Interaction between isolated human myocardial mast cells and cultured fibroblasts

Abstract

Introduction: Previously, we reported an increase in interstitial collagen and total mast cell numbers in heart failure versus normal myocardium. A secondary increase, primarily in chymase-negative mast cells, occurred following LVAD-support compared to matched pre-LVAD tissue samples and was associated with a decrease in interstitial collagen and bFGF. We investigated the direct interaction between mast cells, isolated from failing myocardium with or without previous LVAD support, and human fibroblasts in a co-culture model. Methods: Myocardial tissue was obtained from 10 patients with endstage dilated cardiomyopathy (DCM) at the time of transplantation. Five patients were transplanted following LVAD support, five patients without previous LVAD support. Mast cells were isolated according to a standard protocol, including collagenase digestion and cell separation. The isolated mast cells were co-cultured with human fibroblasts for 12 hours, with or without stimulation of degranulation and protein synthesis was measured by [3H]-proline incorporation. Results: Mast cells isolated from unsupported DCM tissue caused a 92% increase in [3H]-proline incorporation in fibroblasts after stimulation compared to mast cell free culture (p < 0.01), while mast cells isolated from LVAD supported myocardium decreased the [3H]-proline incorporation by 63% (p < 0.01) and consequently the protein production. Unstimulated mast cells did not significantly alter the protein production over baseline. Conclusion: We demonstrate that fibroblast protein production in vitro is significantly altered by mast cells and that the direction of change is dependent on whether myocardium was supported by LVAD. We suggest, that under long-term LVAD support there is a phenotypic alteration in mast cells, which leads to a change in mediators’ concentration and/or composition, capable of re-remodeling the myocardial matrix.