Effects of mechanical loading on the expression of pleiotrophin and its receptor protein tyrosine phosphatase beta/zeta in a rat spinal deformity model |
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Affiliation: | 1. Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada;2. Orthopaedic Department, University Hospital, University of Basel, Basel, Switzerland;3. Statistics, Information Technologies, University of Calgary, Calgary, Alberta, Canada;1. CBRL, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, D.F. 04510, Mexico;2. Departamento de Inmunología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, D.F. 04510, Mexico;3. Departamento de Biología Celular y Tisular, Facultad de Medicina, Universidad Nacional Autónoma de México, México, D.F., Mexico;4. Laboratorio de Neurobiología Molecular y Neuroquímica de Adicciones, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñíz, México, D.F., México;5. Departmento de Biología Celular, CINVESTAV-IPN, México, D.F., Mexico |
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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. |
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Keywords: | Deformities End plate Intervertebral disc Mechanical loading Pleiotrophin Receptor protein tyrosine phosphatase |
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