Homing and Long-Term Engraftment of Long- and Short-Term Renewal Hematopoietic Stem Cells

Long-term hematopoietic stem cells (LT-HSC) and short-term hematopoietic stem cells (ST-HSC) have been characterized as having markedly different in vivo repopulation, but similar in vitro growth in liquid culture. These differences could be due to differences in marrow homing. We evaluated this by comparing results when purified ST-HSC and LT-HSC were administered to irradiated mice by three different routes: intravenous, intraperitoneal, and directly into the femur. Purified stem cells derived from B6.SJL mice were competed with marrow cells from C57BL/6J mice into lethally irradiated C57BL/6J mice. Serial transplants into secondary recipients were also carried out. We found no advantage for ST-HSC engraftment when the cells were administered intraperitoneally or directly into femur. However, to our surprise, we found that the purified ST-HSC were not short-term in nature but rather gave long-term multilineage engraftment out to 387 days, albeit at a lower level than the LT-HSC. The ST-HSC also gave secondary engraftment. These observations challenge current models of the stem cell hierarchy and suggest that stem cells are in a continuum of change

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Experiment 3: intrafemoral injection.

<p>Chimerism (%CD45.1) (ordinate) plotted as a function of Days Post Transplant (abscissa), type of cells injected (•▪: LT-HSC, ○□: ST-HSC), and source (•○: whole blood, ▪□: whole bone marrow) for several different methods of summary: A) raw individual mouse percent CD45 cells that were CD45.1, B) mean ± standard error of the mean, C) median with inter-quartile range, and D) percent of mice with greater than 10% of CD45 cells being CD45.1. For each tile, the data from the primary transplant is plotted on the left and secondary transplant on the right, separated by a vertical line at zero for the secondary transplant.</p

Experiment 2: intravenous injection.

<p>Chimerism (%CD45.1) (ordinate) plotted as a function of Days Post Transplant (abscissa), type of cells injected (•▪: LT-HSC, ○□: ST-HSC), and source (•○: whole blood, ▪□: whole bone marrow) for several different methods of summary: A) raw individual mouse percent CD45 cells that were CD45.1, B) mean ± standard error of the mean, C) median with inter-quartile range, and D) percent of mice with greater than 10% of CD45 cells being CD45.1. For each tile, the data from the primary transplant is plotted on the left and secondary transplant on the right, separated by a vertical line at zero for the secondary transplant.</p

Experiment 1: intraperitoneal injection.

<p>Chimerism (%CD45.1) (ordinate) plotted as a function of Days Post Transplant (abscissa), type of cells injected (•▪: LT-HSC, ○□: ST-HSC), and source (•○: whole blood, ▪□: whole bone marrow) for several different methods of summary: A) raw individual mouse percent CD45 cells that were CD45.1, B) mean ± standard error of the mean, C) median with inter-quartile range, and D) percent of mice with greater than 10% of CD45 cells being CD45.1. For each tile, the data from the primary transplant is plotted on the left and secondary transplant on the right, separated by a vertical line at zero for the secondary transplant.</p

Sorting Scheme.

<p>Fluorescence-activated cell sorting of lineage negative (FITC ⁻) leukocytes to isolate long term- and short term-hematopoietic stem cell groups. A) Forward and side scatter plot isolates cells. B) Forward scatter and PI plot captures living cells (PI⁻). C) Forward scatter and FITC plot removes remaining lineage⁺ cells (FITC⁺) and retains lineage⁻ cells (FITC ⁻). D) Sca-1 (Alexa Fluor 405⁺) and c-kit (APC ⁺) positive cells are isolated. E) Forward scatter and Flk-2 plot separates long term cells (Flk-2⁻ PE⁻) from short term cells (Flk-2⁺ PE⁺). Stem cells in the LT-HSC (Flk-2⁻) (F1, F2) and ST-HSC (Flk-2⁺) (G1, G2) groups were resorted to ensure that contaminating cells are not present in either population.</p