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Surgical Therapies and Tissue Engineering: At the Intersection Between Innovation and Regulation.

Innovations in tissue engineering and regenerative medicine are often realized in the operating room as surgeons restore form and function using biomaterials and grafted tissues. Examples seen every day in operating rooms around the world include the use of decellularized dermal matrix allograft or xenograft for reconstructing the abdominal wall, chest wall, or the pelvic floor. In breast reconstruction, acellular dermal matrix is commonly used along with silicone implants to provide a supportive structure to the surrounding tissues. The practice of autologous fat grafting is utilized to reconstruct tissues throughout the body using minimally invasive harvest techniques, and additives such as platelet-rich plasma have been employed. In cases of nasal reconstruction, cartilage grafts are taken from the ear and combined with a tissue flap to provide shape. For ear reconstruction, rib cartilage is harvested and carved to match the shape of the normal ear before implanting. The ready availability of biomaterials and tissue transfer techniques enable new reconstructive solutions facilitated by the creativity of the surgeons applying them. This is well evidenced by the development of techniques for ‘‘prefabricated’’ flaps, in which tissue grafts from other parts of the body are assembled in a heterotopic location within the boundaries of a tissue flap that will be harvested and transferred at a later date. A specific example is building structures of a nose on the forearm and allowing the tissues to heal over supportive stents before transferring the flap. In similarly advanced clinical scenarios, surgeons have used mesh trays to fashion morselized bone chips in the shape of craniofacial bones, and even employed calcium-based scaffolds along with adipose stem cells and growth factors to generate vascularized bone segments for clinical reconstruction. In essence, surgeons are applying tissue engineering concepts in real time in the operating room. From a practical standpoint, surgeons have a wide array of building blocks to work with in clinical reconstructive procedures today, including a broad range of tissues in the body that can be grafted, a number of approved biomaterials readily available in the operating room, approved growth factors such as bone morphogenic protein and plateletderived growth factor, and fibrin glue to serve as a biologic bonding agent. As the limits of technology and technique are being pushed forward, a surgeon has the capability to harvest autologous tissue during a surgical procedure, isolate cellular elements or other tissue components, seed the tissue onto a scaffold that is approved for implantation, and enrich the construct with growth factors that are readily available in the operating room. Given this expansive pallet of materials available to the surgeon to work with in the operating room, where do the boundaries of standard clinical care lie when it comes to removing and implanting tissues? The answer is found in the United States Code of Federal Regulations Section 21, part 1271 (21 CFR 1271), HUMAN CELLS, TISSUES, AND CELLULAR AND TISSUE-BASED PRODUCTS. This specific code of federal regulations was written by the food and drug administration (FDA) under authority granted by Section 361 of the Public Health Service Act, which empowers the agency to control the spread of communicable diseases. While many surgeons are under the impression that they are free from FDA regulations when performing procedures that involve autologous tissue grafting and that they are simply practicing medicine, 21 CFR 1271 gives the FDA regulatory