Low back pain is a widespread disorder, with tremendous socioeconomical impact. While this condition is multifactorial, intervertebral disc degeneration is one of its main causes. Actual treatments are only symptomatic (to alleviate pain) and new therapies are needed. Disc degeneration is characterized by the inability of the resident cells to keep the disc tissue intact due to a change of their phenotype and their decreasing number. Thus, delivery of exogenous cells may help. The disc originally contains two distinct cell populations: the nucleus pulposus cells (NPCs, chondrocyte-like cells) and the notochordal cells (NCs). Because NCs do not exist in human adults, regenerative therapies have only focused on using chondrocyte-like cells, e.g. adult mesenchymal stem cells (MSCs). However, their transplantation has been of limited success as disc degeneration was only inhibited and not reversed. We believe that this failure is in part due to inability of the transplanted cells to produce enough/appropriate disc matrix to restore tissue properties.

Using an innovative approach, we propose to mimic the natural cell combination of a developing disc, i.e. NCs and NPCs/MSCs, when the largest amount of matrix is produced. Different approaches will be tested for their efficacy using a succession of model systems moving from higher volume:cost ratio systems to more realistic but lower volume:costs systems. Another novelty of our approach will be to use the canine model in which disc degeneration is a frequent spontaneous spinal disease and whose NCs, NPCs and MSCs are readily available.

First, canine NCs, NPCs and MSCs (used to complement the decreasing disc cell population) will be combined in different co-culture systems to compare the ability of various cell combinations to stimulate the production of an appropriate disc matrix. We will also determine if the NCs directly contribute to matrix production or regulate other cells through biochemical signals. The most successful concepts will be further developed pre-clinically in experimental dogs with early stage spontaneous disc degeneration. Finally as proof of principle, a clinical study will be performed in client-owned canine patients with disc disease as the basis for a trial to be set up in human patients. In parallel with this sequential approach, the applicability of our findings to human cells will be demonstrated and if the NC regulatory effects are mediated through soluble factors, these will be identified for further exploitation. This project will (1) provide new and important insights on the role of NCs in disc regeneration and (2) may provide a new biological therapy to treat one of the most common disorders in modern society.

• prof. dr. B.P. (Bjorn) Meij
• dr. F.C. (Frances) Bach
• prof. dr. M.A. (Marianna) Tryfonidou

• Prof. dr. Keita Ito (TU/e)
• dr. Laura Creemers (UMCU)
• Ing. Stefan de Vries (TU/e)
• Ing. Irene Arkensteijn (TU/e)
• dr. Esther Potier (TU/e)

Despite numerous advances in the treatment of the diseased / damaged musculo-skeletal system, the field of clinical orthopedics is still challenged by the treatment of large bone defects. One major problem of bone Regenerative Medicine (RM) is that osteoblasts are metabolically highly demanding. Due to the lag-time of vascularization, hypoxia and nutrient deficiency occur within the construct and result into decreased proliferation of the seeded osteoblasts and into reduction of the matrix (quality and quantity) produced by the osteoblasts.

Contrary, chondrocytes are specialized in surviving without direct blood supply, proliferate optimally and produce better matrix (quality and quantity) under hypoxic conditions. This physiologic aspect can bethe solution to the problem of bone RM. Chondrocyte-based bone formation may conquer the strenuous conditions within large bone defects and complicated fracture healing. Therefore, novel successful strategies in bone RM are based on the understanding of the mechanisms by which the extensive network of local signaling pathways facilitates the cross-talk of chondrocytes, osteoblasts, and osteoclasts during endochondral bone formation.

Key objective of this proposal is to study local networks that define an accelerated pace of endochondral bone formation. This proposal studies the orderly occurring endochondral bone formation at the growth plate level. Dogs represent an excellent model for studying this process. They reveal large growth disparity between breeds, and hence distinct physiological differences in the rate of endochondral bone formation. The distal growth plate of the ulna from growing large and small breed dogs is studied with a two-colour microarray experiment. The data-set is validated for its biological significance by 

1. studying the osteogenic potential of the selected novel pathways in the chondrocytic lineage of canine and human MSCs through endochondral bone formation.
2. comparing the protein expression pattern in the canine and human growth plate
3. studying the expression pattern of the potent target or its ligand, that is crucial in determining a higher pace of endochondral bone formation, in fracture healing of critical bone defects.

The obtained knowledge can be further employed in translational RM to develop rational-driven therapies for amending endochondral bone formation during fracture healing or in cell-seeded scaffolds employed in large bone defects in human and veterinary patients.

• prof. dr. M.A. (Marianna) Tryfonidou

• dr. Laura Creemers
• Prof. dr. Wouter Dhert

Do not remove…

The spinal column has a heavy task. It protects our spinal cord and its nerves, carries our body weight, supports the head and absorbs the shocks resulting from physical exercise. No wonder that lower back pain is a very common problem. Two out of three Dutch people will be confronted with this problem during their lifetime. Some people have chronic lower back pain. An important cause of chronic back pain is wear and tear of the intervertebral disc, the soft disc between the vertebrae that together form the spinal column. This degeneration of the intervertebral disc develops due to a previously incurred hernia or gradual wear and tear. Current treatments for lower back pain require the replacement of afflicted vertebrae with bone from elsewhere in the body, or replacement by intervertebral disc prostheses. In both cases, the entire intervertebral disc is removed and only the symptoms are suppressed. These operations also carry risks, such as further damage to the adjacent intervertebral disc, and persistent pain at the sites where the bone was removed.

... but repair

The purpose of this study is to determine how the function of the degenerated intervertebral disc can be repaired instead of removed. If the degeneration of a vertebral disc is not far advanced, a treatment could consist of injectable, biodegradable materials that release drugs over a longer period of time, thereby stimulating the self-recovery of the intervertebral disc. The materials for the incorporation and release of these compounds may be watery gels, very small spheres (microparticles) or a combination of these two. Next to this, methods are being developed to repair the outside of the intervertebral disc to ensure the injected materials will not diffuse out of the disc. These methods are based on a biodegradable plaster.

A unique aspect of this project is the investigation into the ethical aspects of these new self-repair methods and the moral guidelines for implementing these techniques in patients.

• prof. dr. M.A. (Marianna) Tryfonidou
• dr. N. (Nicole) Willems
• dr. A.R. (Anna) Tellegen
• prof. dr. B.P. (Bjorn) Meij

• dr LB Creemers
• prof dr K Ito
• prof dr T Smit
• InGell BV.
• DSM
• TNO