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Biodegradable fibrin conduit promotes long-term regeneration after peripheral nerve injury in adult rats
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy. Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
2010 (English)In: Journal of Plastic, Reconstructive & Aesthetic Surgery, ISSN 1748-6815, E-ISSN 1532-1959, Vol. 63, no 11, 1893-1899 p.Article in journal (Refereed) Published
Abstract [en]

Peripheral nerve injuries are often associated with loss of nerve tissue and require autologous nerve grafts to provide a physical substrate for axonal growth. Biosynthetic neural conduits could be an alternative treatment strategy in such injuries. The present study investigates the long-term effects of a tubular fibrin conduit on neuronal regeneration, axonal sprouting and recovery of muscle weight following peripheral nerve injury and repair in adult rats. Sciatic axotomy was performed proximally in the thigh to create a 10-mm gap between the nerve stumps. The injury gap was bridged by using a 14-mm-long fibrin glue conduit, entubulating 2mm of the nerve stump at each end. A reversed autologous nerve graft was used as a control. The regenerative response from sensory and motor neurones was evaluated following retrograde labelling with Fast Blue fluorescent tracer. In control experiments, at 16 weeks following peripheral nerve grafting, 5184 (+/-574 standard error of mean (SEM)) sensory dorsal root ganglion neurones and 1001 (+/-37 SEM) spinal motor neurones regenerated across the distal nerve-graft interface. The fibrin conduit promoted regeneration of 60% of sensory neurones and 52% of motor neurones when compared to the control group. The total number of myelinated axons in the distal nerve stump in the fibrin-conduit group reached 86% of the control and the weight of gastrocnemius and soleus muscles recovered to 82% and 89% of the controls, respectively. The present results suggest that a tubular fibrin conduit can be used to promote neuronal regeneration following peripheral nerve injury.

Place, publisher, year, edition, pages
Elsevier , 2010. Vol. 63, no 11, 1893-1899 p.
Keyword [en]
Biosynthetic conduit, Dorsal root ganglion, Fluorescent tracer, Motor neurone, Nerve injury, Nerve graft
National Category
Neurosciences
Research subject
Surgery
Identifiers
URN: urn:nbn:se:umu:diva-35218DOI: 10.1016/j.bjps.2009.11.024ISI: 000282944600034PubMedID: 20005193OAI: oai:DiVA.org:umu-35218DiVA: diva2:338013
Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Nerve gap repair by the use of artificial conduits and cultured cells
Open this publication in new window or tab >>Nerve gap repair by the use of artificial conduits and cultured cells
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Peripheral nerve injuries are often associated with loss of nerve tissue and require autologous nerve grafts to provide a physical substrate for axonal growth. This thesis investigates the use of fibrin as both a tubular conduit to guide nerve regeneration and also as a matrix material to suspend various regenerative cell types within/on poly-3-hydroxybutyrate (PHB) nerve conduits. Adipose derived stem cells (ASC) are found in abundant quantities. In this thesis the ability of rat ASC to differentiate into Schwann cells was determined and a preliminary study of the neurotrophic potential of human ASC was also investigated.

Rat sciatic nerve axotomy was performed proximally in the thigh to create a 10-mm gap between the nerve stumps and the gap was bridged using the various conduits.  At early time points the nerve grafts were harvested and investigated for axonal and Schwann cell markers.  After 16 weeks the regenerative response from sensory and motor neurons was also evaluated following retrograde labelling with Fast Blue fluorescent tracer. Stem cells were treated with a mixture of glial growth factors and after 2 weeks in vitro the expression of Schwann cell markers was analysed by immunocytochemistry and Western blotting.  ASC were cocultured with the NG108-15 neuronal cell line to determine their ability to promote neurite outgrowth.  Human ASC were isolated from the deep and superficial layers of abdominal fat tissue obtained during abdominoplasty procedures.  RT-PCR was used to investigate the expression of neurotrophic factors.

Immunohistochemistry showed a superior nerve regeneration distance in the fibrin conduit compared with PHB. The fibrin conduit promoted regeneration of 60% of sensory neurones and 52% of motor neurones when compared with an autograft group at 16 weeks. The total number of myelinated axons in the distal nerve stump in the fibrin-conduit group reached 86% of the graft and the weight of gastrocnemius and soleus muscles recovered to 82% and 89% of the controls, respectively. In vitro studies showed that rat ASC could be differentiated to a Schwann cell phenotype. These treated cells enhanced both the number of NG108-15 cells expressing neurites and neurite length. In the same coculture model system, human superficial fat layer ASC induced significantly enhanced neurite outgrowth when compared with the deep layer fat cells. RT-PCR analysis showed ASC isolated from both layers expressed neurotrophic factors.

These results indicate that a tubular fibrin conduit can be used to promote neuronal regeneration following peripheral nerve injury. There was also a beneficial effect of using a fibrin matrix to seed cells within/on PHB conduits which should ultimately lead to improved functional recovery following nerve injury.  There might also be an advantage to use a simple strip of PHB rather than a conventional tube-like structure implying that single fascicle nerve grafting could be advantageous for nerve repair.  The results of in vitro experiments indicate adipose tissue contains a pool of regenerative stem cells which can be differentiated to a Schwann cell phenotype and given that human ASC express a range of neurotrophic factors they are likely to be of clinical benefit for treatment of peripheral nerve injuries.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2010. 54 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1369
Keyword
adipose stem cells, cell matrix, fibrin, nerve conduit, nerve gap
National Category
Surgery
Research subject
Surgery
Identifiers
urn:nbn:se:umu:diva-35582 (URN)978-91-7459-038-8 (ISBN)
Public defence
2010-09-20, BiA201, Biologihuset, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2010-08-30 Created: 2010-08-24 Last updated: 2010-08-30Bibliographically approved
2. Biosynthetic conduits and cell transplantation for neural repair
Open this publication in new window or tab >>Biosynthetic conduits and cell transplantation for neural repair
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Spinal cord injury results in complete failure of the central neurons to regenerate and is associated with cyst formation and enlargement of the trauma zone. In contrast to the spinal cord, axons in the injured peripheral nerve have the capacity to undergo some spontaneous regeneration. However, significant post-traumatic loss of nervous tissue causing long nerve gap is one of the main reasons for the poor restoration of function following microsurgical repair of injured nerves. The present thesis investigates the effects of biodegradable conduits prepared from fibrin glue and poly-beta-hydroxybutyrate (PHB) in combination with cultured Schwann cells, mesenchymal stem cells and extracellular matrix molecules on regeneration after spinal cord and peripheral nerve injury in adult rats.

At 4-8 weeks after transplantation into the injured spinal cord, the PHB conduit was well integrated into the cavity but regenerating axons were found mainly outside the PHB. When suspension of BrdU-labeled Schwann cells was added to the PHB, regenerating axons filled the conduit and became associated with the implanted cells. Modification of the PHB surface with extracellular matrix molecules significantly increased Schwann cell attachment and proliferation but did not alter axonal regeneration. To improve the labeling technique of the transplanted cells, the efficacy of fluorescent cell tracers Fast Blue, PKH26, Vibrant DiO and Cell Tracker™ Green CMFDA was evaluated. All tested dyes produced very efficient initial labeling of olfactory ensheathing glial cells in culture. The number of Fast Blue-labeled cells remained largely unchanged during the first 4 weeks whereas the number of cells labeled with other tracers was significantly reduced after 2 weeks. After transplantation into the spinal cord, Fast Blue-labeled glial cells survived for 8 weeks but demonstrated very limited migration from the injection sites. Additional immunostaining with glial and neuronal markers demonstrated transfer of the dye from the transplanted cells to the host tissue.

In a sciatic nerve injury model, the extent of axonal regeneration through a 10mm gap bridged with tubular PHB conduit was compared with a fibrin glue conduit. At 2 weeks after injury, the fibrin conduit supported similar axonal regeneration and migration of the host Schwann cells compared with the PHB conduit augmented with a diluted fibrin matrix and GFP-labeled Schwann cells or mesenchymal stem cells. The long-term regenerative response was evaluated using retrograde neuronal labeling. The fibrin glue conduit promoted regeneration of 60% of sensory neurons and 52% of motoneurons when compared with the autologous nerve graft. The total number of myelinated axons in the distal nerve stump in the fibrin conduit group reached 86% of the nerve graft control and the weight of gastrocnemius and soleus muscles recovered to 82% and 89%, respectively. When a fibrin conduit was used to bridge a 20mm sciatic nerve gap, the weight of gastrocnemius muscle reached only 43% of the nerve graft control. The morphology of the muscle showed more chaotic appearance and the mean area and diameter of fast type fibers were significantly worse than those of the corresponding 10mm gap group. In contrast, both gap sizes treated with nerve graft showed similar fiber size.

In summary, these results show that a PHB conduit promotes attachment, proliferation and survival of adult Schwann cells and supports marked axonal growth after transplantation into the injured spinal cord. The data suggest an advantage of the fibrin conduit for the important initial phase of peripheral nerve regeneration and demonstrate potential of the conduit to promote long-term neuronal regeneration and muscle recovery.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2011. 61 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1408
Keyword
Spinal cord injury; Peripheral nerve injury; Nerve graft; Biosynthetic conduit; Nerve tissue engineering; Neural prosthesis
National Category
Neurosciences
Research subject
Neurology; Neurosurgery
Identifiers
urn:nbn:se:umu:diva-42440 (URN)978-91-7459-160-6 (ISBN)
Public defence
2011-05-19, BiA201, Biologihuset, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2011-04-28 Created: 2011-04-07 Last updated: 2011-04-28Bibliographically approved
3. Development of biosynthetic conduits for peripheral nerve repair
Open this publication in new window or tab >>Development of biosynthetic conduits for peripheral nerve repair
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Peripheral nerve injuries are often associated with significant loss of nervous tissue leading to poor restoration of function following repair of injured nerves. Although the injury gap could be bridged by autologous nerve graft, the limited access to donor material and additional morbidity such as loss of sensation and scarring have prompted a search for biosynthetic nerve transplants.

The present thesis investigates the effects of a synthetic matrix BD™ PuraMatrix™ peptide (BD)hydrogel, alginate/fibronectin gel and fibrin glue combined with cultured rat Schwann cells or human bone marrow derived mesenchymal stem cells (MSC) on neuronal regeneration and muscle recovery after peripheral nerve injury in adult rats.

In a sciatic nerve injury model, after 3 weeks postoperatively, the regenerating axons grew significantly longer distances within the conduits filled with BD hydrogel if compared with the alginate/fibronectin gel. The addition of rat Schwann cells to the BD hydrogel drastically increased regeneration distance with axons crossing the injury gap and entering into the distal nerve stump. However, at 16 weeks the number of regenerating spinal motoneurons was decreased to 49% and 31% in the BD hydrogel and alginate/fibronectin groups respectively. The recovery of the gastrocnemius muscle was also inferior in both experimental groups if compared with the nerve graft. The addition of the cultured Schwann cells did not further improve the regeneration of motoneurons and muscle recovery.

The growth-promoting effects of the tubular conduits prepared from fibrin glue were also studied following repair of short and long peripheral nerve gaps. Retrograde neuronal labeling demonstrated that fibrin glue conduit promoted regeneration of 60% of injured sensory neurons and 52% of motoneurons when compared with the autologous nerve graft. The total number of myelinated axons in the distal nerve stump in the fibrin conduit group reached 86% of the nerve graft control and the weight of gastrocnemius and soleus muscles recovered to 82% and 89%, respectively. When a fibrin conduit was used to bridge a 20 mm sciatic nerve gap, the weight of gastrocnemius muscle reached only 43% of the nerve graft control. The morphology of the muscle showed a more atrophic appearance and the mean area and diameter of fast type fibres were significantly worse than those of the corresponding 10 mm gap group. In contrast, both gap sizes treated with nerve graft showed similar fiber size.

The combination of fibrin conduit with human MSC and daily injections of cyclosporine A enhanced the distance of regeneration by four fold and the area occupied by regenerating axons by three fold at 3 weeks after nerve injury and repair. In addition, the treatment also significantly reduced the ED1 macrophage reaction. At 12 weeks after nerve injury the treatment with cyclosporine A alone or cyclosporine A combined with hMSC induced recovery of the muscle weight and the size of fast type fibres to the control levels of the nerve graft group.

In summary, these results show that a BD hydrogel supplemented with rat Schwann cells can support the initial phase of neuronal regeneration across the conduit. The data also demonstrate an advantage of tubular fibrin conduits combined with human MSC to promote axonal regeneration and muscle recovery after peripheral nerve injury.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2012. 55 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1518
Keyword
Biosynthetic conduit, Mesenchymal stem cells, Nerve graft, Nerve tissue engineering, Peripheral nerve injury, Schwann cells
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-60915 (URN)978-91-7459-476-8 (ISBN)
Public defence
2012-11-27, BiA201, Biologihuset, Umeå Universitet, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2012-11-06 Created: 2012-11-02 Last updated: 2012-11-08Bibliographically approved

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