A major goal in aging research is to improve health during aging. In the case of mice, genetic manipulations that shorten or lengthen telomeres result, respectively, in decreased or increased longevity. Based on this, we have tested the effects of a telomerase gene therapy in adult (1 year of age) and old (2 years of age) mice. Treatment of 1‐ and 2‐year old mice with an adeno associated virus (AAV) of wide tropism expressing mouse TERT had remarkable beneficial effects on health and fitness, including insulin sensitivity, osteoporosis, neuromuscular coordination and several molecular biomarkers of aging. Importantly, telomerase‐treated mice did not develop more cancer than their control littermates, suggesting that the known tumorigenic activity of telomerase is severely decreased when expressed in adult or old organisms using AAV vectors. Finally, telomerase‐treated mice, both at 1‐year and at 2‐year of age, had an increase in median lifespan of 24 and 13%, respectively. These beneficial effects were not observed with a catalytically inactive TERT, demonstrating that they require telomerase activity. Together, these results constitute a proof‐of‐principle of a role of TERT in delaying physiological aging and extending longevity in normal mice through a telomerase‐based treatment, and demonstrate the feasibility of anti‐aging gene therapy. See accompanying article http://dx.doi.org/10.1002/emmm.201200246

Summary: Here, we show that a small‐molecule activator of telomerase (TA‐65) purified from the root of Astragalus membranaceus is capable of increasing average telomere length and decreasing the percentage of critically short telomeres and of DNA damage in haploinsufficient mouse embryonic fibroblasts (MEFs) that harbor critically short telomeres and a single copy of the telomerase RNA Terc gene (G3 Terc^+/− MEFs). Importantly, TA‐65 does not cause telomere elongation or rescue DNA damage in similarly treated telomerase‐deficient G3 Terc^−/− littermate MEFs. These results indicate that TA‐65 treatment results in telomerase‐dependent elongation of short telomeres and rescue of associated DNA damage, thus demonstrating that TA‐65 mechanism of action is through the telomerase pathway. In addition, we demonstrate that TA‐65 is capable of increasing mouse telomerase reverse transcriptase levels in some mouse tissues and elongating critically short telomeres when supplemented as part of a standard diet in mice. Finally, TA‐65 dietary supplementation in female mice leads to an improvement of certain health‐span indicators including glucose tolerance, osteoporosis and skin fitness, without significantly increasing global cancer incidence.

Differentiation and specialization of epithelial cells in the small intestine are regulated in two ways. First, there is differentiation along the crypt-villus axis of the intestinal stem cells into absorptive enterocytes, Paneth, goblet, tuft, enteroendocrine, or M cells, which is mainly regulated by WNT. Second, there is specialization along the cephalocaudal axis with different absorptive and digestive functions in duodenum, jejunum, and ileum that is controlled by several transcription factors such as GATA4. However, so far it is unknown whether location-specific functional properties are intrinsically programmed within stem cells or if continuous signaling from mesenchymal cells is necessary to maintain the location-specific identity of the small intestine. Using the pure epithelial organoid technique, we show that region-specific gene expression profiles are conserved throughout long-term cultures of both mouse and human intestinal stem cells and correlated with differential Gata4 expression. Furthermore, the human organoid culture system demonstrates that Gata4-regulated gene expression is only allowed in absence of WNT signaling. These data show that location-specific function is intrinsically programmed in the adult stem cells of the small intestine and that their differentiation fate is independent of location-specific extracellular signals. In light of the potential future clinical application of small intestine-derived organoids, our data imply that it is important to generate GATA4-positive and GATA4-negative cultures to regenerate all essential functions of the small intestine. Stem Cells 2014;32:1083–1091

Peyer's patches consist of domains of specialized intestinal epithelium overlying gut-associated lymphoid tissue (GALT). Luminal antigens reach the GALT by translocation through epithelial gatekeeper cells, the so-called M cells. We recently demonstrated that all epithelial cells required for the digestive functions of the intestine are generated from Lgr5-expressing stem cells. Here, we show that M cells also derive from these crypt-based Lgr5 stem cells. The Ets family transcription factor SpiB, known to control effector functions of bone marrow-derived immune cells, is specifically expressed in M cells. In SpiB^−/− mice, M cells are entirely absent, which occurs in a cell-autonomous fashion. It has been shown that Tnfsf11 (RankL) can induce M cell development in vivo. We show that in intestinal organoid (“minigut”) cultures, stimulation with RankL induces SpiB expression within 24 h and expression of other M cell markers subsequently. We conclude that RankL-induced expression of SpiB is essential for Lgr5 stem cell-derived epithelial precursors to develop into M cells.

End‐stage liver diseases are an increasing health burden, and liver transplantations are currently the only curative treatment option. Due to a lack of donor livers, alternative treatments are urgently needed. Human liver organoids are very promising for regenerative medicine; however, organoids are currently cultured in Matrigel, which is extracted from the extracellular matrix of the Engelbreth‐Holm‐Swarm mouse sarcoma. Matrigel is poorly defined, suffers from high batch‐to‐batch variability and is of xenogeneic origin, which limits the clinical application of organoids. Here, a novel hydrogel based on polyisocyanopeptides (PIC) and laminin‐111 is described for human liver organoid cultures. PIC is a synthetic polymer that can form a hydrogel with thermosensitive properties, making it easy to handle and very attractive for clinical applications. Organoids in an optimized PIC hydrogel proliferate at rates comparable to those observed with Matrigel; proliferation rates are stiffness‐dependent, with lower stiffnesses being optimal for organoid proliferation. Moreover, organoids can be efficiently differentiated toward a hepatocyte‐like phenotype with key liver functions. This proliferation and differentiation potential maintain over at least 14 passages. The results indicate that PIC is very promising for human liver organoid culture and has the potential to be used in a variety of clinical applications including cell therapy and tissue engineering.