Abstract
Autologous chondrocyte implantation for cartilage repair represents a challenge because strongly limited by chondrocytes’ poor expansion capacity in vitro. Mesenchymal stem cells (MSCs) can differentiate into chondrocytes, while mechanical loading has been proposed as alternative strategy to induce chondrogenesis excluding the use of exogenous factors. Moreover, MSC supporting material selection is fundamental to allow for an active interaction with cells. Here, we tested a novel thermo-reversible hydrogel composed of 8% w/v methylcellulose (MC) in a 0.05 M Na2SO4 solution. MC hydrogel was obtained by dispersion technique and its thermo-reversibility, mechanical properties, degradation and swelling were investigated, demonstrating a solution-gelation transition between 34 and 37 °C and a low bulk degradation (<20%) after 1 month. The lack of any hydrogel-derived immunoreaction was demonstrated in vivo by mice subcutaneous implantation. To induce in vitro chondrogenesis, MSCs were seeded into MC solution retained within a porous polyurethane (PU) matrix. PU-MC composites were subjected to a combination of compression and shear forces for 21 days in a custom made bioreactor. Mechanical stimulation led to a significant increase in chondrogenic gene expression, while histological analysis detected sulphated glycosaminoglycans and collagen II only in loaded specimens, confirming MC hydrogel suitability to support load induced MSCs chondrogenesis.
Highlights
Autologous chondrocyte implantation for cartilage repair represents a challenge because strongly limited by chondrocytes’ poor expansion capacity in vitro
To mimic natural tissue microenvironment, different bioreactor systems have been developed to reproduce the physiological loading conditions and have been used to investigate cartilaginous tissue formation in vitro[9,10]. These studies have demonstrated that mechanical forces are able to shape the mesenchymal stem cell (MSC) fate when appropriately applied in in vitro models of cartilage regeneration. The concept behind this strategy is that bioreactors can be used to precondition implants before surgery, but they represent an effective tool to study the cellular response to mechanical stimulation under defined conditions[9]
Chondrocytes cultured in poly(ethylene glycol) (PEG) hydrogel enriched with RGD peptides, which can act as a binding site for chondrocytes, showed a general gene expression upregulation under mechanical loading compared to the static cultures[17]
Summary
Autologous chondrocyte implantation for cartilage repair represents a challenge because strongly limited by chondrocytes’ poor expansion capacity in vitro. To mimic natural tissue microenvironment, different bioreactor systems have been developed to reproduce the physiological loading conditions and have been used to investigate cartilaginous tissue formation in vitro[9,10] These studies have demonstrated that mechanical forces are able to shape the mesenchymal stem cell (MSC) fate when appropriately applied in in vitro models of cartilage regeneration. The concept behind this strategy is that bioreactors can be used to precondition implants before surgery, but they represent an effective tool to study the cellular response to mechanical stimulation under defined conditions[9]. In the gel phase, the thermo-responsive hydrogel tends to gel because of the polymer chain network reticulation
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