Alteration of Protease Expression Phenotype of Mouse Peritoneal Mast Cells by Changing the Microenvironment as Demonstrated byin Situ Hybridization Histochemistry

Mouse mast cell protease (MMCP) mRNA expression was examined by in situ hybridization histochemistry. Peritoneal mast cells (PMCs) of WBB6F 1 -+/+ mice expressed MMCP-2, MMCP-4, MMCP-5, and MMCP-6 mRNAs, but did not express MMCP-1 mRNA. When proliferation of PMCs was induced by culturing them in methylcellulose with T cell-derived cytokines, cells in mast cell colonies expressed MMCP-1 mRNA. These mast cells were transferred to a suspension culture to induce further proliferation. The phenotype of the resulting PMC-derived cultured mast cells was similar to that of bone marrow-derived cultured mast cells. When 10 5 PMC-derived cultured mast cells or 10 5 bone marrow-derived cultured mast cells were injected into the stomach wall of mast cell-deficient WBB6F 1 - W/W v mice, mast cells that appeared in the mucosa and muscularis propria were similar to mast cells in the stomach of intact WBB6F 1 -+/+ mice, indicating the injected cells adapted to a new tissue environment. In contrast, when 10 5 PMCs were injected into the stomach wall of WBB6F 1 - W/W v mice, the injected PMCs did not adapt to the mucosa. When 20 PMCs were injected, they proliferated and adapted to the mucosal environment. The present results suggest that PMCs adapt to new environments when proliferation occurs before redifferentiation.