Differentiation of smooth muscle cells from human amniotic mesenchymal cells implanted in the freeze-injured mouse urinary bladder.

Abstract

The multipotency of human amniotic mesenchymal cells (HAMCs) has been reported, but the role of HAMCs in urinary tract regeneration is unknown. The aim of the study was to determine if cells derived from HAMCs support the structural and functional reconstruction of freeze-injured mouse bladders. HAMCs were harvested from an amnion membrane, and cells were cultured for 7 d prior to injection into the freeze-injured bladder walls of nude mice. Three days prior to implantation, the posterior bladder walls were freeze injured for 30s. The cultured HAMC-derived cells (0.5 x 10(5) cells per 50 microl) were implanted into the injured regions. Control bladders received a cell-free injection. At 1, 2, 4, and 6 wk after the cell implantation, the experimental bladders were extirpated. The bladder tissues were examined by immunohistochemistry for alpha-smooth muscle actin (SMA). The HAMC-derived cells were detected by antihuman nuclei antibody (HuNu). Separately, bladder muscle strips were examined for contractile responses to potassium. At 1 wk after implantation, the HAMC-derived cells, which were detected by HuNu, differentiated into muscular layers composed of SMA-positive cells. From 2 to 6 wk after implantation, abundant layers of SMA-positive and HuNu-positive cells developed. In control bladders, few SMA-positive cells remained at the injured regions at 1 wk, but by 6 wk, more were present. At 1 wk, the contractile responses to potassium of the cell-implanted bladders were significantly higher than those of the control-injected ones. Control-injected bladders also recovered by 6 wk, but the rate of recovery was slower. Freeze-injured mouse bladders implanted with HAMC-derived cells recovered morphology and function faster than control-injected bladders.