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Axonal Growth Arrests After an Increased Accumulation of Schwann Cells Expressing Senescence Markers and Stromal Cells in Acellular Nerve Allografts. Tissue Eng Part A 2016 07;22(13-14):949-61

Date

06/15/2016

Pubmed ID

27297909

Pubmed Central ID

PMC4948214

DOI

10.1089/ten.TEA.2016.0003

Scopus ID

2-s2.0-84987617950   31 Citations

Abstract

Acellular nerve allografts (ANAs) and other nerve constructs do not reliably facilitate axonal regeneration across long defects (>3 cm). Causes for this deficiency are poorly understood. In this study, we determined what cells are present within ANAs before axonal growth arrest in nerve constructs and if these cells express markers of cellular stress and senescence. Using the Thy1-GFP rat and serial imaging, we identified the time and location of axonal growth arrest in long (6 cm) ANAs. Axonal growth halted within long ANAs by 4 weeks, while axons successfully regenerated across short (3 cm) ANAs. Cellular populations and markers of senescence were determined using immunohistochemistry, histology, and senescence-associated β-galactosidase staining. Both short and long ANAs were robustly repopulated with Schwann cells (SCs) and stromal cells by 2 weeks. Schwann cells (S100β(+)) represented the majority of cells repopulating both ANAs. Overall, both ANAs demonstrated similar cellular populations with the exception of increased stromal cells (fibronectin(+)/S100β(-)/CD68(-) cells) in long ANAs. Characterization of ANAs for markers of cellular senescence revealed that long ANAs accumulated much greater levels of senescence markers and a greater percentage of Schwann cells expressing the senescence marker p16 compared to short ANAs. To establish the impact of the long ANA environment on axonal regeneration, short ANAs (2 cm) that would normally support axonal regeneration were generated from long ANAs near the time of axonal growth arrest ("stressed" ANAs). These stressed ANAs contained mainly S100β(+)/p16(+) cells and markedly reduced axonal regeneration. In additional experiments, removal of the distal portion (4 cm) of long ANAs near the time of axonal growth arrest and replacement with long isografts (4 cm) rescued axonal regeneration across the defect. Neuronal culture derived from nerve following axonal growth arrest in long ANAs revealed no deficits in axonal extension. Overall, this evidence demonstrates that long ANAs are repopulated with increased p16(+) Schwann cells and stromal cells compared to short ANAs, suggesting a role for these cells in poor axonal regeneration across nerve constructs.

Author List

Poppler LH, Ee X, Schellhardt L, Hoben GM, Pan D, Hunter DA, Yan Y, Moore AM, Snyder-Warwick AK, Stewart SA, Mackinnon SE, Wood MD

Author

Gwendolyn M B Hoben MD Assistant Professor in the Plastic Surgery department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Animals
Axons
Cellular Senescence
Female
Male
Nerve Regeneration
Rats
Rats, Sprague-Dawley
Rats, Transgenic
Schwann Cells
Stromal Cells
Tissue Scaffolds
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a