Tenomodulin highly expressing MSCs as a better cell source for tendon injury healing

Hydrogel-Loaded Exosomes: A Promising Therapeutic Strategy for Musculoskeletal Disorders

Clinical treatment strategies for musculoskeletal disorders have been a hot research topic. Accumulating evidence suggests that hydrogels loaded with MSC-derived EVs show great potential in improving musculoskeletal injuries. The ideal hydrogels should be capable of promoting the development of new tissues and simulating the characteristics of target tissues, with the properties matching the cell-matrix constituents of autologous tissues. Although there have been numerous reports of hydrogels loaded with MSC-derived EVs for the repair of musculoskeletal injuries, such as intervertebral disc injury, tendinopathy, bone fractures, and cartilage injuries, there are still many hurdles to overcome before the clinical application of modified hydrogels. In this review, we focus on the advantages of the isolation technique of EVs in combination with different types of hydrogels. In this context, the efficacy of hydrogels loaded with MSC-derived EVs in different musculoskeletal injuries is discussed in detail to provide a reference for the future application of hydrogels loaded with MSC-derived EVs in the clinical treatment of musculoskeletal injuries.

Age-related cellular and microstructural changes in the rotator cuff enthesis

Rotator cuff injuries increase with age. The enthesis is the most frequent site of rotator cuff injury and degeneration. Understanding age-related changes of the enthesis are essential to determine the mechanism of rotator cuff injuries, degeneration, and to guide mechanistically driven therapies. In this study, we explored age-related cellular changes of the rotator cuff enthesis in young, mature, and aged rats. Here we found that the aged enthesis is typified by an increased mineralized zone and decreased nonmineralized zone. Proliferation, migration, and colony-forming potential of rotator cuff derived cells (RCECs) was attenuated with aging. The tenogenic and chondrogenic potential were significantly reduced, while the osteogenic potential increased in aged RCECs. The adipogenic potential increased in RCECs with age. This study explores the cellular differences found between young, mature, and aged rotator cuff enthesis cells and highlights the importance of using age-appropriate models, as well as provides a basis for further delineation of mechanisms and potential therapeutics for rotator cuff injuries.

Magnetic Nanoparticle-Mediated Orientation of Collagen Hydrogels for Engineering of Tendon-Mimetic Constructs

Despite the high incidence of tendon injuries worldwide, an optimal treatment strategy has yet to be defined. A key challenge for tendon repair is the alignment of the repaired matrix into orientations which provide maximal mechanical strength. Using oriented implants for tissue growth combined with either exogenous or endogenous stem cells may provide a solution. Previous research has shown how oriented fiber-like structures within 3D scaffolds can provide a framework for organized extracellular matrix deposition. In this article, we present our data on the remote magnetic alignment of collagen hydrogels which facilitates long-term collagen orientation. Magnetic nanoparticles (MNPs) at varying concentrations can be contained within collagen hydrogels. Our data show how, in response to the magnetic field lines, MNPs align and form string-like structures orientating at 90 degrees from the applied magnetic field from our device. This can be visualized by light and fluorescence microscopy, and it persists for 21 days post-application of the magnetic field. Confocal microscopy demonstrates the anisotropic macroscale structure of MNP-laden collagen gels subjected to a magnetic field, compared to gels without MNP dosing. Matrix fibrillation was compared between non- and biofunctionalized MNP hydrogels, and different gels dosed with varying MNP concentrations. Human adipose stem cells (hASCs) seeded within the magnetically aligned gels were observed to align in parallel to MNP and collagen orientation 7 days post-application of the magnetic field. hASCs seeded in isotropic gels were randomly organized. Tenocyte-likeness of the cells 7 days post-seeding in collagen I scaffolds was confirmed by the positive expression of tenomodulin and scleraxis proteins. To summarize, we have developed a convenient, non-invasive protocol to control the collagen I hydrogel architecture. Through the presence or absence of MNP dosing and a magnetic field, collagen can be remotely aligned or randomly organized, respectively, in situ. Tendon-like cells were observed to organize in parallel to unidirectionally aligned collagen fibers and polydirectionally in non-aligned collagen constructs. In this way, we were able to engineer the constructs emulating a physiologically and pathologically relevant tendon niche. This can be considered as an innovative approach particularly useful in tissue engineering or organ-on-a-chip applications for remotely controlling collagen matrix organization to recapitulate the native tendon.

Stem cells in tendon regeneration and factors governing tenogenesis

Tendons are connective tissue structures of paramount importance to the human ability of locomotion. Tendinopathy and tendon rupture can be resistant to treatment and often recurs, thus resulting in a significant health problem with a relevant social impact worldwide. Unfortunately, existing treatment approaches are suboptimal. A better understanding of the basic biology of tendons may provide a better way to solve these problems and promote tendon regeneration. Stem cells, either obtained from tendons or non-tendon sources, such as bone marrow (BMSCs), adipose tissue (AMSCs), as well as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), have received increasing attention toward enhancing tendon healing. There are many studies showing that stem cells can contribute to improving tendon healing. Hence, in this review, the current knowledge of BMSCs, AMSCs, TSPCs, ESCs and iPSCs for tendon regeneration, as well as the advantages and limitations among them, has been highlighted. Moreover, the transcriptional and bioactive factors governing tendon healing processes have been discussed.

Nonwoven-based gelatin/polycaprolactone membrane loaded with ERK inhibitor U0126 for treatment of tendon defects

BACKGROUND

Tendon is a major component of musculoskeletal system connecting the muscles to the bone. Tendon injuries are very common orthopedics problems leading to impeded motion. Up to now, there still lacks effective treatments for tendon diseases.

METHODS

Tendon stem/progenitor cells (TSPCs) were isolated from the patellar tendons of SD rats. The expression levels of genes were evaluated by quantitative RT-PCR. Immunohistochemistry staining was performed to confirm the presence of tendon markers in tendon tissues. Bioinformatics analysis of data acquired by RNA-seq was used to find out the differentially expressed genes. Rat patellar tendon injury model was used to evaluate the effect of U0126 on tendon injury healing. Biomechanical testing was applied to evaluate the mechanical properties of newly formed tendon tissues.

RESULTS

In this study, we have shown that ERK inhibitor U0126 rather PD98059 could effectively increase the expression of tendon-related genes and promote the tenogenesis of TSPCs in vitro. To explore the underlying mechanisms, RNA sequencing was performed to identify the molecular difference between U0126-treated and control TSPCs. The result showed that GDF6 was significantly increased by U0126, which is an important factor of the TGFβ superfamily regulating tendon development and tenogenesis. In addition, NBM (nonwoven-based gelatin/polycaprolactone membrane) which mimics the native microenvironment of the tendon tissue was used as an acellular scaffold to carry U0126. The results demonstrated that when NBM was used in combination with U0126, tendon healing was significantly promoted with better histological staining outcomes and mechanical properties.

CONCLUSION

Taken together, we have found U0126 promoted tenogenesis in TSPCs through activating GDF6, and NBM loaded with U0126 significantly promoted tendon defect healing, which provides a new treatment for tendon injury.

Extracellular Vesicles of Adipose-Derived Stem Cells Promote the Healing of Traumatized Achilles Tendons

Healing of ruptured tendons remains a clinical challenge because of its slow progress and relatively weak mechanical force at an early stage. Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have therapeutic potential for tissue regeneration. In this study, we isolated EVs from adipose-derived stem cells (ADSCs) and evaluated their ability to promote tendon regeneration. Our results indicated that ADSC-EVs significantly enhanced the proliferation and migration of tenocytes in vitro. To further study the roles of ADSC-EVs in tendon regeneration, ADSC-EVs were used in Achilles tendon repair in rabbits. The mechanical strength, histology, and protein expression in the injured tendon tissues significantly improved 4 weeks after ADSC-EV treatment. Decorin and biglycan were significantly upregulated in comparison to the untreated controls. In summary, ADSC-EVs stimulated the proliferation and migration of tenocytes and improved the mechanical strength of repaired tendons, suggesting that ADSC-EV treatment is a potential highly potent therapeutic strategy for tendon injuries.

Stretch-Induced Tenomodulin Expression Promotes Tenocyte Migration via F-Actin and Chromatin Remodeling

The mechanosensitive gene tenomodulin (Tnmd) is implicated in tendon maturation and repair. However, the mechanism by which mechanical loading regulates Tnmd's expression and its role in tenocyte migration is yet to be defined. Here, we show that Tnmd and migration were upregulated in uniaxial cyclic stress-stimulated tenocytes. The knockdown of Tnmd reduced cell migration in the presence and absence of mechanical loading, suggesting that Tnmd is involved in tenocyte migration. Moreover, the treatment of stress-stimulated tenocytes with the actin inhibitor latrunculin (Lat A), histone acetyltransferase inhibitor anacardic acid (ANA), or histone demethylases inhibitor GSK-J4 suppressed Tnmd expression and tenocyte migration. These results show that actin stress fiber formation and chromatin decondensation regulates Tnmd expression, which might then regulate tenocyte migration. Thus, this study proposes the involvement of the actin and chromatin mechanotransduction pathway in the regulation of Tnmd and reveals a novel role of Tnmd in tenocyte migration. The identification of Tnmd function in tenocyte migration provides insight into the molecular mechanisms involved in Tnmd-mediated tendon repair.

Biomanufacturing organized collagen-based microfibers as a Tissue ENgineered Device (TEND) for tendon regeneration

Approximately 800, 000 surgical repairs are performed annually in the U.S. for debilitating injuries to ligaments and tendons of the foot, ankle, knee, wrist, elbow and shoulder, presenting a significant healthcare burden. To overcome current treatment shortcomings and advance the treatment of tendon and ligament injuries, we have developed a novel electrospun Tissue ENgineered Device (TEND), comprised of type I collagen and poly(D,L-lactide) (PDLLA) solubilized in a benign solvent, dimethyl sulfoxide (DMSO). TEND fiber alignment, diameter and porosity were engineered to enhance cell infiltration leading to promote tissue integration and functional remodeling while providing biomechanical stability. TEND rapidly adsorbs blood and platelet-rich-plasma (PRP), and gradually releases growth factors over two weeks. TEND further supported cellular alignment and upregulation of tenogenic genes from clinically relevant human stem cells within three days of culture. TEND implanted in a rabbit Achilles tendon injury model showed new in situ tissue generation, maturation, and remodeling of dense, regularly oriented connective tissue in vivo. In all, TEND's organized microfibers, biological fluid and cell compatibility, strength and biocompatiblility make significant progress towards clinically translating electrospun collagen-based medical devices for improving the clinical outcomes of tendon injuries.

Genome-wide association identifies seven loci for pelvic organ prolapse in Iceland and the UK Biobank

Pelvic organ prolapse (POP) is a downward descent of one or more of the pelvic organs, resulting in a protrusion of the vaginal wall and/or uterus. We performed a genome-wide association study of POP using data from Iceland and the UK Biobank, a total of 15,010 cases with hospital-based diagnosis code and 340,734 female controls, and found eight sequence variants at seven loci associating with POP (P < 5 × 10-8); seven common (minor allele frequency >5%) and one with minor allele frequency of 4.87%. Some of the variants associating with POP also associated with traits of similar pathophysiology. Of these, rs3820282, which may alter the estrogen-based regulation of WNT4, also associates with leiomyoma of uterus, gestational duration and endometriosis. Rs3791675 at EFEMP1, a gene involved in connective tissue homeostasis, also associates with hernias and carpal tunnel syndrome. Our results highlight the role of connective tissue metabolism and estrogen exposure in the etiology of POP.

Aspirin promotes tenogenic differentiation of tendon stem cells and facilitates tendinopathy healing through regulating the GDF7/Smad1/5 signaling pathway

Tendinopathy is a common musculoskeletal system disorder in sports medicine, but regeneration ability of injury tendon is limited. Tendon stem cells (TSCs) have shown the definitive treatment evidence for tendinopathy and tendon injuries due to their tenogenesis capacity. Aspirin, as the representative of nonsteroidal anti-inflammatory drugs for its anti-inflammatory and analgestic actions, has been commonly used in treating tendinopathy in clinical, but the effect of aspirin on tenogenesis of TSCs is unclear. We hypothesized that aspirin could promote injury tendon healing through inducing TSCs tenogenesis. The aim of the present study is to make clear the effect of aspirin on TSC tenogenesis and tendon healing in tendinopathy, and thus provide new treatment evidence and strategy of aspirin for clinical practice. First, TSCs were treated with aspirin under tenogenic medium for 3, 7, and 14 days. Sirius Red staining was performed to observe the TSC differentiation. Furthermore, RNA sequencing was utilized to screen out different genes between the induction group and aspirin treatment group. Then, we identified the filtrated molecules and compared their effect on tenogenesis and related signaling pathway. At last, we constructed the tendinopathy model and compared biomechanical changes after aspirin intake. From the results, we found that aspirin promoted tenogenesis of TSCs. RNA sequencing showed that growth differentiation factor 6 (GDF6), GDF7, and GDF11 were upregulated in induction medium with the aspirin group compared with the induction medium group. GDF7 increased tenogenesis and activated Smad1/5 signaling. In addition, aspirin increased the expression of TNC, TNMD, and Scx and biomechanical properties of the injured tendon. In conclusion, aspirin promoted TSC tenogenesis and tendinopathy healing through GDF7/Smad1/5 signaling, and this provided new treatment evidence of aspirin for tendinopathy and tendon injuries.

Evaluation of tenogenic differentiation potential of selected subpopulations of human adipose-derived stem cells

Identification of a suitable cell source and bioactive agents guiding cell differentiation towards tenogenic phenotype represents a prerequisite for advancement of cell-based therapies for tendon repair. Human adipose-derived stem cells (hASCs) are a promising, yet intrinsically heterogenous population with diversified differentiation capacities. In this work, we investigated antigenically-defined subsets of hASCs expressing markers related to tendon phenotype or associated with pluripotency that might be more prone to tenogenic differentiation, when compared to unsorted hASCs. Subpopulations positive for tenomodulin (TNMD+ hASCs) and stage specific early antigen 4 (SSEA-4+ hASCs), as well as unsorted ASCs were cultured up to 21 days in basic medium or media supplemented with TGF-β3 (10 ng/ml), or GDF-5 (50 ng/ml). Cell response was evaluated by analysis of expression of tendon-related markers at gene level and protein level by real time RT-PCR, western blot, and immunocytochemistry. A significant upregulation of scleraxis was observed for both subpopulations and unsorted hASCs in the presence of TGF-β3. More prominent alterations in gene expression profile in response to TGF-β3 were observed for TNMD+ hASCs. Subpopulations evidenced an increased collagen III and TNC deposition in basal medium conditions in comparison with unsorted hASCs. In the particular case of TNMD+ hASCs, GDF-5 seems to influence more the deposition of TNC. Within hASCs populations, discrete subsets could be distinguished offering varied sensitivity to specific biochemical stimulation leading to differential expression of tenogenic components suggesting that cell subsets may have distinctive roles in the complex biological responses leading to tenogenic commitment to be further explored in cell based strategies for tendon tissues.

Exosomes from tendon stem cells promote injury tendon healing through balancing synthesis and degradation of the tendon extracellular matrix

Tendon injuries are common musculoskeletal system disorders in clinical, but the regeneration ability of tendon is limited. Tendon stem cells (TSCs) have shown promising effect on tissue engineering and been used for the treatment of tendon injury. Exosomes that serve as genetic information carriers have been implicated in many diseases and physiological processes, but effect of exosomes from TSCs on tendon injury repair is unclear. The aim of this study is to make clear that the effect of exosomes from TSCs on tendon injury healing. Exosomes were harvested from conditioned culture media of TSCs by a sequential centrifugation process. Rat Achilles tendon tendinopathy model was established by collagenase‐I injection. This was followed by intra‐Achilles‐tendon injection with TSCs or exosomes. Tendon healing and matrix degradation were evaluated by histology analysis and biomechanical test at the post‐injury 5 weeks. In vitro, TSCs treated with interleukin 1 beta were added by conditioned medium including exosomes or not, or by exosomes or not. Tendon matrix related markers and tenogenesis related markers were measured by immunostaining and western blot. We found that TSCs injection and exosomes injection significantly decreased matrix metalloproteinases (MMP)‐3 expression, increased expression of tissue inhibitor of metalloproteinase‐3 (TIMP‐3) and Col‐1a1, and increased biomechanical properties of the ultimate stress and maximum loading. In vitro, conditioned medium with exosomes and exosomes also significantly decreased MMP‐3, and increased expression of tenomodulin, Col‐1a1 and TIMP‐3. Exosomes from TSCs could be an ideal therapeutic strategy in tendon injury healing for its balancing tendon extracellular matrix and promoting the tenogenesis of TSCs.

The Influence of Cell Source and Donor Age on the Tenogenic Potential and Chemokine Secretion of Human Mesenchymal Stromal Cells

Background

Cellular therapy is proposed for tendinopathy treatment. Bone marrow- (BM-MSC) and adipose tissue- (ASC) derived mesenchymal stromal cells are candidate populations for such a therapy. The first aim of the study was to compare human BM-MSCs and ASCs for their basal expression of factors associated with tenogenesis as well as chemotaxis. The additional aim was to evaluate if the donor age influences these features.

Methods

Cells were isolated from 24 human donors, 8 for each group: hASC, hBM-MSC Y (age ≤ 45), and hBM-MSC A (age > 45). The microarray analysis was performed on RNA isolated from hASC and hBM-MSC A cells. Based on microarray results, 8 factors were chosen for further evaluation. Two genes were additionally included in the analysis: SCLERAXIS and PPARγ. All these 10 factors were tested for gene expression by the qRT-PCR method, and all except of RUNX2 were additionally evaluated for protein expression or secretion.

Results

Microarray analysis showed over 1,400 genes with a significantly different expression between hASC and hBM-MSC groups. Eight of these genes were selected for further analysis: CXCL6, CXCL12, CXCL16, TGF-β2, SMAD3, COLLAGEN 14A1, MOHAWK, and RUNX2. In the subsequent qRT-PCR analysis, hBM-MSCs showed a significantly higher expression than did hASCs in following genes: CXCL12, CXCL16, TGF-β2, SMAD3, COLLAGEN 14A1, and SCLERAXIS (p < 0.05, regardless of BM donor age). In the case of CXCL12, the difference between hASC and hBM-MSC was significant only for younger BM donors, whereas for COLLAGEN 14A1—only for elder BM donors. PPARγ displayed a higher expression in hASCs compared to hBM-MSCs. In regard to CXCL6, MOHAWK, and RUNX2 gene expression, no statistically significant differences between groups were observed.

Conclusions

In the context of cell-based therapy for tendinopathies, bone marrow appears to be a more attractive source of MSCs than does adipose tissue. The age of cell donors seems to be less important than cell source, although cells from elder donors show slightly higher basal tenogenic potential than do cells from younger donors.

Tendon Tissue Engineering: Effects of Mechanical and Biochemical Stimulation on Stem Cell Alignment on Cell-Laden Hydrogel Yarns

Fiber-based approaches hold great promise for tendon tissue engineering enabling the possibility of manufacturing aligned hydrogel filaments that can guide collagen fiber orientation, thereby providing a biomimetic micro-environment for cell attachment, orientation, migration, and proliferation. In this study, a 3D system composed of cell-laden, highly aligned hydrogel yarns is designed and obtained via wet spinning in order to reproduce the morphology and structure of tendon fascicles. A bioink composed of alginate and gelatin methacryloyl (GelMA) is optimized for spinning and loaded with human bone morrow mesenchymal stem cells (hBM-MSCs). The produced scaffolds are subjected to mechanical stretching to recapitulate the strains occurring in native tendon tissue. Stem cell differentiation is promoted by addition of bone morphogenetic protein 12 (BMP-12) in the culture medium. The aligned orientation of the fibers combined with mechanical stimulation results in highly preferential longitudinal cell orientation and demonstrates enhanced collagen type I and III expression. Additionally, the combination of biochemical and mechanical stimulations promotes the expression of specific tenogenic markers, signatures of efficient cell differentiation towards tendon. The obtained results suggest that the proposed 3D cell-laden aligned system can be used for engineering of scaffolds for tendon regeneration.