What aspect is NOT part of the definition of tissue engineering?

The definition of tissue engineering encompasses several key aspects, particularly the integration of biology and engineering principles to create functional tissues or to develop methods for tissue repair. In this context, the correct choice highlights that the use of the body's natural regeneration mechanisms for tissue repair is not explicitly part of tissue engineering's primary definition. While tissue engineering may indeed support and enhance the body's healing processes, it fundamentally focuses on creating tissues or cellular products in vitro (outside the body) and developing technologies to better manage tissue repair through engineered solutions.

The other aspects mentioned, such as the integration of biology with engineering, creating tissues outside the body, and improving tissue repair, are central to tissue engineering. They reflect the field's innovation in synthesizing functional biological substitutes using designed scaffolds, cells, and various bioactive molecules, whereas option D focuses on an inherent biological process that tissue engineering seeks to augment rather than its direct definition.