Photochemical tissue bonding promotes the proliferation and migration of injured tenocytes through ROS/RhoA/NF-κB/Dynamin 2 signaling pathway

Effects of Low-Intensity Pulsed Ultrasound in Tendon Injuries

Tendon injuries are the most common soft tissue injuries, caused by tissue overuse and age-related degeneration. However, the tendon repair process is slow and inefficient due to the lack of cellular structure and blood vessels in the tendon. Low-intensity pulsed ultrasound (LIPUS) has received increasing attention as a non-invasive, simple, and safe way to promote tendon healing. This review summarizes the effects and underlying mechanisms of LIPUS on tendon injury by comprehensively examining the published literature, including in vitro, in vivo, and clinical studies. This review reviewed 24 studies, with 87.5% showing improvement. The application of LIPUS in tendon diseases is a promising field worthy of further study.

Di-n-butyl phthalate induces oversecretion of vascular endothelium-derived NAP-2 and promotes epithelial-mesenchymal transition of urothelial cells in newborn hypospadias rats

Di-n-butyl phthalate (DBP) is a plasticizer commonly used in industrial production and is present in our daily life. It has been confirmed that DBP causes genitourinary malformations, especially hypospadias. However, the research of hypospadias mainly focusses on the genital tubercle in previous studies. In this study, we found DBP could affect the exocrine function of the vascular endothelium which disturb the development of genital nodules and induced hypospadias. We used cytokine array to find that vascular endothelium-derived NAP-2 may be a major abnormal secreted cytokine with biological functions. The transcriptomic sequencing analysis showed that abnormal activation of the RhoA/ROCK signaling pathway was the main reason for increased NAP-2 secretion. The expression levels of epithelial-mesenchymal transition (EMT) biomarkers and NAP-2 in hypospadias animal models were detected with Immunohistochemistry, Western blot, Immunofluorescence, and ELISA methods. The expression levels of NAP-2, RhoA/ROCK signaling pathway related proteins, reactive oxygen species (ROS) levels in HUVEC cells, EMT biomarkers and migration capacity of urothelial cells cocultured with HUVEC were measured with ELISA, flow cytometry, Western blot or Transwell assay for further cell experiments. The results showed that DBP leaded to NAP-2 oversecretion from vascular endothelium mainly rely on the activation of RhoA/ROCK signaling pathway and ROS accumulation. The RhoA/ROCK inhibitor fasudil could partially decrease ROS production, and both fasudil and N-acetyl-L-cysteine (NAC) could decrease NAP-2 secretion. Meanwhile, the oversecretion of NAP-2 from HUVEC in coculture system promoted EMT and migration capacity of urothelial cells, and TGF-β inhibitor LY219761 could block the aberrant activation of EMT process. Therefore, it could be concluded that DBP increase NAP-2 secretion from vascular endothelium by RhoA/ROCK/ROS pathway, and further promote EMT in urothelial cells through TGF-β pathway. This study provided a novel direction for studying the occurrence of hypospadias and may provide a hypospadias predictive marker in the future.

Soft nano and microstructures for the photomodulation of cellular signaling and behavior

Photoresponsive soft materials are everywhere in the nature, from human's retina tissues to plants, and have been the inspiration for engineers in the development of modern biomedical materials. Light as an external stimulus is particularly attractive because it is relatively cheap, noninvasive to superficial biological tissues, can be delivered contactless and offers high spatiotemporal control. In the biomedical field, soft materials that respond to long wavelength or that incorporate a photon upconversion mechanism are desired to overcome the limited UV-visible light penetration into biological tissues. Upon light exposure, photosensitive soft materials respond through mechanisms of isomerization, crosslinking or cleavage, hyperthermia, photoreactions, electrical current generation, among others. In this review, we discuss the most recent applications of photosensitive soft materials in the modulation of cellular behavior, for tissue engineering and regenerative medicine, in drug delivery and for phototherapies.

The 532 nm Laser Treatment Promotes the Proliferation of Tendon-Derived Stem Cells and Upregulates Nr4a1 to Stimulate Tenogenic Differentiation

Objective: This study aimed to verify the effect of photobiomodulation therapy (PBMT) with a wavelength of 532 nm on the proliferation and differentiation of tendon-derived stem cells (TDSCs) of Sprague-Dawley (SD) rats. Background: The combination of PBMT and stem cell transplantation with TDSCs provides a new treatment strategy for tendon injury. Nevertheless, the effect of PBMT on the biological behavior of TDSCs and its internal mechanisms remain unclear. Methods: TDSCs were isolated from Achilles tendons of SD rats and identified by cell morphology and flow cytometric analysis. Energy density gradient experiment was performed to determine the ideal energy. Then, TDSCs were treated with PBMT using a wavelength of 532 nm at a fluence of 15 J/cm² in 532 nm laser group, and the TDSC in control group were not treated with 532 nm laser. Cell response after irradiation was observed to ascertain cell morphology and cell proliferation in the 532 nm laser group and the control group. The RNA expression levels of the key genes of TDSC differentiation, including scleraxis (Scx), tenomodulin (Tnmd), Mohawk homeobox (Mkx), Decorin (Dcn), peroxisome proliferator-activated receptor gamma (PPARγ), SRY-box transcription factor 9 (Sox9), and RUNX family transcription factor 2 (Runx2), were detected by reverse transcription-polymerase chain reaction. Then, gene chip microarray was used to detect the expression of differential genes after 532 nm laser intervention in TDSCs, and the target genes were screened out to verify the role in this process in vitro and in vivo. Results: When the 532 nm laser energy density was 15 J/cm², the proliferation capacity of TDSCs was improved (2.73 ± 0.24 vs. 1.81 ± 0.71, p < 0.05), and the expression of genes related to tenogenic differentiation of TDSCs was significantly increased (p < 0.01). After RNA sequencing and bioinformatics analyses, we speculated that nuclear receptor subfamily 4 group A member 1 (Nr4a1) was involved in the tenogenic differentiation process of TDSCs regulated by 532 nm laser treatment. Subsequent experiments confirmed that Nr4a1 regulated the expression of the tenogenic differentiation genes Scx and Tnmd in TDSCs. Conclusions: A 532 nm laser with 15 J/cm² regulated the process of TDSC proliferation and upregulated Nr4a1 to stimulate tenogenic differentiation.

Roles of Oxidative Stress in Acute Tendon Injury and Degenerative Tendinopathy-A Target for Intervention

Both acute and chronic tendon injuries are disabling sports medicine problems with no effective treatment at present. Sustained oxidative stress has been suggested as the major factor contributing to fibrosis and adhesion after acute tendon injury as well as pathological changes of degenerative tendinopathy. Numerous in vitro and in vivo studies have shown that the inhibition of oxidative stress can promote the tenogenic differentiation of tendon stem/progenitor cells, reduce tissue fibrosis and augment tendon repair. This review aims to systematically review the literature and summarize the clinical and pre-clinical evidence about the potential relationship of oxidative stress and tendon disorders. The literature in PubMed was searched using appropriate keywords. A total of 81 original pre-clinical and clinical articles directly related to the effects of oxidative stress and the activators or inhibitors of oxidative stress on the tendon were reviewed and included in this review article. The potential sources and mechanisms of oxidative stress in these debilitating tendon disorders is summarized. The anti-oxidative therapies that have been examined in the clinical and pre-clinical settings to reduce tendon fibrosis and adhesion or promote healing in tendinopathy are reviewed. The future research direction is also discussed.

Exosomes derived from human umbilical cord mesenchymal stem cells reduce tendon injuries via the miR-27b-3p/ARHGAP5/RhoA signaling pathway

Tendon injuries are common clinical issues resulted from tissue overuse and age-related degeneration. Previous sutdies have suggested that exosomes secreted by mesenchymal stem cells (MSCs) contribute to tissue injury repair. Here, we provide evidence for a critical role of human umbilical cord mesenchymal stem cell (hucMSC)-derived exosomes in reducing tendon injury by activating the RhoA signaling. Treatment of primary injured tenocytes with hucMSC exosomes increases cell proliferation and invasion, which correlates with increased RhoA activity. RhoA mediates the effects of hucMSC exosomes, as treatment of primary injured tenocytes with the RhoA inhibitor, CCG-1423, abolishes the effects of hucMSC exosomes on cell proliferation and invasion. Mechanistically, we observe that hucMSC exosomes induce the expression of a microRNA, miR-27b-3p, which targets and suppresses ARHGAP5, a negative regulator of RhoA. Consistent with this observation, ARHGAP5 overexpression suppresses the effects of hucMSC exosomes on cell proliferation and invasion, while knockdown of ARHGAP5 rescues these effects. Finally, we demonstrate the functional significance of our findings using an Achilles tendon injury model and show that treatment with exosomes reduces tendon injury in rats, which correlates with increased RhoA activity and reduced ARHGAP5 expression. Taken together, our findings highlight a critical role of hucMSC exosomes in reducing tendon injury via miR-27b-3p-mediated suppression of ARHGAP5, resulting in RhoA activation, and leading to increased cell proliferation and invasion of primary injured tenocytes.

Noninvasive Photochemical Sealing for Achilles Tendon Rupture by Combination of Upconversion Nanoparticles and Photochemical Tissue Bonding Technology

Photochemical tissue bonding (PTB), based on photosensitizer rose bengal (RB) and green light, has been regarded as an effective alternative to surgical suture and has been reported to provide benefits for Achilles tendon repair. Limited to the poor penetration of green light, secondary damage still exists while applying PTB for closed Achilles tendon rupture. This study is aimed at exploring the effects of noninvasive photochemical sealing on Achilles tendon rupture by the combination of PTB and upconversion nanoparticles (UCNPs). The rare-earth UCNPs of NaYF₄ : Yb/Er (Y : Yb : Er = 78 : 20 : 2) were fabricated and then loaded into Chitosan/β-GP hydrogel containing RB to prepare UCNPs@RB/Chitosan/β-GP hydrogel. The properties of UCNPs and UCNP/Chitosan/β-GP hydrogel were characterized by TEM, SEM, DLS, and FTIR analysis. The effects of UCNP and PTB combination were evaluated in an Achilles tendon rupture rat model using histological analysis. Bioluminescence imaging of ROS was performed to explore the potential mechanism. UCNPs had a uniform shape with a diameter of 29.7 ± 2.6 nm. The UCNPs@RB/Chitosan/β-GP hydrogel could upconvert the near-infrared light into green light. The results of histological assessment showed that compared with traditional suture repair, the rats injected with UCNPs@RB/Chitosan/β-GP hydrogel followed by irradiating with near-infrared light and the rats treated with RB solution followed by irradiating with green light had better effects on Achilles tendon repair. The benefits might be related to the generation of ROS in the PTB process. These findings indicated that the combination of PTB and UCNPs@RB/Chitosan/β-GP hydrogel could be used as a noninvasive photochemical sealing for Achilles tendon rupture.