Transplantation of autologous chondrocytes seeded on a fibrin/hyaluronic acid composite gel into vocal fold in rabbits: Preliminary results

Investigation of the Clinical Potential of Polarization-Sensitive Optical Coherence Tomography in a Laryngeal Tumor Model

BACKGROUND

The vocal cord tissue consists of three anatomical layers from the surface to deep inside: the epithelium that contains almost no collagen, the lamina propria that is composed of abundant collagen, and the vocalis muscle layer. It is clinically important to visualize the tissue microstructure using a non-invasive method, especially in the case of vocal cord nodules or cancer, since histological changes in each layer of the vocal cord cause changes in the voice. Polarization-sensitive optical coherence tomography (PS-OCT) enables phase retardation measurement to evaluate birefringence of tissue with varied organization of collagen fibers in different tissue layers. Therefore, PS-OCT can visualize structural changes between normal and abnormal vocal cord tissue.

METHOD

A rabbit laryngeal tumor model with different stages of tumor progression was investigated ex-vivo by PS-OCT. A phase retardation slope-based analysis, which quantifies the birefringence in different layers, was conducted to distinguish the epithelium, lamina propria, and muscle layers.

RESULTS

The PS-OCT images showed a gradual decrease in birefringence from normal tissue to advanced tumor tissue. The quantitative analysis provided a more detailed comparison among different stages of the rabbit laryngeal tumor model, which was validated by the corresponding histological findings.

CONCLUSION

Differences in tissue birefringence was evaluated by PS-OCT phase retardation measurement. It is also possible to indirectly infer the dysplastic changes based on the mucosal and submucosal alterations.

Mechanically Reinforced Extracellular Matrix Scaffold for Application of Cartilage Tissue Engineering

Scaffolds with cartilage-like environment and suitable physical properties are critical for tissue-engineered cartilage repair. In this study, decellularized porcine cartilage-derived extracellular matrix (ECM) was utilized to fabricate ECM scaffolds. Mechanically reinforced ECM scaffolds were developed by combining salt-leaching and crosslinking for cartilage repair. The developed scaffolds were investigated with respect to their physicochemical properties and their cartilage tissue formation ability. The mechanically reinforced ECM scaffold showed similar mechanical strength to that of synthetic PLGA scaffold and expressed higher levels of cartilage-specific markers compared to those expressed by the ECM scaffold prepared by simple freeze-drying. These results demonstrated that the physical properties of ECM-derived scaffolds could be influenced by fabrication method, which provides suitable environments for the growth of chondrocytes. By extension, this study suggests a promising approach of natural biomaterials in cartilage tissue engineering.

Efficiency and durability of hyaluronic acid of different particle sizes as an injectable material for VF augmentation

CONCLUSION

The results of the present investigation suggest that modification of HA could improve efficiency and durability in augmentation laryngoplasty.

OBJECTIVES

Injection laryngoplasty (IL) is one of the most suitable options for treatment of glottic insufficiency, which is caused by vocal fold (VF) paralysis, atrophy, or scarring. Hyaluronic acid (HA) is a widely used material for VF injection. This study was intended to evaluate the durability and efficiency of HA of different particle sizes for VF augmentation.

METHODS

Three types of HA, Restylane®, monophasic low-viscosity, and unequal particle-sized middle-viscosity HA were injected into the left VF of three groups with eight rabbits each.

RESULTS

After 6 and 10 weeks, the injected site was evaluated endoscopically, histologically, radiologically, and functionally. None of the 24 rabbits showed any signs of respiratory distress. Computed tomography (CT) images and endoscopic evaluation revealed sufficient augmented volume of the injected VF in all treated groups 6 weeks after the injection. Histological data at week 10 showed that unequal particle-sized HA did not migrate from its original injection site, while other HAs migrated to the periphery of the arytenoid cartilage. Videokymographic analysis showed more favorable vibrations of unequal particle-sized HA injected VF mucosa 10 weeks post-injection, compared to the other treatment groups.

Tissue-engineered tracheal reconstruction using three-dimensionally printed artificial tracheal graft: preliminary report

Three-dimensional printing has come into the spotlight in the realm of tissue engineering. We intended to evaluate the plausibility of 3D-printed (3DP) scaffold coated with mesenchymal stem cells (MSCs) seeded in fibrin for the repair of partial tracheal defects. MSCs from rabbit bone marrow were expanded and cultured. A half-pipe-shaped 3DP polycaprolactone scaffold was coated with the MSCs seeded in fibrin. The half-pipe tracheal graft was implanted on a 10 × 10-mm artificial tracheal defect in four rabbits. Four and eight weeks after the operation, the reconstructed sites were evaluated bronchoscopically, radiologically, histologically, and functionally. None of the four rabbits showed any sign of respiratory distress. Endoscopic examination and computed tomography showed successful reconstruction of trachea without any collapse or blockage. The replaced tracheas were completely covered with regenerated respiratory mucosa. Histologic analysis showed that the implanted 3DP tracheal grafts were successfully integrated with the adjacent trachea without disruption or granulation tissue formation. Neo-cartilage formation inside the implanted graft was sufficient to maintain the patency of the reconstructed trachea. Scanning electron microscope examination confirmed the regeneration of the cilia, and beating frequency of regenerated cilia was not different from those of the normal adjacent mucosa. The shape and function of reconstructed trachea using 3DP scaffold coated with MSCs seeded in fibrin were restored successfully without any graft rejection.

Tissue-engineered tracheal reconstruction using chondrocyte seeded on a porcine cartilage-derived substance scaffold

OBJECTIVES

Tracheal reconstruction with tissue-engineering technique has come into the limelight in the realm of head and neck surgery. We intended to evaluate the plausibility of allogenic chondrocytes cultured with porcine cartilage-derived substance (PCS) scaffold for partial tracheal defect reconstruction.

METHODS

Powder made from crushed and decellularized porcine articular cartilage was formed as 5 mm × 12 mm (height × diameter) scaffold. Chondrocytes from rabbit articular cartilage were expanded and cultured with PCS scaffold. After 7 weeks culture, the scaffolds were implanted on a 5 mm × 10 mm artificial tracheal defect in six rabbits. Two, four and eight weeks postoperatively, the sites were evaluated endoscopically, radiologically, histologically and functionally.

RESULTS

None of the six rabbits showed any sign of respiratory distress. Endoscopic examination did not show any collapse or blockage of the reconstructed trachea and the defects were completely covered with regenerated respiratory epithelium. Computed tomography showed good luminal contour of trachea. Postoperative histologic data showed that the implanted chondrocyte successfully formed neo-cartilage with minimal inflammatory response and granulation tissue. Ciliary beat frequency of regenerated epithelium was similar to those of normal adjacent mucosa.

CONCLUSIONS

The shape and function of reconstructed trachea using allogenic chondrocytes cultured with PCS scaffold was restored successfully without any graft rejection.

In Vivo Osteogenic Differentiation of Human Embryoid Bodies in an Injectable in Situ-Forming Hydrogel

In this study, we examined the in vivo osteogenic differentiation of human embryoid bodies (hEBs) by using an injectable in situ-forming hydrogel. A solution containing MPEG-b-(polycaprolactone-ran-polylactide) (MCL) and hEBs was easily prepared at room temperature. The MCL solution with hEBs and osteogenic factors was injected into nude mice and developed into in situ-forming hydrogels at the injection sites; these hydrogels maintained their shape even after 12 weeks in vivo, thereby indicating that the in situ-forming MCL hydrogel was a suitable scaffold for hEBs. The in vivo osteogenic differentiation was observed only in the in situ gel-forming MCL hydrogel in the presence of hEBs and osteogenic factors. In conclusion, this preliminary study suggests that hEBs and osteogenic factors embedded in an in situ-forming MCL hydrogel may provide numerous benefits as a noninvasive alternative for allogeneic tissue engineering applications.