Preheat the oven to 375 degrees. Season the shanks all over with salt and pepper. In a heavy-bottomed 6- to 8-quart casserole (preferably cast iron), heat the olive oil until smoking. Place the shanks in the pan and brown all over, turning to get every surface, for 12 to 15 minutes. Remove the shanks and set aside. Reduce the heat to medium, add the carrot, onion, celery and thyme leaves and cook, stirring regularly, until golden brown and slightly softened, about 8 to 10 minutes. Add the tomato sauce, chicken stock and wine and bring to a boil. Place shanks back into the pan, making sure they are submerged at least halfway. If shanks are not covered halfway, add more stock. Cover the pan with a tight-fitting lid of aluminum foil. Place in oven for 2 to 2 1/2 hours and cook until meat is nearly falling off the bone.