title: Effects of mechanical loading on the expression of pleiotrophin and its receptor protein tyrosine phosphatase beta/zeta in a rat spinal deformity model.
abstract: Mechanical loading of the spine is a major causative factor of degenerative changes and causes molecular and structural changes in the intervertebral disc (IVD) and the vertebrae end plate (EP). Pleiotrophin (PTN) is a growth factor with a putative role in bone remodeling through its receptor protein tyrosine phosphatase beta/zeta (RPTPβ/ζ). The present study investigates the effects of strain on PTN and RPTPβ/ζ protein expression in vivo. Tails of eight weeks old Sprague-Dawley rats were subjected to mechanical loading using a mini Ilizarov external apparatus. Rat tails untreated (control) or after 0 degrees of compression and 10°, 30° and 50° of angulation (groups 0, I, II and III respectively) were studied. PTN and RPTPβ/ζ expression were evaluated using immunohistochemistry and Western blot analysis. In the control group, PTN was mostly expressed by the EP hypertrophic chondrocytes. In groups 0 to II, PTN expression was increased in the chondrocytes of hypertrophic and proliferating zones, as well as in osteocytes and osteoblast-like cells of the ossification zone. In group III, only limited PTN expression was observed in osteocytes. RPTPβ/ζ expression was increased mainly in group 0, but also in group I, in all types of cells. Low intensity RPTPβ/ζ immunostaining was observed in groups II and III. Collectively, PTN and RPTPβ/ζ are expressed in spinal deformities caused by mechanical loading, and their expression depends on the type and severity of the applied strain.
authors.affiliation: Laboratory of Molecular Pharmacology, School of Health Sciences, University of Patras, Patras 26504, Greece; Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Athens 14561, Greece.
authors.forename: Angelos
authors.initials: A
authors.lastname: Kaspiris
authors.affiliation: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Athens 14561, Greece; Second Department of Orthopaedic Surgery, Konstantopoulio General Hospital and Medical School, University of Athens, Athens 14233, Greece.
authors.forename: Efstathios
authors.initials: E
authors.lastname: Chronopoulos
authors.affiliation: Department of Orthopaedics, Tzanio General Hospital of Piraeus-NHS, Piraeus 18536, Greece.
authors.forename: Theodoros B
authors.initials: TB
authors.lastname: Grivas
authors.affiliation: Third Department of Orthopaedics, KAT General Hospital, School of Medicine, University of Athens, Athens 14561, Greece.
authors.forename: Elias
authors.initials: E
authors.lastname: Vasiliadis
authors.affiliation: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Athens 14561, Greece.
authors.forename: Lubna
authors.initials: L
authors.lastname: Khaldi
authors.affiliation: Laboratory of Molecular Pharmacology, School of Health Sciences, University of Patras, Patras 26504, Greece.
authors.forename: Margarita
authors.initials: M
authors.lastname: Lamprou
authors.affiliation: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Athens 14561, Greece.
authors.forename: Pavlos P
authors.initials: PP
authors.lastname: Lelovas
authors.affiliation: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Athens 14561, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Papaioannou
authors.affiliation: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, Athens 14561, Greece.
authors.forename: Ismene A
authors.initials: IA
authors.lastname: Dontas
authors.affiliation: Laboratory of Molecular Pharmacology, School of Health Sciences, University of Patras, Patras 26504, Greece. Electronic address: epapad@upatras.gr.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Papadimitriou
mesh_terms: D000818:Animals; D017209:Apoptosis; D001696:Biomechanical Phenomena; D002352:Carrier Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D019902:Chondrocytes / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism*; D016267:External Fixators; D007403:Intervertebral Disc / Q000378:metabolism*; D009336:Necrosis; D010006:Osteoblasts / Q000378:metabolism; D010011:Osteocytes / Q000378:metabolism; D010766:Phosphorylation; D017207:Rats, Sprague-Dawley; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5 / Q000378:metabolism*; D015398:Signal Transduction; D013131:Spine / Q000002:abnormalities* / Q000166:cytology / Q000378:metabolism*; D013314:Stress, Mechanical
chemical_list: D002352:Carrier Proteins; D016207:Cytokines; C066845:pleiotrophin; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5
keywords: Deformities; End plate; Intervertebral disc; Mechanical loading; Pleiotrophin; Receptor protein tyrosine phosphatase