Volume 152, Issue 6 pp. 1149-1160

Mast cell tryptase and chymase in chronic leg ulcers: chymase is potentially destructive to epithelium and is controlled by proteinase inhibitors

M. Huttunen

M. Huttunen

Department of Dermatology, Kuopio University Hospital, POB 1777, 70211 Kuopio, Finland

Department of Dermatology, Helsinki University Central Hospital, Helsinki, Finland

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I.T. Harvima

I.T. Harvima

Department of Dermatology, Kuopio University Hospital, POB 1777, 70211 Kuopio, Finland

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First published: 24 March 2005
Citations: 42
Ilkka T. Harvima.
E-mail: [email protected]

Conflicts of interest: none declared.

Summary

Background Numerous mast cells are present in chronic leg ulcers. Tryptase and chymase are the major mediators of mast cells, but their significance is mostly dependent on their activity. In addition, the proteinases may affect ulcer epithelialization.

Objectives To study levels and activity of tryptase and chymase in wash samples and biopsies from chronic leg ulcers and the possible effect of these proteinases on keratinocyte growth and adherence.

Methods Wash samples were taken from 16 patients and a superficial shave biopsy was taken in eight of these patients; a second biopsy series was obtained from the edge of chronic venous leg ulcers (n = 6).

Results Significant levels of soluble tryptase activity and histamine, but low levels of chymase activity, were measured in wash samples from chronic ulcers. No tryptase-inhibiting activity, but clear chymase-inhibiting activity, was detected in the wash samples. In superficial wound bed biopsies, relatively marked levels of chymase activity together with histamine and tryptase activity were detected. In the second biopsy series, about 80% of the mast cells belonged to the MCTC type (tryptase- and chymase-immunopositive). However, about 55–61% of the chymase-immunopositive cells displayed chymase activity and 64 ± 17% of the tryptase-positive cells revealed immunoreactivity of α1-antichymotrypsin. As the activity of chymase and tryptase was detected in the ulcer base in a ratio of 1 : 8, a preparation containing both chymase and tryptase was partially purified from human skin yielding a similar activity ratio of 1 : 11–13. Treatment of fibronectin-coated plastic surfaces with this preparation decreased the adherence of cultured human keratinocytes, this effect being attributable mainly to chymase. In 2-day cultures using growth factor/serum-deficient low- or high-calcium medium, the tryptase–chymase preparation inhibited the slow growth and at higher concentrations it even induced detachment of keratinocytes. This effect was attributed to chymase, and it was partially regulated by heparin and histamine.

Conclusions Even though chymase is partially inactivated in chronic leg ulcers, accumulated mast cells in the close proximity of the epithelium edge and their chymase may impair keratinocyte adherence and migration.

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