VEGF promotes tendon regeneration of aged rats by inhibiting adipogenic differentiation of tendon stem/progenitor cells and promoting vascularization

Leptin promotes tendon stem/progenitor cell senescence through the AKT-mTOR signaling pathway

Dysregulated adipokine production is an influencing factor for the homeostatic imbalance of tendons. High levels of serum leptin may be a potential link between increasing adiposity and tendinopathy, while the detailed mechanistic explanation was not well-defined. In this study, we investigated the regulatory role of leptin in the tendon stem/progenitor cells (TSPCs) and the molecular mechanism within, and determined the effect of high levels of leptin on tendon recovery. We demonstrated that leptin reduced the viability of isolated rat TSPCs in a dose-dependent way, accompanied with increased transdifferentiation and altered gene expression of a series of extracellular matrix (ECM) enzymatic modulators. Also, we found that leptin could dose-dependently promote TSPCs senescence, while exhibiting limited effect in apoptotic or autophagic induction. Mechanistic study evidenced that leptin treatment increased the AKT/mTOR signaling activity and elevated the expression of leptin receptor (LEPR) in TSPCs, without marked change in MAPK or STAT5 activation. Further, we confirmed that rapamycin treatment, but not AKT inhibition, effectively reduced the leptin-promoted TSPCs senescence. In a rat model with Achilles wounding, exposure to leptin profoundly delayed tendon healing, which was effectively rescued with rapamycin treatment. Our results suggested that leptin could cause intrinsic cellular deficits in TSPCs and impede tendon repair through the AKT/mTOR signaling pathway. These findings evidenced for an important role of elevated leptin levels in the care of tendinopathy and tendon tears.

Regenerative Aesthetics: A Genuine Frontier or Just a Facet of Regenerative Medicine: A Systematic Review

BACKGROUND

Regenerative aesthetics claims to enhance cosmetic outcomes through advanced biological interventions like Stem cell and Exosome therapy, Polydeoxyribonucleotide (PDRN), Photobiomodulation, bioactive peptides and treatment for cellular senescence yet lacks substantial scientific and regulatory validation.

OBJECTIVE

To evaluate the scientific and clinical foundations of regenerative medicine techniques in non-surgical aesthetics and assess the legitimacy of regenerative aesthetics as a medical specialty.

METHODS

A systematic review was conducted according to PRISMA guidelines, searching databases including PubMed, Scopus, and Web of Science for studies published in the last ten years. We included 19 studies, comprising 14 randomized controlled trials (RCTs) and 5 prospective studies, focusing on interventions that purportedly use regenerative medicine principles in aesthetic applications.

RESULTS

The review highlights a prevalent gap in molecular and clinical evidence supporting the efficacy and safety of regenerative aesthetics. Despite the robust design of the included RCTs and prospective studies, there remains a significant lack of consistent, high-quality evidence proving the effectiveness of these interventions. Issues such as inadequate reporting, unclear molecular mechanisms, and absence of long-term safety data were common.

CONCLUSION

The field of regenerative aesthetics lacks the necessary scientific rigour and regulatory compliance to be recognized as a legitimate medical specialty. This review underscores the need for stringent scientific validation and regulatory oversight to ensure patient safety and treatment efficacy before these techniques can be recommended for clinical use.

LEVEL OF EVIDENCE II

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Role of tendon-derived stem cells in tendon and ligament repair: focus on tissue engineer

This review offered a comprehensive analysis of tendon and ligament injuries, emphasizing the crucial role of tendon-derived stem cells (TDSCs) in tissue engineering as a potential solution for these challenging medical conditions. Tendon and ligament injuries, prevalent among athletes, the elderly, and laborers, often result in long-term disability and reduced quality of life due to the poor intrinsic healing capacity of these avascular structures. The formation of biomechanically inferior scar tissue and a high rate of reinjury underscore the need for innovative approaches to enhance and guide the regenerative process. This review delved into the complexities of tendon and ligament structure and function, types of injuries and their impacts, and the limitations of the natural repair process. It particularly focused on the role of TDSCs within the context of tissue engineering. TDSCs, with their ability to differentiate into tenocytes, are explored in various applications, including biocompatible scaffolds for cell tracking, co-culture systems to optimize tendon-bone healing, and graft healing techniques. The review also addressed the challenges of immunoreactivity post-transplantation, the importance of pre-treating TDSCs, and the potential of hydrogels and decellularized matrices in supporting tendon regeneration. It concluded by highlighting the essential roles of mechanical and molecular stimuli in TDSC differentiation and the current challenges in the field, paving the way for future research directions.

Global research trends and hotspots on tendon-derived stem cell: a bibliometric visualization study

Purpose: This study was aimed to examine the global research status and current research hotspots in the field of tendon stem cells. Methods: Bibliometric methods were employed to retrieve relevant data from the Web of Science Core Collection (WOSCC) database. Additionally, Citespace, Vosviewer, SCImago, and Graphad Prism were utilized to analyze the publication status in this field, identify the current research hotspots, and present a mini-review. Results: The most active countries in this field were China and the United States. Notable authors contributing significantly to this research included Lui Pauline Po Yee, Tang Kanglai, Zhang Jianying, Yin Zi, and Chen Xiao, predominantly affiliated with institutions such as the Hong Kong Hospital Authority, Third Military Medical University, University of Pittsburgh, and Zhejiang University. The most commonly published journals in this field were Stem Cells International, Journal of Orthopedic Research, and Stem Cell Research and Therapy. Moreover, the current research hotspots primarily revolved around scaffolds, molecular mechanisms, and inflammation regulation. Conclusion: Tendon stem cells hold significant potential as seed cells for tendon tissue engineering and offer promising avenues for further research Scaffolds, molecular mechanisms and inflammation regulation are currently research hotspots in this field.

A Novel Multi-compartment Rotating Bioreactor for Improving ADSC-Spheroid Formation and its Application in Neurogenic Erectile Dysfunction

OBJECTIVE

The aim of this study was to construct a multicompartment synchronous rotating bioreactor (MCSRB) for batch-production of homogenized adipose-derived stem cell (ADSC) microspheres and treat neurogenic erectile dysfunction (ED).

METHODS

Firstly, an MCSRB was constructed using a centrifugal device and hinged trays. Secondly, influence factors (density, rotational speed) on the formation of ADSC-spheroids were explored. Finally, a neurogenic ED model was established to verify the effectiveness and safety of ADSC-spheroids for ED treatment.

RESULTS

An MCSRB promoted ADSCs to gather microspheres, most of which were 90-130 μm in diameter. Supernatant from three-dimensional culture led to a significant increase in cytokine expression in ADSCs and migration rate in human umbilical vein endothelial cells (HUVECs) compared to control groups. The erectile function and pathological changes of the penis were improved in the ADSC-spheroids treatment group compared to the traditional ADSCs treatment group (p < 0.01).

CONCLUSION

Efficient, batch, controlled and homogenized production of ADSC stem cell microspheres, and effective improvement of erectile dysfunction in neurogenic rats can be achieved using the MCSRB device.

The Functions and Mechanisms of Tendon Stem/Progenitor Cells in Tendon Healing

Tendon injury is one of the prevalent disorders of the musculoskeletal system in orthopedics and is characterized by pain and limitation of joint function. Due to the difficulty of spontaneous tendon healing, and the scar tissue and low mechanical properties that usually develops after healing. Therefore, the healing of tendon injury remains a clinical challenge. Although there are a multitude of approaches to treating tendon injury, the therapeutic effects have not been satisfactory to date. Recent studies have shown that stem cell therapy has a facilitative effect on tendon healing. In particular, tendon stem/progenitor cells (TSPCs), a type of stem cell from tendon tissue, play an important role not only in tendon development and tendon homeostasis, but also in tendon healing. Compared to other stem cells, TSPCs have the potential to spontaneously differentiate into tenocytes and express higher levels of tendon-related genes. TSPCs promote tendon healing by three mechanisms: modulating the inflammatory response, promoting tenocyte proliferation, and accelerating collagen production and balancing extracellular matrix remodeling. However, current investigations have shown that TSPCs also have a negative effect on tendon healing. For example, misdifferentiation of TSPCs leads to a "failed healing response," which in turn leads to the development of chronic tendon injury (tendinopathy). The focus of this paper is to describe the characteristics of TSPCs and tenocytes, to demonstrate the roles of TSPCs in tendon healing, while discussing the approaches used to culture and differentiate TSPCs. In addition, the limitations of TSPCs in clinical application and their potential therapeutic strategies are elucidated.

Allogenic Synovia-Derived Mesenchymal Stem Cells for Treatment of Equine Tendinopathies and Desmopathies-Proof of Concept

Tendon and ligament injuries are frequent in sport horses and humans, and such injuries represent a significant therapeutic challenge. Tissue regeneration and function recovery are the paramount goals of tendon and ligament lesion management. Nowadays, several regenerative treatments are being developed, based on the use of stem cell and stem cell-based therapies. In the present study, the preparation of equine synovial membrane mesenchymal stem cells (eSM-MSCs) is described for clinical use, collection, transport, isolation, differentiation, characterization, and application. These cells are fibroblast-like and grow in clusters. They retain osteogenic, chondrogenic, and adipogenic differentiation potential. We present 16 clinical cases of tendonitis and desmitis, treated with allogenic eSM-MSCs and autologous serum, and we also include their evaluation, treatment, and follow-up. The concerns associated with the use of autologous serum as a vehicle are related to a reduced immunogenic response after the administration of this therapeutic combination, as well as the pro-regenerative effects from the growth factors and immunoglobulins that are part of its constitution. Most of the cases (14/16) healed in 30 days and presented good outcomes. Treatment of tendon and ligament lesions with a mixture of eSM-MSCs and autologous serum appears to be a promising clinical option for this category of lesions in equine patients.

Writing 3D In Vitro Models of Human Tendon within a Biomimetic Fibrillar Support Platform

Tendinopathies are poorly understood diseases for which treatment remains challenging. Relevant in vitro models to study human tendon physiology and pathophysiology are therefore highly needed. Here we propose the automated 3D writing of tendon microphysiological systems (MPSs) embedded in a biomimetic fibrillar support platform based on cellulose nanocrystals (CNCs) self-assembly. Tendon decellularized extracellular matrix (dECM) was used to formulate bioinks that closely recapitulate the biochemical signature of tendon niche. A monoculture system recreating the cellular patterns and phenotype of the tendon core was first developed and characterized. This system was then incorporated with a vascular compartment to study the crosstalk between the two cell populations. The combined biophysical and biochemical cues of the printed pattern and dECM hydrogel were revealed to be effective in inducing human-adipose-derived stem cells (hASCs) differentiation toward the tenogenic lineage. In the multicellular system, chemotactic effects promoted endothelial cells migration toward the direction of the tendon core compartment, while the established cellular crosstalk boosted hASCs tenogenesis, emulating the tendon development stages. Overall, the proposed concept is a promising strategy for the automated fabrication of humanized organotypic tendon-on-chip models that will be a valuable new tool for the study of tendon physiology and pathogenesis mechanisms and for testing new tendinopathy treatments.