Corneal stromal cells from patients with keratoconus exhibit alterations in the ESCRT-dependent machinery responsible for multivesicular body formation.

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Previous studies have reported that exosomes produced by corneal stromal cells from keratoconus patients exhibit a molecular content distinct from those produced by cells from healthy donors. This study investigates differences in the expression of ESCRT components, regarded as the most critical mechanism in exosome biogenesis. The study included analysis of transcription levels of system-encoding genes using qRT-PCR reactions, as well as semiquantitative protein determination through immunocytochemistry. Of the 34 molecules analyzed, mRNA downregulation was observed in 8 in pathological cells. In keratoconus, genes encoding STAM2 from the ESCRT-0 complex and VPS37A, VPS37C, VPS37D and UBAP1 from the ESCRT-I complex were found to be underexpressed, although VPS37D could not be confirmed at the protein level. Additionally, two other expression alterations affected the ESCRT-III complex, involving the core protein CHMP4C and the regulatory protein CHMP1B. Finally, deregulation of the ubiquitin-specific peptidase UBPY was observed. Most changes identified in this study affected specific isoforms, which could suggest functional diversification and differences in cargo recognition in the context of pathology. Altogether, these findings suggest that the previously reported alteration in the molecular content of exosomes produced by stromal cells in keratoconus may be, at least partially, due to disruptions in the exosome synthesis machinery.