Prenatal Tracheal Repair with Cartilage Engineered from Amniotic Mesenchymal Stem Cells in an Allogeneic Ovine Model
Christopher G. Turner, MD, Shaun M. Kunisaki, MD, Justin D. Klein, MD, Deborah Freedman, MD, Dario O. Fauza, MD
Children’s Hospital Boston, Boston, MA
PURPOSE OF STUDY
The treatment of severe tracheal anomalies remains fundamentally unsolved. This study was aimed at determining whether cartilaginous grafts engineered from an easily accessible cell source, namely the amniotic fluid, could be employed in fetal tracheal repair.
Ovine mesenchymal amniocytes were expanded in culture, labeled with green fluorescent protein (GFP), and dynamically seeded onto polyglycolic acid scaffold tubes. Constructs were maintained under hydrodynamic stimulation in serum-free medium supplemented with transforming growth factor beta and insulin growth factor for 24-30 weeks, after which chondrogenic differentiation was confirmed. Grafts were then used to repair partial or full circumferential defects spanning 4-5 tracheal rings in allogeneic fetal lambs (n=7). Normal delivery was allowed 4-5 weeks postoperatively. Newborns were evaluated for signs of airway compromise. Implants were harvested over a 10-day period for multiple analyses. Statistical analysis was by the paired t-test (P<.05).
SUMMARY OF RESULTS
All 5 lambs that survived to term were able to breathe spontaneously at birth, 4 (80%) of them without stridor. However, variable degrees of stridor did develop over time in all but one animal. Mild to moderate tracheal stenosis at the level of the repair was present in all specimens. Histologically, all grafts contained GFP-positive cells, had a pseudo-columnar epithelium, and remodeled into a predominantly fibrous cartilage pattern. Quantitatively, implants showed no significant changes in glycosaminoglycan, collagen, and elastin contents at harvest.
Engineered cartilaginous grafts derived from mesenchymal amniocytes are a viable alternative for tracheal repair. The amniotic fluid is a practical cell source for engineered tracheal reconstruction.