Malignant schwannoma-derived cells support human skin mast cell survival in vitro

We have recently observed mast cell infiltration in malignant schwannoma (MS) arising in the patient with von Recklinghausen's disease. To determine the cell to cell interactions between human skin mast cell (HSMC) and MS cell, we investigated the HSMC survival and the morphological changes when cultured with MS-derived cells isolated from the patient. Partially purified HSMCs obtained from normal adult skin and cutaneous neurofibroma by enzymatic digestion were cocultured with MS-derived cells on the coverslips. The number of HSMCs stained with crystal violet were directly counted by light microscope. HSMCs cocultured with MS-derived cell feeder layer revealed significantly increased HSMC survival compared to that with normal human skin fibroblast layer at 1 and 2 weeks. Conditioned medium of cultured MS-derived cell did not influence HSMC survival. In the morphology HSMCs cultured with MS-derived cells demonstrated spindle form in close contact with the adjacent MS-derived cells, suggesting cell to cell interactions. We failed to detect stem cell factor (SCF) mRNA in cultured MS-derived cell by RT-PCR. These results suggest that MS-derived cell is capable of supporting HSMC survival in vitro. Some factor(s) other than SCF, which is associated with direct contact between HSMCs and MS-derived cells, might relate to these observations.