Keratinocyte Proliferation Correlates With The Extent Of Scar Formation
Hui Li1, Swathi Balaji1, Xinyi Wang1, Paul Bollyky2, Manish Butte3, Sundeep Keswani1.
1Baylor College of Medicine, Houston, TX, USA, 2Stanford University, Palo Alto, CA, USA, 3UCLA, Los Angeles, CA, USA.
Background: Postnatal wound healing leads to scar formation, however, there is variability in scarring extent among individuals after similar injuries. Underlying mechanisms that determine the scar phenotype in healthy adults remain unknown. We determined cellular differences between healthy patients exhibiting low or high scar-forming responses. Methods: We obtained skin samples from female patients undergoing abdominoplasty to remove cesarean scars and compared keratinocytes from scar tissue against those from matched normal skin. The Vancouver Scar Scale was used to classify patients into low (score 1-3) and high (score 6-9) scar-forming groups. Formalin fixed paraffin embedded tissue sections were analyzed by immunohistochemistry using the cell proliferation marker Ki67. Moreover, keratinocytes were dissected from frozen tissue sections by Laser Microdissection (LMD) to quantitate Ki67 mRNA by qRT-PCR. Results: We analyzed a pilot sample of n=3 low scar and n=3 high scar-forming tissues from our biobank. Immunohistochemical analysis showed that low scar-forming patients had 3.8-fold more proliferating keratinocytes in their normal skin than high scar patients (12%+/-2.6 vs. 3.17%+/-2.1 Ki67+ cells in the epidermis). qRT-PCR analysis showed that Ki67 expression in control skin of high scar-forming patients was 0.54-fold lower than low scar-forming patients. Comparing scar keratinocytes versus matched control skin keratinocytes, we observed a 0.45- and 0.43-fold decrease in Ki67 expression in low and high scar-forming patients, respectively. Conclusions: These data reveal differences in keratinocyte proliferation among patients with different scarring phenotypes, suggesting that keratinocyte proliferation may inversely affect the individual propensity for scar formation, mediated through their roles in wound closure and ECM production during wound healing.
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