Only an early stage retina but still a good step in the right direction.

UC Irvine scientists have created an eight-layer, early stage retina from human embryonic stem cells, the first three-dimensional tissue structure to be made from stem cells.

It also marks the first step toward the development of transplant-ready retinas to treat eye disorders such as retinitis pigmentosa and macular degeneration that affect millions.

"We made a complex structure consisting of many cell types," said study leader Hans Keirstead of the Reeve-Irvine Research Center and the Sue and Bill Gross Stem Cell Research Center at UCI. "This is a major advance in our quest to treat retinal disease."

One of the things I wonder about future rejuvenation therapies is how much of the repair and replacement will be done by swapping out bigger parts like, say, a retina or a whole organ. Will stem cells and gene therapy be able to repair most existing parts in place? Or will we need to have replacements for most of our organs grown in vats and then swapped into our bodies with surgery? I'd prefer repair in place in order to avoid large numbers of risky surgeries. But replacement of whole organs will be called for due to either urgency of the need or because it will be hard to get stem cells to correctly fill in gaps in structure that are too large and complex for cell therapies to target.