Rapid activation of hematopoietic stem cells

Adult hematopoietic stem cells (HSCs) in the bone marrow (BM) are quiescent. Following perturbations, such as blood loss or infection, HSCs may undergo activation. Surprisingly, little is known about the earliest stages of HSCs activation. We utilize surface markers of HSCs activation, CD69 and CD317, revealing a response as early as 2 h after stimulation. The dynamic expression of HSCs activation markers varies between viral-like (poly-Inosinic-poly-Cytidylic) or bacterial-like (Lipopolysaccharide) immune stimuli. We further quantify dose response, revealing a low threshold, and similar sensitivity of HSCs and progenitors in the BM. Finally, we find a positive correlation between the expression of surface activation markers and early exit from quiescence. Our data show that the response of adult stem cells to immune stimulation is rapid and sensitive, rapidly leading HSCs out of quiescence.

High throughput screen for the improvement of inducible promoters for tumor microenvironment cues

Cancer immunotherapies are highly potent and are gaining wide clinical usage. However, severe side effects require focusing effector immune cell activities on the tumor microenvironment (TME). We recently developed a chimeric antigen receptor tumor-induced vector (CARTIV), a synthetic promoter activated by TME factors. To improve CARTIV functions including background, activation levels, and synergism, we screened a library of promoters with variations in key positions. Here, we present a screening method involving turning ON/OFF stimulating TNFα and IFNγ cytokines, followed by sequential cell sorting. Sequencing of enriched promoters identified seventeen candidates, which were cloned and whose activities were then validated, leading to the identification of two CARTIVs with lower background and higher induction. We further combined a third hypoxia element with the two-factor CARTIV, demonstrating additional modular improvement. Our study presents a method of fine-tuning synthetic promoters for desired immunotherapy needs.

Isolation of Murine Myeloid Progenitor Populations by CD34/CD150 Surface Markers

Myeloid progenitors are intermediates between Hematopoietic Stem Cells (HSCs) and Myeloid effector progeny. In mouse bone marrow, they are part of the Lineage⁻ cKit⁺ Sca1⁻ (LK) compartment. To date, most researchers used CD34 and FcγR surface markers for the dissection of this compartment into various populations. Surprisingly, however, this approach does not provide distinct separation by fluorescence-activated cell sorting (FACS). In this study, we suggest using CD150 instead of FcγR. We re-analyzed published single-cell RNA-Seq data and found that CD34/CD150 provides better sub-populations separation, compared to the “classical” CD34/FcγR-based approach. We confirm our findings by independent FACS analysis. We demonstrate comparable differentiation potential of the newly-obtained LK sub-populations, like previous “classical” ones. Therefore, we suggest the CD34/CD150 gating strategy, utilizing commonly-used surface markers, as a robust and reproducible separation of the LK compartment into distinct sub-populations.

Hypersensitivity response has negligible impact on Hematopoietic Stem Cells

Immune cells are generated from hematopoietic stem cells (HSCs) in the bone marrow (BM). Immune stimulation can rapidly activate HSCs out of their quiescent state to accelerate the generation of immune cells. HSCs' activation follows various viral or bacterial stimuli, and we sought to investigate the hypersensitivity immune response. Surprisingly, the Ova-induced hypersensitivity peritonitis model finds no significant changes in BM HSCs. HSC markers cKIT, SCA1, CD48, CD150, and the Fgd5-mCherry reporter showed no significant difference from control. Functionally, hypersensitivity did not alter HSCs' potency, as assayed by transplantation. We further characterized the possible impact of hypersensitivity using RNA-sequencing of HSCs, finding minor changes at the transcriptome level. Moreover, hypersensitivity induced no significant change in the proliferative state of HSCs. Therefore, this study suggests that, in contrast to other immune stimuli, hypersensitivity has no impact on HSCs.

Enteral nutrition in the early postoperative period: a new semi-elemental formula versus total parenteral nutrition

Several studies have reported that gastrointestinal (GI) intolerance symptoms are the limiting factor to enteral alimentation in the immediate postoperative period and often the reason for resorting to total parenteral nutrition (TPN). We postulated that Reabilan HN (a recently developed small peptide-based formula, in part obtained by enzyme hydrolysis of proteins) might be better absorbed and better tolerated so as to avoid the need for TPN. Accordingly, 19 patients undergoing major abdominal surgery were randomly assigned to receive Reabilan HN via jejunostomy or an equicaloric isonitrogenous TPN regimen. Both were begun 6 hr postoperatively at 25 ml/hr and increased by 25 ml/hr at 12-hr intervals up to the rate providing 1.5 times the calculated REE. GI tolerance to enteral feeding was excellent during the first three postoperative days, allowing the progression of the feeding rate to 99% of goal. During the next 3 days (starting on average 1.7 days after the return of bowel sounds), GI intolerance symptoms required a reduction in feeding rate to 52% on average. Subsequently, the symptoms resolved and the feeding rate reached 96% of goal. Although overall mean daily calorie and nitrogen intakes were lower for the enteral than for the TPN group (79.6 +/- 10.2% vs 94.6 +/- 3.8% of goal; p less than 0.01), the enteral group was nevertheless in positive caloric and nitrogen balance, and maintained similar serum albumin, prealbumin, and plasma transferrin levels. Average daily cost of supplies was $44.36 for enteral vs $102.10 for parenteral nutrition (p less than 0.001). We conclude that enteral feeding using this formula is well tolerated and cost-effective in the immediate postoperative period.(ABSTRACT TRUNCATED AT 250 WORDS)