Changes in phenotype and differentiation potential of human mesenchymal stem cells aging in vitro

Human second-trimester fetal liver-derived mesenchymal stromal cells are more effective than adult bone marrow MSCs for their superior growth kinetics, immunomodulatory, and osteogenic potential

BACKGROUND

Mesenchymal stromal cells (MSCs) are promising candidates for cell therapy. Most of the therapeutic applications have used adult bone marrow MSCs, adipose MSCs and perinatal tissue-derived MSCs. Recent evidence suggests that MSCs from mid-gestational fetal tissues are more primitive, grow faster and are biologically more closely related to embryonic stem cells than other sources of MSCs. However, the expression of pluripotency genes raises the question of whether these genes are safe for clinical application. In this study, we demonstrated that second-trimester fetal liver-derived MSCs lack the expression of pluripotent markers and maintain their proliferative and osteogenic differentiation potential beyond passage 12. Compared to other sources, FL-MSCs exhibit characteristics that are promising for use in skeletal regeneration.

METHODS

MSCs were isolated from the second-trimester fetal liver and characterized for surface antigen expression, pluripotency marker expression and multilineage differentiation. The growth kinetics, population doubling, and number of colony-forming units were analyzed at the 3rd, 5th, 8th and 10th passages of FLMSCs and compared with those of BMMSCs. The immunomodulatory properties of FLMSCs were analyzed by a T-cell proliferation assay. The osteogenic differentiation potential of FL-MSCs was assessed at passages 3, 5, 8 and 12 and compared with that of BMMSCs.

RESULTS

We demonstrated that second-trimester fetal liver-derived MSCs exhibited a distinct fibroblast-like spindle-shaped morphology and expressed typical MSC surface antigens. Unlike first-trimester fetal MSCs, second-trimester FL-MSCs did not express pluripotent markers and showed significantly greater self-renewal and proliferative potential at higher passages and a lower apoptotic rate than BM-MSCs. Additionally, the osteogenic differentiation potential of FL-MSCs was 4-6 times greater than that of BM-MSCs at both early and late passages CONCLUSION: Our findings underscore the robust self-renewal and proliferative potential of second-trimester fetal liver-derived MSCs, which notably lack pluripotent markers. The ability of FL-MSCs to sustain osteogenic potential through multiple passages makes them promising candidates for bone tissue engineering and regenerative medicine.

Promotion of quiescence and maintenance of function of mesenchymal stem cells on substrates with surface potential

The widespread use of human mesenchymal stem cells(hMSCs) is impeded by functional loss during prolonged expansion. Although multiple approaches have been attempted to preserve hMSCs stemness, a suitable culture system remains to be modified. The interaction between electrical signals and stem cells is expected to better maintain the function of stem cells. However, it remains unclear whether the surface potential of substrates has the potential to preserve stem cell function during in vitro expansion. In our study, hMSCs cultured on materials with different surface potentials could be induced into a reversible quiescent state, and we demonstrated that quiescent hMSCs could be reactivated and transitioned back into the proliferation cell cycle. hMSCs cultured under appropriate potential displayed superior differentiation and proliferation abilities within the same generation compared to conventional conditions. These findings underscore the importance of surface potential as a critical physical factor regulating hMSCs stemness. Manipulating the surface potential of hMSCs culture substrates holds promise for optimising preservation and culture conditions, thereby enhancing their application in tissue repair and regeneration engineering.

Optimal good manufacturing practice-compliant production of dental follicle stem cell sheet and its application in Sprague-Dawley rat periodontitis

BACKGROUND

Dental follicle stem cell (DFSC) sheets demonstrate strong extracellular secretion capabilities and efficacy in periodontal regeneration. However, existing methods for producing DFSC sheets lack a comprehensive discussion on the most efficient and cost-effective approaches at the good manufacturing practice (GMP) level.

AIM

To investigate the culture condition of GMP-compliant DFSC sheets and to compare the properties of DFSC sheets and cell suspensions.

METHODS

This study explored the optimal conditions for culturing GMP-compliant DFSC sheets, focusing on four key factors: Cell passage, cell concentration, L-ascorbic acid content, and culture duration. We evaluated the characteristics of the cell sheets under varying culture conditions, including cell viability, cell count, appearance, osteogenesis, chondrogenesis, odontogenesis, aging, relative telomere length, and extracellular matrix secretion. A comparison was also made between the periodontal regeneration, osteogenesis, and paracrine capacity of cell sheets cultured under optimal conditions and those of the cell suspensions.

RESULTS

The GMP-compliant DFSC sheets cultured from passage 4 cells exhibited the highest viability (≥ 99%, P < 0.05) and optimal osteogenic differentiation capacity (optical density ≥ 0.126, P < 0.05). When cultured for 10 days, DFSC sheets demonstrated maximal expression of osteogenic, chondrogenic and periostin genes [alkaline phosphatase, Runt-related transcription factor 2, collagen type I, osteopontin, cartilage associated protein, and PERIOSTN (P < 0.001); osteocalcin (P < 0.01)]. Concurrently, they showed the lowest senescent cell count (P < 0.01) with no progression to late-stage senescence. At a seeding density of 2500 cells/cm², GMP-compliant DFSC sheets achieved better osteogenic differentiation (P < 0.01) and maximal osteogenic, chondrogenic and periostin gene expression (P < 0.001), coupled with the highest hydroxyproline secretion (P < 0.001) and moderate sulfated glycosaminoglycan production. No statistically significant difference in senescent cell count was observed compared to DFSC sheets at a seeding density of 5000 cells/cm². Supplementation with 25 μg/mL L-ascorbic acid significantly enhanced osteogenic gene expression (P < 0.001) and elevated hydroxyproline (P < 0.01) and sulfated glycosaminoglycan secretion to high ranges. Compared with the cell suspension, the cell sheet demonstrated improved osteogenic, paracrine, and periodontal regenerative capacities in Sprague-Dawley rats. The optimized DFSC sheets demonstrated significantly higher levels of vascular endothelial growth factor and angiopoietin-1 (P < 0.001) compared to DFSC suspensions, along with enhanced osteogenic induction outcomes (optical density = 0.1333 ± 0.01270 vs 0.1007 ± 0.0005774 in suspensions, P < 0.05). Following implantation into the rat periodontal defect model, micro-computed tomography analysis revealed superior bone regeneration metrics in the cell sheet group compared to both the cell suspension group and control group (percent bone volume, trabecular thickness, trabecular number), while trabecular spacing exhibited an inverse pattern.

CONCLUSION

Optimized DFSC sheets cultured under the identified conditions outperform DFSC suspensions. This study contributes to the industrial-scale production of DFSC sheets and establishes a foundation for cell therapy applications.

Diabetes Mellitus Impairs the Bone Regeneration Capacity of Mesenchymal Stromal Cell-Based Therapy

BACKGROUND

Diabetes mellitus (DM) negatively impacts bone tissue, leading to bone loss and increased fracture risk. Many individuals need additional treatments, and therapy based on mesenchymal stromal cells (MSCs) represents a promising treatment for bone defects in patients with diabetes.

AIMS

The present study explored the effects of interactions between MSCs from normoglycemic (NG-MSCs) and diabetic (DM-MSCs) donors on osteoblast differentiation and the effects of cell therapy using NG-MSCs on bone regeneration in defects created in diabetic rats.

METHODS

After inducing DM with streptozotocin, we evaluated the morphometric parameters of rat femurs and the osteoblast differentiation of MSCs, as well as the effects of the interaction between NG-MSCs and DM-MSCs on their osteoblast differentiation. The efficacy of cell therapy was measured by evaluating the bone repair in calvarial defects of diabetic rats treated with local injections of either NG-MSCs or a vehicle.

RESULTS

DM induced bone loss and impaired the osteoblast differentiation of MSCs, which was partially restored by NG-MSCs, while the bone formation observed in defects treated with NG-MSCs and the vehicle was similar.

CONCLUSION

These results indicate that the beneficial effect of NG-MSCs on DM-MSCs did not translate into enhanced bone repair, mainly due to a hostile environment created by hyperglycemia, which compromised the ability of MSCs to induce bone formation.

Natural bioactive compounds modified with mesenchymal stem cells: new hope for regenerative medicine

Mesenchymal stem cells (MSCs) have the potential to differentiate into various cell types, providing important sources of cells for the development of regenerative medicine. Although MSCs have various advantages, there are also various problems, such as the low survival rate of transplanted cells and poor migration and homing; therefore, determining how to reform MSCs to improve their utilization is particularly important. Although many natural bioactive compounds have shown great potential for improving MSCs, many mechanisms and pathways are involved; however, in the final analysis, natural bioactive compounds promoted MSC proliferation, migration and homing and promoted differentiation and antiaging. This article reviews the regulatory effects of natural bioactive compounds on MSCs to provide new ideas for the therapeutic effects of modified MSCs on diseases.

Determination and validation of design space for mesenchymal stem cell cultivation processes using prediction intervals

In regenerative medicine, mesenchymal stem cells (MSCs) constitute a promising therapeutic route for many diseases. The current quality-by-design guidelines do not clearly define a framework for MSC production. Here, we suggest and experimentally validate a model-based method to determine design spaces (DSs) for MSC cultivation. A kinetic model used in previous work was employed; part of the experimental data was used to re-estimate the maximum specific growth rate in the kinetic model and then calculate the prediction intervals of this parameter. Subsequently, regions of seeding density and harvesting time where both the upper and lower limits of growth predictions met the acceptable number of cells and confluency with given risk levels were defined as DSs. Finally, the established DS was validated with the remaining data; it allowed better predictions of the cell numbers and confluency under specific cultivation conditions and improved the overall robustness of MSC cultivation processes.

Insights into ionic medicine: Cerium reduces the presence of reactive oxygen species and favors osteogenic over adipogenic differentiation in human mesenchymal stromal cells

The guided application of metallic ions in bone tissue engineering (BTE) has recently gained popularity being described as one important example of ionic medicine (IM). BTE aims to enhance osteogenic differentiation of precursor cells like bone-marrow-derived mesenchymal stromal cells (BMSCs) and, by that, regenerate bone tissue. BMSCs however can also differentiate into adipogenic lineage. It is known that elevated levels of reactive oxygen species (ROS) stimulate BMSC towards (undesired) adipogenic differentiation. One ion, that is particularly interesting for application in IM-guided BTE is cerium (Ce) since it acts as a self-regenerating ROS-scavenger and has already been successfully incorporated in biomaterials. Ce has demonstrated pro-osteogenic, anti-adipogenic and anti-oxidative effects before, however, so far, there is no direct comparative study available that analyzes these effects on human BMSCs in one and the same setting. Therefore, in this study, the influence of Ce nitrate (CeN) on the expression of osteogenic, adipogenic and ROS-scavenging genes in BMSCs was evaluated as well as its impact on formation of an osseous extracellular matrix (ECM), lipid formation and physical ROS presence. The presence of CeN improved BMSCs viability, enhanced proliferation, and reduced ROS-levels. Furthermore, CeN suppressed adipogenesis while osteogenic differentiation and the formation and maturation of the ECM were enhanced. The presence of CeN reduced the physical presence of ROS and the gene expression patterns shifted towards an anti-oxidant profile. Ce therefore constitutes an attractive ion for application in IM-guided BTE. Further research is necessary to clarify the biological mechanisms and pathways that are involved in the Ce-mediated modulation of BMSC differentiation.

Fine-tuning licensing strategies to boost MSC-based immunomodulatory secretome

BACKGROUND

Immune-mediated inflammatory diseases (IMIDs) are a major global health challenge, affecting millions of people and often lacking effective treatments. The mesenchymal stromal cell (MSC)-derived secretome has emerged as a promising therapeutic approach owing to its potent immunomodulatory properties. However, progress has been hindered by the lack of standardized protocols for inducing a robust immunomodulatory MSC phenotype.

METHODS

In this study, we focused on optimizing the MSC-derived secretome to enhance its ability to suppress activated immune cells. Specifically, we examined (1) the effects of IFN-γ and TNF-α, individually and in combination, to uncover potential synergy; (2) the ideal cytokine ratio and (3) concentration; (4) the best production time for the secretome; and (5) the impact of cellular confluence. These factors were systematically evaluated to assess their influence on cell behavior, viability, cytosolic content release, and the secretion of key immunomodulatory and regenerative factors.

RESULTS

Our results demonstrate that overnight licensing with a 1:1 ratio of IFN-γ and TNF-α at 60 ng/mL, followed by 48 h of incubation at 90% confluence, yields an optimized conditioned media (CM) with significantly enhanced immunomodulatory properties. Functional assays showed that this CM can inhibit human peripheral blood mononuclear cell (PBMC) activation with more than twice the effectiveness of suboptimal protocols. Additionally, we found that direct cell-cell contact was critical for inducing regulatory T cells (Tregs), highlighting the complex dynamics of immune regulation.

CONCLUSIONS

These findings establish a robust and standardized MSC licensing protocol, paving the way for the development of innovative and effective therapies to combat IMIDs.

CLINICAL TRIAL NUMBER

Not applicable.

Engineered 3D mesenchymal stem cell aggregates with multifunctional prowess for bone regeneration: Current status and future prospects

BACKGROUND

Impaired efficacy of in vitro expanded mesenchymal stem cells (MSCs) is a universal and thorny situation, which cast a shadow on further clinical translation of exogenous MSCs. Moreover, the relatively lengthy healing process, host metabolic heterogeneity and the sophisticated cell recognition and crosstalk pose rigorous challenges towards MSC-based bone regeneration strategies. Three-dimensional (3D) cell aggregates facilitate more robust intercellular communications and cell-extracellular matrix (ECM) interactions, providing a better mimicry of microarchitectures and biochemical milieus in vivo, which is conducive for stemness maintenance and downstream bone formation.

AIM OF REVIEW

This review enunciates the phenotypic features of MSCs in aggregates, which deepens the knowledge of the MSC fate determination in 3D microenvironment. By summarizing current empowerment methods and biomaterial-combined techniques for establishing functionalized MSC aggregates, this review aims to spark innovative and promising solutions for exalting the translational value of MSCs and improve their therapeutic applications in bone tissue repair.

KEY SCIENTIFIC CONCEPTS OF REVIEW

3D aggregates optimize regenerative behaviors of in vitro cultured MSCs including cell adhesion, viability, proliferation, pluripotency and immunoregulation capacity, etc. Biomaterials hybridization endows MSC aggregates with tailored mechanical and biological properties, which offers more possibilities in adapting various clinical scenarios.

Phenotypic changes associated with continuous long term in vitro expansion of bone marrow-derived mesenchymal stem cells

In vitro expansion of mesenchymal stem cells is necessary to obtain a higher cell number for clinical applications. However, long-term expansion can produce significant phenotypic changes on these cells, decreasing their therapeutic utility. Therefore, understanding the phenotypic changes that long-term expansion triggers in mesenchymal stem cells will allow for better and more consistent cell therapy results. Here, we evaluate the phenotypic changes caused by continuous passaging through colony forming unit-fibroblast assay, senescence beta-galactosidase staining, morphology examination, secretome analysis, surface marker expression, protein quantification, osteogenic and adipogenic differentiation, and CD4+ T lymphocyte immunosuppressive potential. Long-term in vitro culture decreases mesenchymal stem cell osteogenic potential and self-renewal, increases cell size, and senescence, but does not consistently affect adipogenic differentiation. Surface marker expression remains similar for positive and negative markers, while secretory phenotype shifts with decreased p14ARF, MMP-3, p21 Waf1/Cip1,ENA-78, GCP-2, GROα, IL-3, IL-7, IL-8, RANTES, TNFβ, and VEGF-A expression, and increased p53, p16 INK4a, MCP-1, and SDF-1 expression. Immunomodulatory potential remains unchanged. These findings can help better understand the phenotypic changes that mesenchymal stem cells undergo while expanded in vitro.

Aging-dependent dysregulation of EXOSC2 is maintained in cancer as a dependency

Reprogramming of aged donor tissue cells into induced pluripotent stem cells (A-iPSC) preserved the epigenetic memory of aged-donor tissue, defined as genomic instability and poor tissue differentiation in our previous study. The unbalanced expression of RNA exosome subunits affects the RNA degradation complex function and is associated with geriatric diseases including premature aging and cancer progression. We hypothesized that the age-dependent progressive subtle dysregulation of EXOSC2 (exosome component 2) causes the aging traits (abnormal cell cycle and poor tissue differentiation). We used embryonic stem cells as a tool to study EXOSC2 function as the aging trait epigenetic memory determined in A-iPSC because these aging traits could not be studied in senesced aged cells or immortalized cancer cells. We found that the regulatory subunit of PP2A phosphatase, PPP2R5E, is a key target of EXOSC2 and this regulation is preserved in stem cells and cancer.

Electrical Phenotyping of Aged Human Mesenchymal Stem Cells Using Dielectrophoresis

Human mesenchymal stem cells (hMSCs) are widely used in regenerative medicine, but large-scale in vitro expansion alters their function, impacting proliferation and differentiation potential. Currently, a predictive marker to assess these changes is lacking. Here, we used dielectrophoresis (DEP) to characterize the electrical phenotype of hMSCs derived from bone marrow (BM), adipose tissue (AT), and umbilical cord (UC) as they aged in vitro from passage 4 (P4) to passage 9 (P9). The electrical phenotype was defined by the DEP spectra, membrane capacitance, and cytoplasm conductivity. Cell morphology and size, growth characteristics, adipogenic differentiation potential, and osteogenic differentiation potential were assessed alongside label-free biomarker membrane capacitance and cytoplasm conductivity. Differentiation was confirmed by histological staining and RT-qPCR. All hMSCs exhibited typical morphology, though cell size varied, with UC-hMSCs displaying the largest variability across all size metrics. Growth analysis revealed that UC-hMSCs proliferated the fastest. The electrical phenotype varied with cell source and in vitro age, with high passage hMSCs showing noticeable shifts in DEP spectra, membrane capacitance, and cytoplasm conductivity. Correlation analysis revealed that population doubling level (PDL) correlated with membrane capacitance and cytoplasm conductivity, indicating PDL as a more precise marker of in vitro aging than passage number. Additionally, we demonstrate that membrane capacitance correlates with the osteogenic marker COL1A1 and that cytoplasm conductivity correlates with the adipogenic markers ADIPOQ and FABP4, suggesting that DEP-derived electrical properties serve as label-free biomarkers of differentiation potential. While DEP has previously been applied to BM-hMSCs and AT-hMSCs, and more recently to UC-hMSCs, few studies have provided a direct comparison across all three sources or tracked changes across continuous expansion. These findings underscore the utility of DEP as a label-free approach for assessing hMSC aging and function, offering practical applications for optimizing stem cell expansion and stem cell banking in clinical settings.

Batch variability and anti-inflammatory effects of iPSC-derived mesenchymal stromal cell extracellular vesicles in osteoarthritis in vitro model

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) hold promise as a cell-free therapy for osteoarthritis (OA), due to their immunomodulatory and anti-inflammatory properties. However, the need for large-scale expansion to obtain MSC-EVs for clinical use can lead to senescence-related changes and loss of stem-like properties. In this scenario, induced pluripotent stem cell (iPSC)-derived MSCs (iMSCs) offer the unique opportunity to address obstacles associated with traditional MSC-based therapies. This study used a xeno-free (XFS) medium for long-term expansion of both MSCs and iMSCs, and their EVs comparison. Characterization of both cells and EVs was conducted across different passages, and the anti-inflammatory potential of EVs and iEVs was assessed using an in vitro model of osteoarthritis. Long-term expansion of MSCs resulted in cellular senescence and a reduction in trilineage differentiation capacity by passage five, accompanied by diminished anti-inflammatory properties of EVs. On the other hand, iMSCs exhibited batch-to-batch variability in differentiation and EV biological properties. However, the effects of iMSC-EVs were prolonged compared to MSC-EVs, providing a wider window of activity for therapeutic purposes. Despite this, the variability among iMSC batches poses challenges for their reliability in OA treatment. Further work is needed to overcome these limitations for clinical application.

Cell origin and microenvironment: The players of differentiation capacity in human mesenchymal stem cells

Mesenchymal stem cells (MSCs) have several important properties that make them desirable for regenerative medicine. These properties include immunomodulatory ability, growth factor production, and differentiation into various cell types. Despite extensive research and promising results in clinical trials, our understanding of MSC biology, their mechanism of action, and their targeted and routine use in clinics is limited. Differentiation of human MSCs (hMSCs) is a complex process influenced by various elements such as growth factors, pharmaceutical compounds, microRNAs, 3D scaffolds, and mechanical and electrical stimulation. Research has shown that different culture conditions can affect the differentiation potential of hMSCs obtained from multiple fetal and adult sources. Additionally, it seems that what affects the differentiation capacities of these cells is their secretory characteristics, which are influenced by the origin of the cells and the local microenvironment where the cells are located. The review can provide insights into the microenvironment-based mechanisms involved in MSC differentiation, which can be valuable for future therapeutic applications.

Nanotechnology-Assisted mesenchymal stem cells treatment for improved cartilage regeneration: A review of current practices

Cartilage tissue does not promptly elicit an inflammatory response upon injury, hence constraining its capacity for healing and self-regeneration. Mesenchymal Stem Cells (MSC) therapy, enhanced by nanotechnology, offers promising advancements in cartilage repair. Injuries to cartilage often cause chronic pain, where current treatments are inadequate. As MSCs can readily differentiate into chondrocytes and secrete soluble factors, they are essential components in tissue engineering of cartilage repair. Although, like other stem cell applications, clinical applications are restricted by poor post implantation survival and differentiation. Recent studies show that nanoparticles (NPs) can further improve MSC outcomes by promoting cell adhesion, and chondrogenic differentiation allowing for sustained growth factor release. In addition, nanomaterials can improve the biological activity of MSCs, by also facilitating the composition of a conducive microenvironment for cartilage repair. In this review, the application of nanofibrous scaffolds, hydrogels and nanoscale particulate matter to improve mechanical properties in cartilage tissue engineering, are discussed. Moreover, the MSCs and nanotechnology synergistic effects present hope of overcoming the limitations of conventional treatments. Nanotechnology greatly enhances the MSC based cartilage regeneration strategies and could provide better treatment for cartilage related diseases in the future. Future research should be aimed at standardizing MSC harvesting and culturing protocols and contrasting their long-term efficacy.

Implication of bone marrow adipose tissue in bone homeostasis during osteoarthritis

OBJECTIVE

To explore the role of bone marrow adipocytes (BMAds) in osteoarthritis (OA).

METHODS

Male and female C57BL/6 mice (n=4/group) underwent meniscectomy (MNX) or SHAM surgery. OA was determined using Osteoarthritis Research Society International (OARSI) score, and the number of perilipin+ adipocytes was quantified. Mesenchymal Stromal Cells (MSCs) from MNX and SHAM mice were differentiated into osteoblasts and adipocytes. Human adipocytes and MSCs (n=8) were enzymatically isolated from epiphyseal and metaphyseal marrow, and from subcutaneous adipose tissue (SCAT) of hip OA patients. Human OA MSCs were differentiated into osteoblasts and adipocytes (OA-Diff-hAdipo). Gene expression patterns of epiphyseal and metaphyseal BMAds, SCAT adipocytes and OA-Diff-hAdipo were evaluated by RNAseq (n=4). The effect conditioned media from OA epiphyseal bone (n=5) on the alkaline phosphatase (ALP) activity and mineralization kinetics was assessed in vitro.

RESULTS

Increase in BMAd density was positively correlated with cartilage degradation in MNX mice. OA modified the differentiation capacity of MSCs, accelerating adipocyte differentiation and failing to produce osteoblasts in both human and mice. Human epiphyseal, metaphyseal and SCAT adipocytes from the same OA patients each displayed a specific transcriptome, suggesting different functions. Enrichment analysis defined metaphyseal OA-BMAds as cells implicated in hematopoietic stem cell differentiation. On the other hand, epiphyseal OA-BMAds were considered as osteogenic cells showing an up-regulation of genes related to bone mineralization and remodeling. Specifically, OA epiphysis-secreted molecules decreased ALP activity and altered in vitro the mineralization process.

CONCLUSION

All these results support the emergence of BMAds as new cell partners in OA, opening new venues for therapeutic approaches.

Requirements for standardizing the assessment of mesenchymal stem cell therapy and its effects on osteoarthritis

Publications of Soufan et al and Kristjánsson et al in the World Journal of Orthopedics on mesenchymal stem cell (MSC) therapy for osteoarthritis (OA) represent a significant exploration of regenerative medicine's potential in OA treatment. In their research, it is highlighted that MSCs can alleviate OA symptoms and even regenerate cartilage, potentially reversing the disease. They also compared the efficacy of three MSC subtypes, emphasizing the therapeutic advantages of adipose-derived MSCs. MSC injections, a novel and less invasive alternative to traditional treatments such as chondrocyte transplantation or arthroplasty, have a low cost, low risks, and favorable outcomes, presenting a promising approach for OA patients. Additionally, we stressed that the efficacy evaluation criteria, heterogeneity, safety, and other factors must be carefully considered to further advance the clinical translation of MSC therapy for OA.

Efficient Differentiation of hiPSCs into hMSC-like Cells under Chemically Defined Conditions on Temperature-Sensitive Micropatterned Surfaces

The fairness of long-term self-renewal and robust cell proliferation limits the applications of human mesenchymal stem cells (hMSCs) in regenerative medicine. Inducing hMSCs from human-induced pluripotent stem cells (hiPSCs), which have the advantages of autogenous and no cell number issues, is highly valuable. However, current induction methods using FBS-containing mesenchymal culture medium have problems, including immunogenicity, microbial contamination, and low efficiency. To solve these problems, we propose a chemically defined induction protocol incorporating transforming growth factor-beta 1 and retinoic acid (RA) additives in serum-free E6 medium for the suspension induction of embryoid bodies in hiPSCs. Additionally, microgroove-patterned polydimethylsiloxane surfaces coated with temperature-sensitive N-isopropylacrylamide (PNIPAAm) were prepared for efficient harvesting and purification of induced hiPSC-derived hMSCs (hiPSC-MSCs). The results showed that both supplementation with RA and patterned microgrooves with a width of 20 μm could accelerate the induction of hiPSC-MSCs, realizing the promising scalable production of homogeneous cells. This study successfully established a chemically defined induction protocol and utilized patterned surfaces to obtain clinically applicable hiPSC-MSCs, which show great promise in tissue engineering, gene therapy, and cell transplantation.

Engineered Osteochondral Scaffolds with Bioactive Cartilage Zone for Enhanced Articular Cartilage Regeneration

Despite progress, osteochondral (OC) tissue engineering strategies face limitations in terms of articular cartilage layer development and its integration with the underlying bone tissue. The main objective of this study is to develop a zonal OC scaffold with native biochemical signaling in the cartilage zone to promote articular cartilage development devoid of cells and growth factors. Herein, we report the development and in vivo assessment of a novel gradient and zonal-structured scaffold for OC defect regeneration. The scaffold system is composed of a mechanically supportive 3D-printed template containing decellularized cartilage extracellular matrix (ECM) biomaterial in the cartilage zone that possesses bioactive characteristics, such as chemotactic activity and native tissue biochemical composition. OC scaffolds with a bioactive cartilage zone were implanted in vivo in a rabbit osteochondral defect model and assessed for gross morphology, matrix deposition, cellular distribution, and overall tissue regeneration. The scaffold system supported recruitment and infiltration of host cells into the cartilage zone of the graft, which led to increased ECM deposition and physiologically relevant articular cartilage tissue formation. Semi-quantitative ICRS scoring (overall score double for OC scaffold with bioactive cartilage zone compared to PLA scaffold) further confirm the bioactive scaffold enhanced articular cartilage engineering. This strategy of designing bioactive scaffolds to promote endogenous cellular infiltration can be a much simpler and effective approach for OC tissue repair and regeneration.

State-of the-art and future perspective in co-culture systems for tendon engineering

Tendon is a connective tissue that links bone to muscle, allowing for maintenance of skeleton posture, joint movement, energy storage and transmission of muscle force to bone. Tendon is a hypocellular and hypovascular tissue of poor self-regeneration capacity. Current surgical treatments are of limited success, frequently resulting in reinjury. Upcoming cell therapies are primarily based on tenocytes, a cell population of limited self-renewal capacity in vitro or mesenchymal stromal cells, a cell population prone to ectopic bone formation in vivo. Over the years mono- or multi- factorial cell culture technologies have failed to effectively maintain tenocyte phenotype in culture during expansion or to prime mesenchymal stromal cells towards tenogenic lineage prior to implantation. Upon these limitations the concept of co-culture was conceived. Here, we comprehensively review and discuss tenogenic differentiation of mesenchymal stromal cells through direct or indirect culture with tenocytes in an attempt to generate a tenocyte or a tendon-like cell population for regenerative medicine purposes.

Identification of mesenchymal stem cell populations with high osteogenic potential using difference in cell division rate

Introduction

In bone regenerative medicine, mesenchymal stem cells (MSCs) have been widely investigated for their potential in bone regeneration. However, MSCs are a heterogeneous cell population containing a variety of cell types, making it difficult to obtain a homogeneous MSC population sufficient for tissue regeneration. Our group previously reported that by selecting rapidly dividing human auricular chondrocytes, it was possible to enrich for more chondrogenic cells. In this study, we aimed to identify a highly osteogenic MSC population by using a similar approach for mouse bone marrow MSCs.

Methods

Mouse bone marrow MSCs were fluorescently labeled with carboxyfluorescein succinimidyl ester (CFSE) and sorted according to the fluorescence intensity using flow cytometry on day 3 after labeling. To compare the ability to produce bone matrix in vitro, osteogenic differentiation cultures were performed and mineral deposition was confirmed by alizarin red staining. Real-time qPCR was also performed to examine the differences in gene expression between the fast- and slow-dividing cell groups immediately after aliquoting and after osteogenic differentiation.

Results

Differences in the growth rate of the fractionated cells were maintained after culture. Results of osteogenic differentiation culture and alizarin red staining showed more extensive mineral deposition in the slow cell group than in the fast cell group. Calcium quantification also showed higher absorbance in the slow cell group compared to the fast cell group, indicating higher osteogenic differentiation potential in the slow cell group. Furthermore, real-time qPCR analysis showed that osteocalcin expression was higher in the slow cell group in cells immediately after preparative differentiation. In addition, the expression of osteocalcin and sclerostin were higher in the slow cells after osteogenic differentiation.

Conclusion

The slow cell population contains many highly differentiated cells that are already more deeply committed to the bone lineage, suggesting that they have higher osteogenic differentiation potential than the fast cell population. This study will contribute to the realization of better bone regenerative medicine by utilizing the high osteogenic differentiation potential of the slow cell population.

Exploring the therapeutic potential of small extracellular vesicles derived from induced pluripotent stem cell in periodontal regeneration

OBJECTIVES

To investigate the role of small extracellular vesicles derived from induced pluripotent stem cells (iPSC-sEVs) in periodontal tissue regeneration, elucidate their potential molecular mechanisms, and provide theoretical guidance for the clinical application of iPSC-sEVs as a cell-free therapeutic strategy for periodontal tissue regeneration.

METHODS

We investigated the effects of iPSC-sEVs on the proliferation, migration, and osteogenic differentiation of periodontal ligament stem cells (PDLSCs) in vitro. The regenerative potential of iPSC-sEVs was evaluated in vivo, using a periodontal defect model. Bulk RNA sequencing was performed to elucidate the underlying molecular mechanisms.

RESULTS

iPSC-sEVs were isolated, characterized, and systemically evaluated for regenerative potential. The results revealed that treatment with iPSC-sEVs significantly enhanced the proliferation, migration, and osteogenic differentiation of PDLSCs. In situ treatment with iPSC-sEVs loaded onto collagen sponges was performed in a rat model of periodontal defects. Micro-CT and histological analyses indicated that iPSC-sEV treatment markedly promoted alveolar bone repair and periodontal ligament regeneration. Mechanistically, the analysis of bulk RNA sequencing data coupled with experimental validation revealed that iPSC-sEV treatment significantly activated the mitogen-activated protein kinase (MAPK) signaling pathway in PDLSCs. Further investigation showed that the inhibition of this pathway completely abolished the proliferative effects of iPSC-sEVs on PDLSCs.

CONCLUSIONS

iPSC-sEVs promote PDLSC proliferation through MAPK signaling pathway activation, while also enhancing PDLSC migratory and osteogenic differentiation capacities, facilitates the repair and regeneration of damaged periodontal tissue and presents a potential novel therapeutic strategy for clinical periodontal tissue regeneration.

LPA reduces the apoptosis of cryopreserved porcine skin-derived stem cells by inhibiting the regulatory factor TNF-α

Preserving the viability and functionality of stem cells during cryopreservation is crucial for their successful application in regenerative medicine. The aim of this study is to investigate the effect of lysophosphatidic acid (LPA) on reducing the apoptosis of cryopreserved porcine skin-derived stem cells (pSDSCs). Our findings revealed that LPA, at a concentration of 5 μM, significantly improved viability and reduced apoptosis in cryopreserved pSDSCs. Furthermore, our data indicated that LPA enters pSDSCs through receptor type 1 (LPAR1). In cryopreserved pSDSCs, after LPA treatment, the expression level of tumor necrosis factor alpha (TNF-α) protein decreased, suggesting TNF-α involvement in the regulation of the anti-apoptotic process. Additionally, we found that resiquimod (R848), a TNF-α activator, increased the level of apoptosis in cryopreserved pSDSCs. When cryopreserved pSDSCs were treated with both LPA and R848, the protective effect of LPA against apoptosis was decreased. In conclusion, our study demonstrates that LPA could effectively counteract the effect of TNF-α-induced apoptosis, thereby enhancing the survival rates of cryopreserved pSDSCs. Importantly, this study explored a novel mechanism of reducing apoptosis in cryopreserved stem cells.

Nicotinamide adenine dinucleotide rejuvenates septic bone marrow mesenchymal stem cells

BACKGROUND

Sepsis is a severe illness characterized by systemic and multiorgan reactive responses and damage. However, the impact of sepsis on the bone marrow, particularly on bone marrow mesenchymal stem cells (BMSCs), is less reported. BMSCs are critical stromal cells in the bone marrow microenvironment that maintain bone stability and hematopoietic homeostasis; however, the impairment caused by sepsis remains unknown.

AIM

To investigate the effects of sepsis on BMSCs and the underlying mechanisms.

METHODS

BMSCs were obtained from healthy donors and patients with sepsis. We compared the self-renewal capacity, differentiation potential, and hematopoietic supportive ability in vitro. Senescence of septic BMSCs was assessed using β-galactosidase staining, senescence-associated secretory phenotype, intracellular reactive oxygen species levels, and the expression of P16 and P21. Finally, the changes in septic BMSCs after nicotinamide adenine dinucleotide (NAD) treatment were evaluated.

RESULTS

Septic BMSCs showed decreased proliferation and self-renewal, bias towards adipogenic differentiation, and weakened osteogenic differentiation. Additionally, hematopoietic supportive capacity declines in sepsis. The levels of aging markers were significantly higher in the septic BMSCs. After NAD treatment, the proliferation capacity of septic BMSCs showed a recovery trend, with increased osteogenic and hematopoietic supportive capacities. Sepsis resulted in decreased expression of sirtuin 3 (SIRT3) in BMSCs, whereas NAD treatment restored SIRT3 expression, enhanced superoxide dismutase enzyme activity, reduced intracellular reactive oxygen species levels, maintained mitochondrial stability and function, and ultimately rejuvenated septic BMSCs.

CONCLUSION

Sepsis accelerates the aging of BMSCs, as evidenced by a decline in self-renewal and osteogenic capabilities, as well as weakened hematopoietic support functions. These deficiencies can be effectively reversed via the NAD/SIRT3/superoxide dismutase pathway.

Stem cell therapy: A promising therapeutic approach for skeletal muscle atrophy

Skeletal muscle atrophy results from disruptions in the growth and metabolism of striated muscle, leading to a reduction or loss of muscle fibers. This condition not only significantly impacts patients’ quality of life but also imposes substantial socioeconomic burdens. The complex molecular mechanisms driving skeletal muscle atrophy contribute to the absence of effective treatment options. Recent advances in stem cell therapy have positioned it as a promising approach for addressing this condition. This article reviews the molecular mechanisms of muscle atrophy and outlines current therapeutic strategies, focusing on mesenchymal stem cells, induced pluripotent stem cells, and their derivatives. Additionally, the challenges these stem cells face in clinical applications are discussed. A deeper understanding of the regenerative potential of various stem cells could pave the way for breakthroughs in the prevention and treatment of muscle atrophy.

Retarding human adipose-derived MSCs senescence and promoting tendon repair using cell sheet engineering with a histone methyltransferase inhibitor

Mesenchymal stem cell (MSC) holds immense potential as candidates for cell therapy in the treatment of tendon injuries due to their remarkable ability for multiple cell differentiation. However, the proliferative and differentiation capacity of MSCs has been limited by cellular senescence during the process of expanding culture. Therefore, in this study, our aim was to maintain the beneficial properties of MSCs. We found that SETD7, a histone methyltransferase, was upregulated during ex vivo expansion of human adipose-derived mesenchymal stem cells (hAD-MSCs). Pharmacological inhibition of SETD7 with PFI-2 in hAD-MSCs cultures delayed their senescence, as evident by the diminished expression of senescent-associated genes and the maintenance of their proliferation and differentiation capacity. Upon transplantation, cell sheets derived from hAD-MSCs expanded with PFI-2 were better able to accelerate tendon repair. Therefore, the present findings reveal that SETD7 is an important target to improve the expansion of hAD-MSCs by delaying senescence, which is importance for the development of efficient stem cell-based therapeutic approaches.

Rejuvenation of Bone Marrow Mesenchymal Stem Cells: Mechanisms and Their Application in Senile Osteoporosis Treatment

Bone marrow mesenchymal stromal cells (BM-MSCs) are multipotent cells present in bone marrow; they play a crucial role in the process of bone formation. Cellular senescence is defined as a stable state of cell cycle arrest that impairs the functioning of cells. Research has shown that aging triggers a state of senescence in BM-MSCs, leading to a reduced capacity for osteogenic differentiation and the accumulation of senescent cells, which can accelerate the onset of various diseases. Therefore, it is essential to explore mechanisms and strategies for the rejuvenation of senescent BM-MSCs. Senile osteoporosis (SOP) is a metabolic bone disease characterized by reduced bone formation. The senescence of BM-MSCs is considered one of the most important factors in the occurrence and development of SOP. Therefore, the rejuvenation of BM-MSCs for the treatment of SOP represents a promising strategy. This work provides a summary of the functional alterations observed in senescent BM-MSCs and a systematic review of the mechanisms that facilitate the rejuvenation of senescent BM-MSCs. Additionally, we analyze the progress in and the limitations associated with the application of rejuvenated senescent BM-MSCs to treat SOP, with the aim of providing new insights for the prevention and treatment of SOP.

Single-Cell Transcriptome Decoding Umbilical Cord-Derived Mesenchymal Stem Cell Heterogeneity Reveals a Unique IL1R1HighPDGFRAHigh Ultroser-G-MSC With Osteogenesis and Chondrogenesis Signatures

The heterogeneity of human umbilical cord mesenchymal stem cells (hUC-MSCs) is culturing-dependent, resulting in functional non-uniformness. To achieve the best clinical benefit, a comprehensive understanding of the origin of the heterogeneity in different culture systems can identify functional subgroups to direct the precise application of hUC-MSCs. Here, we create a single-cell transcriptome atlas of hUC-MSC in different culture systems for the identification of a subgroup of Ultroser-G-MSCs with high osteogenic and chondrogenic potentials featured by high expressions of IL1R1 and PDGFRA. Further experimental validations surprisingly reveal that IL1R1highPDGFRAhigh Ultroser-G-MSCs possess advantages over "traditional" hUC-MSCs in the treatments of modeled osteoarthritis, leading to a cell-cell communication network centered in Clusters 0 and 2. Moreover, we found that Wnt5 signaling is the key pathway for the dynamic transformation of osteogenic and chondrogenic phenotypes in hUC-MSC. Overall, the present study paves the way for the clarification of heterogenetic nature of hUC-MSC in different culture systems for the selection of optimal MSC types to achieve the precision on clinical treatments.

Automated Manufacturing Processes and Platforms for Large-scale Production of Clinical-grade Mesenchymal Stem/ Stromal Cells

Mesenchymal stem/stromal cells (MSCs) hold immense potential for regenerative medicine due to their remarkable regenerative and immunomodulatory properties. However, their therapeutic application requires large-scale production under stringent regulatory standards and Good Manufacturing Practice (GMP) guidelines, presenting significant challenges. This review comprehensively evaluates automated manufacturing processes and platforms for the scalable production of clinical-grade MSCs. Various large-scale culture vessels, including multilayer flasks and bioreactors, are analyzed for their efficacy in MSCs expansion. Furthermore, automated MSCs production platforms, such as Quantum® Cell Expansion System, CliniMACS Prodigy®, NANT001/ XL, CellQualia™, Cocoon® Platform, and Xuri™ Cell Expansion System W25 are reviewed and compared as well. We also underscore the importance of optimizing culture media specifically emphasizing the shift from fetal bovine serum to humanized or serum-free alternatives to meet GMP standards. Moreover, advances in alternative cryopreservation methods and controlled-rate freezing systems, that offer promising improvements in MSCs preservation, are discussed as well. In conclusion, advancing automated manufacturing processes and platforms is essential for realizing the full potential of MSCs-based regenerative medicine and accomplishing the increasing demand for cell-based therapies. Collaborative initiatives involving industry, academia, and regulatory bodies are emphasized to accelerate the translation of MSCs-based therapies into clinical practice.

A self-forming bone membrane generated by periosteum-derived stem cell spheroids enhances the repair of bone defects

The periosteum, a highly specialized thin tissue, is instrumental in contributing to as much as 70 % of early bone formation. Recognizing the periosteum's vital physiological roles, the fabrication of a biomimetic periosteum has risen as an auspicious strategy for addressing extensive bone defects. In the study, we obtained such biomimetic periosteum by utilizing periosteum-derived stem cells (PDSCs) spheroids. These spheroids are induced to spontaneously generate a bioactive membrane on a delicate 3D-printed polycaprolactone (PCL) substrate. This process yields a biomimetic periosteum rich in the resources needed for bone repair. The in vitro evaluations demonstrated that this membrane can act as a repository for growth factors and stem cells. The release kinetics confirmed a sustained delivery of BMP-2 and VEGF, which promoted enhanced osteogenesis and angiogenesis in vitro, respectively. The in vivo results further highlighted robust bone regeneration from critical cranial defects upon the application of this biomimetic periosteum. The biomimetic periosteum, easily harvested and potent in bioactivity, presents substantial clinical potential, particularly for the treatment of critical-sized bone defects. STATEMENT OF SIGNIFICANCE: PDSC theoretically demonstrates substantial potential in membrane construction, a value we've harnessed in this pioneering application. By employing cell spheroids, we've successfully integrated a substantial number of cells into the membrane framework. PDSC spheroids exhibit the remarkable ability to self-assemble into functional membranes, endowing them with robust biological capabilities that enhance their performance in biological systems. The in vitro evaluations demonstrated that this membrane can act as a repository for growth factors and stem cells. The in vivo bone repair facilitated by this membrane is notably effective, characterized by superior bone quality and accelerated formation rates. This process mirrors the natural intramembrane ossification, offering a promising approach to bone integration and regeneration.

Thawing, Growth, and Maintenance of Vero Cell Lines

Vero cell line is derived from the kidney of an African green monkey and is one of the most common mammalian continuous cell lines used in research. Its deficiency in the production of type 1 interferons allows this cell line to be susceptible and permissible to replication of several viruses, including the yellow fever virus. Continuous cell culture in the laboratory can increase the risk of contamination, as well as loss of characteristics of interest in the strain. To minimize these risks a cultivation standard should be established. This chapter presents useful protocols for the maintenance of Vero cells for laboratorial routine, such as thawing vials from a cell bank stock, maintenance by subcultivation procedures, adaptation of the cells to grow in serum-free media, and production of cell culture plates for laboratory routine assays.

Decellularized Extracellular Matrix and Polyurethane Vascular Grafts Have Positive Effects on the Inflammatory and Pro-Thrombotic State of Aged Endothelial Cells

In vitro assessment of small-diameter synthetic vascular grafts usually uses standard cell culture conditions with early-passage cells. However, these conduits are mainly implanted in elderly patients and are subject to complex cellular interactions influenced by age and inflammation. Understanding these factors is central to the development of vascular grafts tailored to the specific needs of patients. In this study, the effects of aged endothelial cells subjected to pro- and anti-inflammatory agents and cultivated on a newly developed biodegradable electrospun thermoplastic polyurethane/poly(urethane-urea) blend (TPU/TPUU), on clinically available expanded polytetrafluorethylene (ePTFE), and on decellularized extracellular matrix (dECM) grafts were investigated. Young and aged endothelial cells were exposed to pro- and anti-inflammatory agents and characterized by morphology, migration capacity, and gene expression. In addition, the cells were seeded onto the various graft materials and examined microscopically alongside gene expression analyses. When exposed to pro-inflammatory cytokines, young and aged cells demonstrated signs of endothelial activation. Cells seeded on ePTFE showed reduced attachment and increased expression of pro-inflammatory genes compared with the other materials. dECM and TPU/TPUU substrates provided better support for endothelialization with aged cells under inflammatory conditions compared with ePTFE. Moreover, TPU/TPUU showed positive effects on reducing pro-thrombotic and pro-inflammatory gene expression in endothelial cells. Our results thus emphasize the importance of developing new synthetic graft materials as an alternative for clinically used ePTFE.

Safety and Tolerability of Wharton's Jelly-Derived Mesenchymal Stem Cells for Patients With Duchenne Muscular Dystrophy: A Phase 1 Clinical Study

BACKGROUND AND PURPOSE

This study was an open-label, dose-escalation, phase 1 clinical trial to determine the safety and dose of EN001 for patients with Duchenne muscular dystrophy (DMD). EN001, developed by ENCell, are allogeneic early-passage Wharton's jelly-derived mesenchymal stem cells that originate at the umbilical cord, with preclinical studies demonstrating their high therapeutic efficacy for DMD.

METHODS

This phase 1 clinical trial explored the safety and tolerability of EN001 as a potential treatment option for patients with DMD. Six pediatric participants with DMD were divided into two subgroups of equal size: low-dose EN001 (5.0×10⁵ cells/kg) and high-dose EN001 (2.5×10⁶ cells/kg). All participants were monitored for 12 weeks after EN001 administration to assess its safety. Dose-limiting toxicity (DLT) was evaluated across 2 weeks post administration. Exploratory efficacy was evaluated by measuring serum creatine kinase levels, and functional evaluations-including spirometry, myometry, the North Star Ambulatory Assessment, and the 6-minute walk test-were conducted at week 12 and compared with the baseline values.

RESULTS

No participants experienced serious adverse events related to EN001 injection during the 12-week follow-up period. Mild adverse events included injection-related local erythema, edema, parosmia, and headache, but DLT was not observed. Functional evaluations at week 12 revealed no significant changes from baseline.

CONCLUSIONS

These results demonstrated that EN001 are safe and well tolerated for patients with DMD, and did not cause serious adverse events. The efficacy of EN001 could be confirmed through larger-scale future studies that incorporate repeated dosing and have a randomized controlled trial design.

Harnessing the ubiquitin proteasome system as a key player in stem cell biology

Intracellular proteins take part in almost every body function; thus, protein homeostasis is of utmost importance. The ubiquitin proteasome system (UPS) has a fundamental role in protein homeostasis. Its main role is to selectively eradicate impaired or misfolded proteins, thus halting any damage that could arise from the accumulation of these malfunctioning proteins. Proteasomes have a critical role in controlling protein homeostasis in all cell types, including stem cells. We will discuss the role of UPS enzymes as well as the 26S proteasome complex in stem cell biology from several angles. First, we shall overview common trends of proteasomal activity and gene expression of different proteasomal subunits and UPS enzymes upon passaging and differentiation of stem cells toward various cell lineages. Second, we shall explore the effect of modulating proteasomal activity in stem cells and navigate through the interrelation between proteasomes' activity and various proteasome-related transcription factors. Third, we will shed light on curated microRNAs and long non-coding RNAs using various bioinformatics tools that might have a possible role in regulating UPS in stem cells and possibly, upon manipulation, can enhance the differentiation process into different lineages and/or delay senescence upon cell passaging. This will help to decipher the role played by individual UPS enzymes and subunits as well as various interrelated molecular mediators in stem cells' maintenance and/or differentiation and open new avenues in stem cell research. This can ultimately provide a leap toward developing novel therapeutic interventions related to proteasome dysregulation.

Protocol for developing shape-morphing 4D bioprinted magnetic constructs to promote articular cartilage regeneration using silk fibroin-gelatin bioink

External magnetic fields can regulate cellular responses. Here, we present a protocol to fabricate magnetic constructs by 4D bioprinting with shape-morphing properties using silk fibroin-gelatin bioinks for articular cartilage regeneration. We illustrate the steps for magnetic bioink formulation, bioprinting, and chondrogenic induction of human bone marrow mesenchymal stem/stromal cells. We detail the steps to actuate the constructs using an external magnetic field and then characterize chondrogenesis. Magnetic field actuation may be helpful for mechanically activating constructs for articular cartilage regeneration. For complete details on the use and execution of this protocol, please refer to Chakraborty et al.1.

Transcriptomic Changes in Human Tonsil-Derived Mesenchymal Stem Cells Across Culture Passages

BACKGROUND/OBJECTIVES

Tonsil-derived mesenchymal stem cells (TMSCs) are in the limelight in regenerative medicine due to their high proliferation and differentiation potential. It is important to conduct studies to determine the optimal conditions for achieving the maximum yield while maintaining the optimal differentiation capacity of TMSCs.

METHODS

This study explores the impact of serial subculture on TMSCs by analyzing gene expression at passages 2, 4, 6, and 8. For each culture passage, genes with significant differences in RNA expression from previous passages were selected and their characteristics were observed performing enrichment analysis including KEGG (Kyoto Encyclopedia of Genes and Genomes) and Reactome pathway.

RESULTS

At each passage, a "cell cycle" term was ranked high with statistical significance in the KEGG and Reactome pathway. Cell cycle gene expression, including Cyclin-dependent kinases (CDKs) and cyclins, increased until passage 6, then decreased by passage 8. The cell cycle is known to be important not only for proliferation but also for determining whether stem cells maintain pluripotency or differentiate into various lineages.

CONCLUSIONS

The results suggest that cell cycle gene expression can guide the timing for differentiation induction, with passage 6 potentially being a critical point for initiating differentiation.

LEP O-GlcNAcylation inactivates NF-κB pathway by suppressing LEP protein level and thus mediates cellular senescence and osteogenic differentiation in mouse mesenchymal stem cells

BACKGROUND

Cellular senescence is a key driver of decreased bone formation and osteoporosis. Leptin (LEP) has been implicated in cellular senescence and osteogenic differentiation. The aim of this study was to investigate the mechanisms by which LEP mediates cellular senescence and osteogenic differentiation.

METHODS

C3H10T1/2 cells were treated with etoposide to induce cellular senescence, which was assessed by β-galactosidase staining. Quantitative real-time PCR and western blotting were used to measure the levels of senescence markers p21 and p16, as well as osteogenic differentiation-related genes ALP, COL1A1, and RUNX2. Alkaline phosphatase (ALP) staining and alizarin red S staining were performed to evaluate osteogenic differentiation. The NF-κB pathway and O-GlcNAcylation were assessed by western blotting.

RESULTS

Etoposide treatment increased the number of senescent cells and the levels of p21 and p16, along with elevated LEP expression. These effects were reversed by LEP knockdown. Additionally, LEP knockdown increased ALP staining density and osteoblast mineralization nodules, as well as the mRNA and protein levels of ALP, COL1A1, and RUNX2, indicating that LEP knockdown promoted osteogenic differentiation in C3H10T1/2 cells. Mechanistically, LEP knockdown inactivated the NF-κB pathway by inhibiting the nuclear translocation of p65. Furthermore, OGT was found to promote O-GlcNAcylation of LEP at the S50 site.

CONCLUSION

Our findings demonstrated that O-GlcNAcylation of LEP inactivated the NF-κB pathway by reducing LEP protein levels, thereby inhibiting cellular senescence and promoting osteogenic differentiation in C3H10T1/2 cells. This study may provide a novel therapeutic target for the treatment of osteoporosis.

In vitro and in vivo assessment of a non-animal sourced chitosan scaffold loaded with xeno-free umbilical cord mesenchymal stromal cells cultured under macromolecular crowding conditions

There is an increasing demand to not only accelerate the development of advanced therapy tissue engineered medicines, but to also eliminate xenogeneic materials from their development cycle. With these in mind, herein we first assessed the influence of carrageenan as macromolecular crowding agent to enhance and accelerate extracellular matrix deposition in xeno-free human umbilical cord mesenchymal stromal cell cultures and we developed and characterised a non-animal sourced chitosan scaffold. Following appropriate in vitro experimentation, a splinted nude mouse wound healing model was used to assess wound closure and scar size of non-treated control, non-animal sourced chitosan scaffold, non-animal sourced chitosan scaffold loaded with xeno-free human umbilical cord mesenchymal stromal cells and non-animal sourced chitosan scaffold loaded with xeno-free human umbilical cord mesenchymal stromal cells cultured under macromolecular crowding conditions groups. Across all three donors, carrageenan supplementation significantly increased collagen deposition at day 5, day 8 and day 11 without affecting cell morphology, viability, DNA concentration and metabolic activity. Through freeze drying, a non-animal sourced chitosan sponge was developed with appropriate structural and mechanical properties for wound healing applications. In vitro biological analysis made apparent that neither the scaffold nor macromolecular crowding negatively impacted xeno-free human umbilical cord mesenchymal stromal cell metabolic activity and proliferation. In vivo biological analysis revealed no significant differences between the groups in wound closure and scar size, raising question about the suitability of the model. In any case, this work sets the foundations for the development of completely xeno-free tissue engineered medicines.

Roles of extracellular vesicles from mesenchymal stem cells in regeneration

Mesenchymal stem cells (MSCs) are highly valued in regenerative medicine due to their ability to self-renew and differentiate into various cell types. Their therapeutic benefits are primarily due to their paracrine effects, in particular through extracellular vesicles (EVs), which are related to intercellular communication. Recent advances in EV production and extraction technologies highlight the potential of MSC-derived EVs (MSC-EVs) in tissue engineering and regenerative medicine. MSC-EVs offer several advantages over traditional cell therapies, including reduced toxicity and immunogenicity compared with whole MSCs. EVs carrying functional molecules such as growth factors, cytokines, and miRNAs play beneficial roles in tissue repair, fibrosis treatment, and scar prevention by promoting angiogenesis, skin cell migration, proliferation, extracellular matrix remodeling, and reducing inflammation. Despite the potential of MSC-EVs, there are several limitations to their use, including variability in quality, the need for standardized methods, low yield, and concerns about the composition of EVs and the potential risks. Overall, MSC-EVs are a promising alternative to cell-based therapies, and ongoing studies aim to understand their actions and optimize their use for better clinical outcomes in wound healing and skin regeneration.

Reparative homing of bone mesenchymal stem cells induced by iMSCs via the SDF-1/CXCR4 axis for articular cartilage defect restoration

BACKGROUND

The intrinsic healing ability of articular cartilage is poor after injury or illness, and untreated injury could lead to cartilage degeneration and ultimately osteoarthritis. iMSCs are derived from embryonic induced pluripotent stem cells and have strong therapeutic capabilities in the repair of cartilage defects, while the mechanism of action is unclear. The aim of this study is to clarify the repair mode of iMSCs on cartilage defects in rat knee joints, elucidate the chemotactic effect of iMSCs on autologous BMSCs in rats, and provide a basis for the treatment of cartilage defects and endogenous regeneration with iMSCs.

METHODS

Based on the establishment of the rat cartilage defect model, the reparative effect of iMSCs on the rat cartilage defect was evaluated. The cartilage repair was evaluated by quantitative score, H&E staining, Masson staining and Safranin-O staining, and the metabolic changes of iMSCs in the joint cavity were detected in vivo. The expression of SOX9, CD29, CD90, ColⅠ, ColⅡ, PCNA, SDF-1, and CXCR4 was detected by immunohistochemistry (IHC), IF, flow cytometry, respectively. After co-culturing iMSCs with BMSCs in vitro, the expression of CXCR4/SDF-1 on the cell membrane surface of BMSCs was detected by western blotting.; The level of p-Akt and p-Erk1/2 in total protein of BMSCs were detected by western blotting.

SIGNIFICANCE

Our research results provide experimental evidence for the treatment of cartilage defects and endogenous regeneration with iMSCs; This also provides new ideas for the clinical treatment of cartilage defects using iMSCs.

Assessing the Effects of Dasatinib on Mesenchymal Stem/Stromal Cells

Introduction

Progressive aging, or senescence, of mesenchymal stem/stromal cells (MSCs) is a major obstacle faced when trying to culture potent stem cells for use in therapy. Senescent cells are irreversibly nondividing cells that cease performing critical functional effects. Elimination of senescent cells using biochemical means, such as the use of senolytic drugs like dasatinib, may be useful in retaining the viable and proliferating populations of the cells.

Methods

An in vitro approach was used to investigate the effect of dasatinib on phenotypic, genotypic, and immunomodulatory functionality of osteogenic and adipogenic differentiated MSCs. Replicative senescence was achieved through multiple sub-culturing in vitro, then senescent and non-senescent cultures were treated with a standard dosage of dasatinib. MSCs were then differentiated into osteogenic, adipogenic or chondrogenic cultures using conditioned media to be tested for the three criteria being investigated.

Results

Significant changes were observed in these criteria, indicated by evidence gathered from proliferation and indoleamine 2,3 dioxygenase activity assays. Phenotypic results of dasatinib were shown to reduce the population of senescent MSCs while allowing non-senescent MSCs to continue differentiating and proliferating without interference from senescent cells. Genotypic results showed no change to upregulation in markers associated with osteogenic and adipogenic cells when exposed to dasatinib. Indoleamine Dioxygenase activity showed insignificant differences in cells exposed to dasatinib versus control groups, providing evidence against compromised cellular immune function.

Conclusion

This investigation provides insight into how dasatinib effects MSCs functional ability and provides a better understanding of the function of senolytic agents.

Gold Kiwi-Derived Nanovesicles Mitigate Ultraviolet-Induced Photoaging and Enhance Osteogenic Differentiation in Bone Marrow Mesenchymal Stem Cells

Bone marrow mesenchymal stem cells (BM-MSCs) play a crucial role in bone formation through their ability to differentiate into osteoblasts. Aging, however, detrimentally affects the differentiation and proliferation capacities of BM-MSCs, consequently impairing bone regeneration. Thus, mitigating the aging effects on BM-MSCs is vital for addressing bone-related pathologies. In this study, we demonstrate that extracellular nanovesicles isolated from gold kiwi (GK-NVs) protect human BM-MSCs from ultraviolet (UV)-induced photoaging, thereby alleviating aging-related impairments in cellular functions that are crucial for bone homeostasis. Notably, GK-NVs were efficiently taken up by BM-MSCs without causing cytotoxicity. GK-NVs reduced intracellular reactive oxygen species (ROS) levels upon UV irradiation, restoring impaired proliferation and migration capabilities. Furthermore, GK-NVs corrected the skewed differentiation capacities of UV-irradiated BM-MSCs by enhancing osteoblast differentiation, as evidenced by the increased expression in osteoblast-specific genes and the calcium deposition, and by reducing adipocyte differentiation, as indicated by the decreased lipid droplet formation. These findings position GK-NVs as a promising biomaterial for the treatment of bone-related diseases such as osteoporosis.

Mesenchymal stromal cell therapies for traumatic neurological injuries

Improved treatment options are urgently needed for neurological injuries resulting from trauma or iatrogenic events causing long-term disabilities that severely impact patients' quality of life. In vitro and animal studies have provided promising proof-of-concept examples of regenerative therapies using mesenchymal stromal cells (MSC) for a wide range of pathological conditions. Over the previous decade, various MSC-based therapies have been investigated in clinical trials to treat traumatic neurological injuries. However, while the safety and feasibility of MSC treatments has been established, the patient outcomes in these studies have not demonstrated significant success in the translation of MSC regenerative therapy for the treatment of human brain and spinal cord injuries. Herein, we have reviewed the literature and ongoing registered trials on the application of MSC for the treatment of traumatic brain injury, traumatic spinal cord injury, and peripheral nerve injury. We have focused on the shortcomings and technological hurdles that must be overcome to further advance clinical research to phase 3 trials, and we discuss recent advancements that represent potential solutions to these obstacles to progress.

Differentiation of Human Mesenchymal Stem Cells into Corneal Epithelial Cells: Current Progress

The limited availability of corneal tissue grafts poses significant challenges in the treatment of corneal blindness. Novel treatment utilizes stem cell grafts transplanted from the healthy side of the cornea to the damaged side. However, this procedure is only possible for those who have one-sided corneal blindness. Human stem cells offer promising potential for corneal tissue engineering, providing an alternative solution. Among the different types of stem cells, mesenchymal stem cells (MSCs) stand out due to their abundance and ease of isolation. Human MSCs can be derived from bone marrow, adipose, and umbilical cord tissues. Differentiating MSC toward corneal tissue can be achieved through several methods including chemical induction and co-culture with adult corneal cells such as human limbal epithelial stem cells (LESCs) and human corneal epithelial cells (hTCEpi). Adipose-derived stem cells (ADSCs) are the most common type of MSC that has been studied for corneal differentiation. Corneal epithelial cells are the most common corneal cell type targeted by researchers for corneal differentiation. Chemical induction with small molecules, especially bone morphogenetic protein 4 (BMP4), all-trans retinoic acid (ATRA), and epidermal growth factor (EGF), has gained more popularity in corneal epithelial cell differentiation. This review highlights the current progress in utilizing MSCs for corneal differentiation studies, showcasing their potential to revolutionize treatments for corneal blindness.

Disorganized chromatin hierarchy and stem cell aging in a male patient of atypical laminopathy-based progeria mandibuloacral dysplasia type A

Studies of laminopathy-based progeria offer insights into aging-associated diseases and highlight the role of LMNA in chromatin organization. Mandibuloacral dysplasia type A (MAD) is a largely unexplored form of atypical progeria that lacks lamin A post-translational processing defects. Using iPSCs derived from a male MAD patient carrying homozygous LMNA p.R527C, premature aging phenotypes are recapitulated in multiple mesenchymal lineages, including mesenchymal stem cells (MSCs). Comparison with 26 human aging MSC expression datasets reveals that MAD-MSCs exhibit the highest similarity to senescent primary human MSCs. Lamina-chromatin interaction analysis reveals reorganization of lamina-associating domains (LADs) and repositioning of non-LAD binding peaks may contribute to the observed accelerated senescence. Additionally, 3D genome organization further supports hierarchical chromatin disorganization in MAD stem cells, alongside dysregulation of genes involved in epigenetic modification, stem cell fate maintenance, senescence, and geroprotection. Together, these findings suggest LMNA missense mutation is linked to chromatin alterations in an atypical progeroid syndrome.

Behavioral dynamics of medicinal signaling cells from porcine bone marrow in long-term culture

Medicinal signaling cells (MSC) hold promise for regenerative medicine due to their ability to repair damaged tissues. However, their effectiveness can be affected by how long they are cultured in the lab. This study investigated how passage number influences key properties for regenerative medicine of pig bone marrow MSC. The medicinal signiling cells derived from pig bone marrow (BM-MSC) were cultured in D-MEM High Glucose supplemented with 15% foetal bovine serum until the 25th passage and assessed their growth, viability, ability to differentiate into different cell types (plasticity), and cell cycle activity. Our findings showed that while the cells remained viable until the 25th passage, their ability to grow and differentiate declined after the 5th passage. Additionally, cells in later passages spent more time in a resting phase, suggesting reduced activity. In conclusion, the number of passages is a critical factor for maintaining ideal MSC characteristics. From the 9th passage BM-MSC exhibit decline in proliferation, differentiation potential, and cell cycle activity. Given this, it is possible to suggest that the use of 5th passage cells is the most suitable for therapeutic applications.

Enhancing Gingival-Derived Mesenchymal Stem Cell Potential in Tissue Engineering and Regenerative Medicine Through Paraprobiotics

Gingival-derived mesenchymal stem cells (GMSCs) stand for a unique source of mesenchymal stem cells (MSCs) isolated from a neural crest origin with potential application in regenerative medicine. However, there are some limitations to the usage of these cells in clinical cell therapy such as reduced cell number and undesirable differentiation of the cell throughout frequent passages. Nowadays, studies have applied manipulation strategies to improve MSCs' effectiveness in clinical therapy. Among all of the materials used for this purpose, there is a growing trend for the use of biomaterials such as probiotic extracts or their conditioned media due to their lower toxicity. In the present study, we utilized extracts from Lactobacillus reuteri and Lactobacillus rhamnosus to assess their potential to enhance the function of GMSCs. We compared the effectiveness of these bacterial extracts to determine their relative efficacy. Bacterial extracts of two lactic acid bacteria were prepared using an ultrasonic homogenizing device. The impact of these bacterial extracts on GMSCs was evaluated through Alizarin Red and Oil Red O staining, cell counting by Trypan Blue staining, and real-time polymerase chain reaction. The findings of our study indicate that the administration of 50 μg/mL L. rhamnosus extract resulted in a greater enhancement of stemness marker expression, osteogenic differentiation, and proliferation of GMSCs compared with an equivalent concentration of L. reuteri extract. Neither of these bacterial extracts revealed any effect on the differentiation of the GMSCs into the adipogenic lineage. These findings suggest that L. rhamnosus extract could be more effective at promoting GMSCs' efficacy in tissue engineering and regenerative medicine.

Metabolomics Dysfunction in Replicative Senescence of Periodontal Ligament Stem Cells Regulated by AMPK Signaling Pathway

Periodontal ligament mesenchymal stem cells (PDLSCs) are a promising cell resource for stem cell-based regenerative medicine in dentistry, but they inevitably acquire a senescent phenotype after prolonged in vitro expansion. The key regulators of PDLSCs during replicative senescence remain unclear. Here, we sought to elucidate the role of metabolomic changes in determining the cellular senescence of PDLSCs. PDLSCs were cultured to passages 4, 10, and 20. The senescent phenotypes of PDLSCs were detected, and metabolomics analysis was performed. We found that PDLSCs manifested senescence phenotype during passaging. Metabolomics analysis showed that the metabolism of replicative senescence in PDLSCs varied significantly. The AMP-activated protein kinase (AMPK) signaling pathway was closely related to adenosine monophosphate (AMP) levels. The AMP:ATP ratio increased in senescent PDLSCs; however, the levels of p-AMPK, FOXO1 and FOXO3a decreased with senescence. We treated PDLSCs with an activator of the AMPK pathway (AICAR) and observed that the phosphorylated AMPK level at P20 PDLSCs was partially restored. These data delineate that the metabolic process of PDLSCs is active in the early stage of senescence and attenuated in the later stages of senescence; however, the sensitivity of AMPK phosphorylation sites is impaired, causing senescent PDLSCs to fail to respond to changes in energy metabolism.

Effects of Replicative Senescence of Human Chorionic MSCs on their EV-miRNA Profile

Chorionic mesenchymal stromal cells (CHO-MSCs) and their extracellular vesicles (EVs) are becoming increasingly popular, since chorion is ethically harmless and an easily accessible source of MSCs. However, until now there is only a limited number of studies with a thorough characterization of CHO-MSCs derived EVs and their miRNA profile. In this study, we monitored changes in the EV-miRNA profile between early and late passage of human CHO-MSCs. First, senescence of CHO-MSCs was induced by serial passaging and confirmed by morphological changes, shortened telomeres and changes in the expression of selected genes. The expression of MSCs-specific surface markers CD73, CD90, CD105 did not change with increasing passages. Next, EVs and their miRNA profiles were compared between early vs late passage cells. Number of EVs and their size were not significantly changed. Seven of the top 10 most expressed EV-miRNAs were common to both early and late passages. A differential expression study between early and late passages identified 37 significantly differentially expressed EV-miRNAs, out of which 23 were found to be associated with pathways of cellular senescence based on KEGG pathway analysis. A set of 9 miRNAs were identified as the most frequently associated with senescence and/or with the most altered expression between early and late passages, out of which miR-145-5p, miR-335-5p and miR-199b-3p were the most significant downregulated miRNAs in late passages. The most upregulated EV-miRNAs were miR-1307-3p, miR-3615 and miR320b. Targeting these miRNAs in future experiments may prolong the therapeutic potential of CHO-MSCs and their EVs.

Exosome-mediated renal protection: Halting the progression of fibrosis

Renal fibrosis is a complex and multifactorial process that involves inflammation, cell proliferation, collagen, and fibronectin deposition in the kidney, ultimately leading to chronic kidney disease and even end-stage renal disease. The main goal of treatment is to slow down or halt the progression of fibrosis and to improve or preserve kidney function. Despite significant progress made in understanding the underlying mechanisms of renal fibrosis, current therapies have limited renal protection as the disease progresses. Exosomes derived from stem cells are a newer area of research for the treatment of renal fibrosis. Exosomes as nano-sized extracellular vesicles carry proteins, lipids, and nucleic acids, which can be taken up by local or distant cells, serving as mediators of intercellular communication and as drug delivery vehicles. Exosomes deliver molecules that reduce inflammation, renal fibrosis and extracellular matrix protein production, and promote tissue regeneration in animal models of kidney disease. Additionally, they have several advantages over stem cells, such as being non-immunogenic, having low risk of tumor formation, and being easier to produce and store. This review describes the use of natural and engineered exosomes containing therapeutic agents capable of mediating anti-inflammatory and anti-fibrotic processes during both acute kidney injury and chronic kidney disease. Exosome-based therapies will be compared with stem cell-based treatments for tissue regeneration, with a focus on renal protection. Finally, future directions and strategies for improving the therapeutic efficacy of exosomes are discussed.