Metformin and Inhibition of Transforming Growth Factor-Beta Stimulate In Vitro Transport in Primary Renal Tubule Cells.

Patient-oriented applications of cell culture include cell therapy of organ failure like chronic renal failure. Clinical deployment of a cell-based device for artificial renal replacement requires qualitative and quantitative fidelity of a cultured cell to its in vivo counterpart. Active specific apicobasal ion transport reabsorbs 90-99% of the filtered load of salt and water in the kidney. In a bioengineered kidney, tubular transport concentrates wastes and eliminates the need for hemodialysis, but renal tubule cells in culture transport little or no salt and water. We previously identified transforming growth factor-beta as a signaling pathway necessary for in vitro differentiation of renal tubule cells. Inhibition of TGF-β receptor-1 led to active inhabitable electrolyte and water transport by primary human renal tubule epithelial cells in vitro. Addition of metformin increased transport, in the context of a transient effect on 5' AMP-activated kinase phosphorylation. The signals that undermine in vitro differentiation are complex, but susceptible to pharmacologic intervention. This achievement overcomes a major hurdle limiting the development of a bioreactor of cultured cells for renal replacement therapy that encompasses not only endocrine and metabolic functions but also transport and excretion. Impact statement Clinical tissue engineering requires functional fidelity of the cultured cell to its in vivo counterpart, but this has been elusive in renal tissue engineering. Typically, renal tubule cells in culture have a flattened morphology and do not express key transporters essential to their function. In this study, we build on our prior work by using small molecules to modulate pathways affected by substrate elasticity. In doing so, we are able to enhance differentiation of these cells on conventional noncompliant substrates and show transport. These results are fundamentally enabling a new generation of cell-based renal therapies.