• Sangwook Tim Yoon, Jin Soo Park, Keun S Kim, Jun Li, Emad Samir Attallah-Wasif, William C Hutton, and Scott D Boden.
• Department of Orthopaedic Surgery, Emory University School of Medicine, Atlanta, GA, USA. tim_yoon@emoryhealthcare.org
• Spine. 2004 Dec 1; 29 (23): 2603-11.

Study DesignExperiments using both in vitro tissue culture and in vivo rabbit methods were used to study the effect of Lim Mineralization Protein-1 (LMP-1) on intervertebral disc (IVD) cell production of proteoglycans and bone morphogenetic proteins (BMPs).ObjectivesTo determine the effect of LMP-1 overexpression in IVD cells on the production of proteoglycans and BMPs both in vitro and in vivo and to show that LMP-1 mediates the control of proteoglycan production through its action on BMPs.Summary Of Background DataBecause BMPs are known to increase proteoglycan synthesis and LMP-1 is known to upregulate BMPs in certain cells, it was hypothesized that LMP-1 may increase proteoglycan production in IVD cells.MethodsDMMB, real-time polymerase chain reaction, and ELISA methods were used to quantitate proteoglycan, mRNA, and protein levels, respectively. Noggin was used to block the effect of the adenovirus carrying LMP-1 (AdLMP-1) on proteoglycan synthesis. In vivo experiments using intradiscal AdLMP-1 injection were performed with New Zealand White rabbits. Three weeks later, the mRNA levels of LMP-1, aggrecan, BMP-2, and BMP-7 were measured.ResultsIn vitro experiments revealed that the sulfated glycosaminoglycan (sGAG) and aggrecan mRNA levels were significantly increased with AdLMP-1 treatment. Similarly, BMP-2 and BMP-7 mRNA and protein levels increased significantly, but BMP-4 and BMP-6 levels were unchanged. Noggin blocked the upregulation of proteoglycan by AdLMP-1. In vivo discs injected with AdLMP-1 had significantly elevated levels of LMP-1, BMP-2, and BMP-7 mRNA.ConclusionsLMP-1 overexpression increases disc cell production of proteoglycan, BMP-2, and BMP-7. LMP-1 mediates the control of proteoglycan production through its action on BMP.

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