Conductivity of a chronic wound model.
The dermal equivalent matrix (DEM) is well recognized as an in vitro model of wound healing. To quantify the low-frequency (10-100 Hz) electric fields that cause proliferative effects in this model, determination of conductivity is a prerequisite. This article outlines a four-electrode technique to establish conductivity of DEM at 100 Hz. DEM is fabricated from human foreskin fibroblasts and collagen type I extracted from rat tail. Over 8-10 days, fibroblasts contract translucent collagen matrices into opaque circular "dime-sized" structures that are approximately 10 mm in diameter and 1 mm thick. To determine conductivity, rectangular samples are cut from each matrix. Thickness and width of each sample is measured by microscopy. Over 17 experiments, conductivity of multiple samples is found to be related inversely to cell density in matrix, with 1.22 Siemens/meter (S/m) corresponding to 0 cells/mm3 matrix and 0.78 S/m corresponding to 2.6 x 10(4)cells/mm3. These results are consistent with a physical model of DEM consisting of pores within a framework of type I collagen; the cells and medium are within the pores. The model is most compatible with a relative pore area of 73% and a cell volume of 9.0 x 10(-6)mm3 (the latter in agreement with published fibroblast dimensions). From these results, DEM is much more porous than dermis. Although DEM has been recognized as a reasonable model of chronic wound healing, this dissimilarity is noted.
Goldman
R
R
Department of Rehabilitation Medicine, University of Pennsylvania, Philadelphia 19104, USA.
Pollack
S
S
D000465:Algorithms; D000818:Animals; D002449:Cell Aggregation; D002452:Cell Count; D002455:Cell Division; D002478:Cells, Cultured; D003094:Collagen / Q000502:physiology; D004553:Electric Conductivity; D004560:Electricity; D004566:Electrodes; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006801:Humans; D008853:Microscopy; D008954:Models, Biological; D016062:Porosity; D051381:Rats; D012867:Skin / Q000166:cytology / Q000293:injuries; D012879:Skin Physiological Phenomena; D014945:Wound Healing
D003094:Collagen