Macrophage colony-stimulating factor (CSF1) controls monocyte production and maturation and the steady-state size of the liver in pigs.

Kristin A Sauter,Zofia M Lisowski,Sara M Clohisey,Neil A Mabbott,David A Hume,Gemma M Davis,Rachel Young,Elizabeth Magowan,Lindsey A Waddell,Kim M Summers,Lucas Lefevre,Mary Mcculloch

doi:10.1152/ajpgi.00116.2016

Abstract

Macrophage colony-stimulating factor (CSF1) is an essential growth and differentiation factor for cells of the macrophage lineage. To explore the role of CSF1 in steady-state control of monocyte production and differentiation and tissue repair, we previously developed a bioactive protein with a longer half-life in circulation by fusing pig CSF1 with the Fc region of pig IgG1a. CSF1-Fc administration to pigs expanded progenitor pools in the marrow and selectively increased monocyte numbers and their expression of the maturation marker CD163. There was a rapid increase in the size of the liver, and extensive proliferation of hepatocytes associated with increased macrophage infiltration. Despite the large influx of macrophages, there was no evidence of liver injury and no increase in circulating liver enzymes. Microarray expression profiling of livers identified increased expression of macrophage markers, i.e., cytokines such as TNF, IL1, and IL6 known to influence hepatocyte proliferation, alongside cell cycle genes. The analysis also revealed selective enrichment of genes associated with portal, as opposed to centrilobular regions, as seen in hepatic regeneration. Combined with earlier data from the mouse, this study supports the existence of a CSF1-dependent feedback loop, linking macrophages of the liver with bone marrow and blood monocytes, to mediate homeostatic control of the size of the liver. The results also provide evidence of safety and efficacy for possible clinical applications of CSF1-Fc.

Highlights

Native CSF1 has a much shorter half-life and at the same dose had no effect on monocyte-macrophage numbers [21]
CSF1-Fc treatment of macrophages in vitro did not induce proinflammatory cytokines [21] and, in keeping with the lack of intrinsic proinflammatory activity, there was no evidence of any reaction at the sites of injection in any treated animals
We examined the expression of the CSF1R (CD115) using either a recently described monoclonal antibody [39] or labeled CSF1-Fc

Summary

Introduction

Antigen retrieval was performed with proteinase K (Dako S302030) for 10 min. Nonspecific protein binding was blocked using 2.5% goat serum (Vector Laboratories) for 20 min. Endogenous peroxidase activity was blocked using Dako REAL peroxidase blocker (Dako S202386) for 10 min. Sections were incubated for 60 min using mouse anti-pig CD163 (Serotec MCA2311GA) diluted 1/30. Visualization using secondary reagent Dako Envision mouse HRP (Dako K4007) for 40 min followed by DAB MON-APP177) for 10 min and DAB enhancer for 3 min CO7-25) was performed by the R(D)SVS pathology department. The staining was analyzed using Image J (Fiji)

Methods

Results

Conclusion