Smoothened-antagonists reverse homogentisic acid-induced alterations of Hedgehog signaling and primary cilium length in alkaptonuria.

Alkaptonuria (AKU) is an ultra-rare genetic disease, in which the accumulation of a toxic metabolite, homogentisic acid (HGA) leads to the systemic development of ochronotic aggregates. These aggregates cause severe complications mainly at the level of joints with extensive degradation of the articular cartilage. Primary cilia have been demonstrated to play an essential role in development and the maintenance of articular cartilage homeostasis, through their involvement in mechanosignaling and Hedgehog signaling pathways. Hedgehog signaling has been demonstrated to be activated in osteoarthritis (OA) and to drive cartilage degeneration in vivo. The numerous similarities between OA and AKU suggest that primary cilia Hedgehog signaling may also be altered in AKU. Thus, we characterized an AKU cellular model in which healthy chondrocytes were treated with HGA (66 µM) to replicate AKU cartilage pathology. We investigated the degree of activation of the Hedgehog signaling pathway and how treatment with inhibitors of the receptor Smoothened (Smo) influenced Hedgehog activation and primary cilia structure. The results obtained in this work provide a further step in the comprehension of the pathophysiological features of AKU, suggesting a potential therapeutic approach to modulate AKU cartilage degradation processes through manipulation of the Hedgehog pathway.

Corneal and Scleral Problems Caused by Skin-Lightening Creams.

PURPOSE: To present a case series of patients with corneal and scleral changes associated with the use of skin-lightening creams. This is the first report of corneal changes with these widely available creams. METHODS: Three patients of West African origin presented with strikingly similar skin, corneal, and scleral changes and were found to have all been using skin-lightening creams containing hydroquinone. Histopathology was obtained for 1 patient. RESULTS: Three patients were referred to the corneal clinics of 2 hospitals with corneal changes and a history of blurred vision for 1 to 3 years. There was a 60-year-old woman from Nigeria and a 68-year-old woman and a 73-year-old man both from Ghana. All 3 had been using skin-lightening lotions containing hydroquinone on their faces for between 3 and 15 years and had black-blue facial pigmentation of exogenous ochronosis, a recognized complication of these creams. Their corneas all had horizontal striae radiating across the posterior corneas with scleral thinning and plaques. Linear brown epithelial pigmentation was observed within the lower third of the corneas. Biopsy of the sclera in 1 patient showed ochronosis. CONCLUSIONS: We present previously unreported eye changes associated with the use of skin-lightening creams containing hydroquinone, with a triad of signs: posterior corneal striae radiating from 3 o'clock to 9 o'clock, thinning and plaques in the sclera, and a normal endothelial cell count. Similar pathological changes are seen in exogenous ochronosis, a recognized skin complication of hydroquinone, are seen in the sclera.