Pei-Yun Liu

A denatured collagen microfiber scaffold seeded with human fibroblasts and keratinocytes for skin grafting

Biomaterial scaffolds are categorized into artificial or natural polymers, or combinations of the two. Artificial polymers often undergo serum protein adsorption, elicit foreign body and encapsulation immune responses post-implantation. Large pore bovine electrospun collagen I was therefore screened as a candidate for human keratinocyte and fibroblast cell scaffolds. Human HaCaT keratinocyte and dermal fibroblasts were seeded on electrospun denatured collagen I microfiber (DCM) scaffolds and after 72 h Livedead(®) assays performed to determine adhesive cell, survival and scaffold penetration. Both keratinocytes and fibroblasts attached to and survived on DCM scaffolds, however only fibroblasts migrated over and into this biomaterial. HaCaT keratinocytes remained largely stationary on the scaffold surface in discrete islands of monolayered cells. For this reason, normal human epidermal keratinocyte (NHEK) scaffold interactions were assessed using scanning and transmission electron microscopy (EM) that demonstrated DCM scaffolds comprised networks of interlocking and protruding collagen fibers with a mean diameter of 2-5 μm, with a mean inter-fiber pore size of 6.7 μm (range 3-10 μm) and scaffold thickness 50-70 μm. After 72 h the keratinocytes and fibroblasts on DCM scaffolds had attached, flattened and spread over the entire scaffold with assembly of lamellapodia and focal adhesion (FA)-like junctions. Using transmission EM, NHEKs and HaCaT keratinocytes assembled desmosomes, lamellapodia and FA junctions, however, neither hemidesmosomes nor basal lamina were present. In long term (21 day) co-culture fibroblasts migrated throughout the scaffold and primary keratinocytes (and to a lesser extend HaCaTs) stratified on the scaffold surface forming a human skin equivalent (HSE). In vivo testing of these HSEs on immunocompetent (BalbC) and immunodeficient (SCID) excisionally wounded model mice demonstrated scaffold wound biocompatibility and ability to deliver human cells after scaffold biodegradation.

The optimal duration and delay of first aid treatment for deep partial thickness burn injuries.

Using our porcine model of deep dermal partial thickness burn injury, various durations (10min, 20min, 30min or 1h) and delays (immediate, 10min, 1h, 3h) of 15 degrees C running water first aid were applied to burns and compared to untreated controls. The subdermal temperatures were monitored during the treatment and wounds observed weekly for 6 weeks, for re-epithelialisation, wound surface area and cosmetic appearance. At 6 weeks after the burn, tissue biopsies were taken of the scar for histological analysis. Results showed that immediate application of cold running water for 20min duration is associated with an improvement in re-epithelialisation over the first 2 weeks post-burn and decreased scar tissue at 6 weeks. First aid application of cold water for as little as 10min duration or up to 1h delay still provides benefit.

Silver deposits in cutaneous burn scar tissue is a common phenomenon following application of a silver dressing

Background:  Silver dressings have been widely and successfully used to prevent cutaneous wounds, including burns, chronic ulcers, dermatitis and other cutaneous conditions, from infection. However, in a few cases, skin discolouration or argyria‐like appearances have been reported. This study investigated the level of silver in scar tissue post‐burn injury following application of Acticoat™, a silver dressing.

Silver absorption on burns after the application of Acticoat: data from pediatric patients and a porcine burn model.

Silver dressings have been widely used to successfully prevent burn wound infection and sepsis. However, a few case studies have reported the functional abnormality and failure of vital organs, possibly caused by silver deposits. The aim of this study was to investigate the serum silver level in the pediatric burn population and also in several internal organs in a porcine burn model after the application of Acticoat™. A total of 125 blood samples were collected from 46 pediatric burn patients. Thirty-six patients with a mean of 13.4% TBSA burns had a mean peak serum silver level of 114 &mgr;g/L, whereas 10 patients with a mean of 1.85% TBSA burns had an undetectable level of silver (<5.4 &mgr;g/L). Overall, serum silver levels were closely related to burn sizes. However, the highest serum silver was 735 &mgr;g/L in a 15-month-old toddler with 10% TBSA burns and the second highest was 367 &mgr;g/L in a 3-year old with 28% TBSA burns. In a porcine model with 2% TBSA burns, the mean peak silver level was 38 &mgr;g/L at 2 to 3 weeks after application of Acticoat™ and was then significantly reduced to an almost undetectable level at 6 weeks. Of a total of four pigs, silver was detected in all four livers (1.413 &mgr;g/g) and all four hearts (0.342 &mgr;g/g), three of four kidneys (1.113 &mgr;g/g), and two of four brains (0.402 &mgr;g/g). This result demonstrated that although variable, the level of serum silver was positively associated with the size of burns, and significant amounts of silver were deposited in internal organs in pigs with only 2% TBSA burns, after application of Acticoat™.

The efficacy of Aloe vera, tea tree oil and saliva as first aid treatment for partial thickness burn injuries.

Many alternative therapies are used as first aid treatment for burns, despite limited evidence supporting their use. In this study, Aloe vera, saliva and a tea tree oil impregnated dressing (Burnaid) were applied as first aid to a porcine deep dermal contact burn, compared to a control of nothing. After burn creation, the treatments were applied for 20 min and the wounds observed at weekly dressing changes for 6 weeks. Results showed that the alternative treatments did significantly decrease subdermal temperature within the skin during the treatment period. However, they did not decrease the microflora or improve re-epithelialisation, scar strength, scar depth or cosmetic appearance of the scar and cannot be recommended for the first aid treatment of partial thickness burns.

Burn healing is dependent on burn site : A quantitative analysis from a porcine burn model

This retrospective review examines healing in different sites on a porcine burn model; 24 pairs of burns on 18 pigs from other animal trials were selected for analysis. Each pair of burns was located on the either the cranial or the caudal part of the thoracic ribs region, on the same side of the animal. The burns were 40-50 cm(2) in size and of uniform deep-dermal partial thickness. Caudal burns healed significantly better than cranial burns, demonstrated by earlier closure of wounds, less scar formation and better cosmesis. To our knowledge, this is the first detailed study reporting that burn healing is affected by location on a porcine burn model. We recommend that similar symmetrical burns should be used for future comparative assessments of burn healing.

Conservative surgical debridement as a burn treatment: Supporting evidence from a porcine burn model

In thermal deep‐dermal burns, surgical debridement is normally used in conjunction with skin grafting or skin substitutes and debridement alone as a burn treatment is not usually practiced. The current study addresses whether or not debridement alone would enhance burn wound healing on small deep‐dermal‐partial thickness burns. This was a prospective and blinded experimental trial using a porcine deep‐dermal‐partial thickness burn model. Four burns, approximately 50 cm2 in size, were created on each of eight pigs. Two burns from each pig were immediately surgically debrided and the other two were not debrided as the internal control. Hydrate gel together with paraffin gauze were used to cover the burns for four pigs and silver dressings for the other four. Clinical assessment of wound healing was conducted over a 6‐week period. Skin samples were collected at the end of the experiment and histopathological evaluation was performed. The results show thinner scar formation and lower scar height in the debrided compared with nondebrided wounds in the hydrate gel/paraffin gauze groups. There were no statistically significant differences in wound healing assessment between the debrided and nondebrided wounds dressed with silver dressings. This study provides supporting evidence that immediate debridement with an appropriate dressing and without skin grafting may promote wound healing, suggesting its potential benefit for clinical patients.

Fetuin-A: A Major Fetal Serum Protein that Promotes “Wound Closure” and Scarless Healing

Burn-wound healing is a dynamic, interactive process involving a number of cellular and molecular events and is characterized by inflammation, granulation tissue formation, re-epithelialization, and tissue remodeling (Greenhalgh, 2002; Linares, 2002). Unlike incisional-wound healing, it also requires extensive re-epithelialization due to a predominant horizontal loss of tissue and often heals with abnormal scarring when burns involve deep dermis. The early mammalian fetus has the remarkable ability to regenerate normal epidermis and dermis and to heal dermal incisional wounds with no signs of scarring. Extensive research has indicated that scarless healing appears to be intrinsic to fetal skin (McCallion and Ferguson, 1996; Ferguson and O’Kane, 2004). Previously, we reported a fetal burn model, in which 80-day-old ovine fetuses (gestation¼ 145–153 days) healed deep dermal partial thickness burns without scars, whereas postnatal lambs healed equal depth burns with significant scarring (Cuttle et al., 2005; Fraser et al., 2005). This burn model provided early evidence that fetal skin has the capacity to repair and restore dermal horizontal loss, not just vertical injuries.

Fetuin-A promotes primary keratinocyte migration: independent of epidermal growth factor receptor signalling

Please cite this paper as: Fetuin‐A promotes primary keratinocyte migration: independent of epidermal growth factor receptor signalling. Experimental Dermatology 2010; 19: e289–e292.

Burn Wound Infection in a Porcine Burn Model

Burn wound infection is a serious complication of thermal injury and is categorized into wound colonization, wound infection, invasive infection, cellulitis, and necrotizing infection. Clinically, the diagnosis of wound infection mostly relies on the clinical symptoms and examination of burn wounds. In the past 4 years, we have developed a porcine burn model and assessed a total of 304 thermal burns sized 40 to 50 cm (from 130 large white pigs). Wound colonization/infection was judged clinically (details in Table 1), and 19.4% of wounds (59 of 304) were recorded having 2 colonization scores at least once over a 6-week period. In one of animal trials, a total of 228 skin biopsies (from 16 burns/4 pigs) were collected at 0 to 14 days postburn injury (Table 2) and Gram staining of these biopsies was conducted to validate the clinical judgement. Clinically, no wound colonization (defined as scores of 0–1) was recorded from days 0 to 9. However, at day 14 wound colonization (defined as scores of 2–3) was noticed in localized areas of four wounds. Consistent with the clinical finding, no bacteria was found in the viable tissue from samples took at days 0 to 9 and from 96% samples (71 of 74) collected from clinically noncolonized areas at day 14 (a very low number of bacteria in 4% clinical negative samples). However, all 12 wound biopsies collected from clinically colonized areas had bacteria in the viable tissue and these bacteria were mostly scattered in the dermis with some in the macrophages and neutrophils. We agree with others that regular clinical examination of the entire burn wound surface, though subjective, is the most useful and reliable method of diagnosing burn wound infection. Histological examination is more objective, but is an invasive approach, and can only analyze sampled areas of burn wounds rather than representing the whole burn wound.