The effects of biological wound dressings on the healing process

Photo-crosslinked adhesive hydrogel loaded with extracellular vesicles promoting hemostasis and liver regeneration

Hepatectomy is an effective surgical method for the treatment of liver diseases, but intraoperative bleeding and postoperative liver function recovery are still key issues. This study aims to develop a composite hydrogel dressing with excellent hemostatic properties, biocompatibility, and ability to promote liver cell regeneration. The modified gelatin matrix (GelMA, 10%) was mixed with equal volumes of sodium alginate-dopamine (Alg-DA) at concentrations of 0.5%, 1%, and 2%. Then a cross-linking agent (0.1%) was added to prepare different composite hydrogels under UV light, named GelMA/Alg-DA-0.5, GelMA/Alg-DA-1 and GelMA/Alg-DA-2, respectively. All the prepared hydrogel has a porous structure with a porosity greater than 65%, and could be stabilized in a gel state after being cross-linked by ultraviolet light. Physicochemical characterization showed that the elastic modulus, water absorption, adhesion, and compressibility of the composite hydrogels were improved with increasing Alg-DA content. Furthermore, the prepared hydrogel exhibits in vitro degradability, excellent biocompatibility, and good hemostatic function. Among all tested groups, the group of GelMA/Alg-DA-1 hydrogel performed the best. To further enhance its application potential in the field of liver regeneration, adipose-derived mesenchymal stem cell exosomes (AD-MSC-Exo) were loaded into GelMA/Alg-DA-1 hydrogel. Under the same conditions, GelMA/Alg-DA-1/Exo promoted cell proliferation and migration more effectively than hydrogels without extracellular vesicles. In conclusion, the prepared GelMA/Alg-DA-1 composite hydrogel loaded with AD-MSC-Exo has great application potential in liver wound hemostasis and liver regeneration.

Human skin processing affects clinical outcome in allograft recipients

Skin allografts represent a milestone in burn patient treatment. However, skin procurement is still burdened by high rates of contamination, and validation procedures have not yet been standardized. In addition, it is not clear if tissue viability affects allograft skin outcomes. In 2120 skin samples from 610 donors, a retrospective analysis was performed to identify donor and procurement variables associated with bacterial contamination and tissue viability. Post-processing contamination was associated significantly with the donor type, cause of death, length of hospitalization, procurement site, surgeon, interval between procurement and banking, and decontamination method. Tissue viability appeared to be negatively associated with freezing. In two series of skin allograft recipients (155 and 195 patients), we evaluated the role of skin characteristics and procurement variables on clinical outcomes. We found that the length of hospitalization was associated significantly with donor age. Procalcitonin and PCR values in allograft recipients were correlated with the decontamination method. No significant associations were observed between tissue viability and clinical outcomes (length of hospitalization, cause of donor death, or inflammatory parameters) after allograft transplantation. In these large case series, we identified donor and procurement variables that may affect allograft skin recipients. The decontamination method appeared to be a critical step for skin allograft requiring better standardization.

Evaluation of fish skin as a biological dressing for metacarpal wounds in donkeys

Background

The use of biological dressings has recently emerged in the management of burns and wounds. The aim of the present study was to evaluate the Nile tilapia skin as a biological dressing for full-thickness cutaneous metacarpal wounds in donkeys. The study was conducted on nine clinically healthy donkeys (n = 9). Here, fish skin dressings were obtained from fresh Nile tilapia (Oreochromis niloticus and sterilized by immersion in silver nanoparticles (AgNPs) solution for 5 min, with no change in collagen content. Bilateral, circular full-thickness excisional skin wounds (2 cm in diameter) were created on the dorsal aspect of the mid-metacarpals of each donkey. Wounds on the right metacarpals (treated wounds, n = 9) were dressed with sterile fish skins, while wounds on the left metacarpals (control wounds, n = 9) were dressed with sterile non-adherent dressing pads without any topical applications. Wound dressings were changed weekly. Wounds were evaluated microbiologically, grossly, and histologically on days 7, 14, and 21 post-wound inductions.

Results

Fish skin-dressed wounds showed a significant (P < 0.0001) reduction in microbial counts (Total viable bacterial count, Staphylococcal count, and Coliform count), a significant (P < 0.0001) decrease in the wound size, and a significant reduction (P < 0.0001) in the epithelial gap compared to the untreated wounds. No frequent dressing changes were needed.

Conclusions

Fish skin dressing accelerated the wound healing process and efficiently inhibited the local microbial activity and exuberant granulation tissue formation suggesting its reliable and promising application for metacarpal wounds of donkeys.

Evolution of Biological Bandages as First Cover for Burn Patients

Significance: Cutaneous wound regeneration is vital to keep skin functions and for large wounds, to maintain human survival. In a deep burn, the ability of the skin to heal is compromised due to the damage of vasculature and resident cells, hindering a coordinated response in the regeneration process. Temporal skin substitutes used as first cover can play a major role in skin regeneration as they allow a rapid wound covering that, in turn, can significantly reduce infection risk, rate of secondary corrective surgeries, and indirectly hospitalization time and costs. Recent Advances: Skin was one of the first tissues to be bioengineered providing thus a skin equivalent; however, what is the current status subsequent to 40 years of tissue engineering? We review the classic paradigms of biological skin substitutes used as first cover and evaluate recent discoveries and clinical approaches adapted for burn injuries cover, with an emphasis on innovative cell-based approaches. Critical Issues: Cell-based first covers offer promising perspectives as they can have an active function in wound healing, such as faster healing minimizing scar formation and prepared wound bed for subsequent grafting. However, cell-based therapies encounter some limitations due to regulatory hurdles, as they are considered as "Advanced Therapy Medicinal Products," which imposes the same industry-destined good manufacturing practices as for pharmaceutical products and biological drug development. Future Directions: Further improvements in clinical outcome can be expected principally with the use of cell-based therapies; however, hospital exemptions are necessary to assure accessibility to the patient and safety without hindering advances in therapies.

Amnion: The Ideal Scaffold for Treating Full-Thickness Wounds of the Lower Extremity

Amnion and amniotic tissue has been studied for more than 100 years in the treatment of acute and chronic wounds. Recent studies have focused on the use of amnion tissue in the management of full-thickness diabetic wounds, particularly of the lower extremities. With new harvesting, processing, and distribution technologies, amnion is increasingly available in treating these wounds. Current data and research show increased healing potential and decreased healing times, pain, drainage, and infection in wounds treated with amnion products. There are a variety of amnion products with varying differences and purposes, requiring additional research and comparison trials.

Dermis fat graft for pediatric exenteration-challenging but rewarding

Orbital exenteration is a destructive and disfiguring surgery and involves removal of the entire orbital contents, soft tissue and often lids as well. We report a case of an eight month old female, with malignant orbital teratoma who underwent lid sparing exenteration for the destructive, locally advanced disease. Three month post surgery she developed recurrence with intracranial extension as well as socket infection with pus discharge. Repeat surgery involved a multispeciality approach for removal of the tumor which was abutting the cavernous sinus posteriorly and ethmoid sinus medially, apart from filling the entire bony orbit. The focus of infection was found to be the retained lacrimal sac. The unhealthy lid skin also had to be sacrificed. The challenges in repeat exenteration of an 8 month old, and the utility of autologous dermis fat graft as a reconstructive option are discussed.

Application of hyperdry amniotic membrane patches without fibrin glue over the bony surface of mastoid cavities in canal wall down tympanoplasty

CONCLUSION

Fibrin glue might be an inessential bioadhesive for attachment of hyperdry amniotic membrane (AM) patches in canal wall down (CWD) tympanoplasty.

OBJECTIVE

To clarify the pliability and adherence capability of human hyperdry AM, the feasibility of fixing hyperdry AM without fibrin glue to the bony surface of the mastoid cavity was evaluated in CWD tympanoplasty.

METHODS

This was a retrospective chart review. In seven ears of seven patients, the AM was simply attached over the bony surface of the mastoid cavity without fibrin glue (AMG(-) group). In 22 ears of 20 other patients, hyperdry AM (11 ears of 11 patients, AMG(+) group) or temporal fascia (11 ears of 9 patients, TFG(+) group) was attached over the bony surface of the mastoid cavity with fibrin glue. Times for graft epithelization were compared among the three groups.

RESULTS

Complete epithelization of the mastoid cavity took place in all patients in all three groups. The mean time to complete epithelization of the graft in the AMG(-) and AMG(+) groups was significantly faster than that in the TFG(+) group (p < 0.05) and was not significantly different between the two AM groups (p > 0.05).

Effect of hyperdry amniotic membrane patches attached over the bony surface of mastoid cavities in canal wall down tympanoplasty

OBJECTIVES

To overcome the lack of the autografts in revision ear surgery, the usefulness of human amniotic membrane (AM) patches as a dressing substitute for fascia grafts of the temporal muscle (temporalis fascia graft) was investigated in canal wall down tympanoplasty.

STUDY DESIGN

Retrospective chart review.

METHODS

In 11 ears of 11 patients, the AM was attached over the bony surface of the mastoid cavity (AM group). In 11 ears of nine patients, the temporalis fascia graft was attached over the bony surface of the mastoid cavity (fascia group). The times for graft epithelization were compared in both groups.

RESULTS

In both groups, complete epithelization of the mastoid cavity took place in all patients. The time of epithelization in the AM group was 32 days, whereas in the fascia group it was 45 days. Complete epithelization of the AM graft was significantly faster than the fascia graft (P < .05).

CONCLUSIONS

Hyperdry AM might be a new useful dressing substitute for temporalis fascia graft due to the reduction in the epithlializing time offered by the AM in revision ear surgery.

Cultured epithelial autografts for coverage of large burn wounds in eighty-eight patients: the Indiana University experience

Since 1990, the authors have used a new technique for coverage of large burns, which begins with early tangential excision and coverage with cadaver allograft (A), followed by placement of cultured epithelial autograft (CEA) onto an allodermis base (CEA/A). They present their 18-year experience (1990-present) using CEA in 88 patients (20 children and 68 adults) with age range of 6 months to 73 years. A review of prospectively collected data was conducted on adult and pediatric patients grafted with CEA at the Indiana University Medical Center for definitive wound coverage (TBSA 28-98%). These patients were followed up for 3 to 90 months. Complications, take rates, and outpatient follow-ups were noted. The mean final take rate of CEA/A was 72.7%, and the overall patient survival rate was 91% (80 of 88 patients). Complications were classified as early and late, they included: (early) blistering and shearing (31%), pruritus and itching (4.7%), (late) CEA loss (2 patients, 2.3%), and wound contractures (66%). Contracture releases were performed on 32 patients (36%); of which, 18 were children (56%). Cultured keratinocytes provide an excellent alternative or adjunct to conventional split-thickness skin grafting in treating large burn wounds. A dedicated team of physicians, nurses, and therapists well rehearsed in CEA care are vital for success in keratinocyte grafting. The final graft take of 72.7% with a 91% overall survival rate gives much optimism for continuing to use CEA in critically burned patients.

Xenoderm dressing in the treatment of second degree burns

BACKGROUND

In many countries the standard treatment of second degree burns includes the use of local antibacterial agents, frequent debridement of the wound, and frequent dressing changes, which are debilitating and costly. Since accurate information about alternative cures is scanty, this study was conducted to assess the outcome of the use of xenoderm biologic dressings as one alternative.

MATERIALS AND METHODS

This descriptive, goal-oriented sampling study was performed on 97 subjects suffering from deep partial thickness burns. Additionally, some of them had superficial and third degree burns. The patients underwent surgical operation and xenoderm dressings. The outcome of xenoderm application was considered such as frequency of dressings, hospital stay, the duration of analgesia use, wound infection, and the formation of granulation and scars at the burns site.

RESULTS

The results of this study indicate that the mean hospital stay from the time the patients were referred to the emergency ward was 6.45+/-5.51 days and it was 4.69+/-5.51 days from the time the operation was performed. The mean frequency of dressings in the interval between the use of xenoderm and the patients' discharge was 1.51+/-1.60 times. 22.9% (22 patients) of the patients did not take any analgesic after the operation. 27.1% of the patients had superficial infection at the burns site. Granulation tissue was observed in 46.9% of the patients.

CONCLUSION

The finding of the present study suggest that the use of xenoderm reduces the frequency of the dressings, Hospital stay, pain and analgesic. Therefore, the use of xenoderm in the treatment of second degree burns is recommended.

Performance and safety of skin allografts

Skin preservation for transplantation began almost 200 years ago with the pioneering work of Baronio (cited by in Ref. ). Since that time, hundreds of papers have been published on the preservation of skin for later application in wound treatment. This interest stems from the excellent clinical results obtained with skin as a permanent autograft or temporary allograft for wound cover, coupled with the relative ease of preservation and storage methods. The general recognition of the need for human skin allografts has stimulated the establishment of banking facilities and research to improve the methods for harvesting, processing, storage, and subsequent evaluation of transplantation performance.

Tissue regeneration. The past, the present and the future

Tissue engineering has been a topic of extensive research over the last years. The ability of human body to regenerate tissue loss such as bone, cartilage, nerves, skin and muscle is limited leading often to amputations of limbs or functional disability. The isolation of mesenchymal stem cells (MSCs) and later the embryonic stem cells in conjunction with the advances made in cellular biology, tissue engineering, genetics and recombinant technology has initiated the development of new techniques and new therapeutic strategies allowing treatment of many pathological conditions providing restoration of tissue continuity and function.

Use of dressings and bandages in equine wound management

The use and aims of various wound dressings are discussed. Application and indications in the horse vary according to the type and location of the wound as well as the nature and availability of the dressing material. Coaptation and immobilization are essential to promote healing in certain locations. Techniques used for bandage application in horses are described, with special emphasis on problem areas.

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.

Partial-thickness burns: identification and management

PURPOSE

To provide an overview of the appropriate evaluation and management of partial-thickness burns.

TARGET AUDIENCE

This continuing-education activity is intended for physicians and nurses with an interest in learning about burn wound care.

LEARNING OBJECTIVES

After reading the article and taking the test, the participant will be able to: 1. Describe the classification of burn wounds. 2. Identify characteristics of burn wounds and the clinical techniques for diagnosing burn wound depth. 3. Identify the treatment options for partial-thickness burns.