Tissue specific ablation of Enpp1 (and possibly Ank) could help determine in future studies whether PPi is produced renally or extrarenally. Injection of recombinant Enpp1 may be able to reduce the renal calcifications in Npt2a-/- mice [26, 29] and provide further evidence of the causal relationship of this extracellular enzyme, urine PPi, and renal mineralization.