The Journal of Neuroscience, May 15, 2001, 21(10):3401-3408
Macrophages Are Eliminated from the Injured Peripheral Nerve via
Local Apoptosis and Circulation to Regional Lymph Nodes and the
Spleen
Tanja
Kuhlmann1,
Andreas
Bitsch2,
Christine
Stadelmann1,
Heike
Siebert1, and
Wolfgang
Brück1
1 Department of Neuropathology, Charité, Campus
Virchow-Klinikum, 13353 Berlin, Germany, and 2 Department
of Neurology, University of Göttingen, 37075 Göttingen,
Germany
The present study investigated the fate of macrophages in
peripheral nerves undergoing Wallerian degeneration, especially their
disappearance from the injured nerves after phagocytosis of axonal and
myelin debris. Wallerian degeneration was induced in adult male C57Bl/6
mice by transecting the right sciatic nerve. Five days after
transection, the male sciatic nerves were transplanted into female
recipient mice by placing them exactly parallel to the host sciatic
nerves. Nerves of the female recipient mice were also transected to
induce breakdown of the blood-nerve barrier in the host animal.
Apoptosis was assessed by morphological, immunohistochemical (activated
caspase-3), and molecular (DNA fragmentation) methods in transplanted,
recipient, and in control nerves. A subpopulation of macrophages within
the degenerating nerves died locally by apoptosis in each experiment.
The fate of the male macrophages within the transplanted nerves and the
host organism was investigated by in situ hybridization
with a Y-chromosome-specific DNA probe (145SC5). In situ
hybridization specifically stained cells within the transplanted male
nerve. Y-chromosome-positive cells were detected not only inside the
transplanted nerve, but also inside the female host nerve, the
perineurial tissue, the local perineurial blood vessels, draining lymph
nodes and the spleen of the female host, suggesting hematogenous as
well as lymphatic elimination of macrophages from the injured nerve.
These data indicate that local apoptosis and systemic elimination via
circulation to the local lymph nodes and the spleen are involved in the
disappearance of macrophages from the injured peripheral nervous system.
Key words:
macrophage; elimination; nervous system; apoptosis; migration; Y-chromosome probe; transplantation
Copyright © 2001 Society for Neuroscience 0270-6474/01/21103401-08$05.00/0