Neutropenia impairs venous thrombosis resolution in the rat.
OBJECTIVE
Neutrophil influx is one of the first events in a formed deep venous thrombosis (DVT), but whether these cells are active participants in the resolution process is not clear. This study tests the hypothesis that neutrophils (PMN) are active participants in DVT resolution.


METHODS
Thrombosis was induced by inferior vena caval (IVC) ligation in male Sprague-Dawley rats, and rats were sacrificed at 2, 4, or 7 days for evaluation of the thrombus. Neutropenia was induced by rabbit anti-rat PMN serum, and controls received rabbit serum. Venography was performed at the 7-day time point. Immunohistochemical staining was performed to quantify intrathrombus PMNs and monocytes, and the myeloperoxidase (MPO) assay was performed to assess intrathrombus neutrophil activity. Intrathrombus concentrations of kerotinocyte cytokine (KC), macrophage inflammatory protein-2 (MIP-2), gamma interferon inducible protein-10 (IP-10), macrophage inflammatory protein-1 alpha (MIP-1 alpha), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor (TNF)-alpha were quantified by enzyme immunoassay at each time point and normalized to total protein. Total collagen was determined at day 7.


RESULTS
Peripheral blood smears showed a 94% PMN reduction at 2 days (P <.05), recovering to 44% of control at 7 days. Intrathrombus PMNs were significantly lower in neutropenic rats at 2 and 4 days, but there were no differences in intrathrombus monocytes. The MPO assay confirmed reduced neutrophil activity at 4 days. Thrombi from neutropenic rats were larger at 2 and 7 days compared with controls. In vivo thrombus area at 7 days as assessed by venography was also greater in neutropenic rats as compared with controls. The intrathrombus KC concentration was increased more than 20-fold in the neutropenic rats at 2 days, but there were no significant differences in other intrathrombus chemokines. Finally, intrathrombus collagen was increased over threefold in neutropenic rats as compared with controls.


CONCLUSIONS
Neutropenia impairs DVT resolution by several measures, most likely by altering normal fibrinolytic activity and thrombus collagen turnover.
Varma
Manu R
MR
Department of Surgery, University of Michigan Medical School, Ann Arbor, 48109, USA.
Varga
Andrea J
AJ
Knipp
Brian S
BS
Sukheepod
Pasu
P
Upchurch
Gilbert R
GR
Kunkel
Steven L
SL
Wakefield
Thomas W
TW
Henke
Peter K
PK
D000818:Animals; D018925:Chemokines / Q000276:immunology; D003094:Collagen / Q000276:immunology; D005342:Fibrinolysis / Q000502:physiology; D008297:Male; D009503:Neutropenia / Q000276:immunology* / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function / Q000502:physiology; D012075:Remission, Spontaneous; D013927:Thrombosis / Q000276:immunology / Q000503:physiopathology*; D020246:Venous Thrombosis / Q000276:immunology* / Q000503:physiopathology*
D018925:Chemokines; D003094:Collagen