Peter N. Uchakin

Adult-derived stem cells and their potential for use in tissue repair and molecular medicine.

This report reviews three categories of precursor cells present within adults. The first category of precursor cell, the epiblast‐like stem cell, has the potential of forming cells from all three embryonic germ layer lineages, e.g., ectoderm, mesoderm, and endoderm. The second category of precursor cell, the germ layer lineage stem cell, consists of three separate cells. Each of the three cells is committed to form cells limited to a specific embryonic germ layer lineage. Thus the second category consists of germ layer lineage ectodermal stem cells, germ layer lineage mesodermal stem cells, and germ layer lineage endodermal stem cells. The third category of precursor cells, progenitor cells, contains a multitude of cells. These cells are committed to form specific cell and tissue types and are the immediate precursors to the differentiated cells and tissues of the adult. The three categories of precursor cells can be readily isolated from adult tissues. They can be distinguished from each other based on their size, growth in cell culture, expressed genes, cell surface markers, and potential for differentiation. This report also discusses new findings. These findings include the karyotypic analysis of germ layer lineage stem cells; the appearance of dopaminergic neurons after implantation of naive adult pluripotent stem cells into a 6‐hydroxydopamine‐lesioned Parkinsons model; and the use of adult stem cells as transport mechanisms for exogenous genetic material. We conclude by discussing the potential roles of adult‐derived precursor cells as building blocks for tissue repair and as delivery vehicles for molecular medicine.

Plasma Cytokine Concentrations Indicate That In Vivo Hormonal Regulation of Immunity Is Altered During Long-Duration Spaceflight

Aspects of immune system dysregulation associated with long-duration spaceflight have yet to be fully characterized and may represent a clinical risk to crewmembers during deep space missions. Plasma cytokine concentration may serve as an indicator of in vivo physiological changes or immune system mobilization. The plasma concentrations of 22 cytokines were monitored in 28 astronauts during long-duration spaceflight onboard the International Space Station. Blood samples were collected 3 times before flight, 3-5 times during flight (depending on mission duration), at landing, and 30 days after landing. Analysis was performed by bead array immunoassay. With few exceptions, minimal detectable mean plasma concentrations were observed at baseline (launch minus 180) for innate inflammatory cytokines or adaptive regulatory cytokines; however, interleukin (IL)-1ra and several chemokines and growth factors were constitutively present. An increase in the plasma concentration, tumor necrosis factor-α (TNFα), IL-8, IL-1ra, thrombopoietin (Tpo), vascular endothelial growth factor (VEGF), C-C motif chemokine ligand 2 (CCL2), chemokine ligand 4/macrophage inhibitory protein 1b (CCL4), and C-X-C motif chemokine 5/epithelial neutrophil-activating protein 78 (CXCL5) was observed associated with spaceflight. No significant alterations were observed during or following spaceflight for the inflammatory or adaptive/T-regulatory cytokines: IL-1α, IL-1β, IL-2, interferon-gamma (IFN-γ), IL-17, IL-4, IL-5, IL-10, G-CSF, GM-CSF, FGF basic, CCL3, or CCL5. This pattern of cytokine dysregulation suggests multiple physiological adaptations persist during flight, including inflammation, leukocyte recruitment, angiogenesis, and thrombocyte regulation.

Immune Responsiveness Following Academic Stress in First-Year Medical Students

Many studies illustrate that physical or psychologic stressors can alter human immune function, which might predispose one to an increased susceptibility to infections. In the present study, we monitored immune responsiveness in 16 first-year medical students (age 23.8 +/- 2.2 years) during the first examination session. Baseline blood samples were collected 30 days prior to the first examination session. Subsequently, subjects were randomly assigned to two groups, and blood samples were collected at 24 h (POST24h) or 48 h (POST48h) after an examination. The percentage of CD3(+), CD3(+)CD4(+), CD3(+)CD8(+), CD3(+)CD45RO(+), CD3(+)CD45RA(+), CD3(-)CD16(+)56(+), CD19(+), and CD14(+) cells in whole blood was examined to determine changes in circulating immune cell populations. Activation of peripheral blood mononuclear cells (PBMC) with a mixture of phorbol myristate acetate (PMA) and ionomycin or lipopolysaccharide (LPS) for 4 h was used to assess the distribution of interleukin-2 (IL-2)-secreting or interferon-gamma (IFN-gamma)-secreting CD4(+) and CD8(+) cells, as well as IL-1alpha-secreting CD14(+) cells. Activation with a combination of phytohemagglutinin (PHA) and LPS was used to assess secretion of IL-2, IFN-gamma, IL-4, IL-10, soluble IL-2 receptor-alpha (sIL-2Ralpha), IL-1beta, and IL-1R antagonist (IL-1Ra) by PBMC in 48-h cell culture. A significantly higher level of total T cells was found at POST24h, and CD14(+) was elevated at both POST24h and POST48h. The percentage of CD4(+) and CD8(+) cells significantly declined at POST24 and POST48h. A significant elevation in the percentage of memory T cells was observed at POST48h, whereas the percentage of naive T cells was elevated at POST24h and POST48h. These changes were accompanied by a significant decline in percentage of natural killer (NK) cells 24 h after the examination. The percentage of IL-2-producing CD4(+) and CD8(+) cells was significantly lower at POST24h, and the percentage of CD8(+)IFN-gamma(+) cells significantly declined at POST48h. The percentage of CD14(+)IL-1alpha(+) significantly declined at both POST24 and POST48h. A significant decrease was observed in IL-2 secretion 24 h after the examinations, and the secretion of IL-4 and IL-1beta significantly declined at POST48h. No changes in IFN-gamma, IL-10, sIL-2Ralpha, and IL-1Ra secretion were observed. We conclude that the stress outcomes of academic examinations in first-year medical students can significantly alter immune cell distribution and in vitro production and secretion of specific cytokines.

Fatigue in Medical Residents Leads to Reactivation of Herpes Virus Latency

The main objective of this study was to detect fatigue-induced clinical symptoms of immune suppression in medical residents. Samples were collected from the subjects at rest, following the first night (low-stress), and the last night (high-stress) of night float. Computerized reaction tests, Epworth Sleepiness Scale, and Wellness Profile questionnaires were used to quantify fatigue level. DNA of human herpes viruses HSV-1, VZV, EBV, as well as cortisol and melatonin concentrations, were measured in saliva. Residents at the high-stress interval reported being sleepier compared to the rest interval. EBV DNA level increased significantly at both stress intervals, while VZV DNA level increased only at low-stress. DNA levels of HSV-1 decreased at low-stress but increased at high-stress. Combined assessment of the viral DNA showed significant effect of stress on herpes virus reactivation at both stress intervals. Cortisol concentrations at both stress intervals were significantly higher than those at rest.

A case of persistent skin rash and rhinitis with immune system dysregulation onboard the International Space Station

There is now ample evidence to confirm that dysregulation of various immune system parameters, including leukocyte distribution, functional capacity of various cellular populations, and cytokine production profiles, is associated with spaceflight. This phenomenon was recently found to persist for the duration of a 6-month deployment to the International Space Station (ISS). In astronauts, the reactivation of latent herpesviruses has been correlated with immune system alterations. There is a common perception that astronauts do not experience illness during flight. This may be due to the (appropriately) restricted nature of an astronaut’s confidential medical information, or related to successful preflight quarantine and living in a quasi-isolation chamber. Nevertheless, astronauts do indeed experience varying degrees of illness. For this case report, we track symptomology, medication use, and research immunology findings for an ISS astronaut during a typical 6-month flight onboard ISS. This particular crewmember experienced a chronic rash, which occurred early and never fully resolved during the course of the mission. We overlay observed symptoms with major mission events, to highlight a potential relationship between clinical outcomes and mission stress. Parallel data from a biomedical research investigation are presented in this article’s Online Repository at www.jaci-inpractice.org. This ISS mission consisted of 191 flight days from launch to landing. Occurring during this ISS deployment were the dockings of 3 Space Shuttle missions, 2 Soyuz vehicles, 2 Russian “Progress” cargo vehicles, and 1 European Space Agency “ATV” cargo vehicle. The crewmember participated in 5 EVAs (extravehicular activities—spacewalks). There were also 12 additional EVAs or spacewalks that occurred during Shuttle docked operations. These additional EVAs were performed by Shuttle crewmembers, but required support and guidance by ISS crewmembers. The crewmember also supported other significant on-orbit operations such as relocation of modules and hardware installation. All major mission events, including vehicle docking and/or undocking, and EVAs are represented in Figure 1. Crewmember on-orbit blood, saliva, and urine sample collections are also indicated, as are crewmember circadian rhythm shifts. Generally, these rhythm shifts are purposeful and preplanned by ground control to support mission operations. Other relevant medical data such as symptomatic incidents or periods of relevant medication usage are also represented. Using this information, clinical findings and research data may be interpreted in the context of the mission schedule and on-orbit events. The case study crewmember experienced no unusual symptoms, other than those associated with normal adaptation to microgravity, before flight day 17. The crewmember then developed a rash, possibly dermatitis, on flight day 17. This corresponded to the first period of notable stress in the mission, coinciding with a Shuttle docking and an extremely high workload (Figure 1). The rash presented red, bumpy, and very itchy areas on the back and neck (Figure 2). Coinciding with the rash development was the appearance of eye and upper respiratory rhinitis symptoms, primarily sneezing and itchy, watery eyes. It is noteworthy that the crewmember does not experience terrestrial allergies of any kind and had never previously required any antihistamine medication. The occurrence of symptoms and rash severity over the general mission timeline is presented in Figure 1. Rash severity was tracked on a relative 1-10 scale between the crewmember and flight surgeon, with guidance having been provided to the crewmember to grade based on discomfort and operational impact. The crewmember treated the rash with hydrocortisone cream as needed at the crewmembers’ discretion. The use of this medication was not recorded daily, but per the crewmember, it was used heavily for the duration of the mission. The crewmember was also prescribed fluconazole on mission day 22, on the possibility that the rash could have fungal component. The antifungal had no beneficial effect on the rash. Near to the Shuttle undocking on flight day 27, there was general improvement in the rash severity, and the rhinitis symptoms were treated with, and responded to, an oral antihistamine. A worsening of rash symptoms occurred around mission day 33, immediately after an EVA, and coinciding with a period of notable on-orbit operations. Terbinafine cream was prescribed for use as needed on flight day 34. The severity of the rash generally diminished to 1-2þ by mission day 48, after 2 more EVAs. On flight day 69, the most challenging EVA (per the crewmember description) occurred. On mission day 71, a crewmate received some distressing personal news regarding a death in the family. This event was a psychological stressor for the entire crew. On mission day 73, the rash flared to its worst point in the 6-month mission, described by the crewmember as 10þ. We retrospectively anticipate, based on rash locations, appearance, and discomfort and/or itch, that this level of severity would correspond to approximately 30-37 on the Scoring Atopic Dermatitis scale. At this point, the hydrocortisone cream was exhausted. Triamcinolone acetonide cream was used and was found to be ineffective. A methylprednisolone steroid dosepack was prescribed, and the rash improved during the initial period of the 6-day treatment, with return of symptoms on the fifth day of the tapering. A 30 mg prednisone dose was initiated with a much

Spaceflight Nutrition Research: Platforms and Analogs

Conducting research during actual or simulated weightlessness is a challenging endeavor, where even the simplest activities may present significant challenges. This article reviews some of the potential obstacles associated with performing research during space flight and offers brief descriptions of current and previous space research platforms and ground-based analogs, including those for human, animal, and cell-based research. This review is intended to highlight the main issues of space flight research analogs and leave the specifics for each physiologic system for the other papers in this section.