Date Published: April 25, 2019
Publisher: Public Library of Science
Author(s): D. Kok, C. M. M. Peeters, Z. Mardina, D. L. M. Oterdoom, S. K. Bulstra, A. G. Veldhuizen, R. Kuijer, F. H. Wapstra, Benjamin Elder.
Through the increasing number of minimally invasive procedures in spinal fusion surgery, the complete removal of intervertebral disc (IVD) tissue has become more a challenge. Remaining IVD may interfere with the biological process of bone formation.
In order to establish whether complete removal of IVD tissue will improve or inhibit the fusion process, the effects of different concentrations of extracts of inflamed disc tissue on the mitochondrial activity of mesenchymal stem cells (MSCs), and the capacity to mineralize their extracellular matrix by osteoblasts and differentiated MSCs were tested in vitro.
A MTT assay was conducted to measure the mitochondrial activity of MSCs, and an Alizarin Red S staining quantification assay to measure the deposition of calcium by osteoblasts and differentiated, bone marrow-derived MSCs.
A significantly higher mitochondrial activity was shown in MSCs co-cultured with extracts of IVD tissue (10%, 50%, and 100%) compared with the control group after 48 hours of incubation, indicating that the IVD tissue extracts stimulated the mitochondrial activity of MSCs. This effect appeared to be inversely proportional to the concentration of IVD tissue extract. No significant differences in mineralization by human osteoblasts or differentiated MSCs were found between the samples incubated with IVD tissue extracts (3% and 33%) and the control samples.
Our findings indicate that remaining IVD tissue has more of a stimulating than inhibiting effect on the activity of MSCs. Even if inflammatory cytokines are produced, these do not result in a net inhibition of cellular activity or osteogenic differentiation of MSCs.
The number of spinal fusion surgeries has been increased considerably in the last few decades. For a solid fusion of two vertebrae it is essential to perform a discectomy and remove the tissue of the intervertebral disc (IVD) as well as both the vertebral endplate cartilages. However, during minimally invasive procedures using the transforaminal lumbar interbody fusion technique (TLIF), the complete removal of intervertebral tissue and the vertebral cartilages is a challange[2,3].
The aims of this in vitro study were to evaluate the influence of IVD tissue extracts on (i) the cellular activity of human MCSs, (ii) their osteogenic differentiation, and (iii) the mineral production of osteblasts. The results of this study indicate that IVD tissue extracts might stimulate the cellular activity of MSCs, when present in low concentrations. The results also indicate that IVD tissue extracts have no influence on the osteogenic differentiation of MSCs, and on the mineralizing capacity of mature primary osteoblasts.