| Zinc finger-like family of nuclear transcription factor (Kruppel-like transcription factors; KLFs) is an important endogenous regulation of axonal regeneration in eukaryotes developmental dependent transcription factor family.It has been found that KLFs own seventeen family members, zinc finger protein nuclear transcription factor4(Kruppel-like transcription factor4; KLF4) is one member of KLFs family,which consists of three domains:a highly conserved C-terminal DNA binding domain, the transcriptional regulation of the N-terminal highly variable domain and the nuclear localization sequence. KLF4plays an important role in cell growth, differentiation, proliferation and apoptosis of many basic life activities. Moore has been confirmed KLF4is a powerful axon growth inhibitors in embryonic hippocampal neurons and retinal ganglion cells (Retinal ganglion cells; RGCs).Furthermore, it has been confirmed tissue culture RGCs and optic nerve damage experiments in vivo, axons of RGCs missed KLF4gene could extend at different levels.Studies of Fischer D have shown that lens injury and intravitreal injection of purified β/γ-crystallin protein in adult rat, its mature RGCs neuron is active and apoptosis delayed, and could see new axons in the injuried optic nerve. In the past two decades, scholars committed JAK/STAT3-PI3K/AKT-MAPK/ERK-and other signaling pathways to explore the effect of lens injury on regulation of endogenous regenerative capacity of the central nervous system axons,however, KLFs as an important endogenous development-dependent zinc finger-like nuclear transcription factor to regulate axonal regeneration, whether involve and play an important role in this process also unknowable.We select KLF4,one of the most representative of KLFs,to explore the mechanisms on the effect of lens injury promting optic nerve regeneration in rats.ObjectiveTo observe the expression levels of KLF4mRNA in rat pure optic nerve injury and optic nerve injury combined lens injury models, explore the effect of lens injury promting optic nerve regeneration after optic nerve injury.MethodFifty-four healthy male Wistar rat were divided into three groups at random: Group A.Normal control group,6rats; Group B.Pure optic nerve injury group,24rats; Group C. Optic nerve injury combined lens injury group,24rats. Two rats in group A,8rats in group B,8rats in group C were repectively put to death at7days,14days and21days after injury.The morphology variations of optic nerve injury were observed under electromicroscopy(EMS).The expression levels of KLF4mRNA in three groups were analyzed by real time fluorescent quantitative PCR (qRT-PCR) at7days,14days and21days after injury.Results1. Ultrastructural changes of the optic nerve at three time points of three groupsCompared with the normal control group, EMS showed axonal swelling obviously, axoplasm electron density lower,myelin sheath structure chaos,which were visible in the two experimental group at7days. EMS also showed some new nerve fibers without myelin sheath are partial clustered, which were visible in combined injury group at7days. However, EMS showed many collagen fibers instead of the original optic nerve fibers at14days and21days. 2. Expression of KLF4mRNA in retinal ganglion cells and their axonsCompared with the normal control group(1.003±0.113), the relative expression of KLF4mRNA in pure injury group (0.561±0.045) and combined injury group (0.091±0.026) were all decreased in different degree,which in combined injury group reduced to the minimum at7days,the differences were statistically significant (P<0.05);compared with the normal control group, the expression levels of KLF4mRNA in pure injury group(0.333±0.106) and combined injury group(0.401±0.169) were also decreased in some degree at14days (P<0.05),yet,there was no statistical significance between which in pure injury group and combined injury group (P>0.05);however, compared with the normal control group, the expression levels of KLF4mRNA in pure injury group(1.100±0.100) and combined injury group (1.166±0.115) were slightly increased,there were no statistical significance among which in normal control group, pure injury group and combined injury group (P>0.05) at21days.Conclusion1. After optic nerve half cross sectional injury,lens injury induce early forming new nerve fibers without myelin sheath.2. Lens injury suppressed the expression of KLF4gene in RGCs, the inhibitory effect weaken gradually along with the time extension.3. KLF4may be involved in the lens damage promoting optic nerve regeneration process. |
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