Tissue engineering (TE) has been defined as the science of persuading a body to reconstruct those tissues and/or organs that are not capable of spontaneously regeneration. In one of the possible approaches to this aim, living cells are used to generate ex-vivo implantable structures, which could cover losses of tissues (e.g., as a result of trauma or tumor surgery), or replace non-functional organs (e.g., to overcome the problem of the reduced availability of organs from healthy donors). Anyway, the possible impact of this field is much wider: in the future, the engineered tissues could not only reduce the need for organs to be transplanted, but may also constitute model systems of tissues ex vivo, which would allow speeding up the development of new medicaments and the research for new therapies, in order to improving the tissue regeneration.
In order to engineering tissues in vitro, specific types of cells (stem, progenitor, differentiated cells) are cultured on bio-active degradable supports having the chemical physical characteristics that allow the cells themselves to differentiate and generate three-dimensional tissue structures (scaffolds).
In this context, our research activity combines interdisciplinary expertise in cell biology, biomedical engineering and materials science towards the generation of human cell-based three-dimensional (3D) tissues. The activity is carried out in collaboration with the Stem Cell laboratory of Prof. Rodolfo Quarto of the University of Genoa, placed at Advanced Biotechnology Center (CBA) of Genoa.
Adult bone marrow contains multipotent mesenchymal stem cells (MSCs) that can differentiate into different mesenchymal lineages and whose end-stage cells fabricate bone, cartilage, tendon, fat, and other connective tissues, depending on the three-dimensional scaffolds used to guide the cells during repair or regeneration of the tissue.
In the modern medicine, the tissue engineering approach has been practicing in the development of clinical devices and tissue-substitute materials, which still present physical and biological constrains. Engineered tissue should guarantee the main characteristics of the natural tissue (i.e. bone, cartilage, tendon).
Although the approach is promising, current therapies still present some important drawbacks, which include complicated logistics for in vitro cell expansion, non satisfactory biomaterials for their clinical use, limited and slow tissue ingrowth in 3D constructs.
Starting from these considerations, the group is actively interested to these topics:
a) design, engineering and development of 3D biomaterials as tissue substitutes (i.e. bone, cartilage and osteochondral substitutes);
b) design and development of innovative bioreactor systems for stem/progenitor cell culture in 3D environment under proper physical stimulations
c) innovative tissue engineering approaches for in vivo tissue regeneration.
The engineered constructs are being developed (i) as grafts for the treatment of traumas/diseases of the musculoskeletal system, and/or (ii) as 3D model systems to investigate fundamental aspects of cell differentiation and tissue development under controlled and defined conditions.
With reference to stem/progenitor cells, we investigate the role of physical forces and culture substrate material on maintenance of stem cell properties and induction of lineage-specific differentiation. Different bioreactor-based techniques have been also developed in our laboratory, (some of them also patented), to expand progenitor/stem cells within 3D natural/synthetic scaffolds under controlled physical stimuli. The bioreactor systems should support the possibility to expand and co-culture different cells type in 3D environments, under a multiple biomechanical stimulation (perfusion fluid flow, torsion/traction, air/fluid compression). From a clinical standpoint, we aim at developing a safe, standardized, scalable and possibly cost-effective therapeutical processes based on the 3D culture of stem cells within specialized, closed, controlled and automated bioreactor systems.
Engineering and development of biomaterials substitutes (i.e. bone, cartilage and osteochondral substitutes)
In principle, an ideal bone substitute should have an osteoinductive potential, defined as the “induction of undifferentiated inducible osteoprogenitor cells that are not yet committed to the osteogenic lineage to form osteoprogenitor cells”.
Until now, no adequate bone substitute has been developed and hence large bone defects/injuries still represent a major challenge for orthopedic and reconstructive surgeons.
It is in this context that tissue engineering has been emerging as a valid approach to the current therapies for tissue regeneration/substitution. In contrast to classic biomaterial approach, the main goal is the understanding of tissue formation and regeneration, and aims to induce new functional tissues, rather than just to implant new spare parts, lead to engineered bone.
In this context, we are interested on the identification of the best internal structures and chemical compositions of the 3D scaffolds to be used as bone grafts/substitutes. Besides chemical composition, the other critical parameter to improve the efficiency of biomaterials to be used in bone tissue engineering is the overall structure: density, pore shape, pore size and pore interconnection pathway.
Therefore, we have tested and compared several osteoconductive porous biomaterials with different internal architecture and chemical composition, by using an established model of in vivo bone formation by exogenously added osteoprogenitor cells. In parallel, we have designed, developed and tested a prototype 3D osteoconductive graft, completely based on an “open-structure” concept, in order to favour vascularisation of the graft and in principle guarantee an unlimited neo-bone tissue ingrowth. This new concept of biomaterials should overcomes the intrinsic limits of their internal structure of the most porous materials available.
Design and development of innovative bioreactor systems for stem/progenitor cell culture in 3D environment under proper physical stimulations
From the bio-engineering point of view, the ex vivo generation of osteoinductive grafts as bone substitute must become a reproducible and automatic process, where control and automation introduced by defined bioreactor systems have to play a key role for the transfer of bone TE approach to large-scale medical applications. Inducing cells to form tissues in a reproducible manner is the fundamental problem of tissue engineering. In addition to stimuli of a biochemical nature, it has been noticed that the cell growth, and especially the spatial organization of the cells (that is essential for the structural tissues) are also affected by stimuli of a mechanical origin. Thereby, the bioreactor systems allow promoting the cell growth in the desired physiological specialization. At the same time, the bioreactor systems allow automatizing the tissue regeneration process, and switching to the use of the regenerative medicine in the routine clinical practice, thus ensuring that the techniques used in the laboratory are standardizable and easily reproducible.
In our lab, different bioreactor system have been designed and developed (i.e. perfusing systems, torsional/traction/compression bioreactor devices, parallel plate systems with fluid flow induced shear stress stimulation), for a wide regenerative medicine application field.
Innovative tissue engineering approaches for in vivo tissue regeneration
Stem cell therapy of skeletal tissues has proven to be a potentially successful strategy by providing a novel therapeutic approach that responds to pathological conditions of patients suffering large bone losses because of injuries or diseases. Among different sources of osteoprogenitor cells which have been proposed, the use of adult stem cells combined with proper 3D scaffolds would allow a wide spread applications particularly in areas of spinal cord injury, non-unions, critical bone defects, spinal fusions, augmentation of ligament reconstructions, cartilage repair and degenerative disc disorders. In this context, we are also involved in the development and validation of a therapeutic approach for in vivo Imaging and Targeting of bioactive molecules and stem cell therapy in regenerative medicine.