Cell and tissue models of alkaptonuria

Alkaptonuria (AKU) is a rare metabolic disease of historical and medical interest. Despite the identification of gene and protein defects leading to the accumulation of homogentisic acid (HGA), little is known on how HGA is transformed into an ochronotic pigment (the hallmark of the disease) leading to a range of clinical manifestations. Major obstacles in tackling the pathological features of AKU are the rarity of biological samples, the invasiveness of sampling techniques and the intrinsic difficulties of studying the pigmented tissues. This review provides an overview of the in vitro and ex vivo cell and tissue models that were recently developed and characterized to fill the above-mentioned gaps in the knowledge of AKU.