FIBROBLAST GROWTH IN-VITRO SUPPRESSED BY LPS-ACTIVATED MACROPHAGES - REVERSAL OF SUPPRESSION BY HYDROCORTISONE

Activated macrophages are among the major constituents of the periapic al granuloma, Their state of activation may persist for long periods a fter the local irritant is removed and may delay resolution and repair of the lesion. The effect of activated macrophages on fibroblast grow th was studied in vitro, Circular fibroblast colonies were formed usin g a drop containing 7.5 x 10(5) murine dermal fibroblasts and allowed to grow for 7 days, When peritoneal exudate macrophages were added (0. 5-3.0 x 10(6) cells/dish) and activated in vitro by LPS (1 mu g/ml), t he fibroblast colony's growth was suppressed, LPS alone, at the concen tration used, had no effect on the fibroblast growth, Hydrocortisone ( greater than or equal to 10(-7) M) totally reversed the suppression, w hen added either simultaneously with or 6, 24, or 48 h after the LPS, The efficacy of late hydrocortisone treatment suggests that its effect was through prevention of the expression of the LPS activation of the macrophages. These findings may provide a possible clue to a pharmaco logical modulation of the healing processes that occur in the periapic al lesion once its infective source had been eliminated.