for eyelid reconstruction is given. Furthermore, approaches in stem cell therapy of the lacrimal gland as well as own results are presented.

RESULTS

Acellular dermis has been successfully used for eyelid reconstruction and represents a viable option in cases of limited availability of autologous tissue. In vitro grown cellular constructs or tissues with genetically modified cells have already been successfully applied in dermatology for the treatment of burns or severe genodermatoses. First studies on stem cell therapy for severe dry eye in Sjögren syndrome showed a safe and effective application of mesenchymal stem cells by injection into the lacrimal gland.

CONCLUSION

Due to the limitations of currently available replacement tissues, there is a clinical need for the development of new materials for adnexa oculi reconstruction. Constructs grown in vitro with allogeneic and/or genetically engineered cells are slowly making their way into clinical practice. The efficacy and mode of action of stem cells in severe dry eye are subject matters of current clinical trials.

Bi-layered living cellular construct resulted in greater healing in an alloxan-induced diabetic porcine model

Tissue-engineered skin constructs, including bi-layered living cellular constructs (BLCC) used in the treatment of chronic wounds, are structurally/functionally complex. While some work has been performed to understand their mechanisms, the totality of how BLCC may function in wound healing remains unknown. To this end, we have developed a delayed wound healing model to test BLCC cellular and molecular mechanisms of action. Diabetes was chemically-induced using alloxan in Yucatan miniature pigs, and full-thickness wounds were generated on their dorsum. These wounds were either allowed to heal by secondary intention alone (control) or treated with a single or multiple treatments of a porcine autologous BLCC. Results indicated a single treatment with porcine BLCC resulted in statistically significant wound healing at day 17, while four treatments resulted in statistically significant healing on days 10, 13, and 17 compared to control. Statistically accelerated wound closure was driven by re-epithelialisation rather than contraction or granulation. This porcine diabetic model and the use of a porcine BLCC allowed evaluation of healing responses in vivo without the complications typically seen with either xenogenic responses of human/animal systems or the use of immune compromised animals, expanding the knowledge base around how BLCC may impact chronic wounds.

Chronic wounds

Chronic wounds are characterized by their inability to heal within an expected time frame and have emerged as an increasingly important clinical problem over the past several decades, owing to their increasing incidence and greater recognition of associated morbidity and socio-economic burden. Even up to a few years ago, the management of chronic wounds relied on standards of care that were outdated. However, the approach to these chronic conditions has improved, with better prevention, diagnosis and treatment. Such improvements are due to major advances in understanding of cellular and molecular aspects of basic science, in innovative and technological breakthroughs in treatment modalities from biomedical engineering, and in our ability to conduct well-controlled and reliable clinical research. The evidence-based approaches resulting from these advances have become the new standard of care. At the same time, these improvements are tempered by the recognition that persistent gaps exist in scientific knowledge of impaired healing and the ability of clinicians to reduce morbidity, loss of limb and mortality. Therefore, taking stock of what is known and what is needed to improve understanding of chronic wounds and their associated failure to heal is crucial to ensuring better treatments and outcomes.

Pressure Injuries and Management after Spinal Cord Injury

Spinal cord injury (SCI) results in motor paralysis and sensory loss that places individuals at particularly high risk of pressure injuries. Multiple comorbidities associated with autonomic, cardiovascular, pulmonary, endocrine, gastrointestinal, genitourinary, neurological, and musculoskeletal dysfunction makes it even more likely that pressure injuries will occur. This manuscript will review the structure and function of the integumentary system, and address the multidisciplinary approach required to prevent and manage pressure injuries in this vulnerable population.

Overview of Biologic Agents Used in Skin and Soft Tissue Reconstruction

Wound healing is a highly complex process mediated by cellular interactions at the microscopic level. Increased understanding of wound healing physiology has served as the foundation for translational research to develop biologic wound care technologies that have profoundly affected patient care. As the reader will see throughout this series in Seminars in Plastic Surgery , biologic wound technologies have broad applications and have greatly impacted the reconstructive ladder. Despite their frequent use, many surgeons lack familiarity with the myriad of products available on the market along with each product's relative advantages and shortcomings. This overview will discuss the classification of biologic wound agents used to reconstruct defects of the skin and soft tissue along with the advantages and disadvantages associated with their use.

Use of Biologic Agents in Nasal and Scalp Reconstruction

Oncologic reconstruction of the nose and scalp following Mohs micrographic surgery poses a significant challenge for plastic surgeons. While these defects are traditionally reconstructed using primary closure techniques, skin grafts, local flaps, pedicled flaps, and free tissue transfer, the incorporation of biologic healing wound agents such as Integra and Cytal provides patients and surgeons with alterative reconstructive options without additional donor site morbidity. Herein, we review the use of biologic agents used in soft tissue reconstruction of the nose and scalp following Mohs surgery.

Allogeneic ABCB5+ mesenchymal stem cells for treatment-refractory chronic venous ulcers: a phase I/IIa clinical trial

A significant number of chronic venous ulcers (CVUs) fail to heal despite of guideline-conform standard of care. Skin-derived ABCB5+ mesenchymal stem cells (MSCs) can dampen the sustained IL-1β-driven inflammation present in chronic wounds. Based on their wound healing-facilitating effects in a mouse CVU model and an autologous first-in-human study, ABCB5+ MSCs have emerged as a potential candidate for cell-based advanced therapy of non-healing CVUs. In the present interventional, multicenter, single-arm, phase I/IIa clinical trial, subjects whose CVU had emerged as standard therapy-resistant received one or two topical applications of 1×106 allogeneic ABCB5+ MSCs/cm2 wound area in addition to standard treatment. Out of 83 treatment-emergent adverse events, only three were judged related to the cell product; they were mild or moderate and recovered without sequelae. Wound size markedly decreased from baseline to week 12, resulting in a median wound size reduction of 76% (full analysis set, N=31), 78% (per-protocol set, N=27) and 87% (subset of responders; n=21). In conclusion, the study treatment was well tolerated and safe. The treatment elicited a profound wound size reduction within 12 weeks, identifying ABCB5+ MSCs as a potential candidate for adjunctive therapy of otherwise incurable CVUs. These results justify the conduct of a larger, randomized, controlled trial to confirm clinical efficacy.

Growth factors for treating chronic venous leg ulcers: A systematic review and meta-analysis

Chronic venous leg ulcers (VLU) are wounds that commonly occur due to venous insufficiency. Many growth factors have been introduced over the past two decades to treat VLU. This systematic review and meta-analysis evaluates the impact of growth factor treatments of VLU in comparison to control for complete wound healing, percent reduction in wound area, time to wound healing, and adverse events. A systematic review and meta-analysis of randomised trials was conducted. MEDLINE and EMBASE were searched up to December 2020. Studies were included if they compared a growth factor versus placebo or standard care in patients with VLU. From 1645 articles, 13 trials were included (n = 991). There was a significant difference between any growth factor and placebo in complete wound healing (P = 0.04). Any growth factor compared to placebo significantly increased the likelihood of percent wound reduction by 48.80% (P = <0.00001). There was no difference in overall adverse event rate. Most comparisons have low certainty of evidence according to Grading of Recommendations, Assessment, Development, and Evaluation. This meta-analysis suggests that growth factors have a beneficial effect in complete wound healing of VLU. Growth factors may also increase percent reduction in wound area. The suggestion of benefit for growth factors identified in this review is not a strong one based on the low quality of evidence.

Chyloid Fat Carried Adipose-Derived Mesenchymal Stem Cells Accelerate Wound Healing Via Promoting Angiogenesis

ABSTRACT

Impaired wound healing is responsible for significant morbidity and mortality worldwide. It is necessary to find a stable, efficient, and safe method to promote soft tissue wound healing. Fat grafting has become increasingly popular in contouring procedures. However, more recently, there has been an emphasis on its regenerative potential. In this study, we established the wound healing model using nude mice. Hematoxylin and eosin and Masson stainings were performed to assess the effect of chyloid fat on the histology of wound healing. A laser Doppler perfusion imager was used to evaluate the blood perfusion of wounds. Immunohistochemistry was carried out to detect the expression of CD31 in wound tissues. The results suggested that after treatment with granule fat or chyloid fat, wound healing was accelerated and blood perfusion was promoted. In addition, granule fat or chyloid fat treatment promoted the angiogenesis of the wound. In addition, we evaluated the amount of adipose-derived mesenchymal stem cells in chyloid fat and granule fat. It was found that chyloid fat contained more adipose-derived mesenchymal stem cells than granule fat did. In conclusion, we proved that chyloid fat could significantly accelerate the wound healing process via promoting angiogenesis. The adipose-derived mesenchymal stem cell plays a critical role in this effect of chyloid fat.

Comparison of Skin Substitutes for Acute and Chronic Wound Management

Chronic and acute wounds, such as diabetic foot ulcers and burns, respectively, can be difficult to treat, especially when autologous skin transplantations are unavailable. Skin substitutes can be used as a treatment alternative by providing the structural elements and growth factors necessary for reepithelialization and revascularization from a nonautologous source. As of 2020, there are 76 commercially available skin substitute products; this article provides a review of the relevant literature related to the major categories of skin substitutes available.

Clinical and cost efficacy of advanced wound care matrices in the treatment of venous leg ulcers: a systematic review

BACKGROUND

Venous leg ulcers (VLUs) are hard-to-heal, recurrent and challenging to treat. Advanced wound care matrices (AWCMs) have been developed to supplement conventional therapies. These costly AWCMs warrant careful comparison as healthcare expenditures are subjected to increasing scrutiny.

AIM

This study was designed to compare AWCMs in their ability to heal VLUs and their cost efficacy through a systematic review of randomised controlled trials (RCTs).

METHOD

An organised search of Medline, Cochrane Library, Central and CINAHL databases identified RCTs that compared AWCMs to standard compression therapy in the healing of VLUs. Bias was assessed using the Effective Public Health Practice Project (EPHPP) Quality Assessment Tool for Quantitative Studies. Eight studies analysing bilayered skin substitute (BSS) (Apligraf), dehydrated human amnion/chorion membrane (dHACM) (Epifix), human fibroblast-derived dermal substitute (HFDDS) (Dermagraft), extracellular wound matrix (ECM) (Oasis), advanced matrix (AM) (Talymed) and matrix wound dressing (MWD) (Promogran) met the inclusion criteria.

RESULTS

Four studies reported significant improvement over standard therapy: BSS, dHACM, ECM and AM. Incremental cost per additional successful treatment was determined for each trial, ranging from $2593 (MWD) to $210,800 (HFDDS).

CONCLUSION

Our consolidated analysis of eight major RCTs of AWCMs in the treatment of VLUs revealed a great variation in clinical and cost efficacy among these products. The included trials were inconsistent in methodology, and these limitations should be noted, but, in the absence of RCTs to compare these products, our systematic review may serve as a guide for practitioners who seek to optimise wound healing while considering cost efficacy.

Review of the Current Evidence for Topical Treatment for Venous Leg Ulcers

OBJECTIVE

The development of a venous leg ulcer (VLU) represents the most severe clinical manifestation of a chronic venous disease. Despite major progress, there is a limited understanding of VLU pathogenesis and wound healing biology. Treatment of VLUs remains a serious challenge for physicians of different specialties. This communication focuses on describing the rationale and scientific basis for topical wound care in the management of VLUs.

METHODS

A literature review was performed to summarize methods with proven efficacy in VLU management. A systematic literature search was also performed to identify new evidence from the randomized controlled trials published within 2014-2021. The scientific challenges, clinical practice concerns, economic obstacles, and possible directions for further research have been discussed.

RESULTS

Hundreds of topical products have been advertised for the treatment of VLUs. Published data on topical treatment of venous ulcers is insufficient, scattered, weak, and has significant methodological flaws. Forty-three randomized controlled trials on topical treatment of VLUs have been published within 2014-2021. Clinical practice guidelines need to be updated. Major gaps in knowledge have been identified, and suggestions for future research directions have been provided.

CONCLUSIONS

The American Venous Forum Research Committee would like to bring attention to topical wound care for VLUs as a critical gap in knowledge, and encourage scientists, practitioners, and industry to collaborate to fill this gap.

Topical cannabis-based medicines - A novel adjuvant treatment for venous leg ulcers: An open-label trial

Venous leg ulcers are highly prevalent lower limb integumentary wounds that remain challenging to heal despite the use of evidence-based compression therapies. A multitude of adjuvant treatments has been studied but none have demonstrated enough efficacy to gain adoption into treatment guidelines. Global attention on Cannabis-Based Therapies is increasing and has been driven by quantum scientific advancements in the understanding of the endocannabinoid signalling system. Topical Cannabis-Based Medicines represent a novel treatment paradigm for venous leg ulcers in terms of promoting wound closure. Fourteen complex patients with sixteen recalcitrant leg ulcers were treated with Topical Cannabis-Based Medicines in conjunction with compression bandaging, every second day, to both wound bed and peri-wound tissues. The cohort had a mean age of 75.8 years and was medically complex as reflected by a mean M3 multimorbidity index score of 2.94 and a mean Palliative Performance Scale score of 67.1%. Complete wound closure, defined as being fully epithelialized, was achieved among 11 patients (79%) and 13 wounds (81%) within a median of 34 days. All three remaining patients demonstrated progressive healing trends but were lost to follow-up. The treatments were well tolerated, and no significant adverse reactions were experienced. The rapid wound closure of previously non-healing venous leg ulcers among elderly and highly complex patients suggests that Topical Cannabis-Based Medicines may become effective adjuvants in conjunction with compression therapy. This may also indicate that they may have an even broader role within integumentary and wound management. Therefore, this treatment paradigm warrants being subjected to controlled trials.

A prospective clinical trial evaluating changes in the wound microenvironment in patients with chronic venous leg ulcers treated with a hypothermically stored amniotic membrane

Amniotic tissues have been long utilised to treat chronic wounds; however, there are few studies evaluating how the wound microenvironment responds to these therapies. The goal of this study was to evaluate the changes in wounds treated with a hypothermically stored amniotic membrane (HSAM). In this prospective single‐arm study, 15 female patients with venous leg ulcers were treated with HSAM from male donors and standard of care for 12 weeks. Over the course of the study, wound exudate was collected and evaluated using proteomic microarrays. Biopsies were collected during the course of treatment to detect the presence of HSAM tissue. By 4 weeks, 60% of subjects achieved 50% or greater reduction in wound size, and by 12 weeks, 53% of subjects achieved 100% re‐epithelialization. HSAM DNA was detected in 20% of biopsies as determined by the detection TSPY4, indicating HSAM was no longer present within the wound bed approximately 7 days from the last treatment for the majority of wounds. Proteomic analysis of wound exudate found that wounds on a healing trajectory had significantly higher levels of MMP‐10, MMP‐7, and TIMP‐4 and significantly lower levels of CX3CL1, FLT‐3 L, IL‐1ra, IL‐1a, IL‐9, IL‐2, IL‐3, MCP‐1, and TNF‐b compared with other wounds.

Treatment of venous leg ulcers using bilayered living cellular construct

Background: Venous leg ulcers (VLUs) present a significant economic burden on the US healthcare system and payers (US$14.9 billion). Aim: To evaluate the quality of life (QoL) of patients with VLUs; to analyze the limitations of standard of care (SOC) for VLUs; and to explain how using bilayered living cellular construct (BLCC) with SOC for treatment of VLUs can help heal more VLUs faster (than using SOC alone) as well as help improve QoL and help reduce the burden on the US healthcare system and payers. Materials & methods: This is a review study. The search was conducted in February 2020 by way of electronic databases to find relevant articles that provided information related to QoL of patients with VLUs, limitations of SOC for VLUs and economic analyses of using BLCC for treatment of VLUs. Results: VLUs impact patients' physical, functional and psychological status and reduce QoL. A total 75% of VLU patients who used SOC alone failed to achieve healing in a timely fashion, which led to increased healthcare costs and healthcare resource utilization. Although the upfront cost is high, the greater effectiveness of BLCC offsets the added cost of the product during the time period of the studies. Therefore, BLCC helps to improve the QoL of VLU patients. As an example, for every 100 VLU patients in a healthcare plan, the use of BLCC can create cost savings of US$1,349,829.51. Conclusion: Payers' coverage of BLCC results in reduction of the overall medical cost for treating VLU patients.

Open-label Venous Leg Ulcer Pilot Study Using a Novel Autolologous Homologous Skin Construct

Venous leg ulcers (VLUs) are often refractory to compression therapy, and their prevalence is increasing. An autologous homologous skin construct (AHSC) that uses the endogenous regenerative capacity of healthy skin has been developed to treat cutaneous defects, with a single application. The ability of AHSC to close VLUs with a single treatment was evaluated in an open-label, single-arm feasibility study to test the hypothesis that AHSC treatment will result in wound closure by providing healthy autologous tissue to the wound bed.

METHODS

Ten VLUs were treated with a single application of AHSC. A 1.5 cm2 full-thickness skin harvest from the proximal calf was collected and sent to a Food and Drug Administration-registered facility, where it was processed into AHSC and returned to the provider within 48 hours. AHSC was spread evenly across the wound and dressed with silicone. The primary endpoint was wound closure rate at 12 weeks. Wound closure was followed with 3-dimensional planimetry, and closure was confirmed by a panel of plastic surgeons. Additional endpoints followed for 12 weeks included graft take, harvest site closure, adverse event rate, complications, and patient-reported pain.

RESULTS

All 10 VLUs demonstrated successful graft take as evidenced by graft persisting in wound and harvest site closure. Eight VLUs exhibited complete closure within 12 weeks. One VLU that failed to heal with a prior split thickness skin graft closed within 13.5 weeks with AHSC. The mean time of closure was 34 days (95% confidence interval, 14-53). Pain improved by closure confirmation visit. There was 1 serious adverse event unrelated to the product or procedure.

CONCLUSION

This pilot study demonstrated that AHSC may be a viable single-application topical intervention for VLUs and warrants further investigation in larger, controlled studies.

Leg Ulcers in Sickle-Cell Disease: Treatment Update

Significance: Sickle-cell leg ulcers (SCLUs) are a severe, chronic, and recurrent complication of sickle-cell disease (SCD). There are no official recommendations for treatment. Recent Advances: Only a few studies with a high level of evidence have been conducted to evaluate treatment of SCLUs. However, several studies have been conducted with a high level of evidence to evaluate the efficacy of treatments in venous leg ulcers, and SCLUs could benefit from these treatments, especially when a venous incompetence or an edema is associated. Pathophysiology of SCLUs includes a vasculopathy related to chronic hemolysis and an endothelial dysfunction, which could be therapeutic approaches to SCLU treatment. Critical Issues: Therapeutic approaches to SCLUs can target SCD on the one hand and skin healing and associated aggravating factors on the other. A review of the literature found only case series and six randomized controlled trials; some offered encouraging results, but most had serious biases. Clinical trials specifically targeting SCLUs are difficult to realize because of the small number of affected patients, in comparison with patients with leg ulcers from other causes. Future Direction: Treating SCLUs remains a challenge. Data in the literature are currently insufficient to offer clear treatment guidelines because of several biases in controlled studies. New studies are under way to assess the efficacy of topical treatments and describe the microbiome of SCLUs. Prevention of SCLU recurrence should be assessed in future clinical trials because the high risk of recurrence is an unsolved critical issue.

Lung Surfactant Accelerates Skin Wound Healing: A Translational Study with a Randomized Clinical Phase I Study

Lung surfactants are used for reducing alveolar surface tension in preterm infants to ease breathing. Phospholipid films with surfactant proteins regulate the activity of alveolar macrophages and reduce inflammation. Aberrant skin wound healing is characterized by persistent inflammation. The aim of the study was to investigate if lung surfactant can promote wound healing. Preclinical wound models, e.g. cell scratch assays and full-thickness excisional wounds in mice, and a randomized, phase I clinical trial in healthy human volunteers using a suction blister model were used to study the effect of the commercially available bovine lung surfactant on skin wound repair. Lung surfactant increased migration of keratinocytes in a concentration-dependent manner with no effect on fibroblasts. Significantly reduced expression levels were found for pro-inflammatory and pro-fibrotic genes in murine wounds. Because of these beneficial effects in preclinical experiments, a clinical phase I study was initiated to monitor safety and tolerability of surfactant when applied topically onto human wounds and normal skin. No adverse effects were observed. Subepidermal wounds healed significantly faster with surfactant compared to control. Our study provides lung surfactant as a strong candidate for innovative treatment of chronic skin wounds and as additive for treatment of burn wounds to reduce inflammation and prevent excessive scarring.

A bioengineered living cell construct activates metallothionein/zinc/MMP8 and inhibits TGFβ to stimulate remodeling of fibrotic venous leg ulcers

Venous leg ulcers (VLU) represent a major clinical unmet need, impairing quality of life for millions worldwide. The bioengineered bilayered living cell construct (BLCC) is the only FDA-approved therapy demonstrating efficacy in healing chronic VLU, yet its in vivo mechanisms of action are not well understood. Previously, we reported a BLCC-mediated acute wounding response at the ulcer edge; in this study we elucidated the BLCC-specific effects on the epidermis-free ulcer bed. We conducted a randomized controlled clinical trial (ClinicalTrials.gov NCT01327937) enrolling 30 subjects with nonhealing VLUs, and performed genotyping, genomic profiling, and functional analysis on wound bed biopsies obtained at baseline and 1 week after treatment with BLCC plus compression or compression therapy (control). The VLU bed transcriptome featured processes of chronic inflammation and was strikingly enriched for fibrotic/fibrogenic pathways and gene networks. BLCC application decreased expression of profibrotic TGFß1 gene targets and increased levels of TGFß inhibitor decorin. Surprisingly, BLCC upregulated metallothioneins and fibroblast-derived MMP8 collagenase, and promoted endogenous release of MMP-activating zinc to stimulate antifibrotic remodeling, a novel mechanism of cutaneous wound healing. By activating a remodeling program in the quiescent VLU bed, BLCC application shifts nonhealing to healing phenotype. As VLU bed fibrosis correlates with poor clinical healing, findings from this study identify the chronic VLU as a fibrotic skin disease and are first to support the development and application of antifibrotic therapies as a successful treatment approach.

Collagen Type I: A Versatile Biomaterial

Collagen type I is the most abundant matrix protein in the human body and is highly demanded in tissue engineering, regenerative medicine, and pharmaceutical applications. To meet the uprising demand in biomedical applications, collagen type I has been isolated from mammalians (bovine, porcine, goat and rat) and non-mammalians (fish, amphibian, and sea plant) source using various extraction techniques. Recent advancement enables fabrication of collagen scaffolds in multiple forms such as film, sponge, and hydrogel, with or without other biomaterials. The scaffolds are extensively used to develop tissue substitutes in regenerating or repairing diseased or damaged tissues. The 3D scaffolds are also used to develop in vitro model and as a vehicle for delivering drugs or active compounds.

Immune tolerance of tissue-engineered skin produced with allogeneic or xenogeneic fibroblasts and syngeneic keratinocytes grafted on mice

Organs are needed for the long-term replacement of diseased or wounded tissues. Various technologies based on cells seeded in synthetic or biomaterial scaffolds, or scaffold-free methods have been developed in order to produce substitutes that mimic native organs and tissues. For cell-based approaches, the use of living allogeneic fibroblasts could potentially lead to the production of "off-the-shelf" bioengineered organs/tissues. However, questions remain regarding the outcome of allogeneic grafts in terms of persistence of allogeneic cells, tolerance and the host immune reaction against the tissue after implantation. To evaluate graft tolerance of engineered-tissues containing non-autologous fibroblasts, tissue-engineered skin substitutes (TESs) produced with syngeneic, allogeneic or xenogeneic fibroblasts associated with syngeneic, allogeneic or xenogeneic epithelial cells were grafted in mice as primary and secondary grafts. The immune response was evaluated by histological analysis and immunodetection of M2 macrophages, CD4- and CD8-positive T cells, 15, 19, 35 and 56 days after grafting. Tissue-engineered skin composed of non-autologous epithelial cells were rejected. In contrast, TESs composed of non-autologous fibroblasts underlying syngeneic epithelial cells were still present 56 days after grafting. This work shows that TES composed of non-autologous fibroblasts and autologous epithelial cells are not rejected after grafting. STATEMENT OF SIGNIFICANCE: We found that tissue-engineered skin substitutes produced by a scaffold-free cell-based approach from allogeneic fibroblasts and autologous epithelial cells are not rejected after grafting and allow for the permanent coverage of a full-thickness skin wounds. In the field of tissue engineering, these findings open the possibility of selecting a human fibroblastic or stromal cell population based on its biological properties and adequate biosafety, banking it, in order to produce "ready-to-use" bioengineered organs/tissues that could be grafted to any patient without eliciting immune reaction after grafting. Our results can be generalized to any organs produced from fibroblasts. Thus, it is a great step with multiple applications in tissue engineering and transplantation.

Potential of Allogeneic Adipose-Derived Stem Cell-Hydrogel Complex for Treating Diabetic Foot Ulcers

Mesenchymal stem cells (MSCs) may hold great promise for treating diabetic wounds. However, it is difficult for a clinician to use MSCs because they have not been commercialized. Meanwhile, a new commercial drug that contains adipose-derived stem cells (ASCs) has been developed. The purpose of this study was to examine the potential of allogeneic ASC sheets for treating diabetic foot ulcers. Fifty-nine patients with diabetic foot ulcers were randomized to either the ASC treatment group (n = 30) or a control group treated with polyurethane film (n = 29). Either an allogeneic ASC sheet or polyurethane film was applied on diabetic wounds weekly. These wounds were evaluated for a maximum of 12 weeks. Complete wound closure was achieved for 73% in the treatment group and 47% in the control group at week 8. Complete wound closure was achieved for 82% in the treatment group and 53% in the control group at week 12. The Kaplan-Meier median times to complete closure were 28.5 and 63.0 days for the treatment group and the control group, respectively. There were no serious adverse events related to allogeneic ASC treatment. Thus, allogeneic ASCs might be effective and safe to treat diabetic foot ulcers.

Addressing the Manufacturing Challenges of Cell-Based Therapies

Exciting developments in the cell therapy field over the last decades have led to an increasing number of clinical trials and the first cell products receiving marketing authorization. In spite of substantial progress in the field, manufacturing of cell-based therapies presents multiple challenges that need to be addressed in order to assure the development of safe, efficacious, and cost-effective cell therapies.The manufacturing process of cell-based therapies generally requires tissue collection, cell isolation, culture and expansion (upstream processing), cell harvest, separation and purification (downstream processing), and, finally, product formulation and storage. Each one of these stages presents significant challenges that have been the focus of study over the years, leading to innovative and groundbreaking technological advances, as discussed throughout this chapter.Delivery of cell-based therapies relies on defining product targets while controlling process variable impact on cellular features. Moreover, commercial viability is a critical issue that has had damaging consequences for some therapies. Implementation of cost-effectiveness measures facilitates healthy process development, potentially being able to influence end product pricing.Although cell-based therapies represent a new level in bioprocessing complexity in every manufacturing stage, they also show unprecedented levels of therapeutic potential, already radically changing the landscape of medical care.

Specialized Living Wound Dressing Based on the Self-Assembly Approach of Tissue Engineering

There is a high incidence of failure and recurrence for chronic skin wounds following conventional therapies. To promote healing, the use of skin substitutes containing living cells as wound dressings has been proposed. The aim of this study was to produce a scaffold-free cell-based bilayered tissue-engineered skin substitute (TES) containing living fibroblasts and keratinocytes suitable for use as wound dressing, while considering production time, handling effort during the manufacturing process, and stability of the final product. The self-assembly method, which relies on the ability of mesenchymal cells to secrete and organize connective tissue sheet sustaining keratinocyte growth, was used to produce TESs. Three fibroblast-seeding densities were tested to produce tissue sheets. At day 17, keratinocytes were added onto 1 or 3 (reference method) stacked tissue sheets. Four days later, TESs were subjected either to 4, 10, or 17 days of culture at the air–liquid interface (A/L). All resulting TESs were comparable in terms of their histological aspect, protein expression profile and contractile behavior in vitro. However, signs of extracellular matrix (ECM) digestion that progressed over culture time were noted in TESs produced with only one fibroblast-derived tissue sheet. With lower fibroblast density, the ECM of TESs was almost completely digested after 10 days A/L and lost histological integrity after grafting in athymic mice. Increasing the fibroblast seeding density 5 to 10 times solved this problem. We conclude that the proposed method allows for a 25-day production of a living TES, which retains its histological characteristics in vitro for at least two weeks.

Randomized, Prospective, Blinded-Enrollment, Head-To-Head Venous Leg Ulcer Healing Trial Comparing Living, Bioengineered Skin Graft Substitute (Apligraf) with Living, Cryopreserved, Human Skin Allograft (TheraSkin)

Chronic venous leg ulcers are responsible for significant morbidity and health care costs worldwide. This pilot study evaluated the effectiveness 2 biologically active grafts, TheraSkin and Apligraf, in conjunction with compression therapy. The study, not industry-sponsored, was designed and conducted as a prospective, head-to-head, single-site, randomized clinical trial to assess differences in healing rates, adverse outcomes, and treatment costs. The healing rates were different but not statistically significant, there were no adverse outcomes, and TheraSkin averaged $2495.33 and Apligraf averaged $4316.67 per subject. This suggests that TheraSkin may provide equivalent or superior outcomes to Apligraf while reducing costs.

Dressings and topical agents for treating venous leg ulcers

BACKGROUND

Venous leg ulcers are open skin wounds on the lower leg which can be slow to heal, and are both painful and costly. The point prevalence of open venous leg ulcers in the UK is about 3 cases per 10,000 people, and many people experience recurrent episodes of prolonged ulceration. First-line treatment for venous leg ulcers is compression therapy, but a wide range of dressings and topical treatments are also used. This diversity of treatments makes evidence-based decision-making challenging, and a clear and current overview of all the evidence is required. This review is a network meta-analysis (NMA) which assesses the probability of complete ulcer healing associated with alternative dressings and topical agents.

OBJECTIVES

To assess the effects of (1) dressings and (2) topical agents for healing venous leg ulcers in any care setting and to rank treatments in order of effectiveness, with assessment of uncertainty and evidence quality.

SEARCH METHODS

In March 2017 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also scanned reference lists of relevant included studies as well as reviews, meta-analyses, guidelines and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting. We updated this search in March 2018; as a result several studies are awaiting classification.

SELECTION CRITERIA

We included published or unpublished randomised controlled trials (RCTs) that enrolled adults with venous leg ulcers and compared the effects of at least one of the following interventions with any other intervention in the treatment of venous leg ulcers: any dressing, or any topical agent applied directly to an open venous leg ulcer and left in situ. We excluded from this review dressings attached to external devices such as negative pressure wound therapies, skin grafts, growth factors and other biological agents, larval therapy and treatments such as laser, heat or ultrasound. Studies were required to report complete wound healing to be eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, 'Risk of bias' assessment and data extraction. We conducted this NMA using frequentist meta-regression methods for the efficacy outcome; the probability of complete healing. We assumed that treatment effects were similar within dressings classes (e.g. hydrocolloid, foam). We present estimates of effect with their 95% confidence intervals (CIs) for individual treatments focusing on comparisons with widely used dressing classes, and we report ranking probabilities for each intervention (probability of being the best, second best, etc treatment). We assessed the certainty (quality) of the body of evidence using GRADE for each network comparison and for the network as whole.

MAIN RESULTS

We included 78 RCTs (7014 participants) in this review. Of these, 59 studies (5156 participants, 25 different interventions) were included in the NMA; resulting in 40 direct contrasts which informed 300 mixed-treatment contrasts.The evidence for the network as a whole was of low certainty. This judgement was based on the sparsity of the network leading to imprecision and the general high risk of bias in the included studies. Sensitivity analyses also demonstrated instability in key aspects of the network and results are reported for the extended sensitivity analysis. Evidence for individual contrasts was mainly judged to be low or very low certainty.The uncertainty was perpetuated when the results were considered by ranking the treatments in terms of the probability that they were the most effective for ulcer healing, with many treatments having similar, low, probabilities of being the best treatment. The two most highly-ranked treatments both had more than 50% probability of being the best (sucralfate and silver dressings). However, the data for sucralfate was from one small study, which means that this finding should be interpreted with caution. When exploring the data for silver and sucralfate compared with widely-used dressing classes, there was some evidence that silver dressings may increase the probability of venous leg ulcer healing, compared with nonadherent dressings: RR 2.43, 95% CI 1.58 to 3.74 (moderate-certainty evidence in the context of a low-certainty network). For all other combinations of these five interventions it was unclear whether the intervention increased the probability of healing; in each case this was low- or very low-certainty evidence as a consequence of one or more of imprecision, risk of bias and inconsistency.

AUTHORS' CONCLUSIONS

More research is needed to determine whether particular dressings or topical agents improve the probability of healing of venous leg ulcers. However, the NMA is uninformative regarding which interventions might best be included in a large trial, largely because of the low certainty of the whole network and of individual comparisons.The results of this NMA focus exclusively on complete healing; whilst this is of key importance to people living with venous leg ulcers, clinicians may wish to take into account other patient-important outcomes and factors such as patient preference and cost.

Treatment of Nonhealing Ulcers with an Allograft/Xenograft Substitute: A Case Series

OBJECTIVE:

Wound dressings that use biosynthetic cellulose may be a good alternative to dressings currently used to treat chronic and acute ulcers because their nanostructure is similar to collagen. The objective of this study was to evaluate a wound dressing created with a new material that is composed of a fibrillary network of biosynthetic cellulose.

METHODS:

A case series of 8 patients in primary healthcare centers in Östergötland county council, Sweden, with chronic and acute lower limb wounds were treated with a wound dressing based on eiratex (S2Medical AB, Linköping, Sweden). The dressing was applied to traumatic (n = 5) and venous ulcers (n = 3). All ulcers were considered healed at the end of the treatment.

MAIN OUTCOME MEASURE:

The wounds were examined at regular intervals by a physician to determine healing time, number of dressing changes, and number of visits.

MAIN RESULTS:

Mean healing time was 43 ± 6 days after the first application of the dressing. The mean number of visits was 5.7 ± 0.6, and the mean number of dressings used per patient was 1.7 ± 0.2.

CONCLUSIONS:

These results demonstrate the efficacy of a wound dressing made of eiratex to heal chronic and acute ulcers. The data show that the number of dressings used and dressing changes needed to heal the ulcers are lower than what have been reported in the literature for other dressing materials.

Comparative effectiveness of a bilayered living cellular construct and an acellular fetal bovine collagen dressing in the treatment of venous leg ulcers

Aim: To compare the effectiveness of bilayered living cellular construct (BLCC) and an acellular fetal bovine collagen dressing (FBCD) for the treatment of venous leg ulcers. Methods: Data from WoundExpert^® (Net Health, PA, USA) was used to analyze 1021 refractory venous leg ulcers treated at 177 facilities. Results: Kaplan-Meier analyses showed that BLCC (893 wounds) was superior to FBCD (128 wounds), p = 0.01 for: wound closure by weeks 12 (31 vs 25%), 24 (55 vs 43%) and 36 (68 vs 53%); reduction in time to wound closure of 37%, (19 vs 30 weeks); and improvement in the probability of healing by 45%. Conclusion: BLC versus FBCD showed significant differences in both time to and frequency of healing suggesting that BLCC may provide significant cost savings compared with FBCD.

Apligraf – a Living Human Skin Equivalent for the Treatment of Chronic Wounds

Apligraf, a manufactured living human skin equivalent, was the first true composite tissue analog to become commercially available. It has been approved by the FDA for the treatment of venous leg ulcers and diabetic foot ulcers. The tissue engineered bi-layered skin equivalent has both an epidermis and a dermis, which consist of keratinocytes and fibroblasts derived from neonatal foreskin and bovine collagen. The skin equivalent produces a great number of cytokines and growth factors and is immunologically well tolerated. The product is easy to handle in clinical use and can be applied in an outpatient setting.

Stem Cell Therapy in Wound Healing

Wound healing is a complex restorative process of the altered cutaneous tissue, which is impaired by numerous local and systemic factors, leading to chronic non-healing lesions with few efficient therapeutic options. Stem cells possess the capacity to differentiate into various types of cell lines. Furthermore, stem cells are able to secrete cytokines and growth factors, modulating inflammation and ultimately leading to angiogenesis, fibrogenesis, and epithelization. Because of their paracrine activity, these cells are able to attract other cell types to the base of the wound, improving the formation of new skin layers. Mesenchymal stem cells derived from the adipose tissue, bone marrow, and placenta, offer numerous ways of implementation. The process of harvesting, growing, and administrating stem cells depends on the site and type of the cells, but recent trial results showed improvement of wound healing independent of the administration site. Bioengineered skin substitutes are validated for treatment of chronic wounds with direct application on the skin surface. These offer physical scaffolding for the migrating cells and promote secretion of growth factors, thus facilitating rapid wound healing. Obtaining further clinical data is essential, but stem cell therapy may become a first-line therapeutic choice for the treatment of non-healing chronic wounds.

Comparative Effectiveness of a Bioengineered Living Cellular Construct and Cryopreserved Cadaveric Skin Allograft for the Treatment of Venous Leg Ulcers in a Real-World Setting

Objective: A variety of advanced biological therapies are available for the treatment of chronic wounds such as venous leg ulcers (VLUs), but real-world comparative effectiveness data that can help guide decisions around treatments are currently lacking. Approach: This analysis was designed to compare the effectiveness of a bioengineered living cellular construct (BLCC) to a cryopreserved cadaveric skin allograft (CCSA) for the treatment of VLUs. Treatment records were collected from a large wound care-specific electronic medical record database on 717 patients (799 VLUs) receiving treatment at 177 wound care centers. Ulcers ≥28 days duration, between ≥1 and < 40 cm2 that closed ≤40% within the 28 days before treatment were included. Results: Patient baseline demographics and wound characteristics were comparable between groups. The median time to wound closure was 52% faster with BLCC compared with CCSA (15 weeks vs. 31 weeks). In addition, the proportion of wounds healed were significantly higher for BLCC by 12 weeks (42% vs. 24%) and 24 weeks (65% vs. 41%) (p = 0.0002). Treatment with BLCC increased the probability of healing by 97% compared with CCSA (hazard ratio = 1.97 [95% confidence interval 1.39-2.79], p = 0.0002). Innovation: This is the first real-world comparative effectiveness analysis to evaluate BLCC and CCSA for the treatment of VLUs. Conclusion: Treatment with a bioengineered cellular technology significantly improved the incidence and speed of wound closure compared with a CCSA.

A bioengineered living cell construct activates an acute wound healing response in venous leg ulcers

Chronic nonhealing venous leg ulcers (VLUs) are widespread and debilitating, with high morbidity and associated costs; about $15 billion is spent annually on the care of VLUs in the United States. Despite this, there is a paucity of treatments for VLUs because of the lack of pathophysiologic insight into ulcer development as well as the lack of knowledge regarding biologic actions of existing VLU-targeted therapies. The bioengineered bilayered living cellular construct (BLCC) skin substitute is a U.S. Food and Drug Administration-approved biologic treatment for healing VLUs. To elucidate the mechanisms through which the BLCC promotes healing of chronic VLUs, we conducted a clinical trial (NCT01327937) in which patients with nonhealing VLUs were treated with either standard of care (compression therapy) or the BLCC together with standard of care. Tissue was collected from the VLU edge before and 1 week after treatment, and the samples underwent comprehensive microarray mRNA and protein analyses. Ulcers treated with the BLCC skin substitute displayed three distinct transcriptomic patterns, suggesting that BLCC induced a shift from a nonhealing to a healing tissue response, involving modulation of inflammatory and growth factor signaling, keratinocyte activation, and attenuation of Wnt/β-catenin signaling. In these ways, BLCC application orchestrated a shift from the chronic nonhealing ulcer microenvironment to a distinctive healing milieu resembling that of an acute, healing wound. Our findings provide in vivo evidence in VLU patients of pathways that can be targeted in the design of new therapies to promote healing of chronic VLUs.

Tissue Engineered Skin Substitutes

The fundamental skin role is to supply a supportive barrier to protect body against harmful agents and injuries. Three layers of skin including epidermis, dermis and hypodermis form a sophisticated tissue composed of extracellular matrix (ECM) mainly made of collagens and glycosaminoglycans (GAGs) as a scaffold, different cell types such as keratinocytes, fibroblasts and functional cells embedded in the ECM. When the skin is injured, depends on its severity, the majority of mentioned components are recruited to wound regeneration. Additionally, different growth factors like fibroblast growth factor (FGF), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF) are needed to orchestrated wound healing process. In case of large surface area wounds, natural wound repair seems inefficient. Inspired by nature, scientists in tissue engineering field attempt to engineered constructs mimicking natural healing process to promote skin restoration in untreatable injuries. There are three main types of commercially available engineered skin substitutes including epidermal, dermal, and dermoepidermal. Each of them could be composed of scaffold, desired cell types or growth factors. These substitutes could have autologous, allogeneic, or xenogeneic origin. Moreover, they may be cellular or acellular. They are used to accelerate wound healing and recover normal skin functions with pain relief. Although there are a wide variety of commercially available skin substitutes, almost none of them considered as an ideal equivalents required for proper wound healing.

Immunological challenges associated with artificial skin grafts: available solutions and stem cells in future design of synthetic skin

The repair or replacement of damaged skins is still an important, challenging public health problem. Immune acceptance and long-term survival of skin grafts represent the major problem to overcome in grafting given that in most situations autografts cannot be used. The emergence of artificial skin substitutes provides alternative treatment with the capacity to reduce the dependency on the increasing demand of cadaver skin grafts. Over the years, considerable research efforts have focused on strategies for skin repair or permanent skin graft transplantations. Available skin substitutes include pre- or post-transplantation treatments of donor cells, stem cell-based therapies, and skin equivalents composed of bio-engineered acellular or cellular skin substitutes. However, skin substitutes are still prone to immunological rejection, and as such, there is currently no skin substitute available to overcome this phenomenon. This review focuses on the mechanisms of skin rejection and tolerance induction and outlines in detail current available strategies and alternatives that may allow achieving full-thickness skin replacement and repair.