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Decreased Colony Forming Capacity in Mesenchymal Stem Cells Derived from Irradiated Human Skin
Maxwell Johnson, M.S., Soleil Niknam-Bienia, M.D., Xingtian Xu, Ph.D., Vinaya Soundararajan, B.S., Daniel Gardner, M.S., Regina Y. Baker, M.D., Alex K. Wong, MD.
Keck School of Medicine of USC, Los Angeles, CA, USA.

PURPOSE:Radiotherapy results in increased complications during post-oncologic reconstructive surgery. Skin-derived mesenchymal stem cells (SMSCs) are critically involved in skin homeostasis, but little is known about the in situ effect of irradiation on these cells. This study aimed to characterize functional alterations in SMSCs derived from irradiated and normal human skin.
METHODS:Four pairs of irradiated and normal human skin samples were harvested from patients. SMSCs were isolated from these samples and cultured according to standard protocol. SMSC function was assessed using a colony forming unit (CFU) assay. Gene expression was evaluated using RNA-Seq and confirmed with quantitative polymerase chain reaction (qPCR).
RESULTS:SMSCs from irradiated skin had a 5.6-fold decrease in colony formation capacity (p < 0.05). Analysis of RNA-Seq data was restricted to genes with reads per kilobase of transcript per million mapped reads (RPKM) greater than 0.3. Eleven genes were differentially expressed in irradiated SMSCs (p < 0.05). Three candidate genes—DACT1, FMN1, and IL32—were selected on the basis of their involvement in skin function or pathology, and the directionality of their differential expression confirmed with qPCR.
CONCLUSION:SMSCs from irradiated skin have significant defects in colony formation in vitro that are associated with a distinct pattern of altered gene expression. The investigation of these differentially expressed genes may aid in the development of targeted therapies to improve skin healing after radiotherapy.


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