Mesenchymal stem cell energy deficit and oxidative stress contribute to osteopenia in the Pahenu2 classical PKU mouse.
Osteopenia occurs in a subset of phenylalanine hydroxylase (PAH) deficient phenylketonuria (PKU) patients. While osteopenia is not fully penetrant in patients, the Pahenu2 classical PKU mouse is universally osteopenic, making it an ideal model of the phenotype. Pahenu2 Phe management, with a Phe-fee amino acid defined diet, does not improve bone density as histomorphometry metrics remain indistinguishable from untreated animals. Previously, we demonstrated Pahenu2 mesenchymal stem cells (MSCs) display impaired osteoblast differentiation. Oxidative stress is recognized in PKU patients and PKU animal models. Pahenu2 MSCs experience oxidative stress determined by intracellular superoxide over-representation. The deleterious impact of oxidative stress on mitochondria is recognized. Oximetry applied to Pahenu2 MSCs identified mitochondrial stress by increased basal respiration with concurrently reduced maximal respiration and respiratory reserve. Proton leak secondary to mitochondrial complex 1 dysfunction is a recognized superoxide source. Respirometry applied to Pahenu2 MSCs, in the course of osteoblast differentiation, identified a partial complex 1 deficit. Pahenu2 MSCs treated with the antioxidant resveratrol demonstrated increased mitochondrial mass by MitoTracker green labeling. In hyperphenylalaninemic conditions, resveratrol increased in situ alkaline phosphatase activity suggesting partial recovery of Pahenu2 MSCs osteoblast differentiation. Up-regulation of oxidative energy production is required for osteoblasts differentiation. Our data suggests impaired Pahenu2 MSC developmental competence involves an energy deficit. We posit energy support and oxidative stress reduction will enable Pahenu2 MSC differentiation in the osteoblast lineage to subsequently increase bone density.
['Dobrowolski|Steven F|SF|', 'Sudano|Cayla|C|', 'Phua|Yu Leng|YL|', 'Tourkova|Irina L|IL|', 'Spridik|Kayla|K|', 'Goetzman|Eric S|ES|', 'Vockley|Jerry|J|', 'Blair|Harry C|HC|']
D000469:Alkaline Phosphatase D000818:Animals D015519:Bone Density D001851:Bone Diseases, Metabolic D002454:Cell Differentiation D004195:Disease Models, Animal D006801:Humans D059630:Mesenchymal Stem Cells D051379:Mice D010006:Osteoblasts D018384:Oxidative Stress D010649:Phenylalanine D010651:Phenylalanine Hydroxylase D010661:Phenylketonurias D000077185:Resveratrol
Oxidative stress Osteopenia Phenylketonuria Pah(enu2) Respiratory complex 1