Microenvironments for New Therapies


The MiNT Group bioengineers microenvironments to promote tissue regeneration/functional restoration through modulation of the host response. Pivotal in this strategy is the concept that biodegradable biomaterials can drive inflammation towards either pro- or anti-inflammatory microenvironments. This rational has been consistently followed since 2012, when we first demonstrated that a natural polysaccharide (chitosan, Ch) drives anti-inflammatory macrophage polarization. We have implemented the above strategy to bone injury and intervertebral disc degeneration, progressively focusing on the spine.



1. The development of immunomodulatory biomaterials for bone repair/regeneration
We have put forward the hypothesis that fibrinogen (Fg), which is regarded as a pro-inflammatory and pro-healing molecule, could be used to alter the pro- and anti-inflammatory balance following bone injury, so as to promote bone regeneration. To test this hypothesis we have developed two types of porous scaffolds: in one of them Fg was adsorbed to Ch, while the other was made of 100% Fg.
We have used in vitro models to study the crosstalk between immune cells and mesenchymal stem/stromal cells (MSC), and in vivo models to test the host response. We have demonstrated: i) the impact of different biomaterials and other elements of the microenvironment on the recruitment of MSC by immune cells; ii) the impact of bone injury and the implanted biomaterial on the systemic immune response; iii) the relation between elicited local and systemic immune responses and the bone regenerative outcomes; iv) the possibility of modulating in vivo host immune responses through the use of endogenous pro-resolution mediators (lipoxins and resolvins) incorporated in biomaterial scaffolds.


2. The demonstration that inhibiting inflammation contributes to promoting extracellular matrix synthesis in intervertebral discs
Our hypothesis is that modulation of inflammation associated with intervertebral disc degeneration can be used to stop/revert this process. We have established an ex vivo model of disc degeneration in pro-inflammatory conditions. We have developed nanoparticles of Chitosan/Poly-gamma-glutamic acid with Diclofenac and demonstrated that they reduced pro-inflammatory markers and metaloproteases of bovine discs and up-regulated extracellular matrix genes.
We have explored the immunomodulatory potential of MSCs in disc degeneration. We found that: 1) intravenous injection of MSCs in rats with punctured IVDs reduced hernia size and up-regulated anti-inflammatory cytokines systemically; 2) MSCs are able to reduce the levels of pro-inflammatory markers produced by IVD cells.


3. The development of an injectable system for bone regeneration based on the local release of strontium (Sr).
We have developed a viscoelastic hybrid polymer–ceramic injectable system consisting of an RGD -alginate matrix crosslinked in situ with Sr, incorporating a reinforcement in the form of Sr-rich ceramic microspheres. We have studied the in vitro and in vivo responses. We have also investigated the antimicrobial properties against S. aureus and S. epidermidis, as well as the capacity to modulate the immune response towards a pro-regenerative phenotype (rodent air-pouch model tests). We have demonstrated that the system: i) can be manually injected and sets in situ at body temperature; ii) is able to stimulate MSC osteogenic differentiation; iii) led to an increased bone formation; vi) has antibacterial properties; vi) has the ability to modulate the inflammatory response through M2 macrophage polarization.

Morphology of macrophages differentiated on surfaces can be observed by staining for F-actin filaments (red) and nuclei (green).