Differential Gene Expression In Young Patients Before And After Free Tissue Transfer For Parry Romberg Disease
Jacqueline S. Israel, MD, Rebecca L. Farmer, MD, PhD, Kirsten A. Gunderson, BS, Mark E. Berres, PhD, Samuel O. Poore, MD, PhD, John W. Siebert, MD.
University of Wisconsin - Madison, Madison, WI, USA.
Purpose: Parry Romberg disease is associated with progressive hemifacial atrophy, and its pathophysiology remains poorly understood. Surgical treatment options include free tissue transfer and serial fat grafting. We have previously shown that following free tissue transfer, gene expression in tissue obtained from the affected hemiface appears to resemble that obtained from the skin of healthy control patients. The purpose of this study was to evaluate differences in affected soft tissue gene expression in young patients with Parry Romberg before and after free tissue transfer, using each subjectís contralateral, unaffected tissue as an internal control.
Methods: Patients with active hemifacial atrophy underwent reconstruction with a free parascapular adipofascial flap. Revisions were performed in all patients 6 months following free tissue transfer. Preauricular skin samples were obtained from the affected hemiface at the time of free tissue transfer (stage 1), and at the time of revision (stage 2). Each subject was their own control, using preauricular samples from the unaffected hemiface. Following RNA extraction, sequencing was performed using Illumina HiSeq. Reads were mapped back to the genome and differentially expressed genes were identified. TargetMine software was used for KEGG pathway enrichment.
Results: Eight subjects were included, with ages ranging from 4 to 29 years (mean 12 years; 75% of patients were <12 years old). Sample quality was found to be improved compared our previous study that utilized control tissue from unaffected patients. For the 1,991 differentially expressed (DE) genes identified when stage 1 samples were compared to stage 2 (p<0.05), very high resolution was noted. Of the top 50 DE genes identified when stage 1 samples were compared to controls, more genes were noted to be upregulated than downregulated. When all three groups were compared, stage 2 samples more closely resembled the control group. Significant pathways amongst the DE genes included protein digestion, IL-17 and TNF signaling, and immune regulation.
Conclusion: This is the first study to use internal controls and compare molecular signatures of affected tissue in young patients with Parry Romberg disease before and after reconstruction with free tissue transfer. Results of this study support the use of free tissue transfer in young patients with active, progressive disease. We have identified several gene pathways for ongoing study. A multi-center study incorporating serial fat grating as a treatment option may allow for a more nuanced understanding of the pathophysiology of this disease process and the effects of treatment.
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