aKG supplementation in vivo leads to renewal of Paneth cells, which in old animals reduces expression of the Wnt-antagonist Notum, and rescues recovery after 5-FU-induced damage to the level of young animals. 5/8

ISCs with old mitochondria have faster TCA-cycle turnover and higher amounts of aKG, which drives the bias towards the Paneth cell linage and increased Tet2-dependent 5-hydroxy methylation of cytosines in DNA. 4/8

These stem cells (ISC-mito-O) are better at forming organoids in vitro due to their ability to regenerate Paneth cells faster. 3/8

Using in vivo snap-tag labeling of mitochondrial age-classes, we found that the intestine contains a subset of stem cells that retain old mitochondria through asymmetric division. 2/8

Thank you to the organizers of the fantastic meeting #CSMetabolites2025 Kivanc Birsoy @robzonculab.bsky.social and @cellpress.bsky.social editors Allyson Evans @kristabledsoe.bsky.social We had a fantastic time in Sitges, looking forward to this meeting happening again! @cellpressevents.bsky.social

Congratulations Hien Bui who showed remarkable persistence in initiating, leading and finalizing the project. Thank you to everyone involved, especially second authors @simonsterson.bsky.social Agustin Sola Carvajal and all collaborators at @helsinki.fi i.fi @metastem.bsky.social and @ki.se. 9/9

In conclusion, we discovered a new role for peroxisomes in determination of cell fate of adult stem cells through their age-dependent segregation and spatially compartmentalized metabolism. The SNAP-PTS1 mouse will be a valuable tool for studying peroxisomal heterogeneity also in other tissues. 8/9

We found that sub-cellular compartmentalization of specific metabolic reactions determines cell fate as expression of G6PD specifically on the peroxisome membrane, but not in the cytosol or in the peroxisome matrix, boosted stemness through peroxisomal ether lipid synthesis. 7/9

To find the mechanism, we performed proteomics of old and young peroxisomes isolated by density centrifugation and single-organelle FACS and found the metabolic enzyme G6PD to be enriched on old peroxisomes. 6/9

Similarly, during in vivo ACD of epidermal stem cells, old peroxisomes were preferentially inherited by the daughter cell that remains attached to the basement membrane. 5/9

In in vitro ACD of basal mammary epithelial cells, daughter cells with old peroxisomes PO exhibited higher self-renewal and bi-potency than daughter cells with young peroxisomes PY, demonstrated by their ability to form organoids and create the luminal lineage to induce branching morphogenesis. 4/9

To study if this takes place in primary adult stem and progenitor cells, we generated a novel mouse model expressing the SNAP-PTS1 construct, allowing for temporal labelling of peroxisomes in vivo, and saw heterogeneity of peroxisome age in epithelial cells in the mammary gland and the skin. 3/9

Hien asked if peroxisomes are age-selectively apportioned in asymmetric cell divisions (ACD) as we previously showed for mitochondria (Katajisto et al Science 2015, Döhla et al NCB 2022). To our surprise, this time it was the old organelles that were inherited by the self-renewing daughter cell! 2/9

4/6 Interestingly, high Aspn levels in the old lead to persistently activated fetal-like state without resolution post-injury, resulting in reduced recovery. This stalled developmental reversion can be resolved by activating Wnt signaling in the old animals

3/6 Mechanistically pericryptal fibroblasts express Aspn, and induction of Aspn during injury promotes TGF-B signalling in intestinal epithelial cells via CD44, leading to fetal-like reversion and repair of damaged epithelium in mice, which is induced and resolved in a controlled manner in the young

2/6 We found that the intestinal epithelium transiently adopts a TGF-B-dependent fetal-like program when re-epithelializing on decellularized ECM (iECM). Thus, we establish iECM as a platform for modeling epithelial injury responses ex vivo