¹Sutton Arthritis Research Laboratories, Department of Rheumatology, Institute of Bone and Joint Research, The University of Sydney at Royal North Shore Hospital, St Leonards, New South Wales, Australia

Correspondence: Dr Meilang Xue, Sutton Research Laboratories, Department of Rheumatology, Institute of Bone and Joint Research, Level 1, Block 4, The University of Sydney, Royal North Shore Hospital, St Leonards, New South Wales 2065, Australia. E-mail: mlxue@med.usyd.edu.au

Received 18 December 2007; Revised 3 April 2008; Accepted 6 April 2008; Published online 22 May 2008.

Abstract

Cultured human keratinocytes produce matrix metalloproteinase (MMP)-2 and MMP-9. In this study, using small interfering RNA (siRNA) for MMP-2 or MMP-9, we investigated the functions of these two gelatinases in the regulation of survival by measuring growth, differentiation, apoptosis, and migration of cultured keratinocytes. MMP-2 siRNA treatment significantly decreased keratinocyte growth and migration, and stimulated apoptosis fourfold. In addition, MMP-2 siRNA caused a 70% reduction in keratin-14 (K14) and a fourfold increase in K10. In contrast, MMP-9 siRNA treatment exerted opposite effects on cell growth, apoptosis, and K10 expression. MMP-2 appears to act through the ERK MAP kinase and caspase-3 signaling pathways as evidenced by the 53% reduction in the level of phosphorylated ERK1/2 and threefold increase in phosphorylated p38 and stronger staining for active caspase-3 in response to MMP-2 siRNA. Dual fluorescent staining revealed that almost all cultured cells stained positive for MMP-2, with only a few scattered cells being positive for MMP-9. There were considerably more BrdU-positive cells following MMP-9 siRNA treatment, indicating that MMP-9 inhibited proliferation. In conclusion, MMP-2 stimulates keratinocyte survival whereas MMP-9 promotes terminal differentiation.