Mitochondrial transfer from bone mesenchymal stem cells protects against tendinopathy both in vitro and in vivo

Co-culture of STRO1 + human gingival mesenchymal stem cells and human umbilical vein endothelial cells in 3D spheroids: enhanced in vitro osteogenic and angiogenic capacities

Stem cell spheroid is a promising graft substitute for bone tissue engineering. Spheroids obtained by 3D culture of STRO1+ Gingival Mesenchymal Stem Cells (sGMSCs) (sGMSC spheroids, GS) seldom express angiogenic factors, limiting their angiogenic differentiation in vivo. This study introduced a novel stem cell spheroid with osteogenic and angiogenic potential through 3D co-culture of sGMSCs and Human Umbilical Vein Endothelial Cells (HUVECs) (sGMSC/HUVEC spheroids, GHS). GHS with varying seeding ratios of sGMSCs to HUVECs (GHR) were developed. Cell fusion within the GHS system was observed via immunofluorescence. Calcein-AM/PI staining and chemiluminescence assay indicated cellular viability within the GHS. Furthermore, osteogenic and angiogenic markers, including ALP, OCN, RUNX2, CD31, and VEGFA, were quantified and compared with the control group comprising solely of sGMSCs (GS). Incorporating HUVECs into GHS extended cell viability and stability, initiated the expression of angiogenic factors CD31 and VEGFA, and upregulated the expression of osteogenic factors ALP, OCN, and RUNX2, especially when GHS with a GHR of 1:1. Taken together, GHS, derived from the 3D co-culture of sGMSCs and HUVECs, enhanced osteogenic and angiogenic capacities in vitro, extending the application of cell therapy in bone tissue engineering.

Mesenchymal Stem/Progenitor Cells and Their Derivates in Tissue Regeneration-Part II

During the last three decades, mesenchymal stem/stromal cells (MSCs) were extensively studied, and are mainly considered within the setting of their regenerative and immunomodulatory properties in tissue regeneration [...].

Connexin 43 Regulates Intercellular Mitochondrial Transfer from Human Mesenchymal Stromal Cells to Chondrocytes

Background

The phenomenon of intercellular mitochondrial transfer from mesenchymal stromal cells (MSCs) has shown promise for improving tissue healing after injury and has potential for treating degenerative diseases like osteoarthritis (OA). Recently MSC to chondrocyte mitochondrial transfer has been documented, but the mechanism of transfer is unknown. Full-length connexin43 (Cx43, encoded by GJA1 ) and the truncated internally translated isoform GJA1-20k have been implicated in mitochondrial transfer between highly oxidative cells, but have not been explored in orthopaedic tissues. Here, our goal was to investigate the role of Cx43 in MSC to chondrocyte mitochondrial transfer. In this study, we tested the hypotheses that (a) mitochondrial transfer from MSCs to chondrocytes is increased when chondrocytes are under oxidative stress and (b) MSC Cx43 expression mediates mitochondrial transfer to chondrocytes.

Methods

Oxidative stress was induced in immortalized human chondrocytes using tert-Butyl hydroperoxide (t-BHP) and cells were evaluated for mitochondrial membrane depolarization and reactive oxygen species (ROS) production. Human bone-marrow derived MSCs were transduced for mitochondrial fluorescence using lentiviral vectors. MSC Cx43 expression was knocked down using siRNA or overexpressed (GJA1+ and GJA1-20k+) using lentiviral transduction. Chondrocytes and MSCs were co-cultured for 24 hrs in direct contact or separated using transwells. Mitochondrial transfer was quantified using flow cytometry. Co-cultures were fixed and stained for actin and Cx43 to visualize cell-cell interactions during transfer.

Results

Mitochondrial transfer was significantly higher in t-BHP-stressed chondrocytes. Contact co-cultures had significantly higher mitochondrial transfer compared to transwell co-cultures. Confocal images showed direct cell contacts between MSCs and chondrocytes where Cx43 staining was enriched at the terminal ends of actin cellular extensions containing mitochondria in MSCs. MSC Cx43 expression was associated with the magnitude of mitochondrial transfer to chondrocytes; knocking down Cx43 significantly decreased transfer while Cx43 overexpression significantly increased transfer. Interestingly, GJA1-20k expression was highly correlated with incidence of mitochondrial transfer from MSCs to chondrocytes.

Conclusions

Overexpression of GJA1-20k in MSCs increases mitochondrial transfer to chondrocytes, highlighting GJA1-20k as a potential target for promoting mitochondrial transfer from MSCs as a regenerative therapy for cartilage tissue repair in OA.

Early delivery of human umbilical cord mesenchymal stem cells improves healing in a rat model of Achilles tendinopathy

Objective: This study aimed to explore the efficacy and optimal delivery time of human umbilical cord mesenchymal stem cells (hUC-MSCs) in treating collagenase-induced Achilles tendinopathy. Methods: Achilles tendinopathy in rats at early or advanced stages was induced by injecting collagenase I into bilateral Achilles tendons. A total of 28 injured rats were injected with a hUC-MSC solution or normal saline into bilateral tendons twice and sampled after 4 weeks for histological staining, gene expression analysis, transmission electron microscope assay and biomechanical testing analysis. Results: The results revealed better histological performance and a larger collagen fiber diameter in the MSC group. mRNA expression of TNF-α, IL-1β and MMP-3 was lower after MSC transplantation. Early MSC delivery promoted collagen I and TIMP-3 synthesis, and strengthened tendon toughness. Conclusion: hUC-MSCs demonstrated a therapeutic effect in treating collagenase-induced Achilles tendinopathy, particularly in the early stage of tendinopathy.

Low-Intensity Pulsed Ultrasound Promotes the Repair of Achilles Tendinopathy by Downregulating the JAK/STAT Signaling Pathway in Rabbits

Tendinopathy is a complex tendon injury or pathology outcome, potentially leading to permanent impairment. Low-intensity pulsed ultrasound (LIPUS) is emerging as a treatment modality for tendon disorders. However, the optimal treatment duration and its effect on tendons remain unclear. This study aims to investigate the efficacy of LIPUS in treating injured tendons, delineate the appropriate treatment duration, and elucidate the underlying treatment mechanisms through animal experiments. Ninety-six three-month-old New Zealand white rabbits were divided into normal control (NC) and model groups. The model group received Prostaglandin E2 (PGE2) injections to induce Achilles tendinopathy. They were then divided into model control (MC) and LIPUS treatment (LT) groups. LT received LIPUS intervention with a 1-MHz frequency, a pulse repetition frequency (PRF) of 1 kHz, and spatial average temporal average sound intensity ( [Formula: see text]) of 100 mW/cm2. MC underwent a sham ultrasound, and NC received no treatment. Assessments on 1, 4, 7, 14, and 28 days after LT included shear wave elastography (SWE), mechanical testing, histologic evaluation, ribonucleic acid sequencing (RNA-seq), polymerase chain reaction (PCR), and western blot (WB) analysis. SWE results showed that the shear modulus in the LT group was significantly higher than that in the MC group after LT for seven days. Histological results demonstrated improved tendon tissue alignment and fibroblast distribution after LT. Molecular analyses suggested that LIPUS may downregulate the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway and regulate inflammatory and matrix-related factors. We concluded that LT enhanced injured tendon elasticity and accelerated Achilles tendon healing. The study highlighted the JAK/STAT signaling pathway as a potential therapeutic target for LT of Achilles tendinopathy, guiding future research.