Preheat oven to 375°F. Cook the sausage, peppers, celery and onion in a large skillet over medium heat for 8-10 minutes or until the sausage is thoroughly cooked. Pour into a large bowl. Add the panko bread crumbs, poultry seasoning, celery seed, sage and chicken broth. Stir to mix ingredients. Spoon into a lightly greased casserole dish. Bake for 30 minutes.