On the basis of the similarities in the structure of cartilage and intervertebral disc and on the property of glucosamine of being the building block for the construction of proteoglycan aggregates, we investigated the compound's role in the proliferation of nucleus pulposus cells under iso- and hyperosmotic conditions, the putative activation of signaling cascades, and the induction of glycosaminoglycan production.
We examined the mode of action of glucosamine in nucleus pulposus cells.
Glucosamine that naturally occurs in cartilage tissues has been widely used for treating osteoarthritis, but its role in nucleus pulposus cells is largely unknown.
The effect of glucosamine sulfate on the viability and proliferation of nucleus pulposus cells was assessed by the microculture tetrazolium test (MTT) assay, direct cell counting, and tritiated thymidine incorporation. Changes in the expression and phosphorylation profile of selected proteins were estimated by Western analysis. Glycosaminoglycan production was measured using the Blyscan assay.
We showed that glucosamine sulfate up to 1 mM did not influence the viability, proliferation rate, or novel DNA synthesis of nucleus pulposus cells in the presence or absence of elevated osmolality but induced the transient phosphorylation of p38 mitogen-activated protein kinase. The highest concentration used (10 mM) negatively affected cellular proliferation and resulted in deactivation of extracellular signal-regulated kinases and c-Jun N-terminal kinases. Interestingly, these effects resulted from an additional hyperosmotic stress provoked by glucosamine alone. Finally, we found that a long-term incubation with glucosamine leads to an increase in the glycosaminoglycan content of nucleus pulposus cells.
Glucosamine sulfate was not found to reverse the high osmolality–mediated delay of proliferation in nucleus pulposus cells needed for the maintenance of the tissue's homeostasis. In addition, glycosaminoglycan synthesis stimulated by glucosamine provides a possible promising clinical role for treating disc degenerative disorders.
The effect of glucosamine on several physiological parameters of nucleus pulposus cells was investigated. Glucosamine did not affect cellular proliferation under iso- or hyperosmotic conditions. A long-term incubation of the cells led to an increased glycosaminoglycan synthesis, attributing to the compound a possible clinical role in treating disc degenerative disorders.
From the Laboratory of Cell Proliferation and Ageing, Institute of Biology, National Centre for Scientific Research “Demokritos,” Athens, Greece
Address correspondence and reprint requests to Dimitris Kletsas, PhD, Laboratory of Cell Proliferation and Ageing, Institute of Biology, National Centre for Scientific Research “Demokritos,” 153 10 Athens, Greece; E-mail: firstname.lastname@example.org
Acknowledgment date: March 1, 2012. First revision date: June 12, 2012. Acceptance date: July 16, 2012.
The device(s)/drug(s) is/are FDA approved or approved by corresponding national agency for this indication.
European Union FP7 grant funds (“GENODISC” project, grant agreement no. HEALTH-F2–2008-201626) were received to support this work.
Although one or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript, benefits will be directed solely to a research fund, foundation, educational institution, or other nonprofit organization which the author(s) has/have been associated.