Mobilization studies in complement-deficient mice reveal that optimal AMD3100 mobilization of hematopoietic stem cells depends on complement cascade activation by AMD3100-stimulated granulocytes

Stem Cell Institute at James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA.
Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K (Impact Factor: 10.43). 03/2010; 24(3):573-82. DOI: 10.1038/leu.2009.271
Source: PubMed


We reported that complement cascade (CC) becomes activated in bone marrow (BM) during mobilization of hematopoietic stem/progenitor cells (HSPCs) induced by granulocyte colony-stimulating factor (G-CSF) and C5 cleavage has an important function in optimal egress of HSPCs. In this work, we explored whether CC is involved in mobilization of HSPCs induced by the CXCR4 antagonist, AMD3100. To address this question, we performed mobilization studies in mice that display a defect in the activation of the proximal steps of CC (Rag(-/-), severe combined immune deficient (SCID), C2.Cfb(-/-)) as well as in mice that do not activate the distal steps of CC (C5(-/-)). We noticed that proximal CC activation-deficient mice (above C5 level), in contrast to distal step CC activation-deficient C5(-/-) ones, mobilize normally in response to AMD3100 administration. We hypothesized that this discrepancy in mobilization could be explained by AMD3100-activating C5 in Rag(-/-), SCID, and C2.Cfb(-/-) animals in a non-canonical mechanism involving activated granulocytes. To support this, granulocytes (i) first egress from BM and (ii) secrete several proteases that cleave/activate C5 in response to AMD3100. We conclude that AMD3100-directed mobilization of HSPCs, similarly to G-CSF-induced mobilization, depends on activation of CC; however, in contrast to G-CSF, AMD3100 activates the distal steps of CC directly at the C5 level. Overall, these data support that C5 cleavage fragments and distal steps of CC activation are required for optimal mobilization of HSPCs.

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Available from: Marcin Wysoczynski, Aug 06, 2014
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    • "Hematopoietic stem/progenitor cells (HSPCs) escape their BM niche in response to chemotactic gradients and can be detected in the PB under steady state conditions [7]. Numerous factors have been shown to be responsible for HSPC mobilization including strenuous exercise [8], tissue, or organ injury (including ischemic cardiac events) [9, 10] and may significantly increase in circulation after administration of pharmacological agents [11, 12]. BMSPCs have multifaceted roles in an adult organism most importantly being involved in lymphohematopoiesis [7] and immune surveillance [13]. "
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    ABSTRACT: Despite significant advances in medical therapy and interventional strategies, the prognosis of millions of patients with acute myocardial infarction (AMI) and ischemic heart disease (IHD) remains poor. Currently, short of heart transplantation with all of its inherit limitations, there are no available treatment strategies that replace the infarcted myocardium. It is now well established that cardiomyocytes undergo continuous renewal, with contribution from bone marrow (BM)-derived stem/progenitor cells (SPCs). This phenomenon is upregulated during AMI by initiating multiple innate reparatory mechanisms through which BMSPCs are mobilized towards the ischemic myocardium and contribute to myocardial regeneration. While a role for the SDF-1/CXCR4 axis in retention of BMSPCs in bone marrow is undisputed, its exclusive role in their mobilization and homing to a highly proteolytic microenvironment, such as the ischemic/infarcted myocardium, is currently being challenged. Recent evidence suggests a pivotal role for bioactive lipids in the mobilization of BMSPCs at the early stages following AMI and their homing towards ischemic myocardium. This review highlights the recent advances in our understanding of the mechanisms of stem cell mobilization, provides newer evidence implicating bioactive lipids in BMSPC mobilization and differentiation, and discusses their potential as therapeutic agents in the treatment of IHD.
    01/2014; 2014:653543. DOI:10.1155/2014/653543
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    • "Since then, several factors have been reported to sensitize the responsiveness of HSPCs to a SDF-1 gradient. These factors include elements of innate immunity, such as cleavage fragments of the complement cascade molecule C3 (Reca et al., 2003), cationic antimicrobial peptides, such as cathelicidin (LL-37) and ␤-defensins (Lee et al., 2010–Lehrer, 2004), and PGE2, a member of the eicosanoid family (Goichberg et al., 2006–Hoggatt et al., 2009). Several arms of the innate immunity system are shown to be involved in regulation of HSPC egress and mobilization, including the complement system and neutrophil activation, as described herein. "
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    ABSTRACT: Hematopoietic stem and progenitor cells (HSPCs) continuously egress out of the bone marrow (BM) to the circulation under homeostatic conditions. Their enhanced recruitment to the periphery in response to exogenous stimulation is a process, termed mobilization. HSPC mobilization is induced clinically or experimentally in animal models by a wide variety of agents, such as cytokines (e.g. G-CSF), chemotherapeutic agents (e.g. cyclophosphamide) and small molecules (e.g. the CXCR4 antagonist AMD3100). The major source for clinical transplantation protocols is via peripheral blood (PB) mobilization of BM derived HSPCs. Thus, deciphering mechanisms that regulate HSPC motility can be utilized for the development of improved mobilization regimens. The chemokine stromal derived factor-1 (SDF-1, also termed CXCL12) and its major receptor CXCR4 are crucial in mediating both retention and mobilization of HSPCs, and this chapter will emphasize its recently revealed roles in directing steady state egress and rapid mobilization. Loss of retention is mediated by disruption of adhesion interactions, such as those mediated by integrins and CD44, and intrinsic signaling pathways such as Rho GTPases dependent signaling. Pivotal roles for the hemostatic fibrinolytic and stress-induced proteolytic enzymatic machineries in regulating HSPC recruitment are also discussed. Nevertheless, breakdown of adhesion interactions and activity of proteases are only part of the story, as accumulating evidences present the BM microenvironment, not only as maintaining HSPC quiescence and proliferation, but also as controlling HSPC retention and motility. Differentiating myeloid cells, bone remodeling by osteoblasts and osteoclasts, stimuli of the innate immunity as well as of the nervous system, including signals emanating the circadian clock, highly regulate various aspects of HSPC function, including egress, recruitment and mobilization. This review aims at presenting up to-date results concerning the dynamic interplay between the BM microenvironment and the HSPCs, focusing on molecular mechanisms that lead eventually to mobilization of HSPCs from the BM into the circulation.
    StemBook, 12/2012; Harvard Stem Cell Institute.
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    • "In addition, leukapheresis products which are enriched in activated granulocytes are known to release several cationic peptides and activate complement cascades [13]. We recently noted that activated granulocyte-derived cationic peptide positively primes responsiveness of murine HSPCs to a CXCL12 gradient [25]. "
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    ABSTRACT: Current strategies to accelerate hematopoietic reconstitution after transplantation include transplantation of greater numbers of hematopoietic stem/progenitor cells (HSPCs) or ex vivo expansion of harvested HSPCs before transplant. However, the number of cells available for transplantation is usually low, and strategies to expand HSPCs and maintain equivalent engraftment capability ex vivo are limited. We noted that activated granulocyte-derived cationic peptides positively primed responsiveness of HSPCs to a CXCL12 gradient. Accordingly, we noted that accelerated homing/engraftment of β-defensin-2, a well-known antimicrobial cationic peptide, primed bone marrow nucleated cells (BMNCs) compared to normal BMNCs after transplantation into lethally irradiated recipients. We envision that small cationic peptides, which primarily possess antimicrobial functions and are harmless to mammalian cells, could be applied to prime HSPCs before transplantation. This novel approach would be particularly important in cord blood transplantation, where the number of HSPCs available for transplantation is usually limited.
    06/2011; 27(2):133-40. DOI:10.5625/lar.2011.27.2.133
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