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ID naloge: 159 Letnik: 2003 Predmet: patofiziologija
RAZLIKE MED SPOLOMA V REGENERACIJI SENZORICNIH AKSONOV PO POŠKODBI PERIFERNEGA ŽIVCA PRI PODGANI
Avtor: Tilen Žele
Mentor: doc. dr. Fajko Bajrovic
Somentor: Uroš Kovacic
IZHODIŠCE: Po poškodbi perifernega živca se motoricni aksoni pri samicah regenerirajo hitreje kot pri samcih. Ni znano, ali obstajajo razlike med spoloma tudi pri regeneraciji senzoricnih aksonov.
NAMEN: Prouciti morebitno razliko med spoloma glede hitrosti regeneracije senzoricnih aksonov in obsega obnove nocicepcije kože po poškodbi perifernega živca podgane.
HIPOTEZE: Predpostavili smo, da je zgodnja regeneracija senzoricnih aksonov po aksonotmezi pri samicah podgan hitrejša kot pri samcih, ter da je obnova nocicepcije v koži po takšni poškodbi pri samicah hitrejša in površinsko obsežnejša kot pri samcih. Dodatno smo predpostavili, da povecana hitrost regeneracije senzoricnih aksonov pri samicah ni posledica endokrinih ucinkov spolnih hormonov in da zato odstranitev jajcnikov pri samicah ne bo bistveno vplivala na hitrost zgodnje regeneracije senzoricnih aksonov. Na razliko med spoloma v hitrosti zgodnje regeneracije naj bi pomembno vplivala celicna podpora aksonom v odseku živca distalno od poškodbe.
METODE: V prvem poskusu smo pri normalnih samcih in samicah ter samicah z odstranjenimi jajcniki poškodovali suralni živec z aksonotmezo. Regeneracijo aksonov smo nato zasledovali s testom ušcipa živca v obdobju osmih dni. Dolocili smo število regenerirajocih se aksonov v poškodovanem živcu z imunohistokemicno reakcijo na nevrofilament. V drugem poskusu smo pri normalnih samcih in samicah s testom ušcipa kože zasledovali obnavljanje obcutljivosti za bolecino v nartu tacke po poškodbi suralnega živca z aksonotmezo in trajni prekinitvi sosednjih živcev v obdobju 24 tednov.
V tretjem poskusu smo pri normalnih samcih in samicah ter samicah z odstranjenimi jajcniki po aksonotmezi s testom ušcipa živca dolocili hitrost regeneracije aksonov skozi distalni odsek suralnega živca, v katerem smo celice unicili z zmrzovanjem in tako odstranili celicno podporo aksonom.
REZULTATI: Pri prvem poskusu je bila povprecna dolžina, za katero so se podaljšali najhitreje regenerirajoci se aksoni osem dni po aksonotmezi, za približno 15% vecja pri samicah kot pri samcih. Razlika je bila statisticno znacilna (p<0,01). Število regenerirajocih se aksonov med spoloma ni bilo statisticno znacilno razlicno (p>0,05).
Pri drugem poskusu je bil delež na bolecino obcutljivega podrocja kože narta statisticno znacilno vecji pri samicah v primerjavi s samci med celotnim poskusom (p<0,05). Na koncu poskusa (24. teden) je bilo to podrocje pri samicah za približno 20% vecje kot pri samcih. Tudi povprecna absolutna površina podrocja bolecinske obcutljivosti je bila 2 tedna, 8 tednov in 24 tednov po aksonotmezi statisticno znacilno vecja pri samicah kot pri samcih (p<0,05), na koncu za približno 28 mm2.
Povprecna dolžina, za katero so se podaljšali najhitreje regenerirajoci se aksoni 8 dni po aksonotmezi pri samicah z odstranjenimi jajcniki ni bila statisticno znacilno razlicna od dolžine pri normalnih samicah, je pa bila statisticno znacilno vecja v primerjavi z normalnimi samci. Razlike glede podaljšanja senzoricnih aksonov pri regeneraciji skozi brezcelicni distalni odsek živca 8 dni po aksonotmezi pri normalnih samcih, normalnih samicah in samicah z odstranjenimi jajcniki niso bile statisticno znacilne.
ZAKLJUCKI: V raziskavi smo potrdili hipotezi, da sta po aksonotmezi perifernega živca tako zgodnja regeneracija senzoricnih aksonov kot tudi obnova nocicepcije hitrejši pri samicah kot pri samcih. Obnova nocicepcije je pri samicah tudi bolj obsežna. Hitrejša zgodnja regeneracija senzoricnih aksonov pri samicah ni odvisna od endokrinih ucinkov spolnih hormonov. Zdi se, da na razliko med spoloma glede hitrosti zgodnje regeneracije senzoricnih aksonov pomembno vpliva celicna podpora v odseku živca distalno od poškodbe.
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[Abstract / English version]
RAZLIKE MED SPOLOMA V REGENERACIJI SENZORICNIH AKSONOV PO POŠKODBI PERIFERNEGA ŽIVCA PRI PODGANI
Author: Tilen Žele
Mentor: doc. dr. Fajko Bajrovic
Co-mentor: Uroš Kovacic
BACKGROUND: After peripheral nerve injury, motor axon regeneration and functional recovery is faster in female than in male rats. Possible sex related differences in the regeneration of sensory axons have not been examined yet.
AIM: To study possible sex related differences in the rate of early regeneration of sensory axons and recovery of nociception after the peripheral nerve injury in the rat.
HYPOTHESES: We hypothesized that early regeneration of sensory axons after peripheral nerve crush is faster in female than in male rats, and that the recovery of nociception after such an injury is faster and more extensive in females than in males. If so, we further hypothesized that the faster regeneration of sensory axons in female rats is not due to the effects of the circulating ovarian hormones but, rather, is related to the more effective cell support for the axons in the nerve segment distal to the injury.
METHODS: In the first experiment, the sural nerve was crushed in normal female and male rats, and ovariectomised female rats. The regeneration of sensory axons was followed during 8 days after the nerve injury. The elongation of the fastest regenerating nociceptive axons was assessed by the nerve pinch test. The abundance of regenerating axons was examined in nerve cross sections 8 mm distal from the crush site by the immunohistochemical reaction to neurofilament.
In the second experiment, the sural nerve was crushed in intact male and female rats, and the adjacent nerves were transected and ligated. Then recovery of the nociception in the skin of the instep of the right foot was monitored for 24 weeks by the skin pinch test.
In the third experiment, the sural nerve was crushed and its segment just distal to the crush lesion was made acellular by freezing and thawing in intact female and male rats, and ovariectomised female rats. Eight days after the nerve injury, the regeneration of the sensory axons was assessed as in the first experiment.
RESULTS: Eight days after the sural nerve crush, the elongation distance of the fastest growing sensory axons was about 15% greater in female than in male rats. The difference was statistically significant (p<0.01). The difference in the number of regenerating sensory axons was not statistically different between the two groups.
The recovery of nociception in skin of the instep was significantly faster and more extensive in female rats during the whole observational period. At 24 weeks after injury, the area of recovered nociception was about 20% greater in female than in male rats (p<0.05).
The average elongation of the fastest growing sensory axons 8 days after the sural nerve crush in ovariectomised females was not statistically significantly different from that in the normal female rats, however, it was still significantly greater than in the intact male rats (p<0.05). In contrast, there were no statistically significant differences between the normal female, normal male and ovariectomised female rats regarding the average elongation of the fastest growing sensory axons regenerating in the absence of the cellular support in the nerve segment distal to the crush site.
CONCLUSIONS: The results corroborated our hypothesis that the regeneration of sensory axons and recovery of nociception after peripheral nerve injury is faster in female than in male rats. It seems that a more effective cell support in the distal nerve segment, rather than circulating female sex hormones in plasma, is responsible for faster early regeneration of nociceptive axons in females than in males.
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