the 2007 Abstract Presentations - Wound Healing Society

Abstracts
137
OCCLUSION DECREASES HYPERTROPHIC SCARRING IN A
RABBIT EAR MODEL
K.D. O’Shaughnessy, N.K. Roy, T.A. Mustoe
Wound Healing Research Laboratory, Division of Plastic Surgery, Department
of Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL
Introduction: Previous studies in our laboratory have shown a reduction in
hypertrophic scarring by silicone gel sheet occlusion. We hypothesize that the
decrease in scar formation is due to hydration sensed by the epidermis and
therefore occlusion of a wound after epithelization is complete will decrease
scar formation, regardless of which occlusion material is used.
Methods: In an established rabbit model of hypertrophic scarring, 7 mm ear
punch wounds were created in 8 rabbits. The rabbits were divided into four
groups and wounds were occluded with Kelocote, Cavilon, Indermil or tape
stripping on days 14–28. Each rabbit served as its own internal control. All
wounds were harvested on day 28 and examined histologically to measure the
scar elevation index (SEI), epithelial thickness and cellularity. Ultrastructural
analysis was performed by electron microscopy.
Results: Kelocote, Cavilon and Indermil all significantly decreased SEI when
compared to hypertrophic scar controls. Tape stripping significantly increased
the SEI, epithelial thickness and cellularity. Under EM, the tape stripped
wounds displayed extensive intercellular edema, intracellular vacuoles, migratory
inflammatory cells and dense collagen. Both unwounded skin and occlusion
treated scars did not display these characteristics.
Conclusions: Hypertrophic scarring was reduced regardless of occlusive method
used. Furthermore, repeated disruption of the permeability barrier by tape
stripping lead to epidermal hyperplasia. This may be due to increased DNA
synthesis within the basal cell layer in an attempt to restore homeostasis within
the keratinocytes. Intercellular edema of the basal cell layer and intracellular
vacuoles seen in unoccluded and tape stripped wounds indicate inflammation
and keratinocyte damage. Occluded wounds may be in an advanced state of
wound repair returning to almost normal states of ultrastructure compared
with untreated or tape stripped skin. Occlusion may mimic the intact stratum
corneum and mediate its effects by hydration which is sensed by the epidermis.
This study was supported by an NIH grant awarded to T.A. Mustoe
139
CRYOPRESERVED AMNIOTIC MEMBRANE RELEASES
ANGIOGENIC FACTORS
S. Hennerbichler 1,2,3 , B. Reichl 1,2,3 , S. Wolbank 2 , J. Eibl 3 , C. Gabriel 2 , H. Redl 1
1 Ludwig Boltzmann Institute for Experimental and Clinical Traumatology,
Linz-Vienna, Austria,
2 Red Cross Blood Transfusion Service of Upper Austria, Linz, Austria,
3 Bio-Products & Bio-Engineering AG, Vienna, Austria
Preserved amniotic membrane is used in the field of ophthalmology and wound
care due to its supporting properties. Typically, amnion is used in a glycerol
preserved or freeze dried state. As we have shown previously, under such
conditions the majority of cells are dead, while preserving amnion in fresh or
frozen state under optimised conditions more than 20% of cells can be
preserved. Therefore we investigated which growth factors (GF) and cytokines
are released from cells in viable amnion to the culture medium. Fresh and
cryopreserved amnion was incubated for 48 h in protein free medium and the
medium afterwards screened for GF using a protein array system. Amnion was
also tested for viability and microbiological contamination. The amniotic
membrane was viable and sterile over the 48 hour period and the medium
contained GF and cytokines. Of the 20 protein spots on the array, the following
gave positive signals – Angiogenin, GRO, IL6/8, MCP-1, TIMP1/2, IGF-1.
Several growth factors and cytokines are released from cryopreserved amniotic
membrane which may be responsible for its supportive properties in tissue
regeneration. This work was partially supported by the Lorenz Bohler ¨ Fonds.
138
DERMAL FIBROBLASTS FROM RED DUROC AND
YORKSHIRE PIGS EXHIBIT INTRINSIC DIFFERENCES IN
THE CONTRACTION OF COLLAGEN GELS
I. de Hemptinne, C.L. Gallant-Behm, C.L. Noack, D.A. Hart
University of Calgary
Previous studies have shown that the Yorkshire (Y) pig is an ideal model for
skin wound healing, while red Duroc (RD) pigs form hyperpigmented,
hypercontracted scars similar to human hypertrophic scars (1–4). In order to
assess potential intrinsic differences in fibroblast phenotypes, the contraction
ability of ventral and dorsal dermal fibroblasts from Y and RD pigs was
determined in vitro. Cells were isolated from juvenile female pigs using
standard methods, propagated, and incorporated into collagen gels. Briefly, a
solution containing bovine collagen was combined with the isolated fibroblasts
over a dose range of 5 10 4 –5 10 5 cells/ml. The collagen was neutralized,
distributed into 24 well plates and allowed to solidify at 37 1C. Base media
(containing 2% FBS), or media with 10% FBS, 1 or 10 ng/ml TGFb1 was
added to each well and the matrix left for 24 hours before being released. The
gels were photographed at 0, 6, 24, 30 and 48 hours post-release time, and the
degree of contraction was quantified. The final contraction levels were dependent
on cell density and serum concentration for all cell types. The rates of
contraction of RD dorsal fibroblasts were significantly greater than those for Y
dorsal fibroblasts. The initial contraction rates for ventral fibroblasts were
higher than dorsal fibroblasts for both breeds. Supplementation media with
1–10 ng TGFb1 led to modest alterations in contraction rates, except for Y
ventral cells where contraction was significantly increased. These fibroblastpopulated
collagen matrix contraction studies revealed intrinsically different in
vitro responses with fibroblasts from the two breeds of pig. The findings also
indicate that at least some of the abnormal skin healing phenotype of RD pigs
may be attributable to these intrinsic differences in cellular behavior between
the breeds, and possibly yet to be identified mediators released during healing.
140
ENZYMATIC DEBRIDING AGENTS ARE SAFE IN WOUNDS
WITH HIGH BACTERIAL BIOBURDENS AND STIMULATE
HEALING
R.E. Salas, MD, D. Naidu, MD, F. Ko, BS, M.C. Robson, MD, G. Donate,
DPM, T.E. Wright, MD, W.G. Payne, MD
Institute for Tissue Regeneration, Repair, and Rehabilitation Bay Pines VA
Medical Center Bay Pines, Florida
Historically, proteolytic enzymes were reported to be unsafe in wounds with
significant bacterial bioburden unless used in conjunction with topical antimicrobials.
This study evaluated the two most frequently used enzymatic
debriding agents, collagenase and papain-urea in a rodent model of a chronically
infected granulating wound. Fifteen rats underwent a 30% TBSA dorsal
scald burn and were inoculated with 5 10 9 E. coli. On the 5th post-burn day,
escharectomies were performed leaving a granulating wound with 4 10 8 bacteria/gm.
of tissue. The wounds were treated with collagenase, papain-urea, or
saline dressings as a control. Every 72 hrs., wounds were traced for planimetry
and biopsied for quantitative bacteriology. Collagenase and papain-urea
statistically decreased the bacterial counts in the infected wounds compared
with the control (P o 0.05). They also accelerated wound closure in this model
compared with the control (P o 0.01). In conclusion, the common enzymatic
debriding agents appear safe and beneficial even in wounds with high tissue
levels of bacteria.
Wound Rep Reg (2007) 15 A14–A54 c 2007 by the Wound Healing Society
A51