umu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Neuroprotection and axonal regeneration after peripheral nerve injury
Umeå University, Faculty of Medicine, Integrative Medical Biology, Anatomy. Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Hand Surgery. (Neurogruppen)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Following microsurgical reconstruction of injured peripheral nerves, severed axons are able to undergo spontaneous regeneration. However, the functional result is always unsatisfactory with poor sensory recovery and reduced motor function. One contributing factor is the retrograde neuronal death, which occurs in the dorsal root ganglia (DRG) and in the spinal cord. An additional clinical problem is the loss of nerve tissue that often occurs in the trauma zone and which requires “bridges” to reconnect separated nerve ends. The present thesis investigates the extent of retrograde degeneration in spinal motoneurons and cutaneous and muscular afferent DRG neurons after permanent axotomy and following treatment with N-acetyl-cysteine (NAC). In addition, it examines the survival and growth-promoting effects of nerve reconstructions performed by primary repair and peripheral nerve grafting in combination with NAC treatment.

In adult rats, cutaneous sural and muscular medial gastrocnemius DRG neurons and spinal motoneurons were retrogradely labeled with fluorescent tracers from the homonymous transected nerves. Survival of labeled neurons was assessed at different time points after nerve transection, ventral root avulsion and ventral rhizotomy. Axonal regeneration was evaluated using fluorescent tracers after sciatic axotomy and immediate nerve repair. Intraperitoneal or intrathecal treatment with NAC was initiated immediately after nerve injury or was delayed for 1-2 weeks.

Counts of labeled gastrocnemius DRG neurons did not reveal any significant retrograde cell death after nerve transection. Sural axotomy induced a delayed loss of DRG cells, which amounted to 43- 48% at 8-24 weeks postoperatively. Proximal transection of the sciatic nerve at 1 week after initial axonal injury did not further increase retrograde DRG degeneration, nor did it affect survival of corresponding motoneurons. In contrast, rhizotomy and ventral root avulsion induced marked 26- 53% cell loss among spinal motoneurons. Primary repair or peripheral nerve grafting supported regeneration of 53-60% of the motoneurons and 47-49% of the muscular gastrocnemius DRG neurons at 13 weeks postoperatively. For the cutaneous sural DRG neurons, primary repair or peripheral nerve grafting increased survival by 19-30% and promoted regeneration of 46-66% of the cells. Regenerating sural and medial gastrocnemius DRG neurons upregulate transcription of peripherin and activating transcription factor 3. The gene expression of the structural neurofilament proteins of high molecular weight was significantly downregulated following injury in both regenerating and non-regenerating sensory neurons. Treatment with NAC was neuroprotective for spinal motoneurons after ventral rhizotomy and avulsion, and sural DRG neurons after sciatic nerve injury. However, combined treatment with nerve graft and NAC had significant additive effect on neuronal survival and also increased the number of sensory neurons regenerating across the graft. In contrast, NAC treatment neither affected the number of regenerating motoneurons nor the number of myelinated axons in the nerve graft and in the distal nerve stump.

In summary, the present results demonstrate that cutaneous sural sensory neurons are more sensitive to peripheral nerve injury than muscular gastrocnemius DRG cells. Moreover, the retrograde loss of cutaneous DRG cells taking place despite immediate nerve repair would still limit recovery of cutaneous sensory functions. Experimental data also show that NAC provides a highly significant degree of neuroprotection in animal models of adult nerve injury and could be combined with nerve grafting to further attenuate retrograde neuronal death and to promote functional regeneration.

Place, publisher, year, edition, pages
Umeå: Umeå university , 2010. , 58 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1342
Keyword [en]
Dorsal root ganglion; Motoneuron; Axonal reaction; Peripheral nerve injury; Nerve regeneration; N-acetylcysteine
National Category
Surgery Cell and Molecular Biology
Research subject
Human Anatomy; handkirurgi
Identifiers
URN: urn:nbn:se:umu:diva-32819ISBN: 978-91-7264-975-0 (print)OAI: oai:DiVA.org:umu-32819DiVA: diva2:306174
Public defence
2010-04-23, sal BiA201, Biologihuset, Umeå Universitet, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2010-03-30 Created: 2010-03-28 Last updated: 2010-03-30Bibliographically approved
List of papers
1. Survival and regeneration of cutaneous and muscular afferent neurons after peripheral nerve injury in adult rats
Open this publication in new window or tab >>Survival and regeneration of cutaneous and muscular afferent neurons after peripheral nerve injury in adult rats
Show others...
2008 (English)In: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 186, 315-323 p.Article in journal (Refereed) Published
Abstract [en]

Peripheral nerve injury induces the retrograde degeneration of dorsal root ganglion (DRG) cells, which affects predominantly the small-diameter cutaneous afferent neurons. This study compares the time-course of retrograde cell death in cutaneous and muscular DRG cells after peripheral nerve transection as well as neuronal survival and axonal regeneration after primary repair or nerve grafting. For comparison, spinal motoneurons were also included in the study. Sural and medial gastrocnemius DRG neurons were retrogradely labeled with the fluorescent tracers Fast Blue (FB) or Fluoro-Gold (FG) from the homonymous transected nerves. Survival of labeled sural and gastrocnemius DRG cells was assessed at 3 days and 1-24 weeks after axotomy. To evaluate axonal regeneration, the sciatic nerve was transected proximally at 1 week after FB-labeling of the sural and medial gastrocnemius nerves and immediately reconstructed using primary repair or autologous nerve grafting. Twelve weeks later, the fluorescent tracer Fluoro-Ruby (FR) was applied 10 mm distal to the sciatic lesion in order to double-label sural and gastrocnemius neurons that had regenerated across the repair site. Counts of labeled gastrocnemius DRG neurons did not reveal any significant retrograde cell death after nerve transection. In contrast, sural axotomy induced a delayed loss of sural DRG cells, which amounted to 22% at 4 weeks and 43-48% at 8-24 weeks postoperatively. Proximal transection of the sciatic nerve at 1 week after injury to the sural or gastrocnemius nerves neither further increased retrograde DRG degeneration, nor did it affect survival of sural or gastrocnemius motoneurons. Primary repair or peripheral nerve grafting supported regeneration of 53-60% of the spinal motoneurons and 47-49% of the muscular DRG neurons at 13 weeks postoperatively. In the cutaneous DRG neurons, primary repair or peripheral nerve grafting increased survival by 19-30% and promoted regeneration of 46-66% of the cells. The present results suggest that cutaneous DRG neurons are more sensitive to peripheral nerve injury than muscular DRG cells, but that their regenerative capacity does not differ from that of the latter cells. However, the retrograde loss of cutaneous DRG cells taking place despite immediate nerve repair would still limit the recovery of cutaneous sensory functions.

National Category
Surgery Cell and Molecular Biology
Research subject
Human Anatomy; handkirurgi
Identifiers
urn:nbn:se:umu:diva-8117 (URN)10.1007/s00221-007-1232-5 (DOI)18057922 (PubMedID)
Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2010-06-24Bibliographically approved
2. Peripherin and ATF3 genes are differentially regulated in regenerating and non-regenerating primary sensory neurons
Open this publication in new window or tab >>Peripherin and ATF3 genes are differentially regulated in regenerating and non-regenerating primary sensory neurons
Show others...
2010 (English)In: Brain Research, ISSN 0006-8993, E-ISSN 1872-6240, Vol. 1310, 1-7 p.Article in journal (Refereed) Published
Abstract [en]

Peripheral nerve injury leads to deficient recovery of sensation and a causative factor may be that only 50-60% of primary sensory neurons succeed in regenerating axons after primary nerve repair. In this study, an in vivo rat sciatic nerve injury and regeneration model was combined with laser microdissection and quantitative real-time polymerase chain reaction with the aim of examining the gene expression of regenerative molecules in cutaneous and muscular sensory neurons. Recent studies have identified peripherin and ATF-3 molecules as crucial for neurite outgrowth propagation; our novel findings demonstrate a subpopulation of non-regenerating sensory neurons characterized by a failure to upregulate transcription of these molecules and that a greater peripherin mRNA expression in injured cutaneous neurons may potentiate this subpopulation to regenerate more axons than muscle afferent neurons following injury. The gene expression of the structural neurofilament NF-H is found to be significantly downregulated following injury in both sensory subpopulations.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
Dorsal root ganglion, Peripheral nerve injury, Nerve regeneration, Regeneration-associated gene, Fluorescent tracer
National Category
Surgery Cell and Molecular Biology
Research subject
Human Anatomy; handkirurgi
Identifiers
urn:nbn:se:umu:diva-32011 (URN)10.1016/j.brainres.2009.11.011 (DOI)000274450900001 ()19913522 (PubMedID)
Available from: 2010-03-03 Created: 2010-02-26 Last updated: 2012-02-29Bibliographically approved
3. Motorneuron protection by N-acetyl-cysteine after ventral root avulsion and ventral rhizotomy
Open this publication in new window or tab >>Motorneuron protection by N-acetyl-cysteine after ventral root avulsion and ventral rhizotomy
Show others...
2005 (English)In: British Journal of Plastic Surgery, ISSN 0007-1226, E-ISSN 1465-3087, Vol. 58, no 6, 765-773 p.Article in journal (Refereed) Published
Abstract [en]

Motor recovery after proximal nerve injury remains extremely poor, despite advances in surgical care. Several neurobiological hurdles are implicated, the most fundamental being extensive cell death within the motorneuron pool. N-acetyl-cysteine almost completely protects sensory neurons after peripheral axotomy, hence its efficacy in protecting motorneurons after ventral root avulsion/rhizotomy was investigated. In adult rats, the motorneurons supplying medial gastrocnemius were unilaterally pre-labelled with retrograde tracer (true-blue/fluoro-gold), prior to L5 and 6 ventral root avulsion, or rhizotomy. Groups received either intraperitoneal N-acetyl-cysteine (ip, 150 or 750 mg/kg/day), immediate or delayed intrathecal N-acetyl-cysteine treatment (it, 2.4 mg/day), or saline; untreated animals served as controls. Either 4 (avulsion model) or 8 (rhizotomy model) weeks later, the pre-labelled motorneurons' mean soma area and survival were quantified. Untreated controls possessed markedly fewer motorneurons than normal due to cell death (avulsion 53% death; rhizotomy 26% death, P<0.01 vs. normal). Motorneurons were significantly protected by N-acetyl-cysteine after avulsion (ip 150 mg/kg/day 40% death; it 30% death, P<0.01 vs. no treatment), but particularly after rhizotomy (ip 150 mg/kg/day 17% death; ip 750 mg/kg/day 7% death; it 5% death, P<0.05 vs. no treatment). Delaying intrathecal treatment for 1 week after avulsion did not impair neuroprotection, but a 2-week delay was deleterious (42% death, P<0.05 vs. 1-week delay, 32% death). Treatment prevented the decrease in soma area usually found after both types of injury. N-acetyl-cysteine has considerable clinical potential for adjuvant treatment of major proximal nerve injuries, including brachial plexus injury, in order that motorneurons may survive until surgical repair facilitates regeneration.

Keyword
Acetylcysteine/*pharmacology, Animals, Cell Death/physiology, Female, Motor Neurons/*drug effects/physiology, Neuroprotective Agents/*pharmacology, Rats, Rats; Sprague-Dawley, Rhizotomy/*methods, Sciatic Nerve/*injuries/surgery, Spinal Nerve Roots/*injuries/surgery
National Category
Surgery Cell and Molecular Biology
Research subject
handkirurgi; Human Anatomy
Identifiers
urn:nbn:se:umu:diva-12716 (URN)10.1016/j.bjps.2005.04.012 (DOI)16040014 (PubMedID)
Available from: 2007-12-11 Created: 2007-12-11 Last updated: 2010-06-24Bibliographically approved
4. Effects of N-acetyl-cysteine on the survival and regeneration of sural sensory neurons in adult rats
Open this publication in new window or tab >>Effects of N-acetyl-cysteine on the survival and regeneration of sural sensory neurons in adult rats
Show others...
2009 (English)In: Brain Research, ISSN 0006-8993, E-ISSN 1872-6240, Vol. 1287, no 1, 58-66 p.Article in journal (Refereed) Published
Abstract [en]

Microsurgical reconstruction of injured peripheral nerves often results in limited functional recovery. One contributing factor is the retrograde neuronal degeneration of sensory neurons in the dorsal root ganglia (DRG) and of motor neurons in the spinal cord. The present study investigates the neuroprotective and growth-promoting effects of N-acetyl-cysteine (NAC) on sensory DRG neurons and spinal motoneurons after sciatic axotomy and nerve grafting in adult rats. Sciatic axotomy and nerve grafting were performed at 1 week after sural DRG neurons and motoneurons were retrogradely labeled with the fluorescent tracer Fast Blue. To assess the efficacy of axonal regeneration, a second fluorescent dye Fluoro-Ruby was applied distal to the graft at 12 weeks after nerve repair. At 8-13 weeks after axotomy, only 52-56% of the sural sensory neurons remained in the lumbar DRG, while the majority of motoneurons survived the sciatic nerve injury. Nerve grafting alone or continuous intrathecal NAC treatment (2.4 mg/day) improved survival of sural DRG neurons. Combined treatment with nerve graft and NAC had significant additive effect on neuronal survival and also increased the number of sensory neurons regenerating across the graft. However, NAC treatment neither affected the number of regenerating motoneurons nor the number of myelinated axons in the nerve graft or in the distal nerve stump. The present results demonstrate that NAC provides a highly significant effect of neuroprotection in an animal nerve injury model and that combination with nerve grafting further attenuates retrograde cell death and promotes regeneration of sensory neurons.

Keyword
Dorsal root ganglion, Motoneuron, Axonal reaction, Peripheral nerve graft, Nerve regeneration, N-acetyl-cysteine
National Category
Surgery Cell and Molecular Biology
Research subject
Human Anatomy; handkirurgi
Identifiers
urn:nbn:se:umu:diva-31984 (URN)10.1016/j.brainres.2009.06.038 (DOI)19555676 (PubMedID)
Available from: 2010-03-03 Created: 2010-02-26 Last updated: 2012-06-04Bibliographically approved

Open Access in DiVA

fulltext(540 kB)4239 downloads
File information
File name FULLTEXT01.pdfFile size 540 kBChecksum SHA-512
790937ea72900de178fe63a78d3b251a78e85e2f86cc924168e42eb8a5b921b4b9c0cee8eef2e840d12f636a3185fc5f4886e58a05cb2490dd4589ca80df9d90
Type fulltextMimetype application/pdf

Authority records BETA

Welin, Dag

Search in DiVA

By author/editor
Welin, Dag
By organisation
AnatomyHand Surgery
SurgeryCell and Molecular Biology

Search outside of DiVA

GoogleGoogle Scholar
Total: 4239 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 342 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf