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Depletion and Reconstitution of Macrophages in Mice
Published on: August 1, 2012
Macrophage depletion induced by clodronate-loaded erythrocytes
Luigia Rossi1, Sonja Serafini, Antonella Antonelli
1Institute of Biochemistry G. Fornaini, University of Urbino, 61029 Urbino (PU), Italy.
Insights
Erythrocytes loaded with clodronate effectively deplete macrophages, offering a new method for transiently suppressing macrophage functions in research and potential therapeutic applications.
Area of Science:
- Immunology
- Cell Biology
- Biomedical Engineering
Background:
- Macrophages play a critical role in various diseases.
- Transient suppression of macrophage function is a potential therapeutic strategy.
- Liposome-encapsulated bisphosphonate clodronate is a known method for macrophage depletion.
Purpose of the Study:
- To investigate the efficacy of erythrocytes loaded with clodronate for macrophage depletion.
- To evaluate the in vitro and in vivo performance of clodronate-loaded erythrocytes.
Main Methods:
- Clodronate encapsulation into human and murine erythrocytes via hypotonic dialysis, isotonic resealing, and reannealing.
- In vitro assessment of macrophage adherence capacity after treatment with engineered erythrocytes.
- In vivo evaluation of macrophage depletion in Swiss and C57BL/6 mice.
Main Results:
- Engineered erythrocytes reduced human macrophage adherence by 50% at 13 days post-treatment.
- Murine peritoneal macrophages showed a 67% reduction in adhesion 48 hours post-treatment.
- In vivo studies demonstrated significant reductions in peritoneal, spleen, and liver macrophages.
Conclusions:
- Clodronate-loaded erythrocytes effectively deplete macrophages, offering a novel delivery system.
- This method provides transient suppression of macrophage functions for research and biomedical applications.
- Engineered erythrocytes represent a promising alternative to liposomal clodronate for macrophage modulation.
Abstract:
Given the important role of macrophages in various disorders, the transient and organ specific suppression of their functions may benefit some patients. Until now, liposome-encapsulated bisphosphonate clodronate has been extensively proposed to this end. In this paper, we demonstrate that erythrocytes loaded with clodronate can also be effective in macrophage depletion. Here, clodronate was encapsulated in erythrocytes through hypotonic dialysis, isotonic resealing and reannealing to final concentrations of 4.1 +/- 0.4 and 10.1 +/- 0.8 micromol/ml of human and murine erythrocytes, respectively. The ability of clodronate-loaded erythrocytes to deplete macrophages was evaluated both in vitro and in vivo. In vitro studies on human macrophages showed that a single administration of engineered erythrocytes was able to reduce cell adherence capacity in a time-dependent manner, reaching 50 +/- 4% reduction, 13 days post treatment. The administration of loaded erythrocytes to cultures of murine peritoneal macrophages was able to reduce macrophage adhesion 67 +/- 3%, 48 h post treatment. In vivo, the ability of clodronate-loaded erythrocytes to deplete macrophages was evaluated both in Swiss and C57BL/6 mice. Swiss mice received 125 microg of clodronate through erythrocytes and 6 days post treatment 69 +/- 7% reduction in the number of adherent peritoneal macrophages and 75 +/- 5% reduction in number of spleen macrophages were observed. C57BL/6 mice received 220 microg clodronate by RBC and 3 and 8 days post treatment 65 +/- 7% reduction in the number of spleen macrophages and the complete depletion of liver macrophages were obtained. In summary, our results indicate that clodronate selectively targeted to the phagocytic cells by a single administration of engineered erythrocytes is able to deplete macrophages, even if not completely. The transient suppression of macrophage functions through clodronate-loaded erythrocytes can be used in many biomedical phenomena and research applications.
