Mesenchymal stromal cell-derived extracellular vesicles rescue radiation damage to murine marrow hematopoietic cells

Mesenchymal stromal cells (MSCs) have been shown to reverse radiation damage to marrow stem cells. We have evaluated the capacity of MSC-derived extracellular vesicles (MSC-EVs) to mitigate radiation injury to marrow stem cells at 4 h to 7 days after irradiation. Significant restoration of marrow stem cell engraftment at 4, 24 and 168 h post irradiation by exposure to MSC-EVs was observed at 3 weeks to 9 months after transplant and further confirmed by secondary engraftment. Intravenous injection of MSC-EVs to 500cGy exposed mice led to partial recovery of peripheral blood counts and restoration of the engraftment of marrow. The murine hematopoietic cell line, FDC-P1 exposed to 500cGy, showed reversal of growth inhibition, DNA damage and apoptosis on exposure to murine or human MSC-EVs. Both murine and human MSC-EVs reverse radiation damage to murine marrow cells and stimulate normal murine marrow stem cell/progenitors to proliferate. A preparation with both exosomes and microvesicles was found to be superior to either microvesicles or exosomes alone. Biologic activity was seen in freshly isolated vesicles and in vesicles stored for up to 6 months in 10% dimethyl sulfoxide at -80 °C. These studies indicate that MSC-EVs can reverse radiation damage to bone marrow stem cells.

Marrow cell genetic phenotype change induced by human lung cancer cells

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Background: Murine lung-derived microvesicles are capable of inducing lung-specific mRNA in marrow cells, when co-cultured across from these cells, but separated from them by a cell-impermeable (0.4 micron) membrane. These converted murine marrow cells showed mRNA elevations, lung-specific protein production and enhanced capacity to convert to lung epithelial cells after in vivo transplantation into irradiated mice. We examine here whether fresh tissue from lung cancer patients would have the same capacity to genetically alter co-cultured human marrow cells. Methods: Lung cancer samples were collected from 5 patients undergoing surgery. Minced tumor tissue at 50–100 mg was co-cultured in a semi-permeable culture plate insert opposite 3.0 ×106 human marrow cells. The marrow cells were harvested after 2–7 days of co-culture. Marrow cell RNA was analyzed for lung specific mRNA using real time RT-PCR. Relative levels of gene expression was expressed a fold increase compared to level in controls. Results: Lung cancers studied were adenocarcinoma, endobronchial alveolar carcinoma, bronchioloalveolar carcinoma, non-small cell carcinoma and squamous cell carcinoma. mRNAs for aquaporin 1–5, specific for type I pneumocytes and surfactant A-D, specific for type II pneumocytes, were measured. Aquaporin I was elevated in marrow cells from co culture with all lung cancers; elevations ranging from 2.15 to 56.7 fold (mean 23 fold). Similarly surfactant B mRNA was induced in marrow cells by all lung cancers with fold elevations ranging from 7.9 to 2164 (mean fold elevation 668). More variable elevations were also seen with aquaporin 3, 4, and 5, surfactant A, surfactant C, and surfactant D. Ultracentrifugation (28,000 g) of conditioned media from these cancers revealed the presence of microvesicles with diameters of 100–180 nm. Conclusions: These observations indicate that the genetic phenotype of cells in the vicinity of lung cancer cells can be altered and that these alterations might be mediated by microvesicle transfer of genetic information.

No significant financial relationships to disclose.

The marrow cell continuum: stochastic determinism

Traditional models of hematopoiesis have been hierarchical in nature. Over the past 10 years, we have developed data indicating that hematopoiesis is regulated in a continuum with deterministic and stochastic components. We have shown that the most primitive stem cells, as represented by lineage negative rhodamine(low) Hoechst(low) murine marrow cells are continuously or intermittently cycling as determined by in vivo BrdU labeling. When marrow stem cells are induced to transit cell cycle by in vitro exposure to cytokines, either IL-3, IL-6, IL-11, and steel factor or thrombopoietin, FLT3 ligand, and steel factor, they progress through cycle in a highly synchronized fashion. We have determined that when the stem cells progress through a cytokine stimulated cell cycle the homing, engraftment, adhesion protein, global gene expression, and hematopoietic differentiation phenotypes all change in a reversible fashion. This has led to the continuum model, in which, with cycle transit, chromatin is continually changing altering open transcription areas and providing a continually changing landscape of transcriptional opportunity. More recently, we have extended the changing differentiation profiles to differentiation into lung cells and found that non-hematopoietic differentiation also shows cycle related reversibly modulation. These observations all together support a continuum model of stem cell regulation in which the phenotype of the marrow stem cells is continually and reversibly changing over time.

Cloning and expression of the ApaLI, NspI, NspHI, SacI, ScaI, and SapI restriction-modification systems in Escherichia coli

The genes encoding the ApaLI (5'-GTGCAC-3'), NspI (5'-RCATGY-3'), NspHI (5'-RCATGY-3'), SacI (5'-GAGCTC-3'), SapI (5'-GCTCTTCN1-3', 5'-N4GAAGAGC-3') and ScaI (5'-AGTACT-3') restriction-modification systems have been cloned in E. coli. Amino acid sequence comparison of M.ApaLI, M.NspI, M.NspHI, and M.SacI with known methylases indicated that they contain the ten conserved motifs characteristic of C5 cytosine methylases. NspI and NspHI restriction-modification systems are highly homologous in amino acid sequence. The C-termini of the NspI and NlaIII (5'-CATG-3') restriction endonucleases share significant similarity. 5mC modification of the internal C in a SacI site renders it resistant to SacI digestion. External 5mC modification of a SacI site has no effect on SacI digestion. N4mC modification of the second base in the sequence 5'-GCTCTTC-3' blocks SapI digestion. N4mC modification of the other cytosines in the SapI site does not affect SapI digestion. N4mC modification of ScaI site blocks ScaI digetion. A DNA invertase homolog was found adjacent to the ApaLI restriction-modification system. A DNA transposase subunit homolog was found upstream of the SapI restriction endonuclease gene.