Project description:Hematopoietic stem cells (HSCs) primarily reside in the bone marrow where signals generated by stromal cells regulate their self-renewal, proliferation, and trafficking. Endosteal osteoblasts and perivascular stromal cells including endothelial cells3, CXCL12-abundant reticular (CAR) cells, leptin-receptor positive stromal cells, and nestin-GFP positive mesenchymal progenitors have all been implicated in HSC maintenance. However, it is unclear if specific hematopoietic progenitor cell (HPC) subsets reside in distinct niches defined by the surrounding stromal cells and the regulatory molecules they produce. CXCL12 (stromal-derived factor-1, SDF-1) regulates both HSCs and lymphoid progenitors and is expressed by all of these stromal cell populations. Here, we selectively deleted Cxcl12 from candidate niche stromal cell populations and characterized the effect on HPCs. Deletion of Cxcl12 from mineralizing osteoblasts has no effect on HSCs or lymphoid progenitors. Deletion of Cxcl12 from osterix-expressing stromal cells, which includes CAR cells and osteoblasts, results in constitutive HPC mobilization and a loss of B lymphoid progenitors, but HSC function is normal. Cxcl12 deletion in endothelial cells results in a modest loss of long-term repopulating activity. Strikingly, deletion of Cxcl12 in nestin-negative mesenchymal progenitors using Prx1-Cre is associated with a marked loss of HSCs, long-term repopulating activity, HSC quiescence, and common lymphoid progenitors. These data suggest that osterix-expressing stromal cells comprise a distinct niche that supports B lymphoid progenitors and retains HPC in the bone marrow, while expression of CXCL12 from stromal cells in the perivascular region, including endothelial cells and mesenchymal progenitors, support HSCs. Total of three samples of two groups analyzed. Replica samples of CXCL12-abundant reticular (CAR) cells from two CXCL12-GFP knock-in mice and a combined sample of PDGFRa+ Sca+ CD45- lineage- cells from three Prx1-Cre Rosa26Ai9/+ Cxcl12gfp/+ mice were used and analyzed.
Project description:METTL14 forms a protein complex that induces m6A methylation on RNA but its roles in mouse limb development remains elusive. We knocked out Mettl14 in a limb bud-specific manner with the Prx1 promoter-driven Cre. The resulting Prx1-cre;Mettl14 flox/flox (conditional KO or cKO) mice showed shorter limbs with disrupted bone and cartilage development compared with the heterozygous Prx1-cre;Mettl14 wild type/flox (cHet) control mice. To understand the molecular basis for the abnormalities, we analyzed polysome RNA prepared from day 12.5 (E12.5) embryonic limb buds with RNA-seq.
Project description:METTL14 forms a protein complex that induces m6A methylation on RNA but its roles in mouse limb development remains elusive. We knocked out Mettl14 in a limb bud-specific manner with the Prx1 promoter-driven Cre. The resulting Prx1-cre;Mettl14 flox/flox (conditional KO or cKO) mice showed shorter limbs with disrupted bone and cartilage development compared with the heterozygous Prx1-cre;Mettl14 wild type/flox (cHet) control mice. To understand the molecular basis for the abnormalities, we applied total RNA from day 12.5 (E12.5) embryonic limb buds to m6A-seq.
Project description:Purpose: We have used microarrays to identify gene expression profiles that distinguish mouse OS cells from normal pre-osteoblast cells and mature osteoblast cells. Methods: Transcriptional profiles of three cell lines derived from tumors from Osx-Cre p53fl/fl Rbfl/fl (fibroblastic OS) mouse model, and from pre-osteoblast cells (Kusa4b10 mouse bone marrow stromal cell line) and osteoblast cells (derived by in vitro differentiation of the Kusab410 mouse bone marrow stromal cell line) were generated by microarray analysis, each in triplicate, using Affymetrix mouse Gene1.0ST arrays. Transcriptional profiles were analyzed in cell lines derived from tumors from a genetically engineered mouse model of human osteosarcoma (Osx-Cre p53fl/fl Rbfl/fl) and osteoblast cells derived from the Kusa4b10 mouse bone marrow stromal cell line, in the undifferentiated state (pre-osteoblasts) and differentiated state (osteoblasts).
Project description:The expression of Prx1 has been used as a marker to define the skeletal stem cells (SSC) populations found within the bone marrow and periosteum that contribute to bone regeneration. However, Prx1 expressing SSCs (Prx1-SSCs) are not restricted to the bone compartments, but are also located within the muscle and able to contribute to ectopic bone formation. Little is known however, about the mechanism(s) regulating Prx1-SSCs that reside in muscle and how they participate in bone regeneration. This study compared both the intrinsic and extrinsic factors of the periosteum and muscle derived Prx1-SSCs and analyzed their regulatory mechanisms of activation, proliferation, and skeletal differentiation. There was considerable transcriptomic heterogeneity in the Prx1-SSCs found in muscle or the periosteum however in vitro cells from both tissues show tri-lineage (adipose, cartilage and bone) differentiation. At homeostasis, periosteal derived Prx1 cells were proliferative and low levels of BMP2 were able to promote their differentiation, while the muscle derived Prx1 cells were quiescent and refractory to comparable levels of BMP2 that promoted periosteal cell differentiation. The transplantation of Prx1-SCC from muscle and periosteum into either the same site from which they were isolated, or their reciprocal sites showed that periosteal cell transplanted onto the surface of bone tissues differentiated into bone and cartilage cells but was incapable of similar differentiation when transplanted into muscle. Prx1-SSCs from the muscle showed no ability to differentiate at either site of transplantation. Both fracture and ten times the BMP2 dose was needed to promote muscle-derived cells to rapidly enter the cell cycle as well as undergo skeletal cell differentiation. This study elucidates the diversity of the Prx1-SSC population showing that cells within different tissue sites are intrinsically different. While muscle tissue must have factors that promote Prx1-SSC to remain quiescent, either bone injury or high levels of BMP2 can activate these cells to both proliferate and undergo skeletal cell differentiation. Finally, these studies raise the possibility that muscle SSCs are potential target for skeletal repair and bone diseases.
Project description:Hematopoietic stem cells (HSCs) primarily reside in the bone marrow where signals generated by stromal cells regulate their self-renewal, proliferation, and trafficking. Endosteal osteoblasts and perivascular stromal cells including endothelial cells3, CXCL12-abundant reticular (CAR) cells, leptin-receptor positive stromal cells, and nestin-GFP positive mesenchymal progenitors have all been implicated in HSC maintenance. However, it is unclear if specific hematopoietic progenitor cell (HPC) subsets reside in distinct niches defined by the surrounding stromal cells and the regulatory molecules they produce. CXCL12 (stromal-derived factor-1, SDF-1) regulates both HSCs and lymphoid progenitors and is expressed by all of these stromal cell populations. Here, we selectively deleted Cxcl12 from candidate niche stromal cell populations and characterized the effect on HPCs. Deletion of Cxcl12 from mineralizing osteoblasts has no effect on HSCs or lymphoid progenitors. Deletion of Cxcl12 from osterix-expressing stromal cells, which includes CAR cells and osteoblasts, results in constitutive HPC mobilization and a loss of B lymphoid progenitors, but HSC function is normal. Cxcl12 deletion in endothelial cells results in a modest loss of long-term repopulating activity. Strikingly, deletion of Cxcl12 in nestin-negative mesenchymal progenitors using Prx1-Cre is associated with a marked loss of HSCs, long-term repopulating activity, HSC quiescence, and common lymphoid progenitors. These data suggest that osterix-expressing stromal cells comprise a distinct niche that supports B lymphoid progenitors and retains HPC in the bone marrow, while expression of CXCL12 from stromal cells in the perivascular region, including endothelial cells and mesenchymal progenitors, support HSCs.
Project description:TGF-β regulates fetale bone marrow niche emergence. Abrogating TGF-β signaling in mesenchymal cells during development results in a marked expansion of adipocytes and CAR cells in the bone marrow, while osteoblasts are reduced. RNA expression data from Osx-Cre targeted mesenchymal stromal cells obtained from E16.5 mouse hindlimbs of transgenic mice lacking Tgfbr2 in mesenchymal stromal cells or littermate controls.
Project description:Bone marrow-derived macrophages (BMMs) from Uba3(flox/flox) mice or Uba3(flox/flox; lyz2-cre) mice were stimulated with or without 100ng/ml LPS for 4 hours. The total RNA was prepared and subjected to microarray.
Project description:Bone marrow-derived macrophages (BMMs) from Nedd8(flox/flox) mice or Nedd8(flox/flox; lyz2-cre) mice were stimulated with or without 100ng/ml LPS for 4 hours. The total RNA was prepared and subjected to microarray.
Project description:Extracellular vesicles (EVs) are key mediators of intercellular communication, with important roles in numerous physiological and pathological processes, including profound effects on bone metabolism. These small membrane-bound vesicles are produced and released in the extracellular environment by virtually all cell types, including cells in the osteogenic lineage such as bone marrow-derived mesenchymal stem cells (MSCs), osteoblasts, osteoclasts and osteocytes. EVs serve as potent carriers of bioactive molecules, such as nucleic acids, proteins, lipids and metabolites, where they can influence recipient cells through fusion with target cell membranes to deliver these functional biomolecules. However, once released, the source cell of the EV is difficult to ascertain with any certainty. To overcome this obstacle, we developed a conditional (e.g. Cre-mediated) mouse model that expresses an EV tag, containing a fusion of CD81 and multiple C-terminal tags, termed the “Snorkel-tag”. By crossing with a Cre of interest, representing a specific cell-type or tissue, the specific EV subpopulations that are released can be isolated using antibody affinity columns. We crossed the CAGS-Snorkel mouse with Prx1- and Ocn-Cre, representing cell-types in the early vs late stages of osteoblast differentiation, isolated EVs from bone marrow plasma, and treated mouse bone marrow stromal cells (mBMSCs) with Prx1-EVs, Ocn-EVs or All-EVs (isolated using a Pan EV Isolation Kit [Miltenyi Biotec]) for 3 days and performed bulk RNA-sequencing. We found unique transcriptional and pathway signatures elicited by the different EV subpopulations in the mBMSCs, suggesting that EVs from diverse sources have distinct biological activities.