Oral Lichen Planus

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Sugarman PB, et al. The pathogenesis of oral lichen planus. Crit Rev Oral Biol Med 2002;13:350-365.

Roopashree MR, et al. Pathogenesis of oral lichen planus – a review. J Oral Pathol Med 2010;39:729-734.

THE EPITHELIAL BASEMENT MEMBRANE As discussed above, epithelial basement membrane changes are common in OLP and include breaks, branches, and duplications (Jungell et al., 1989a; Zhou et al., 2001). Keratinocytes contribute to the structure of the epithelial basement membrane by secreting collagen IV and laminin V into the basement membrane zone (Marinkovich et al., 1993). Presumably, apoptotic keratinocytes are no longer able to perform this function. Hence, keratinocyte apoptosis triggered by intra-epithelial CD8+ cytotoxic T-cells may result in epithelial basement membrane disruption in OLP. Conversely, evidence from the involuting mouse mammary gland model suggests that keratinocytes require a basement-membrane-derived cell survival signal to prevent the onset of apoptosis (Pullan et al., 1996). Hence, epithelial basement membrane disruption may trigger keratinocyte apoptosis in OLP. An intriguing question in OLP is which came first — keratinocyte apoptosis or epithelial basement membrane disruption? Both mechanisms may be involved in the pathogenesis of OLP, e.g., basement membrane disruption may trigger keratinocyte apoptosis, and apoptotic keratinocytes may be unable to repair the disrupted basement membrane. Such a cyclical mechanism may underlie disease chronicity.

The epithelial basement membrane Keratinocytes contribute to the structure of the epithelial basement membrane by secreting collagen IV and laminin V into the basement membrane zone. Also evidence from the involuting mouse mammary gland model suggests that keratinocytes require a basementmembrane- derived cell survival signal to prevent the onset of apoptosis (3). Thus basement membrane is required for keratinocyte survival and keratinocyte for normal basement membrane production (Fig. 3). Apoptotic keratinocytes are no longer able to perform this function. Hence, keratinocyte apoptosis triggered by intra-epithelial CD8+ cytotoxic T cells may result in epithelial basement membrane disruption in OLP, which allows the non-specific T lymphocytes present in the sub epithelial zone to migrate into the epithelium. Both keratinocyte apoptosis and basement membrane disruption may be involved in the pathogenesis of OLP, e.g., basement membrane disruption may trigger keratinocyte apoptosis, and apoptotic keratinocytes may be unable to repair the disrupted basement membrane. Such a cyclical mechanism may underlie disease chronicity (3, 5).