Extracellular and intracellular inorganic pyrophosphates in ATDC5 cells transduced with wild-type vector before clonal selection. Cells were assayed at day 14 of chondrogenesis. (a) Consistent with previous reports of the impact of overexpression of ank on levels of intracellular inorganic pyrophosphate (iPPi) and extracellular inorganic pyrophosphate (ePPi), cells transduced with wild-type (WT) ank demonstrate a decrease in levels of iPPi when compared with cells transduced with pLNCX empty vector or with untransduced ATDC5 cells. (b) Concomitantly, cells transduced with WT ank exhibit an increase in ePPi levels when compared with cells transduced with pLNCX vector only (empty) or with untransduced ATDC5 cells. n = 6; *P ≤ 0.05. PPi, inorganic pyrophosphate.