The Janus Role of Adhesion in Chondrogenesis

Mechanomorphological Guidance of Colloidal Gel Regulates Cell Morphogenesis

Microstructural morphology of the extracellular matrix guides the organization of cells in 3D. However, current biomaterials-based matrices cannot provide distinct spatial cues through their microstructural morphology due to design constraints. To address this, colloidal gels are developed as 3D matrices with distinct microstructure by aggregating ionic polyurethane colloids via electrostatic screening. Due to the defined orientation of interconnected particles, positively charged colloids form extended strands resulting in a dense microstructure whereas negatively charged colloids form compact aggregates with localized large voids. Chondrogenesis of human mesenchymal stem cells (MSCs) and endothelial morphogenesis of human endothelial cells (ECs) are examined in these colloidal gels. MSCs show enhanced chondrogenic response in dense colloidal gel due to their spatial organization achieved by balancing the cell-cell and cell-matrix interactions compared to porous gels where cells are mainly clustered. ECs tend to form relatively elongated cellular networks in dense colloidal gel compared to porous gels. Additionally, the role of matrix stiffness and viscoelasticity in the morphogenesis of MSCs and ECs are analyzed with respect to microstructural morphology. Overall, these results demonstrate that colloidal gels can provide spatial cues through their microstructural morphology and in correlation with matrix mechanics for cell morphogenesis.

Recent advances in engineering nanotopographic substrates for cell studies

Cells sense their environment through the cell membrane receptors. Interaction with extracellular ligands induces receptor clustering at the nanoscale, assembly of the signaling complexes in the cytosol and activation of downstream signaling pathways, regulating cell response. Nanoclusters of receptors can be further organized hierarchically in the cell membrane at the meso- and micro-levels to exert different biological functions. To study and guide cell response, cell culture substrates have been engineered with features that can interact with the cells at different scales, eliciting controlled cell responses. In particular, nanoscale features of 1–100 nm in size allow direct interaction between the material and single cell receptors and their nanoclusters. Since the first “contact guidance” experiments on parallel microstructures, many other studies followed with increasing feature resolution and biological complexity. Here we present an overview of the advances in the field summarizing the biological scenario, substrate fabrication techniques and applications, highlighting the most recent developments.

Nanoscale ligand density modulates gap junction intercellular communication of cell condensates during chondrogenesis

Aim: To unveil the influence of cell-matrix adhesions in the establishment of gap junction intercellular communication (GJIC) during cell condensation in chondrogenesis. Materials & methods: Previously developed nanopatterns of the cell adhesive ligand arginine-glycine-aspartic acid were used as cell culture substrates to control cell adhesion at the nanoscale. In vitro chondrogenesis of mesenchymal stem cells was conducted on the nanopatterns. Cohesion and GJIC were evaluated in cell condensates. Results: Mechanical stability and GJIC are enhanced by a nanopattern configuration in which 90% of the surface area presents adhesion sites separated less than 70 nm, thus providing an onset for cell signaling. Conclusion: Cell-matrix adhesions regulate GJIC of mesenchymal cell condensates during in vitro chondrogenesis from a threshold configuration at the nanoscale.

Mesenchymal Stem Cells Isolated from Paediatric Paravertebral Adipose Tissue Show Strong Osteogenic Potential

Mesenchymal stem cells (MSCs) represent the basis of novel clinical concepts in cellular therapy and tissue regeneration. Therefore, the isolation of MSCs from various tissues has become an important endeavour for stem cell biobanking and the development of regenerative therapies. Paravertebral adipose tissue is readily exposed during spinal procedures in children and could be a viable source of stem cells for therapeutic applications. Here, we describe the first case of MSCs isolated from paravertebral adipose tissue (PV-ADMSCs), obtained during a routine spinal surgery on a child. Using quantitative real-time PCR and flow cytometry, we show that PV-ADMSCs have different levels of stem marker expression compared to the MSCs from other sources while having the highest proliferation rate. Furthermore, we evaluate the multipotency of PV-ADMSCs by the three-lineage (adipogenic, osteogenic and chondrogenic) differentiation and compare it to the multipotency of MSCs from other sources. It was found that the PV-ADMSCs have a strong osteogenic potential in particular. Taken together, our data indicate that PV-ADMSCs meet the criteria for successful cell therapy, defined by the International Society for Cellular Therapy (ISCT), and thus, could provide a source of MSCs that is relatively easy to isolate and expand in culture. Due to their strong osteogenic potential, these cells provide a promising basis, especially for orthopaedic applications.

Non-mulberry silk fiber-based scaffolds reinforced by PLLA porous microspheres for auricular cartilage: An in vitro study

Designing clinical applicable polymeric composite scaffolds for auricular cartilage tissue engineering requires appropriate mechanical strength and biological characteristics. In this study, silk fiber-based scaffolds co-reinforced with poly-L-lactic acid porous microspheres (PLLA PMs) combined with either Bombyx mori (Bm) or Antheraea pernyi (Ap) silk fibers were fabricated as inspired by the "steel bars reinforced concrete" structure in architecture and their chondrogenic functions were also investigated. We found that the Ap silk fiber-based scaffolds reinforced by PLLA PMs (MAF) exhibited superior physical properties (the mechanical properties in particular) as compared to the Bm silk fiber-based scaffolds reinforced by PLLA PMs (MBF). Furthermore, in vitro evaluation of chondrogenic potential showed that the MAF provided better cell adhesion, viability, proliferation and GAG secretion than the MBF. Therefore, the MAF are promising in auricular cartilage tissue engineering and relevant plastic surgery-related applications.

Dual Function Molecules and Processes in Cell Fate Decision: A Preface to the Special Issue

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