Porcine dermal collagen as a wound dressing for skin donor sites and deep partial skin thickness burns

Effect of natural polymer materials on skin healing based on internal wound microenvironment: a review

The concept of wound microenvironment has been discussed for a long time. However, the mechanism of the internal microenvironment is relatively little studied. Here, we present a systematic discussion on the mechanism of natural polymer materials such as chitosan, cellulose, collagen and hyaluronic acid through their effects on the internal wound microenvironment and regulation of wound healing, in order to more comprehensively explain the concept of wound microenvironment and provide a reference for further innovative clinical for the preparation and application of wound healing agents.

Hyperbaric and topical oxygen therapies in thermal burn wound healing: a review

OBJECTIVE

This review aims to evaluate the effectiveness of the two most commonly used oxygen delivery methods for the treatment of thermal burn wound healing: hyperbaric oxygen therapy (HBOT) and topical oxygen therapy (TOT).

METHOD

The PubMed database was searched for articles discussing the use of HBOT or TOT in the treatment of thermal burns.

RESULTS

The search yielded 43,406 articles, of which 28 (23 HBOT, 5 TOT) met the inclusion criteria. Both experimental and clinical studies have demonstrated conflicting results after treating thermal burns with HBOT or TOT. Overall, 14/23 studies demonstrated positive results for HBOT on the healing of burn wounds and associated complications, such as oedema and pain. Findings from these studies showed it can reduce morbidity and mortality in certain high-risk groups such as those with diabetes or extensive burns. Although the five studies (one human and four animal trials) reviewing TOT showed promising outcomes, this therapeutic modality has not been well investigated.

CONCLUSION

Therapeutic use of HBOT in thermal burns has been popular in the past but its use remains controversial due to inconsistent results, serious side-effects, lack of convenience and high costs. The use of TOT in the management of burns needs further exploration by scientists and clinicians alike, in addition to the implementation of a standardised treatment protocol.

Application expansion of small intestinal submucosa extracellular matrix in complex and surgical wounds

A wound is hard-to-heal or complex when the defect fails to progress through the normal stages of wound healing in a timely fashion. Hard-to-heal wounds such as diabetic foot or venous leg ulcers can be long-lasting conditions. Alternatively, complex acute wounds that occur from trauma, burns, postoperative, necrosis and some dermatological diseases can also result in hard-to-heal wounds. This article reviews important considerations in the management of complex acute wounds, such as time to wound closure, pain, scarring, patient satisfaction and identification of options that can promote healing of grafts and flaps, while reducing donor-site morbidity. Primary research has demonstrated the inherent benefits of small intestinal submucosa extracellular matrix (SIS-ECM), a naturally occurring porcine matrix that promotes development of dermis-like tissue in both complex acute and hard-to-heal wounds. Presently, the literature provides mostly case studies demonstrating the benefits of SIS-ECM in the management of complex acute wounds. The available case series suggest emerging clinical benefits including rapid time to coverage, avoidance of donor-site complications and development of granulation tissue in locations of low circulation, which improves poor graft sites, potentially reducing dehiscence and providing support for reconstruction flaps and grafts.

Collagen membranes for skin wound repair: A systematic review

Membranes or skin dressing are common treatments for skin wound injuries, collagen being one the most effective materials for their manufacturing. Many different sources of collagen with diverse methods of extraction and processing have been used, with evidence of positive effects on the stimulation of skin wound healing. In spite of these factors, there is still limited understanding of the interaction between collagen membranes and biological tissues, especially due to the series of different types of collagen origin. In this context, this study aimed to conduct a systematic review of the available literature examining the effect of various collagen membranes for accelerating skin wound healing in experimental animal models and clinical trials. The present review was performed from March to May of 2020 searching in two databases (PubMed and Scopus). The following Medical Subject Headings (MeSH) descriptors were used: "collagen", "dressing", "membranes", "skin" and "wound". After the eligibility assessment, 16 studies were included and analyzed. The studies demonstrated that collagen was obtained predominantly from bovine and porcine sources, by acetic acid and/or enzyme dissolution. Additionally, most of the studies demonstrated that the membranes were processed mainly by freeze-drying or lyophilization methods. All the in vivo and clinical trial studies evidenced positive outcomes in the wound healing process, thus confirming that collagen membranes are one of the most efficient treatment for skin wounds, highlighting the enormous potential of this biomaterial to be used for skin tissue engineering purposes.

In Vitro Feasibility Analysis of a New Sutureless Wound-Closure System Based on a Temperature-Regulated Laser and a Transparent Collagen Membrane for Laser Tissue Soldering (LTS)

For the post-surgical treatment of oral wounds and mucosal defects beyond a certain size, the gold standard is still an autologous skin or mucosal graft in combination with complex suturing techniques. A variety of techniques and biomaterials has been developed for sutureless wound closure including different tissue glues or collagen patches. However, no wound covering that enables for sutureless fixation has yet been introduced. Thus, a new system was developed that allows for sutureless wound covering including a transparent collagen membrane, which can be attached to the mucosa using a specially modified 2λ laser beam with integrated temperature sensors and serum albumin as bio-adhesive. The sutureless wound closure system was tested for its applicability and its cytocompatibility by an established in vitro model in the present study. The feasibility of the laser system was tested ex vivo on a porcine palate. The in vitro cytocompatibility tests excluded the potential release of toxic substances from the laser-irradiated collagen membrane and the bio-adhesive. The results of the ex vivo feasibility study using a porcine palate revealed satisfactory mean tensile strength of 1.2–1.5 N for the bonding of the membrane to the tissue fixed with laser of 980 nm. The results suggest that our newly developed laser-assisted wound closure system is a feasible approach and could be a first step on the way towards a laser based sutureless clinical application in tissue repair and oral surgery.

Morphological Evaluation of Soft Tissue Augmentation Using Porous Poly-DL-Lactic Acid With Straight Holes

OBJECTIVES

This study investigated the biological reaction to porous poly-DL-lactic acid (PDLLA) scaffolds with holes for soft tissue augmentation.

MATERIALS AND METHODS

The control group was porous PDLLA with a diameter of 5.0 mm and a height of 2.0 mm. For the 2 test groups, 7 holes were drilled from the upper to the lower base of the scaffolds; the holes had diameters of 0.5 and 1.0 mm. A scaffold was placed in the periosteum of the cranium. The height and molecular weight (Mw) of the scaffolds were measured at 4 and 8 weeks. Hematoxylin and eosin staining was used to measure the connective tissue and blood vessel areas.

RESULTS

All groups had similar scaffold heights, but the Mw decreased significantly over time. There were significant differences in the connective tissue and blood vessel areas among the control, 0.5-mm, and 1.0-mm groups at the same time point. The soft tissue was increased by drilling holes in the scaffolds.

CONCLUSION

Porous poly-DL-lactic acid (PDLLA) contributed favorable prognosis for soft tissue. A wider hole was associated with increased connective tissue and blood vessel areas. The scaffold height and Mw were not impacted by size of the holes.

In vitro engineering of a palatal mucosa equivalent with acellular porcine dermal matrix

The objective of this study was to develop a palatal mucosa equivalent composed of multilayered oral keratinocytes grown on the acellular porcine dermal matrix. Acellular porcine dermal matrix was prepared through a series of procedures and assessed by histological, immunohistochemical, and scanning electron microscopy examination. The palatal mucosa equivalent was fabricated by seeding oral keratinocytes, which cultured from human palate mucosa, onto the acellular dermal matrix. After 4 days submerged in medium, this composite was raised to the air-liquid interface for another 7 or 14 days of cultivation. The results demonstrated the processed porcine dermal matrix was totally cell-free. The resultant palatal mucosa equivalent showed a multilayered oral epithelium that had been formed, and the number of cell layers was correlated with the culture period at the air-liquid interface. Oral keratinocytes infiltrated into the empty hair follicles of the acellular porcine dermal matrix and formed an anchor-like structure, which exhibited resemblance to the rete ridges of the native palate mucosa. Immunohistochemical staining for CK10/13, CK19, Ki-67 nuclear antigen, and Heparan sulphate indicated the cultured palatal mucosa equivalent shared the same characteristics with that of the native palate mucosa. In conclusion, our fabricated palatal mucosa equivalent exhibited the characteristics of the native counterpart, and this equivalent might be useful for recovery of the wounds in the palate secondary to palatoplasty.

Extracellular matrix as a strategy for treating chronic wounds

The dermis normally directs all phases of skin wound healing following tissue trauma or disease. However, in chronic wounds, the dermal matrix is insufficient to stimulate healing and assistance by external factors is needed for wound closure. Although the concept of the extracellular matrix directing wound healing is not new, ideas about how best to provide the extracellular matrix components required to 'jump-start' the healing process are still evolving. Historically, these strategies have included use of enzyme-inhibiting dressing materials, which bind matrix metalloproteinases and remove them from the chronic wound environment, or direct application of purified growth factors to stimulate fibroblast activity and deposition of neo-matrix. More recently, the application of a structurally intact, biochemically complex extracellular matrix, designed to provide the critical extracellular components of the dermis in a single application, has allowed for the reconstruction of new, healthy tissue and restoration of tissue integrity in the previously chronic wound. This review focuses on this third mechanism as an emerging tactic in effective wound repair. Intact extracellular matrix can quickly, easily, and effectively provide key extracellular components of the dermis necessary to direct the healing response and allow for the proliferation of new, healthy tissue. Its application may promote the healing of wounds that have been refractory to other, more conventional treatment strategies, and may eventually show utility when used earlier in wound healing treatment with the goal of preventing wounds from reaching a truly chronic, nonresponsive state.

Comparing the Vancouver Scar Scale With the Cutometer in the Assessment of Donor Site Wounds Treated With Various Dressings in a Randomized Trial

Cutaneous scarring observed in wounds is, to a significant degree, dependent upon the time it takes for the wounds to heal. Various topical dressings are proposed to influence healing time in donor sites. In this prospective randomized study, we examined the effect of Vaseline gauze (VD; Branolind, Paul Hartmann AG, Germany), Biobrane (BD; Bertek Pharmaceuticals, Inc., Morgantown, WV), an occlusive film dressing Barrier Flex (OD; Moelnlycke Health Care GmbH, Germany), and an equine collagen foil, Tissu Foil E (CD; Baxter, Heidelberg, Germany), on re-epithelialization and scarring in standardized donor site wounds. At 6 months after surgery, donor site scars and normal uninjured mirror sided skin were evaluated in 33 patients using both the Vancouver Scar Scale (VSS) and the cutometer SEM 575 (Courage and Khazaka). The median healing time for OD was 14 days, BD 16 days, CD 19 days, and VD 19 days. The single parameter pliability of the VSS was not significantly different from uninjured skin when all donor site scars were pooled. No difference was found between the four groups. Viscoelastic analysis of all pooled patient data showed a significant difference for Uf (total deformation), Ua (total recovery), Ur (immediate retraction), Ue (immediate distension), Ur/Ue, and Ur/Uf, indicating that donor sites significantly differed from normal uninjured skin. No significant correlation between objective viscoelastic measurements and the subjective pliability assessment of the VSS was found. Viscoelastic differences were greatest in the VD and BD groups. Viscolelastic differences did not significantly correlate with healing time. Various wound dressings had minimal yet significant influence on healing time and scarring. In contrast to the VSS, viscoelastic measurements of skin pliability can objectify scarring when few differences are anticipated.

A Comparison of Human and Porcine Acellularized Dermis: Interactions with Human Fibroblasts In Vitro

BACKGROUND

Dermal substitutes derived from xenograft materials require elaborate processing at a considerable cost. Acellularized porcine dermis is a readily available material associated with minimal immunogenicity. The objective of this study was to evaluate acellularized pig dermis as a scaffold for human fibroblasts.

METHODS

In vitro methods were used to evaluate fibroblast adherence, proliferation, and migration on pig acellularized dermal matrix. Acellular human dermis was used as a control.

RESULTS

Pig acellularized dermal matrix was found to be inferior to human acellularized dermal matrix as a scaffold for human fibroblasts. Significantly more samples of human acellularized dermal matrix (83 percent, n = 24; p < 0.05) demonstrated fibroblast infiltration below the cell-seeded surface than pig acellularized dermal matrix (31 percent, n = 49). Significantly more (p < 0.05) fibroblasts infiltrated below the surface of human acellularized dermal matrix (mean, 1072 +/- 80 cells per section; n = 16 samples) than pig acellularized dermal matrix (mean, 301 +/- 48 cells per section; n = 16 samples). Fibroblasts migrated significantly less (p < 0.05) distance from the cell-seeded pig acellularized dermal matrix surface than in the human acellularized dermal matrix (78.8 percent versus 38.3 percent cells within 150 mum from the surface, respectively; n = 5). Fibroblasts proliferated more rapidly (p < 0.05) on pig acellularized dermal matrix (n = 9) than on the human acellularized dermal matrix (7.4-fold increase in cell number versus 1.8-fold increase, respectively; n = 9 for human acellularized dermal matrix). There was no difference between the two materials with respect to fibroblast adherence (8120 versus 7436 average adherent cells per section, for pig and human acellularized dermal matrix, respectively; n = 20 in each group; p > 0.05).

CONCLUSION

Preliminary findings suggest that substantial differences may exist between human fibroblast behavior in cell-matrix interactions of porcine and human acellularized dermis.

Randomized Clinical Trial Comparing OASIS Wound Matrix to Regranex Gel for Diabetic Ulcers

OBJECTIVE

To compare healing rates at 12 weeks for full-thickness diabetic foot ulcers treated with OASIS Wound Matrix, an acellular wound care product, versus Regranex Gel.

DESIGN

Randomized, prospective, controlled multicenter trial at 9 outpatient wound care clinics.

SUBJECTS

A total of 73 patients with at least 1 diabetic foot ulcer were entered into the trial and completed the protocol.

INTERVENTION

Patients were randomized to receive either OASIS Wound Matrix (n = 37) or Regranex Gel (n = 36) and a secondary dressing. Wounds were cleansed and debrided, if needed, at a weekly clinic visit. Dressings were changed as needed. The maximum treatment period for each patient was 12 weeks.

PRIMARY OUTCOME MEASURE

Incidence of healing in each group at 12 weeks.

RESULTS

After 12 weeks of treatment, 18 (49%) OASIS-treated patients had complete wound closure compared with 10 (28%) Regranex-treated patients.

CONCLUSION

Although the sample size was not large enough to demonstrate that the incidence of healing in the OASIS group was statistically superior (P = .055), the study results showed that treatment with OASIS is as effective as Regranex in healing full-thickness diabetic foot ulcers by 12 weeks.

An investigation of the long-term bioactivity of endogenous growth factor in OASIS Wound Matrix

OBJECTIVE

To examine the retention and bioactivity of endogenous FGF-2 after prolonged storage within a complex matrix. FGF-2 is a growth factor found in OASIS Wound Matrix, a purified collagen wound-care product containing other endogenous components of the extracellular matrix.

METHOD

FGF-2 content was measured by ELISA. FGF-2 activity was measured using an in vitro bioassay in rat pheochromocytoma (PC12) cells.

RESULTS

FGF-2 content ranged from 15.3 ng/g to 84.3 ng/g. The bioassay showed that the FGF-2 retained in the matrix was present in a bioactive form able to cause differentiation of cells in culture.

CONCLUSION

The results demonstrate that wound-care products can be developed to retain their bioactivity over time and that inherently unstable purified growth factors are preserved if stored as bound factors within their natural extracellular matrix. The results also suggest that use of acellular matrices containing active growth factors would have advantages in terms of simplicity and cost over purified recombinant growth factor therapies.

Use of porcine renal capsule matrix as a full-thickness dermal wound-healing material in rats

OBJECTIVE

To compare the utility of porcine renal capsule matrix (RCM) with porcine small intestinal mucosa (SIS) in a rat full-thickness skin wound model.

METHOD

Groups of rats had surgically-created wounds filled with either SIS or RCM. On each rat a contralateral wound was left unfilled (RCM-U or SIS-U). Wound diameter was measured 3, 7, 12, 17, 26 and 30 days after creation. Wound sites sampled 3, 7, 14, 28, 42 and 56 days after wound creation were numerically graded for degree of histologic change and for collagen content, based on intensity of trichrome staining.

RESULTS

Wounds in all groups rapidly contracted to less than 50% of the original diameter within 12 days. There were no differences in wound diameter between RCM- and SIS-treated wounds at any time point, but these wounds had significantly greater (p < 0.001) diameters than their unfilled counterparts on days 7, 12 and 17. There were no differences in histologic scores or trichrome-staining scores between RCM- and SIS-treated wounds and their unfilled counterparts at any time point, except for a greater (p < 0.05) histologic score in SIS-treated wounds compared with unfilled controls on day 14. In both treatment groups an acute inflammatory response at the wound site was soon replaced by an influx of macrophages and fibroblasts.

CONCLUSION

The results show that RCM is equivalent to SIS for the treatment of full-thickness wounds and that these materials may enhance wound healing in terms of wound-tissue collagenisation and maturation. These materials therefore merit further study in other wound-care models.

Adhesive retention dressings are more comfortable than alginate dressings on split-skin-graft donor sites

Painful split-skin-graft donor sites remain a common problem for patients. We undertook a prospective randomised trial to examine the comparative comfort and ease of care of two different donor-site dressings. One dressing is the alginate Kaltostat, the standard plastic-surgical dressing in the UK and abroad, and the other is the adhesive retention tape Mefix, a novel use of a readily available dressing. We randomised 50 patients requiring split-skin grafts to receive either alginate (Kaltostat) or retention (Mefix) donor-site dressings. Dressings were assessed by interview and questionnaire at 24, 72 h and 2 weeks, and by wound review at 2 weeks. Retention dressings were found to be more comfortable, required less nursing intervention and allowed patients easier mobility with a greater range of daily activities, especially washing, without compromising wound healing. We recommend adhesive retention dressings as cost-effective comfortable dressings, which readily conform to any donor site.

A study to evaluate primary dressings for the application of cultured keratinocytes

Despite the recent improvements in cell culture and dermal regeneration methods, tissue engineering of skin has yet to receive widespread acceptance in the management of burn injuries. The reasons for this are complex and include not only the inherent costs of (particularly) setting up and running such a system but also the continuing difficulties in achieving successful engraftment of the neoepidermis. The latter has previously been addressed in a number of ways, including improving the recipient bed and using pre-confluent delivery systems to allow earlier application of cells to that wound bed. One area that has received little attention is that of the optimal wound dressing to use with this technology; the cells are very poorly attached at early time points, and, in this context, the traditional dressing of paraffin gauze has never been formally assessed in comparison with newer materials. Using a porcine acute wound chamber model, we performed a prospective randomised trial to assess four different wound dressings with reference to the amount of epidermal cover gained and the histological quality of the regenerated skin after 3 weeks. Out of the four materials tested, polyurethane foam (Allevyn) was superior histologically (although equal in take rate with paraffin gauze), whilst polythene sheet (Opsite) and silicone sheet were substantially inferior. We conclude that the traditional dressing used with this technology should be compared with polyurethane foam in a clinical trial. In the future, novel dressings should be formally tested against traditional methods before being adopted.

Successful treatment of a patient with 100% total burn surface area at high altitude

A patient with 100% total burn surface area has been treated in our department which is situated at 2261 meters above sea level in July 1993. This paper reports the treatment experience.

Frozen human epidermal allogeneic cultures promote rapid healing of facial dermabrasion wounds

BACKGROUND

Clinical studies have shown that cultured human epidermal allogenic sheets promote faster reepithelization of skin donor sites and deep partial-thickness wounds.

OBJECTIVE

We describe the results of a controlled, clinical study of facial dermabrasion sites treated with a single application of frozen cultured human allogenic epidermal sheets that were thawed for 5-10 minutes at room temperature before application.

METHODS

Ten patients with scars from acne or of other etiology underwent facial dermabrasion. One side of the face was treated with the frozen and thawed cultures, the other side was treated with standard dry dressing.

RESULTS

The epidermal cultures promoted faster reepithelization of the wounds, with complete reepithelization in an average time of 4.6 days, whereas controls healed in an average of 7. 9 days. The reduction in healing time was 42% (P = 4.82 x 10(-7)). Pain was reduced in sites treated with the thawed cultures.

CONCLUSION

Epidermal allogenic cultures, preserved by freezing, promoted significantly faster reepithelization and reduced pain intensity of dermabraded facial wounds, suggesting that they could be used routinely to improve the recovery from dermabrasion.

Comparison of the effect of a collagen dressing and a polyurethane dressing on the healing of split thickness skin graft (STSG) donor sites

Recent advances in the resurfacing of burn wounds with dermal equivalents and collagen preparations have shown the efficacy of collagen. To investigate the benefits (if any), standardised split skin donor areas were chosen to compare the influence of collagen on re-epithelialisation. A bovine collagen preparation consisting of type-I collagen was prospectively compared with polyurethane film dressing in a study of 20 split thickness skin graft donor sites. The rates of epithelialisation, the discomfort experienced by the patients and the convenience of the dressings were assessed. The median time from operation to the observation of complete healing was 7.5 (+/- 2.5) days for the donor sites dressed with the collagen membrane and 12.5 (+/- 3.4) days for the the donor areas dressed with a polyurethane film (p < 0.001). The discomfort experienced by the two groups of patients was significantly less after wound coverage with collagen (p < 0.005). Haematomas or seromas that required repeated aspiration was seen under the polyurethane film dressing. The collagen dressing was more expensive than the polyurethane film, but improved wound healing compared with the polyurethane dressings.