PHENOTYPIC DIFFERENCES IN GROWTH, MATRIX SYNTHESIS AND RESPONSE TO NIFEDIPINE BETWEEN FIBROBLASTS DERIVED FROM CLINICALLY HEALTHY AND OVERGROWN GINGIVAL TISSUE

Gingival overgrowth is a disfiguring condition affecting 10-20% of pat ients on nifedipine therapy. The pathogenesis of this condition, altho ugh unclear, is thought to involve an interaction between the drug and resident gingival fibroblasts. The aim of the present study was to in vestigate the cellular mechanisms underlying this condition using cell culture techniques, Gingival fibroblast cell lines were derived by ex plant culture from two patients on long-term nifedipine therapy exhibi ting gingival overgrowth (`responders') and from two patients on simil ar therapy with clinically healthy gingiva ('non responders'). Compara tive studies showed phenotypic differences between the two cell types, 'responder' cells having an increased growth potential and producing increased levels of protein and collagen compared to 'non responder' l ines. Addition of exogenous nifedipine (10-1000 ng/ml) to cultures had no effect on 'non-responder' cells but induced a significant inhibito ry response in the 'responder' cells. Although adding support to the c oncept that nifedipine-sensitive fibroblasts reside within overgrown c onnective tissue, the inhibitory effect of the drug on cell growth and matrix synthesis was surprising in view of the clinical appearance of this condition.