Changes of substance P-immunoreactive nerve fiber innervation density in the sublesional bones in young growing rats at an early stage after spinal cord injury.
Spinal cord injury (SCI) causes osteoporosis (OP), and the neuropeptide substance P (SP) may play important roles in the pathogenesis of OP after SCI. Our study confirmed SCI-induced sublesional bone loss in young rats at an early stage is associated with a significant increase of SP-immunoreactive nerve fiber innervation density.


BACKGROUND
Spinal cord injury (SCI) causes osteoporosis (OP), and neuropeptides may play important roles in the pathogenesis of OP after SCI. However, few data exist concerning the relationship between neural factors and OP following SCI.


METHODS
One hundred and eight SCI and hindlimb cast immobilization (HCI) rats were studied for skeletal innervation of substance P (SP) and neurofilament 200 (NF200) with immunocytochemistry. Bone and serum SP levels were also assessed using enzyme immunoassay.


RESULTS
Developing bone loss was successfully induced by SCI at 3 wks and by HCI at 6 wks. We observed a significant increase of SP-immunoreactive (IR) nerve fibers and decrease of NF200-IR nerve fibers in the tibiae of SCI rats compared with HCI and control (CON) rats at all time points. SP in the proximal tibiae in SCI rats was significantly higher than that in HCI and CON rats at all time points, but no difference was found in the serum.


CONCLUSIONS
SCI-induced sublesional bone loss in young rats at an early stage is associated with a significant increase of nerve fiber innervation density of SP-IR and decrease of NF200-IR. We speculated that neural factors may play an important role in pathogenesis of OP after SCI.
Liu
D
D
Department of Orthopaedic Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
Li
H
H
Zhao
C-Q
CQ
Jiang
L-S
LS
Dai
L-Y
LY
D000818:Animals; D015519:Bone Density / Q000502:physiology*; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010024:Osteoporosis / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000473:pathology*; D013373:Substance P / Q000378:metabolism*; D016896:Treatment Outcome
D018377:Neurotransmitter Agents; D013373:Substance P