OrthoLab is our platform for experimental, translational research.
We have two main interests:
1. Research on bone substitutes designed to fill bone defects following fractures or in connection with complex prosthesis failure.
2. Neuroprotection and stimulation of neuronal regeneration following damage to the spinal cord or peripheral nerve.
Translational research is always interdisciplinary. Hence, the experiments are conducted in close collaboration with the groups led by Jöns Hilborn, Department of Chemistry, Ångström Laboratory, Cecilia Persson, Department of Engineering Sciences, Ångström Laboratory, Anna Rostedt-Punga, Department of Neuroscience, Josef Järhult, Department of Medical Biochemistry and Microbiology, Microbiology & Immunology all from Uppsala University and Marianne Jensen-Waern from the Swedish University of Agricultural Sciences. There is an international group collaboration with Robert Nitsch, Department for Cell and Neurobiology at the Johannes Gutenberg University Mainz, Germany.
We try to limit the use of laboratory animals as much as possible, and have therefore replaced many experiments on live animals with experiments on cell or tissue cultures.
The group includes: Brittmarie Andersson, Andrej Bajic, Nils Hailer, Gry Hulsart-Billström, Sune Larsson, Alexander Ossinger, Nikos Schizas and Anders Westermark.
Our goal is to develop new bone substitutes for clinical use where there is a need to grow new bone due to bone loss caused by injury or illness. Two classic examples include bone defects following open fractures – of the lower leg in particular – and major osteolysis caused by the failure of previously inserted joint prostheses. A considerable portion of our work is conducted in collaboration with the Departments for Chemistry and Engineering Sciences at the Uppsala University Ångström Laboratory.
In recent years, our research has focused on developing, refining and evaluating various hydrogels intended for use as a carrier for several bone-stimulating substances. One highly successful concept was to integrate Bone Morphogenetic Protein (BMP) into different hydrogels. The release of BMP molecules appear to be much more effective using these carriers when compared to previously used carriers using bovine collagen. This has resulted in a significantly lower dose of BMP to create the same amount of bone. Furthermore, it has also become clear that BMP can stimulate the healing of bone defects in rodents. Nevertheless, more BMP will no doubt be needed to help heal similar critical defects in humans. In addition, hydrogels lack the mechanical stability that may be needed in a substance intended for use as a bone substitute.
And so we have continued to establish a research chain where calcium phosphate crystals are 3D-printed alongside an absorbent slightly firmer carrier substance. These bone substitutes are evaluated on their mechanical properties, ability to stimulate growth of osteoblasts and consequently bone regeneration and the final ability to reabsorb. The first pre-clinical studies have taken place in recent years. By using micro CT equipment, the formation of bone tissue and the implant’s in vivo behaviour can also be studied in live animals. Not only does the equipment allow for a more accurate assessment of bone tissue, it also involves a substantial reduction in the number of animals needed for these studies.
One additional stage is the development of implants that reduce the risk of prosthetic infections. Prosthetic infections develop as bacteria adhere to the implant, multiply and encapsulate in a greasy mass known as biofilm, thus making them inaccessible to antibiotics. Cemented implants are protected to a certain extent through the use of antibiotics mixed in with the cement. However non-cemented implants – which are becoming more common – are unprotected. We have modified the titanium surfaces and bone substitutes described above using nanometre sized silver “islands”, and are developing resorbable hydrogels containing antibiotics that can be brushed directly onto titanium surfaces. Both strategies will prevent the growth of bacteria and formation of biofilms on non-cemented implants. The strategy can be used both preventatively and as a treatment method for existing infections. We are currently cultivating bacterial strains from patients affected by prosthetic infection on these modified surfaces to investigate whether the bacteria’s growth can be inhibited.
Neuroprotection and regeneration
Spinal cord injury - SCI is an incurable condition with devastating consequences for those affected, especially young patients. The pathophysiology of SCI is categorised by two stages with glia cells playing the main role: In the acute phase endogenous macrophages (called micro glia cells) contribute to secondary neuronal damage: They release neurotoxicity factors and trigger neuronal apoptosis, which aggravate the initial damage. In the chronic phase, microglial cells and astrocytes – another type of glia cell – contribute to the formation of a scar tissue that can restrict axonal regeneration. Another cell type with a complex role is the oligodendrocyte that can express factors that can directly impede the development of new neural pathways. However the role of the glial cells is complex: In some stages, glial cells can actually contribute to regeneration. We only partially understand how these complex processes are regulated.
We follow three strategies in the acute phase of SCI to limit secondary damage to the injured spinal cord.
1. Neuroprotective substances: Several immune response agents have been investigated for the ability to inhibit activation of microglial cells and to improve neuronal survival after spinal injury. We have previously shown that a very promising immune modulator substance, Interleukin-1-antagonist (IL-1RA) prevents activation and proliferation of microglial cells, and IL-1RA promotes both neuronal survival and preservation of myelinated neural pathways.
2. Biomaterials based on hyaluronic acid: Together with material researchers at Ångström, hydro gels are developed as carriers of immune response modifiers such as IL-1RA or growth factors such as neurotrophine-3.
A hydrogel containing IL-1RA or other neuroprotective substances that are applied topically during surgery would be able to secrete high concentrations of medication over a given period. As part of an international collaboration, experiments are being conducted on mice with SCI, where the carriers of neuroprotective substances are being tested in vivo.
3. Small interfering RNA (siRNA): This is a group of double stranded RNA molecules that can supress specific genes and consequently regulate protein expression. Future strategies include RNA interference to supress genes that regulate the expression of various factors that are involved in the secondary injury process following SCI, such as proinflammatory cytokines such as IL-1.
In the chronic SCI phase, we are attempting to promote functional recovery, either by preventing the formation of the glia scar or by circumventing this problem.
1. Transplantation of neural stem cells into the damaged spinal cord counteracts the loss of neurons, reduces the proportion of apoptotic cells and inhibits the activation of microglial cells and astrocytes. Stem cells seem to exert their effects through the release of soluble factors such as Brain-derived neurotrophic factor (BDNF).