What is the role of sirolimus in the treatment of keloids and hypertrophic scars?

Updated: Jun 12, 2018
  • Author: Brian Berman, MD, PhD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Sirolimus is an inhibitor of the mammalian target of rapamycin (mTOR), a serine/threonine kinase that regulates collagen expression. By inhibiting mTOR, sirolimus blocks the response to IL-2 and decreases ECM deposition. [54] Similar to rapamycin, sirolimus inhibits Gli -1 signal transduction. mTOR kinases form 2 distinct multiprotein complexes, mTORC1 and mTORC2. In an in vitro and ex vivo study, 2 compounds, KU-0063794 and KU-0068650, were demonstrated to be potent and highly selective competitive inhibitors of mTORC1 and mTORC2 compared with rapamycin, which inhibits mTORC1 alone. The compounds have shown promising antifibrotic activity, with apparent no toxicity in vivo. [55]

A higher concentration of VEGF and higher blood vessel density has been found in the basal layer of the epidermis of keloidal tissue in comparison to normal skin. In co-cultured keloid keratinocytes and fibroblasts exposed to sirolimus, VEGF expression has shown to be down-regulated in a dose-dependent manner. Through inhibition of VEGF, sirolimus may control the expression profile of underlying dermal fibroblasts.


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