TY - JOUR

T1 - Ochronotic osteoarthropathy in a mouse model of alkaptonuria, and its inhibition by nitisinone.

AU - Preston, Andrew J.

AU - Keenan, Craig M.

AU - Sutherland, Hazel

AU - Wilson, Peter J.

AU - Wlodarski, Brenda

AU - Taylor, Adam

AU - Williams, Dominic P.

AU - Ranganath, Lakshminarayan R.

AU - Gallagher, James A.

AU - Jarvis, Jonathan C.

PY - 2014/1

Y1 - 2014/1

N2 - BACKGROUND: Alkaptonuria (AKU) is a rare metabolic disease caused by deficiency of homogentisate 1,2 dioxygenase, an enzyme involved in tyrosine catabolism, resulting in increased circulating homogentisic acid (HGA). Over time HGA is progressively deposited as a polymer (termed ochronotic pigment) in collagenous tissues, especially the cartilages of weight bearing joints, leading to severe joint disease.OBJECTIVES: To characterise blood biochemistry and arthropathy in the AKU mouse model (Hgd-/-). To examine the therapeutic effect of long-term treatment with nitisinone, a potent inhibitor of the enzyme that produces HGA.METHODS: Lifetime levels of plasma HGA from AKU mice were measured by high-performance liquid chromatography (HPLC). Histological sections of the knee joint were examined for pigmentation. The effect of nitisinone treatment in both tissues was examined.RESULTS: Mean (±SE) plasma HGA levels were 3- to 4-fold higher (0.148±0.019 mM) than those recorded in human AKU. Chondrocyte pigmentation within the articular cartilage was first observed at 15 weeks, and found to increase steadily with mouse age. Nitisinone treatment reduced plasma HGA in AKU mice throughout their lifetime, and completely prevented pigment deposition.CONCLUSIONS: The AKU mouse was established as a model of both the plasma biochemistry of AKU and its associated arthropathy. Early-stage treatment of AKU patients with nitisinone could prevent the development of associated joint arthropathies. The cellular pathology of ochronosis in AKU mice is identical to that observed in early human ochronosis and thus is a model in which the early stages of joint pathology can be studied and novel interventions evaluated.

AB - BACKGROUND: Alkaptonuria (AKU) is a rare metabolic disease caused by deficiency of homogentisate 1,2 dioxygenase, an enzyme involved in tyrosine catabolism, resulting in increased circulating homogentisic acid (HGA). Over time HGA is progressively deposited as a polymer (termed ochronotic pigment) in collagenous tissues, especially the cartilages of weight bearing joints, leading to severe joint disease.OBJECTIVES: To characterise blood biochemistry and arthropathy in the AKU mouse model (Hgd-/-). To examine the therapeutic effect of long-term treatment with nitisinone, a potent inhibitor of the enzyme that produces HGA.METHODS: Lifetime levels of plasma HGA from AKU mice were measured by high-performance liquid chromatography (HPLC). Histological sections of the knee joint were examined for pigmentation. The effect of nitisinone treatment in both tissues was examined.RESULTS: Mean (±SE) plasma HGA levels were 3- to 4-fold higher (0.148±0.019 mM) than those recorded in human AKU. Chondrocyte pigmentation within the articular cartilage was first observed at 15 weeks, and found to increase steadily with mouse age. Nitisinone treatment reduced plasma HGA in AKU mice throughout their lifetime, and completely prevented pigment deposition.CONCLUSIONS: The AKU mouse was established as a model of both the plasma biochemistry of AKU and its associated arthropathy. Early-stage treatment of AKU patients with nitisinone could prevent the development of associated joint arthropathies. The cellular pathology of ochronosis in AKU mice is identical to that observed in early human ochronosis and thus is a model in which the early stages of joint pathology can be studied and novel interventions evaluated.

U2 - 10.1136/annrheumdis-2012-202878

DO - 10.1136/annrheumdis-2012-202878

M3 - Journal article

VL - 73

SP - 284

EP - 289

JO - Annals of the Rheumatic Diseases

JF - Annals of the Rheumatic Diseases

SN - 0003-4967

IS - 1

ER -