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Granulation tissues, hypertrophic scars, hypertrophic scars treated with mechanical pressure and mature scars from deep thermal injuries, or equivalent trauma, were examined for the presence and dermal distribution of mast cells. Statistical analyses of mast cell counts indicate that 1) the hypertrophic scar contains significantly greater numbers of mast cells than the other tissues studied. 2) as granulation tissue develops interstitial collagen, mast cells begin to appear, 3) mature scars contain significantly fewer mast cells than hypertrophic scars, 4) based on mast cell data, the effect of pressure therapy is first detected in the upper and middle reticularis of the dermis, and 5) on a mast cell statistical basis mature scar and hypertrophic scar under pressure are indistinguishable.

Fibronectin (FN) distribution was compared among samples of normal human dermis, hypertrophic scar, keloid, and granulation tissues from deep injuries. Localization was established by use of fibronectin antibodies and the indirect immunofluorescence method. Fresh-frozen tissue was sectioned on a cryostat and examined by epifluorescence. Hypertrophic scar and keloid demonstrated heavy deposition of FN, which conformed to the nodular characteristics of the lesions. Intense localization occurred in granulation tissue over fibroblasts which were stellate and vesiculated, and over small blood vessels. FN-staining was weak in areas over fibroblasts which were more rounded and nonvesiculated. Staining for FN was also minimal over the collagen in normal dermis and the deeper, larger collagen fascicles in the lesions. Fibroblasts cultured from normal dermis, hypertrophic scar, and keloid for 5-6 weeks were intensely stained for FN. Extracellular matrix was heavily positive in cultures from the lesions compared with those from normal dermis.

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