Shiyu Lin

Nanomaterials and bone regeneration

The worldwide incidence of bone disorders and conditions has been increasing. Bone is a nanomaterials composed of organic (mainly collagen) and inorganic (mainly nano-hydroxyapatite) components, with a hierarchical structure ranging from nanoscale to macroscale. In consideration of the serious limitation in traditional therapies, nanomaterials provide some new strategy in bone regeneration. Nanostructured scaffolds provide a closer structural support approximation to native bone architecture for the cells and regulate cell proliferation, differentiation, and migration, which results in the formation of functional tissues. In this article, we focused on reviewing the classification and design of nanostructured materials and nanocarrier materials for bone regeneration, their cell interaction properties, and their application in bone tissue engineering and regeneration. Furthermore, some new challenges about the future research on the application of nanomaterials for bone regeneration are described in the conclusion and perspectives part.

Crosstalk between adipose-derived stem cells and chondrocytes: when growth factors matter

Adipose-derived stem cells (ASCs) and mesenchymal stem cells are promising for tissue repair because of their multilineage differentiation capacity. Our previous data confirmed that the implantation of mixed ASCs and chondrocytes into cartilage defects induced desirable in vivo healing outcomes. However, the paracrine action of ASCs on chondrocytes needs to be further elucidated. In this study, we established a co-culture system to achieve cell-to-cell and cell-to-tissue crosstalk and explored the soluble growth factors in both ASCs and chondrocytes supplemented with 1% fetal bovine serum to mimic the physiological microenvironment. In ASCs, we screened for growth factors by semi-quantitative PCR and quantitative real-time PCR and found that the expression of bone morphogenetic protein 2 (BMP-2), vascular endothelial growth factor B (VEGFB), hypoxia inducible factor-1α (HIF-1α), fibroblast growth factor-2 (FGF-2), and transforming growth factor-β1 significantly increased after co-culture in comparison with mono-culture. In chondrocytes, VEGFA was significantly enhanced after co-culture. Unexpectedly, the expression of collagen II and aggrecan was significantly down-regulated in the co-culture group compared with the mono-culture group. Meanwhile, among all the growth factors screened, we found that the BMP family members BMP-2, BMP-4, and BMP-5 were down-regulated and that VEGFB, HIF-1α, FGF-2, and PDGF were significantly decreased after co-culture. These results suggest that crosstalk between ASCs and chondrocytes is a pathway through the regulated growth factors that might have potential in cartilage repair and regeneration and could be useful for tissue engineering.

Effects of low oxygen tension on gene profile of soluble growth factors in co-cultured adipose-derived stromal cells and chondrocytes

Moving towards development of optimized cartilage regeneration with adipose‐derived stromal cells (ASCs), the focus of this study was on investigating the influence of hypoxia on soluble factors secreted by ASCs and chondrocytes after crosstalk.

Softening Substrates Promote Chondrocytes Phenotype via RhoA/ROCK Pathway

Due to its evascular, aneural, and alymphatic conditions, articular cartilage shows extremely poor regenerative ability. Thus, directing chondrocyte toward a desired location and function by utilizing the mechanical cues of biomaterials is a promising approach for effective tissue regeneration. However, chondrocytes cultured on Petri dish will lose their typical phenotype which may lead to compromised results. Therefore, we fabricated polydimethylsiloxane (PDMS) materials with various stiffness as culture substrates. Cell morphology and focal adhesion of chondrocytes displayed significant changes. The cytoskeletal tension of the adherent cells observed by average myosin IIA fluorescent intensity increased as stiffness of the underlying substrates decreased, consistent with the alteration of chondrocyte phenotype in our study. Immunofluorescent images and q-PCR results revealed that chondrocyte cultured on soft substrates showed better chondrocyte functionalization by more type II collagen and aggrecan expression, related to the lowest mRNA level of Rac-1, RhoA, ROCK-1, and ROCK-2. Taken together, this work not only points out that matrix elasticity can regulate chondrocyte functionalization via RhoA/ROCK pathway, but also provides new prospect for biomechanical control of cell behavior in cell-based cartilage regeneration.

Tetrahedral DNA Nanostructure: A Potential Promoter for Cartilage Tissue Regeneration via Regulating Chondrocyte Phenotype and Proliferation.

Utilizing biomaterials to regulate the phenotype and proliferation of chondrocytes is a promising approach for effective cartilage tissue regeneration. Recently, a significant amount of effort has been invested into directing chondrocytes toward a desired location and function by utilizing biomaterials to control the dedifferentiation and phenotypic loss of chondrocytes during in vitro monolayer culture. Here, the transmission signals resulting from tetrahedral DNA nanostructures (TDNs) in the regulation of chondrocyte phenotype and proliferation are exploited. TDNs, new DNA nanomaterials, have been considered as promising materials in biomedical fields. Upon exposure to TDNs, chondrocyte phenotype is significantly enhanced, accompanied by lower gene expression related to Notch signaling pathway and higher expression of type II collagen. In addition, the cell proliferation and morphology of chondrocytes are changed after exposure to TDNs. In conclusion, this work demonstrates that TDNs are potentially useful mechanism in cartilage tissue regeneration from chondrocytes, whereby chondrocyte phenotype and proliferation can be retained.

Self-Assembled Tetrahedral DNA Nanostructures Promote Adipose-Derived Stem Cell Migration via lncRNA XLOC 010623 and RHOA/ROCK2 Signal Pathway

Self-assembled tetrahedral DNA nanostructures (TDNs) with precise sizes have been extensively applied in various fields owing to their exceptional mechanical rigidity, structural stability, and modification versatility. In addition, TDNs can be internalized by mammalian cells and remain mainly intact within the cytoplasm by escaping degradation by nucleases. Here, we studied the effects of TDNs on cell migration and the underlying molecular mechanisms. TDNs remarkably enhanced the migration of rat adipose-derived stem cells and down-regulated the long noncoding RNA (lncRNA) XLOC 010623 to activate the mRNA expression of Tiam1 and Rac1. Furthermore, TDNs highly up-regulated the mRNA and protein expression of RHOA, ROCK2, and VCL. These results indicate that TDNs suppressed the transcription of lncRNA XLOC 010623 and activated the TIAM1/RAC1 and RHOA/ROCK2 signaling pathways to promote cell migration. On the basis of these findings, TDNs show a high potential for application in tissue repair and regenerative medicine as a functional three-dimensional DNA nanomaterial.

PCL-PEG-PCL film promotes cartilage regeneration in vivo.

Management of chondral defects has long been a challenge due to poor self‐healing capacity of articular cartilage. Many approaches, ranging from symptomatic treatment to structural cartilage regeneration, have obtained very limited satisfactory results. Cartilage tissue engineering, which involves optimized combination of novel scaffolds, cell sources and growth factors, has emerged as a promising strategy for cartilage regeneration and repair. In this study, the aim was to investigate the role of poly(ε‐caprolactone)‐poly(ethylene glycol)‐poly(ε‐caprolactone) (PCL‐PEG‐PCL, PCEC) PCEC scaffold in cartilage repair.

The JAK/STAT3 signalling pathway regulated angiogenesis in an endothelial cell/adipose-derived stromal cell co-culture, 3D gel model

The aim of the study was to investigate the role of the JAK/STAT3 signalling pathway in angiogenesis.

Gene profile of soluble growth factors involved in angiogenesis, in an adipose‐derived stromal cell/endothelial cell co‐culture, 3D gel model

The aim of this study was to investigate gene expressions of growth factors for angiogenesis, in a three‐dimensional (3D) gel populated with adipose‐derived stromal cells (ASCs) and endothelial cells (ECs) in co‐culture.

Angiogenesis in a 3D model containing adipose tissue stem cells and endothelial cells is mediated by canonical Wnt signaling

Adipose-derived stromal cells (ASCs) have gained great attention in regenerative medicine. Progress in our understanding of adult neovascularization further suggests the potential of ASCs in promoting vascular regeneration, although the specific cues that stimulate their angiogenic behavior remain controversial. In this study, we established a three-dimensional (3D) angiogenesis model by co-culturing ASCs and endothelial cells (ECs) in collagen gel and found that ASC-EC-instructed angiogenesis was regulated by the canonical Wnt pathway. Furthermore, the angiogenesis that occurred in implants collected after injections of our collagen gel-based 3D angiogenesis model into nude mice was confirmed to be functional and also regulated by the canonical Wnt pathway. Wnt regulation of angiogenesis involving changes in vessel length, vessel density, vessel sprout, and connection numbers occurred in our system. Wnt signaling was then shown to regulate ASC-mediated paracrine signaling during angiogenesis through the nuclear translocation of β-catenin after its cytoplasmic accumulation in both ASCs and ECs. This translocation enhanced the expression of nuclear co-factor Lef-1 and cyclin D1 and activated the angiogenic transcription of vascular endothelial growth factor A (VEGFA), basic fibroblast growth factor (bFGF), and insulin-like growth factor 1 (IGF-1). The angiogenesis process in the 3D collagen model appeared to follow canonical Wnt signaling, and this model can help us understand the importance of the canonical Wnt pathway in the use of ASCs in vascular regeneration.