Addition of Fibronectin to Alginate Matrix Improves Peripheral Nerve Regeneration in Tissue-Engineered Conduits

Abstract

Schwann cell (SC) transplantation has been proposed to encourage peripheral nerve regeneration, but an optimal SC-carrying matrix would be needed. The aim of this study was to characterize how the addition of fibronectin to alginate would affect the outcome of nerve regeneration promoted by Schwann cells embedded in this matrix. Genetically labeled rat SCs were obtained by lacZ gene transduction. SCs were suspended in alginate hydrogel matrix with/without addition of liquid fibronectin, and their viability and growth in the different types of matrices were assessed in vitro by AlamarBlue assay. In vivo assessment of SC transplantation in the matrix was carried out with poly-3-hydroxybutyrate (PHB) conduits to bridge a sciatic nerve gap. The grafted conduits were harvested at 2, 3, and 6 weeks and assessed for the presence of labeled SCs in relation to regrowing axons. The amount and rate of axonal regeneration were assessed by quantitative immunohistochemistry. Addition of fibronectin to alginate hydrogel improved SC viability and growth profile in vitro. X-Gal staining confirmed that SCs transplanted in PHB conduits were viable throughout the time course, and that the labeled SCs were clearly associated with regenerating axons. The regeneration rate was enhanced when liquid fibronectin was added to the alginate matrix. Furthermore, the presence of SCs also enhanced regeneration and there was an additive effect when both SCs and fibronectin were combined with alginate. In conclusion, the addition of fibronectin to alginate hydrogel matrix contributed to improve nerve regeneration, supporting SC viability and augmenting their effect on axonal growth when transplanted in a bioengineered nerve conduit.

Assessment of Axonal Growth into Collagen Nerve Guides Containing VEGF‐Transfected Stem Cells in Matrigel

“…Both cellular additives were equally effective and superior to the control by all measures of recovery. Finally, in agreement with our results, Mosahebi et al (2003) showed that the regeneration distance at 3 weeks was about 2.5 mm using an empty conduit; elongation was significantly inhibited using an alginate gel even when fibronectin was added, but was augmented when Schwann cells were added to the mixture. Interestingly, the rate of regeneration was 1-2 mm per week, but group differences at 2 or 6 weeks postoperative were absent.…”

“…Other studies have reported negative results on axonal outgrowth with laminin gels (Labrador et al, 1998) or Matrigel (Valentini et al, 1987;Cai et al, 2004). The conventional view is that axons will easily regenerate through a 10-mm interstump gap by 4 weeks postoperative (Williams, 1987;Kim et al, 1994;Lundborg, 2004), but others disagree (Mosahebi et al, 2003). Haastert et al (2006) used Matrigel as a carrier for Schwann cells transfected to produce FGF-2 in silicone chambers over a 15-mm gap.…”

“…The rationale is that Matrigel may provide a scaffold for axonal outgrowth and act as a matrix improving the retention of homologous bone marrow stem cells with or without VEGF transfection. An early time point of 21 days postoperative was selected for study to maximize the ability to detect group differences (Schroder et al, 1993;Lee et al, 2003;Mosahebi et al, 2003;Lundborg, 2004;Tohill et al, 2004).…”

Adenoviral gene transfer of bone morphogenetic protein-7 enhances functional recovery after sciatic nerve injury in rats

“…Schwann cells concurrently synthesize and secrete neurotrophic factors and matrix to guide axon growth and provide a favorable microenvironment for nerve innervation. [25][26][27] In this study, increased proliferation in both Schwann cell and sciatic nerve explants by BMP7 overexpression may explain in part the in vivo beneficial effect of BMP7.…”

Neuregulin 1 Role in Schwann Cell Regulation and Potential Applications to Promote Peripheral Nerve Regeneration

“…Alginate hydrogel provides a sustained and controlled release of neurotrophich factors in vitro and in vivo (Austin, Bower, Kurek, & Muldoon, 1997;Ko, Dixit, Shaw, & Gitnick, 1995) and freeze-dryed alginate supports axonal regeneration across 50-mm gap in the cat sciatic nerve (Suzuki et al, 1999). Moreover, coating of alginate hydrogel with fibronectin, supports SC viability and neuronal regeneration (Mosahebi, Wiberg, & Terenghi, 2003). An ultrapure endotoxin-free low-viscosity alginate with high manuronic content was used for recombinant NRG-1-type II-β3 (human GGF2, CeNes Pharmaceutical USA) delivery in a poly 3-hydroxybutyrate (PHB) polymer conduit to repair 20mm and 40mm gaps in rabbit common peroneal nerve (Mohanna, Young, Wiberg, & Terenghi, 2003).…”