A tissue modification apparatus includes a first and a second guide, a first and a second set of mounts, and a first and a second actuator. The first guide defines a first axis, and the second guide defines a second axis intersecting the first axis. The mounts of the first set of mounts are movable relative to one another along the first axis, and the mounts of the second set of mounts are movable relative to one another along the second axis. The first actuator and the second actuator are each settable to a stress load, with the first actuator and the second actuator movable, respectively, along the first axis and the second axis to transmit each respective stress load to a piece of tissue mechanically coupled to the first and second set of mounts.