| Summary: | Dermal fibroblasts are connected to each other and to elements of the
extracellular matrix (ECM). In vitro studies using fibroblasts grown in collagen
gels have demonstrated that fibroblasts are able to deform the gel via cell
adhesions. The purpose of this project was to investigate qualitatively the effect
of sinusoidal stretching of fresh strips of skin on both the mechanical response of
the tissue and the morphology of the fibroblasts. These investigations were
carried out for skin soaked in a physiological solution (Kreb's buffer) with and
without addition of a mast cell degranulating material, compound 48/80 (C48/80).
Two by 10 millimeters strips of skin were removed from the back of 3 male
rats. Skin samples were either only soaked in Kreb's buffer in the presence or
absence of C48/80, or simultaneously soaked and intermittently sinusoidally
stretched in Kreb's buffer in the presence or absence of C48/80. Controls
consisted of skin samples fixed immediately after excision from the rats or
samples only soaked in buffer. All tissues were fixed and processed for
transmission electron microscopy.
Morphometric analysis of the relative surface area of fibroblast
cytoplasmic extensions and cell bodies showed that sinusoidal stretching of rat
skin results in the retraction of fibroblast cytoplasmic extensions and "rounding
up" of the cells. Incubation with C48/80 alone had no apparent effect on
fibroblast cytoplasmic extensions and morphology.
The measurement of tension during sinusoidal stretching in Kreb's buffer
with or without addition of C48/80 demonstrated that the tension has a tendency to decrease as the number of sine wave cycles and stretching sequences
increased. In addition, during the 14.33 minute interval between two successive
stretching sequences the tissue demonstrated recovery of tension.
The decrease in tension observed as a result of biomechanical
experiments along with the "rounding up" of fibroblasts demonstrated in the
morphological study are consistent with the hypothesis that cell adhesions play a
role in the mechanical response of the tissue. The biomechanical and
morphological results, however, did not support the hypothesis that C48/80 alone
induces lost of fibroblast adhesions.
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