Tuning the Porosity of Collagen-based Scaffolds for Use as Nerve Regenerative Templates

Abstract

Regenerative medicine aims at inducing the formation of physiological tissues, in cases where the spontaneous healing response following a severe injury or disease leads to wound closure via contraction and synthesis of scar or fibrotic tissue. The suppression of both wound contraction and scar synthesis, with the simultaneous synthesis of physiological tissues, might be achieved by implanting a porous macromolecular scaffold within the site of injury, able to host cells and guide their behavior toward regeneration. Tubular scaffolds, reconnecting the proximal and distal stumps of a transected peripheral nerve, demonstrated to be able to induce regeneration of the lost nerve trunk. Experimental evidence from independent investigations shows that protein-permeable porous tubes, of different types, perform better as regenerative templates when their pore size is also cell-permeable (>10 μm). Moreover, the regenerative potential of the porous conduit may be further enhanced when inserting a substrate with longitudinally oriented pores within it, since such an oriented construct provides physical support and guide to the growth of neural structures across the site of injury. This study focused on the production of collagen-based conduits and matrices with a micropatterned porosity, suitable for use as nerve regenerative templates. The manufacturing techniques for the production of tubular and cylindrical scaffolds, with controlled pore size and orientation, were based on a freeze-drying process. Tubular scaffolds possessed a radially oriented porosity with a radial gradient of pore sizes, ranging from cell-permeable pores at the inner tube wall to cell-impermeable pores at the outer one. Cylindrical scaffolds exhibited nearly axially oriented pores, with a pore size depending on the freezing rate as well as on the collagen concentration. Due to their peculiar porous structures, such scaffolds are expected to enhance the regenerative capacity of transected peripheral nerves as well as to lead to a better understanding of the cellular mechanisms underlying peripheral nerve regeneration.

Keywords

tissue engineering collagen freeze-drying porosity.

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References

Yannas, I.V. (2001). Tissue and Organ Regeneration in Adults, Springer, NY, 2001.

Stevenson, T.R. , Kadhiresan, V.A. and Faulkner, J.A. (1994). Tubular Nerve Guide and Epineurial Repair: Comparison of Techniques for Neurorrhaphy , J. Reconstr. Microsurg., May; 10(3): 171-174.

Harley, B.A. and Yannas, I.V. (2006). Induced Peripheral Nerve Regeneration Using Scaffolds, Minerva Biotechnologica , 19: 97-120.

Chamberlain, L.J. , Yannas, I.V. , Hsu , H.P. , Strichartz, G. and Spector, M. (1998). Collagen-GAG Substrate Enhances the Quality of Nerve Regeneration through Collagen Tubes Up to Level of Autograft, Exp. Neurol., December; 154(2): 315-329.

Rodriguez, F.J. , Gomez, N. , Perego , G. and Navarro, X. (1990). Highly Permeable Polylactide-Caprolactone Nerve Guides Enhance Peripheral Nerve Regeneration Through Long Gaps, Biomaterials, August; 20(16): 1489-1500.

Jenq, C.B. and Coggeshall, R.E. (1987). Permeable Tubes Increase the Length of the Gap that Regenerating Axons can Span, Brain Res., 7 April; 408(1-2): 239-242.

Jenq, C.B. , Jenq, L.L. and Coggeshall, R.E. (1987). Nerve Regeneration Changes with Filters of Different Pore Size, Exp. Neurol., September; 97(3): 662-671.

Aebischer, P. , Guenard, V. , Winn , S.R. , Valentini, R.F. and Galletti, P.M. (1988). Blind-ended Semipermeable Guidance Channels Support Peripheral Nerve Regeneration in the Absence of a Distal Nerve Stump, Brain Res., June 28; 454(1-2): 179-187.

Lundborg, G. , Dahlin, L.B. and Danielsen , N. (1991). Ulnar Nerve Repair by the Silicone Chamber Technique. Case Report, Scand. J. Plast. Reconstr. Surg. Hand. Surg. , 25(1): 79-82.

10.

Chamberlain, L.J. , Yannas, I.V. , Hsu , H.P. , Strichartz, G.R. and Spector, M. (2000). Near-Terminus Axonal Structure and Function Following Rat Sciatic Nerve Regeneration Through a Collagen-GAG Matrix in a Ten-millimeter Gap, J. Neurosci. Res., 1 June; 60(5): 666-677.

11.

Yannas, I.V. , Orgill, D.P. , Silver , J. , Norregaard, T.V. , Zervas, N.T. and Schoene, W.C. (1985). Polymeric Template Facilitates Regeneration of Sciatic Nerve Across 15 mm Gap, Trans. Soc. Biomater., 8: 146.

12.

Yannas, I.V. , Orgill, D.P. , Silver, J. , Norregaard, T.V. , Zervas, N.T. and Schoene, W.C. (1987). Regeneration of Sciatic Nerve Across 15-mm Gap by Use of a Polymeric Template. In: Gebelein, C.G. (ed.), Advances in Biomedical Materials, pp. 1-9. American Chemical Society, Washington, DC.

13.

O'Brien, F.J. , Harley, B.A. , Yannas , I.V. and Gibson, L. (2004). Influence of Freezing Rate on Pore Structure in Freeze-Dried Collagen-GAG Scaffolds, Biomaterials, March; 25(6): 1077-1086.

14.

Harley, B.A. , Spilker, M.H. , Wu , J.W. , Asano, K. , Hsu , H.P. , Spector, M. et al. (2004 ). Optimal Degradation Rate for Collagen Chambers Used for Regeneration of Peripheral Nerves Over Long Gaps, Cells Tissues Organs , 176(1-3): 153-165.

15.

Chamberlain, L.J. , Yannas, I.V. , Arrizabalaga , A. , Hsu , H.P. , Norregaard, T.V. and Spector, M. (1998). Early Peripheral Nerve Healing in Collagen and Silicone Tube Implants: Myofibroblasts and the Cellular Response, Biomaterials, August; 19(15): 1393-1403.

16.

Chamberlain, L.J. , Yannas, I.V. , Hsu , H.P. and Spector, M. (2000). Connective Tissue Response to Tubular Implants for Peripheral Nerve Regeneration: The Role of Myofibroblasts , J. Comp. Neurol., 21 February; 417(4): 415-430.

17.

Yannas, I.V. , Harley, B.A. , Hastings, A.Z. , Sannino A. and Inventors. (2006). Novel Technique to Fabricate Molded Structures Having a Patterned Porosity . US Patent No. WO 2006/047758 A1.

18.

Lamm, O. (1929). Die Differentialgleichung der Ultrazentrifugierung, Ark. Mat. Astr. Fys., 21B(2): 1-4.

19.

Madaghiele, M. , Sannino, A. , Yannas , I.V. and Spector, M. (2008). Collagen-based Matrices with Axially Oriented Pores, J. Biomed. Mater. Res., 85A: 757-767.

20.

Chang, A.S.P. , Yannas, I.V. , Krarup , C. , Sethi, R. , Norregaard, T.V. and Zervas, N.T. (1988). Polymeric Templates for Peripheral Nerve Regeneration. Electrophysiological Study of Functional Recovery, Proc. ACS Div. of Polymeric Materials: Sci. and Engr., 59: 906-910.

21.

Harley, B.A. , Hastings, A.Z. , Yannas, I.V. and Sannino, A. (2006). Fabricating Tubular Scaffolds with a Radial Pore Size Gradient by a Spinning Technique, Biomaterials, February; 27(6): 866-874.

22.

Chamberlain, L.J. and Yannas, I.V. (1999). Preparation of Collagen-Glycosaminoglycan Copolymers for Tissue Regeneration. In: Morgan, J.R. and Yarmush, M.L. (eds), Tissue Engineering Methods and Protocols. Humana Press , Totowa, NJ, pp. 3-17.

23.

Yannas, I.V. and Tobolsky, A.V. (1967). Cross-linking of Gelatine by Dehydration, Nature, 215: 509-510.

24.

Yannas, I.V. (1972). Collagen and Gelatin in the Solid State, J. Macromol. Sci. Revs. Macromol. Chem. , C7: 49-104.

25.

O'Brien, F.J. , Harley, B.A. , Yannas , I.V. and Gibson, L.J. (2005). The Effect of Pore Size on Cell Adhesion in Collagen-GAG Scaffolds, Biomaterials , February; 26(4): 433-441.

26.

Loree, H.M. (1988). A Freeze-Drying Process for Fabrication of Polymeric Bridges for Peripheral Nerve Regeneration [M.S.], Massachusetts Institute of Technology, Cambridge.

27.

Chang, A.S.P. (1988). Electrophysiological Recovery of Peripheral Nerves Regenerated by Biodegradable Polymer Matrix, Massachusetts Institute of Technology, Cambridge.

28.

Yunoki, S. , Ikoma, T. , Monkawa, A. , Ohta, K. , Kikuchi, M. , Sotome, S. et al. (2006). Control of the Pore Structure and Mechanical Property in Hydroxyapatite/Collagen Composite Using Unidirectional Ice Growth, Mater. Lett., 60: 999-1002.