Histone Variants as Stem Cell Biomarkers for Long‐Term Injection Medialization Laryngoplasty

OBJECTIVES/HYPOTHESIS: Vocal fold (VF) paralysis by sectioning the recurrent laryngeal nerve dramatically impacts the life of thyroidectomy patients. Volume-expanding materials can temporarily restore VF medialization. To prolong this benefit, adipose mesenchymal stem cells (ADSCs) and micronized acellular dermis (MACD) were co-injected in a rabbit model of injection medialization laryngoplasty. Biomarkers of in situ proliferation were identified by mass spectrometry proteomics and pathway analysis to guide future efforts to increase the length of benefit. METHODS: ADSCs were expanded and/or differentiated into chondrocytes (CHON) as collagen microspheres. After VF paralysis rabbits received MACD, MACD + undifferentiated ADSC, or MACD+CHON, ADSCs differentiated into chondrocytes. After 12 weeks, animals were sacrificed and 5-µm paraffin-embedded cryosections were prepared from larynges for hematoxylin and eosin visualization and nanoflow liquid chromatography electrospray-ionization tandem-mass spectrometry analysis of tissue collections. Validated proteins were processed by Venn subtraction and gene ontology (GO) overrepresentation analysis to identify unique pathways and biomarkers. RESULTS: Confirmed proteins numbered 147 (MACD), 1,243 (MACD+ADSC), and 1,033 (MACD+CHON). Totally, 333 proteins were uniquely found in the MACD+ADSC group, including mesenchymal surface markers CD9, CD44, fibronectin, and vimentin. Over 70% of proteins belonged to catalytic activity and binding GO categories, with the histone (H) family being overrepresented (P < 0.05). Histone variants H3.3, H2A.V, and H2A.Z (associated with open chromatin states) were overrepresented in the MACD+ADSC group, whereas structural histones H2A, H2B, and H4 were not. CONCLUSION: Biomarkers, including atypical histones, are associated with in vivo proliferation of ADSCs and an expanded VF medialization volume. LEVEL OF EVIDENCE: NA Laryngoscope, 128:E402-E408, 2018.