A burn wound healing model in the hairless descendant of the Mexican hairless dog

Hairless descendants of Mexican hairless dogs: an experimental model for studying hypertrophic scars

BACKGROUND/OBJECTIVE

In previous studies, the author noticed hypertrophic scar formation in hairless dogs. The purpose of this study was to evaluate both grossly and histopathologically hypertrophic scars in hairless dogs to explore any similarities with hypertrophic scars in humans and to introduce these dogs as an appropriate model for further investigation on hypertrophic scarring.

METHODS

Full-thickness wounds were made on the dorsolumbar skin of hairless dogs. Hypertrophic scarring was examined with three methods: clinical observations, dihydroxyphenylalanine (DOPA)-positive melanocytes, and skin histopathology.

RESULTS

Hairless dogs clinically developed the formation of hyperpigmented and hypertrophic scars that did not extend beyond the original wound margins. In hypertrophic scars of hairless dogs, the split epidermal sheet showed an increased number of DOPA-positive melanocytes with well-developed dendrites exhibiting activated melanocytes. There were very few DOPA-positive melanocytes in the repaired skin of haired dogs. Histopathologic examinations demonstrated that hypertrophic scars were fully reepithelialized and granulation tissue formation was accompanied by inflammatory cell infiltration. There was remodeling of thick collagens and fine elastic fibers in the course of hypertrophic scar formation.

CONCLUSION

Experimental hypertrophic scars produced in hairless dogs have morphologic properties similar to those of human hypertrophic scars.

Morphological parameters for assessment of burn severity in an acute burn injury rat model

Determination of burn severity (i.e. burn depth) is important for effective medical management and treatment. Using a recently described acute burn model, we studied various morphological parameters to detect burn severity. Anaesthetized Sprague-Dawley rats received burns of various severity (0- to 14-s contact time) followed by standard resuscitation using intravenous fluids. Biopsies were taken from each site after 5 h, tissues fixed in 10% neutral-buffered formalin, processed and stained with haematoxylin and eosin. Superficial burn changes in the epidermis included early keratinocyte swelling progressing to epidermal thinning and nuclear elongation in deeper burns. Subepidermal vesicle formation generally decreased with deeper burns and typically contained grey foamy fluid. Dermal burns were typified by hyalinized collagen and a lack of detectable individual collagen fibres on a background of grey to pale eosinophilic seroproteinaceous fluid. Intact vascular structures were identified principally deep to the burn area in the collagen. Follicle cell injury was identified by cytoplasmic clearing/swelling and nuclear pyknosis, and these follicular changes were often the deepest evidence of burn injury seen for each time point. Histological scores (epidermal changes) or dermal parameter depths (dermal changes) were regressed on burn contact time. Collagen alteration (r(2) = 0.91) correlated best to burn severity followed by vascular patency (r(2) = 0.82), epidermal changes (r(2) = 0.76), subepidermal vesicle formation (r(2) = 0.74) and follicular cell injury was useful in all but deep burns. This study confirms key morphological parameters can be an important tool for the detection of burn severity in this acute burn model.

Effect of a hydrocolloid dressing on first intention healing surgical wounds in the dog: a pilot study

OBJECTIVES

To evaluate the efficacy of a hydrocolloid dressing for the treatment of surgical wounds in dogs.

METHODS

Six healthy young female dogs of medium size and different breed underwent ovariohysterectomy. Histological evaluation was performed on biopsies taken from the edges of the wounds at day 7. The dressing was applied on one half of the wound according to manufacturer's instructions; the second half served as control. Biopsy specimens were fixed in a 10% formalin buffered solution pH 7.4, paraffin embedded and stained with haematoxylin and eosin. For clinical assessment, the presence and quality of exudate, erythema of the surrounding area, swelling and correct apposition of the wound margins were evaluated.

RESULTS

The hydrocolloid dressing was easy to use. The clinical quality of the treated skin wounds was superior to the non-treated ones. Comparison of histological features between treated and untreated wounds showed a more regular organisation of the granulation tissue in the treated wounds, with fibroblasts being aligned parallel to the overlying epidermis. The number of inflammatory cells and the extension of granulation tissue were less prominent and less widespread in treated compared to untreated wounds.

CONCLUSION

The dressing performed very well in terms of adhesiveness and flexibility. It was useful in the management of surgical wounds to avoid contamination and ameliorate the epithelialisation rate and granulation tissue morphology of the surgical scar.

Isolation and culture of different epidermal and dermal cell types from human scalp suitable for the development of a therapeutical cell spray

BACKGROUND

Previous studies demonstrated, that cultured epithelial autografts (CEA) can be isolated and skin cell sprays can be produced for application on different types of wounds. The purpose of the present study was to determine which cell types can be isolated from the human scalp and whether these cells can be used for spray transplantation.

METHODS

Outer root sheath cells (ORS), keratinocytes, melanocytes, dermal papilla cells (DP), and dermal sheath cells (DSC) were isolated from human scalp tissue. Isolated cells were characterized, expanded and sprayed in an in vitro model. Growth behaviour, morphology and cell counts were compared with non-sprayed cells.

RESULTS

With acceptable time, equipment and laboratory personnel a sufficient amount of keratinocytes, ORS, melanocytes, DP cells and DSC cells could be achieved. The cells are sufficient for application as a cell spray. Cells, positive for Integrin alpha6, Cytokeratin 19, CD73 and CD105 were identified within the cultures.

CONCLUSIONS

Human scalp is suitable to gain epidermal and dermal cells for the development of therapeutic cell spray transplantation. Further studies have to determine, whether these cells can be combined to produce wound specific skin substitutes.

The use of fucosphere in the treatment of dermal burns in rabbits

The aim of this study was to prepare a new microsphere (fucosphere) system based on polyion complexation of fucoidan with chitosan, and to evaluate its treatment efficiency on dermal burns. The physicochemical properties such as mean particle size and distribution, zeta potential and bioadhesive properties of the microspheres were investigated. The formulation which had the high surface charge, narrow size distribution and the highest bioadhesive property was selected and applied on seven male New Zealand white rabbits with dermal burns. Biopsy samples were taken on day 7, 14 and 21. Each burn site was evaluated macroscopically and histopathologically and the findings were compared with controls of fucoidan solution and chitosan microspheres. The microspheres between the size ranges of 367 and 1017 nm were obtained. The work of bioadhesion of microspheres, with the surface charges +6.1 to +26.3 mV, changed between 0.081 and 0.191 mJ cm(-2). Macroscopically and histopathological observations indicated that the fastest healing of the burns was obtained in group treated with fucosphere after 21 days of treatment (P<0.05). Rete peg formation values and nuclear organize regions (NORs) were higher with treated fucospheres than the other groups on day 14. In conclusion, in vitro and in vivo evaluation of fucospheres indicated that the new microsphere system shortened the treatment period of burns and provided fast and effective healing by improving regeneration and re-epithelization. Hence fucosphere may find application in the treatment of dermal burns.

Photoepilation: a potential threat to wound healing in a mouse

BACKGROUND

Theoretically, the bulge area which is known to be a reservoir of epidermal stem cells should be destroyed to achieve permanent photoepilation. We wished to determine whether wound healing capability is perturbed after photoepilation.

METHODS

Twenty C57/BL6 mice were used. After wax epilation to synchronize the hair cycle, one-half of the backs of mice were photoepilated in the early anagen stage. After the two hair cycles of the mice to confirm the hair removal effect, 30% trichloroacetic acid was applied to the both halves of the backs of the mice. A skin biopsy was performed on both sides before and just after the injury, and 2, 6, 9, and 14 days thereafter. The specimens were evaluated histologically after staining with hematoxylin and eosin, Masson trichrome, and Verhoeff-van Gieson.

RESULTS

No differences in wound healing times were evident upon gross observation by the naked eye. However, the photoepilated hairless skin was observed to have a thicker epidermis and dermis than normal hairy skin by histological evaluation. The cellularity of the healed wound was much denser in the photoepilated. Collagen production of the neodermis in the normal hairy skin was first observed around the lower part of hair follicle, while it started from the upper papillary dermis in photoepilated skin.

CONCLUSION

Photoepilation may disturb the normal wound healing process, especially dermal wound healing, and increases the risk of producing hypertropic scar or keloid.

Hair follicle dermal sheath cells: unsung participants in wound healing

The dermal sheath that surrounds the outside of the hair follicle contains progenitor cells that maintain and regenerate the dermal papilla, a key component for hair growth. Our contention is that dermal sheath cells have other roles. We believe that they can become wound healing fibroblasts and perform an important function in the repair of skin dermis after injury. The dermal sheath has close developmental and anatomical parallels with follicle outer root sheath, the epithelial component that contains the stem cells responsible for replacing skin epidermis. Dermal sheath cells also have a myofibroblast or wound healing phenotype, and in animals with high follicle densities differences in wound healing are observed in conjunction with changes in the hair growth cycle. Similarly, in human beings there are apparent differences in wound healing responses between hairy and non-hairy body sites. Moreover, clinical and experimental data suggest that the involvement of follicle-derived dermal cells results in qualitatively improved dermal repair. Therefore, in a therapeutic context, hair follicle dermal cells provide an accessible option for the creation of dermal or full skin equivalents that could both improve wound healing and reduce scarring. Indeed, given the inductive properties of adult hair follicle dermal cells, it is reasonable to envisage a tissue engineering approach for the production of a skin equivalent that will grow hair follicles when grafted.

Electrolyzed strong acid aqueous solution irrigation promotes wound healing in a burn wound model

The purpose of the study was to understand the effectiveness of electrolyzed strong acid aqueous solution (ESAAS) for acceleration of epithelialization in a rat burn wound model. Eighteen anesthetized Sprague-Dawley rats received 30% total body surface area third-degree burns, and 2 days after injury, the wound eschars were removed. Rats were divided into 3 groups: Group 1, no irrigation; Group 2, irrigation with physiological saline; and Group 3, irrigation with ESAAS. Wounds were observed macroscopically until they were fully epithelialized, and epithelialized wounds were examined microscopically. Epithelialization of the wounds occurred significantly early in the rats treated with ESAAS (p < 0.05). Proliferation of associated lymphocytes and macrophages was more extensive in all rats that underwent irrigation than it was in control rats. ESAAS irrigation may promote tissue growth in burn wounds.

A standardized model of partial thickness scald burns in mice

BACKGROUND

Large mammal partial thickness wound models were developed primarily for their anatomical similarity to human wounds, yet lack the economy, ease of handling, and statistical power afforded with rodent models. Previous small mammal models of partial thickness burn injury have failed to demonstrate complete reepithelialization in less than 3 weeks. We present a murine partial thickness scald model with a reepithelialization rate comparable to that of porcine wound models.

METHODS

Thirty-eight adult male mice were secured in a burn template allowing exposure of a 2 x 3-cm area of the shaved dorsum to 60 degreesC water for 45 s, followed by 4 degreesC water for 45 s. Four wounds were harvested daily on Postburn Days 1-7, 10, and 14 for histologic evaluation.

RESULTS

Histologic evidence of partial thickness dermal injury with sparing of dermal appendage epithelial cells was seen in all wounds. Of 134 wound sections evaluated 26 contained some areas of full thickness dermal injury, with only 8 of these 26 sections showing full thickness injury in 50% or more of the cross-sectional area of the wounds. Complete wound reepithelialization was seen between Postburn Days 10 and 14. The viable dermal thickness in all burn cross sections was at least 40-80 micrometers, and up to 1400 micrometers in reepithelialized wounds.

CONCLUSIONS

This murine model of partial thickness scald injury provides a standardized thermal wound with consistent depth of injury, low mortality, and a reepithelialization rate between 10 and 14 days. A simple protocol allows easy production of 30-50 wounds daily with one technician.

Burn healing in organ cultures of embryonic chicken skin: a model system

Burn wounds cause complex damage to the skin. Unlike simple cuts, burns cause a graded damage at the margin of the wound and leave biochemically complex debris in the wound, two factors that complicate the process of wound healing. To develop an in vitro system for studying cellular responses to burns in whole tissue, we have applied a standardized burn wound to organ cultures of embryonic chicken skin and evaluated cellular changes in response to the burn damage. This simplified system is not subject to uncontrolled infection and does not involve angiogenesis and granulation. Thus, these cultures provide a simplified model of how cells of the dermis and epidermis in and around a burn wound respond to heat damage early in the process of healing.