Uncovering the multifaceted roles played by neutrophils in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a life-saving procedure used for the treatment of selected hematological malignancies, inborn errors of metabolism, and bone marrow failures. The role of neutrophils in alloHSCT has been traditionally evaluated only in the context of their ability to act as a first line of defense against infection. However, recent evidence has highlighted neutrophils as key effectors of innate and adaptive immune responses through a wide array of newly discovered functions. Accordingly, neutrophils are emerging as highly versatile cells that are able to acquire different, often opposite, functional capacities depending on the microenvironment and their differentiation status. Herein, we review the current knowledge on the multiple functions that neutrophils exhibit through the different stages of alloHSCT, from the hematopoietic stem cell (HSC) mobilization in the donor to the immunological reconstitution that occurs in the recipient following HSC infusion. We also discuss the influence exerted on neutrophils by the immunosuppressive drugs delivered in the course of alloHSCT as part of graft-versus-host disease (GVHD) prophylaxis. Finally, the potential involvement of neutrophils in alloHSCT-related complications, such as transplant-associated thrombotic microangiopathy (TA-TMA), acute and chronic GVHD, and cytomegalovirus (CMV) reactivation, is also discussed. Based on the data reviewed herein, the role played by neutrophils in alloHSCT is far greater than a simple antimicrobial role. However, much remains to be investigated in terms of the potential functions that neutrophils might exert during a highly complex procedure such as alloHSCT.     

PEG hydrogel degradation and the role of the surrounding tissue environment

Poly(ethylene glycol) (PEG)‐based hydrogels are extensively used in a variety of biomedical applications, due to ease of synthesis and tissue‐like properties. Recently there have been varied reports regarding PEG hydrogel's degradation kinetics and in vivo host response. In particular, these studies suggest that the surrounding tissue environment could play a critical role in defining the inflammatory response and degradation kinetics of PEG implants. In the present study we demonstrated a potential mechanism of PEG hydrogel degradation, and in addition we show potential evidence of the role of the surrounding tissue environment on producing variable inflammatory responses. Copyright © 2013 John Wiley & Sons, Ltd.     

Rapid‐onset clinical and mechanistic effects of anti‐C5aR treatment in the mouse collagen‐induced arthritis model

Preclinical evidence supports targeting the C5a receptor (C5aR) in rheumatoid arthritis (RA). To support ongoing clinical development of an anti‐C5aR monoclonal antibody, we have investigated for the first time the mechanism of action and the pharmacodynamics of a blocking anti‐murine C5aR (anti‐mC5aR) surrogate antibody in mouse collagen‐induced arthritis (CIA). First, efficacy was demonstrated in a multiple‐dose treatment study. Almost complete inhibition of clinical disease progression was obtained, including reduced bone and cartilage destruction in anti‐mC5aR‐treated mice. Then, the mechanism of action was examined by looking for early effects of anti‐mC5aR treatment in single‐dose treatment studies. We found that 48 h after single‐dose treatment with anti‐mC5aR, the neutrophil and macrophage infiltration into the paws was already reduced. In addition, several inflammatory markers, including tumour necrosis factor (TNF)‐α, interleukin (IL)‐6 and IL‐17A were reduced locally in the paws, indicating reduction of local inflammation. Furthermore, dose‐setting experiments supported a beneficial clinical effect of dosing above the C5aR saturation level. In conclusion, these preclinical data demonstrated rapid onset effects of antibody blockade of C5aR. The data have translational value in supporting the Novo Nordisk clinical trials of an anti‐C5aR antibody in rheumatoid arthritis patients, by identifying potential biomarkers of treatment effects as well as by providing information on pharmacodynamics and novel insights into the mechanism of action of monoclonal antibody blockade of C5aR.     

Human Neutrophil Defensins and Their Effect on Epithelial Cells

Background: The aims of the present study include: 1) to localize human neutrophil defensin‐1 (HNP‐1) through HNP‐3 in gingiva and in neutrophil extract‐treated epithelial cell monolayers; 2) to determine the effects of HNP‐1 on the epithelial cell viability, attachment, and spreading; and 3) to analyze the effect of HNP‐1 on the bacterial adherence to epithelial cells. Methods: For localization of HNP‐1 through HNP‐3 in gingival tissue and in preincubated cell monolayers, immunohistochemical and immunocytochemical methods were used. Viability and proliferation of epithelial cells were determined with commercial kits after incubating the keratinocytes with different HNP‐1 concentrations (low, 1 to 5 μg/mL; moderate, 10 μg/mL; high, 20 to 50 μg/mL). Attachment and spreading of keratinocytes on fibronectin‐coated surfaces in the presence of HNP‐1 were evaluated under microscope. Attachment of Fusobacterium nucleatum ATCC25586 and Prevotella intermedia ATCC25611 on keratinocytes preincubated with HNP‐1 were determined with a standard antibiotic test. Results: HNP‐1 through HNP‐3 localized in the junctional epithelium of clinically healthy gingiva and in the pocket epithelium of gingiva with periodontitis. When keratinocyte monolayers were incubated with neutrophil extracts, HNP‐1 through HNP‐3 were bound to the periphery of the growing cell colonies. In low HNP‐1 concentrations, the keratinocyte proliferation enhanced. Moderate and high concentrations of HNP‐1 increased the cellular death significantly. HNP‐1 increased the attachment and spreading of keratinocytes on fibronectin‐coated surfaces and bacterial attachment to keratinocytes in a concentration‐dependent manner. Conclusion: HNP‐1 plays a role in the integrity of keratinocytes by stimulating their proliferation, attachment, and spreading, whereas higher doses increase the bacterial attachment and keratinocyte death.