Wojciech Marlicz

Novel insight into stem cell mobilization-plasma sphingosine-1-phosphate is a major chemoattractant that directs the egress of hematopoietic stem progenitor cells from the bone marrow and its level in peripheral blood increases during mobilization due to activation of complement cascade/membrane attack complex.

The complement cascade (CC) becomes activated and its cleavage fragments play a crucial role in the mobilization of hematopoietic stem/progenitor cells (HSPCs). Here, we sought to determine which major chemoattractant present in peripheral blood (PB) is responsible for the egress of HSPCs from the bone marrow (BM). We noticed that normal and mobilized plasma strongly chemoattracts HSPCs in a stromal-derived factor-1 (SDF-1)-independent manner because (i) plasma SDF-1 level does not correlate with mobilization efficiency; (ii) the chemotactic plasma gradient is not affected in the presence of AMD3100 and (iii) it is resistant to denaturation by heat. Surprisingly, the observed loss of plasma chemotactic activity after charcoal stripping suggested the involvement of bioactive lipids and we focused on sphingosine-1-phosphate (S1P), a known chemoattracant of HSPCs. We found that S1P (i) creates in plasma a continuously present gradient for BM-residing HSPCs; (ii) is at physiologically relevant concentrations a chemoattractant several magnitudes stronger than SDF-1 and (iii) its plasma level increases during mobilization due to CC activation and interaction of the membrane attack complex (MAC) with erythrocytes that are a major reservoir of S1P. We conclude and propose a new paradigm that S1P is a crucial chemoattractant for BM-residing HSPCs and that CC through MAC induces the release of S1P from erythrocytes for optimal egress/mobilization of HSPCs.

CD34 + , kit + , rhodamine123 low phenotype identifies a marrow cell population highly enriched for human hematopoietic stem cells

We hypothesized that human hematopoietic cells displaying a CD34+, kit+, rhodamine123low phenotype would be highly enriched for cells with stem-like properties. To test this hypothesis, we employed fluorescence activated cell sorting (FACS) to isolate cells with this phenotype from normal light density marrow mononuclear cells (MNC). CD34+, kit+, rhodamine123low cells comprised from 0.05–0.01% of the total MNC population. They were small, had scant cytoplasm, and contained nuclei with dense, hyperchromatic chromatin and inconspicuous nucleoli. Additional immunophenotyping revealed that these cells were CD33−, CD38−, CD20−, and glycophorin A−. When plated in semisolid cultures containing optimal concentrations of IL-3, GM-CSF, KL, EPO, IL-6, and IL-1 these cells did not form colonies. However, when cultured over irradiated stromal cells, cobblestone areas were observed to form after 3 weeks, and harvested cells were able to initiate long-term cultures. To further demonstrate that these cells were indeed stem like, we also tested their ability to engraft and mature in immunocompromised (SCID) mice. Irradiated (400 cGy) SCID mice were transplanted with 2 × 103 candidate stem cells which were then injected with recombinant human growth factors every other day. Two months post-transplant the animals were sacrificed. PCR and FACS analysis of marrow and spleen cell samples revealed the presence of cells expressing human CD45 consistent with engraftment of human stem cells and the establishment of murine–human chimerism. Moreover, MNC isolated from transplanted mice formed unambiguously human BFU-E, CFU-GM and B cell colonies when stimulated with the appropriate growth factors. Accordingly, we have identified a relatively rapid and simple mechanism for isolating primitive human hematopoietic cells with stem cell-like properties. We anticipate that this strategy will be useful for experimental and therapeutic applications that require human stem cells in quantity.

Various types of stem cells, including a population of very small embryonic-like stem cells, are mobilized into peripheral blood in patients with Crohn's disease†

Background: Developmentally early cells, including hematopoietic stem progenitor cells (HSPCs), mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs), and very small embryonic‐like stem cells (VSELs), are mobilized into peripheral blood (PB) in response to tissue/organ injury. We sought to determine whether these cells are mobilized into PB in patients with Crohns disease (CD). Methods: Twenty‐five patients with active CD, 20 patients in clinical remission, and 25 age‐matched controls were recruited and PB samples harvested. The circulating CD133+/Lin−/CD45+ and CD34+/Lin−/CD45+ cells enriched for HSPCs, CD105+/STRO‐1+/CD45− cells enriched for MSCs, CD34+/KDR+/CD31+/CD45−cells enriched for EPCs, and small CXCR4+CD34+CD133+ subsets of Lin−CD45− cells that correspond to the population of VSELs were counted by fluorescence‐activated cell sorting (FACS) and evaluated by direct immunofluorescence staining for pluripotency embryonic markers and by reverse‐transcription polymerase chain reaction (RT‐PCR) for expression of messenger (m)RNAs for a panel of genes expressed in intestine epithelial stem cells. The serum concentration of factors involved in stem cell trafficking, such as stromal derived factor‐1 (SDF‐1), vascular endothelial growth factor (VEGF), and hepatocyte growth factor (HGF) were measured by enzyme‐linked immunosorbent assay (ELISA). Results: Our data indicate that cells expressing markers for MSCs, EPCs, and small Oct‐4+Nanog+SSEA‐4+CXCR4+lin−CD45− VSELs are mobilized into PB in CD. The mobilized cells also expressed at the mRNA level genes playing a role in development and regeneration of gastrointestinal epithelium. All these changes were accompanied by increased serum concentrations of VEGF and HGF. Conclusions: CD triggers the mobilization of MSCs, EPCs, and VSELs, while the significance and precise role of these mobilized cells in repair of damaged intestine requires further study. (Inflamm Bowel Dis 2012;)

The bone marrow-expressed antimicrobial cationic peptide LL-37 enhances the responsiveness of hematopoietic stem progenitor cells to an SDF-1 gradient and accelerates their engraftment after transplantation

We report that the bone marrow (BM) stroma-released LL-37, a member of the cathelicidin family of antimicrobial peptides, primes/increases the responsiveness of murine and human hematopoietic stem/progenitor cells (HSPCs) to an α-chemokine stromal-derived factor-1 (SDF-1) gradient. Accordingly, LL-37 is upregulated in irradiated BM cells and enhances the chemotactic responsiveness of hematopoietic progenitors from all lineages to a low physiological SDF-1 gradient as well as increasing their (i) adhesiveness, (ii) SDF-1-mediated actin polymerization and (iii) MAPKp42/44 phosphorylation. Mice transplanted with BM cells ex vivo primed by LL-37 showed accelerated recovery of platelet and neutrophil counts by ∼3–5 days compared with mice transplanted with unprimed control cells. These priming effects were not mediated by LL-37 binding to its receptor and depended instead on the incorporation of the CXCR4 receptor into membrane lipid rafts. We propose that LL-37, which has primarily antimicrobial functions and is harmless to mammalian cells, could be clinically applied to accelerate engraftment as an ex vivo priming agent for transplanted human HSPCs. This novel approach would be particularly important in cord blood transplantations, where the number of HSCs available is usually limited.

Paracrine proangiopoietic effects of human umbilical cord blood-derived purified CD133+ cells--implications for stem cell therapies in regenerative medicine.

CD133+ cells purified from hematopoietic tissues are enriched mostly for hematopoietic stem/progenitor cells, but also contain some endothelial progenitor cells and very small embryonic-like stem cells. CD133+ cells, which are akin to CD34+ cells, are a potential source of stem cells in regenerative medicine. However, the lack of convincing donor-derived chimerism in the damaged organs of patients treated with these cells suggests that the improvement in function involves mechanisms other than a direct contribution to the damaged tissues. We hypothesized that CD133+ cells secrete several paracrine factors that play a major role in the positive effects observed after treatment and tested supernatants derived from these cells for the presence of such factors. We observed that CD133+ cells and CD133+ cell-derived microvesicles (MVs) express mRNAs for several antiapoptotic and proangiopoietic factors, including kit ligand, insulin growth factor-1, vascular endothelial growth factor, basic fibroblast growth factor, and interleukin-8. These factors were also detected in a CD133+ cell-derived conditioned medium (CM). More important, the CD133+ cell-derived CM and MVs chemoattracted endothelial cells and display proangiopoietic activity both in vitro and in vivo assays. This observation should be taken into consideration when evaluating clinical outcomes from purified CD133+ cell therapies in regenerative medicine.

An intensified systemic trafficking of bone marrow‐derived stem/progenitor cells in patients with pancreatic cancer

Various experimental studies indicate potential involvement of bone marrow (BM)‐derived stem cells (SCs) in malignancy development and progression. In this study, we comprehensively analysed systemic trafficking of various populations of BM‐derived SCs (BMSCs), i.e., mesenchymal, haematopoietic, endothelial stem/progenitor cells (MSCs, HSCs, EPCs respectively), and of recently discovered population of very small embryonic/epiblast‐like SCs (VSELs) in pancreatic cancer patients. Circulating CD133+/Lin−/CD45−/CD34+ cells enriched for HSCs, CD105+/STRO‐1+/CD45− cells enriched for MSCs, CD34+/KDR+/CD31+/CD45− cells enriched for EPCs and small CXCR4+CD34+CD133+ subsets of Lin−CD45− cells that correspond to VSELs were enumerated and sorted from blood samples derived from 29 patients with pancreatic cancer, and 19 healthy controls. In addition, plasma levels of stromal‐derived factor‐1 (SDF‐1), growth/inhibitory factors and sphingosine‐1‐phosphate (S1P; chemoattractants for SCs), as well as, of complement cascade (CC) molecules (C3a, C5a and C5b‐9/membrane attack complex – MAC) were measured. Higher numbers of circulating VSELs and MSCs were detected in pancreatic cancer patients (P < 0.05 and 0.01 respectively). This trafficking of BMSCs was associated with significantly elevated C5a (P < 0.05) and C5b‐9/MAC (P < 0.005) levels together with S1P concentrations detected in plasma of cancer patients, and seemed to be executed in a SDF‐1 independent manner. In conclusion, we demonstrated that in patients with pancreatic cancer, intensified peripheral trafficking of selected populations of BMSCs occurs. This phenomenon seems to correlate with systemic activation of the CC, hepatocyte growth factor and S1P levels. In contrast to previous studies, we demonstrate herein that systemic SDF‐1 levels do not seem to be linked with increased mobilization of stem cells in patients with pancreatic cancer.

Identification of Very Small Embryonic/Epiblast-Like Stem Cells (VSELs) Circulating in Peripheral Blood During Organ/Tissue Injuries

We have identified in adult tissues a population of pluripotent very small embryonic/epiblast-like stem cells (VSELs) that we hypothesize are deposited at onset of gastrulation in developing tissues and play an important role as backup population of tissue-specific/committed stem cells. We envision that during steady-state conditions these cells may be involved in tissue rejuvenation and in processes of regeneration/repair after organ injuries. VSELs similarly as epiblast-derived migrating primordial germ cells change the epigenetic signature of some of the imprinted genes and therefore remain quiescent in adult tissues. These epigenetic changes in methylation status of imprinted genes prevent them also from teratoma formation. Mounting evidence indicates that VSELs are mobilized into peripheral blood during tissue/organ injuries and enumeration of these cells may be of prognostic value (e.g., in stroke or heart infarct). In this chapter, we will present FACS-based strategies to detect and enumerate these cells in human peripheral blood and umbilical cord blood.

Complement system activation and endothelial dysfunction in patients with age‐related macular degeneration (AMD): possible relationship between AMD and atherosclerosis

Age‐related macular degeneration (AMD) shares several pathological and epidemiological similarities with systemic atherosclerosis (AS). First, an association between AS and AMD is apparent from the analyses of the histological and biochemical structure of atherosclerotic plaques in the vascular walls and retinal drusen, the hallmark of AMD. Second, there is considerable evidence implicating endothelial dysfunction in the pathogenesis of both disorders, and cellular oxidative stress appears to be a common denominator underlying this process. Moreover, there are observations that the complement system (CS) triggering inflammatory response contributes to the onset and advancement of both diseases. The CS plays a role in the generation of drusen and neovascularization in AMD as well as in vascular endothelium activation, cell damage and ultimately atherosclerotic plaque formation in the course of systemic arteriosclerosis. It is widely recognized that both AMD and AS are not only related to local stimulation of the CS, but also result in its systemic activation. In addition, a specific Y402H polymorphism of the complement inhibitor factor H has been found to be associated with the incidence of both AMD and AS. Here, we propose a linking hypothesis between CS activation, endothelial dysfunction and the pathogenesis of two common and age‐related pathological processes, AS and AMD. We also discuss the potential therapeutic value of pharmacological modulation of CS activation in these disorders.

Nonsteroidal anti-inflammatory drugs, proton pump inhibitors, and gastrointestinal injury: contrasting interactions in the stomach and small intestine.

Nonsteroidal anti-inflammatory drugs (NSAIDs) and proton pump inhibitors (PPIs) are among the most frequently prescribed groups of drugs worldwide. The use of NSAIDs is associated with a high number of significant adverse effects. Recently, the safety of PPIs has also been challenged. Capsule endoscopy studies reveal that even low-dose NSAIDs are responsible for gut mucosal injury and numerous clinical adverse effects, for example, bleeding and anemia, that might be difficult to diagnose. The frequent use of PPIs can exacerbate NSAID-induced small intestinal injury by altering intestinal microbiota. Thus, the use of PPI is considered to be an independent risk factor associated with NSAID-associated enteropathy. In this review, we discuss this important clinical problem and review relevant aspects of epidemiology, pathophysiology, and management. We also present the hypothesis that even minor and subclinical injury to the intestinal mucosa can result in significant, though delayed, metabolic consequences, which may seriously affect the health of an individual. PubMed was searched using the following key words (each key word alone and in combination): gut microbiota, microbiome, non-steroidal anti inflammatory drugs, proton pump inhibitors, enteropathy, probiotic, antibiotic, mucosal injury, enteroscopy, and capsule endoscopy. Google engine search was also carried out to identify additional relevant articles. Both original and review articles published in English were reviewed.

Minimal hepatic encephalopathy does not impair health-related quality of life in patients with cirrhosis: a prospective study.

Background: Minimal hepatic encephalopathy (HE) is a serious complication of cirrhosis; however, the impact of minimal HE on health‐related quality of life (HRQoL) remains controversial. The Psychometric Hepatic Encephalopathy Score (PHES) remains a ‘gold standard’ for the assessment of minimal HE, but its results clearly differ between studied populations.