Increased expression of matrix metalloproteinase-2, matrix metalloproteinase-9 and matrix metalloproteinase-13 in lesional skin of bullous pemphigoid.

BACKGROUND

Matrix metalloproteinase (MMP)-2, MMP-9 and MMP-13 can degrade type IV collagen which is the major component of the basement membrane zone (BMZ). In bullous pemphigoid (BP), the separation occurs within the BMZ.

OBJECTIVE

To evaluate the involvement of MMPs in the pathogenesis of BP, we examined the expression of MMP-2, MMP-9 and MMP-13 in the lesional skin of BP patients.

METHODS

The expression of MMP-2, MMP-9, MMP-13, tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2 was analyzed by immunohistochemistry in the lesional skin of BP patients in comparison with that in normal human skin. Next, the cellular sources of MMP-2, MMP-9 and MMP-13 were analyzed by double immunohistochemistry. Finally, the levels of these MMPs in the serum and blister fluid of BP patients were measured by ELISA.

RESULTS

The number of cells expressing MMP-2, MMP-9 and MMP-13 were significantly increased in the lesional skin of BP patients as compared to that in normal skin. Although the number of cells expressing TIMP-1 and TIMP-2 were also increased in the lesional skin of BP patients as compared to that in normal skin, the ratio of MMPs to TIMPs in the lesional skin of BP patients was high (2.4:1). T cells comprised the major source of MMP-2, MMP-9 and MMP-13, while a proportion of mast cells and eosinophils also expressed these MMPs. Furthermore, marked expression of MMP-2 was detected in the epidermal keratinocytes. The levels of these MMPs in the blister fluid were significantly greater than those in the serum.

CONCLUSION

These results suggest that MMP-2, MMP-9 and MMP-13 may be involved in the mechanism of blister formation in BP and that besides infiltrating inflammatory cells, structural cells like epidermal keratinocytes may also participate in the induction of blister formation in BP.