Involvement of calcitonin gene-related peptide innervation in the promoting effect of low-intensity pulsed ultrasound on spinal fusion without decortication.
METHODS
A prospective left-right comparison designed experiment using a rabbit posterolateral intertransverse process fusion model.


OBJECTIVE
To investigate the involvement of calcitonin gene-related peptide (CGRP) innervation in the promoting effect of low intensity pulsed ultrasound stimulation (LIPUS) on spinal fusion without decortication.


BACKGROUND
Sensory neuropeptide CGRP is involved in bone repair and ectopic ossification. Comparison of CGRP innervations in ectopic bone between sham LIPUS and LIPUS sides can help us to understand the relationship between sensory nerve innervation and LIPUS.


METHODS
A total of 27 New Zealand white rabbits underwent bilateral posterolateral intertransverse process fusion with implantation of porous poly-D,L-lactic acid blocks loaded with 1.25 μg recombinant human bone morphogenetic protein-4 solution. One side was provided LIPUS daily whereas the other side served as control. Animals were killed and the operated lumbar vertebrae were harvested for histomorphologic evaluation at 3 days (n = 3), 1 week (n = 6), 3 weeks (n = 6), 7 weeks (n = 6), and 12 weeks (n = 6) following surgery, respectively.


RESULTS
LIPUS accelerated the invasion of CGRP-positive nerve fibers during ectopic ossification spatially and temporally. Spatially, CGRP-positive nerve fibers were also observed in the new formed cartilage and bone tissues on LIPUS side, whereas they were only detected in the fibrous tissue and bone marrow on sham LIPUS side. Temporally, the density of CGRP-positive nerve fibers was significantly higher on the LIPUS side when compared with the sham LIPUS side.


CONCLUSIONS
LIPUS promoted the invasion of CGRP sensory nerve in ectopic bone, which may in turn contribute to the promoting effect of LIPUS on ectopic ossification.
Wang
Xiao-Yun
XY
Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
Guo
Xia
X
Cheng
Jack Chung-Yiu
JC
Mi
Yong-Li
YL
Lai
Patrick Yau-Ming
PY
D000818:Animals; D055415:Bone Morphogenetic Protein 4 / Q000494:pharmacology; D001861:Bone Regeneration / Q000502:physiology; D001842:Bone and Bones / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002356:Cartilage / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D023421:Models, Animal; D009412:Nerve Fibers / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D011984:Sensory Receptor Cells / Q000378:metabolism; D013123:Spinal Fusion; D018617:Ultrasonography, Doppler, Pulsed
D055415:Bone Morphogenetic Protein 4; D015740:Calcitonin Gene-Related Peptide