Craniofacial Tissue Engineering

Abstract

The craniofacial complex is composed of fundamental components such as blood vessels and nerves, and also a variety of specialized tissues such as craniofacial bones, cartilages, muscles, ligaments, and the highly specialized and unique organs, the teeth. Together, these structures provide many functions including speech, mastication, and aesthetics of the craniofacial complex. Craniofacial defects not only influence the structure and function of the jaws and face, but may also result in deleterious psychosocial issues, emphasizing the need for rapid and effective, precise, and aesthetic reconstruction of craniofacial tissues. In a broad sense, craniofacial tissue reconstructions share many of the same issues as noncraniofacial tissue reconstructions. Therefore, many concepts and therapies for general tissue engineering can and have been used for craniofacial tissue regeneration. Still, repair of craniofacial defects presents unique challenges, mainly because of their complex and unique 3D geometry.

Figure 1.

Schematic of the layered structure of craniofacial tissues. The skull and craniofacial bones provide the structural support for the muscle, vascular network, and skin (from catalog.biodigital.com/storeImages/detail/cranio_dvd.jpg).

Figure 2.

Components of inkjet, microextrusion, and laser-assisted bioprinters. (A) Thermal inkjet printers electrically heat the printhead to produce air-pressure pulses that force droplets from the nozzle, whereas acoustic printers use pulses formed by piezoelectric or ultrasound pressure. (B) Microextrusion printers use pneumatic or mechanical (piston or screw) dispensing systems to extrude continuous beads of material and/or cells. (C) Laser-assisted printers use lasers focused on an absorbing substrate to generate pressures that propel cell-containing materials onto a collector substrate. (From Murphy and Atala 2014; adapted, with permission, from Nature Publishing Group © 2014.)

Figure 3.

Composite bone–tooth constructs. (A) Tooth scaffolds composed of a dental mesenchymal (DM) cell seeded polyglycolide/poly-l-lactide (PGA/PLLA) scaffold sphere to mimic the dental papilla, and a dental epithelial (DE) cell seeded gelfoam strip to mimic the enamel organ. (B) Lattice bone scaffolds made by poly-dl-lactic-co-glycolic acid (PLGA), seeded with iliac crest–derived mesenchymal stem cells (MSCs) and grown in the rotational oxygen-permeable bioreactor system (ROBS) for 6 weeks. (C) Fabricated tooth–bone construct seeded with cells before implantation. (D) Surgical implant site before wound closure. (E) Bioengineered dental tissues that closely resembled those of naturally formed pig tooth tissues surrounded by alveolar bone. Scale bar = 100 µm. b, bone; bm, bone marrow; d, dentin; e, enamel; p, pulp; pdl, periodontal ligament.