Mechanoregulation model of the intervertebral disc

Mechanoregulation model of the intervertebral disc

Citation for published version (APA):

Barthelemy, V. M. P., Huyghe, J. M. R. J., Isaksson, H. E., Wilson, W., & Ito, K. (2010). Mechanoregulation model of the intervertebral disc. Poster session presented at Mate Poster Award 2010 : 15th Annual Poster Contest.

Document status and date: Published: 01/01/2010 Document Version:

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Mechanoregulation model

of the intervertebral disc

Barthelemy V.M.P, Huyghe J.M.R.J, Isaksson H., Wilson W., Ito K.

/ Department of Biomedical Engineering

Introduction

Regenerative therapy is a promising treatment for early intervertebral disc (IVD) degeneration. It may restore tissue functionality via biomaterials containing stem

cells, growth factors or agents blocking tissue

catabolism (Fig. 1).

The long term functional benefit to the disc may be

assessed by computational studies. Up to now,

numerical models of the IVD have only focused on the mechanical behavior of the tissue and the nutrient supply to the cells as two independent mechanisms. However, these two processes are related by the cell activities.

Objective

The goal of this project is to develop a computational mechanoregulation model of a degenerated IVD to evaluate the effectiveness of regenerative strategies.

Methods

The sharp distinction between the outer and inner disc tissue fades away after few days (Fig. 4).

The nutrient concentration model (Fig. 5) shows good correlation with other validated numerical data [3] although extreme values are somewhat overestimated.

Discussion

The variation in the cell type prediction over time might be due to simple assumptions for the mechanical model (axisymmetry, axial load, boundary condition).

In the nutrient concentration model, the extreme values must be improved, discrepancies with other data might be caused by modeling issues.

References

[1] Prendergast et al, J Biomech.,1997.

[2] Isaksson et al, J.Theoretical Biology, 2008. [3] Soukane et al, J. Biomech. Eng, 2005.

• Change in cell phenotype or density • Tissue degeneration • Cells • Growth factors • Anti-catabolic agents

Degeneration

Regenerative

strategies

Fig. 1. Healthy and degenerated disc: Characteristics of a degenerated IVD (left) and potential regenerative strategies (right).

Fig. 2. Schematic representation of the computational model.

LOAD Nutrient concentration material properties Mechanoregulation theory Cell processes Matrix composition Finite Element model Mechanical analysis Finite Element analyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyysis Finite Element model Diffusive analysis Cell analysis 5.8 kPa 0.8 kPa 4.4 mmol/mm3 0.9 mmol/mm3

Fig. 5. Oxygen (left) and lactate (right) concentration at equilibrium. .

Fig. 4. Initial cell phenotypes (left), prediction after 20 days (right).

We are developing an iterative mechanoregulation model (Fig. 2) including:

§ prediction of cell behavior based on their mechanical environment [1][2],

§ influence of nutrient concentration on cell activities, § effect of cells on matrix composition [2].

We apply a physiological compressive load on an axisymmetric model (Fig. 3) of a healthy disc. Initially for model development, the nutrient and cell models are artificially kept independent.

Preliminary results

Fig. 3. Axisymmetric finite element mesh of an intervertebral disc.

Orthopaedic Biomechanics

This research forms part of the Project P2.01 IDiDAS of the research program of the BioMedical Materials institute, co-funded by the Dutch Ministry of Economic Affairs