The therapeutic effect of secretome from human umbilical cord-derived mesenchymal stem cells in age-related osteoporosis

Exosomes promote hFOB1.19 proliferation and differentiation via LINC00520

BACKGROUND

Osteoporosis remains a significant clinical challenge worldwide. Recent studies have shown that exosomes stimulate bone regeneration. Thus, it is worthwhile to explore whether exosomes could be a useful therapeutic strategy for osteoporosis. The purpose of this study was to investigate the effects of exosomes derived from human umbilical cord mesenchymal stem cells (hucMSCs) on osteoblast proliferation and differentiation.

METHODS

Exosomes were isolated from hucMSCs. Bioinformatics analysis was performed to identify the differentially expressed lncRNAs in myeloma-derived mesenchymal stem cells. Plasmids encoding LINC00520 or short hairpin RNA of LINC00520 were transfected into hucMSCs and then exosomes were isolated. After human osteoblasts hFOB1.19 were exposed to the obtained exosomes, cell survival, cell cycle, apoptosis and calcium deposits of hFOB1.19 cell were detected by MTT, 7-aminoactinomycin D, Annexin V-FITC/propidium iodide and Alizarin red staining, respectively.

RESULTS

In hFOB1.19 cells, 10 × 10⁹/mL hucMSC-derived exosomes inhibited cell proliferation, arrested cell cycle, and promoted apoptosis, while hucMSCs or 1 × 10⁹/mL exosomes promoted cell proliferation, accelerated cell cycle, and promoted calcium deposits and the expression of OCN, RUNX2, collagen I and ALP. In hFOB1.19 cells, exosomes from hucMSCs with LINC00520 knockdown reduced the survival and calcium deposits, arrested the cell cycle, and enhanced the apoptosis, while exosomes from hucMSCs overexpressing LINC00520 enhance the proliferation and calcium deposits and accelerated the cell cycle.

CONCLUSIONS

LINC00520 functions as a modulator of calcium deposits, and exosomes derived from hucMSCs overexpressing LINC00520 might be a novel therapeutic approach for osteoporosis.

Rejuvenation of Senescent Mesenchymal Stem Cells to Prevent Age-Related Changes in Synovial Joints

Mesenchymal/medicinal stem/signaling cells (MSCs), well known for regenerative potential, have been involved in hundreds of clinical trials. Even if equipped with reparative properties, aging significantly decreases their biological activity, representing a major challenge for MSC-based therapies. Age-related joint diseases, such as osteoarthritis, are associated with the accumulation of senescent cells, including synovial MSCs. An impaired ability of MSCs to self-renew and differentiate is one of the main contributors to the human aging process. Moreover, senescent MSCs (sMSCs) are characterized by the senescence-messaging secretome (SMS), which is typically manifested by the release of molecules with an adverse effect. Many factors, from genetic and metabolic pathways to environmental stressors, participate in the regulation of the senescent phenotype of MSCs. To better understand cellular senescence in MSCs, this review discusses the characteristics of sMSCs, their role in cartilage and synovial joint aging, and current rejuvenation approaches to delay/reverse age-related pathological changes, providing evidence from in vivo experiments as well.

Hydrogel-based delivery system applied in the local anti-osteoporotic bone defects

Osteoporosis is an age-related systemic skeletal disease leading to bone mass loss and microarchitectural deterioration. It affects a large number of patients, thereby economically burdening healthcare systems worldwide. The low bioavailability and complications, associated with systemic drug consumption, limit the efficacy of anti-osteoporosis drugs currently available. Thus, a combination of therapies, including local treatment and systemic intervention, may be more beneficial over a singular pharmacological treatment. Hydrogels are attractive materials as fillers for bone injuries with irregular shapes and as carriers for local therapeutic treatments. They exhibit low cytotoxicity, excellent biocompatibility, and biodegradability, and some with excellent mechanical and swelling properties, and a controlled degradation rate. This review reports the advantages of hydrogels for adjuvants loading, including nature-based, synthetic, and composite hydrogels. In addition, we discuss functional adjuvants loaded with hydrogels, primarily focusing on drugs and cells that inhibit osteoclast and promote osteoblast. Selecting appropriate hydrogels and adjuvants is the key to successful treatment. We hope this review serves as a reference for subsequent research and clinical application of hydrogel-based delivery systems in osteoporosis therapy.

Extracellular vesicles derived from neural EGFL-Like 1-modified mesenchymal stem cells improve acellular bone regeneration via the miR-25-5p-SMAD2 signaling axis

Stem cell based transplants effectively regenerate tissues; however, limitations such as immune rejection and teratoma formation prevent their application. Extracellular vesicles (EVs)-mediated acellular tissue regeneration is a promising alternative to stem cell based transplants. Although neural EGFL-like 1 (Nell1) is known to contribute to the osteogenic differentiation of bone marrow stem cells (BMSCs), it remains unknown whether EVs are involved in this process. Here, we present that EVs derived from Nell1-modified BMSCs (Nell1/EVs) have a stronger ability to promote BMSC osteogenesis owing to miR-25–5p downregulation. MiR-25–5p inhibits osteogenesis by targeting Smad2 and suppressing the SMAD and extracellular signal-related kinase 1 and 2 (ERK1/2) pathway activation. In addition, we demonstrate that the 3D-Nell1/EV-hydrogel system is beneficial for bone regeneration in vivo, probably stemming from a slow, continuous release and high concentration of EVs in the bone defect area. Thus, our results have shown the potential of Nell1/EVs as a novel acellular bone regeneration strategy. Mechanistically, the identification of miR-25-5p-SMAD2 signaling axis expands the knowledge of Nell1/EVs induced osteogenesis.

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Extracellular vesicles contributed to the Nell1-induced osteoblast lineage commitment program of BMSCs.

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The miRNA profile of Nell1-modified-EVs remarkably changed after genetic modification of their parental cells.

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miRNA-25–5p downregulation of Nell1-modifed-EVs helped with osteogenic effect via the SMAD and ERK pathway.

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Hydrogel captured with Nell1-modified-EVs showed potential to repair large bone defect.

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

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

Self-Assembling Imageable Silk Hydrogels for the Focal Treatment of Osteosarcoma

Background: The standard treatment for osteosarcoma comprises complete surgical resection and neoadjuvant chemotherapy, which may cause serious side effects and partial or total limb loss. Therefore, to avoid the disadvantages of traditional treatment, we developed self-assembling imageable silk hydrogels for osteosarcoma.

Methods: We analysed whether iodine induced apoptosis in MG-63 and Saos-2 cells by using CCK-8 and flow cytometry assays and transmission electron microscopy. Western blotting was used to analyse the pathway of iodine-induced apoptosis in osteosarcoma cells. PEG400, silk fibroin solution, polyvinylpyrrolidone iodine (PVP-I), and meglumine diatrizoate (MD) were mixed to produce an imageable hydrogel. A nude mouse model of osteosarcoma was established, and the hydrogel was injected locally into the interior of the osteosarcoma with X-ray guidance. The therapeutic effect and biosafety of the hydrogel were evaluated.

Results: Iodine treatment at 18 and 20 µM for 12 h resulted in cell survival rate reduced to 50 ± 2.1% and 50.5 ± 2.7% for MG-63 and Sao-2 cells, respectively (p < 0.01). The proportion of apoptotic cells was significantly higher in the iodine-treatment group than in the control group (p < 0.05), and apoptotic bodies were observed by transmission electron microscopy. Iodine could regulate the death receptor pathway and induce MG-63 and Saos-2 cell apoptosis. The hydrogels were simple to assemble, and gels could be formed within 38 min. A force of less than 50 N was required to inject the gels with a syringe. The hydrogels were readily loaded and led to sustained iodine release over 1 week. The osteosarcoma volume in the PEG-iodine-silk/MD hydrogel group was significantly smaller than that in the other three groups (p < 0.001). Caspase-3 and poly (ADP-ribose) polymerase (PARP) expression levels were significantly higher in the PEG-iodine-silk/MD hydrogel group than in the other three groups (p < 0.001). Haematoxylin and eosin (H&E) staining showed no abnormalities in the heart, liver, spleen, lung, kidney, pancreas or thyroid in any group.

Conclusions: Self-assembling imageable silk hydrogels could be injected locally into osteosarcoma tissues with X-ray assistance. With the advantages of good biosafety, low systemic toxicity and minimal invasiveness, self-assembling imageable silk hydrogels provide a promising approach for improving the locoregional control of osteosarcoma.

Investigating the Effects of Conditioned Media from Stem Cells of Human Exfoliated Deciduous Teeth on Dental Pulp Stem Cells

Pulp regeneration has recently attracted interest in modern dentistry. However, the success ratio of pulp regeneration is low due to the compromising potential of stem cells, such as their survival, migration, and odontoblastic differentiation. Stem cells from human exfoliated deciduous teeth (SHED) have been considered a promising tool for regenerative therapy due to their ability to secrete multiple factors that are essential for tissue regeneration, which is achieved by minimally invasive procedures with fewer ethical or legal concerns than those of other procedures. The aim of this study is to investigate the potency of SHED-derived conditioned media (SHED CM) on dental pulp stem cells (DPSCs), a major type of mesenchymal stem cells for dental pulp regeneration. Our results show the promotive efficiency of SHED CM on the proliferation, survival rate, and migration of DPSCs in a dose-dependent manner. Upregulation of odontoblast/osteogenic-related marker genes, such as ALP, DSPP, DMP1, OCN, and RUNX2, and enhanced mineral deposition of impaired DPSCs are also observed in the presence of SHED CM. The analysis of SHED CM found that a variety of cytokines and growth factors have positive effects on cell proliferation, migration, anti-apoptosis, and odontoblast/osteogenic differentiation. These findings suggest that SHED CM could provide some benefits to DPSCs in pulp regeneration.

Polymeric Hydrogels as Mesenchymal Stem Cell Secretome Delivery System in Biomedical Applications

Secretomes of mesenchymal stem cells (MSCs) have been successfully studied in preclinical models for several biomedical applications, including tissue engineering, drug delivery, and cancer therapy. Hydrogels are known to imitate a three-dimensional extracellular matrix to offer a friendly environment for stem cells; therefore, hydrogels can be used as scaffolds for tissue construction, to control the distribution of bioactive compounds in tissues, and as a secretome-producing MSC culture media. The administration of a polymeric hydrogel-based MSC secretome has been shown to overcome the fast clearance of the target tissue. In vitro studies confirm the bioactivity of the secretome encapsulated in the gel, allowing for a controlled and sustained release process. The findings reveal that the feasibility of polymeric hydrogels as MSC -secretome delivery systems had a positive influence on the pace of tissue and organ regeneration, as well as an enhanced secretome production. In this review, we discuss the widely used polymeric hydrogels and their advantages as MSC secretome delivery systems in biomedical applications.

The therapeutic potential of mesenchymal stem cells in treating osteoporosis

Osteoporosis (OP), a common systemic metabolic bone disease, is characterized by low bone mass, increasing bone fragility and a high risk of fracture. At present, the clinical treatment of OP mainly involves anti-bone resorption drugs and anabolic agents for bone, but their long-term use can cause serious side effects. The development of stem cell therapy and regenerative medicine has provided a new approach to the clinical treatment of various diseases, even with a hope for cure. Recently, the therapeutic advantages of the therapy have been shown for a variety of orthopedic diseases. However, these stem cell-based researches are currently limited to animal models; the uncertainty regarding the post-transplantation fate of stem cells and their safety in recipients has largely restricted the development of human clinical trials. Nevertheless, the feasibility of mesenchymal stem cells to treat osteoporotic mice has drawn a growing amount of intriguing attention from clinicians to its potential of applying the stem cell-based therapy as a new therapeutic approach to OP in the future clinic. In the current review, therefore, we explored the potential use of mesenchymal stem cells in human OP treatment.

Conditioned Medium from Bone Marrow Mesenchymal Stem Cells Restored Oxidative Stress-Related Impaired Osteogenic Differentiation

Oxidative stress from high levels of intracellular reactive oxygen species (ROS) has been linked to various bone diseases. Previous studies indicate that mesenchymal stem cells (MSC) secrete bioactive factors (conditioned medium (MSC-CM)) that have antioxidant effects. However, the antioxidant role of MSC-CM on osteogenesis has not been fully studied. We aimed to identify antioxidant proteins in MSC-CM using mass spectrometry-based proteomics and to explore their effects on osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSC) exposed to oxidative stress induced by hydrogen peroxide (H₂O₂). Our analysis revealed that MSC-CM is comprised of antioxidant proteins that are involved in several biological processes, including negative regulation of apoptosis and positive regulation of cell proliferation. Then, hBMSC exposed to H₂O₂ were treated with MSC-CM, and the effects on their osteogenic differentiation were evaluated. MSC-CM restored H₂O₂-induced damage to hBMSC by increasing the antioxidant enzyme-SOD production and the mRNA expression level of the anti-apoptotic BCL-2. A decrease in ROS production and cellular apoptosis was also shown. MSC-CM also modulated mRNA expression levels of osteogenesis-related genes, runt-related transcription factor 2, collagen type I, bone morphogenic protein 2, and osteopontin. Furthermore, collagen type I protein secretion, alkaline phosphatase activity, and in vitro mineralization were increased. These results indicate that MSC-CM contains several proteins with antioxidant and anti-apoptotic properties that restored the impaired hBMSC osteogenic differentiation associated with oxidative stress.

Modern Approaches to Acellular Therapy in Bone and Dental Regeneration

An approach called cell-free therapy has rapidly developed in regenerative medicine over the past decade. Understanding the molecular mechanisms and signaling pathways involved in the internal potential of tissue repair inspires the development of new strategies aimed at controlling and enhancing these processes during regeneration. The use of stem cell mobilization, or homing for regeneration based on endogenous healing mechanisms, prompted a new concept in regenerative medicine: endogenous regenerative medicine. The application of cell-free therapeutic agents leading to the recruitment/homing of endogenous stem cells has advantages in overcoming the limitations and risks associated with cell therapy. In this review, we discuss the potential of cell-free products such as the decellularized extracellular matrix, growth factors, extracellular vesicles and miRNAs in endogenous bone and dental regeneration.

Mesenchymal Stromal Cell Secretome for the Treatment of Immune-Mediated Inflammatory Diseases: Latest Trends in Isolation, Content Optimization and Delivery Avenues

Considering the high prevalence and the complex pharmacological management of immune-mediated inflammatory diseases (IMIDs), the search for new therapeutic approaches for their treatment is vital. Although the immunomodulatory and anti-inflammatory effects of mesenchymal stromal cells (MSCs) have been extensively studied as a potential therapy in this field, direct MSC implantation presents some limitations that could slow down the clinical translation. Since the beneficial effects of MSCs have been mainly attributed to their ability to secrete a plethora of bioactive factors, their secretome has been proposed as a new and promising pathway for the treatment of IMIDs. Formed from soluble factors and extracellular vesicles (EVs), the MSC-derived secretome has been proven to elicit immunomodulatory effects that control the inflammatory processes that occur in IMIDs. This article aims to review the available knowledge on the MSC secretome, evaluating the advances in this field in terms of its composition, production and application, as well as analyzing the pending challenges in the field. Moreover, the latest research involving secretome administration in IMIDs is discussed to provide an updated state-of-the-art for this field. Finally, novel secretome delivery alternatives are reviewed, paying special attention to hydrogel encapsulation as one of the most convenient and promising strategies.

A review of biomimetic scaffolds for bone regeneration: Toward a cell-free strategy

In clinical terms, bone grafting currently involves the application of autogenous, allogeneic, or xenogeneic bone grafts, as well as natural or artificially synthesized materials, such as polymers, bioceramics, and other composites. Many of these are associated with limitations. The ideal scaffold for bone tissue engineering should provide mechanical support while promoting osteogenesis, osteoconduction, and even osteoinduction. There are various structural complications and engineering difficulties to be considered. Here, we describe the biomimetic possibilities of the modification of natural or synthetic materials through physical and chemical design to facilitate bone tissue repair. This review summarizes recent progresses in the strategies for constructing biomimetic scaffolds, including ion-functionalized scaffolds, decellularized extracellular matrix scaffolds, and micro- and nano-scale biomimetic scaffold structures, as well as reactive scaffolds induced by physical factors, and other acellular scaffolds. The fabrication techniques for these scaffolds, along with current strategies in clinical bone repair, are described. The developments in each category are discussed in terms of the connection between the scaffold materials and tissue repair, as well as the interactions with endogenous cells. As the advances in bone tissue engineering move toward application in the clinical setting, the demonstration of the therapeutic efficacy of these novel scaffold designs is critical.

Early-senescent bone marrow mesenchymal stem cells promote C2C12 cell myogenic differentiation by preventing the nuclear translocation of FOXO3

AIMS

Mouse bone marrow mesenchymal stem cells (BMSCs) are pluripotent cells with self-renewal and differentiation abilities. Since the effects of senescent BMSCs on C2C12 cells are not fully clear, the present study aimed to elucidate these effects.

MAIN METHODS

Senescence-associated β-galactosidase staining and western blotting were performed to confirm the senescence of BMSCs. Immunofluorescence and western blotting were used to assess myoblast differentiation in each group. The role of the AKT/P70 signaling pathway and forkhead box O3 (FOXO3) nuclear translocation was explored by western blotting. BMSC-derived exosomes were injected into the tibialis anterior of mice, and RT-qPCR was used to assess the role of exosomes in promoting muscle differentiation.

KEY FINDINGS

Conditioned medium (CM) from early-senescent BMSCs promoted myogenic differentiation in vitro, which was detected as enhanced expression of myosin heavy chain (MHC), myogenin (MYOG), and myogenic differentiation 1 (MyoD). The AKT signaling pathway was found to be regulated by CM, which inhibited FOXO3 nuclear translocation. RT-qPCR analysis results showed that MHC, MyoD, and MYOG mRNA expression increased in the tibialis anterior of mice after exosome injection.

SIGNIFICANCE

The present study demonstrated that early-senescent BMSCs accelerated C2C12 cell myogenic differentiation, and the transcription factor, FOXO3, was the target of senescent cells. Collectively, our results suggest that the AKT/P70 signaling pathway mediates the effect of BMSCs on neighboring cells.

Biomaterial-based extracellular vesicle delivery for therapeutic applications

Extracellular vesicle (EV)- based therapies have been successfully tested in preclinical models for several biomedical applications, including tissue engineering, drug delivery and cancer therapy. However, EVs are most commonly delivered via local or systemic injection, which results in rapid clearance. In order to prolong the retention of EVs at target site and improve their therapeutic efficacy, biomaterial-based delivery systems are being investigated. This review discusses the various biomaterial-based systems that have been used to deliver EVs for therapeutic applications, specifically highlighting any strategies for controlled release. Further, challenges to clinical translation of biomaterial-based EV delivery systems are also discussed.

Translational Animal Models Provide Insight Into Mesenchymal Stromal Cell (MSC) Secretome Therapy

The therapeutic potential of the mesenchymal stromal cell (MSC) secretome, consisting of all molecules secreted by MSCs, is intensively studied. MSCs can be readily isolated, expanded, and manipulated in culture, and few people argue with the ethics of their collection. Despite promising pre-clinical studies, most MSC secretome-based therapies have not been implemented in human medicine, in part because the complexity of bioactive factors secreted by MSCs is not completely understood. In addition, the MSC secretome is variable, influenced by individual donor, tissue source of origin, culture conditions, and passage. An increased understanding of the factors that make up the secretome and the ability to manipulate MSCs to consistently secrete factors of biologic importance will improve MSC therapy. To aid in this goal, we can draw from the wealth of information available on secreted factors from MSC isolated from veterinary species. These translational animal models will inspire efforts to move human MSC secretome therapy from bench to bedside.

Amniotic Fluid Stem Cell-Derived Extracellular Vesicles Counteract Steroid-Induced Osteoporosis In Vitro

Background—Osteoporosis is characterized by defects in both quality and quantity of bone tissue, which imply high susceptibility to fractures with limitations of autonomy. Current therapies for osteoporosis are mostly concentrated on how to inhibit bone resorption but give serious adverse effects. Therefore, more effective and safer therapies are needed that even encourage bone formation. Here we examined the effect of extracellular vesicles secreted by human amniotic fluid stem cells (AFSC) (AFSC-EV) on a model of osteoporosis in vitro. Methods—human AFSC-EV were added to the culture medium of a human pre-osteoblast cell line (HOB) induced to differentiate, and then treated with dexamethasone as osteoporosis inducer. Aspects of differentiation and viability were assessed by immunofluorescence, Western blot, mass spectrometry, and histological assays. Since steroids induce oxidative stress, the levels of reactive oxygen species and of redox related proteins were evaluated. Results—AFSC-EV were able to ameliorate the differentiation ability of HOB both in the case of pre-osteoblasts and when the differentiation process was affected by dexamethasone. Moreover, the viability was increased and parallelly apoptotic markers were reduced. The presence of EV positively modulated the redox unbalance due to dexamethasone. Conclusion—these findings demonstrated that EV from hAFSC have the ability to recover precursor cell potential and delay local bone loss in steroid-related osteoporosis.

Emergence of the Stem Cell Secretome in Regenerative Engineering

The secretome is defined as the set of molecules and biological factors that are secreted by cells into the extracellular space. In the past decade, secretome-based therapies have emerged as a promising approach to overcome the limitations associated with cell-based therapies for tissue and organ regeneration. Considering the growing number of recent publications related to secretome-based therapies, this review takes a step-by-step engineering approach to evaluate the role of the stem cell secretome in regenerative engineering. We discuss the functional benefits of the secretome, the techniques used to engineer the secretome and tailor its therapeutic effects, and the delivery systems and strategies that have been developed to use the secretome for tissue regeneration.

Biomaterials functionalized with MSC secreted extracellular vesicles and soluble factors for tissue regeneration

The therapeutic benefits of mesenchymal stromal cell (MSC) transplantation have been attributed to their secreted factors, including extracellular vesicles (EVs) and soluble factors. The potential of employing the MSC secretome as an alternative acellular approach to cell therapy is being investigated in various tissue injury indications, but EVs administered via bolus injections are rapidly sequestered and cleared. However, biomaterials offer delivery platforms to enhance EV retention rates and healing efficacy. In this review, we highlight the mechanisms underpinning the therapeutic effects of MSC-EVs and soluble factors as effectors of immunomodulation and tissue regeneration, conferred primarily via their nucleic acid and protein contents. We discuss how manipulating the cell culture microenvironment or genetic modification of MSCs can further augment the potency of their secretions. The most recent advances in the development of EV-functionalized biomaterials that mediate enhanced angiogenesis and cell survival, while attenuating inflammation and fibrosis, are presented. Finally, some technical challenges to be considered for the clinical translation of biomaterials carrying MSC-secreted bioactive cargo are discussed.

Restoring aged stem cell functionality: Current progress and future directions

Stem cell dysfunction is a hallmark of aging, associated with the decline of physical and cognitive abilities of humans and other mammals [Cell 2013;153:1194]. Therefore, it has become an active area of research within the aging and stem cell fields, and various techniques have been employed to mitigate the decline of stem cell function both in vitro and in vivo. While some techniques developed in model organisms are not directly translatable to humans, others show promise in becoming clinically relevant to delay or even mitigate negative phenotypes associated with aging. This review focuses on diet, treatment, and small molecule interventions that provide evidence of functional improvement in at least one type of aged adult stem cell.