Stem cell secretome, regeneration, and clinical translation: a narrative review

Proteins Derived From MRL/MpJ Tendon Provisional Extracellular Matrix and Secretome Promote Pro-Regenerative Tenocyte Behavior

Tendinopathies are prevalent musculoskeletal conditions that have no effective therapies to attenuate scar formation. In contrast to other adult mammals, the tendons of Murphy Roths Large (MRL/MpJ) mice possess a superior healing capacity following acute and overuse injuries. Here, we hypothesized that the application of biological cues derived from the local MRL/MpJ tendon environment would direct otherwise scar-mediated tenocytes towards a pro-regenerative MRL/MpJ-like phenotype. We identified soluble factors enriched in the secretome of MRL/MpJ tenocytes using bioreactor systems and quantitative proteomics. We then demonstrated that the combined administration of structural and soluble constituents isolated from decellularized MRL/MpJ tendon provisional ECM (dPECM) and the secretome stimulate scar-mediated rodent tenocytes towards enhanced mechanosensitivity, proliferation, intercellular communication, and ECM deposition associated with MRL/MpJ cell behavior. Our findings highlight key biological mechanisms that drive MRL/MpJ tenocyte activity and their interspecies utility to be harnessed for therapeutic strategies that promote pro-regenerative healing outcomes.

Teaser

Proteins enriched in a super-healer mouse strain elicit interspecies utility in promoting pro-regenerative tenocyte behavior.

Bioorthogonal non-canonical amino acid tagging to track transplanted human induced pluripotent stem cell-specific proteome

BACKGROUND

Human induced pluripotent stem cells (hiPSCs) and their differentiated cell types have a great potential for tissue repair and regeneration. While the primary focus of using hiPSCs has historically been to regenerate damaged tissue, emerging studies have shown a more potent effect of hiPSC-derived paracrine factors on tissue regeneration. However, the precise contents of the transplanted hiPSC-derived cell secretome are ambiguous. This is mainly due to the lack of tools to distinguish cell-specific secretome from host-derived proteins in a complex tissue microenvironment in vivo.

METHODS

In this study, we present the generation and characterization of a novel hiPSC line, L274G-hiPSC, expressing the murine mutant methionyl-tRNA synthetase, L274GMmMetRS, which can be used for tracking the cell specific proteome via biorthogonal non-canonical amino acid tagging (BONCAT). We assessed the trilineage differentiation potential of the L274G-hiPSCs in vitro and in vivo. Furthermore, we assessed the cell-specific proteome labelling in the L274G-hiPSC derived cardiomyocytes (L274G-hiPSC-CMs) in vitro following co-culture with wild type human umbilical vein derived endothelial cells and in vivo post transplantation in murine hearts.

RESULTS

We demonstrated that the L274G-hiPSCs exhibit typical hiPSC characteristics and that we can efficiently track the cell-specific proteome in their differentiated progenies belonging to the three germ lineages, including L274G-hiPSC-CMs. Finally, we demonstrated cell-specific BONCAT in transplanted L274G-hiPSC-CMs.

CONCLUSION

The novel L274G-hiPSC line can be used to study the cell-specific proteome of hiPSCs in vitro and in vivo, to delineate mechanisms underlying hiPSC-based cell therapies for a variety of regenerative medicine applications.

Insights into the role of mesenchymal stem cells in cutaneous medical aesthetics: from basics to clinics

With the development of the economy and the increasing prevalence of skin problems, cutaneous medical aesthetics are gaining more and more attention. Skin disorders like poor wound healing, aging, and pigmentation have an impact not only on appearance but also on patients with physical and psychological issues, and even impose a significant financial burden on families and society. However, due to the complexities of its occurrence, present treatment options cannot produce optimal outcomes, indicating a dire need for new and effective treatments. Mesenchymal stem cells (MSCs) and their secretomics treatment is a new regenerative medicine therapy that promotes and regulates endogenous stem cell populations and/or replenishes cell pools to achieve tissue homeostasis and regeneration. It has demonstrated remarkable advantages in several skin-related in vivo and in vitro investigations, aiding in the improvement of skin conditions and the promotion of skin aesthetics. As a result, this review gives a complete description of recent scientific breakthroughs in MSCs for skin aesthetics and the limitations of their clinical applications, aiming to provide new ideas for future research and clinical transformation.

Pretreatment with Inflammatory Factors Altered the Secretome of Human Amniotic Epithelial Cells

Human amniotic epithelial cells (hAECs) are novel and promising therapeutic agents for patients suffering from degenerative diseases. Studies have demonstrated that the therapeutic effects of hAECs mainly depend on their paracrine components. Currently, appropriate pretreatment is a widely confirmed strategy for enhancing the repair potential of stem cells; however, the effect of proinflammatory factor pretreatment on hAECs and their secretome is still unclear. In this study, we used the well-characterized proinflammatory factors tumor necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) to stimulate hAECs and analyzed the effect of TNF-α and IFN-γ on hAECs, including gene expression profile, paracrine proteins, and microRNAs (miRNAs) in exosomes. Results showed that TNF-α and IFN-γ pretreatment improved the viability of hAECs but inhibited the proliferation of hAECs. TNF-α and IFN-γ pretreatment altered the gene expression profile of hAECs, and upregulated differentially expressed genes were predominantly enriched in biological adhesion, antioxidant activity, and response to IFN-beta. In addition, TNF-α and IFN-γ pretreatment enhanced the paracrine secretion of cytokines by hAECs. The upregulated differentially expressed proteins were mainly enriched in tissue remodeling proteins and cytokine-cytokine receptor. Notably, the expression of miRNAs in exosomes from hAECs was also changed by TNF-α and IFN-γ pretreatment. The target genes of upregulated exosomal miRNAs substantially contributed to the response to stimulus, metabolic pathways, and PI3K-Akt signaling pathway. Our findings improve our understanding of the biological characteristics of hAECs after proinflammatory factor pretreatment and provide novel insights to strengthen and optimize the therapeutic potential of hAECs and their secretome in regenerative medicine.

Cervical tuberculosis treated with closed system abscess evacuation, and percutaneous laser disc decompression combined with secretome derived from umbilical cord mesenchymal stem cells: A case report

INTRODUCTION AND IMPORTANCE

Minimal invasive surgery is preferred as it offers the same benefit with less tissue damage, especially in the cervical area where a lot of critical structure resides. Mesenchymal stem cells (MSCs) and its secretome provide a promising regenerative intervention to damaged tissue. We report a cervical spinal tuberculosis case with hemiparesis treated with minimally invasive surgery combined with a regenerative approach.

CASE PRESENTATION

A 13-year-old boy presented with weakness in his left arm and left leg, accompanied by hemiparesthesia. The patient was unable to get up from bed, run, and jumpRadiology examination showed compression fracture, intervertebral disc retropulsion, spinal cord compression, and paravertebral cold abscess. The patient was treated with a single minimal invasive surgery consisting of closed system abscess evacuation, and percutaneous laser disc decompression combined with umbilical cord-derived mesenchymal stem cells.

CLINICAL DISCUSSION

The pain, weakness, and numbness were gone two days after surgery. The patient could carry out normal activities, even doing sports such as mini soccer and badminton. This clinical improvement was obtained as he carried out some procedures. The cold abscess aspiration removed infection focus which prevents further vertebra destruction, PLDD which decompresses the retropulsed discs, and implantation of MSCs and secretomes which regenerate and strengthen the destructed bone and surrounding tissue.

CONCLUSION

Closed system abscess evacuation, and percutaneous laser disc degeneration combined with secretome derived from UC-MSC are minimally-invasive strategies with promising results. Further studies are required to investigate its efficacy.

Engineering Innervated Musculoskeletal Tissues for Regenerative Orthopedics and Disease Modeling

Musculoskeletal (MSK) disorders significantly burden patients and society, resulting in high healthcare costs and productivity loss. These disorders are the leading cause of physical disability, and their prevalence is expected to increase as sedentary lifestyles become common and the global population of the elderly increases. Proper innervation is critical to maintaining MSK function, and nerve damage or dysfunction underlies various MSK disorders, underscoring the potential of restoring nerve function in MSK disorder treatment. However, most MSK tissue engineering strategies have overlooked the significance of innervation. This review first expounds upon innervation in the MSK system and its importance in maintaining MSK homeostasis and functions. This will be followed by strategies for engineering MSK tissues that induce post-implantation in situ innervation or are pre-innervated. Subsequently, research progress in modeling MSK disorders using innervated MSK organoids and organs-on-chips (OoCs) is analyzed. Finally, the future development of engineering innervated MSK tissues to treat MSK disorders and recapitulate disease mechanisms is discussed. This review provides valuable insights into the underlying principles, engineering methods, and applications of innervated MSK tissues, paving the way for the development of targeted, efficacious therapies for various MSK conditions.

Mesenchymal stem cell secretome for regenerative medicine: Where do we stand?

BACKGROUND

Mesenchymal stem cell (MSC)-based therapies have yielded beneficial effects in a broad range of preclinical models and clinical trials for human diseases. In the context of MSC transplantation, it is widely recognized that the main mechanism for the regenerative potential of MSCs is not their differentiation, with in vivo data revealing transient and low engraftment rates. Instead, MSCs therapeutic effects are mainly attributed to its secretome, i.e., paracrine factors secreted by these cells, further offering a more attractive and innovative approach due to the effectiveness and safety of a cell-free product.

AIM OF REVIEW

In this review, we will discuss the potential benefits of MSC-derived secretome in regenerative medicine with particular focus on respiratory, hepatic, and neurological diseases. Both free and vesicular factors of MSC secretome will be detailed. We will also address novel potential strategies capable of improving their healing potential, namely by delivering important regenerative molecules according to specific diseases and tissue needs, as well as non-clinical and clinical studies that allow us to dissect their mechanisms of action.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MSC-derived secretome includes both soluble and non-soluble factors, organized in extracellular vesicles (EVs). Importantly, besides depending on the cell origin, the characteristics and therapeutic potential of MSC secretome is deeply influenced by external stimuli, highlighting the possibility of optimizing their characteristics through preconditioning approaches. Nevertheless, the clarity around their mechanisms of action remains ambiguous, whereas the need for standardized procedures for the successful translation of those products to the clinics urges.

Subcutaneous injection of adipose stromal cell-secretome improves renal function and reduces inflammation in established acute kidney injury

BACKGROUND

Adipose stromal cells (ASC) are a form of mesenchymal stromal cells that elicit effects primarily via secreted factors, which may have advantages for the treatment of injury or disease. Several previous studies have demonstrated a protective role for MSC/ASC on mitigating acute kidney injury but whether ASC derived factors could hasten recovery from established injury has not been evaluated.

METHODS

We generated a concentrated secretome (CS) of human ASC under well-defined conditions and evaluated its ability to improve the recovery of renal function in a preclinical model of acute kidney injury (AKI) in rats. 24 h following bilateral ischemia/reperfusion (I/R), rats were randomized following determination of plasma creatinine into groups receiving vehicle -control or ASC-CS treatment by subcutaneous injection (2 mg protein/kg) and monitored for evaluation of renal function, structure and inflammation.

RESULTS

Renal function, assessed by plasma creatinine levels, recovered faster in ASC-CS treated rats vs vehicle. The most prominent difference between the ASC-CS treated vs vehicle was observed in rats with the most severe degree of initial injury (Pcr > 3.0 mg/dl 24 h post I/R), whereas rats with less severe injury (Pcr < 2.9 mg/dl) recovered quickly regardless of treatment. The quicker recovery of ASC-treated rats with severe injury was associated with less tissue damage, inflammation, and lower plasma angiopoietin 2. In vitro, ASC-CS attenuated the activation of the Th17 phenotype in lymphocytes isolated from injured kidneys.

CONCLUSIONS

Taken together, these data suggest that ASC-CS represents a potent therapeutic option to improve established AKI.

Modulating the release of bioactive molecules of human mesenchymal stromal cell secretome: Heparinization of hyaluronic acid-based hydrogels

An amine derivative of hyaluronic acid (HA) was crosslinked to obtain a 3D dried sponge. The sponge was subsequently rehydrated using secretome from human mesenchymal stromal cells (MSCs), resulting in the formation of a hydrogel. The release kinetics analysis demonstrated that the hydrogel effectively sustained secretome release, with 70% of the initially loaded wound-healing-associated cytokines being released over a 12-day period. Tuning the hydrogel properties through heparin crosslinking resulted in a biomaterial with a distinct mechanism of action. Specifically, the presence of heparin enhanced water uptake capacity of the hydrogel and increased its sensitivity to enzymatic degradation. Notably, the heparin crosslinking also led to a significant retention of cytokines within the hydrogel matrix. Overall, the secretome-rehydrated HA hydrogel holds promise as a versatile device for regenerative medicine applications: the non-heparinized hydrogel may function as a biomaterial with low reabsorption rates, sustaining the release of bioactive molecules contained in MSC secretome. In contrast, the heparinized hydrogel may serve as a depot of bioactive molecules with faster reabsorption rates. Given its patch-like characteristic, the HA-based hydrogel appears suitable as topical treatment for external organs, such as the skin.

The Immunoregulatory and Regenerative Potential of Activated Human Stem Cell Secretome Mitigates Acute-on-Chronic Liver Failure in a Rat Model

Acute-on-chronic liver failure (ACLF) is a syndrome marked by sudden liver function decline and multiorgan failure, predominantly acute kidney injury (AKY), in patients with chronic liver disease. Unregulated inflammation is a hallmark of ACLF; however, the key drivers of ACLF are not fully understood. This study explores the therapeutic properties of human mesenchymal stem cell (MSC) secretome, particularly focusing on its enhanced anti-inflammatory and pro-regenerative properties after the in vitro preconditioning of the cells. We evaluated the efficacy of the systemic administration of MSC secretome in preventing liver failure and AKI in a rat ACLF model where chronic liver disease was induced using by the administration of porcine serum, followed by D-galN/LPS administration to induce acute failure. After ACLF induction, animals were treated with saline (ACLF group) or MSC-derived secretome (ACLF-secretome group). The study revealed that MSC-secretome administration strongly reduced liver histological damage in the ACLF group, which was correlated with higher hepatocyte proliferation, increased hepatic and systemic anti-inflammatory molecule levels, and reduced neutrophil and macrophage infiltration. Additionally, renal examination revealed that MSC-secretome treatment mitigated tubular injuries, reduced apoptosis, and downregulated injury markers. These improvements were linked to increased survival rates in the ACLF-secretome group, endorsing MSC secretomes as a promising therapy for multiorgan failure in ACLF.

The Combined Effects on Human Dental Pulp Stem Cells of Fast-Set or Premixed Hydraulic Calcium Silicate Cements and Secretome Regarding Biocompatibility and Osteogenic Differentiation

An important part of regenerative endodontic procedures involving immature permanent teeth is the regeneration of the pulp-dentin complex with continuous root development. Hydraulic calcium silicate cements (HCSCs) are introduced for the pulpal treatment of immature permanent teeth. The stem-cell-derived secretome recently has been applied for the treatment of various damaged tissues. Here, we evaluated the biocompatibility and osteogenic differentiation of HCSCs combined with secretome on human dental pulp stem cells. In the Cell Counting Kit-8 test and wound healing assays, significantly higher cell viability was observed with secretome application. In alkaline phosphatase analysis, the activity was significantly higher with secretome application in all groups, except for RetroMTA on day 2 and Endocem MTA Premixed on day 4. In an Alizarin Red S staining analysis, all groups with secretome application had significantly higher staining values. Quantitative real-time polymerase chain reaction results showed that the day 7 expression of OSX significantly increased with secretome application in all groups. SMAD1 and DSPP expression also increased significantly with secretome addition in all groups except for Biodentine. In conclusion, HCSCs showed favorable biocompatibility and osteogenic ability and are predicted to demonstrate greater synergy with the addition of secretome during regenerative endodontic procedures involving immature permanent teeth.

Secretome Analysis: Reading Cellular Sign Language to Understand Intercellular Communication

A significant portion of mammalian proteomes is secreted to the extracellular space to fulfill crucial roles in cell-to-cell communication. To best recapitulate the intricate and multi-faceted crosstalk between cells in a live organism, there is an ever-increasing need for methods to study protein secretion in model systems that include multiple cell types. In addition, posttranslational modifications further expand the complexity and versatility of cellular communication. This review aims to summarize recent strategies and model systems that employ cellular coculture, chemical biology tools, protein enrichment, and proteomic methods to characterize the composition and function of cellular secretomes. This is all geared towards gaining better understanding of organismal biology in vivo mediated by secretory signaling.

Strategies to improve the therapeutic efficacy of mesenchymal stem cell-derived extracellular vesicle (MSC-EV): a promising cell-free therapy for liver disease

Liver disease has emerged as a significant worldwide health challenge due to its diverse causative factors and therapeutic complexities. The majority of liver diseases ultimately progress to end-stage liver disease and liver transplantation remains the only effective therapy with the limitations of donor organ shortage, lifelong immunosuppressants and expensive treatment costs. Numerous pre-clinical studies have revealed that extracellular vesicles released by mesenchymal stem cells (MSC-EV) exhibited considerable potential in treating liver diseases. Although natural MSC-EV has many potential advantages, some characteristics of MSC-EV, such as heterogeneity, uneven therapeutic effect, and rapid clearance in vivo constrain its clinical translation. In recent years, researchers have explored plenty of ways to improve the therapeutic efficacy and rotation rate of MSC-EV in the treatment of liver disease. In this review, we summarized current strategies to enhance the therapeutic potency of MSC-EV, mainly including optimization culture conditions in MSC or modifications of MSC-EV, aiming to facilitate the development and clinical application of MSC-EV in treating liver disease.

Mesenchymal stem cell secretome ameliorates over-expression of soluble fms-like tyrosine kinase-1 (sFlt-1) and fetal growth restriction (FGR) in animal SLE model

INTRODUCTION

In the near future, stem cell research may lead to several major therapeutic innovations in medical practice. Secretome, a "by-product" of stem cell line cultures, has many advantages. Its easiness of storage, usage, and fast direct effect are some of those to consider. Fetal growth restriction (FGR) remains one of the significant challenges in maternal-fetal and neonatal medicine. Placentation failure is one of the most profound causal and is often related to increasing sFlt-1 in early pregnancy. This study aimed to investigate hUC-MSC secretome in ameliorating sFlt-1 and how to improve outcomes in preventing FGR in an animal model.

MATERIALS AND METHODS

Pristane-induced systemic lupus erythematosus (SLE) in a mouse model was used to represent placentation failure and its consequences. Twenty-one mice were randomized into three groups: (I) normal pregnancy, (II) SLE, and (III) SLE with secretome treatment. Pristane was administered in all Groups four weeks prior mating period. Secretome was derived from human umbilical cord mesenchymal stem cells (hUC-MSC) conditioned medium on the 3rd and 4th passage, around day-21 until day-28 from the start of culturing process. Mesenchymal stem cell was characterized using flow cytometry for CD105+, CD90+, and CD73+ surface antigen markers. Immunohistochemistry anlysis by using Remmele's Immunoreactive Score (IRS) was used to quantify the placental sFlt-1 expression in each group. Birth weight and length were analyzed as the secondary outcome. The number of fetuses obtained was also calculated for pregnancy loss comparison between Groups.

RESULTS

The administration of secretome of hUC-MSC was found to lower the expression of the placental sFlt-1 significantly in the pristane SLE animal model (10.30 ± 1.40 vs. 4.98 ± 2.57; p < 0.001) to a level seen in normal mouse pregnancies in Group I (3.88 ± 0.49; p = 0.159). Secretome also had a significant effect on preventing fetal growth restriction in the pristane SLE mouse model (birth weight: 354.29 ± 80.76 mg vs. 550 ± 64.03 mg; p < 0.001 and birth length: 14.43 ± 1.27 mm vs. 19.00 ± 1.41 mm), comparable to the birth weight and length of the normal pregnancy in Group I (540.29 ± 75.47 mg and 18.14 ± 1.34 mm, p = 0.808 and = 0.719). Secretome administration also showed a potential action to prevent high number of pregnancy loss as the number of fetuses obtained could be similar to those of mice in the normal pregnant Group (7.71 ± 1.11 vs. 7.86 ± 1.06; p = 0.794).

CONCLUSIONS

Administration of secretome lowers sFlt-1 expression in placenta, improves fetal growth, and prevents pregnancy loss in a mouse SLE model.

TNF-α and IFN-γ prestimulation enhances the therapeutic efficacy of human amniotic epithelial stem cells in chemotherapy-induced ovarian dysfunction

BACKGROUND

Exposure to a harsh ovarian microenvironment induced by chemotherapeutic agents seriously affects the remodeling of ovarian function and follicular development, leading to premature ovarian failure or insufficiency (POF/POI). For decades, the effectiveness of stem cell therapies in POI animal models has been intensively studied; however, strategies to enhance the therapeutic effect of stem cells remain challenging.

METHODS

In this study, we first observed the pathological changes of the ovaries at different time points during chemotherapy, including the number of follicles, granulosa cell proliferation, oxidative stress damage, ovarian fibrosis, and inflammatory reaction. Moreover, we investigated whether activated hAECs stimulated by the proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) were more effective than native hAECs in repairing ovarian injury induced by chemotherapy.

RESULTS

The inhibitory effect of chemotherapy drugs on ovarian granulosa cells (GCs) in growing follicles mainly occurred on day 3 after chemotherapy in a mouse model. Then, continued ovarian injury, including oxidative damage and cell death cascades, resulted in the depletion of follicular reserves and inflammation-related ovarian fibrosis. Cytokine array demonstrated that activated hAECs secreted high levels of paracrine cytokines related to extracellular matrix (ECM) remodeling, angiogenesis, and immunomodulation. An in vivo study showed that the engraftment rate of activated hAECs in damaged ovaries was higher than that of native hAECs. Furthermore, activated hAECs in damaged ovaries had significantly upregulated expression of the antioxidant proteins thioredoxin1/2. In addition, activated hAECs had increased numbers of mature follicles and ameliorated the ovarian microenvironment by promoting angiogenesis and reducing ovarian fibrosis.

CONCLUSIONS

These results indicated that secondary ovarian damage induced by chemotherapy, including oxidative stress damage, chronic inflammatory response, and ovarian tissue fibrosis should be attended. Prestimulation with the proinflammatory factors TNF-α and IFN-γ could enhance the therapeutic efficacy of hAECs against chemotherapy-induced ovarian dysfunction, which may become a new feasible strategy to improve the therapeutic potential of hAECs in regenerative medicine.

Secretome as a Tool to Treat Neurological Conditions: Are We Ready?

Due to their characteristics, mesenchymal stem cells (MSCs) are considered a potential therapy for brain tissue injury or degeneration. Nevertheless, despite the promising results observed, there has been a growing interest in the use of cell-free therapies in regenerative medicine, such as the use of stem cell secretome. This review provides an in-depth compilation of data regarding the secretome composition, protocols used for its preparation, as well as existing information on the impact of secretome administration on various brain conditions, pointing out gaps and highlighting relevant findings. Moreover, due to the ability of MSCs to respond differently depending on their microenvironment, preconditioning of MSCs has been used to modulate their composition and, consequently, their therapeutic potential. The different strategies used to modulate the MSC secretome were also reviewed. Although secretome administration was effective in improving functional impairments, regeneration, neuroprotection, and reducing inflammation in brain tissue, a high variability in secretome preparation and administration was identified, compromising the transposition of preclinical data to clinical studies. Indeed, there are no reports of the use of secretome in clinical trials. Despite the existing limitations and lack of clinical data, secretome administration is a potential tool for the treatment of various diseases that impact the CNS.

Revolutionizing orofacial pain management: the promising potential of stem cell therapy

Orofacial pain remains a significant health issue in the United States. Pain originating from the orofacial region can be composed of a complex array of unique target tissue that contributes to the varying success of pain management. Long-term use of analgesic drugs includes adverse effects such as physical dependence, gastrointestinal bleeding, and incomplete efficacy. The use of mesenchymal stem cells for their pain relieving properties has garnered increased attention. In addition to the preclinical and clinical results showing stem cell analgesia in non-orofacial pain, studies have also shown promising results for orofacial pain treatment. Here we discuss the outcomes of mesenchymal stem cell treatment for pain and compare the properties of stem cells from different tissues of origin. We also discuss the mechanism underlying these analgesic/anti-nociceptive properties, including the role of immune cells and the endogenous opioid system. Lastly, advancements in the methods and procedures to treat patients experiencing orofacial pain with mesenchymal stem cells are also discussed.

Engineered adult stem cells: Current clinical trials status of disease treatment

Regenerative medicine is an interdisciplinary field involving the process of replacing and regenerating cells/tissues or organs by integrating medicine, science, and engineering principles to enhance the intrinsic regenerative capacity of the host. Recently, engineered adult stem cells have gained attention for their potential use in regenerative medicine by reducing inflammation and modulating the immune system. This chapter introduces adult stem cell engineering and chimeric antigen receptor T cells (CAR T) gene therapy and summarises current engineered stem cell- and extracellular vesicles (EVs)-focused clinical trial studies that provide the basis for the proposal of a personalised medicine approach to diseases diagnosis and treatment.

Comparing the healing properties of intra-articular injection of human dental pulp stem cells and cell-free-secretome on induced knee osteoarthritis in male rats

OBJECTIVE

Osteoarthritis (OA) is a common and painful joint disease with multifactorial causes. Stem cells, due to their high ability to reproduce and differentiate, have created a new horizon in tissue engineering of cartilage and bone. Secretions are one of the new therapies that can be used with stem cells or separately. This study aimed to compare the healing effects of human dental pulp stem cells, cell-free secretome, and human dental pulp mesenchymal stem cells with secretome in the induced OA in male rats.

METHODS

Dental pulp mesenchymal stem cells were isolated and prepared from human dental pulp. The collagenase type II was injected into the knee of twenty-five male Sprague-Dawley rats, and after 10 weeks, OA was confirmed. Rats were divided into five groups (n = 5): 1) Human dental pulp stem cells plus secretome (HDP+Sec); 2) Human dental pulp stem cells (HDP); 3) Secretome (Sec); 4) Hyalgan as the positive control (Hya); 5) No treatment as the negative control (Ctrl). After 12 weeks since OA was confirmed, the healing process was examined by histopathology and radiology evaluations.

RESULTS

Histopathological evaluations, radiological assessments, and matrix indexes in three treatment groups significantly improved compared to the Ctrl and Hya groups. Surface in HDP+Sec was significantly better than the Ctrl group. In radiological evaluations, a significant decrease in OA was observed in the three treatment groups in comparison with the Ctrl groups. There was no significant difference between the treatment groups in any radiological and histopathological evaluations. HDP + Sec group slightly records better results compared to Sec or HDP treatment groups.

CONCLUSION

It was concluded that human dental pulp stem cells and their secretome promote cartilage regeneration due to their cell protective potential as well as matrix degeneration reduction capacity.

Human Neuromuscular Junction on a Chip: Impact of Amniotic Fluid Stem Cell Extracellular Vesicles on Muscle Atrophy and NMJ Integrity

Neuromuscular junctions (NMJs) are specialized synapses, crucial for the communication between spinal motor neurons (MNs) and skeletal muscle. NMJs become vulnerable in degenerative diseases, such as muscle atrophy, where the crosstalk between the different cell populations fails, and the regenerative ability of the entire tissue is hampered. How skeletal muscle sends retrograde signals to MNs through NMJs represents an intriguing field of research, and the role of oxidative stress and its sources remain poorly understood. Recent works demonstrate the myofiber regeneration potential of stem cells, including amniotic fluid stem cells (AFSC), and secreted extracellular vesicles (EVs) as cell-free therapy. To study NMJ perturbations during muscle atrophy, we generated an MN/myotube co-culture system through Xona^TM microfluidic devices, and muscle atrophy was induced in vitro by Dexamethasone (Dexa). After atrophy induction, we treated muscle and MN compartments with AFSC-derived EVs (AFSC-EVs) to investigate their regenerative and anti-oxidative potential in counteracting NMJ alterations. We found that the presence of EVs reduced morphological and functional in vitro defects induced by Dexa. Interestingly, oxidative stress, occurring in atrophic myotubes and thus involving neurites as well, was prevented by EV treatment. Here, we provided and validated a fluidically isolated system represented by microfluidic devices for studying human MN and myotube interactions in healthy and Dexa-induced atrophic conditions-allowing the isolation of subcellular compartments for region-specific analyses-and demonstrated the efficacy of AFSC-EVs in counteracting NMJ perturbations.

Extracellular Vesicles from Human Umbilical Cord-Derived MSCs Affect Vessel Formation In Vitro and Promote VEGFR2-Mediated Cell Survival

Mesenchymal stromal cell (MSC)-derived extracellular vesicles (EVs) have emerged as novel tools in regenerative medicine. Angiogenesis modulation is widely studied for the treatment of ischaemic diseases, wound healing, and tissue regeneration. Here, we have shown that EVs from human umbilical cord-derived MSCs can affect VEGFR2 signalling, a master regulator of angiogenesis homeostasis, via altering the phosphorylation of AKT. This translates into an inhibition of apoptosis, promoting exclusively cell survival, but not proliferation, in human microvascular endothelial cells. Interestingly, when comparing EVs from normoxic cells to those obtained from hypoxia (1% O₂) preconditioned cells, hypoxia-derived EVs appear to have a slightly enhanced effect. Furthermore, when studied in a longer term endothelial-fibroblast co-culture angiogenesis model in vitro, both EV populations demonstrated a positive effect on vessel formation, evidenced by increased vessel networks with tubes of significantly larger diameters. Our data reveals that EVs selectively target components of the angiogenic pathway, promoting VEGFR2-mediated cell survival via enhancement of AKT activation. Our data show that EVs are able to enhance specific components of the VEGF signalling pathway and may have therapeutic potential to support endothelial cell survival.

The non-protein fraction of embryonic stem cell secretome has antibacterial effects against antibiotic-resistant strains of bacteria

In recent years, the search for new antibacterial agents has been shown to be extremely important, as the burgeoning problem of antibiotic resistance and the toxicity of many antimicrobial compounds has forced scientists to turn their attention to alternatives. Searching stem cell secretomes, including the non-protein part, for new antimicrobials is a promising area of current research. We investigated the effect of the non-protein part of an embryonic stem cell secretome on various bacterial strains, including antibiotic-resistant ones. The non-protein fraction of the stem cell secretome was obtained by preparative high-performance liquid chromatography. Bactericidal activity was tested against eight museum strains and 206 clinical strains of bacteria by comparing the secretomes effects on growth of bacterial cultures. The museum strains showed some dose-dependent effects at concentrations of 25-100 g/ml. Against the clinical strains of Gram-negative microorganisms of different species, some bactericidal activity was shown at a concentration of 100 g/ml, but sensitivity of bacteria to the secretome fraction varied, with growth stimulation being detected in some strains. Application of higher concentrations of 100-1000 g/ml showed no dose-dependent effect. The clinical strains of E. coli and P. aeruginosa were shown to have reduced bactericidal activity after one day of incubation. Thus, this study has shown that the non-protein fraction of the embryonic stem cell secretome has bactericidal effects against some strains. However, more detailed studies are needed to identify the mechanism of action and to determine the most effective dose and frequency of administration.

Efficacy of Mesenchymal Stem Cells from Human Exfoliated DeciduousTeeth and their Derivatives in Inflammatory Diseases Therapy

Mesenchymal stem cells derived from postnatal orofacial tissues can be readily isolated and possess diverse origins, for example, from surgically removed teeth or gingiva. These cells exhibit stem cell properties, strong potential for self-renewal, and show multi-lineage differentiation, and they have therefore been widely employed in stem cell therapy, tissue regeneration, and inflammatory diseases. Among them, stem cells from human exfoliated deciduous teeth [SHED] and their derivatives have manifested wide application in the treatment of diseases because of their outstanding advantages- including convenient access, easy storage, and less immune rejection. Numerous studies have shown that most diseases are closely associated with inflammation and that inflammatory diseases are extremely destructive, can lead to necrosis of organ parenchymal cells, and can deposit excessive extracellular ma- trix in the tissues. Inflammatory diseases are thus the principal causes of disability and death from many diseases worldwide. SHED and their derivatives not only exhibit the basic characteristics of stem cells but also exhibit some special properties of their own, particularly with regard to their great potential in inhib- iting inflammation and tissue regeneration. SHED therapy may provide a new direction for the treatment of inflammation and corresponding tissue defects. In this review, we critically analyze and summarize the latest findings on the behaviors and functions of SHED, serum‑free conditioned medium from SHED [SHED-CM], and extracellular vesicles, especially exosomes, from SHED [SHED-Exos], and discuss their roles and underlying mechanisms in the control of inflammatory diseases, thus further highlighting additional functions for SHED and their derivatives in future therapies.

Identifying the Efficacy of Extracellular Vesicles in Osteogenic Differentiation: An EV-Lution in Regenerative Medicine

Mesenchymal stromal cells (MSCs) have long been the focus for regenerative medicine and the restoration of damaged or aging cells throughout the body. However, the efficacy of MSCs in cell-based therapy still remains unpredictable and carries with it enumerable risks. It is estimated that only 3-10% of MSCs survive transplantation, and there remains undefined and highly variable heterogeneous biological potency within these administered cell populations. The mode of action points to secreted factors produced by MSCs rather than the reliance on engraftment. Hence harnessing such secreted elements as a replacement for live-cell therapies is attractive. Extracellular vesicles (EVs) are heterogenous lipid bounded structures, secreted by cells. They comprise a complex repertoire of molecules including RNA, proteins and other factors that facilitate cell-to-cell communication. Described as protected signaling centers, EVs can modify the cellular activity of recipient cells and are emerging as a credible alternative to cell-based therapies. EV therapeutics demonstrate beneficial roles for wound healing by preventing apoptosis, moderating immune responses, and stimulating angiogenesis, in addition to promoting cell proliferation and differentiation required for tissue matrix synthesis. Significantly, EVs maintain their signaling function following transplantation, circumventing the issues related to cell-based therapies. However, EV research is still in its infancy in terms of their utility as medicinal agents, with many questions still surrounding mechanistic understanding, optimal sourcing, and isolation of EVs for regenerative medicine. This review will consider the efficacy of using cell-derived EVs compared to traditional cell-based therapies for bone repair and regeneration. We discuss the factors to consider in developing productive lines of inquiry and establishment of standardized protocols so that EVs can be harnessed from optimal secretome production, to deliver reproducible and effective therapies.

New Perspectives to Improve Mesenchymal Stem Cell Therapies for Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is one of the leading causes of acute liver injury. Many factors may contribute to the susceptibility of patients to this condition, making DILI a global medical problem that has an impact on public health and the pharmaceutical industry. The use of mesenchymal stem cells (MSCs) has been at the forefront of regenerative medicine therapies for many years, including MSCs for the treatment of liver diseases. However, there is currently a huge gap between these experimental approaches and their application in clinical practice. In this concise review, we focus on the pathophysiology of DILI and highlight new experimental approaches conceived to improve cell-based therapy by the in vitro preconditioning of MSCs and/or the use of cell-free products as treatment for this liver condition. Finally, we discuss the advantages of new approaches, but also the current challenges that must be addressed in order to develop safer and more effective procedures that will allow cell-based therapies to reach clinical practice, enhancing the quality of life and prolonging the survival time of patients with DILI.

Adipogenesis or osteogenesis: destiny decision made by mechanical properties of biomaterials

Regenerative medicine affords an effective approach for restoring defect-associated diseases, and biomaterials play a pivotal role as cell niches to support the cell behavior and decide the destiny of cell differentiation. Except for chemical inducers, mechanical properties such as stiffness, pore size and topography of biomaterials play a crucial role in the regulation of cell behaviors and functions. Stiffness may determine the adipogenesis or osteogenesis of mesenchymal stem cells (MSCs) via the translocation of yes-associated protein (YAP) and the transcriptional coactivator with a PDZ-binding motif (TAZ). External forces transmit through cytoskeleton reorientation to assist nuclear deformation and molecule transport, meanwhile, signal pathways including the Hippo, FAK/RhoA/ROCK, and Wnt/β-catenin have been evidenced to participate in the mechanotransduction. Different pore sizes not only tailor the scaffold stiffness but also conform to the requirements of cell migration and vessels in-growth. Topography guides cell geometry along with mobility and determines the cell fate ascribed to micro/nano-scale contact. Herein, we highlight the recent progress in exploring the regulation mechanism by the physical properties of biomaterials, which might lead to more innovative regenerative strategies for adipose or bone tissue repair.

Regenerative medicine affords an effective approach for restoring defect-associated diseases, and biomaterials play a pivotal role as cell niches to support the cell behavior and decide the destiny of cell differentiation.

Dental Pulp Stem Cell-Derived Secretome and Its Regenerative Potential

The therapeutic potential of the dental pulp stem (DSC) cell-derived secretome, consisting of various biomolecules, is undergoing intense research. Despite promising in vitro and in vivo studies, most DSC secretome-based therapies have not been implemented in human medicine because the paracrine effect of the bioactive factors secreted by human dental pulp stem cells (hDPSCs) and human exfoliated deciduous teeth (SHEDs) is not completely understood. In this review, we outline the current data on the hDPSC- and SHED-derived secretome as a potential candidate in the regeneration of bone, cartilage, and nerve tissue. Published reports demonstrate that the dental MSC-derived secretome/conditional medium may be effective in treating neurodegenerative diseases, neural injuries, cartilage defects, and repairing bone by regulating neuroprotective, anti-inflammatory, antiapoptotic, and angiogenic processes through secretome paracrine mechanisms. Dental MSC-secretomes, similarly to the bone marrow MSC-secretome activate molecular and cellular mechanisms, which determine the effectiveness of cell-free therapy. Many reports emphasize that dental MSC-derived secretomes have potential application in tissue-regenerating therapy due to their multidirectional paracrine effect observed in the therapy of many different injured tissues.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Potential Therapeutic Strategy for Acute Kidney Injury

Acute kidney injury (AKI) is a common and potential life-threatening disease in patients admitted to hospital, affecting 10%-15% of all hospitalizations and around 50% of patients in the intensive care unit. Severe, recurrent, and uncontrolled AKI may progress to chronic kidney disease or end-stage renal disease. AKI thus requires more efficient, specific therapies, rather than just supportive therapy. Mesenchymal stem cells (MSCs) are considered to be promising cells for cellular therapy because of their ease of harvesting, low immunogenicity, and ability to expand in vitro. Recent research indicated that the main therapeutic effects of MSCs were mediated by MSC-derived extracellular vesicles (MSC-EVs). Furthermore, compared with MSCs, MSC-EVs have lower immunogenicity, easier storage, no tumorigenesis, and the potential to be artificially modified. We reviewed the therapeutic mechanism of MSCs and MSC-EVs in AKI, and considered recent research on how to improve the efficacy of MSC-EVs in AKI. We also summarized and analyzed the potential and limitations of EVs for the treatment of AKI to provide ideas for future clinical trials and the clinical application of MSC-EVs in AKI.