Dependence of human stem cell engraftment and repopulation of NDO/SCID mice on CXCR4
Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel. Science
(Impact Factor: 33.61).
Stem cell homing and repopulation are not well understood. The chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 were found to be critical for murine bone marrow engraftment by human severe combined immunodeficient (SCID) repopulating stem cells. Treatment of human cells with antibodies to CXCR4 prevented engraftment. In vitro CXCR4-dependent migration to SDF-1 of CD34+CD38-/low cells correlated with in vivo engraftment and stem cell function. Stem cell factor and interleukin-6 induced CXCR4 expression on CD34+ cells, which potentiated migration to SDF-1 and engraftment in primary and secondary transplanted mice. Thus, up-regulation of CXCR4 expression may be useful for improving engraftment of repopulating stem cells in clinical transplantation.
Available from: Dominique Bonnet
- "CXCL12 binding to CXCR4 enhances the affinity of integrins , in particular VLA-4, which mediates HSC cell adhesion in the niche (Hartmann et al., 2008; Peled et al., 1999a, 2000). Impairment of integrin or CXCR4/SDF1 expression or neutralization of their function by antibody treatment is known to be associated with reduced HSC homing (Kollet et al., 2001; Peled et al., 1999b; Qian et al., 2006; Wagers et al., 2002). Treatment with the CXCR4 receptor antagonist, AMD3100, is a potent mobilizing agent (Broxmeyer et al., 2005; Liles et al., 2003), and inhibition of VLA-4 (via Bio5192, a small molecule inhibitor) alone and in combination with CXCR4 antagonists was shown to mobilize long-term HSPCs to the periphery more effectively than with AMD3100 alone (Bonig et al., 2009; Ramirez et al., 2009; Leone et al., 2003). "
[Show abstract] [Hide abstract]
ABSTRACT: Despite advances in our understanding of interactions between mouse hematopoietic stem cells (HSCs) and their niche, little is known about communication between human HSCs and the microenvironment. Using a xenotransplantation model and intravital imaging, we demonstrate that human HSCs display distinct motile behaviors to their hematopoietic progenitor cell (HPC) counterparts, and the same pattern can be found between mouse HSCs and HPCs. HSCs become significantly less motile after transplantation, while progenitor cells remain motile. We show that human HSCs take longer to find their niche than previously expected and suggest that the niche be defined as the position where HSCs stop moving. Intravital imaging is the only technique to determine where in the bone marrow stem cells stop moving, and future analyses should focus on the environment surrounding the HSC at this point.
Available from: Thavasyappan Thambi
- "It was hypothesized that the delivery of molecules which regulates the microenvironment in the brain infarct can increase the degree and duration of neurogenesis and angiogenesis after stroke. Among the milieu of chemicals expressed in the injured microenvironment , stromal cell-derived factor-1a (SDF-1a or CXCL12a) and its unique receptor chemokine CXC motif receptor (CXCR4) is a candidate molecule that modulates the microenvironment in the infarcted brain  . SDF-1a is a major chemoattractant molecule for neural stem cells (NSCs), endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs), and is recognized as a prime candidate in neurorestorative interventions. "
[Show abstract] [Hide abstract]
ABSTRACT: In this study, we hypothesized that the delivery of molecules that regulate the microenvironment after a cerebral infarction can influence regeneration potential after a stroke. Stromal cell-derived factor-1α (SDF-1α) is a chemoattractant molecule that plays a pivotal role in recruiting endothelial progenitor cells (EPCs) to the infarct region after stroke. Increased SDF-1α expression leads to increased EPCs homing at the infarct region and induces neurogenesis, angiogenesis, neuroprotection, and stem cell homing. Thus, we evaluated the effects of targeted delivery of SDF-1α using a pH-sensitive polymer poly (urethane amino sulfamethazine) (PUASM), a synthetic macromolecule with potential for targeted drug delivery in acidic conditions, to enhance therapeutic neurogenesis and angiogenesis in a rat model of permanent middle cerebral artery occlusion. A dual ionic pH-sensitive copolymer PUASM-based random copolymer was designed and synthesized for the controlled release of SDF-1α in stroke. Owing to the unique characteristics of PUASM, it exhibited a dual ionic pH-sensitive property in an aqueous solution. At pH 8.5, the copolymer exhibited a negative charge and was water soluble. Interestingly, when the pH decreased to 7.4, PUASM could form a micelle and encapsulate protein effectively via the ionic interaction between a negatively charged polymer and a positively charged protein. At pH 5.5, the ionization of tertiary amines led to the disassembly of the micellar structure and released the protein rapidly. Then, we investigated the effect of systemic administration of SDF-1α-loaded pH-sensitive polymeric micelles in a stroke induced rat model. An enzyme-linked immunosorbent assay showed increased expression of SDF-1α in the ischemic region, indicating that the pH-sensitive micelles effectively delivered SDF-1α into the ischemic region. In order to observe the biodistribution of SDF-1α in the ischemic region, it was labeled with the near-infrared dye, Cy5.5. Optical imaging showed that the Cy5.5 signal increased in the infarct region 24 h after administration. Immunohistochemistry data showed that targeted delivery of SDF-1α enhanced neurogenesis and angiogenesis, but did not influence cell survival or inflammation. These observations suggest that SDF-1α-loaded pH-sensitive polymeric micelles can be used as pH-triggered targeting agents and can effectively modify the microenvironment to increase innate neurorestorative processes.
Copyright © 2015 Elsevier Ltd. All rights reserved.
Available from: Ramesh C Nayak
- "Dysregulation of stromal components of the HP niches within the BM, such as changes in the levels of chemokines from osteoblasts (Obs) and other mesenchymal cells, has been associated with HP egress (Ding and Morrison, 2013; Greenbaum et al., 2013; Mé ndez-Ferrer et al., 2010; Omatsu et al., 2010; Petit et al., 2002; Sugiyama et al., 2006; Visnjic et al., 2004). Specifically, the deletion of the major hematopoietic stem cell and progenitor (HSC/P) traffic regulator Cxcl12 (Peled et al., 1999, 2000) from Cxcl12-abundant reticular cells and Ob results in constitutive HP mobilization and a loss of B-lymphoid progenitors, whereas their HSC function is normal (Greenbaum et al., 2013). Physiological regulation of these mesenchymal components modulates HP trafficking and is afforded by several mechanisms, including signals derived from BM-resident macrophages (MFs) (Casanova-Acebes et al., 2013; Chow et al., 2011; Christopher et al., 2011; Winkler et al., 2010). "
[Show abstract] [Hide abstract]
ABSTRACT: In the bone marrow (BM), hematopoietic progenitors (HPs) reside in specific anatomical niches near osteoblasts (Obs), macrophages (MΦs), and other cells forming the BM microenvironment. A connection between immunosurveillance and traffic of HP has been demonstrated, but the regulatory signals that instruct the immune regulation of HP circulation are unknown. We discovered that the BM microenvironment deficiency of p62, an autophagy regulator and signal organizer, results in loss of autophagic repression of macrophage contact-dependent activation of Ob NF-κB signaling. Consequently, Ob p62-deficient mice lose bone, Ob Ccl4 expression, and HP chemotaxis toward Cxcl12, resulting in egress of short-term hematopoietic stem cells and myeloid progenitors. Finally, Ccl4 expression and myeloid progenitor egress are reversed by deficiency of the p62 PB1-binding partner Nbr1. A functional "MΦ-Ob niche" is required for myeloid progenitor/short-term stem cell retention, in which Ob p62 is required to maintain NF-κB signaling repression, osteogenesis, and BM progenitor retention.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.