Methods and Strategies for Procurement, Isolation, Characterization, and Assessment of Senescence of Human Mesenchymal Stem Cells from Adipose Tissue

Senotherapeutics for mesenchymal stem cell senescence and rejuvenation

Mesenchymal stem cells (MSCs) are susceptible to replicative senescence and senescence-associated functional decline, which hampers their use in regenerative medicine. Senotherapeutics are drugs that target cellular senescence through senolytic and senomorphic functions to induce apoptosis and suppress chronic inflammation caused by the senescence-associated secreted phenotype (SASP), respectively. Therefore, senotherapeutics could delay aging-associated degeneration. They could also be used to eliminate senescent MSCs during in vitro expansion or bioprocessing for transplantation. In this review, we discuss the role of senotherapeutics in MSC senescence, rejuvenation, and transplantation, with examples of some tested compounds in vitro. The prospects, challenges, and the way forward in clinical applications of senotherapeutics in cell-based therapeutics are also discussed.

Aging and Mesenchymal Stem Cells: Basic Concepts, Challenges and Strategies

Aging and frailty are complex processes implicating multifactorial mechanisms, such as replicative senescence, oxidative stress, mitochondrial dysfunction, or autophagy disorder. All of these mechanisms drive dramatic changes in the tissue environment, such as senescence-associated secretory phenotype factors and inflamm-aging. Thus, there is a demand for new therapeutic strategies against the devastating effects of the aging and associated diseases. Mesenchymal stem cells (MSC) participate in a "galaxy" of tissue signals (proliferative, anti-inflammatory, and antioxidative stress, and proangiogenic, antitumor, antifibrotic, and antimicrobial effects) contributing to tissue homeostasis. However, MSC are also not immune to aging. Three strategies based on MSC have been proposed: remove, rejuvenate, or replace the senescent MSC. These strategies include the use of senolytic drugs, antioxidant agents and genetic engineering, or transplantation of younger MSC. Nevertheless, these strategies may have the drawback of the adverse effects of prolonged use of the different drugs used or, where appropriate, those of cell therapy. In this review, we propose the new strategy of "Exogenous Restitution of Intercellular Signalling of Stem Cells" (ERISSC). This concept is based on the potential use of secretome from MSC, which are composed of molecules such as growth factors, cytokines, and extracellular vesicles and have the same biological effects as their parent cells. To face this cell-free regenerative therapy challenge, we have to clarify key strategy aspects, such as establishing tools that allow us a more precise diagnosis of aging frailty in order to identify the therapeutic requirements adapted to each case, identify the ideal type of MSC in the context of the functional heterogeneity of these cellular populations, to optimize the mass production and standardization of the primary materials (cells) and their secretome-derived products, to establish the appropriate methods to validate the anti-aging effects and to determine the most appropriate route of administration for each case.

Standardized Anatomic and Regenerative Facial Fat Grafting: Objective Photometric Evaluation 1 to 19 Months After Injectable Tissue Replacement and Regeneration

BACKGROUND

A standardized technique for facial fat grafting, injectable tissue replacement and regeneration (ITR2), incorporating new regenerative approaches, was developed to address anatomic volume losses in superficial and deep fat compartments as well as skin aging.

OBJECTIVES

The aim of this study was to track the short- and long-term effects of facial fat grafting by ITR2 in the midfacial zone over 19 months.

METHODS

Twenty-nine females were analyzed for midfacial volume changes after autologous fat transfer with ITR2 with varying fat parcel sizes. Volumes were evaluated with an imaging system to calculate differences between a predefined, 3-dimensional midfacial zone measured preoperatively and after fat grafting.

RESULTS

Patient data were analyzed collectively and by age (<55 and >55 years). Collective analysis revealed a trend of initial volume loss during Months 1 to 7 followed by an increase during Months 8 to 19, averaging 56.6% postoperative gain, and ending at an average of 52.3% gain in volume by 14 to 19 months. A similar trend was observed for patients <55 years of age, with a 54.1% average postoperative gain and a greater final average of 75.2%. Conversely, patients >55 years of age revealed a linear decay from 60.6% to 29.5%. Multiple regression analysis revealed no statistically significant influence of weight change throughout the study.

CONCLUSIONS

A dynamic change in facial volume was observed, with an initial decrease in facial volume followed by a rebound effect, by 19 months after treatment, of improved facial volume regardless of the amount of fat injected. Volume improvement was greater in patients <55 years old, whereas in patients >55 years old, volume gradually decreased. This study represents the first time that progressive improvement in facial volume has been shown 19 months after treatment.

LEVEL OF EVIDENCE: 4

Transcriptomic analysis and biological evaluation reveals that LMO3 regulates the osteogenic differentiation of human adipose derived stem cells via PI3K/Akt signaling pathway

Autologous bone transplantation which is a common treatment method for bone defects needs a large quantity of bone cells. In order to develop new treatments to regenerating bone tissues, this research aimed at identifying the key genes and finding their mechanism in human adipose-derived stem cells (hADSCs) osteogenesis. GSE63754, GSE89330 and GSE72429 were downloaded to perform GO functional and KEGG pathway analyses, construct a competing endogenous RNA (ceRNA) network, construct a PPI network and identify hub genes. The expression level of LMO3 during the osteogenesis of hADSCs was examined by quantitative reverse transcription polymerase chain reaction and western blot. Lentivirus transfection was used to knock down or overexpress LMO3, which enabled us to investigate the effect of LMO3 on osteogenic differentiation of hADSCs. Wortmannin were used to identify the mechanism of the LMO3/PI3K/Akt axis in regulating osteogenic differentiation of hADSCs. Moreover, ectopic bone formation in nude mice was used to investigate the effect of LMO3 on osteogenesis in vivo. In this study, we found the expression of LMO3 was significantly upregulated during the osteogenic differentiation of hADSCs. LMO3 knockdown remarkably suppressed osteogenic differentiation of hADSCs, while LMO3 overexpression promoted osteogenic differentiation of hADSCs both in vitro and in vivo. Moreover, we discovered that the enhancing effect of LMO3 overexpression on osteogenic differentiation was related to the activation of PI3K/Akt signaling pathway. Inhibition of PI3K/Akt signaling pathway with wortmannin effectively blocked the stimulation of osteogenic differentiation induced by LMO3 overexpression. In conclusion, based on transcriptomic analysis, we identified key genes involved in regulating the osteogenic differentiation of hADSCs. In addition, we found that LMO3 might act as a positive modulator of hADSC osteogenic differentiation by mediating PI3K/Akt signaling pathway. Manipulating the expression of LMO3 and its associated pathways might contribute to advances in bone regeneration and tissue engineering.

A Comparative Study of the Effect of Anatomical Site on Multiple Differentiation of Adipose-Derived Stem Cells in Rats

Mesenchymal stem cells (MSCs) derived from adipose tissue are evolved into various cell-based regenerative approaches. Adipose-derived stem cells (ASCs) isolated from rats are commonly used in tissue engineering studies. Still, there is a gap in knowledge about how the harvest locations influence and guide cell differentiation. This study aims to investigate how the harvesting site affects stem-cell-specific surface markers expression, pluripotency, and differentiation potential of ASCs in female Sprague Dawley rats. ASCs were extracted from the adipose tissue of the peri-ovarian, peri-renal, and mesenteric depots and were compared in terms of cell morphology. MSCs phenotype was validated by cell surfaces markers using flow cytometry. Moreover, pluripotent gene expression of Oct4, Nanog, Sox2, Rex-1, and Tert was evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR). ASCs multipotency was evaluated by specific histological stains, and the results were confirmed by quantitative polymerase chain reaction (RT-qPCR) expression analysis of specific genes. There was a non-significant difference detected in the cell morphology and immunophenotype between different harvesting sites. ASCs from multiple locations were significantly varied in their capacity to differentiate into adipocytes, osteoblastic cells, and chondrocytes. To conclude, depot selection is a critical element that should be considered when using ASCs in tissue-specific cell-based regenerative therapies research.

Regenerative and stem cell-based techniques for facial rejuvenation

This review discusses the most novel ideas and modalities being incorporated into facial rejuvenation. Recent innovative techniques include the use of regenerative stem cell techniques and regeneration supportive modalities such as nano-technology or gene therapies. This review aims to investigate approaches that are less well known and lacking established evidence in order to proactively study these techniques prior to them becoming popularized. These applications and relevant research were reviewed in the context of both surgical and non-surgical modalities in clinical practice. Future directions include the concept of "precision cosmetic medicine" utilizing gene editing and cellular therapies to tailor rejuvenation techniques based on each individual's genetic make-up and therefore needs.

A transcriptomic analysis of serial-cultured, tonsil-derived mesenchymal stem cells reveals decreased integrin α3 protein as a potential biomarker of senescent cells

Background

Mesenchymal stem cells (MSCs) have been widely used for stem cell therapy, and serial passage of stem cells is often required to obtain sufficient cell numbers for practical applications in regenerative medicine. A long-term serial cell expansion can potentially induce replicative senescence, which leads to a progressive decline in stem cell function and stemness, losing multipotent characteristics. To improve the therapeutic efficiency of stem cell therapy, it would be important to identify specific biomarkers for senescent cells.

Methods

Tonsil-derived mesenchymal stem cells (TMSCs) with 20–25 passages were designated as culture-aged TMSCs, and their mesodermal differentiation potentials as well as markers of senescence and stemness were compared with the control TMSCs passaged up to 8 times at the most (designated as young). A whole-genome analysis was used to identify novel regulatory factors that distinguish between the culture-aged and control TMSCs. The identified markers of replicative senescence were validated using Western blot analyses.

Results

The culture-aged TMSCs showed longer doubling time compared to control TMSCs and had higher expression of senescence-associated (SA)-β-gal staining but lower expression of the stemness protein markers, including Nanog, Oct4, and Sox2 with decreased adipogenic, osteogenic, and chondrogenic differentiation potentials. Microarray analyses identified a total of 18,614 differentially expressed genes between the culture-aged and control TMSCs. The differentially expressed genes were classified into the Gene Ontology categories of cellular component (CC), functional component (FC), and biological process (BP) using KEGG (Kyoto encyclopedia of genes and genomes) pathway analysis. This analysis revealed that those genes associated with CC and BP showed the most significant difference between the culture-aged and control TMSCs. The genes related to extracellular matrix-receptor interactions were also shown to be significantly different (p < 0.001). We also found that culture-aged TMSCs had decreased expressions of integrin α3 (ITGA3) and phosphorylated AKT protein (p-AKT-Ser⁴⁷³) compared to the control TMSCs.

Conclusions

Our data suggest that activation of ECM-receptor signaling, specifically involved with integrin family-mediated activation of the intracellular cell survival-signaling molecule AKT, can regulate stem cell senescence in TMSCs. Among these identified factors, ITGA3 was found to be a representative biomarker of the senescent TMSCs. Exclusion of the TMSCs with the senescent TMSC markers in this study could potentially increase the therapeutic efficacy of TMSCs in clinical applications.

Adipose-Derived Mesenchymal Stem Cells in the Treatment of Diabetic Foot Ulcers: A Review of Preclinical and Clinical Studies

This review provides an outline of the use of adipose-derived mesenchymal stem cells (AMSCs) in the treatment of diabetic foot ulcers (DFUs). A systematic search of PubMed and the Cochrane database was performed on October 2, 2019. Eighteen studies were identified (14 preclinical and 4 clinical). Studies in animal models have demonstrated that AMSCs enhance diabetic wound healing, accelerate granulation tissue formation, and increase reepithelialization and neovascularization. Only 1 randomized control trial has been published so far. Patients (n = 25) with DFUs were treated using an allogeneic AMSC directly on the wound bed as a primary dressing, and improvements were found in complete wound closure in the treatment group (n = 16). Three clinical studies showed that autologous AMSC might be a safe alternative to achieve therapeutic angiogenesis in patients with diabetes and peripheral arterial disease. Based on the available evidence, AMSCs hold promise in the treatment of DFUs. However, this evidence requires confirmation by well-designed trials. Additional studies are also required to understand some issues regarding this treatment for DFUs. For example, the potential application of autologous or allogeneic AMSCs in different types of DFUs, optimal dose/infusion schedules, safety evaluations, and cost-effectiveness.

Mesenchymal Stem Cell Senescence and Rejuvenation: Current Status and Challenges

Over the past decades, mesenchymal stem cell (MSC)-based therapy has been intensively investigated and shown promising results in the treatment of various diseases due to their easy isolation, multiple lineage differentiation potential and immunomodulatory effects. To date, hundreds of phase I and II clinical trials using MSCs have been completed and many are ongoing. Accumulating evidence has shown that transplanted allogeneic MSCs lose their beneficial effects due to immunorejection. Nevertheless, the function of autologous MSCs is adversely affected by age, a process termed senescence, thus limiting their therapeutic potential. Despite great advances in knowledge, the potential mechanisms underlying MSC senescence are not entirely clear. Understanding the molecular mechanisms that contribute to MSC senescence is crucial when exploring novel strategies to rejuvenate senescent MSCs. In this review, we aim to provide an overview of the biological features of senescent MSCs and the recent progress made regarding the underlying mechanisms including epigenetic changes, autophagy, mitochondrial dysfunction and telomere shortening. We also summarize the current approaches to rejuvenate senescent MSCs including gene modification and pretreatment strategies. Collectively, rejuvenation of senescent MSCs is a promising strategy to enhance the efficacy of autologous MSC-based therapy, especially in elderly patients.

Differential circular RNA expression profiling during osteogenic differentiation in human adipose-derived stem cells

Aim: Circular RNAs (circRNAs) are essential for stem cell differentiation. This study aimed to investigate their exact mechanism of action in human adipose-derived stem cell (hADSC) osteogenesis. Materials & methods: Isolated hADSCs were cultured in growth medium or osteogenic medium, then total RNA was extracted for circRNA microarray, hierarchical cluster, gene ontology, regulating pathway and circRNA–miRNA–mRNA network analyses. Results: A total of 171 circRNAs were upregulated and 119 were downregulated in induced groups compared with those in noninduced groups. Eight circRNAs, 40 miRNAs and 342 mRNAs were selected to construct a competing circRNA-miRNA-mRNA network. Conclusion: These findings may provide novel insight into altered and specific circRNAs that might function as competing endogenous RNAs in hADSCs during osteogenic differentiation.

Adipose-Derived Mesenchymal Stem Cells Isolated from Patients with Abdominal Aortic Aneurysm Exhibit Senescence Phenomena

Mesenchymal stem cells (MSCs) have shown beneficial effects in the treatment of abdominal aortic aneurysm (AAA). Nonetheless, the biological properties of adipose-derived MSCs (ASCs) from patients with AAA (AAA-ASCs) remain unclear. This study is aimed at investigating the properties of cell phenotype and function of AAA-ASCs compared with ASCs from age-matched healthy donors (H-ASCs). H-ASCs and AAA-ASCs were studied for cell phenotype, differentiation capacity, senescence, and mitochondrial and autophagic functions. Cellular senescence was examined by senescence-associated β-galactosidase (SA-β-gal) staining. Mitochondrial morphology was determined by MitoTracker staining. Despite the similar surface markers of AAA-ASCs and H-ASCs, AAA-ASCs exhibited altered multidifferentiation potential. Compared with H-ASCs, AAA-ASCs displayed enhanced senescence manifested by increased SA-β-gal activity and decreased proliferation and migration ability. Furthermore, AAA-ASCs showed increased mitochondrial fusion, reactive oxygen species (ROS) production, and decreased mitochondrial membrane potential. In addition, AAA-ASCs exhibited decreased autophagy level, upregulation of IL-6 and TNF-α secretion, and downregulation of IL-10 secretion compared with H-ASCs. Nonetheless, treatment of AAA-ASCs with rapamycin (an autophagy activator) dramatically reduced secretion of IL-6 and TNF-α and enhanced secretion of IL-10. In conclusion, our study showed that AAA-ASCs exhibit senescence phenomena and decreased cell function. Understanding the specific alterations in AAA-ASCs will help explore novel strategies to restore cell function for AAA treatment.