Efficacy of vocal cord injection of dedifferentiated fat cells in treating glottis closure insufficiency: Insights from a rat model of recurrent laryngeal nerve resection

Glottic insufficiency results from impaired vocal cord contact, leading to a gap between the cords and manifesting as hoarseness and respiratory difficulties. Vocal cord injection is a commonly utilized therapeutic approach to rectify this gap by augmenting vocal cord volume; however, the optimal injectable material remains undetermined. Dedifferentiated fat cells (DFATs), derived from mature adipocytes, exhibit robust proliferative capacity and multipotency, establishing them as potential candidates for treating glottic insufficiency. This study investigated the therapeutic efficacy of DFATs in a rat model of recurrent laryngeal nerve paralysis. In the experimental design, the recurrent laryngeal nerve of each rat was resected unilaterally, and 5 weeks later, the atrophied vocal cord muscles were injected with either 10 μl of saline (control), 1.0 × 10 ⁶ DFATs in 10 μl (DFAT group), or 1.0 × 10 ⁶ DFATs combined with 500 ng of basic fibroblast growth factor (bFGF) in 10 μl (DFAT + bFGF group). At 4 weeks post-injection, laryngeal endoscopy was performed to evaluate the glottic gap, followed by histological analyses to assess vocal muscle atrophy, collagen deposition, and markers of cellular proliferation (Ki-67) and apoptosis (TUNEL). To confirm DFAT engraftment, GFP-labeled DFATs were evaluated at 2, 4, and 6 weeks post-injection. Results indicated that both the DFAT and DFAT + bFGF groups exhibited significantly reduced glottic gaps, increased collagen deposition, and decreased TUNEL-positive apoptotic cells compared to controls. Notably, the DFAT + bFGF group displayed superior outcomes, including a greater vocal muscle area and enhanced Ki-67-positive cell proliferation, indicating mitigation of muscle atrophy. GFP-positive DFATs were detectable in the tissue for up to 6 weeks, confirming engraftment. These findings underscore the potential of DFATs, particularly in combination with bFGF, as an innovative and effective therapeutic approach for glottic insufficiency secondary to recurrent laryngeal nerve paralysis.