Cyclic tensile strain promotes chondrogenesis of bone marrow-derived mesenchymal stem cells by increasing miR-365 expression

mPPTMP195 nanoparticles enhance fracture recovery through HDAC4 nuclear translocation inhibition

Delayed repair of fractures seriously impacts patients' health and significantly increases financial burdens. Consequently, there is a growing clinical demand for effective fracture treatment. While current materials used for fracture repair have partially addressed bone integrity issues, they still possess limitations. These challenges include issues associated with autologous material donor sites, intricate preparation procedures for artificial biomaterials, suboptimal biocompatibility, and extended degradation cycles, all of which are detrimental to bone regeneration. Hence, there is an urgent need to design a novel material with a straightforward preparation method that can substantially enhance bone regeneration. In this context, we developed a novel nanoparticle, mPPTMP195, to enhance the bioavailability of TMP195 for fracture treatment. Our results demonstrate that mPPTMP195 effectively promotes the differentiation of bone marrow mesenchymal stem cells into osteoblasts while inhibiting the differentiation of bone marrow mononuclear macrophages into osteoclasts. Moreover, in a mouse femur fracture model, mPPTMP195 nanoparticles exhibited superior therapeutic effects compared to free TMP195. Ultimately, our study highlights that mPPTMP195 accelerates fracture repair by preventing HDAC4 translocation from the cytoplasm to the nucleus, thereby activating the NRF2/HO-1 signaling pathway. In conclusion, our study not only proposes a new strategy for fracture treatment but also provides an efficient nano-delivery system for the widespread application of TMP195 in various other diseases.

Impact of interstitial flow on cartilage matrix synthesis and NF-kB transcription factor mRNA expression in a novel perfusion bioreactor

This work is focused on designing an easy-to-use novel perfusion system for articular cartilage (AC) tissue engineering and using it to elucidate the mechanism by which interstitial shear upregulates matrix synthesis by articular chondrocytes (AChs). Porous chitosan-agarose (CHAG) scaffolds were synthesized and compared to bulk agarose (AG) scaffolds. Both scaffolds were seeded with osteoarthritic human AChs and cultured in a novel perfusion system with a medium flow velocity of 0.33 mm/s corresponding to 0.4 mPa surfice shear and 40 mPa CHAG interstitial shear. While there were no statistical differences in cell viability for perfusion versus static cultures for either scaffold type, CHAG scaffolds exhibited a 3.3-fold higher (p < 0.005) cell viability compared to AG scaffold cultures. Effects of combined superficial and interstitial perfusion for CHAG showed 150- and 45-fold (p < 0.0001) increases in total collagen (COL) and 13- and 2.2-fold (p < 0.001) increases in glycosaminoglycans (GAGs) over AG non-perfusion and perfusion cultures, respectively, and a 1.5-fold and 3.6-fold (p < 0.005) increase over non-perfusion CHAG cultures. Contrasting CHAG perfusion and static cultures, chondrogenic gene comparisons showed a 3.5-fold increase in collagen type II/type I (COL2A1/COL1A1) mRNA ratio (p < 0.05), and a 1.3-fold increase in aggrecan mRNA. Observed effects are linked to NF-κB signal transduction pathway inhibition as confirmed by a 3.2-fold (p < 0.05) reduction of NF-κB mRNA expression upon exposure to perfusion. Our results demonstrate that pores play a critical role in improving cell viability and that interstitial flow caused by medium perfusion through the porous scaffolds enhances the expression of chondrogenic genes and extracellular matrix through downregulating NF-κB1.

Co-Culture of Bone Marrow Mesenchymal Stem Cells Regulates the Fibrotic Response of Endometrial Stromal Cells

This study explored the protective effects and mechanisms of bone marrow mesenchymal stem cells (BMSCs) on the fibrotic response of endometrial stromal cells. The endometrial cells were isolated from intrauterine adhesions (IUA) patients and assigned into control group, TGF-β1 group, BMSC group which was co-cultured with BMSCs in presence of TGF-β1; Exo group (treated with BMSCs-originated exosomes); Exo-inhibitor group (treated with exosome-specific inhibitors) followed by analysis of α-SMA and Vimentin level, cell viability and expression of TGFBR2, TGFβ-1, Fibronectin (FN), α-SMA, Collagen 1α1 (Col1a1), Smad2/3 and p-Smad2/3. After TGF-β1 treatment, cells exhibited higher expression of p-Smad2/3, TGFBR2, FN, TGF-SMA and COL1A1 along with reduced cell proliferation. However, BMSCs-originated exosomes or co-culture with BMSCs reversed these changes which could be inverted by exosome-specific inhibitors. In conclusion, BMSCs-originated exosomes and BMSCs exerted an anti-fibrosis effect, which was possibly through regulation of TGFβ1/Smad2/Smad3 signalling pathway in endometrial stromal cells.

Cyclic tensile strain facilitates proliferation and migration of human aortic smooth muscle cells and reduces their apoptosis via miRNA-187-3p

The cardiovascular is a system that contains extremely complex mechanical factors, in which the circulatory flow of blood has rich mechanical laws. Many studies have revealed that mechanical factors play a very important role in the process of revascularization. Hence, it is essential to investigate the mechanical factors in the process of revascularization in depth. A cyclic tensile strain (CTS) was applied to human aortic smooth muscle cells (HASMCs) at a frequency of 1 Hz and amplitudes of 5%, 10% and 15%, respectively. SmallRNA-seq was used to identify differentially expressed miRNAs (DE-miRNAs) responding to CTS in HASMCs. Starbase database predicted the target genes of DE-miRNAs. Metascape was applied for GO and KEGG pathway enrichment analysis and protein–protein interaction network construction. The proliferation and migration of CTS-treated HASMCs were significantly enhanced, and apoptosis were significantly reduced compared to the control group. SmallRNA-seq results demonstrated that 55, 16 and 16 DE-miRNAs were present in 5%, 10% and 15% CTS-treated HASMCs, respectively. Compared to controls, with miR-26a-2-3p and miR-187-3p being the intersection of these DE-miRNAs. Starbase database identified 189 common target genes for miR-26a-2-3p and miR-187-3p. Common target genes are mainly enriched in the basolateral plasma membrane and endocytosis. Further, in vitro experiments exhibited that CTS upregulated miR-187-3p expression, and miR-187-3p enhanced the proliferation and migration of HASMCs and reduced their apoptosis. It is suggested that miR-187-3p may be an important target for CTS participate in the process of cardiovascular disease.

Integrins in the Regulation of Mesenchymal Stem Cell Differentiation by Mechanical Signals

Mesenchymal stem cells (MSCs) can sense and convert mechanical stimuli signals into a chemical response. Integrins are involved in the mechanotransduction from inside to outside and from outside to inside, and ultimately affect the fate of MSCs responding to different mechanical signals. Different integrins participate in different signaling pathways to regulate MSCs multi-differentiation. In this review, we summarize the latest advances in the effects of mechanical signals on the differentiation of MSCs, the importance of integrins in mechanotransduction, the relationship between integrin heterodimers and different mechanical signals, and the interaction among mechanical signals. We put forward our views on the prospect and challenges of developing mechanical biology in tissue engineering and regenerative medicine.

Uniaxial Cyclic Stretching Promotes Chromatin Accessibility of Gene Loci Associated With Mesenchymal Stem Cells Morphogenesis and Osteogenesis

It has been previously demonstrated that uniaxial cyclic stretching (UCS) induces differentiation of mesenchymal stem cells (MSCs) into osteoblasts in vitro. It is also known that interactions between cells and external forces occur at various aspects including cell–matrix, cytoskeleton, nucleus membrane, and chromatin. However, changes in chromatin landscape during this process are still not clear. The present study was aimed to determine changes of chromatin accessibility under cyclic stretch. The influence of cyclic stretching on the morphology, proliferation, and differentiation of hMSCs was characterized. Changes of open chromatin sites were determined by assay for transposase accessible chromatin with high-throughput sequencing (ATAC-seq). Our results showed that UCS induced cell reorientation and actin stress fibers realignment, and in turn caused nuclear reorientation and deformation. Compared with unstrained group, the expression of osteogenic and chondrogenic marker genes were the highest in group of 1 Hz + 8% strain; this condition also led to lower cell proliferation rate. Furthermore, there were 2022 gene loci with upregulated chromatin accessibility in 1 Hz + 8% groups based on the analysis of chromatin accessibility. These genes are associated with regulation of cell morphogenesis, cell–substrate adhesion, and ossification. Signaling pathways involved in osteogenic differentiation were found in up-regulated GO biological processes. These findings demonstrated that UCS increased the openness of gene loci associated with regulation of cell morphogenesis and osteogenesis as well as the corresponding transcription activities. Moreover, the findings also connect the changes in chromatin accessibility with cell reorientation, nuclear reorientation, and deformation. Our study may provide reference for directed differentiation of stem cells induced by mechanical microenvironments.

Enhanced matrix production by cocultivated human stem cells and chondrocytes under concurrent mechanical strain

Conventional treatments of osteoarthritis have failed to re-build functional articular cartilage. Tissue engineering clinical treatments for osteoarthritis, including autologous chondrocyte implantation, provides an alternative approach by injecting a cell suspension to fill lesions within the cartilage in osteoarthritic knees. The success of chondrocyte implantation relies on the availability of chondrogenic cell lines, and their resilience to high mechanical loading. We hypothesize we can reduce the numbers of human articular chondrocytes necessary for a treatment by supplementing cultures with human adipose-derived stem cells, in which stem cells will have protective and stimulatory effects on mixed cultures when exposed to high mechanical loads, and in which coculture will enhance production of requisite extracellular matrix proteins over those produced by stretched chondrocytes alone. In this work, adipose-derived stem cells and articular chondrocytes were cultured separately or cocultivated at ratios of 3:1, 1:1, and 1:3 in static plates or under excessive cyclic tensile strain of 10% and results were compared to culturing of both cell types alone with and without cyclic strain. Results indicate 75% of chondrocytes in engineered articular cartilage can be replaced with stem cells with enhanced collagen over all culture conditions and glycosaminoglycan content over stretched cultures of chondrocytes. This can be done without observing adverse effects on cell viability. Collagen and glycosaminoglycan secretion, when compared to chondrocyte alone under 10% strain, was enhanced 6.1- and 2-fold, respectively, by chondrocytes cocultivated with stem cells at a ratio of 1:3.

The effects of locomotion on bone marrow mesenchymal stem cell fate: insight into mechanical regulation and bone formation

Bone marrow mesenchymal stem cells (BMSCs) refer to a heterogeneous population of cells with the capacity for self-renewal. BMSCs have multi-directional differentiation potential and can differentiate into chondrocytes, osteoblasts, and adipocytes under specific microenvironment or mechanical regulation. The activities of BMSCs are closely related to bone quality. Previous studies have shown that BMSCs and their lineage-differentiated progeny (for example, osteoblasts), and osteocytes are mechanosensitive in bone. Thus, a goal of this review is to discuss how these ubiquious signals arising from mechanical stimulation are perceived by BMSCs and then how the cells respond to them. Studies in recent years reported a significant effect of locomotion on the migration, proliferation and differentiation of BMSCs, thus, contributing to our bone mass. This regulation is realized by the various intersecting signaling pathways including RhoA/Rock, IFG, BMP and Wnt signalling. The mechanoresponse of BMSCs also provides guidance for maintaining bone health by taking appropriate exercises. This review will summarize the regulatory effects of locomotion/mechanical loading on BMSCs activities. Besides, a number of signalling pathways govern MSC fate towards osteogenic or adipocytic differentiation will be discussed. The understanding of mechanoresponse of BMSCs makes the foundation for translational medicine.

Mechanical Stimulation and Diameter of Fiber Scaffolds Affect the Differentiation of Rabbit Annulus Fibrous Stem Cells

BACKGROUND

Degeneration of the annulus fibrosus (AF), an important structure of the intervertebral disc, is one of the main causes of degenerative disc disease. Fabrication of scaffolds replicating the stratified microstructure of the AF is critical for the successful regeneration of AF.

METHODS

In this study, we cultured rabbit AF-derived stem cells (AFSCs) using fabricated electrospun fibrous poly-L-lactic acid scaffolds with different diameters. We applied cyclic tensile strain (CTS) on the scaffolds to regulate the differentiation of AFSCs into specific cell types that resided at the inner, middle, and outer zones of the AF.

RESULTS

We found that the morphologies of AFSCs on the smaller-fiber-diameter scaffolds were nearly round, whereas spindle-like cells morphologies were observed on large-diameter scaffolds. CTS enhanced these phenomena and made the cells slender. The expression levels of collagen-I in cells increased as a function of the fiber diameter, whereas collagen-II and aggrecan exhibited opposite trends. Moreover, the application of CTS upregulated the gene expressions of collagen-I, collagen-II, and aggrecan.

CONCLUSION

Overlaying the scaffolds with different CTS-stimulated cells could eventually lead to engineered AF tissues with hierarchical structures that approximated the native AF tissue. Thus, the proposed methodologies could be potentially applied for AF regeneration.

Exosomes derived from umbilical cord mesenchymal stem cells in mechanical environment show improved osteochondral activity via upregulation of LncRNA H19

Background

Exosomes derived from stem cells have been demonstrated to be good candidates for the treatment of osteochondral injury. Our previous studies have demonstrated that mechanical stimulation could be crucial for the secretion of exosomes derived from umbilical cord mesenchymal stem cells (U-MSCs). Therefore, we explore whether mechanical stimulation caused by a rotary cell culture system (RCCS) has a beneficial effect on exosome yield and biological function.

Methods

U-MSCs were subjected to an RCCS at different rotational speeds and exosomes were characterised by transmission electron microscopy, nanoparticle tracking analysis and western blotting. small-interfering RNAs of Rab27a (siRNA-Rab27a) was used to reduce exosome production. Quantitative real-time PCR (qRT-PCR) was used to detect the expression of mechanically sensitive long non-coding RNA H19 (LncRNA H19). The effects of exosomes on chondrocyte proliferation were examined using cell counting kit-8 (CCK-8), toluidine blue staining and a series of related genes. Annexin V-FITC and PI (V-FITC/PI) flow cytometry was used to detect the effect of exosomes on the inhibition of chondrocyte apoptosis. Macroscopic evaluation, MRI quantification and immunohistochemical staining were conducted to investigate the in vivo effects of exosomal LncRNA H19 through SD rat cartilage defect models.

Results

RCCS significantly promoted exosome production at 36 rpm/min within 196 h. Mechanical stimulation was able to increase the expression level of exosomes. The exosomal LncRNA H19 was found to promote chondrocyte proliferation and matrix synthesis and inhibit apoptosis in vitro. Chondral regeneration activity was lost in LncRNA H19-defective exosomes. The injection of exosomal LncRNA H19 in vivo resulted in improved macroscopic assessment, MRI quantification and histological analysis. Moreover, exosomal LncRNA H19 was able to relieve pain levels during the early stages of cartilage repair in an animal experiment.

Conclusion

Our findings confirmed that mechanical stimulation can enhance exosome yield as well as biological function for the repair of cartilage defects. The underlying mechanism may be related to the high expression of LncRNA H19 in exosomes. The translational potential of this article: This study provides a theoretical support of optimizing exosome production. It advances the yield of mesenchymal stem cell exosome and facilitate the clinical application to repair of osteochondral damage.

Scaffold-Based Gene Therapeutics for Osteochondral Tissue Engineering

Significant progress in osteochondral tissue engineering has been made for biomaterials designed to deliver growth factors that promote tissue regeneration. However, due to diffusion characteristics of hydrogels, the accurate delivery of signaling molecules remains a challenge. In comparison to the direct delivery of growth factors, gene therapy can overcome these challenges by allowing the simultaneous delivery of growth factors and transcription factors, thereby enhancing the multifactorial processes of tissue formation. Scaffold-based gene therapy provides a promising approach for tissue engineering through transfecting cells to enhance the sustained expression of the protein of interest or through silencing target genes associated with bone and joint disease. Reports of the efficacy of gene therapy to regenerate bone/cartilage tissue regeneration are widespread, but reviews on osteochondral tissue engineering using scaffold-based gene therapy are sparse. Herein, we review the recent advances in gene therapy with a focus on tissue engineering scaffolds for osteochondral regeneration.