Investiture of new microvessels within an injured peripheral nerve
trunk may determine the success that the
local environment has in promoting axonal sprouting and regeneration. We
therefore examined microvessel
investment of 24 h–14 d proximal nerve stump preparations in
rat sciatic nerves. The stumps, later destined
to form neuromas, were created by sciatic nerve transection with resection
of distal branches to prevent
distal reinnervation. Microvessels were studied in the proximal stump in
semithin whole mount sections of
nerve and by analysis of India ink perfused microvessel profiles.
Quantitative image analysis was made of
the luminal profiles of vessels perfused with India ink from unfixed
sections of the stumps, contralateral
uninjured nerves and sham-exposed but uninjured nerves. Evidence of
angiogenesis was observed in stumps
7 d after transection, indicated by a rise in the total numbers of
perfused microvessels and in the numbers of
2–6 μm diameter perfused microvessels. There was a shift
in the histogram of the percentage of perfused
microvessels towards the 2–4 μm range and a reduction in the mean
microvessel luminal area in the stumps.
By 14 d, new microvessels were larger, indicated by an increase in total
luminal area. New microvessels were
prominent in the epineurial connective tissue or between layers of perineurial
cells of former fascicles.
Microvessels probably share a battery of trophic signals with other proliferating
cellular elements in the
milieu of the injured peripheral nerve trunk.