Clin Exp Otorhinolaryngol.  2013 Jun;6(2):82-89.

Viability and Regeneration of Chondrocytes after Laser Cartilage Reshaping Using 1,460 nm Diode Laser

• Mo JH
• Kim JS
• Lee JW
• Chung PS
• Chung YJ

Abstract

OBJECTIVES
Cartilage reshaping by laser irradiation is used to correct septal and auricular cartilage deformities. Chondrocyte viability following laser irradiation and reshaping has been well established. However, the regeneration process of chondrocyte after laser irradiation has not been revealed yet. The aims of this study were to determine the mechanism of cartilaginous thermal injury and the regenerative process of damaged cartilage following laser irradiation.
METHODS
Laser irradiation was performed on human septal cartilage and rabbit auricular cartilage using a 1,460-nm diode laser. We observed change in the shape of cartilage and evaluated the extent of cartilage injury using live/dead cell assay via confocal microscopy. Hoechst and propidium iodide (PI) staining was used to evaluate the mechanism of chondrocyte injury after laser irradiation. To evaluate the regeneration of cartilage, laser irradiated cartilages were reimplanted into a subperichondrial pocket and were harvested at 1, 2, and 4 weeks after reimplantation for viability assessment and histologic examination.
RESULTS
Laser irradiation using a 1,460-nm diode laser produced a marked shape change in both human septal and rabbit auricular cartilages. Thermal damage on cartilage was correlated with the exposure time and the laser power. Hoechst and PI staining showed that chondrocyte death by laser irradiation was due to mainly necrosis, rather than apoptosis. In lower power treatment group (0.3 W and 0.5 W), all the chondrocytes regenerated within 4 weeks, however, in 1 W treatment group, chondrocytes could not regenerate until 4 weeks.
CONCLUSION
Reshaping of cartilage using 1,460 nm diode laser was attained concurrently with the thermal injury to the chondrocytes. The extent of thermal damage on chondrocytes was dependent on the exposure time and the laser power and the damaged chondrocytes irradiated with lower level of laser power could be regenerated after reimplantation into subperichondrial pocket.

Keyword

Laser; Reshaping; Diode laser; Chondrocyte; Cartilage; Septoplasty

MeSH Terms

Apoptosis
Cartilage
Chondrocytes
Congenital Abnormalities
Ear Cartilage
Humans
Lasers, Semiconductor
Microscopy, Confocal
Necrosis
Propidium
Regeneration
Replantation
Propidium

Figure

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  Fig. 1 Schematic illustration of experimental protocol. (A) Experimental protocol of human septal cartilage (B) experimental protocol of rabbit auricular cartilage.

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  Fig. 2 Shape change of human septal cartilage before (A), immediately after (B) diode laser irradiation. The cartilage was bent by laser irradiation. Reshaped cartilage was recovered into flat shape after re-irradiation by laser to the convex side (C). Red arrow indicates the direction of laser irradiation.

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  Fig. 3 Confocal images of live/dead assay of the human septal cartilage after (A) spot-pattern laser irradiation and (B) linear pattern laser irradiation. Cartilage was irradiated with different laser power (0.5-2.0 W) and exposure time (5-20 seconds). The green and red fluorescence indicates live and dead cell respectively. The extent of damaged area increased with the increase of the laser power and exposure time irrespective of exposure pattern. Average depth and width of thermal injury following laser cartilage reshaping (human) is plotted in graphs, showing linear increase of damaged depth and width with increase in power and exposure time.

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  Fig. 4 (A) Confocal images of live/dead assay of the cartilage injury after laser irradiation in rabbit auricular cartilage. Cartilage was irradiated with laser power of 0.3 W, 0.5 W, and 1.0 W for 5 seconds. The extent of damaged area increased with increase in laser power (0.3-1.0 W). (B) Hoechst & PI staining imaging of rabbit auricular cartilage following laser irradiation (laser power, 0.3-1.0 W; exposure time, 5 seconds). Blue and red stained cell indicates live and necrotic cell, respectively. This image shows that thermal injury of chondrocytes resulted in necrosis of chondrocytes rather than apoptosis.

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  Fig. 5 Regeneration of rabbit cartilage after thermal injury. (A) Confocal images of live/dead assay show that chondrocytes exhibited necrotic changes immediately after laser irradiation, irrespective of laser power. The chondrocytes in 0.3 W and 0.5 W treatment group regenerated completely and those in 0.3 W treatment group showed earlier regeneration. Chondrocytes in 1 W treatment group could not regenerate until 4 weeks after reimplantation. (B) Change of live/dead chondrocyte proportion in irradiated rabbit after reimplantation. (C) Histologic cross sections of laser-irradiated specimens of rabbit cartilage revealed loss of chondrocytes and condensation of nucleus (H&E, ×200).

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