The inability to identify, isolate, and culture intestinal epithelial stem cells (IESCs) has been prohibitive to the study and therapeutic utilization of these cells. Using a Sox9(EGFP) mouse model, we demonstrate that Sox9(EGFP) fluorescence signatures can be used to differentiate between and enrich for progenitors (Sox9(EGFPsubLo)) and multipotent IESCs (Sox9(EGFPlo)). Sox9(EGFPlo) cells generate "organoids" in a recently defined culture system that mimics the native IESC niche. These organoids possess all four differentiated cell types of the small intestine epithelium, demonstrating the multipotent capacity of Sox9(EGFPlo) cells. Our results are consistent with the previously reported observation that single IESCs generate cryptlike units without a detectable mesenchymal cell component. A prospective search revealed that CD24 is expressed in the Sox9(EGFPlo) population and marks IESCs that form organoids in culture. CD24 represents the first cell surface marker that facilitates fluorescence-activated cell sorting enrichment of IESCs with widely available antibodies without requiring a specialized fluorescent reporter gene mouse model.

Osteoarthritis (OA) is a progressive degenerative disease of articular cartilage and surrounding tissues, and is associated with both advanced age and joint injury. Biomechanical factors play a critical role in the onset and progression of OA, yet the mechanisms through which physiologic or pathologic mechanical signals are transduced into a cellular response are not well understood. Defining the role of mechanosensory pathways in cartilage during OA pathogenesis may yield novel strategies or targets for the treatment of OA. The transient receptor potential vanilloid 4 (TRPV4) ion channel transduces mechanical loading of articular cartilage via the generation of intracellular calcium ion transients. Using tissue-specific, inducible Trpv4 gene-targeted mice, we demonstrate that loss of TRPV4-mediated cartilage mechanotransduction in adulthood reduces the severity of aging-associated OA. However, loss of chondrocyte TRPV4 did not prevent OA development following destabilization of the medial meniscus (DMM). These results highlight potentially distinct roles of TRPV4-mediated cartilage mechanotransduction in age-related and post-traumatic OA, and point to a novel disease-modifying strategy to therapeutically target the TRPV4-mediated mechanotransduction pathway for the treatment of aging-associated OA.

Ramalingam S, Daughtridge GW, Johnston MJ, Gracz AD, Magness ST. Distinct levels of Sox9 expression mark colon epithelial stem cells that form colonoids in culture.

We have previously described clinically relevant reductions in fecal microbiota diversity of patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT). Recipients of high-dose chemotherapy and autologous hematopoietic cell transplantation (auto-HCT) incur similar antibiotic exposures and nutritional alterations. To characterize the fecal microbiota in the auto-HCT population, we analyzed 1,161 fecal samples collected from 534 adult recipients of auto-HCT for lymphoma, myeloma and amyloidosis in an observational study conducted at two transplant centers in the United States. Using 16S ribosomal gene sequencing, we assessed fecal microbiota diversity as measured by the inverse Simpson index, and composition. At both centers, early pre-transplant fecal microbiota diversity was lower than in healthy control subjects and decreased further during the course of transplantation. Loss of diversity and domination by specific bacterial taxa occurred during auto-HCT in patterns similar to allo-HCT. Above-median fecal intestinal diversity in the peri-engraftment period was associated with decreased risk of death or progression (PFS HR 0.46 [95% CI, 0.26-0.82], P=0.008), adjusting for disease and disease status. This suggests that further investigation into the health of the intestinal microbiota in auto-HCT patients and post-transplant outcomes should be undertaken.

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