Periodic Reporting for period 1 - ArthroDUR (Bifunctional and regeneratively active biomaterial: Towards an ultimate solution for osteoarthritis treatment)
Reporting period: 2017-09-01 to 2019-02-28
Summary of the context and overall objectives of the project
Damage of cartilage, especially of the articular cartilage, is a relatively common type of injury, especially cartilage damage of the knee. Impairment of cartilage integrity can also be caused by degenerative processes, an increasing problem in view of our ageing population. Since articular cartilage has only minimal capacity to repair damages it tends to generalize. The symptoms are often described as arthritis, a disorder of the joints and their surrounding tissues, which is characterized by inflammation causing pain and stiffness. Among the two common types of arthritis, osteoarthritis (degenerative joint disease) and rheumatoid arthritis (autoimmune inflammatory disease), osteoarthritis is characterized by a progressive degeneration of articular cartilage. This disorder often leads to disability and is associated with high costs to the healthcare systems resulting in a major economic burden to the society. At present, no effective cure for osteoarthritis exists to slow down or halt the progression of the disease. In order to avoid the development of osteoarthritis and indication of total bone replacement (total arthroplasty), alternative methods have been proposed such as mosaicplasty, osteochondral autologous transplantation, autologous chondrocyte implantation, microfracture, and artificial cartilage fabrication. The aim of this ERC-PoC project was to present an improved product for cartilage regeneration/repair and osteoarthritis prevention based on the experimental results of the ERC Advanced Investigator Grant project BIOSILICA. In this ERC Advanced Grant project we had developed with bio-silica that can be prepared enzymatically using the sponge enzyme silicatein, the first regeneratively active inorganic biomaterial that is capable of eliciting cell differentiation and human tissue regeneration. In this project we also asked the question from where the metabolic energy originates that is needed for the structural and functional organization of the extracellular matrix. Thereby, we discovered another inorganic molecule, inorganic polyphosphate (polyP), that provides the biochemically useful energy in the extracellular space. The discovery of polyP as a “metabolic fuel”, as well as the discovery that this polymer exhibits “morphogenetic activity” (promotion of cell differentiation and proliferation via gene induction) enabled the development of new strategies in tissue engineering of bone and cartilage (regenerative medicine).
Our strategy is based on the combination of these beneficial properties, starting with amorphous micro-particles of the Mg2+/Ca2+ salt of polyP (Mg/Ca-polyP) prepared by a biomimetic fabrication process that follows the route found in nature (imitating the material found in natural occurring acidocalcisomes). This project provides the proof-of-concept of this strategy. Novel hydrogel scaffolds consisting of polyP and selected hydrogel-forming polymers have been developed in order to dissolve bone splinters in the synovial fluid that cause pain in osteoarthritis patients, and to repair damaged cartilage. It should be noted that this strategy does not require the addition of cells to the implant since polyP is able to attract stem cells and, in dependence on the counterion, cause their differentiation either into the osteogenic (Ca-polyP) or chondrogenic lineage (Mg-polyP).
Thus, in the frame of this project, we developed the material for two products:
• A material for an injection solution for treatment of osteoarthritis
• A material for cartilage repair
Both materials are based on regeneratively active Mg-polyP or Ca-polyP.
In the frame of this project we succeeded to develop a novel porous hybrid cryogel consisting of the negatively charged polysaccharide hydrocolloid, karaya gum, and poly(vinyl alcohol) (PVA), into which amorphous Ca-polyP nanoparticles have been incorporated. The cryogel was obtained by Ca2+-mediated ionic gelation of karaya gum and intermolecular cross-linking of PVA via freeze-thawing
We demonstrated that in the presence of Ca2+ ions, amorphous Ca-polyP nanoparticles are formed in situ. The particles had a size of 100-150 nm. Furthermore, we showed that exposure of the stable, spherical Ca-polyP nanoparticles in the cryogel to medium/serum led to the formation of a coacervate. In this coacervate form, the polyP became biologically active and energy-delivering. In addition, it was found that this polyP coacervate attracted cells (human mesenchymal stem cells, MSC) that infiltrated the matrix and started to grow.
The polyP-karaya gum/PVA cryogel exhibits pronounced viscoelastic properties, even nonlinear viscoelastic properties comparable to cartilage. These dynamic properties of the polyP-karaya gum/PVA cryogel are caused by the fact that the two organic polymers are cross-linked via non-covalent bonds, namely hydrogen bonds between the PVA chains and Ca2+ bridges between the negatively charged sugar residues of karaya gum. The non-covalent nature of both linkages provides the cryogel with flexibility and elasticity.
Advantages:
1) Injection material:
• polyP provides the “metabolic fuel” for proliferation and differentiation of the mesenchymal stem cells.
• The counterion Mg2+ allows a “dynamic” exchange with Ca2+, present in the synovial fluid and, by that, ameliorates the osteoarthritis pain (injection).
• Production of “high-molecular weight” hyaluronic acid [HA] by cross-linking the low-molecular weight HA in the synovial fluid.
• Formation of artificial cartilage in the damaged area, based on Mg/Ca-polyP and Ca-polyP.
2) Implantation material:
• Mg/Ca-polyP: upregulation of the key marker genes in chondrocytes that control formation and metabolism of cartilage, e.g. collagens or aggrecan.
• Controlled hardening of the particles to the stiffness of physiological cartilage.
• The stress-strain matching that of physiological cartilage.
Economic and/or societal benefits:
• Degenerative joint diseases are the leading cause of pain and functional impairment in working age adults and the elderly
• These diseases have more than doubled in Europe in the last 10 years and their incidences are rising due to an ageing population.
• In 2015 close to 10 million working days were lost in Germany due to temporary incapacity of workers with musculoskeletal problems causing costs to the society of close to 1 billion €.
• In developed countries, the people who are older than 65 years, about 30% perform hip arthroplasty and about 20% perform knee arthroplasty every year.
• Total hip replacement (hip arthroplasty), consisting of replacement of both the acetabulum and the femoral head, is the most common orthopedic operation.
• The average costs for total hip replacement, e.g. in Germany, are around 10.000 € (implant plus rehabilitation) giving 200,000 implants per year in total, summing up with 2 billion €.
Several dissemination events, both to experts and potential end-users, as well as to the broader public, have been performed.
Our strategy is based on the combination of these beneficial properties, starting with amorphous micro-particles of the Mg2+/Ca2+ salt of polyP (Mg/Ca-polyP) prepared by a biomimetic fabrication process that follows the route found in nature (imitating the material found in natural occurring acidocalcisomes). This project provides the proof-of-concept of this strategy. Novel hydrogel scaffolds consisting of polyP and selected hydrogel-forming polymers have been developed in order to dissolve bone splinters in the synovial fluid that cause pain in osteoarthritis patients, and to repair damaged cartilage. It should be noted that this strategy does not require the addition of cells to the implant since polyP is able to attract stem cells and, in dependence on the counterion, cause their differentiation either into the osteogenic (Ca-polyP) or chondrogenic lineage (Mg-polyP).
Thus, in the frame of this project, we developed the material for two products:
• A material for an injection solution for treatment of osteoarthritis
• A material for cartilage repair
Both materials are based on regeneratively active Mg-polyP or Ca-polyP.
In the frame of this project we succeeded to develop a novel porous hybrid cryogel consisting of the negatively charged polysaccharide hydrocolloid, karaya gum, and poly(vinyl alcohol) (PVA), into which amorphous Ca-polyP nanoparticles have been incorporated. The cryogel was obtained by Ca2+-mediated ionic gelation of karaya gum and intermolecular cross-linking of PVA via freeze-thawing
We demonstrated that in the presence of Ca2+ ions, amorphous Ca-polyP nanoparticles are formed in situ. The particles had a size of 100-150 nm. Furthermore, we showed that exposure of the stable, spherical Ca-polyP nanoparticles in the cryogel to medium/serum led to the formation of a coacervate. In this coacervate form, the polyP became biologically active and energy-delivering. In addition, it was found that this polyP coacervate attracted cells (human mesenchymal stem cells, MSC) that infiltrated the matrix and started to grow.
The polyP-karaya gum/PVA cryogel exhibits pronounced viscoelastic properties, even nonlinear viscoelastic properties comparable to cartilage. These dynamic properties of the polyP-karaya gum/PVA cryogel are caused by the fact that the two organic polymers are cross-linked via non-covalent bonds, namely hydrogen bonds between the PVA chains and Ca2+ bridges between the negatively charged sugar residues of karaya gum. The non-covalent nature of both linkages provides the cryogel with flexibility and elasticity.
Advantages:
1) Injection material:
• polyP provides the “metabolic fuel” for proliferation and differentiation of the mesenchymal stem cells.
• The counterion Mg2+ allows a “dynamic” exchange with Ca2+, present in the synovial fluid and, by that, ameliorates the osteoarthritis pain (injection).
• Production of “high-molecular weight” hyaluronic acid [HA] by cross-linking the low-molecular weight HA in the synovial fluid.
• Formation of artificial cartilage in the damaged area, based on Mg/Ca-polyP and Ca-polyP.
2) Implantation material:
• Mg/Ca-polyP: upregulation of the key marker genes in chondrocytes that control formation and metabolism of cartilage, e.g. collagens or aggrecan.
• Controlled hardening of the particles to the stiffness of physiological cartilage.
• The stress-strain matching that of physiological cartilage.
Economic and/or societal benefits:
• Degenerative joint diseases are the leading cause of pain and functional impairment in working age adults and the elderly
• These diseases have more than doubled in Europe in the last 10 years and their incidences are rising due to an ageing population.
• In 2015 close to 10 million working days were lost in Germany due to temporary incapacity of workers with musculoskeletal problems causing costs to the society of close to 1 billion €.
• In developed countries, the people who are older than 65 years, about 30% perform hip arthroplasty and about 20% perform knee arthroplasty every year.
• Total hip replacement (hip arthroplasty), consisting of replacement of both the acetabulum and the femoral head, is the most common orthopedic operation.
• The average costs for total hip replacement, e.g. in Germany, are around 10.000 € (implant plus rehabilitation) giving 200,000 implants per year in total, summing up with 2 billion €.
Several dissemination events, both to experts and potential end-users, as well as to the broader public, have been performed.