title: Notochordal cell-derived conditioned medium protects human nucleus pulposus cells from stress-induced apoptosis.
abstract: Degenerative disc disease (DDD) remains without an effective therapy and presents a costly burden to society.
  
  
  
  Based upon prior reports concerning the effects of notochordal cell-conditioned medium (NCCM) on disc cells, we performed a proof of principle study to determine whether NCCM could reduce cytotoxic stress-induced apoptosis in human disc nucleus pulposus (NP) cells.
  
  
  
  This is an "in vitro" fundamental or basic science study.
  
  
  
  Nucleus pulpous cells derived from 15 patients undergoing spinal surgery were treated with interleukin (IL)-1β and Fas ligand or etoposide in the presence of NCCM. We determined pro- or antiapoptotic events using activated caspase assays and determined genomic regulation of apoptosis using polymerase chain reaction arrays validated using Western blotting methods. We interrogated cellular apoptotic regulation using JC-1 dye and flow cytometry and performed enzyme-linked immunosorbent assays to evaluate NP inflammatory cytokine secretion.
  
  
  
  Notochordal cell-conditioned medium inhibits cytotoxic stress-induced caspase-9 and -3/7 activities and maintains the mitochondrial membrane potential in human NP cells, thereby suppressing the intrinsic apoptotic pathway. Gene expression analysis revealed the X-linked inhibitor of apoptosis protein as a key player responsible for evading etoposide-induced apoptosis in the presence of NCCM, and we verified these data using Western blotting. Enzyme-linked immunosorbent assay results revealed distinct differences in IL-6 and IL-8 secretions by NP cells in response to etoposide in the presence of NCCM.
  
  
  
  Here we demonstrate for the first time that NCCM reduces cytotoxic stress-induced apoptosis in human NP cells. Soluble factors present in NCCM could be harnessed for the development of novel therapeutics for the treatment of DDD.
authors.affiliation: Krembil Research Institute, Toronto Western Hospital, 60 Leonard Ave, Toronto, Ontario M5T 2S8, Canada; Spine Surgery, University Hospital Basel, Spitalstr. 21, CH-4031 Basel, Switzerland.
authors.forename: Arne
authors.initials: A
authors.lastname: Mehrkens
authors.affiliation: Krembil Research Institute, Toronto Western Hospital, 60 Leonard Ave, Toronto, Ontario M5T 2S8, Canada.
authors.forename: Ajay
authors.initials: A
authors.lastname: Matta
authors.affiliation: Krembil Research Institute, Toronto Western Hospital, 60 Leonard Ave, Toronto, Ontario M5T 2S8, Canada.
authors.forename: Muhammad Zia
authors.initials: MZ
authors.lastname: Karim
authors.affiliation: Krembil Research Institute, Toronto Western Hospital, 60 Leonard Ave, Toronto, Ontario M5T 2S8, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Kim
authors.affiliation: Krembil Research Institute, Toronto Western Hospital, 60 Leonard Ave, Toronto, Ontario M5T 2S8, Canada; Division of Neurosurgery and Spine Program, University of Toronto, Toronto Western Hospital, 399 Bathurst St, Toronto, Ontario M5T 2S8, Canada.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Fehlings
authors.affiliation: Spine Surgery, University Hospital Basel, Spitalstr. 21, CH-4031 Basel, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schaeren
authors.affiliation: Krembil Research Institute, Toronto Western Hospital, 60 Leonard Ave, Toronto, Ontario M5T 2S8, Canada; Division of Neurosurgery and Spine Program, University of Toronto, Toronto Western Hospital, 399 Bathurst St, Toronto, Ontario M5T 2S8, Canada; Division of Orthopaedic Surgery, University of Toronto, Toronto Western Hospital, 399 Bathurst St, Toronto, Ontario M5T 2S8, Canada; Division of Research, Canadian Memorial Chiropractic College, Toronto, Ontario M2H 3J1, Canada. Electronic address: mark.erwin@utoronto.ca.
authors.forename: William
authors.initials: W
authors.lastname: Mark Erwin
mesh_terms: D017209:Apoptosis; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D053222:Fas Ligand Protein / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D009672:Notochord / Q000166:cytology / Q000378:metabolism*; D000070614:Nucleus Pulposus / Q000166:cytology* / Q000187:drug effects; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: D017077:Culture Media, Conditioned; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D015850:Interleukin-6; D016209:Interleukin-8; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human
keywords: Apoptosis; Cell proliferation; Cytokines; Degenerative disc disease; Human nucleus pulposus; Notochordal cell; X-linked inhibitor of apoptotic proteins