Effect of hepatocyte growth factor on the promotion of in vitro spinal cord neurite regeneration

Cheng LIU; Haiping QUE; Cuili SHU; Shaojun LIU; Zuze WU

ABSTRACT

BACKGROUND:

Hepatocyte growth factor (HGF) promotes neurite outgrowth from neocortical explants, and supports neuronal survival under serum-free condition. Thus, HGF can mediate neurotrophic function as a novel neurotrophic factor.

OBJECTIVE:

To establish an in vitro injury model with a semi-solid culture system for the purpose of improving the evaluation of neurite regeneration of transected spinal cord neurons from rat embryo, and investigate the effect of HGF on neurite regeneration.

DESIGN:

Randomized controlled study.

SETTING:

Hematology Laboratory of Radian Medical Institute of Academy of Military Medical Sciences of PLA.MATERIALS The experiment was carried out at the Hematology Laboratory of Radian Medical Institute of Academy of Military Medical Sciences of PLA from August 2004 to May 2005. Wistar fetal rats of 14-16 days old were provided by Animal Center of Academy of Military Medical Sciences of PLA. Tail collagen was extracted from adult male Wistar rats with body mass of (250±50) g.

METHODS:

① Rat tail type Ⅰ collagen substrate was prepared and spread on a culture dish, cut into about 0.5-1.0 mm3 slices, then spinal cord slices of 15-day-old fetal Wistar rat were explanted on the primary culture. Five days later, the outgrowing processes were severed, then a block of collagen, with the surface area of 2 mm2 and 200 μm away from the slice, was removed and the vacancy was replaced with a fresh collagen block of 2 μL after aspirating the medium. The fresh collagen block could be solidified and then fresh liquid medium was added as the secondary culture. The regeneration of neurite was observed by microscopy at 0, 1, 6,12 and 24 hours after severing. ② The medium was changed with 0.5% N3-conditioned medium. 10 μg/L HGF was added in the experimental group, and 0.5% N3-conditioned medium was added in the control group.The status of regeneration was evaluated by the average value of 3 longest regenerative neurites for each slice. There were 12 slices in each group.The status of neurite regeneration was calculated and was evaluated 24 hours later.MAIN OUTCOME

MEASURES:

① neurite regeneration in situ; ②comparisons of neurite regeneration between control group and experimental group.

RESULTS:

① Neurite regeneration in situ The neurites disintegrated near the severing line immediately following the transection injury. This process persisted about 1-2 hours and the distance away from the severing line was about 20 μm. Then the proximal end of neurites would swell and thicken. At this time neurites stopped collapsing and neurite regeneration began. Their regenerating rate would quicken at 12 hours after severing. Regenerating neurites were more branching and curlier as compared with original neurites. ② Comparisons of neurite regeneration between control group and experimental group The average length of regenerative neurites was more in the experimental group than that in the control group [(375±96) μm, (200±75) μm, P ＜ 0.05].

CONCLUSION:

① We establish a simple, economic model to evaluate neurite regeneration. ② By this model, we prove that HGF can promote neurite regeneration.