Periodic Reporting for period 1 - AptoGEL (AptoGEL: A 3D Platform for Mesenchymal Stem Cell Homing)
Reporting period: 2020-09-01 to 2022-08-31
It is estimated that about 0.5% of the world’s population will require an articular cartilage (AC) intervention at some point in their life. Current treatment options for chondral lesions are only marginally successful, and if left untreated, lead to osteoarthritic (OA) joint disease, one of the major sources of disability world-wide. Many of the common surgical approaches to treat cartilage lesions such as microfracture (MF), are dependent on the efficient migration of cells from the underlying subchondral bone (SB) to ensure successful regeneration of the tissue. However, the extent of cell migration and hence the clinical outcome, is highly variable. To overcome this critical limitation, a scaffold is proposed which uses two key mechanisms to induce stem cell migration. Firstly, the scaffold is composed of granular hydrogels, whose void space naturally facilitates the endogenous migration of mesenchymal stem cells (MSCs). Secondly, some microgels are modified with sulfate groups, to allow the retention of positively charged growth factors (GFs) (e.g. TGFB3 and PDGF-BB). Therefore, hyaluronic acid (HA) was triple-modified with methacrylate groups, transglutaminase (TG)-sensitive peptides and sulfate groups to produce AptoGEL, a new and exciting material with key properties needed for chondral regeneration. We believe this advanced, yet biocompatible material, provides an ideal 3D environment for promoting cell migration and differentiation leading to a fully functional chondral repair.
In conclusion, in this project we were able to transform bulk hydrogels where the cells cannot penetrate into a granular system with cell guidance capabilities. The results demonstrated that our strategy can be easily extrapolated to other tissues and, the most important, the whole system can retain different GFs cocktails depending on the need.
In conclusion, in this project we were able to transform bulk hydrogels where the cells cannot penetrate into a granular system with cell guidance capabilities. The results demonstrated that our strategy can be easily extrapolated to other tissues and, the most important, the whole system can retain different GFs cocktails depending on the need.
The following tasks were performed to produce Aptogel:
- Development of an injectable, cell-friendly cross-linking granular hydrogel: several conditions to chemically modify hyaluronic acid were evaluated to render a material with two different cross-linking mechanisms (i.e. UV.Vis and enzymatic). Also, two sizing grids (20 µm and 150 µm) were explored to achieve two sizes of microgels. The effect of microgel size was studied on cell migration and chondrogenesis afterwards.
- Demonstration of enhanced cell migration: first, a protocol to study cell infiltration was designed based on spheroid migration assays. The assay allowed us to compare cell migration in the three developed conditions bulk hydrogels, sized with 20 µm and 150 µm grids. Also, real-time cell migration was recorded to determine cell speed, travelled distance and linearity. This gave insights into how granular hydrogels facilitate cell infiltration. It was noted that smaller microgel size significantly promotes cell colonization.
- Guiding cell behaviour: it is essential to guide cells to achieve hydrogel colonization and instruct them to undergo chondrogenesis and repair the damaged cartilage tissue. For that reason, sulfate groups were grafted to HA, and sulfated microgels were mixed with non-sulfated HA microgels to obtain a heterogenous granular hydrogel with GFs depots. Increasing the negative charge gives the possibility to retain positively charged GFs (i.e. TGFB-3 and PDGF-BB). Their successful retention was proven by ELISA and by visualizing cell preference towards GF-loaded sulfated microgels.
- Chondrogenesis: another requirement of the developed material was its ability to promote chondrogenesis. The presented material led to hBMSCs differentiation into chondrocytes, enhanced the production of glycosaminoglycans, collagen 2 and presented a high increase in stiffness over maturation.
The scientific results were recently submitted for publication, and the experienced researcher (ER) also contributed to other scientific collaborations. Additionally, to the dissemination in scientific journals, the project and its results were shared in one national and three international congresses. Also, the ER, Dr. Puiggali-Jou, shared her activities on social media (twitter) for the academic and non-academic public.
Altogether, the Aptogel project represented an outstanding research programme that helped the ER to develop her interdisciplinary career, to improve her communication and interpersonal skills, and to split her scientific knowledge and expertise with the academic and non-academic public.
- Development of an injectable, cell-friendly cross-linking granular hydrogel: several conditions to chemically modify hyaluronic acid were evaluated to render a material with two different cross-linking mechanisms (i.e. UV.Vis and enzymatic). Also, two sizing grids (20 µm and 150 µm) were explored to achieve two sizes of microgels. The effect of microgel size was studied on cell migration and chondrogenesis afterwards.
- Demonstration of enhanced cell migration: first, a protocol to study cell infiltration was designed based on spheroid migration assays. The assay allowed us to compare cell migration in the three developed conditions bulk hydrogels, sized with 20 µm and 150 µm grids. Also, real-time cell migration was recorded to determine cell speed, travelled distance and linearity. This gave insights into how granular hydrogels facilitate cell infiltration. It was noted that smaller microgel size significantly promotes cell colonization.
- Guiding cell behaviour: it is essential to guide cells to achieve hydrogel colonization and instruct them to undergo chondrogenesis and repair the damaged cartilage tissue. For that reason, sulfate groups were grafted to HA, and sulfated microgels were mixed with non-sulfated HA microgels to obtain a heterogenous granular hydrogel with GFs depots. Increasing the negative charge gives the possibility to retain positively charged GFs (i.e. TGFB-3 and PDGF-BB). Their successful retention was proven by ELISA and by visualizing cell preference towards GF-loaded sulfated microgels.
- Chondrogenesis: another requirement of the developed material was its ability to promote chondrogenesis. The presented material led to hBMSCs differentiation into chondrocytes, enhanced the production of glycosaminoglycans, collagen 2 and presented a high increase in stiffness over maturation.
The scientific results were recently submitted for publication, and the experienced researcher (ER) also contributed to other scientific collaborations. Additionally, to the dissemination in scientific journals, the project and its results were shared in one national and three international congresses. Also, the ER, Dr. Puiggali-Jou, shared her activities on social media (twitter) for the academic and non-academic public.
Altogether, the Aptogel project represented an outstanding research programme that helped the ER to develop her interdisciplinary career, to improve her communication and interpersonal skills, and to split her scientific knowledge and expertise with the academic and non-academic public.
In this ambitious project, granular hydrogels were investigated to deliver an injectable, in-situ cross-linkable and cell-guiding material. This new material's main aim was to achieve a one-step procedure for chondral repair and reduce overall surgical costs. Therefore, this project represents an essential contribution to the field of biocompatible materials for chondral repair.
The main achievements can be summarized as follow:
1. Demonstration that granular hydrogels are an excellent material to promote cell colonization and present injectability, stability and cell-friendly cross-linking.
2. The production of a new generation of heterogeneous granular hydrogels with modulating cell adhesive properties by incorporating sulfated microgels. This point represents a crucial goal in the biomedical field because it will allow to strongly guide cells to induce endogenous repair.
3. A facile approach towards the production of granular hydrogels by consolidating the use of mechanical sizing to produce microgels in an easy, scalable and clean methodology.
4. The obtention of a GFs controlled release system.
5. The project opened new possibilities of study: the incorporation of different GFs cocktails depending on the tissue to repair.
Additionally, the socio-economic impact and the societal implications of the Aptogel project are addressed to the people suffering from chondral lesions. First, the idea is to provide a material that will require lower operation time and costs and be minimally invasive. Therefore, the quality of people's life who undergo chondral repair surgery could considerably be improved, thanks to such a new product capable of reducing operative costs and improving the integration of the hydrogel with the human tissue. From an economic point of view, a surgical material with innovative performances could be placed on the market, causing a benefit to the economy. Finally, reducing surgical recurrences would limit the costs of purchasing materials in hospitals and medical centres, bringing essential advantages to the healthcare sector. Thus, the potential users of this novel material will be health institutions.
Altogether constitutes a significant innovation in the biomedical field of injectable materials for chondral repair.
The main achievements can be summarized as follow:
1. Demonstration that granular hydrogels are an excellent material to promote cell colonization and present injectability, stability and cell-friendly cross-linking.
2. The production of a new generation of heterogeneous granular hydrogels with modulating cell adhesive properties by incorporating sulfated microgels. This point represents a crucial goal in the biomedical field because it will allow to strongly guide cells to induce endogenous repair.
3. A facile approach towards the production of granular hydrogels by consolidating the use of mechanical sizing to produce microgels in an easy, scalable and clean methodology.
4. The obtention of a GFs controlled release system.
5. The project opened new possibilities of study: the incorporation of different GFs cocktails depending on the tissue to repair.
Additionally, the socio-economic impact and the societal implications of the Aptogel project are addressed to the people suffering from chondral lesions. First, the idea is to provide a material that will require lower operation time and costs and be minimally invasive. Therefore, the quality of people's life who undergo chondral repair surgery could considerably be improved, thanks to such a new product capable of reducing operative costs and improving the integration of the hydrogel with the human tissue. From an economic point of view, a surgical material with innovative performances could be placed on the market, causing a benefit to the economy. Finally, reducing surgical recurrences would limit the costs of purchasing materials in hospitals and medical centres, bringing essential advantages to the healthcare sector. Thus, the potential users of this novel material will be health institutions.
Altogether constitutes a significant innovation in the biomedical field of injectable materials for chondral repair.