Micro/nano materials regulate cell morphology and intercellular communication by extracellular vesicles

The proteins derived from platelet-rich plasma improve the endothelialization and vascularization of small diameter vascular grafts

Vascular transplantation has become an ideal substitute for heart and peripheral vascular bypass therapy and tissue-engineered vascular grafts (TEVGs) present an attractive potential solution for vascular surgery. However, small diameter (Ф < 6 mm) vascular do not have ideal TEVGs for clinical use. Platelet-rich plasma (PRP), a key source of bioactive molecules, has been confirmed to promote tissue repair and regeneration. In this study, we prepared PRP-loaded TEVGs (PRP-TEVGs) by electrospinning, investigated the characterization of TEVGs, and verified the effect of PRP-TEVGs in vivo and in vitro experiments. The results suggested that PRP-TEVGs had good biocompatibility, released growth factors stably, promoted cell proliferation and migration significantly, up-regulated the expression of endothelial NO synthase (eNOS) in functional vascular endothelial cells (VECs), and maintained the stability of the endothelial structure. In vivo experiments suggest that PRP can promote rapid endothelialization and reconstruction of TEVGs. Overall, this finding indicated that PRP could promote the rapid vascular endothelialization of small-diameter TEVGs by improving contractile vascular smooth muscle cells (VSMCs) regeneration, and maintaining the integrity and functionality of VECs.

Small extracellular vesicles with nanomorphology memory promote osteogenesis

Nanotopographical cues endow biomaterials the ability to guide cell adhesion, proliferation, and differentiation. Cellular mechanical memory can maintain the cell status by retaining cellular information obtained from past mechanical microenvironments. Here, we propose a new concept “morphology memory of small extracellular vesicles (sEV)” for bone regeneration. We performed nanotopography on titanium plates through alkali and heat (Ti8) treatment to promote human mesenchymal stem cell (hMSC) differentiation. Next, we extracted the sEVs from the hMSC, which were cultured on the nanotopographical Ti plates for 21 days (Ti8-21-sEV). We demonstrated that Ti8-21-sEV had superior pro-osteogenesis ability in vitro and in vivo. RNA sequencing further confirmed that Ti8-21-sEV promote bone regeneration through osteogenic-related pathways, including the PI3K-AKT signaling pathway, MAPK signaling pathway, focal adhesion, and extracellular matrix-receptor interaction. Finally, we decorated the Ti8-21-sEV on a 3D printed porous polyetheretherketone scaffold. The femoral condyle defect model of rabbits was used to demonstrate that Ti8-21-sEV had the best bone ingrowth. In summary, our study demonstrated that the Ti8-21-sEV have memory function by copying the pro-osteogenesis information from the nanotopography. We expect that our study will encourage the discovery of other sEV with morphology memory for tissue regeneration.

•

Nanotopography fabricated on titanium plates has superior promoted hMSCs differentiation ability.

•

sEV extracted from hMSCs which were cultured on Ti8 plates for 21 days had the superior pro-osteogenesis ability.

•

Ti8-21-sEV have memory function through copy the pro-osteogenesis information from nanotopography.

•

RNA sequencing confirmed that Ti8-21-sEV promote bone regeneration through osteogenic-related pathways.

Extracellular vesicles in vascular remodeling

Vascular remodeling contributes to the development of a variety of vascular diseases including hypertension and atherosclerosis. Phenotypic transformation of vascular cells, oxidative stress, inflammation and vascular calcification are closely associated with vascular remodeling. Extracellular vesicles (EVs) are naturally released from almost all types of cells and can be detected in nearly all body fluids including blood and urine. EVs affect vascular oxidative stress, inflammation, calcification, and lipid plaque formation; and thereby impact vascular remodeling in a variety of cardiovascular diseases. EVs may be used as biomarkers for diagnosis and prognosis, and therapeutic strategies for vascular remodeling and cardiovascular diseases. This review includes a comprehensive analysis of the roles of EVs in the vascular remodeling in vascular diseases, and the prospects of EVs in the diagnosis and treatment of vascular diseases.

Regulation of T Cell Responses by Nano-Hydroxyapatite to Mediate the Osteogenesis

Nano-hydroxyapatite (nHA) has been widely applied as a tissue-engineering biomaterial and interacted with osteoblasts/stem cells to repair bone defects. In addition, T cells that coexist with osteoblasts/stem cells in the bone modulate the regulation of osteoimmunology by cytokine formation. However, the effects of nHA on T cells and the following regulatory interplay on osteogenic differentiation have been rarely examined. In this work, the physicochemical properties of needle-like nHA are characterized by field emission scanning electron microscopy, zeta potential, Fourier transform-infrared and X-ray diffraction. It is found that as the concentration of nHA increases, the proliferation of T cells gradually increases, and the proportion of apoptotic T cells decreases. The percentage of CD4⁺ T cells is higher than that of CD8⁺ T cells under the regulation of needle-like nHA. Furthermore, the supernatant of T cells co-cultured with nHA significantly inhibits the osteogenic differentiation of MC3T3-E1 by downregulating the formation of alkaline phosphatase and calcium nodule compared with the supernatant of nHA. Thus, our findings provide new insight into the nHA-mediated T cell and osteoblast interactions.

Vascularization in tissue engineering: The architecture cues of pores in scaffolds

Vascularization is a key event and also still a challenge in tissue engineering. Many efforts have been devoted to the development of vascularization based on cells, growth factors, and porous scaffolds in the past decades. Among these efforts, the architecture features of pores in scaffolds played important roles for vascularization, which have attracted increasing attention. It has been known that the open macro pores in scaffolds could facilitate cell migration, nutrient, and oxygen diffusion, which then could promote new tissue formation and vascularization. The pore parameters are the important factors affecting cells response and vessel formation. Thus, this review will give an overview of the current advances in the effects of pore parameters on vascularization in tissue engineering, mainly including pore size, interconnectivity, pore size distribution, pore shape (channel structure), and the micro/nano-surface topography of pores.

Development of hierarchical porous bioceramic scaffolds with controlled micro/nano surface topography for accelerating bone regeneration

Mimicking hierarchical porous architecture of bone has been considered as a valid approach to promote bone regeneration. In this study, hierarchical porous β-tricalcium phosphate (β-TCP) scaffolds were constructed by combining digital light processing (DLP) printing technique and in situ growth crystal process. Macro/micro hierarchical scaffolds with designed macro pores for facilitating the ingrowth of bone tissue were fabricated by DLP printing. Three types of micro/nano surface topography were obtained by in situ growth crystal process to regulate stem cells behavior. The attachment and proliferation of rat bone marrow mesenchymal stem cells (rBMSCs) were strongly dependent on the surface roughness and the specific surface area. The micro/nano surface topography distinctly facilitated the differentiation of rBMSCs by targeting MAPK, STAT and AKT signaling pathways, in which the sodium hydroxide treatment group showed the highest promoting effect. Furthermore, in vivo results of skull defect repair model of rats indicated that hierarchical scaffolds with micro/nano topographies exhibited appealing bone regeneration capacity. The hierarchical porous bioceramic scaffolds constructed by integrating structural design and physical stimulation of the external surface topography have great potential for rapid bone repair via modulation of microenvironmental regulatory pathways at the bone defect site.