Impact of aging on the regenerative properties of bone marrow-, muscle-, and adipose-derived mesenchymal stem/stromal cells

Clinical challenges in bone tissue engineering - A narrative review

Bone tissue engineering (BTE) has emerged as a promising approach to address large bone defects caused by trauma, infections, congenital malformations, and tumors. This review focuses on scaffold design, cell sources, growth factors, and vascularization strategies, highlighting their roles in developing effective treatments. We explore the complexities of balancing mechanical properties, porosity, and biocompatibility in scaffold materials, alongside optimizing mesenchymal stem cell delivery methods. The critical role of growth factors in bone regeneration and the need for controlled release systems are discussed. Vascularization remains a significant hurdle, with strategies such as angiogenic factors, co-culture systems, and bioprinting under investigation. Mechanical challenges, tissue responses, and inflammation management are examined, alongside gene therapy's potential for enhancing osteogenesis and angiogenesis via both viral and non-viral delivery methods. The review emphasizes the impact of patient-specific factors on bone healing outcomes and the importance of personalized approaches. Future directions are described, emphasizing the necessity of interdisciplinary cooperation to advance the field of BTE and convert laboratory results into clinically feasible solutions.

Regional Gene Therapy for Bone Tissue Engineering: A Current Concepts Review

The management of segmental bone defects presents a complex reconstruction challenge for orthopedic surgeons. Current treatment options are limited by efficacy across the spectrum of injury, morbidity, and cost. Regional gene therapy is a promising tissue engineering strategy for bone repair, as it allows for local implantation of nucleic acids or genetically modified cells to direct specific protein expression. In cell-based gene therapy approaches, a variety of different cell types have been described including mesenchymal stem cells (MSCs) derived from multiple sources-bone marrow, adipose, skeletal muscle, and umbilical cord tissue, among others. MSCs, in particular, have been well studied, as they serve as a source of osteoprogenitor cells in addition to providing a vehicle for transgene delivery. Furthermore, MSCs possess immunomodulatory properties, which may support the development of an allogeneic "off-the-shelf" gene therapy product. Identifying an optimal cell type is paramount to the successful clinical translation of cell-based gene therapy approaches. Here, we review current strategies for the management of segmental bone loss in orthopedic surgery, including bone grafting, bone graft substitutes, and operative techniques. We also highlight regional gene therapy as a tissue engineering strategy for bone repair, with a focus on cell types and cell sources suitable for this application.

Exosome Source Matters: A Comprehensive Review from the Perspective of Diverse Cellular Origins

Exosomes have emerged as promising therapeutic agents in regenerative medicine. This review introduces a novel cell type-oriented perspective to systematically analyze exosomal properties in regenerative therapies. To our knowledge, this review is the first to comprehensively compare exosomes based on cellular source type, offering unprecedented insights into selecting optimal exosome producers for targeted regenerative applications. Factors beyond cellular origin influencing exosomal therapeutic efficacy, such as donor sites and collection methods, are also explored here. By synthesizing key advances, we propose promising research directions in the end. We aim to accelerate the development of more effective exosome-based regenerative therapies and highlight underexplored directions in this rapidly evolving field.

The limelight of adipose-derived stem cells in the landscape of neural tissue engineering for peripheral nerve injury

BACKGROUND AND AIMS

Challenges in treating peripheral nerve injury include prolonged repair time and insufficient functional recovery. Stem cell therapy coupled with neural tissue engineering has been shown to induce nerve regeneration following peripheral nerve injury. Among these stem cells, adipose-derived stem cells (ADSCs) are preferred due to their accessibility, expansion, multidirectional differentiation, and production of essential nutrient factors for nerve growth. In recent years, ADSC-laden nerve guide conduit has been utilized to enhance the therapeutic effects of tissue-engineered nerve grafts. This review explores existing research that recognizes the roles played by ADSCs in inducing peripheral nerve regeneration following injury and summarizes the different methods of application of ADSC-laden nerve conduit in neural tissue engineering.

Tailoring surface stiffness to modulate senescent macrophage immunomodulation: Implications for osteo-/angio-genesis in aged bone regeneration

The application of biomaterials in bone regeneration is a prevalent clinical practice. However, its efficacy in elderly patients remains suboptimal, necessitating further advancements. While biomaterial properties are known to orchestrate macrophage (MΦ) polarization and local immune responses, the role of biomaterial cues, specifically stiffness, in directing the senescent macrophage (S-MΦ) is still poorly understood. This study aimed to elucidate the role of substrate stiffness in modulating the immunomodulatory properties of S-MΦ and their role in osteo-immunomodulation. Our results demonstrated that employing collagen-coated polyacrylamide hydrogels with varying stiffness values (18, 76, and 295 kPa) as model materials, the high-stiffness hydrogel (295 kPa) steered S-MΦs towards a pro-inflammatory M1 phenotype, while hydrogels with lower stiffness (18 and 76 kPa) promoted an anti-inflammatory M2 phenotype. The immune microenvironment created by S-MΦs promoted the bioactivities of senescent endothelial cells (S-ECs) and senescent bone marrow mesenchymal stem cells BMSCs (S-BMSCs). Furthermore, the M2 S-MΦs, particularly incubated on the 76 kPa hydrogel matrices, significantly enhanced the ability of angiogenesis of S-ECs and osteogenic differentiation of S-BMSCs, which are crucial and interrelated processes in bone healing. This modulation aided in reducing the accumulation of reactive oxygen species in S-ECs and S-BMSCs, thereby significantly contributing to the repair and regeneration of aged bone tissue.

Acquisition of durable insulin-producing cells from human adipose tissue-derived mesenchymal stem cells as a foundation for cell- based therapy of diabetes mellitus

This study aimed to identify the suitable induction protocol to produce highly qualified insulin producing cells (IPCs) from human adipose tissue derived stem cells (ADSCs) and evaluate the efficacy of the most functionally IPCs in management of diabetes mellitus (DM) in rats. The ADSCs were isolated and characterized according to the standard guidelines. ADSCs were further induced to be IPCs in vitro using three different protocols. The success of trans-differentiation was assessed in vitro through analysis of pancreatic endocrine genes expression, and insulin release in response to glucose stimulation. Then, the functionalization of the generated IPCs was evaluated in vivo. The in vitro findings revealed that the laminin-coated plates in combination with insulin-transferrin-selenium, B27, N2, and nicotinamide could efficiently up-regulate the expression of pancreatic endocrine genes. The in vivo study indicated effectual homing of the PKH-26-labelled IPCs in the pancreas of treated animals. Moreover, IPCs infusion in diabetic rats induced significant improvement in the metabolic parameters and prompted considerable up-regulation in the expression of the pancreatic related genes. The regenerative effect of infused IPCs was determined through histological examination of pancreatic tissue. Conclusively, the utilization of laminin-coated plates in concomitant with extrinsic factors promoting proliferation and differentiation of ADSCs could efficiently generate functional IPCs.

Deciphering Osteosarcopenia through the hallmarks of aging

Osteosarcopenia is a major driver of functional loss and a risk factor for falls, fractures, disability and mortality in older adults, urgently requiring the development of effective interventions to address it. The hallmarks of aging provide a theoretical and practical framework that allows for the structured organization of current knowledge and the planning of new development lines. This article comprehensively reviews the currently available literature on the role of the hallmarks of aging in the development of osteosarcopenia, thereby offering a panoramic view of the state of the art and knowledge gaps in this field.

SCD2 Regulation Targeted by miR-200c-3p on Lipogenesis Alleviates Mesenchymal Stromal Cell Senescence

The senescence of bone marrow mesenchymal stromal cells (MSCs) leads to the impairment of stemness and osteogenic differentiation capacity. In a previous study, we screened out stearoyl-CoA desaturase 2 (SCD2), the most evidently changed differential gene in lipid metabolism, using combined transcriptomic and metabolomic analyses, and verified that SCD2 could mitigate MSC senescence. However, the underlying molecular mechanism by which the rate-limiting enzyme of lipogenesis SCD2 manipulates MSC senescence has not been completely understood. In this study, we demonstrate that SCD2 over-expression alleviates MSC replicative senescence and ameliorates their osteogenic differentiation through the regulation of lipogenesis. Furthermore, SCD2 expression is reduced, whereas miR-200c-3p expression is elevated in replicative senescent MSCs. SCD2 is the direct target gene of miR-200c-3p, which can bind to the 3'-UTR of SCD2. MiR-200c-3p replenishment in young MSCs is able to diminish SCD2 expression levels due to epigenetic modulation. In addition, SCD2-rescued MSC senescence and enhanced osteogenic differentiation can be attenuated by miR-200c-3p repletion via suppressing lipogenesis. Taken together, we reveal the potential mechanism of SCD2 influencing MSC senescence from the perspective of lipid metabolism and epigenetics, which provides both an experimental basis for elucidating the mechanism of stem cell senescence and a novel target for delaying stem cell senescence.

Seven-Year Longitudinal Study: Clinical Evaluation of Knee Osteoarthritic Patients Treated with Mesenchymal Stem Cells

Background/Objectives: Numerous studies have demonstrated the safety and efficacy of intraarticular stem cell injections for treating osteoarthritic knee joints, reporting symptom reduction and pain relief within a few months of treatment. Here, we report the results of a 7-year follow-up after a single intraarticular injection of 0.5-1 × 107 autologous adipose tissue-derived mesenchymal stem cells in patients with OA (Kellgren-Lawrence grade 2 to 4). Methods: Nine patients were treated, and two patients had bilateral disease. Patients were evaluated clinically and radiologically using X-ray and MRI. A comprehensive statistical analysis was undertaken to evaluate the obtained results. Results: All clinical scores and range of motion significantly improved within the first six months after injection. At the 18-month time point, a significant improvement in cartilage structure was observed on MRI while X-ray showed no changes in subchondral bone of distal femur and proximal tibia. At the 60-month time point, the clinical scores were still improved compared to baseline, except for the range of motion, which decreased almost back to the baseline level. At 84 months, the clinical scores decreased significantly toward the baseline level, but the MRI structural characteristics of cartilage still remained significantly better than those measured at baseline. Conclusions: Adipose tissue-derived stem cell therapy has substantial long-term clinical effects on patients with knee osteoarthritis.

Adipose-derived stem cell therapy for spinal cord injuries: Advances, challenges, and future directions

Spinal cord injury (SCI) has limited treatment options for regaining function. Adipose-derived stem cells (ADSCs) show promise owing to their ability to differentiate into multiple cell types, promote nerve cell survival, and modulate inflammation. This review explores ADSC therapy for SCI, focusing on its potential for improving function, preclinical and early clinical trial progress, challenges, and future directions. Preclinical studies have demonstrated ADSC transplantation's effectiveness in promoting functional recovery, reducing cavity formation, and enhancing nerve regrowth and myelin repair. To improve ADSC efficacy, strategies including genetic modification and combination with rehabilitation are being explored. Early clinical trials have shown safety and feasibility, with some suggesting motor and sensory function improvements. Challenges remain for clinical translation, including optimizing cell survival and delivery, determining dosing, addressing tumor formation risks, and establishing standardized protocols. Future research should focus on overcoming these challenges and exploring the potential for combining ADSC therapy with other treatments, including rehabilitation and medication.

Aggregation of human osteoblasts unlocks self-reliant differentiation and constitutes a microenvironment for 3D-co-cultivation with other bone marrow cells

Skeletal bone function relies on both cells and cellular niches, which, when combined, provide guiding cues for the control of differentiation and remodeling processes. Here, we propose an in vitro 3D model based on human fetal osteoblasts, which eases the study of osteocyte commitment in vitro and thus provides a means to examine the influences of biomaterials, substances or cells on the regulation of these processes. Aggregates were formed from human fetal osteoblasts (hFOB1.19) and cultivated under proliferative, adipo- and osteoinductive conditions. When cultivated under osteoinductive conditions, the vitality of the aggregates was compromised, the expression levels of the mineralization-related gene DMP1 and the amount of calcification and matrix deposition were lower, and the growth of the spheroids stalled. However, within spheres under growth conditions without specific supplements, self-organization processes occur, which promote extracellular calcium deposition, and osteocyte-like cells develop. Long-term cultivated hFOB aggregates were free of necrotic areas. Moreover, hFOB aggregates cultivated under standard proliferative conditions supported the co-cultivation of human monocytes, microvascular endothelial cells and stromal cells. Overall, the model presented here comprises a self-organizing and easily accessible 3D osteoblast model for studying bone marrow formation and in vitro remodeling and thus provides a means to test druggable molecular pathways with the potential to promote life-long bone formation and remodeling.

Stem Cell and Regenerative Therapies for the Treatment of Osteoporotic Vertebral Compression Fractures

Osteoporotic vertebral compression fractures (OVCFs) significantly increase morbidity and mortality, presenting a formidable challenge in healthcare. Traditional interventions such as vertebroplasty and kyphoplasty, despite their widespread use, are limited in addressing the secondary effects of vertebral fractures in adjacent areas and do not facilitate bone regeneration. This review paper explores the emerging domain of regenerative therapies, spotlighting stem cell therapy's transformative potential in OVCF treatment. It thoroughly describes the therapeutic possibilities and mechanisms of action of mesenchymal stem cells against OVCFs, relying on recent clinical trials and preclinical studies for efficacy assessment. Our findings reveal that stem cell therapy, particularly in combination with scaffolding materials, holds substantial promise for bone regeneration, spinal stability improvement, and pain mitigation. This integration of stem cell-based methods with conventional treatments may herald a new era in OVCF management, potentially improving patient outcomes. This review advocates for accelerated research and collaborative efforts to translate laboratory breakthroughs into clinical practice, emphasizing the revolutionary impact of regenerative therapies on OVCF management. In summary, this paper positions stem cell therapy at the forefront of innovation for OVCF treatment, stressing the importance of ongoing research and cross-disciplinary collaboration to unlock its full clinical potential.

How mesenchymal stem cells transform into adipocytes: Overview of the current understanding of adipogenic differentiation

Mesenchymal stem cells (MSCs) are stem/progenitor cells capable of self-renewal and differentiation into osteoblasts, chondrocytes and adipocytes. The transformation of multipotent MSCs to adipocytes mainly involves two subsequent steps from MSCs to preadipocytes and further preadipocytes into adipocytes, in which the process MSCs are precisely controlled to commit to the adipogenic lineage and then mature into adipocytes. Previous studies have shown that the master transcription factors C/enhancer-binding protein alpha and peroxisome proliferation activator receptor gamma play vital roles in adipogenesis. However, the mechanism underlying the adipogenic differentiation of MSCs is not fully understood. Here, the current knowledge of adipogenic differentiation in MSCs is reviewed, focusing on signaling pathways, noncoding RNAs and epigenetic effects on DNA methylation and acetylation during MSC differentiation. Finally, the relationship between maladipogenic differentiation and diseases is briefly discussed. We hope that this review can broaden and deepen our understanding of how MSCs turn into adipocytes.

Adipose-Derived Stem Cells: Angiogenetic Potential and Utility in Tissue Engineering

Adipose tissue (AT) is a large and important energy storage organ as well as an endocrine organ with a critical role in many processes. Additionally, AT is an enormous and easily accessible source of multipotent cell types used in our day for all types of tissue regeneration. The ability of adipose-derived stem cells (ADSCs) to differentiate into other types of cells, such as endothelial cells (ECs), vascular smooth muscle cells, or cardiomyocytes, is used in tissue engineering in order to promote/stimulate the process of angiogenesis. Being a key for future successful clinical applications, functional vascular networks in engineered tissue are targeted by numerous in vivo and ex vivo studies. The article reviews the angiogenic potential of ADSCs and explores their capacity in the field of tissue engineering (TE).

In Vitro Osteogenesis Study of Shell Nacre Cement with Older and Young Donor Bone Marrow Mesenchymal Stem/Stromal Cells

Bone void-filling cements are one of the preferred materials for managing irregular bone voids, particularly in the geriatric population who undergo many orthopedic surgeries. However, bone marrow mesenchymal stem/stromal cells (BM-MSCs) of older-age donors often exhibit reduced osteogenic capacity. Hence, it is crucial to evaluate candidate bone substitute materials with BM-MSCs from the geriatric population to determine the true osteogenic potential, thus simulating the clinical situation. With this concept, we investigated the osteogenic potential of shell nacre cement (SNC), a bone void-filling cement based on shell nacre powder and ladder-structured siloxane methacrylate, using older donor BM-MSCs (age > 55 years) and young donor BM-MSCs (age < 30 years). Direct and indirect cytotoxicity studies conducted with human BM-MSCs confirmed the non-cytotoxic nature of SNC. The standard colony-forming unit-fibroblast (CFU-F) assay and population doubling (PD) time assays revealed a significant reduction in the proliferation potential (p < 0.0001, p < 0.05) in older donor BM-MSCs compared to young donor BM-MSCs. Correspondingly, older donor BM-MSCs contained higher proportions of senescent, β-galactosidase (SA-β gal)-positive cells (nearly 2-fold, p < 0.001). In contrast, the proliferation capacity of older donor BM-MSCs, measured as the area density of CellTrackerTM green positive cells, was similar to that of young donor BM-MSCs following a 7-day culture on SNC. Furthermore, after 14 days of osteoinduction on SNC, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) showed that the amount of calcium and phosphorus deposited by young and older donor BM-MSCs on SNC was comparable. A similar trend was observed in the expression of the osteogenesis-related genes BMP2, RUNX2, ALP, COL1A1, OMD and SPARC. Overall, the results of this study indicated that SNC would be a promising candidate for managing bone voids in all age groups.

Proliferation and Differentiation Potential of Bone Marrow-Derived Mesenchymal Stem Cells From Children With Polydactyly and Adults With Basal Joint Arthritis

This study compared the proliferation and differentiation potential of bone marrow-derived mesenchymal stem cells (BMSCs) derived from infants with polydactyly and adults with basal joint arthritis. The proliferation rate of adult and infant BMSCs was determined by the cell number changes and doubling times. The γH2AX immunofluorescence staining, age-related gene expression, senescence-associated β-galactosidase (SA-β-gal) staining were analyzed to determine the senescence state of adult and infant BMSCs. The expression levels of superoxide dismutases (SODs) and genes associated with various types of differentiation were measured using Real-Time Quantitative Polymerase Chain Reaction (RT-qPCR). Differentiation levels were evaluated through histochemical and immunohistochemical staining. The results showed that infant BMSCs had a significantly higher increase in cell numbers and faster doubling times compared with adult BMSCs. Infant BMSCs at late stages exhibited reduced γH2AX expression and SA-β-gal staining, indicating lower levels of senescence. The expression levels of senescence-related genes (p16, p21, and p53) in infant BMSCs were also lower than in adult BMSCs. In addition, infant BMSCs demonstrated higher antioxidative ability with elevated expression of SOD1, SOD2, and SOD3 compared with adult BMSCs. In terms of differentiation potential, infant BMSCs outperformed adult BMSCs in chondrogenesis, as indicated by higher expression levels of chondrogenic genes (SOX9, COL2, and COL10) and positive immunohistochemical staining. Moreover, differentiated cells derived from infant BMSCs exhibited significantly higher expression levels of osteogenic, tenogenic, hepatogenic, and neurogenic genes compared with those derived from adult BMSCs. Histochemical and immunofluorescence staining confirmed these findings. However, adult BMSCs showed lower adipogenic differentiation potential compared with infant BMSCs. Overall, infant BMSCs demonstrated superior characteristics, including higher proliferation rates, enhanced antioxidative activity, and greater differentiation potential into various lineages. They also exhibited reduced cellular senescence. These findings, within the context of cellular differentiation, suggest potential implications for the use of allogeneic BMSC transplantation, emphasizing the need for further in vivo investigation.

A Powerful Tool in the Treatment of Myocardial Ischemia-Reperfusion Injury: Natural and Nanoscale Modified Small Extracellular Vesicles Derived from Mesenchymal Stem Cells

Myocardial ischemia-reperfusion injury (MI/RI) constitutes a pivotal determinant impacting the long-term prognosis of individuals afflicted by ischemic cardiomyopathy subsequent to reperfusion therapy. Stem cells have garnered extensive application within the realm of MI/RI investigation, yielding tangible outcomes. Stem cell therapy encounters certain challenges in its application owing to the complexities associated with stem cell acquisition, a diminished homing rate, and a brief in vivo lifespan. Small extracellular vesicles (sEV) originating from mesenchymal stem cells (MSCs) have been demonstrated to possess the benefits of abundant availability, reduced immunogenicity, and a diminished tumorigenic incidence. They can exert their effects on damaged organs, improving injuries by transporting a lot of constituents, including proteins, RNA, lipid droplets, and more. This phenomenon has garnered substantial attention in the context of MI/RI treatment. Simultaneously, MSC-derived sEV (MSC-sEV) can exhibit enhanced therapeutic advantages through bioengineering modifications, biomaterial incorporation, and natural drug interventions. Within this discourse, we shall appraise the utilization of MSC-sEV and their derivatives in the context of MI/RI treatment, aiming to offer valuable insights for future research endeavors related to MI/RI.

Age-related changes in human bone marrow mesenchymal stromal cells: morphology, gene expression profile, immunomodulatory activity and miRNA expression

Introduction

Mesenchymal stromal cells (MSC) are one of the main cellular components of bone marrow (BM) microenvironment. MSC play a key role in tissue regeneration, but they are also capable of immunomodulating activity. With host aging, MSC undergo age-related changes, which alter these functions, contributing to the set-up of "inflammaging", which is known to be the basis for the development of several diseases of the elderly, including cancer. However, there's few data investigating this facet of MSC, mainly obtained using murine models or replicative senescence. The aim of this research was to identify morphological, molecular and functional alterations of human bone marrow-derived MSC from young (yBM-MSC) and old (oBM-MSC) healthy donors.

Methods

MSC were identified by analysis of cell-surface markers according to the ISCT criteria. To evaluate response to inflammatory status, MSC were incubated for 24h in the presence of IL-1β, IFN-α, IFN-ɣ and TNF-α. Macrophages were obtained by differentiation of THP-1 cells through PMA exposure. For M1 polarization experiments, a 24h incubation with LPS and IFN-ɣ was performed. MSC were plated at the bottom of the co-culture transwell system for all the time of cytokine exposure. Gene expression was evaluated by real-time PCR after RNA extraction from BM-MSC or THP-1 culture. Secreted cytokines levels were quantitated through ELISA assays.

Results

Aging MSC display changes in size, morphology and granularity. Higher levels of β-Gal, reactive oxygen species (ROS), IL-6 and IL-8 and impaired colony-forming and cell cycle progression abilities were found in oBM-MSC. Gene expression profile seems to vary according to subjects' age and particularly in oBM-MSC seem to be characterized by an impaired immunomodulating activity, with a reduced inhibition of macrophage M1 status. The comparative analysis of microRNA (miRNA) expression in yBM-MSC and oBM-MSC revealed a significant difference for miRNA known to be involved in macrophage polarization and particularly miR-193b-3p expression is strongly increased after co-culture of macrophages with yBM-MSC.

Conclusion

There are profound differences in terms of morphology, gene and miRNA expression and immunomodulating properties among yBM-MSC and oBM-MSC, supporting the critical role of aging BM microenvironment on senescence, immune-mediated disorders and cancer pathogenesis.

Evaluating the quality of studies reporting on clinical applications of stromal vascular fraction: A systematic review and proposed reporting guidelines (CLINIC-STRA-SVF)

Background

The stromal vascular fraction (SVF) has been widely explored in a number of therapeutic applications in several specialties. Its therapeutic potential is being increasingly demonstrated, although its mechanism of action is still unclear.

Objective

To evaluate the quality of studies reporting on clinical applications of SVF.

Method

This is a systematic literature review that followed the PRISMA guidelines with the search of the studies from December 1, 2012, to December 1, 2022, in the following databases: MEDLINE, LILACS and EMBASE. The level of evidence of the studies was assessed using the GRADE system, and the rigor used in the publication of the results was assessed in relation to adherence to the guidelines indicated by the EQUATOR Network Group. The CLINIC - STRA-SVF reporting guideline was developed after the completion of this systematic review.

Results

A total of 538 articles were found, and 77 articles were selected after reading the titles and abstracts and removing duplicates. Then, 15 studies were removed for not meeting the inclusion criteria, leaving 62 studies. The CLINIC - STRA-SVF was developed and consists of 33 items and two tables.

Conclusion

There is scientific evidence, although mostly with a low level of evidence, that the use of SVF in clinical applications is safe and effective. The information published in these studies should be standardized, and the CLINIC - STRA-SVF reporting guideline proposed in this study may assist in the design, conduct, recording and reporting of clinical trials and others clinical studies involving the SVF.

Mild heat treatment in vitro potentiates human adipose stem cells: delayed aging and improved quality for long term culture

BACKGROUND

Mesenchymal stem cells (MSCs) have gained significant attention for diverse biomedical applications, including cell-based therapy. Hence, in vitro expansion of MSCs is critical; however, in vitro MSC culture, especially long-term culture, inevitably leads to significant loss of stemness, growth, and differentiation potential.

METHOD

Effects of mild heat treatment (HT) conditions (temperature, duration, and repetition) on the characteristics of adipose tissue-derived MSCs in vitro were systematically investigated. Characteristics of the MSCs subjected to the predetermined HT conditions (41 or 44ºC, 1 h, and 2X HT) were first analyzed in a single passage using various assays. In addition, the feasibility of HT for long-term MSC culture was studied. The RNA sequencing analyses were performed to elucidate the mechanism of HT effects on MSCs.

RESULTS

A comprehensive exploration of various HT conditions revealed that specific mild HT at 41ºC or 44ºC for 1 h upregulated the expression of heat shock proteins and stemness markers and enhanced differentiation potentials. Furthermore, periodic mild HT extended the maintenance of growth rate and stemness of MSCs up to an additional 10 passages, which substantially retarded their spontaneous aging during subsequent in vitro culture. RNA sequencing analyses unveiled that HT downregulated genes associated with aging and apoptosis.

CONCLUSION

Our study successfully demonstrated that mild HT of MSCs has positive effects on their application in various biomedical fields, enhancing their capabilities and slowing down the aging process.

Mesenchymal Stromal Cell Secretome Is Affected by Tissue Source and Donor Age

Variation in mesenchymal stromal cell (MSC) function depending on their origin is problematic, as it may confound clinical outcomes of MSC therapy. Current evidence suggests that the therapeutic benefits of MSCs are attributed to secretion of biologically active factors (secretome). However, the effect of donor characteristics on the MSC secretome remains largely unknown. Here, we examined the influence of donor age, sex, and tissue source, on the protein profile of the equine MSC secretome. We used dynamic metabolic labeling with stable isotopes combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify secreted proteins in MSC conditioned media (CM). Seventy proteins were classified as classically secreted based on the rate of label incorporation into newly synthesized proteins released into the extracellular space. Next, we analyzed CM of bone marrow- (n = 14) and adipose-derived MSCs (n = 16) with label-free LC-MS/MS. Clustering analysis of 314 proteins detected across all samples identified tissue source as the main factor driving variability in MSC CM proteomes. Linear modelling applied to the subset of 70 secreted proteins identified tissue-related difference in the abundance of 23 proteins. There was an age-related decrease in the abundance of CTHRC1 and LOX, further validated with orthogonal techniques. Due to the lack of flow cytometry characterization of MSC surface markers, the analysis could not account for the potential effect of cell population heterogeneity. This study provides evidence that tissue source and donor age contribute to differences in the protein composition of MSC secretomes which may influence the effects of MSC therapy.

Stem Cell-Based Therapy and Cell-Free Therapy as an Alternative Approach for Cardiac Regeneration

The World Health Organization reports that cardiovascular diseases (CVDs) represent 32% of all global deaths. The ineffectiveness of conventional therapies in CVDs encourages the development of novel, minimally invasive therapeutic strategies for the healing and regeneration of damaged tissue. The self-renewal capacity, multilineage differentiation, lack of immunogenicity, and immunosuppressive properties of mesenchymal stem cells (MSCs) make them a promising option for CVDs. However, growing evidence suggests that myocardial regeneration occurs through paracrine factors and extracellular vesicle (EV) secretion, rather than through differentiation into cardiomyocytes. Research shows that stem cells secrete or surface-shed into their culture media various cytokines, chemokines, growth factors, anti-inflammatory factors, and EVs, which constitute an MSC-conditioned medium (MSC-CM) or the secretome. The use of MSC-CM enhances cardiac repair through resident heart cell differentiation, proliferation, scar mass reduction, a decrease in infarct wall thickness, and cardiac function improvement comparable to MSCs without their side effects. This review highlights the limitations and benefits of therapies based on stem cells and their secretome as an innovative treatment of CVDs.

Human Mesenchymal Stem Cells and Innovative Scaffolds for Bone Tissue Engineering Applications

Stem cell-based therapy is a significant topic in regenerative medicine, with a predominant role being played by human mesenchymal stem cells (hMSCs). The hMSCs have been shown to be suitable in regenerative medicine for the treatment of bone tissue. In the last few years, the average lifespan of our population has gradually increased. The need of biocompatible materials, which exhibit high performances, such as efficiency in bone regeneration, has been highlighted by aging. Current studies emphasize the benefit of using biomimetic biomaterials, also known as scaffolds, for bone grafts to speed up bone repair at the fracture site. For the healing of injured bone and bone regeneration, regenerative medicine techniques utilizing a combination of these biomaterials, together with cells and bioactive substances, have drawn a great interest. Cell therapy, based on the use of hMSCs, alongside materials for the healing of damaged bone, has obtained promising results. In this work, several aspects of cell biology, tissue engineering, and biomaterials applied to bone healing/regrowth will be considered. In addition, the role of hMSCs in these fields and recent progress in clinical applications are discussed. Impact Statement The restoration of large bone defects is both a challenging clinical issue and a socioeconomic problem on a global scale. Different therapeutic approaches have been proposed for human mesenchymal stem cells (hMSCs), considering their paracrine effect and potential differentiation into osteoblasts. However, different limitations are still to be overcome in using hMSCs as a therapeutic opportunity in bone fracture repair, including hMSC administration methods. To identify a suitable hMSC delivery system, new strategies have been proposed using innovative biomaterials. This review provides an update of the literature on hMSC/scaffold clinical applications for the management of bone fractures.

Senescence of bone marrow mesenchymal stem cells in Wistar male rats receiving normal chow/high-calorie diets with/without vitamin D

Bone marrow mesenchymal stem cells (BM-MSCs) have a momentous function in the composition of the bone marrow microenvironment because of their many valuable properties and abilities, such as immunomodulation and hematopoiesis. The features and actions of MSCs are influenced by senescence, which may be affected by various factors such as nutritional/micronutrients status, e.g., vitamin D. This study aimed to examine the effects of a high-calorie diet (HCD) with/without vitamin D on BM-MSCs senescence. In the first phase, 48 middle-aged rats were fed a normal chow diet (NCD, n = 24) and an HCD (n = 24) for 26 weeks. Afterward, the rats in each group were randomly divided into three equal subgroups. Immediately, eight-rat from each diet group were sacrificed to assess the HCD effects on the first phase measurements. In the second phase, the remaining 4 groups of rats were fed either NCD or HCD with (6 IU/g) or without vitamin D (standard intake: 1 IU/g); in other words, in this phase, the animals were fed (a) NCD, (b) NCD plus vitamin D, (c) HCD, and (d) HCD plus vitamin D for 4 months. BM-MSCs were isolated and evaluated for P16INK4a, P38 MAPK, and Bmi-1 gene expression, reactive oxygen species (ROS) levels, SA-β-gal activity, and cell cycle profile at the end of both phases. After 26 weeks (first phase), the ROS level, SA-β-gal-positive cells, and cells in the G1 phase were significantly higher in HCD-fed rats than in NCD-fed ones (P < 0.05). HCD prescription did not significantly affect cells in the S and G2 phases (p > 0.05). Compared with the NCD-fed animals, P16INK4a and P38 MAPK gene expression were up-regulated in the HCD-fed animals; also, Bmi-1 gene expression was down-regulated (P < 0.05). BM-MSCs from vitamin D-treated rats (second phase) exhibited reduced mRNA levels of P16INK4a and P38 MAPK genes and increased Bmi-1 mRNA levels (all P < 0.05). Vitamin D prescription also declined the percentage of SA-β-gal-positive cells, ROS levels, and the cells in the G1 phase and increased the cells in the S phase in both NCD and HCD-fed animals (P < 0.05). The reduction of the cells in the G2 phase in rats fed with an NCD plus vitamin D was statistically non-significant (P = 0.128) and significant in HCD plus vitamin D rats (P = 0.002). HCD accelerates BM-MSCs senescence, and vitamin D reduces BM-MSCs senescence biomarkers.

Does Adjunction of Autologous Osteoblastic Cells Improve the Results of Core Decompression in Early-stage Femoral Head Osteonecrosis? A Double-blind, Randomized Trial

BACKGROUND

Osteonecrosis of the femoral head (ONFH) is a disabling disease that can ultimately progress to collapse of the femoral head, often resulting in THA. Core decompression of the femoral head combined with cell therapies have shown beneficial effects in previous clinical studies in patients with early-stage (Association Research Circulation Osseous [ARCO] Stage I and II) ONFH. However, high-quality evidence confirming the efficacy of this treatment modality is still lacking.

QUESTIONS/PURPOSES

(1) Is core decompression combined with autologous osteoblastic cell transplantation superior to core decompression with placebo implantation in relieving disease-associated pain and preventing radiologic ONFH progression in patients with nontraumatic early-stage ONFH? (2) What adverse events occurred in the treatment and control groups?

METHODS

This study was a Phase III, multicenter, randomized, double-blind, controlled study conducted from 2011 to 2019 (ClinicalTrails.gov registry number: NCT01529008). Adult patients with ARCO Stage I and II ONFH were randomized (1:1) to receive either core decompression with osteoblastic cell transplantation (5 mL with 20 x 10 6 cells/mL in the study group) or core decompression with placebo (5 mL of solution without cells in the control group) implantation. Thirty percent (68 of 230) of the screened patients were eligible for inclusion in the study; of these, 94% (64 of 68) underwent a bone marrow harvest or sham procedure (extended safety set) and 79% (54 of 68) were treated (study group: 25 patients; control group: 29). Forty-nine patients were included in the efficacy analyses. Similar proportions of patients in each group completed the study at 24 months of follow-up (study group: 44% [11 of 25]; control: 41% [12 of 29]). The study and control groups were comparable in important ways; for example, in the study and control groups, most patients were men (79% [27 of 34] and 87% [26 of 30], respectively) and had ARCO Stage II ONFH (76% [19 of 25] and 83% [24 of 29], respectively); the mean age was 46 and 45 years in the study and control groups, respectively. The follow-up period was 24 months post-treatment. The primary efficacy endpoint was the composite treatment response at 24 months, comprising the clinical response (clinically important improvement in pain from baseline using the WOMAC VA3.1 pain subscale, defined as 10 mm on a 100-mm scale) and radiologic response (the absence of progression to fracture stage [≥ ARCO Stage III], as assessed by conventional radiography and MRI of the hips). Secondary efficacy endpoints included the percentages of patients achieving a composite treatment response, clinical response, and radiologic response at 12 months, and the percentage of patients undergoing THA at 24 months. We maintained a continuous reporting system for adverse events and serious adverse events related to the study treatment, bone marrow aspiration and sham procedure, or other study procedures throughout the study. A planned, unblinded interim analysis of efficacy and adverse events was completed at 12 months. The study was discontinued because our data safety monitoring board recommended terminating the study for futility based on preselected futility stopping rules: conditional power below 0.20 and p = 0.01 to detect an effect size of 10 mm on the 100-mm WOMAC VA3.1 pain subscale (improvement in pain) and the absence of progression to fracture (≥ ARCO Stage III) observed on radiologic assessment, reflecting the unlikelihood that statistically beneficial results would be reached at 24 months after the treatment.

RESULTS

There was no difference between the study and control groups in the proportion of patients who achieved a composite treatment response at 24 months (61% [14 of 23] versus 69% [18 of 26]; p = 0.54). There was no difference in the proportion of patients with a treatment response at 12 months between the study and control groups (14 of 21 versus 15 of 23; p = 0.92), clinical response (17 of 21 versus 16 of 23; p = 0.38), and radiologic response (16 of 21 versus 18 of 23; p = 0.87). With the numbers available, at 24 months, there was no difference in the proportion of patients who underwent THA between the study and control groups (24% [six of 25] versus 14% [four of 29]). There were no serious adverse events related to the study treatment, and only one serious adverse event (procedural pain in the study group) was related to bone marrow aspiration. Nonserious adverse events related to the treatment were rare in the study and control groups (4% [one of 25] versus 14% [four of 29]). Nonserious adverse events related to bone marrow or sham aspiration were reported by 15% (five of 34) of patients in the study group and 7% (two of 30) of patients in the control group.

CONCLUSION

Our study did not show any advantage of autologous osteoblastic cells to improve the results of core decompression in early-stage (precollapse) ONFH. Adverse events related to treatment were rare and generally mild in both groups, although there might have been a potential risk associated with cell expansion. Based on our findings, we do not recommend the combination of osteoblastic cells and core decompression in patients with early-stage ONFH. Further, well-designed studies should be conducted to explore whether other treatment modalities involving a biological approach could improve the overall results of core decompression.

LEVEL OF EVIDENCE

Level II, therapeutic study.

Mesenchymal Stem Cells Inhibit Epithelial-to-Mesenchymal Transition by Modulating the IRE1α Branch of the Endoplasmic Reticulum Stress Response

Background

Idiopathic pulmonary fibrosis (IPF) is the most common idiopathic interstitial lung disease, and it carries a poor prognosis due to a lack of efficient diagnosis methods and treatments. Epithelial-mesenchymal transition (EMT) plays a key role in IPF pathogenesis. Endoplasmic reticulum (ER) stress contributes to fibrosis via EMT-mediated pathways. Mesenchymal stem cell (MSC) transplantation is a promising treatment strategy for pulmonary fibrosis and ameliorates lung fibrosis in animal models via paracrine effects. However, the specific mechanisms underlying the effect of transplanted MSCs are not known. We previously reported that MSCs attenuate endothelial injury by modulating ER stress and endothelial-to-mesenchymal transition. The present study investigated whether modulation of ER stress- and EMT-related pathways plays essential roles in MSC-mediated alleviation of IPF.

Methods and Results

We constructed a A549 cell model of transforming growth factor-β1 (TGF-β1)-induced fibrosis. TGF-β1 was used to induce EMT in A549 cells, and MSC coculture decreased EMT, as indicated by increased E-cadherin levels and decreased vimentin levels. ER stress participated in TGF-β1-induced EMT in A549 cells, and MSCs inhibited the expression of XBP-1s, XBP-1u, and BiP, which was upregulated by TGF-β1. Inhibition of ER stress contributed to MSC-mediated amelioration of EMT in A549 cells, and modulation of the IRE1α-XBP1 branch of the ER stress pathway may have played an important role in this effect. MSC transplantation alleviated bleomycin (BLM)-induced pulmonary fibrosis in mice. MSC treatment decreased the expression of ER stress- and EMT-related genes and proteins, and the most obvious effect of MSC treatment was inhibition of the IRE1α/XBP1 pathway.

Conclusions

The present study demonstrated that MSCs decrease EMT by modulating ER stress and that blockade of the IRE1α-XBP1 pathway may play a critical role in this effect. The current study provides novel insight for the application of MSCs for IPF treatment and elucidates the mechanism underlying the preventive effects of MSCs against pulmonary fibrosis.

Conversion of Unmodified Stem Cells to Pacemaker Cells by Overexpression of Key Developmental Genes

Arrhythmias of the heart are currently treated by implanting electronic pacemakers and defibrillators. Unmodified adipose tissue-derived stem cells (ASCs) have the potential to differentiate into all three germ layers but have not yet been tested for the generation of pacemaker and Purkinje cells. We investigated if-based on overexpression of dominant conduction cell-specific genes in ASCs-biological pacemaker cells could be induced. Here we show that by overexpression of certain genes that are active during the natural development of the conduction system, the differentiation of ASCs to pacemaker and Purkinje-like cells is feasible. Our study revealed that the most effective procedure consisted of short-term upregulation of gene combinations SHOX2-TBX5-HCN2, and to a lesser extent SHOX2-TBX3-HCN2. Single-gene expression protocols were ineffective. Future clinical implantation of such pacemaker and Purkinje cells, derived from unmodified ASCs of the same patient, could open up new horizons for the treatment of arrythmias.

Progress and emerging techniques for biomaterial-based derivation of mesenchymal stem cells (MSCs) from pluripotent stem cells (PSCs)

The use of mesenchymal stem cells (MSCs) for clinical purposes has skyrocketed in the past decade. Their multilineage differentiation potentials and immunomodulatory properties have facilitated the discovery of therapies for various illnesses. MSCs can be isolated from infant and adult tissue sources, which means they are easily available. However, this raises concerns because of the heterogeneity among the various MSC sources, which limits their effective use. Variabilities arise from donor- and tissue-specific differences, such as age, sex, and tissue source. Moreover, adult-sourced MSCs have limited proliferation potentials, which hinders their long-term therapeutic efficacy. These limitations of adult MSCs have prompted researchers to develop a new method for generating MSCs. Pluripotent stem cells (PSCs), such as embryonic stem cells and induced PSCs (iPSCs), can differentiate into various types of cells. Herein, a thorough review of the characteristics, functions, and clinical importance of MSCs is presented. The existing sources of MSCs, including adult- and infant-based sources, are compared. The most recent techniques for deriving MSCs from iPSCs, with a focus on biomaterial-assisted methods in both two- and three-dimensional culture systems, are listed and elaborated. Finally, several opportunities to develop improved methods for efficiently producing MSCs with the aim of advancing their various clinical applications are described.

Bone marrow-derived dedifferentiated fat cells exhibit similar phenotype as bone marrow mesenchymal stem cells with high osteogenic differentiation and bone regeneration ability

BACKGROUND

Mesenchymal stem cells (MSCs) are known to have different differentiation potential depending on the tissue of origin. Dedifferentiated fat cells (DFATs) are MSC-like multipotent cells that can be prepared from mature adipocytes by ceiling culture method. It is still unknown whether DFATs derived from adipocytes in different tissue showed different phenotype and functional properties. In the present study, we prepared bone marrow (BM)-derived DFATs (BM-DFATs), BM-MSCs, subcutaneous (SC) adipose tissue-derived DFATs (SC-DFATs), and adipose tissue-derived stem cells (ASCs) from donor-matched tissue samples. Then, we compared their phenotypes and multilineage differentiation potential in vitro. We also evaluated in vivo bone regeneration ability of these cells using a mouse femoral fracture model.

METHODS

BM-DFATs, SC-DFATs, BM-MSCs, and ASCs were prepared from tissue samples of knee osteoarthritis patients who received total knee arthroplasty. Cell surface antigens, gene expression profile, and in vitro differentiation capacity of these cells were determined. In vivo bone regenerative ability of these cells was evaluated by micro-computed tomography imaging at 28 days after local injection of the cells with peptide hydrogel (PHG) in the femoral fracture model in severe combined immunodeficiency mice.

RESULTS

BM-DFATs were successfully generated at similar efficiency as SC-DFATs. Cell surface antigen and gene expression profiles of BM-DFATs were similar to those of BM-MSCs, whereas these profiles of SC-DFATs were similar to those of ASCs. In vitro differentiation analysis revealed that BM-DFATs and BM-MSCs had higher differentiation tendency toward osteoblasts and lower differentiation tendency toward adipocytes compared to SC-DFATs and ASCs. Transplantation of BM-DFATs and BM-MSCs with PHG enhanced bone mineral density at the injection sites compared to PHG alone in the mouse femoral fracture model.

CONCLUSIONS

We showed that phenotypic characteristics of BM-DFATs were similar to those of BM-MSCs. BM-DFATs exhibited higher osteogenic differentiation potential and bone regenerative ability compared to SC-DFATs and ASCs. These results suggest that BM-DFATs may be suitable sources of cell-based therapies for patients with nonunion bone fracture.

Progression of pre-rheumatoid arthritis to clinical disease of joints: Potential role of mesenchymal stem cells

Rheumatoid arthritis (RA) related autoimmunity is developed at mucosal sites due to the interplay between genetic risk factors and environmental triggers. The pre-RA phase that leads to anti-citrullinated protein antibodies, rheumatoid factor, and other autoantibodies spread in the systemic circulation may not affect articular tissue for years until a mysterious second hit triggers the localization of RA-related autoimmunity in joints. Several players in the joint microenvironment mediate the synovial innate and adaptive immunological processes, eventually leading to clinical synovitis. There still exists a gap in the early phase of RA pathogenesis, i.e., the progression of diseases from the systemic circulation to joints. The lack of better understanding of these events results in the inability to answer questions about why only after a certain point of time the disease appears in joints and why in some cases, it simply remains latent and doesn't affect joints at all. In the current review, we focused on the immunomodulatory and regenerative role of mesenchymal stem cells and associated exosomes in RA pathology. We also highlighted the age-related dysregulations in activities of mesenchymal stem cells and how that might trigger homing of systemic autoimmunity to joints.

Priming with caffeic acid enhances the potential and survival ability of human adipose-derived stem cells to counteract hypoxia

The therapeutic effectiveness of stem cells after transplantation is hampered by the hypoxic milieu of chronic wounds. Prior research has established antioxidant priming as a thorough plan to improve stem cell performance. The purpose of this study was to ascertain how caffeic acid (CA) priming affected the ability of human adipose-derived stem cells (hASCs) to function under hypoxic stress. In order to study the cytoprotective properties of CA, hASCs were primed with CA in CoCl2 hypoxic conditions. Microscopy was used to assess cell morphology, while XTT, Trypan Blue, X-gal, LDH, Live Dead, scratch wound healing, and ROS assays were used to analyze viability, senescence, cell death, proliferation, and reactive oxygen species prevalence in the cells. According to our findings, CA priming enhances hASCs' ability to survive and regenerate in a hypoxic microenvironment more effectively than untreated hASCs. Our in-vitro research suggested that pre-treatment with CA of hASCs could be a unique way to enhance their therapeutic efficacy and ability to survive in hypoxic microenvironments.

Factors Influencing the Yield of Progenitor Cells in Bone Marrow Aspiration Concentrate—A Retrospective Analysis of 58 Patients

This study aims to identify the role of subjective factors (age, sex, and comorbidities) and procedure-specific factors (aspiration volume) in influencing the yield of progenitor cells in bone marrow aspiration concentrate (BMAC) harvested from the iliac crest. A retrospective analysis was conducted on 58 patients (male:female = 31:27; mean age: 52.56 ± 18.14 years) who underwent BMAC therapy between January 2020 and June 2021. The factors analyzed include individual factors such as age, sex, and comorbid conditions, and procedural factors such as aspirate volume. The mononuclear cell (MNC) count and colony-forming unit (CFU) assay were used to assess the yield of progenitors in the aspirate. Pearson’s correlation test was performed for the age, aspirate volume, and outcome parameters, such as MNC and CFU. We used the chi-square test to analyze the role of sex and comorbidities on cellular yield. The mean volume of aspirate used for BMAC therapy was 66.65 (±17.82) mL. The mean MNC count of the BMAC was 19.94 (±16.34) × 106 cells, which formed 11 (±12) CFUs. Evidence of statistically significant positive associations was noted between the CFUs developed from the BMAC and the MNC count within them (r = 0.95, p < 0.001). The sex of the individual did not play any significant role in MNC count (p = 0.092) or CFUs formed (p = 0.448). The age of the individual showed evidence of a statistically significant negative association with the MNC count (r = −0.681, p < 0.001) and CFUs (r = −0.693, p < 0.001), as did the aspiration volume with the MNC count (r = −0.740, p < 0.001) and CFUs (r = −0.629, p < 0.001). We also noted a significant reduction in the MNC count (p = 0.002) and CFUs formed (p = 0.004) when the patients presented comorbidities. Individual factors such as age, comorbid conditions, and procedure factors such as aspirate volume significantly affected the yield of progenitor cells in the BMAC. The sex of the individual did not influence the yield of progenitor cells in BMAC.

C-Phycocyanin Ameliorates the Senescence of Mesenchymal Stem Cells through ZDHHC5-Mediated Autophagy via PI3K/AKT/mTOR Pathway

The senescence of mesenchymal stem cells (MSCs) impairs their regenerative capacity to maintain tissue homeostasis. Numerous studies are focusing on the interventions and mechanisms to attenuate the senescence of MSCs. C-phycocyanin (C-PC) is reported to have multiple functions such as antitumor, antioxidation, anti-inflammation and anti-aging roles, but there is little research about the effects of C-PC on the senescence of MSCs. Here we investigated the roles and mechanism of C-PC on MSCs senescence. In vitro results showed that C-PC could reduce senescence, enhance proliferation, promote the adipogenic and osteogenic differentiation in senescent MSCs induced by oxidative stress. In vivo D-Galactose (D-Gal) induced rats aging models showed C-PC also increased the viability and differentiation of intrinsic senescent bone marrow derived MSCs (BMSCs). Furthermore, C-PC also decreased the levels of oxidative stress markers ROS or MDA, elevated the SOD activity, and increased the anti-inflammatory factors. Proteomic chip analysis showed that C-PC interacted with ZDHHC5, and their interaction was verified by pull down assay. Overexpression of ZDHHC5 aggravated the senescence of MSCs and greatly lessened the beneficial effects of C-PC on senescence. In addition, we found ZDHHC5 regulated autophagy by altering LC3, Beclin1 and PI3K/AKT/mTOR pathway. In summary, our data indicated that C-PC ameliorates the senescence of MSCs through zinc finger Asp-His-His-Cys (DHHC) domain-containing protein 5 (ZDHHC5) mediated autophagy via PI3K/AKT/mTOR pathway. The present study uncovered the key role of autophagy in MSCs senescence and PI3K/AKT/mTOR pathway may be a potential target for anti-senescence studies of MSCs.

Chondrocyte Hypertrophy in Osteoarthritis: Mechanistic Studies and Models for the Identification of New Therapeutic Strategies

Articular cartilage shows limited self-healing ability owing to its low cellularity and avascularity. Untreated cartilage defects display an increased propensity to degenerate, leading to osteoarthritis (OA). During OA progression, articular chondrocytes are subjected to significant alterations in gene expression and phenotype, including a shift towards a hypertrophic-like state (with the expression of collagen type X, matrix metalloproteinases-13, and alkaline phosphatase) analogous to what eventuates during endochondral ossification. Present OA management strategies focus, however, exclusively on cartilage inflammation and degradation. A better understanding of the hypertrophic chondrocyte phenotype in OA might give new insights into its pathogenesis, suggesting potential disease-modifying therapeutic approaches. Recent developments in the field of cellular/molecular biology and tissue engineering proceeded in the direction of contrasting the onset of this hypertrophic phenotype, but knowledge gaps in the cause-effect of these processes are still present. In this review we will highlight the possible advantages and drawbacks of using this approach as a therapeutic strategy while focusing on the experimental models necessary for a better understanding of the phenomenon. Specifically, we will discuss in brief the cellular signaling pathways associated with the onset of a hypertrophic phenotype in chondrocytes during the progression of OA and will analyze in depth the advantages and disadvantages of various models that have been used to mimic it. Afterwards, we will present the strategies developed and proposed to impede chondrocyte hypertrophy and cartilage matrix mineralization/calcification. Finally, we will examine the future perspectives of OA therapeutic strategies.

Mesenchymal Stem Cell Secreted-Extracellular Vesicles are Involved in Chondrocyte Production and Reduce Adipogenesis during Stem Cell Differentiation

Background:

Extracellular vesicles (EVs) are derived from internal cellular compartments, and have potential as a diagnostic and therapeutic tool in degenerative disease associated with aging. Mesenchymal stem cells (MSCs) have become a promising tool for functional EVs production. This study investigated the efficacy of EVs and its effect on differentiation capacity.

Methods:

The characteristics of MSCs were evaluated by flow cytometry and stem cell differentiation analysis, and a production mode of functional EVs was scaled from MSCs. The concentration and size of EVs were quantitated by Nanoparticle Tracking Analysis (NTA). Western blot analysis was used to assess the protein expression of exosome-specific markers. The effects of MSC-derived EVs were assessed by chondrogenic and adipogenic differentiation analyses and histological observation.

Results:

The range of the particle size of adipose-derived stem cells (ADSCs)- and Wharton’s jelly -MSCs-derived EVs were from 130 to 150 nm as measured by NTA, which showed positive expression of exosomal markers. The chondrogenic induction ability was weakened in the absence of EVs in vitro. Interestingly, after EV administration, type II collagen, a major component in the cartilage extracellular matrix, was upregulated compared to the EV-free condition. Moreover, EVs decreased the lipid accumulation rate during adipogenic induction.

Conclusion:

The results indicated that the production model could facilitate production of effective EVs and further demonstrated the role of MSC-derived EVs in cell differentiation. MSC-derived EVs could be successfully used in cell-free therapy to guide chondrogenic differentiation of ADSC for future clinical applications in cartilage regeneration.

Unlocking the Potential of Induced Pluripotent Stem Cells for Wound Healing: The Next Frontier of Regenerative Medicine

Significance: Nonhealing wounds are a significant burden for the health care system all over the world. Existing treatment options are not enough to promote healing, highlighting the urgent need for improved therapies. In addition, the current advancements in tissue-engineered skin constructs and stem cell-based therapies are facing significant hurdles due to the absence of a renewable source of functional cells. Recent Advances: Induced pluripotent stem cell technology (iPSC) is emerging as a novel tool to develop the next generation of personalized medicine for the treatment of chronic wounds. The iPSC provides unlimited access to various skin cells to generate complex personalized three-dimensional skin constructs for disease modeling and autologous grafts. Furthermore, the iPSC-based therapies can target distinct wound healing phases and have shown accelerating wound closure by enhancing angiogenesis, cell migration, tissue regeneration, and modulating inflammation. Critical Issues: Since the last decade, iPSC has been revolutionizing the field of wound healing and skin tissue engineering. Despite the current progress, safety and heterogeneity among iPSC lines are still major hurdles in addition to the lack of large animal studies. These challenges need to be addressed before translating an iPSC-based therapy to the clinic. Future Directions: Future considerations should be given to performing large animal studies to check the safety and efficiency of iPSC-based therapy in a wound healing setup. Furthermore, strategies should be developed to overcome variation between hiPSC lines, develop an efficient manufacturing process for iPSC-derived products, and generate complex skin constructs with vasculature and skin appendages.

Influence of donor age and comorbidities on transduced human adipose-derived stem cell in vitro osteogenic potential

Human adipose-derived mesenchymal stem cells (ASCs) transduced with a lentiviral vector system to express bone morphogenetic protein 2 (LV-BMP-2) have been shown to reliably heal bone defects in animal models. However, the influence of donor characteristics such as age, sex, race, and medical co-morbidities on ASC yield, growth and bone regenerative capacity, while critical to the successful clinical translation of stem cell-based therapies, are not well understood. Human ASCs isolated from the infrapatellar fat pads in 122 ASC donors were evaluated for cell growth characteristics; 44 underwent additional analyses to evaluate in vitro osteogenic potential, with and without LV-BMP-2 transduction. We found that while female donors demonstrated significantly higher cell yield and ASC growth rates, age, race, and the presence of co-morbid conditions were not associated with differences in proliferation. Donor demographics or the presence of comorbidities were not associated with differences in in vitro osteogenic potential or stem cell differentiation, except that transduced ASCs from healthy donors produced more BMP-2 at day 2. Overall, donor age, sex, race, and the presence of co-morbid conditions had a limited influence on cell yield, proliferation, self-renewal capacity, and osteogenic potential for non-transduced and transduced (LV-BMP-2) ASCs. These results suggest that ASCs are a promising resource for both autologous and allogeneic cell-based gene therapy applications.

Strategies to Convert Cells into Hyaline Cartilage: Magic Spells for Adult Stem Cells

Damaged hyaline cartilage gradually decreases joint function and growing pain significantly reduces the quality of a patient's life. The clinically approved procedure of autologous chondrocyte implantation (ACI) for treating knee cartilage lesions has several limits, including the absence of healthy articular cartilage tissues for cell isolation and difficulties related to the chondrocyte expansion in vitro. Today, various ACI modifications are being developed using autologous chondrocytes from alternative sources, such as the auricles, nose and ribs. Adult stem cells from different tissues are also of great interest due to their less traumatic material extraction and their innate abilities of active proliferation and chondrogenic differentiation. According to the different adult stem cell types and their origin, various strategies have been proposed for stem cell expansion and initiation of their chondrogenic differentiation. The current review presents the diversity in developing applied techniques based on autologous adult stem cell differentiation to hyaline cartilage tissue and targeted to articular cartilage damage therapy.

A systematic review of bone marrow stromal cells and periosteum-derived cells for bone regeneration

Bone marrow stromal cells (BMSCs) and periosteum-derived cells (PDCs) represent promising skeletal stem cell sources to treat critical-size bone defects. However, the large number of preclinical tests with a variety of in vivo data complicates the selection of cells for further clinical translation. This systematic review aims to analyze the in vivo bone-forming efficacy of BMSCs- and PDCs-based approaches in all published preclinical experiments until November 2020. For this purpose, four databases (PubMed, Embase, Cochrane Central Register of Controlled Trial, and Web of Science) were searched for eligible literature, which yielded a total of 94 full-text articles for systematic review. This review generated an evidence-based list of BMSC- or PDC-based approaches, which have been evaluated for bone formation in different animal models. Among them, 74 studies were included for pairwise and network meta-analysis. The results revealed that both PDC and BMSC had beneficial bone-forming efficacy compared to bare scaffold. In addition, BMSC- and PDC-based approaches had no significant difference regarding in vivo bone-forming efficacy. However, BMSC-based approach had a higher probability to be ranked better than PDC-based approach. Furthermore, the review discusses (i) the possible risk of bias of the in vivo evaluation of cell-based approaches, (ii) the difficulty in replication of such experiments due to frequent poor reporting of the methods and results, and (iii) the clinical relevance of the currently utilized BMSC- and PDC-based approaches. Systematic review registration: The study was prospectively registered in PROSPERO, Registration No. CRD42021270922.

Inhibiting DNA methylation as a strategy to enhance adipose-derived stem cells differentiation: Focus on the role of Akt/mTOR and Wnt/β-catenin pathways on adipogenesis

Adipose-derived mesenchymal stem cells (ASCs) represent a valid therapeutic option for clinical application in several diseases, due to their ability to repair damaged tissues and to mitigate the inflammatory/immune response. A better understanding of the underlying mechanisms regulating ASC biology might represent the chance to modulate their in vitro characteristics and differentiation potential for regenerative medicine purposes. Herein, we investigated the effects of the demethylating agent 5-azacytidine (5-aza) on proliferation, clonogenicity, migration, adipogenic differentiation and senescence of ASCs, to identify the molecular pathways involved. Through functional assays, we observed a detrimental effect of 5-aza on ASC self-renewal capacity and migration, accompanied by actin cytoskeleton reorganization, with decreased stress fibers. Conversely, 5-aza treatment enhanced ASC adipogenic differentiation, as assessed by lipid accumulation and expression of lineage-specific markers. We analyzed the involvement of the Akt/mTOR, MAPK and Wnt/β-catenin pathways in these processes. Our results indicated impairment of Akt and ERK phosphorylation, potentially explaining the reduced cell proliferation and migration. We observed a 5-aza-mediated inhibition of the Wnt signaling pathway, this potentially explaining the pro-adipogenic effect of the drug. Finally, 5-aza treatment significantly induced ASC senescence, through upregulation of the p53/p21 axis. Our data may have important translational implications, by helping in clarifying the potential risks and advantages of using epigenetic treatment to improve ASC characteristics for cell-based clinical approaches.

Priming with a Combination of FGF2 and HGF Restores the Impaired Osteogenic Differentiation of Adipose-Derived Stem Cells

Classical aging-associated diseases include osteoporosis, diabetes, hypertension, and arthritis. Osteoporosis causes the bone to become brittle, increasing fracture risk. Among the various treatments for fractures, stem cell transplantation is currently in the spotlight. Poor paracrine/differentiation capacity, owing to donor age or clinical history, limits efficacy. Lower levels of fibroblast growth factor 2 (FGF2) and hepatocyte growth factor (HGF) are involved in cell repopulation, angiogenesis, and bone formation in the elderly ADSCs (ADSC-E) than in the young ADSCs (ADSC-Y). Here, we study the effect of FGF2/HGF priming on the osteogenic potential of ADSC-E, determined by calcium deposition in vitro and ectopic bone formation in vivo. Age-induced FGF2/HGF deficiency was confirmed in ADSCs, and their supplementation enhanced the osteogenic differentiation ability of ADSC-E. Priming with FGF2/HGF caused an early shift of expression of osteogenic markers, including Runt-related transcription factor 2 (Runx-2), osterix, and alkaline phosphatase (ALP) during osteogenic differentiation. FGF2/HGF priming also created an environment favorable to osteogenesis by facilitating the secretion of bone morphogenetic protein 2 (BMP-2) and vascular endothelial growth factor (VEGF). Bone tissue of ADSC-E origin was observed in mice transplanted with FGF/HGF-primed ADSC-E. Collectively, FGF2/HGF priming could enhance the bone-forming capacity in ADSC-E. Therefore, growth factor-mediated cellular priming can enhance ADSC differentiation in bone diseases and thus contributes to the increased efficacy in vivo.

Therapeutic Strategy of Mesenchymal-Stem-Cell-Derived Extracellular Vesicles as Regenerative Medicine

Extracellular vesicles (EVs) are lipid bilayer membrane particles that play critical roles in intracellular communication through EV-encapsulated informative content, including proteins, lipids, and nucleic acids. Mesenchymal stem cells (MSCs) are pluripotent stem cells with self-renewal ability derived from bone marrow, fat, umbilical cord, menstruation blood, pulp, etc., which they use to induce tissue regeneration by their direct recruitment into injured tissues, including the heart, liver, lung, kidney, etc., or secreting factors, such as vascular endothelial growth factor or insulin-like growth factor. Recently, MSC-derived EVs have been shown to have regenerative effects against various diseases, partially due to the post-transcriptional regulation of target genes by miRNAs. Furthermore, EVs have garnered attention as novel drug delivery systems, because they can specially encapsulate various target molecules. In this review, we summarize the regenerative effects and molecular mechanisms of MSC-derived EVs.

Osteogenic capacity of mesenchymal stem cells from patients with osteoporotic hip fractures in vivo

PURPOSE

Human mesenchymal stem cells (MSCs) have the ability to differentiate into bone-forming osteoblasts. The aim of this study was to elucidate if MSCs from patients with OP show a senescent phenotype and explore their bone-forming ability in vivo.

MATERIALS AND METHODS

MSCs from patients with OP and controls with osteoarthritis (OA) were implanted into the subcutaneous tissue of immunodeficient mice for histological analysis and expression of human genes by RT-PCR. The expression of senescence-associated phenotype (SASP) genes, as well as p16, p21, and galactosidase, was studied in cultures of MSCs.

RESULTS

In vivo bone formation was evaluated in 103 implants (47 OP, 56 OA). New bone was observed in 45% of the implants with OP cells and 46% of those with OA cells (p = 0.99). The expression of several bone-related genes (collagen, osteocalcin, alkaline phosphatase, sialoprotein) was also similar in both groups. There were no differences between groups in SASP gene expression, p16, and p21 expression, or in senescence-associated galactosidase activity.

CONCLUSION

Senescence markers and the osteogenic capacity in vivo of MSCs from patients with OP are not inferior to that of cells from controls of similar age with OA. This supports the interest of future studies to evaluate the potential use of autologous MSCs from OP patients in bone regeneration procedures.

BMP-2 Induced Signaling Pathways and Phenotypes: Comparisons Between Senescent and Non-senescent Bone Marrow Mesenchymal Stem Cells

The use of BMP-2 in orthopedic surgery is limited by uncertainty surrounding its effects on the differentiation of mesenchymal stem cells (MSCs) and how this is affected by cellular aging. This study compared the effects of recombinant human BMP-2 (rhBMP-2) on osteogenic and adipogenic differentiation between senescent and non-senescent MSCs. Senescent and non-senescent MSCs were cultured in osteogenic and adipogenic differentiation medium containing various concentrations of rhBMP-2. The phenotypes of these cells were compared by performing a calcium assay, adipogenesis assay, staining, real-time PCR, western blotting, and microarray analysis. rhBMP-2 induced osteogenic differentiation to a lesser extent (P < 0.001 and P = 0.005 for alkaline phosphatase activity and Ca²⁺ release) in senescent MSCs regardless of dose-dependent increase in both cells. However, the induction of adipogenic differentiation by rhBMP-2 was comparable between them. There was no difference between these two groups of cells in the adipogenesis assay (P = 0.279) and their expression levels of PPARγ were similar. Several genes such as CHRDL1, NOG, SMAD1, SMAD7, and FST encoding transcription factors were proposed to underlie the different responses of senescent and non-senescent MSCs to rhBMP-2 in microarray analyses. Furthermore, inflammatory, adipogenic, or cell death-related signaling pathways such as NF-kB or p38-MAPK pathways were upregulated by BMP-2 in senescent MSCs, whereas bone forming signaling pathways involving BMP, SMAD, and TGF- ß were upregulated in non-senescent MSCs as expected. This phenomenon explains bone forming dominance by non-senescent MSCs and possible frequent complications such as seroma, osteolysis, or neuritis in senescent MSCs during BMP-2 use in orthopedic surgery.

Efficacy and Safety of Mesenchymal Stem Cell Transplantation in the Treatment of Autoimmune Diseases (Rheumatoid Arthritis, Systemic Lupus Erythematosus, Inflammatory Bowel Disease, Multiple Sclerosis, and Ankylosing Spondylitis): A Systematic Review and Meta-Analysis of Randomized Controlled Trial

Objective

To evaluate the efficacy and safety of mesenchymal stem cell (MSC) transplantation in the treatment of autoimmune diseases.

Methods

The Chinese and English databases were searched for clinical research on the treatment of autoimmune diseases with mesenchymal stem cells. The search time range is from a self-built database to October 1, 2021. Two reviewers independently screened the literature according to the inclusion and exclusion criteria, extracted data, and evaluated the bias of the included studies. RevMan 5.3 analysis software was used for meta-analysis.

Results

A total of 18 RCTs involving 5 autoimmune diseases were included. The 5 autoimmune disease were rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), inflammatory bowel disease, ankylosing spondylitis, and multiple sclerosis. For RA, the current randomized controlled trials (RCTs) still believe that stem cell transplantation may reduce disease activity, improve the clinical symptoms (such as DAS28), and the percentage of CD4+CD 25+Foxp3+Tregs in the response group increased and the percentage of CD4+IL-17A+Th17 cells decreased. The total clinical effective rate of RA is 54%. For SLE, the results showed that mesenchymal stem cell transplantation may improve SLEDAI [-2.18 (-3.62, -0.75), P = 0.003], urine protein [-0.93 (-1.04, -0.81), P < 0.00001], and complement C3 [0.31 (0.19, 0.42), P < 0.00001]. For inflammatory bowel disease, the results showed that mesenchymal stem cell transplantation may improve clinical efficacy [2.50 (1.07, 5.84), P = 0.03]. For ankylosing spondylitis, MSC treatment for 6 months may increase the total effective rate; reduce erythrocyte sedimentation rate, intercellular adhesion molecules, and serum TNF-α; and improve pain and activity. For multiple sclerosis, the current research results are still controversial, so more RCTs are needed to amend or confirm the conclusions. No obvious adverse events of mesenchymal stem cell transplantation were found in all RCTs.

Conclusion

MSCs have a certain effect on different autoimmune diseases, but more RCTs are needed to further modify or confirm the conclusion.

[Research advances on stem cell therapy for diabetic foot wounds]

Diabetic foot wound repair is a challenging issue in clinical practice. Due to the influence of multiple factors including the damage and regeneration failure of local tissue, the impaired pathways of wound repairing through blood vessels and nerve nutrition, and disorders of a variety of cellular factors, traditional treatment methods are often difficult to achieve good therapeutic effects. Stem cells are a type of cells with potentials of multidirectional differentiation, which also possess functions such as regulating immunity and paracrine to facilitate the comprehensive wound repair, so they have promising application prospect at present for the treatment of diabetic foot wounds. Because the relevant parameters of stem cell treatment are in the exploratory phase, there were no standardized data. This paper reviews the application of stem cells in the research of diabetic foot wound treatment over the past 6 years, analyzing and summarizing the contents in focused aspects including the types and sources of stem cells, effects of donor age and gender on stem cells, mode of administration, transplantation survival rate and safety, which may provide a reference for further application of stem cells in the clinical treatment of diabetic foot wound.

Rapid and robust derivation of mesenchymal stem cells from human pluripotent stem cells via temporal induction of neuralized ectoderm

Background

Mesenchymal stem cells (MSCs) are emerging as the mainstay of regenerative medicine because of their ability to differentiate into multiple cell lineages. The infinite proliferative potential of human pluripotent stem cells (PSCs) grants an unlimited supply of MSCs. Despite their great potential in therapeutic applications, several drawbacks have hindered its clinical translation, including limited number of replication, compromised potential and altered function in late passages. The aim of this study is to establish an efficient method for the production of MSCs from pluripotent stem cells for potential clinical application in rare human disease Hutchinson-Gilford progeria syndrome.

Results

We established a robust method allowing rapid derivation of MSCs from both human iPSCs and ESCs via a temporal induction of neural ectoderm in chemically defined media. The iPSC- and ESC-derived MSCs satisfy the standard criteria of surface markers. They exhibited a high tri-lineage differentiation potential with over 90% transcriptional similarity to the primary MSCs derived from bone marrow. To evaluate the potential application of this method in disease modeling, MSCs were generated from iPSCs derived from a patient with Hutchinson-Gilford progeria syndrome (HGPS-MSCs) and from mutation-rectified HGPS-iPSCs (cHGPS-MSCs). HGPS-MSCs manifested accelerated senescence whereas mutation rectification rescued cellular senescence in HGPS-MSCs.

Conclusions

The robust method of MSC derivation from ESCs and iPSCs provides an efficient approach to rapidly generate sufficient MSCs for in vitro disease modeling and clinical applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00753-2.

Research update of adipose tissue-based therapies in regenerative dermatology

Mesenchymal stromal/stem cells (MSCs) have a spontaneous propensity to support tissue homeostasis and regeneration. Among the several sources of MSCs, adipose-derived tissue stem cells (ADSCs) have received major interest due to the higher mesenchymal stem cells concentration, ease, and safety of access. However, since a significant part of the natural capacity of ADSCs to repair damaged tissue is ascribable to their secretory activity that combines mitogenic factors, cytokines, chemokines, lipids, and extracellular matrix components, several studies focused on cell-free strategies. Furthermore, adipose cell-free derivatives are becoming more attractive especially for non-volumizing purposes, such as most dermatological conditions. However, when keratinocytes, fibroblasts, melanocytes, adipocytes, and hair follicle cells might not be locally sourced, graft of materials containing concentrated ADSCs is preferred. The usage of extracellular elements of adipose tissue aims to promote a self-autonomous regenerative microenvironment in the receiving area restoring physiological homeostasis. Hence, ADSCs or their paracrine activity are currently being studied in several dermatological settings including wound healing, skin fibrosis, burn, and aging.The present work analyzing both preclinical and clinical experiences gives an overview of the efficacy of adipose tissue-derivatives like autologous fat, the stromal vascular fraction (SVF), purified ADSCs, secretome and extracellular matrix graft in the field of regenerative medicine for the skin.

Signaling network regulating osteogenesis in mesenchymal stem cells

Osteogenesis is an important developmental event that results in bone formation. Bone forming cells or osteoblasts develop from mesenchymal stem cells (MSCs) through a highly controlled process regulated by several signaling pathways. The osteogenic lineage commitment of MSCs is controlled by cell-cell interactions, paracrine factors, mechanical signals, hormones, and cytokines present in their niche, which activate a plethora of signaling molecules belonging to bone morphogenetic proteins, Wnt, Hedgehog, and Notch signaling. These signaling pathways individually as well as in coordination with other signaling molecules, regulate the osteogenic lineage commitment of MSCs by activating several osteo-lineage specific transcription factors. Here, we discuss the key signaling pathways that regulate osteogenic differentiation of MSCs and the cross-talk between them during osteogenic differentiation. We also discuss how these signaling pathways can be modified for therapy for bone repair and regeneration.