Inhibition of Fibrotic Contraction by Sirolimus (Rapamycin) in an Ex Vivo Model of Thyroid Eye Disease.
Ophthalmic Plast Reconstr Surg 2021;
37:366-371. [PMID:
33237667 DOI:
10.1097/iop.0000000000001876]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND
Thyroid eye disease (TED) is characterized by orbital inflammation and complicated by extraocular muscle fibrosis. Treatment with rapamycin/sirolimus has been reported to improve ocular motility and disease manifestations in TED. Whether this resulted from a primary antifibrotic effect on fibroblasts or was secondary to immune-suppression is unclear.
METHODS
In vitro contractility studies of primary orbital fibroblasts. Cells from patients with TED and controls were treated with rapamycin [mechanistic target of rapamycin an (mTOR) inhibitor] and MHY1485 (an mTOR stimulator) as well as inhibitors upstream in the same signaling cascade (saracatinib and befatinib).
RESULTS
At concentrations consistent with the therapeutic dosing range in humans, rapamycin/sirolimus significantly reduces fibrosis in orbital fibroblasts from TED patients and controls in vitro. This effect is separate from, and in addition to, its immune suppressive effect. mTOR-driven fibrotic activity is greater in TED-derived fibroblasts and can be blocked also upstream of mTOR by inhibition of src. There was no adverse effect on cell survival.
CONCLUSION
The authors present evidence for a direct antifibrotic effect of rapamycin/sirolimus in primary orbital fibroblasts. Targeting mTOR signaling presents a further and adjunctive treatment of TED alongside other immune-suppressive agents. By acting downstream of IGF1-R, sirolimus may offer a cost-effective alternative to teprotumumab therapy. Clinical case reports, now supplemented by this in vitro evidence, support the initiation of a clinical trial to treat the fibrotic sequelae of TED with this already-approved agent. Such an "off-the-shelf" therapy is a welcome prospect for TED treatment, particularly one available at a low price.
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