Muscle tissue engineering for partial glossectomy defects.

BACKGROUND Tongue reconstruction represents a difficult reconstructive problem, based on the tongue's complex multimodality function. Existing methods of tongue reconstruction often result in significant deficits in speech and deglutition. A functional neotongue requires adequate soft tissue bulk and restoration of coordinated muscle function. Tissue engineering, a scientific approach that allows introduction of isolated cell populations of interest within 3-dimensional polymer scaffolds to create new tissue, may allow the generation of more highly functional tissue in tongue reconstruction. OBJECTIVES To apply muscle-tissue engineering techniques in the reconstruction of partial glossectomy defects in rats, and to compare the gross and histological nature of tissue found after reconstruction of the hemiglossectomy defect with acellular vs tissue-engineered composite material. MATERIALS AND METHODS Thirty mature Lewis rats underwent a left-sided mucosa-sparing partial glossectomy. The defects were then filled with 1 of the following 3 substances: isotonic sodium chloride solution, a collagen-rich hydrogel, or hydrogel containing a suspension of neonatal myoblasts from syngeneic rats. The animals were killed after 6 weeks and the tongues were harvested. The control and operated-on tongue halves were evaluated for weight differences and histological features. RESULTS The group receiving the hydrogel-myoblast composite injections demonstrated a statistically significant increase in tongue weight of the operated-on side compared with the control side. In contrast, the isotonic sodium chloride solution and hydrogel groups demonstrated loss of tongue weight. These findings correlated with the results of the histological evaluation. Hemitongues from the composite group demonstrated formation of new tissue with areas of musclelike tissue extending from islands of residual hydrogel, and we found evidence of neovascularization and possible neurotization. In contrast, the isotonic sodium chloride solution group exhibited dense fibrous scar with loss of muscle architecture and dramatic loss of tongue volume. The hydrogel group demonstrated preservation of tongue volume with persistent islands of gel, but no clear evidence of new tissue formation. CONCLUSIONS The introduction of a hydrogel into the rat hemiglossectomy pocket appears to promote volume preservation and/or muscle regeneration. The addition of myoblasts suspended in collagen gel supports the development of new tissue that preserves weight and volume after hemiglossectomy and may possess muscle properties similar to the tissue desired. This tissue-engineering approach represents a promising new strategy in tongue reconstruction and merits further investigation into the possible functional advantages it offers compared with current techniques.