Two new developments recently in the culture methods for NPCs. First of all, Tanigawa and colleagues continued on their previous work on the culture of rat NPCs with a new study in Cell Reports on the culture of mouse and human NPCs. Slightly different conditions from the rat protocol and different from the protocol from the Oxburgh lab. Although the new Tanigawa method can only maintain the the cells in culture for 19 days with full developmental potential (but still 1800-fold expansion which could be enough for many applications), importantly this includes the potential to form the potential to form proximal structures and glomeruli. Very elegantly, the authors also show that the NPCs can be cultured using in vitro differentiated ES/iPS cells as starting material.
This was followed today by a paper in Cell Stem Cell by Li and colleagues. It is tempting to consider this an ‘another one’ paper, but there are a lot of clearly impressive feats reported in this paper. For instance, the self-renewal capacity is incredible, p110 after 17 months and counting. In contrast to other protocols it seems to be equally efficient on NPCs from different stage embryonic kidneys, and they show full developmental potential in vitro and in vivo, they demonstrate methods for genome editing of these cultures, they show that paracrine factors from these cultures can improve survival in an acute kidney injury model, and slightly different but apparently just as effective conditions are described for human NPCs. One could reasonably argue that there is too much in this paper and by necessity many things are just being touched on. But the great thing is there is so much in this paper, even if it only touches on many things :-). This should get many people think about new experiments, and luckily the protocols included in the supplementary data look extremely detailed. .
Having now several different protocols for the culture of NPCs it gets interesting to pay more attention to the the differences. Species differences might point to biological differences between these species with respect to the NPC niche, but even differences between the protocols for the same species could, coupled to the differences in developmental capacity and stage of origin of the cells that can be used, give new leads to further define the niche of these cells at different time-points, and by extension differences between these cells and developmental stages. In this respect table S1 and S2 in the Li et al Cell Stem Cell paper is a treat. For instance, as already pointed out by Tanigawa et al and confirmed by Li et al, differences in proximal developmental capacity might be linked to the exact activity of the β-catenin pathway and be explained by our work on the post-MET nephron patterning. Likewise, close comparison between growth factors, concentration and the exact capabilities of the different protocols might give interesting new insights.