• Anita Krouwels, Jelena Popov-Celeketic, Plomp Saskia G M SGM Department of Orthopedics, University Medical Center Utrecht, Utrecht, The Netherlands., Dhert Wouter J A WJA Department of Orthopedics, University Medical Center Utrecht, Utrecht, The Netherlands. , F Cumhur Öner, Ruud A Bank, and Laura B Creemers.
• Department of Orthopedics, University Medical Center Utrecht, Utrecht, The Netherlands.
• Spine. 2018 Mar 1; 43 (5): 307-315.

Study DesignAn in vitro study using human degenerated nucleus pulposus cells.ObjectiveTo determine the effect of osmolality and different osmolytes on the regeneration by human nucleus pulposus cells through gene expression and extracellular matrix production.Summary Of Background DataIntervertebral disc (IVD) degeneration is a major problem in developed countries. Regeneration of the IVD can prevent pain and costs due to diminished work absence and health care, and improve quality of life. The osmotic value of a disc decreases during degeneration due to loss of proteoglycans and might increase degeneration. It is known that gene expression of matrix genes of nucleus pulposus (NP) cells increases when cultured in hyperosmotic medium. Thus, increasing the osmolality of the disc might be beneficial for disc regeneration.MethodsIn the current study, isolated degenerated human NP cells were used in regeneration culture with medium of different osmolalities, adjusted with different osmolytes. NaCl, urea and sucrose. The cells were cultured for 28 days and expression of matrix genes and production of glycosaminoglycans and collagen II were measured.ResultsGene expression for both collagen II and aggrecan increased with increasing osmolality using NaCl or sucrose, but not urea. Protein production however, was not affected by increasing osmolality and was decreased when using urea and sucrose. Expression of genes for Col1A1, MMP13, and MMP14 decreased with increasing osmolality, whereas expression of LOXL2 and LOXL3 increased. Transient expression of TonEBP was found 6 hours after the start of culture, but not at later time points.ConclusionAlthough expression of matrix genes is upregulated, hyperosmolality does not enhance matrix production by nucleus pulposus cells. Raising osmolality can potentially increase matrix production, but in itself is not sufficient to accomplish regeneration in the current in vitro culture system.Level Of EvidenceN /A.

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