CREATE TABLE table_5315 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" TEXT, "Result" TEXT)

Who was first elected as the result of a retired republican gain in the district of ohio 21?
SELECT "First elected" FROM table_5315 WHERE "Result" = 'retired republican gain' AND "District" = 'ohio 21'
SELECT "First elected" FROM "table_5315" WHERE "District" = 'ohio 21' AND "Result" = 'retired republican gain'