Peripheral facial nerve axotomy in mice causes sprouting of motor axons into perineuronal central white matter: time course and molecular characterization.
Generation of new axonal sprouts plays an important role in neural repair. In the current study, we examined the appearance, composition and effects of gene deletions on intrabrainstem sprouts following peripheral facial nerve axotomy. Axotomy was followed by the appearance of galanin(+) and calcitonin gene-related peptide (CGRP)(+) sprouts peaking at day 14, matching both large, neuropeptide(+) subpopulations of axotomized facial motoneurons, but with CGRP(+) sprouts considerably rarer. Strong immunoreactivity for vesicular acetylcholine transporter (VAChT) and retrogradely transported MiniRuby following its application on freshly cut proximal facial nerve stump confirmed their axotomized motoneuron origin; the sprouts expressed CD44 and alpha7beta1 integrin adhesion molecules and grew apparently unhindered along neighboring central white matter tracts. Quantification of the galanin(+) sprouts revealed a stronger response following cut compared with crush (day 7-14) as well as enhanced sprouting after recut (day 8 + 6 vs. 14; 14 + 8 vs. 22), arguing against delayed appearance of sprouting being the result of the initial phase of reinnervation. Sprouting was strongly diminished in brain Jun-deficient mice but enhanced in alpha7 null animals that showed apparently compensatory up-regulation in beta1, suggesting important regulatory roles for transcription factors and the sprout-associated adhesion molecules. Analysis of inflammatory stimuli revealed a 50% reduction 12-48 hours following systemic endotoxin associated with neural inflammation and a tendency toward more sprouts in TNFR1/2 null mutants (P = 10%) with a reduced inflammatory response, indicating detrimental effects of excessive inflammation. Moreover, the study points to the usefulness of the facial axotomy model in exploring physiological and molecular stimuli regulating central sprouting.
Makwana
Milan
M
Department of Obstetrics and Gynaecology, EGA Institute for Women's Health, University College London, United Kingdom.
Werner
Alexander
A
Acosta-Saltos
Alejandro
A
Gonitel
Roman
R
Pararajasingam
Abirami
A
Pararajasingham
Abirami
A
Ruff
Crystal
C
Rumajogee
Prakasham
P
Cuthill
Dan
D
Galiano
Mathias
M
Bohatschek
Marion
M
Wallace
Adam S
AS
Anderson
Patrick N
PN
Mayer
Ulrike
U
Behrens
Axel
A
Raivich
Gennadij
G
D000818:Animals; D019771:Axotomy; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D005154:Facial Nerve / Q000378:metabolism / Q000502:physiology*; D020220:Facial Nerve Injuries / Q000378:metabolism / Q000503:physiopathology*; D019004:Galanin / Q000378:metabolism; D017353:Gene Deletion; D020439:Growth Cones / Q000378:metabolism / Q000648:ultrastructure*; D007150:Immunohistochemistry; D016023:Integrins / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000378:metabolism / Q000502:physiology*; D009416:Nerve Regeneration / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D016759:Oncogene Protein p65(gag-jun) / Q000235:genetics; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000235:genetics; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000235:genetics; D013997:Time Factors; D050494:Vesicular Acetylcholine Transport Proteins / Q000378:metabolism
D015815:Cell Adhesion Molecules; D016023:Integrins; D016759:Oncogene Protein p65(gag-jun); D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; C493460:Slc18a3 protein, mouse; C506236:Tnfrsf1a protein, mouse; D050494:Vesicular Acetylcholine Transport Proteins; D019004:Galanin; D015740:Calcitonin Gene-Related Peptide