Engineering of Tracheal Grafts Based on Recellularization of Laser-Engraved Human Airway Cartilage Substrates

OBJECTIVE

Implantation of tissue-engineered tracheal grafts represents a visionary strategy for the reconstruction of tracheal wall defects after resections and may develop into a last chance for a number of patients with severe cicatricial stenosis. The use of a decellularized tracheal substrate would offer an ideally stiff graft, but the matrix density would challenge efficient remodeling into a living cartilage. In this study, we hypothesized that the pores of decellularized laser-perforated tracheal cartilage (LPTC) tissues can be colonized by adult nasal chondrocytes (NCs) to produce new cartilage tissue suitable for the repair of tracheal defects.

DESIGN

Human, native tracheal specimens, isolated from cadaveric donors, were exposed to decellularized and laser engraving-controlled superficial perforation (300 μm depth). Human or rabbit NCs were cultured on the LPTCs for 1 week. The resulting revitalized tissues were implanted ectopically in nude mice or orthotopically in tracheal wall defects in rabbits. Tissues were assayed histologically and by microtomography analyses before and after implantation.

RESULTS

NCs were able to efficiently colonize the pores of the LPTCs. The extent of colonization (i.e., percentage of viable cells spanning >300 μm of tissue depth), cell morphology, and cartilage matrix deposition improved once the revitalized constructs were implanted ectopically in nude mice. LPTCs could be successfully grafted onto the tracheal wall of rabbits without any evidence of dislocation or tracheal stenosis, 8 weeks after implantation. Rabbit NCs, within the LPTCs, actively produced new cartilage matrix.

CONCLUSION

Implantation of NC-revitalized LPTCs represents a feasible strategy for the repair of tracheal wall defects.

Stable Tracheal Regeneration Using Organotypically Cultured Tissue Composed of Autologous Chondrocytes and Epithelial Cells in Beagles

OBJECTIVES

In tracheal regeneration, the slow process of epithelialization is often a barrier to the stability and safety of the transplanted trachea. The aim of this study was to examine a new tracheal regeneration technique using organotypically cultured tissue composed of autologous cells.

METHODS

Nine beagles were prepared. Chondrocytes from auricular cartilage and epithelial cells from buccal mucosa were isolated and cultured. Tissue-engineered cartilages were fabricated with chondrocytes at a density of 1 × 10⁷ cells/mL (high-density group) and 1 × 10⁶ cells/mL (low-density group). A fabricated epithelial cell sheet was laid on a poly(lactic-co-glycolic acid) block in atelocollagen gel containing the chondrocytes, and the organotypically cultured tissues were transplanted into a partially resected trachea. The control group had only the block transplanted.

RESULTS

The tissue-engineered cartilages in the high-density group contained many viable chondrocytes and many cartilage matrices. The low-density group had abundant collagen fibers and no chondrocytes. Tracheal endoscopy revealed no deformation or atrophy at the transplant site in the high-density group. Histologically, partially hyaline cartilages covered with epithelium and lamina propria were found in the high-density group but not in the low-density and control groups.

CONCLUSIONS

Stable tracheal regeneration was achieved using organotypically cultured tissue fabricated with autologous high-density chondrocytes and epithelial cells.

Expression of keratinocyte growth factor and its receptor in rat tracheal cartilage: possible involvement in wound healing of the damaged cartilage

Keratinocyte growth factor (KGF) is involved in the development and regeneration of a variety of tissues. To clarify the role of KGF in cartilage wound healing, we examined the expression of KGF and its receptor (KGFR) immunohistochemically in the wound healing area of rat tracheal cartilage, and the direct effect of recombinant KGF on the proliferation and differentiation of primary cultures of rat chondrocytes. KGF was found in the cytoplasm of both chondrocytes and perichondrial cells. On the other hand, KGFR was detected only in the plasma membrane of chondrocytes. Although the expression of KGF was similar in the cartilage and perichondrial area before and after injury, KGFR expression was induced after injury and limited to proliferating chondrocytes. The staining pattern of KGF and KGFR was same in the mature and the immature rat tracheal cartilage. Moreover, in vitro experiments using primary cultured chondrocytes revealed that KGF at 200 ng/ml significantly increased the number of chondrocytes (~1.5-fold), and significantly reduced acid mucopolysaccharide production. These results indicate that KGF stimulates chondrocyte proliferation, suggesting that KGF could therapeutically modulate the wound healing process in the tracheal cartilage.