Márcia T. Rodrigues

Engineering tendon and ligament tissues: present developments towards successful clinical products

Musculoskeletal diseases are one of the leading causes of disability worldwide. Among them, tendon and ligament injuries represent an important aspect to consider in both athletes and active working people. Tendon and ligament damage is an important cause of joint instability, and progresses into early onset of osteoarthritis, pain, disability and eventually the need for joint replacement surgery. The social and economical burden associated with these medical conditions presents a compelling argument for greater understanding and expanding research on this issue. The particular physiology of tendons and ligaments (avascular, hypocellular and overall structural mechanical features) makes it difficult for currently available treatments to reach a complete and long‐term functional repair of the damaged tissue, especially when complete tear occurs. Despite the effort, the treatment modalities for tendon and ligament are suboptimal, which have led to the development of alternative therapies, such as the delivery of growth factors, development of engineered scaffolds or the application of stem cells, which have been approached in this review. Copyright

A new route to produce starch-based fiber mesh scaffolds by wet spinning and subsequent surface modification as a way to improve cell attachment and proliferation

This study proposes a new route for producing fiber mesh scaffolds from a starch-polycaprolactone (SPCL) blend. It was demonstrated that the scaffolds with 77% porosity could be obtained by a simple wet-spinning technique based on solution/precipitation of a polymeric blend. To enhance the cell attachment and proliferation, Ar plasma treatment was applied to the scaffolds. It was observed that the surface morphology and chemical composition were significantly changed because of the etching and functionalization of the fiber surfaces. XPS analyses showed an increase of the oxygen content of the fiber surfaces after plasma treatment (untreated scaffolds O/C:0.32 and plasma-treated scaffolds O/C:0.41). Both untreated and treated scaffolds were examined using a SaOs-2 human osteoblast-like cell line during 2 weeks of culture. The cell seeded on wet-spun SPCL fiber mesh scaffolds showed high viability and alkaline phosphatase enzyme activity, with those values being even higher for the cells seeded on the plasma-treated scaffolds.

Understanding the role of growth factors in modulating stem cell tenogenesis

Current treatments for tendon injuries often fail to fully restore joint biomechanics leading to the recurrence of symptoms, and thus resulting in a significant health problem with a relevant social impact worldwide. Cell-based approaches involving the use of stem cells might enable tailoring a successful tendon regeneration outcome. As growth factors (GFs) powerfully regulate the cell biological response, their exogenous addition can further stimulate stem cells into the tenogenic lineage, which might eventually depend on stem cells source. In the present study we investigate the tenogenic differentiation potential of human- amniotic fluid stem cells (hAFSCs) and adipose-derived stem cells (hASCs) with several GFs associated to tendon development and healing; namely, EGF, bFGF, PDGF-BB and TGF-β1. Stem cells response to biochemical stimuli was studied by screening of tendon-related genes (collagen type I, III, decorin, tenascin C and scleraxis) and proteins found in tendon extracellular matrix (ECM) (Collagen I, III, and Tenascin C). Despite the fact that GFs did not seem to influence the synthesis of tendon ECM proteins, EGF and bFGF influenced the expression of tendon-related genes in hAFSCs, while EGF and PDGF-BB stimulated the genetic expression in hASCs. Overall results on cellular alignment morphology, immunolocalization and PCR analysis indicated that both stem cell source can be biochemically induced towards tenogenic commitment, validating the potential of hASCs and hAFSCs for tendon regeneration strategies.

Bilayered constructs aimed at osteochondral strategies: the influence of medium supplements in the osteogenic and chondrogenic differentiation of amniotic fluid-derived stem cells.

The development of osteochondral tissue engineered interfaces would be a novel treatment for traumatic injuries and aging associated diseases that affect joints. This study reports the development of a bilayered scaffold, which consists of both bone and cartilage regions. On the other hand, amniotic fluid-derived stem cells (AFSCs) could be differentiated into either osteogenic or chondrogenic cells, respectively. In this study we have developed a bilayered scaffolding system, which includes a starch/polycaprolactone (SPCL) scaffold for osteogenesis and an agarose hydrogel for chondrogenesis. AFSC-seeded scaffolds were cultured for 1 or 2 weeks in an osteochondral-defined culture medium containing both osteogenic and chondrogenic differentiation factors. Additionally, the effect of the presence or absence of insulin-like growth factor-1 (IGF-1) in the culture medium was assessed. Cell viability and phenotypic expression were assessed within the constructs in order to determine the influence of the osteochondral differentiation medium. The results indicated that, after osteogenic differentiation, AFSCs that had been seeded onto SPCL scaffolds did not require osteochondral medium to maintain their phenotype, and they produced a protein-rich, mineralized extracellular matrix (ECM) for up to 2 weeks. However, AFSCs differentiated into chondrocyte-like cells appeared to require osteochondral medium, but not IGF-1, to synthesize ECM proteins and maintain the chondrogenic phenotype. Thus, although IGF-1 was not essential for creating osteochondral constructs with AFSCs in this study, the osteochondral supplements used appear to be important to generate cartilage in long-term tissue engineering approaches for osteochondral interfaces. In addition, constructs generated from agarose-SPCL bilayered scaffolds containing pre-differentiated AFSCs may be useful for potential applications in regeneration strategies for damaged or diseased joints.

Current strategies for osteochondral regeneration: from stem cells to pre-clinical approaches.

Damaged cartilage tissue has no functional replacement alternatives and current therapies for bone injury treatment are far from being the ideal solutions emphasizing an urgent need for alternative therapeutic approaches for osteochondral (OC) regeneration. The tissue engineering field provides new possibilities for therapeutics and regeneration in rheumatology and orthopaedics, holding the potential for improving the quality of life of millions of patients by exploring new strategies towards the development of biological substitutes to maintain, repair and improve OC tissue function. Numerous studies have focused on the development of distinct tissue engineering strategies that could result in promising solutions for this delicate interface. In order to outperform currently used methods, novel tissue engineering approaches propose, for example, the design of multi-layered scaffolds, the use of stem cells, bioreactors or the combination of clinical techniques.

Tissue-engineered constructs based on SPCL scaffolds cultured with goat marrow cells: functionality in femoral defects

This study aims to assess the in vivo performance of cell–scaffold constructs composed of goat marrow stromal cells (GBMCs) and SPCL (a blend of starch with polycaprolactone) fibre mesh scaffolds at different stages of development, using an autologous model. GBMCs from iliac crests were seeded onto SPCL scaffolds and in vitro cultured for 1 and 7 days in osteogenic medium. After 1 and 7 days, the constructs were characterized for proliferation and initial osteoblastic expression by alkaline phosphatase (ALP) activity. Scanning electron microscopy analysis was performed to investigate cellular morphology and adhesion to SPCL scaffolds. Non‐critical defects (diameter 6 mm, depth 3 mm) were drilled in the posterior femurs of four adult goats from which bone marrow and serum had been collected previously. Drill defects alone and defects filled with scaffolds without cells were used as controls. After implantation, intravital fluorescence markers, xylenol orange, calcein green and tetracycline, were injected subcutaneously after 2, 4 and 6 weeks, respectively, for bone formation and mineralization monitoring. Subsequently, samples were stained with Lévai–Laczkó for bone formation and histomorphometric analysis. GBMCs adhered and proliferated on SPCL scaffolds and an initial differentiation into pre‐osteoblasts was detected by an increasing level of ALP activity with the culture time. In vivo experiments indicated that bone neoformation occurred in all femoral defects. The results obtained provided important information about the performance of SPCL–GBMC constructs in an orthotopic goat model that enabled future studies to be designed to investigate in vivo the functionality of SPCL–GBMC constructs in more complex models, viz. critical sized defects, and to evaluate the influence of in vitro cultured autologous cells in the healing and bone regenerative process. Copyright

In situ functionalization of wet-spun fibre meshes for bone tissue engineering.

Bone tissue engineering success strongly depends on our ability to develop new materials combining osteoconductive, osteoinductive and osteogenic properties. Recent studies suggest that biomaterials incorporating silanol (SiOH) groups promote and maintain osteogenesis. The purpose of the present research work was to provide evidence that using wet‐spinning technologies and a calcium silicate solution as a coagulation bath, it was possible to develop an in situ functionalization methodology to obtain 3D wet‐spun fibre meshes with SiOH groups, through a simple, economic and reliable process. SPCL (blend of starch with polycaprolactone) fibre meshes were produced by wet‐spinning, using a calcium silicate solution as a non‐solvent and functionalized in situ with SiOH groups. In vitro tests, using goat bone marrow stromal cells (GBMSCs), showed that SPCL–Si scaffolds sustained cell viability and proliferation. Furthermore, high ALP activity and matrix production indicated that SiOH groups improve cellular functionality towards the osteoblastic phenotype. Using this methodology, and assembling several wet‐spun fibre meshes, 3D meshes can be developed, aiming at designing osteoconductive/osteoinductive 3D structures capable of stimulating bone ingrowth in vivo. Copyright

Amniotic Fluid-Derived Stem Cells as a Cell Source for Bone Tissue Engineering

In tissue engineering, stem cells have become an ideal cell source that can differentiate into most human cell types. Among the stem cells, bone marrow-derived stem cells (BMSCs) have been widely studied, and there is strong evidence that these cells can be differentiated into cells of the osteogenic lineage. Thus, BMSCs have become the gold standard for studies of tissue engineering in orthopedics. However, novel stem cell sources, such as amniotic fluid-derived stem cells (AFSCs) have been identified, and these have important and unique features that may lead to novel and successful applications toward the regeneration of bone tissue. This study was designed to originally compare the osteogenic potential of both BMSCs and AFSCs under distinct culture environments to determine whether the osteogenic differentiation process of both types of stem cells is related to the origin of the cells. Osteogenic differentiation was carried out in both two and three dimensions using a tissue culture plate and by means of seeding the cells onto microfibrous starch and poly(ɛ-caprolactone) scaffolds (a blend of starch and polycaprolactone), respectively. BMSCs and AFSCs were successfully differentiated into the osteogenic cell type, as cells derived from them produced a mineralized extracellular matrix. Nevertheless, the two types of cells presented different expression patterns of bone-related markers as well as different timing of differentiation, indicating that both cell origin and the culture environment have a significant impact on the differentiation into the osteogenic phenotype in AFSCs and BMSCs.

Contributions and future perspectives on the use of magnetic nanoparticles as diagnostic and therapeutic tools in the field of regenerative medicine

The current limitations of regenerative medicine strategies may be overcome through the use of magnetic nanoparticles (MNPs), a class of nanomaterial typically composed of magnetic elements that can be manipulated under the influence of an external magnetic field. Cell engineering approaches following the internalization of these MNPs by cells and/or the incorporation of these nanosystems within 3D constructs (scaffolds or hydrogels) may constitute a new attractive approach to achieve a magnetically responsive system enabling remote control over tissue-engineered constructs in an in vivo scenario. Moreover, the incorporation of bioactive factors within these MNPs also enables a targeted and smart delivery of biomolecules to specific regions and/or triggering specific cell responses upon external magnetic stimulation. Certainly, one of the most attractive properties of MNPs is their ability to be used as theranostic tools for regenerative medicine applications, enabling live monitoring and tracking of the system while simultaneously acting as a therapeutic stimulation.

Cryopreservation of cell laden natural origin hydrogels for cartilage regeneration strategies

The time span needed for obtaining a functional cartilage substitute using tissue engineering strategies, together with the need for specific patient oriented constructs has stimulated the growing interest for developing “off-the shelf” products. One way to deliver such products is based on long-term storage processes, such as cryopreservation, that will provide the clinical substitute available as needed and could be adapted to an autologous immediate solution for the patient. The aim of this study was to examine the effects of cryopreservation on the chondrogenic differentiation characteristics of human mesenchymal derived stem cells isolated from adipose tissue and encapsulated in κ-carrageenan hydrogels. These bioengineered constructs are anticipated to participate in a cartilage regeneration strategy providing temporary habitation for cell survival, proliferation and production of an extracellular matrix which is expected to replace the hydrogel, enhancing the regeneration of native tissues in clinical settings. The results obtained show that the hydrogels withstand the cryopreservation with dimethyl sulfoxide, maintaining their structural integrity, while assisting cells proliferation and chondrogenic potential after cryopreservation. Thus, cell encapsulation systems of natural based hydrogels seem to be an interesting approach for the preservation of cartilage tissue engineered products.