title: Limited regeneration in long acellular nerve allografts is associated with increased Schwann cell senescence.
abstract: Repair of large nerve defects with acellular nerve allografts (ANAs) is an appealing alternative to autografting and allotransplantation. ANAs have been shown to be similar to autografts in supporting axonal regeneration across short gaps, but fail in larger defects due to a poorly-understood mechanism. ANAs depend on proliferating Schwann cells (SCs) from host tissue to support axonal regeneration. Populating longer ANAs places a greater proliferative demand on host SCs that may stress host SCs, resulting in senescence. In this study, we investigated axonal regeneration across increasing isograft and ANA lengths. We also evaluated the presence of senescent SCs within both graft types. A sciatic nerve graft model in rats was used to evaluate regeneration across increasing isograft (~autograft) and ANA lengths (20, 40, and 60 mm). Axonal regeneration and functional recovery decreased with increased graft length and the performance of the isograft was superior to ANAs at all lengths. Transgenic Thy1-GFP rats and qRT-PCR demonstrated that failure of the regenerating axonal front in ANAs was associated with increased levels of senescence related markers in the graft (senescence associated β-galactosidase, p16(INK4A), and IL6). Lastly, electron microscopy (EM) was used to qualitatively assess senescence-associated changes in chromatin of SCs in each graft type. EM demonstrated an increase in the presence of SCs with abnormal chromatin in isografts and ANAs of increasing graft length. These results are the first to suggest that SC senescence plays a role in limited axonal regeneration across nerve grafts of increasing gap lengths.
authors: Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, MO 63110, USA.
authors: Maryam
authors: M
authors: Saheb-Al-Zamani
authors: Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, MO 63110, USA.
authors: Ying
authors: Y
authors: Yan
authors: Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, MO 63110, USA.
authors: Scott J
authors: SJ
authors: Farber
authors: Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, MO 63110, USA.
authors: Daniel A
authors: DA
authors: Hunter
authors: Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, MO 63110, USA.
authors: Piyaraj
authors: P
authors: Newton
authors: Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, MO 63110, USA.
authors: Matthew D
authors: MD
authors: Wood
authors: Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8228, St. Louis, MO 63110, USA.
authors: Sheila A
authors: SA
authors: Stewart
authors: Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, MO 63110, USA.
authors: Philip J
authors: PJ
authors: Johnson
authors: Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, MO 63110, USA.
authors: Susan E
authors: SE
authors: Mackinnon
mesh_terms: D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D002843:Chromatin / Q000473:pathology / Q000648:ultrastructure; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins; D008297:Male; D046529:Microscopy, Electron, Transmission; D009416:Nerve Regeneration / Q000502:physiology*; D009469:Neuromuscular Junction / Q000502:physiology; D051381:Rats; D011917:Rats, Inbred Lew; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D020127:Recovery of Function / Q000502:physiology*; D009418:S100 Proteins / Q000378:metabolism; D012583:Schwann Cells / Q000502:physiology* / Q000637:transplantation* / Q000648:ultrastructure; D012584:Sciatic Nerve / Q000473:pathology / Q000637:transplantation* / Q000648:ultrastructure; D020426:Sciatic Neuropathy / Q000601:surgery; D014184:Transplantation, Homologous / Q000379:methods; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D002843:Chromatin; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009418:S100 Proteins; D049452:Green Fluorescent Proteins; D001616:beta-Galactosidase; D053148:Caspase 3
keywords: 4′,6-diamidino-2-phenylindole; ANAs; Acellular nerve allograft; Cellular senescence; DAPI; EDL; GFP; Nerve autograft; Nerve grafting; Peripheral nerve; SCs; Schwann cell senescence; Schwann cells; SenScs; acellularized nerve allografts; extensor digitorum longus; green fluorescent protein; senescent Schwann cells
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