Joern Redeker

Bundles of Spider Silk, Braided into Sutures, Resist Basic Cyclic Tests: Potential Use for Flexor Tendon Repair

Repair success for injuries to the flexor tendon in the hand is often limited by the in vivo behaviour of the suture used for repair. Common problems associated with the choice of suture material include increased risk of infection, foreign body reactions, and inappropriate mechanical responses, particularly decreases in mechanical properties over time. Improved suture materials are therefore needed. As high-performance materials with excellent tensile strength, spider silk fibres are an extremely promising candidate for use in surgical sutures. However, the mechanical behaviour of sutures comprised of individual silk fibres braided together has not been thoroughly investigated. In the present study, we characterise the maximum tensile strength, stress, strain, elastic modulus, and fatigue response of silk sutures produced using different braiding methods to investigate the influence of braiding on the tensile properties of the sutures. The mechanical properties of conventional surgical sutures are also characterised to assess whether silk offers any advantages over conventional suture materials. The results demonstrate that braiding single spider silk fibres together produces strong sutures with excellent fatigue behaviour; the braided silk sutures exhibited tensile strengths comparable to those of conventional sutures and no loss of strength over 1000 fatigue cycles. In addition, the braiding technique had a significant influence on the tensile properties of the braided silk sutures. These results suggest that braided spider silk could be suitable for use as sutures in flexor tendon repair, providing similar tensile behaviour and improved fatigue properties compared with conventional suture materials.

In Vivo Transformation of Neural Stem Cells Following Transplantation in the Injured Nervous System

Johnson et al report tumor formation following murine neural precursor cell transplantation in a rat peripheral nerve injury model, emphasizing the importance of full in vitro characterization of cells prior to transplantation. Cell lines can change during expansion and subclones which may become tumerogenic may be selected in the process of expansion. Cell transplantation studies with committed cells that have been minimally manipulated and expanded in culture such as olfactory ensheathing cells and Schwann cells may pose less risk of tumerogenicity, but have the disadvantage of limited cell harvest yields. The balance between in vitro transformation of expanded cell lines and the limitation of cell harvest yields from preparation of more stable committed cells must be considered in selection of cells for therapeutic intervention for nerve repair.

Antifibrotic medication using a combination of N-acetyl-L-cystein (NAC) and ACE inhibitors can prevent the recurrence of Dupuytren’s disease

Dupuytrens disease is a progress fibromatosis of unknown origin first described in 1831. Nonoperative treatment options have been suggested involving radiation therapy, vitamin E, local injection therapy suing calcium channel blockers, interferon, corticosteroids or collagenase. Transforming growth factor-beta1 (TGF-beta1) and its downstream Smad signalling system is well established as a key player during fibrogenesis. A number of in vitro experiments have been assessed the blockade of TGF-beta1 and TGF-beta 2. Clinically, a number of antifibrotic agents are available such as N-acetyl-L-cysteins (NAC) as well as angiotensin-converting enzyme (ACE) inhibitors or AT II antagonists. However, to date none of the well known substances has been tested clinically in fibromatosis such as Dupuytrens disease especially to prevent recurrences after surgical release. Antifibrotic medication using a combination of N-acetyl-L-cystein (NAC) and ACE inhibitor can prevent the recurrence of Dupyutrens disease. Given the fact that recurrence rate in Dupuytrens disease is high and unpredictable after surgical release, an antifibrotic intervention might be worthwhile to consider in the clinical setting. Antifibrotic agents inhibit TGF-beta1, which play a key role in fibromatosis. Thus, antifibrotic medication might reduce the recurrence rate in fibromatosis such as Dupuytrens disease in a clinical significant way.

Re: Kalbermatten DF, Erba P, Mahay D, Wiberg M, Pierer G, Terenghi G. Schwann cell strip for peripheral nerve repair. J Hand Surg Eur. 2008, 33: 587–94

I read this report with interest. The point that a discrepancy exists between the definition and the diagram of the Wassel (1969) classification of the type IV thumb duplication has been previously described by Light (1992). Light (1992) proposed a modified classification for the original Wassel (1969) classification scheme and paid special attention to the above mentioned point. He proposed and illustrated the hand depicted by Wassel (1969) as type IV would be classified as a type IIIB thumb. I think that the respected author was not aware of Light’s (1992) work, so did not make reference to him.