A crucial player in immune regulation, FoxP3 regulatory T cells (Tregs) are drawing attention for their heterogeneity and noncanonical functions. Here, we describe a Treg subpopulation that controls hematopoietic stem cell (HSC) quiescence and engraftment. These Tregs highly expressed an HSC marker, CD150, and localized within the HSC niche in the bone marrow (BM). Specific reduction of BM Tregs achieved by conditional deletion of CXCR4 in Tregs increased HSC numbers in the BM. Adenosine generated via the CD39 cell surface ectoenzyme on niche Tregs protected HSCs from oxidative stress and maintained HSC quiescence. In transplantation settings, niche Tregs prevented allogeneic (allo-) HSC rejection through adenosine and facilitated allo-HSC engraftment. Furthermore, transfer of niche Tregs promoted allo-HSC engraftment to a much greater extent than transfer of other Tregs. These results identify a unique niche-associated Treg subset and adenosine as regulators of HSC quiescence, abundance, and engraftment, further highlighting their therapeutic utility.

Millions of people worldwide with incurable end-stage lung disease die because of inadequate treatment options and limited availability of donor organs for lung transplantation 1 . Current bioengineering strategies to regenerate the lung have not been able to replicate its extraordinary cellular diversity and complex three-dimensional arrangement, which are indispensable for life-sustaining gas exchange 2 , 3 . Here we report the successful generation of functional lungs in mice through a conditional blastocyst complementation (CBC) approach that vacates a specific niche in chimeric hosts and allows for initiation of organogenesis by donor mouse pluripotent stem cells (PSCs). We show that wild-type donor PSCs rescued lung formation in genetically defective recipient mouse embryos unable to specify (due to Ctnnb1 cnull mutation) or expand (due to Fgfr2 cnull mutation) early respiratory endodermal progenitors. Rescued neonates survived into adulthood and had lungs functionally indistinguishable from those of wild-type littermates. Efficient chimera formation and lung complementation required newly developed culture conditions that maintained the developmental potential of the donor PSCs and were associated with global DNA hypomethylation and increased H4 histone acetylation. These results pave the way for the development of new strategies for generating lungs in large animals to enable modeling of human lung disease as well as cell-based therapeutic interventions 4 – 6 .

Defining adaptive immunity with the complex structures of the human gastrointestinal (GI) tract over life, is essential for understanding immune responses to ingested antigens, commensal and pathogenic microorganisms, and dysfunctions in disease. We present here an analysis of lymphocyte localization and T cell subset composition across the human GI tract including mucosal sites (jejunum, ileum, colon), gut-associated lymphoid tissues (isolated lymphoid follicles (ILFs), Peyer’s patches (PPs), appendix) and mesenteric lymph nodes (MLNs) from a total of 68 donors spanning 8 decades of life. In pediatric donors, ILFs and PP containing naïve T cells and regulatory T cells (Tregs) are prevalent in jejunum and ileum, respectively; these decline in frequency with age, contrasting stable frequencies of ILFs and T cell subsets in the colon. In the mucosa, tissue resident memory T cells develop during childhood, and persist in high frequencies into advanced ages, while T cell composition changes with age in GALT and MLN. These spatial and temporal features of human intestinal T cell immunity define signatures that can be used to train predictive machine learning algorithms. Our findings demonstrate an anatomic basis for age-associated alterations in immune responses, and establish a quantitative baseline for intestinal immunity to define disease pathologies.

Glomerular CD163 macrophages are the predominant phenotype in the kidneys of lupus patients. These findings indicate that the u-sCD163 level can serve as a biomarker for macrophage-dependent glomerular inflammation in human LN.

Current studies suggest that mesenchymal stromal cells (MSCs) improve acute kidney injury (AKI) via paracrine/endocrine effects. We established human adipose tissue-derived stromal cells (hASCs) cultured in low (2%) serum (hLASCs), which have great potential of tissue regeneration. The present study was performed to investigate the therapeutic effects of hLASCs on AKI and to clarify the mechanisms involved. In low serum, hASCs proliferated well, while human bone marrow-derived stromal cells (hBMSCs) did not. hLASCs secreted higher levels of hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) than did hASCs cultured in high (20%) serum (hHASCs) or hBMSCs cultured in high serum (hHBMSCs). AKI was induced in nude rats by folic acid, and hLASCs, hHASCs or control medium were administered into the renal subcapsules. hLASCs significantly attenuated acute renal damage, while hHASCs showed far less effect. Furthermore, interstitial fibrosis observed on day 14 was less pronounced in the hLASCs group. Cell tracking experiment showed no evidence of transdifferentiation. Intravenous injection of hLASCs or hHBMSCs or subcapsular injection of hHBMSCs did not ameliorate AKI. Concerning the mechanisms, our in vivo experiments showed that HGF knockdown by siRNA impaired the ability of hLASCs to protect the kidney from acute injury whereas VEGF knockdown did not. In conclusion, hLASCs, but not hHASCs or hHBMSCs, ameliorated AKI via paracrine effects, and HGF is one of the key mediators.

Optogenetic genome engineering tools enable spatiotemporal control of gene expression and provide new insight into biological function. Here, we report the new version of genetically encoded photoactivatable (PA) Cre recombinase, PA-Cre 3.0. To improve PA-Cre technology, we compare light-dimerization tools and optimize for mammalian expression using a CAG promoter, Magnets, and 2A self-cleaving peptide. To prevent background recombination caused by the high sequence similarity in the dimerization domains, we modify the codons for mouse gene targeting and viral production. Overall, these modifications significantly reduce dark leak activity and improve blue-light induction developing our new version, PA-Cre 3.0. As a resource, we have generated and validated AAV-PA-Cre 3.0 as well as two mouse lines that can conditionally express PA-Cre 3.0. Together these new tools will facilitate further biological and biomedical research.

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Mesenchymal stromal cells (MSCs) derived from adipose tissue have immunomodulatory effects, suggesting that they may have therapeutic potential for crescentic GN. Here, we systemically administered adipose-derived stromal cells (ASCs) in a rat model of anti-glomerular basement membrane (anti-GBM) disease and found that this treatment protected against renal injury and decreased proteinuria, crescent formation, and infiltration by glomerular leukocytes, including neutrophils, CD8 + T cells, and CD68 + macrophages. Interestingly, ASCs cultured under low-serum conditions (LASCs), but not bone marrow-derived MSCs (BM-MSCs), increased the number of immunoregulatory CD163 + macrophages in diseased glomeruli. Macrophages cocultured withASCs, but not with BM-MSCs, adopted an immunoregulatory phenotype. Notably, LASCs polarized macrophages into CD163 + immunoregulatory cells associated with IL-10 production more efficiently than ASCs cultured under high-serum conditions. Pharmaceutical ablation of PGE 2 production, blocking the EP 4 receptor, or neutralizing IL-6 in the coculture medium all significantly reversed this LASC-induced conversion of macrophages. Furthermore, pretreating LASCs with aspirin or cyclooxygenase-2 inhibitors impaired the ability of LASCs to ameliorate nephritogenic IgG-mediated renal injury. Taken together, these results suggest that LASCs exert renoprotective effects in anti-GBM GN by promoting the phenotypic conversion of macrophages to immunoregulatory cells, suggesting that LASC transfer may represent a therapeutic strategy for crescentic GN.