All-trans retinoic acid preconditioning enhances proliferation, angiogenesis and migration of mesenchymal stem cell in vitro and enhances wound repair in vivo

All-trans retinoic acid pretreatment of mesenchymal stem cells enhances the therapeutic effect on acute kidney injury

A promising new therapy option for acute kidney injury (AKI) is mesenchymal stem cells (MSCs). However, there are several limitations to the use of MSCs, such as low rates of survival, limited homing capacity, and unclear differentiation. In search of better therapeutic strategies, we explored all-trans retinoic acid (ATRA) pretreatment of MSCs to observe whether it could improve the therapeutic efficacy of AKI. We established a renal ischemia/reperfusion injury model and treated mice with ATRA-pretreated MSCs via tail vein injection. We found that AKI mice treated with ATRA-MSCs significantly improved renal function compared with DMSO-MSCs treatment. RNA sequencing screened that hyaluronic acid (HA) production from MSCs promoted by ATRA. Further validation by chromatin immunoprecipitation experiments verified that retinoic acid receptor RARα/RXRγ was a potential transcription factor for hyaluronic acid synthase 2. Additionally, an in vitro hypoxia/reoxygenation model was established using human proximal tubular epithelial cells (HK-2). After co-culturing HK-2 cells with ATRA-pretreated MSCs, we observed that HA binds to cluster determinant 44 (CD44) and activates the PI3K/AKT pathway, which enhances the anti-inflammatory, anti-apoptotic, and proliferative repair effects of MSCs in AKI. Inhibition of the HA/CD44 axis effectively reverses the renal repair effect of ATRA-pretreated MSCs. Taken together, our study suggests that ATRA pretreatment promotes HA production by MSCs and activates the PI3K/AKT pathway in renal tubular epithelial cells, thereby enhancing the efficacy of MSCs against AKI.

Preconditioning of MSCs for Acute Neurological Conditions: From Cellular to Functional Impact-A Systematic Review

This systematic review aims to gather evidence on the mechanisms triggered by diverse preconditioning strategies for mesenchymal stem cells (MSCs) and their impact on their potential to treat ischemic and traumatic injuries affecting the nervous system. The 52 studies included in this review report nine different types of preconditioning, namely, manipulation of oxygen pressure, exposure to chemical substances, lesion mediators or inflammatory factors, usage of ultrasound, magnetic fields or biomechanical forces, and culture in scaffolds or 3D cultures. All these preconditioning strategies were reported to interfere with cellular pathways that influence MSCs' survival and migration, alter MSCs' phenotype, and modulate the secretome and proteome of these cells, among others. The effects on MSCs' phenotype and characteristics influenced MSCs' performance in models of injury, namely by increasing the homing and integration of the cells in the lesioned area and inducing the secretion of growth factors and cytokines. The administration of preconditioned MSCs promoted tissue regeneration, reduced neuroinflammation, and increased angiogenesis and myelinization in rodent models of stroke, traumatic brain injury, and spinal cord injury. These effects were also translated into improved cognitive and motor functions, suggesting an increased therapeutic potential of MSCs after preconditioning. Importantly, none of the studies reported adverse effects or less therapeutic potential with these strategies. Overall, we can conclude that all the preconditioning strategies included in this review can stimulate pathways that relate to the therapeutic effects of MSCs. Thus, it would be interesting to explore whether combining different preconditioning strategies can further boost the reparative effects of MSCs, solving some limitations of MSCs' therapy, namely donor-associated variability.

Therapeutic Effects of Tretinoin and Caffeine-Treated Bone Marrow-Derived Mesenchymal Stem Cell on Immunological Features of Ulcerative Colitis: An Animal Model Study

Background

Ulcerative colitis (UC) is one of the inflammatory gastrointestinal diseases. It causes irritation, inflammation, and ulcers in the digestive tract. UC is distinguished clinically by abdominal and rectal pain and intestinal secretion abnormalities. Mesenchymal stem cell (MSC) therapy could be the underlying treatment for UC. This study aimed to compare the results of MSC therapy with tretinoin and caffeine in an animal model.

Materials and Methods

Sixty male BALB/c mice were randomly divided into six equal groups. Five groups were exposed to acetic acid-induced colitis, and one healthy negative control group was designed. The positive control group was UC-induced mouse model with no treatment. Besides, treatment groups were MSCs (n = 2×106) that received tretinoin and caffeine. The treatment group was given mesalazine orally. The decision to begin treatment was taken after monitoring the symptoms of the UC.

Results

MSCs, tretinoin, and caffeine-treated MSCs significantly decrease inflammatory cytokines (interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-α) and inflammatory mediators (myeloperoxidase (MPO) and nitric oxide (NO)) compared with the positive control group. However, the alleviated effects of tretinoin-treated MSCs significantly were more than those of MSCs and caffeine-treated MSCs.

Conclusion

MSC therapy is an effective option for UC and can prevent disease progression. The results represented a high developmental rate and simple cell application of MSC therapy in UC patients. Also, MSC therapy's ability for immunomodulation is strengthened by drugs that improve their microenvironment by binding to their receptors.

Adipose-derived mesenchymal stem cells cultured in serum-free medium attenuate acute contrast-induced nephropathy by exerting anti-apoptotic effects

BACKGROUND

Contrast-induced nephropathy (CIN) is a major clinical problem associated with acute kidney injury during hospitalization. However, effective treatments for CIN are currently lacking. Mesenchymal stem cells (MSCs) have protective effects against kidney injury by suppressing inflammation and fibrosis. We previously showed that MSCs cultured in serum-free medium (SF-MSCs) enhance their anti-inflammatory and anti-fibrotic effects. However, whether SF-MSCs potentiate their anti-apoptotic effects is unknown. Here, we investigated the effects of SF-MSCs on a CIN mouse model.

METHODS

To create CIN model mice, we removed right kidney at first. One week later, the left renal artery was clamped for 30 min to cause ischemia-reperfusion injury, and mice were injected with iohexol. Then the kidney received 10 Gy of irradiation, and MSCs or SF-MSCs were injected immediately. At 24 h post-injection, mice were sacrificed, and their blood and kidneys were collected to evaluate renal function, DNA damage, and apoptosis. In addition, apoptosis was induced in HEK-293 cells by irradiation and cells were treated with conditioned medium from MSCs or SF-MSCs.

RESULTS

Treatment of CIN model mice with SF-MSCs markedly improved renal function compared with MSCs treatment. Cleaved caspase-3 levels and TUNEL-positive cell numbers were strongly suppressed in CIN model mice treated with SF-MSCs compared with the findings in those treated with MSCs. γH2AX levels, a chromosome damage marker, were reduced by MSCs and further reduced by SF-MSCs. In addition, cleaved caspase-3 in irradiated HEK-293 cells was more strongly suppressed by conditioned medium from SF-MSCs than by that from MSCs. Secretion of epidermal growth factor (EGF) was enhanced by culturing MSCs in serum-free medium. Knockdown of EGF by siRNA attenuated the inhibitory effects of SF-MSCs on CIN-induced renal dysfunction and tubular apoptosis.

CONCLUSIONS

These findings strongly suggest that SF-MSCs improve CIN in model mice by exerting anti-apoptotic effects in a paracrine manner. Thus, SF-MSCs represent a potential novel therapy for CIN.

Hypoxic Extracellular Matrix Preserves Its Competence after Expansion of Human MSCs under Physiological Hypoxia In Vitro

Tissue-relevant O2 levels are considered as an important tool for the preconditioning of multipotent mesenchymal stromal cells (MSCs) for regenerative medicine needs. The present study investigated the quality and functions of the extracellular matrix (ECM) of MSCs under low O2 levels. Human adipose tissue-derived MSCs were continuously expanded under normoxia (20% O2, N) or "physiological" hypoxia (5% O2, Hyp). Decellularized ECM (dcECM) was prepared. The structure of the dcECM was analyzed using confocal laser and scanning electron microscopy. Collagen, dcECM-N, and dcECM-Hyp were recellularized with MSC-N and further cultured at normoxia. The efficacy of adhesion, spreading, growth, osteogenic potential, and paracrine activity of recellularized MSC-N were evaluated. At low O2, the dcECM showed an increased alignment of fibrillar structures and provided accelerated spreading of MSC-N, indicating increased dcECM-Hyp stiffness. We described O2-dependent "ECM-education" of MSC-N when cultured on dcECM-Hyp. This was manifested as attenuated spontaneous osteo-commitment, increased susceptibility to osteo-induction, and a shift in the paracrine profile. It has been suggested that the ECM after physiological hypoxia is able to ensure the maintenance of a low-commitment state of MSCs. DcECM, which preserves the competence of the natural microenvironment of cells and is capable of "educating" others, appears to be a prospective tool for guiding cell modifications for cell therapy and tissue engineering.

Mesenchymal Stem Cells-Derived Apoptotic Extracellular Vesicles (ApoEVs): Mechanism and Application in Tissue Regeneration

Mesenchymal stem cells (MSCs) are commonly used as a source for cellular therapy owing to their strong immunosuppressive and regenerative effects. However, MSCs undergo extensive apoptosis within a short period after transplantation. During apoptosis, MSCs generate several apoptotic extracellular vesicles (MSCs-ApoEVs). MSCs-ApoEVs are rich in miRNomes, metabolites, and proteomes. They are critical intercellular communication mediators that can exert different regulatory effects on recipient cells. MSCs-ApoEVs have been shown to promote regeneration in the skin, hair, bone, muscle, and vascular system, etc. This review describes the production, release, isolation, and functionality of ApoEVs in detail. Furthermore, we summarize the existing mechanisms of MSCs-ApoEVs used for tissue regeneration and evaluate the possible strategies for their clinical application.

Promotion of adipose stem cell transplantation using GelMA hydrogel reinforced by PLCL/ADM short nanofibers

Adipose-derived mesenchymal stem cells (ADSCs) show poor survival after transplantation, limiting their clinical application. In this study, a series of poly(l-lactide-co-ϵ-caprolactone) (PLCL)/acellular dermal matrix (ADM) nanofiber scaffolds with different proportions were prepared by electrospinning. By studying their morphology, hydrophilicity, tensile mechanics, and biocompatibility, PLCL/ADM nanofiber scaffolds with the best composition ratio (PLCL:ADM = 7:3) were selected to prepare short nanofibers. And based on this, injectable gelatin methacryloyl (GelMA) hydrogel loaded with PLCL/ADM short nanofibers (GelMA-Fibers) was constructed as a transplantation vector of ADSCs. ADSCs and GelMA-Fibers were co-cultured, and the optimal loading concentration of PLCL/ADM nanofibers was investigated by cell proliferation assay, live/dead cell staining, and cytoskeleton stainingin vitro. In vivoinvestigations were also performed by H&E staining, Oil red O staining, and TUNEL staining, and the survival and apoptosis rates of ADSCs transplantedin vivowere analyzed. It was demonstrated that GelMA-Fibers could effectively promote the proliferation of ADSCsin vitro. Most importantly, GelMA-Fibers increased the survival rate of ADSCs transplantation and decreased their apoptosis rate within 14 d. In conclusion, the constructed GelMA-Fibers would provide new ideas and options for stem cell tissue engineering and stem cell-based clinical therapies.

Mesenchymal stem cell licensing: enhancing MSC function as a translational approach for the treatment of tendon injury

Tendon injuries are common in both veterinary and human clinical patients and result in morbidity, pain, and lost athletic performance. Consequently, utilizing naturally occurring injuries in veterinary patients as a comparative model could inform the development of novel therapies and increase translation for the treatment of human tendon injuries. Mesenchymal stem cells (MSCs) have shown considerable efficacy for the treatment of experimental and clinical superficial digital flexor tendon injury in the horse; however, the reinjury rate following treatment can remain high and MSC efficacy in treating other tendons is less well known. Additionally, the translation of MSC therapy to human tendon injury has remained poor. Recent evidence indicates that naïve MSC function can be enhanced through exogenous stimulation or manipulation of their environment. This stimulation or activation, herein termed MSC licensing, markedly alters MSC functions associated with immunomodulation, extracellular matrix remodeling, vascular development, bioactive factor production, and endogenous stromal/progenitor cell support. Additionally, a variety of licensing strategies has proven to influence MSC-secreted factors that have positively influenced outcome parameters in both in vitro and in vivo disease models separate from musculoskeletal tissues. Therefore, identifying the optimal licensing strategy for MSCs could ultimately provide an avenue for reliable and repeatable treatment of a broad range of tendon injuries of both veterinary and human clinical patients. This article details current evidence on the effects of licensed MSCs in both in vitro and in vivo disease models of different species and provides commentary on how those effector functions identified may be translated to the treatment of tendon injuries.

Breaking the graft-versus-host-disease barrier: Mesenchymal stromal/stem cells as precision healers

Mesenchymal Stromal/Stem Cells (MSCs) are multipotent, non-hematopoietic progenitor cells with a wide range of immune modulation and regenerative potential which qualify them as a potential component of cell-based therapy for various autoimmune/chronic inflammatory ailments. Their immunomodulatory properties include the secretion of immunosuppressive cytokines, the ability to suppress T-cell activation and differentiation, and the induction of regulatory T-cells. Considering this and our interest, we here discuss the significance of MSC for the management of Graft-versus-Host-Disease (GvHD), one of the autoimmune manifestations in human. In pre-clinical models, MSCs have been shown to reduce the severity of GvHD symptoms, including skin and gut damage, which are the most common and debilitating manifestations of this disease. While initial clinical studies of MSCs in GvHD cases were promising, the results were variable in randomized studies. So, further studies are warranted to fully understand their potential benefits, safety profile, and optimal dosing regimens. Owing to these inevitable issues, here we discuss various mechanisms, and how MSCs can be employed in managing GvHD, as a cellular therapeutic approach for this disease.

Preconditioning adipose-derived mesenchymal stem cells with dimethyl fumarate promotes their therapeutic efficacy in the brain tissues of rats with Alzheimer's disease

AIM

Transplantation of mesenchymal stem cell (MSC) has been suggested to be a promising method for treating neurodegenerative conditions, including Alzheimer's disease (AD). However, the poor survival rate of transplanted MSCs has limited their therapeutic application. This study aimed to evaluate whether preconditioning MSCs with dimethyl fumarate (DMF), a Nrf2 inducer, could enhance MSC therapeutic efficacy in an amyloid-β (Aβ_1-42)-induced AD rat model.

METHODS

The survival and antioxidant capacity of MSCs treated with DMF were assessed in vitro. Aβ_1-42 intrahippocampal injection was used to create a rat model of AD. Following the transplantation of MSCs preconditioned with DMF and using the Morris blue maze test, spatial learning and memory were assessed. Using RT-qPCR, we evaluated the gene expression related to apoptosis and neurotrophins in the hippocampus region.

RESULTS

Treatment with DMF enhanced cell survival and Nrf2 protein expression in MSCs in vitro. Preconditioning with DMF also enhanced the efficacy of transplanted MSCs in rescuing learning and spatial memory deficits in Aβ-AD rats. Besides, DMF preconditioning enhanced the neuroprotective effect of transplanted MSCs in the hippocampus of rats treated with Aβ_1-42 by decreasing the expression of apoptotic markers (Bax, caspase 3, and cytochrome c), and elevating the expression of the anti-apoptotic marker Bcl2 and neurotrophins, including BDNF and NGF.

CONCLUSION

Preconditioning MSCs with DMF boosted the therapeutic efficacy of these cells; therefore, it could serve as a targeted strategy for increasing the therapeutic efficacy of MSCs in treating neurodegenerative disorders, including AD.

Application of mesenchymal stem cells (MSCs) in neurodegenerative disorders: History, findings, and prospective challenges

Over the past few decades, the application of mesenchymal stem cells has captured the attention of researchers and practitioners worldwide. These cells can be obtained from practically every tissue in the body and are used to treat a broad variety of conditions, most notably neurological diseases such as Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, and Alzheimer's disease. Studies are still being conducted, and the results of these studies have led to the identification of several different molecular pathways involved in the neuroglial speciation process. These molecular systems are closely regulated and interconnected due to the coordinated efforts of many components that make up the machinery responsible for cell signaling. Within the scope of this study, we compared and contrasted the numerous mesenchymal cell sources and their cellular features. These many sources of mesenchymal cells included adipocyte cells, fetal umbilical cord tissue, and bone marrow. In addition, we investigated whether these cells can potentially treat and modify neurodegenerative illnesses.

Sulfasalazine and Chromotrope 2B reduce oxidative stress in murine bone marrow-derived mesenchymal stem cells

BACKGROUND

With advancing age of stem cells, dysregulation of various processes at the cellular level occurs, thereby decreasing their regeneration potential. One of the changes that occurs during the aging process is the accumulation of reactive oxygen species (ROS), which accelerates the processes of cellular senescence and cell death. The aim of this study is to evaluate two antioxidant compounds; Chromotrope 2B and Sulfasalazine, for their antioxidant effects on young and old rat bone marrow mesenchymal stem cells (MSCs).

METHODS AND RESULTS

Oxidative stress was induced in MSCs by 5 µM dexamethasone for 96 h and the cells were treated with Chromotrope 2B or Sulfasalazine, 50 µM each. The effects of antioxidant treatment following oxidative stress induction was evaluated by transcriptional profiling of genes involved in the oxidative stress and telomere maintenance. Expression levels of Cat, Gpx7, Sod1, Dhcr24, Idh1, and Txnrd2 were found to be increased in young MSCs (yMSCs) as a result of oxidative stress, while Duox2, Parp1, and Tert1 expression were found to be decreased as compared to the control. In old MSCs (oMSCs), the expressions of Dhcr24, Txnrd2, and Parp1 increased, while that of Duox2, Gpx7, Idh1, and Sod1 decreased following oxidative stress. In both MSC groups, Chromotrope 2B prompted decrease in the ROS generation before and after the induction of oxidative stress. In oMSCs, ROS content was significantly reduced in the Sulfasalazine treated group.

CONCLUSION

Our findings suggest that both Chromotrope 2B and Sulfasalazine possess the potential to reduce the ROS content in both age groups, though the latter was found to be more potent. These compounds can be used to precondition MSCs to enhance their regenerative potential for future cell-based therapeutics.

M1 to M2 induction in macrophages using a retinoic acid-releasing mesenchymal stem cell scaffold

BACKGROUND

Modulation of macrophage polarization is required for effective tissue repair and regenerative therapies. Therapeutic modulation of macrophages from an inflammatory M1 to a fibrotic M2 phenotype could help in diseases, such as chronic wounds, which are stalled in a prolonged and heightened inflammatory stage within the wound healing process.

OBJECTIVE

This study evaluates the efficiency of a pullulan/gelatin nanofiber scaffold loaded with retinoic acid (RA) and adipose-derived mesenchymal stem cells (ASCs) to modulate M1 to M2 anti-inflammatory transition.

METHODS

Scaffolds were fabricated by electrospinning, and crosslinked using ethylene glycol diglycidyl ether (EGDE). Exposure of RA and/or ASCs to cultured macrophages have been shown to promote M1 to M2 transition. Pullulan was chosen as a scaffold material due to its ability to quench reactive oxygen species, key signaling molecules that play an important role in the progression of inflammation, as well as for its excellent mechanical properties. Gelatin was chosen as an additional scaffold component due to the presence of cell-binding motifs and its biocompatibility. Scaffold compositions examined were 75:25 and 50:50, pullulan:gelatin. The scaffolds were crosslinked in 1:70 and 1:50 EGDE:EtOH. The scaffold composition was determined via FTIR. For the present study, the 75:25 pullulan:gelatin crosslinked with 1:70 EGDE:EtOH, forming nanofibers 328 ± 47.9 nm (mean ± SD) in diameter, was chosen as the scaffold composition due to its lower degradation and release rate, which allows a sustained delivery of RA.

RESULTS

The scaffold composition degraded to approximately 80% after 14 days, with approximately 38% of the drug released after 7 days. THP-1 monocytic cells were induced into a M1 macrophage phenotype through stimulation with lipopolysaccharide (LPS) and gamma interferon (IFN-γ). These M1 macrophages were the exposed to scaffolds loaded with RA and ASCs, to induce differentiation to an M2 phenotype.

CONCLUSION

Gene expression quantitation by qPCR showed a reduction of M1 biomarkers, tumor necrosis factor alpha (TNFα) and interleukin 1β (IL1β), and an increase of M2 biomarker CCL22 after 2 days of exposure, suggesting successful M1 to M2 transition.

Guiding stem cells for cutaneous repair

The significance of mesenchymal stem cells (MSCs) for tissue repair and regeneration is widely recognized. The pleiotropic nature of MSCs is demonstrated by their potential for proliferation and differentiation, and paracrine secretions, thereby making them ideal candidates for cell replacement therapy. Tissue resident MSCs are engaged in homeostasis under normal wear and tear. However, stem cell therapy may be applicable if damage cannot be repaired by normal homeostatic mechanisms. The safety of MSCs has been clearly established in clinical trials but their efficacy remains questionable. The efficacy of MSCs depends on several factors, such as their viability, functional status in terms of secretome secretions, and the in-vivo scenario after transplantation. The performance of MSCs is regulated by their micro-environmental conditions and cues. The so-called MSC niche comprises physical, chemical, and biological components, which play key roles in determining the fate of MSCs. MSCs scaled up for transplantation purposes comprise a disorganized mass of cells, which needs to be directed to perform the required function. Thus, MSCs need to be directed toward an expected target activity in human patients. This review focuses on the various methods that can be used to guide stem cells for cutaneous repair.

Role of Mesenchymal Stem Cells and Their Paracrine Mediators in Macrophage Polarization: An Approach to Reduce Inflammation in Osteoarthritis

Osteoarthritis (OA) is a low-grade inflammatory disorder of the joints that causes deterioration of the cartilage, bone remodeling, formation of osteophytes, meniscal damage, and synovial inflammation (synovitis). The synovium is the primary site of inflammation in OA and is frequently characterized by hyperplasia of the synovial lining and infiltration of inflammatory cells, primarily macrophages. Macrophages play a crucial role in the early inflammatory response through the production of several inflammatory cytokines, chemokines, growth factors, and proteinases. These pro-inflammatory mediators are activators of numerous signaling pathways that trigger other cytokines to further recruit more macrophages to the joint, ultimately leading to pain and disease progression. Very few therapeutic alternatives are available for treating inflammation in OA due to the condition's low self-healing capacity and the lack of clear diagnostic biomarkers. In this review, we opted to explore the immunomodulatory properties of mesenchymal stem cells (MSCs) and their paracrine mediators-dependent as a therapeutic intervention for OA, with a primary focus on the practicality of polarizing macrophages as suppression of M1 macrophages and enhancement of M2 macrophages can significantly reduce OA symptoms.

MELTF Might Regulate Ferroptosis, Pyroptosis, and Autophagy in Platelet-Rich Plasma-Mediated Endometrial Epithelium Regeneration

The endometrial basal layer is essential for endometrial regeneration, whose disruption leads to thin endometrium or intrauterine adhesion (IUA) with an unsatisfactory prognosis. Emerging data indicate that platelet-rich plasma (PRP) can promote endometrial proliferation, but the mechanism by which PRP regulates endometrial regeneration remains unclear. Herein, we investigated the therapeutic effects and possible mechanisms of PRP on endometrial regeneration. IUA animal model was generated by sham, mechanically damaging endometrium with or without PRP for 10 days. The uterine section in the model group showed degenerative changes with a narrow endometrial lumen, atrophic columnar epithelium, decreased number of endometrial glands, decreased endometrial thickness, and increased collagen deposition. The above disruption could be ameliorated by the PRP. Transcriptome sequencing analysis displayed that the retinol metabolism pathway and extracellular matrix (ECM) receptor interaction pathway were up-regulated and enriched in differential expression genes (DEGs). Melanotransferrin (MELTF) was the key up-regulated gene in PRP-induced endometrial regeneration, which was verified in vivo and in vitro. Ferroptosis, autophagy, and pyroptosis were down-regulated in PRP-treated Ishikawa cells. Conclusively, PRP promotes endometrium regeneration by up-regulating the retinol metabolism and ECM receptor interaction pathway with MELTF. Meanwhile, PRP could also inhibit endometrial epithelial cell death by regulating ferroptosis, autophagy, and pyroptosis.

Promoting Immortalized Adipose-Derived Stem Cell Transdifferentiation and Proliferation into Neuronal-Like Cells through Consecutive 525 nm and 825 nm Photobiomodulation

Neuronal cells can be generated from adipose-derived stem cells (ADSCs) through biological or chemical inducers. Research has shown that this process may be optimized by the introduction of laser irradiation in the form of photobiomodulation (PBM) to cells. This in vitro study is aimed at generating neuronal-like cells with inducers, chemical or biological, and at furthermore treating these transdifferentiating cells with consecutive PBM of a 525 nm green (G) laser and 825 nm near-infrared (NIR) laser light with a fluence of 10 J/cm². Cells were exposed to induction type 1 (IT1): 3-isobutyl-1-methylxanthine (IBMX) (0.5 mM)+indomethacin (200 μM)+insulin (5 μg/ml) for 14 days, preinduced with β-mercaptoethanol (BME) (1 mM) for two days, and then incubated with IT2: β-hydroxyanisole (BHA) (100 μM)+retinoic acid (RA) (10-6 M)+epidermal growth factor (EGF) (10 ng/ml)+basic fibroblast growth factor (bFGF) (10 ng/ml) for 14 days and preinduced with β-mercaptoethanol (BME) (1 mM) for two days and then incubated with indomethacin (200 μM)+RA (1 μM)+forskolin (10 μM) for 14 days. The results were evaluated through morphological observations, viability, proliferation, and migration studies, 24 h, 48 h, and 7 days post-PBM. The protein detection of an early neuronal marker, neuron-specific enolase (NSE), and late, ciliary neurotrophic factor (CNTF), was determined with enzyme-linked immunosorbent assays (ELISAs). The genetic expression was also explored through real-time PCR. Results indicated differentiation in all experimental groups; however, cells that were preinduced showed higher proliferation and a higher differentiation rate than the group that was not preinduced. Within the preinduced groups, results indicated that cells treated with IT2 and consecutive PBM upregulated differentiation the most morphologically and physiologically.

Therapeutic potential of conditioned medium obtained from deferoxamine preconditioned umbilical cord mesenchymal stem cells on diabetic nephropathy model

Background

The therapeutic potential of mesenchymal stem cells (MSCs)-derived conditioned media (CM) can be increased after preconditioning with various chemical agents. The aim of this study is comparative evaluation of effects of N-CM and DFS-CM which are collected from normal (N) and deferoxamine (DFS) preconditioned umbilical cord-derived MSCs on rat diabetic nephropathy (DN) model.

Methods

After incubation of the MSCs in serum-free medium with/without 150 µM DFS for 48 h, the contents of N-CM and DFS-CM were analyzed by enzyme-linked immunosorbent assay. Diabetes (D) was induced by single dose of 55 mg/kg streptozotocin. Therapeutic effects of CMs were evaluated by biochemical, physical, histopathological and immunohistochemical analysis.

Results

The concentrations of vascular endothelial growth factor alpha, nerve growth factor and glial-derived neurotrophic factor in DFS-CM increased, while one of brain-derived neurotrophic factor decreased in comparison with N-CM. The creatinine clearance rate increased significantly in both treatment groups, while the improvement in albumin/creatinine ratio and renal mass index values were only significant for D + DFS-CM group. Light and electron microscopic deteriorations and loss of podocytes-specific nephrin and Wilms tumor-1 (WT-1) expressions were significantly restored in both treatment groups. Tubular beclin-1 expression was significantly increased for DN group, but it decreased in both treatment groups. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptotic cell death increased in the tubules of D group, while it was only significantly decreased for D + DFS-CM group.

Conclusions

DFS-CM can be more effective in the treatment of DN by reducing podocyte damage and tubular apoptotic cell death and regulating autophagic activity with its more concentrated secretome content than N-CM.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03121-6.

Direct Reprograming of Mouse Fibroblasts into Dermal Papilla Cells via Small Molecules

The reprogramming of somatic fibroblasts into alternative cell linages could provide a promising source of cells for regenerative medicine and cell therapy. However, the direct conversion of fibroblasts into other functional cell types is still challenging. In this study, we show that dermal-papilla-cell-like cells (DPC-LCs) can be generated by treating fibroblasts, including L929 mouse fibroblast cell lines and somatic mouse fibroblasts, with small molecules. Based on alkaline phosphatase activity and other molecular markers, different compounds or their combinations are needed for converting the two different fibroblasts into DPC-LCs. Notably, we found that TTNPB alone can efficiently convert primary adult mouse fibroblasts into DPC-LCs. DPC-LCs generated from mouse fibroblasts showed a stronger hair-inducing capacity. Transcriptome analysis reveals that expression of genes associated with a hair-inducing capacity are increased in DPC-LCs. This pharmacological approach to generating functional dermal papilla cells may have many important implications for hair follicle regeneration and hair loss therapy.

Therapeutic Effects and Repair Mechanism of HGF Gene-Transfected Mesenchymal Stem Cells on Injured Endometrium

There are many studies on the advantages of using mesenchymal stem cells (MSCs) that secrete various paracrine factors for repairing endometrial injury. However, the stability and effectiveness of MSCs require improvement to become a viable therapy. Hepatocyte growth factor (HGF), one of the cytokines secreted by MSCs, promotes vascular repair and mesenchymal to epithelial transformation (MET). Therefore, HGF likely promotes the repair process of the endometrium. We prepared MSCs transfected with the HGF gene to explore its repair effects and mechanism using a damaged endometrium mouse model. HGF gene-transfected MSCs were prepared by electroporation. The transfected MSCs retained their cellular characteristics and significantly increased the expression of HGF ( $P<0.01$ ). HGF gene-transfected MSCs helped damaged endometrium to recover its morphological characteristics, improved proliferation and decreased apoptosis of endometrial cells, increased the expression of endometrial vascular growth-related factors, and activated phosphorylated c-Met and AKT in the mouse endometrial damage model ( $P<0.05$ ). Compared with normal MSCs, HGF gene-transfected MSCs produced a more significant effect on damaged endometrial epithelium repair by activating the HGF/c-Met and downstream signaling pathways. Our results indicate that HGF gene-transfected MSCs provide an effective and promising tool for injured endometrium therapy.

Potential pre-activation strategies for improving therapeutic efficacy of mesenchymal stem cells: current status and future prospects

Mesenchymal stem cell (MSC)-based therapy has been considered as a promising approach targeting a variety of intractable diseases due to remarkable multiple effect of MSCs, such as multilineage differentiation, immunomodulatory property, and pro-regenerative capacity. However, poor engraftment, low survival rate of transplanted MSC, and impaired donor-MSC potency under host age/disease result in unsatisfactory therapeutic outcomes. Enhancement strategies, including genetic manipulation, pre-activation, and modification of culture method, have been investigated to generate highly functional MSC, and approaches for MSC pre-activation are highlighted. In this review, we summarized the current approaches of MSC pre-activation and further classified, analysed the scientific principles and main characteristics of these manipulations, and described the pros and cons of individual pre-activation strategies. We also discuss the specialized tactics to solve the challenges in this promising field so that it improves MSC therapeutic functions to serve patients better.

Enhancement strategies for mesenchymal stem cells and related therapies

Cell therapy, particularly mesenchymal stem/stromal (MSC) therapy, has been investigated for a wide variety of disease indications, particularly those with inflammatory pathologies. However, recently it has become evident that the MSC is far from a panacea. In this review we will look at current and future strategies that might overcome limitations in efficacy. Many of these take their inspiration from stem cell niche and the mechanism of MSC action in response to the injury microenvironment, or from previous gene therapy work which can now benefit from the added longevity and targeting ability of a live cell vector. We will also explore the nascent field of extracellular vesicle therapy and how we are already seeing enhancement protocols for this exciting new drug. These enhanced MSCs will lead the way in more difficult to treat diseases and restore potency where donors or manufacturing practicalities lead to diminished MSC effect.

All-Trans Retinoic Acid-Preconditioned Mesenchymal Stem Cells Improve Motor Function and Alleviate Tissue Damage After Spinal Cord Injury by Inhibition of HMGB1/NF-κB/NLRP3 Pathway Through Autophagy Activation

Spinal cord injury (SCI) is a significant public health issue that imposes numerous burdens on patients and society. Uncontrolled excessive inflammation in the second pathological phase of SCI can aggravate the injury. In this paper, we hypothesized that suppressing inflammatory pathways via autophagy could aid functional recovery, and prevent spinal cord tissue degeneration following SCI. To this end, we examined the effects of intrathecal injection of all-trans retinoic acid (ATRA)-preconditioned bone marrow mesenchymal stem cells (BM-MSCs) (ATRA-MSCs) on autophagy activity and the HMGB1/NF-κB/NLRP3 inflammatory pathway in an SCI rat model. This study demonstrated that SCI increased the expression of Beclin-1 (an autophagy-related gene) and NLRP3 inflammasome components such as NLRP3, ASC, Caspase-1, and pro-inflammatory cytokines IL-1β, IL-18, IL-6, and TNF-α. Additionally, following SCI, the protein levels of key autophagy factors (Beclin-1 and LC3-II) and HMGB1/NF-κB/NLRP3 pathway factors (HMGB1, p-NF-κB, NLRP3, IL-1β, and TNF-α) increased. Our findings indicated that ATRA-MSCs enhanced Beclin-1 and LC3-II levels, regulated the HMGB1/NF-κB/NLRP3 pathway, and inhibited pro-inflammatory cytokines. These factors improved hind limb motor activity and aided in the survival of neurons. Furthermore, ATRA-MSCs demonstrated greater beneficial effects than MSCs in treating spinal cord injury. Overall, ATRA-MSC treatment revealed beneficial effects on the damaged spinal cord by suppressing excessive inflammation and activating autophagy. Further research and investigation of the pathways involved in SCI and the use of amplified stem cells may be beneficial for future clinical use.

Impact of preconditioning stem cells with all-trans retinoic acid signaling pathway on cisplatin-induced nephrotoxicity by down-regulation of TGFβ1, IL-6, and caspase-3 and up-regulation of HIF1α and VEGF

The survival reduction after transplantation limited the clinical uses of stem cells so the current study explored preconditioning adipose-derived stem cells (ADMSCs) and all-trans retinoic acid (ATRA) effects on cisplatin that caused acute kidney injury (AKI). One hundred and fifty Sprague–Dawley male rats were distributed into five groups: control group; Cisplatin (CIS) group; CIS and ATRA group; CIS and ADMSC group, and CIS, ATRA, and ADMSCs group. Ten rats were euthanized after 3rd, 7th, and 11th days from CIS injection. Renal function, molecular studies, and histopathological analysis were studied. The preconditioning of ADMSCs with ATRA increased the viability of the cells which was reflected in the amelioration of kidney functions after CIS injection by the significant reduction of serum creatinine, microalbuminuria, as well as NO, and the significant rise of creatinine clearance, as well as SOD compared to the group of cisplatin. ATRA also supported ADMSCs by a significant down-regulation of caspase-3, il-6 and TGFβ1, and a significant up-regulation of HIF1, VEGF and CD31 compared to group of cisplatin which reversed the cisplatin effect. ATRA increased renoprotective properties of ADMSCs against cisplatin- induced AKI by reducing the apoptosis, inflammation, and stimulating angiogenesis.

Effects of dipotassium glycyrrhizinate on wound healing

PURPOSE

Dipotassium glycyrrhizinate (DPG) has anti-inflammatory properties, besides promoting the regeneration of skeletal muscle. However, it has not been reported on skin wound healing/regeneration. This research aimed to characterize the effects of DPG in the treatment of excisional wounds by second intention.

METHODS

Male adults (n=10) and elderly (n=10) Wistar rats were used. Two circular wounds were excised on the dorsal skin. The excised normal skins were considered adult (GAN) and elderly (GIN) naïve. For seven days, 2% DPG was applied on the proximal excision: treated adult (GADPG) and elderly (GIDPG), whereas distal excisions were untreated adult (GANT) and elderly (GINT). Wound healing areas were daily measured and removed for morphological analyses after the 14th and the 21st postoperative day. Slides were stained with hematoxylin-eosin, Masson's trichrome, and picrosirius red.

RESULTS

Histological analysis revealed intact (GAN/GIN) and regenerated(GANT/GINT/GADPG/GIDPG) skins. No differences of wounds' size were found among treated groups. Epidermis was thicker after 14 days and thinner after 21 days of DPG administration. Higher collagen I density was found in GIDPG (14th day) and GADPG (21st day).

CONCLUSIONS

DPG induced woundhealing/skin regeneration, with collagen I, being more effective in the first 14 days after injury.

Dual Action Gels Containing DsiRNA Loaded Gold Nanoparticles: Augmenting Diabetic Wound Healing by Promoting Angiogenesis and Inhibiting Infection

Hyperglycemia induces the prostaglandin transporter (PGT) gene overexpression, leading to poor vascularization and wound healing. Dicer substrate small interfering RNA (DsiRNA) and gold nanoparticles (AuNPs) co-loaded into PF127 gel was developed to overcome the disturbance and infections. The AuNPs were biosynthesized using cold and hot water extracts of Lignosus rhinocerotis (abbreviated CLRE and HLRE, respectively). The wound healing efficacy of a PF127 gel containing DsiRNA-AuNPs-CLRE and -HLRE (assigned as F2 and F3, respectively) was evaluated in a diabetes-induced Wistar rat model. The F2 (DC) and F3 (DH) treated groups revealed a faster wound closure (92.67 ± 3.4% and 85.1 ± 7.3%, respectively) than the positive control (commercial gel, DTI)(74.9 ± 13.3%). DH and DC groups presented an increased blood vessel density, along with decreased inflammatory cells. In comparison to positive control, higher prostaglandin E₂ (PGE₂) (495 ±79 and 50 ±121 pg/mL, for DC and DH group, respectively), vascular endothelial growth factor (VEGF) (49 ±15 and 38 ±3 pg/mL, for DC and DH group, respectively) and VEGF-A levels were detected in both groups (DC and DH), indicating the effectiveness of DsiRNA in enhancing PGE₂ production and vascularization. On evaluating microbiomes adhered to the wound areas, Gram-positive bacteria Staphylococcus and Corynebacterium, as well as Gram-negative Pseudomonas, Rodentibacter, and Acinetobacter, were found to be sensitive to the gel. Collectively, the gel was confirmed as a promising dressing for diabetic wound therapy, warranting further studies for clinical use.

Extracellular Vesicles from Adipose-Derived Stem Cells Promote Diabetic Wound Healing via the PI3K-AKT-mTOR-HIF-1α Signaling Pathway

BACKGROUND

Impaired potential of hypoxia-mediated angiogenesis lead poor healing of diabetic wounds. Previous studies have shown that extracellular vesicles from adipose derived stem cells (ADSC-EVs) accelerate wound healing with unelucidated mechanism. However, it is not yet clear about the underlying mechanism of ADSC-EVs in regulating the hypoxia-related PI3K/AKT/mTOR signaling pathway of vascular endothelial cells in diabetic wounds. Therefore, in this study, human derived ADSC-EVs (hADSC-EVs) isolated from adipose tissue were co-cultured with advanced glycosylation end product (AGE) treated human umbilical vein endothelial cells (HUVECs) in vitro and local injected into the wounds of diabetic rats.

METHODS

In vitro, the therapeutic potential of hADSC-EVs on AGE-treated HUVECs was evaluated by cell counting kit-8, scratching, and tube formation assay. Subsequently, the effects of hADSC-EVs on the PI3K/AKT/mTOR/HIF-1α signaling pathway were also assayed by qRT-PCR and western blot. In vivo, the effect of hADSC-EVs on diabetic wound healing in rats were also assayed by closure kinetics, Masson staining and HIF-1α-CD31 immunofluorescence.

RESULTS

hADSC-EVs were spherical in shape with an average particle size of 198.1 ± 91.5 nm, and were positive for CD63, CD9 and TSG101. hADSC-EVs promoted the expression of PI3K-AKT-mTOR-HIF-1α signaling pathway of AGEs treated HUVECs with improved the potential of proliferation, migration and tube formation, and improve the healing and angiogenesis of diabetic wound in rats. However, the effect of hADSC-EVs described above can be blocked by PI3K-AKT inhibitor both in vitro and vivo.

CONCLUSION

Our findings indicated that hADSC-EVs accolated the healing of diabetic wounds by promoting HIF-1α-mediated angiogenesis in the PI3K-AKT-mTOR depend manner.

Oct4-dependent FoxC1 activation improves the survival and neovascularization of mesenchymal stem cells under myocardial ischemia

Background

The administration of mesenchymal stem cells (MSCs) remains the most promising approach for cardiac repair after myocardial infarct (MI). However, their poor survival and potential in the ischemic environment limit their therapeutic efficacy for heart repair after MI. The purpose of this study was to investigate the influence of FoxC1-induced vascular niche on the activation of octamer-binding protein 4 (Oct4) and the fate of MSCs under hypoxic/ischemic conditions.

Methods

Vascular microenvironment/niche was induced by efficient delivery of FoxC1 transfection into hypoxic endothelial cells (ECs) or infarcted hearts. MSCs were cultured or injected into this niche by utilizing an in vitro coculture model and a rat MI model. Survival and neovascularization of MSCs regulated by Oct4 were explored using gene transfer and functional studies.

Results

Here, using gene expression heatmap, we demonstrated that cardiac ECs rapidly upregulated FoxC1 after acute ischemic cardiac injury, contributing to an intrinsic angiogenesis. In vitro, FoxC1 accelerated tube-like structure formation and increased survival of ECs, resulting in inducing a vascular microenvironment. Overexpression of FoxC1 in ECs promoted survival and neovascularization of MSCs under hypoxic coculture. Overexpression of Oct4, a FoxC1 target gene, in MSCs enhanced their mesenchymal-to-endothelial transition (MEndoT) while knockdown of Oct4 by siRNA altering vascularization. In a rat MI model, overexpression of FoxC1 in ischemic hearts increased post-infarct vascular density and improved cardiac function. The transplantation of adOct4-pretreated MSCs into these ischemic niches augments MEndoT, enhanced vascularity, and further improved cardiac function. Consistently, these cardioprotective effects of FoxC1 was abrogated when Oct4 was depleted in the MSCs and was mimicked by overexpression of Oct4.

Conclusions

Together, these studies demonstrate that the FoxC1/Oct4 axis is an essential aspect for survival and neovascularization of MSCs in the ischemic conditions and represents a potential therapeutic target for enhancing cardiac repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02553-w.

Serum-free medium and hypoxic preconditioning synergistically enhance the therapeutic effects of mesenchymal stem cells on experimental renal fibrosis

Background

Mesenchymal stem cells (MSCs) repair injured tissue in a paracrine manner. To enhance their therapeutic properties, preconditioning with various factors has been researched. We have previously showed that MSCs cultured in serum-free medium (SF-MSCs) promote their immunosuppressive ability, thereby enhancing their anti-fibrotic effect. Here, we examined whether serum-free medium and hypoxic preconditioning synergistically enhance the therapeutic effects of MSCs on renal fibrosis in rats with ischemia–reperfusion injury (IRI).

Methods

SF-MSCs were incubated under 1% O₂ conditions (hypo-SF-MSCs) or 21% O₂ conditions (normo-SF-MSCs) for 24 h before collection. After IRI procedure, hypo-SF-MSCs or normo-SF-MSCs were injected through the abdominal aorta. At 7 or 21 days post-injection, the rats were killed and their kidneys were collected to evaluate inflammation and fibrosis. In in vitro experiments, we investigated whether hypo-SF-MSCs enhanced secretion of anti-fibrotic humoral factors using transforming growth factor (TGF)-β1-stimulated HK-2 cells incubated with conditioned medium from hypo-SF-MSCs or normo-SF-MSCs.

Results

Normo-SF-MSCs showed attenuation of senescence, which increased their proliferative capacity. Although no significant difference in cellular senescence was found between normo-SF-MSCs and hypo-SF-MSCs, hypo-SF-MSCs further increased their proliferative capacity compared with normo-SF-MSCs. Additionally, administration of hypo-SF-MSCs more strongly ameliorated renal fibrosis than that of normo-SF-MSCs. Moreover, although hypo-SF-MSCs strongly attenuated infiltration of inflammatory cells compared with the control rats, which were treated with PBS, this attenuation was almost equal between normo-SF-MSCs and hypo-SF-MSCs. In vitro experiments revealed that hypo-SF-MSCs more significantly inhibited transforming growth factor (TGF)-β/Smad signaling compared with normo-SF-MSCs. Moreover, hypoxic preconditioning increased hepatocyte growth factor (HGF) secretion even under serum-free conditions, whereas knockdown of HGF in hypo-SF-MSCs attenuated inhibition of TGF-β/Smad signaling.

Conclusions

These results indicate that administration of ex vivo-expanded, hypoxia-preconditioned SF-MSCs may be a useful cell therapy to prevent renal fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02548-7.

Translational insights into stem cell preconditioning: From molecular mechanisms to preclinical applications

Cell-based therapy (CBT) is a revolutionary approach for curing a variety of degenerative diseases. Stem cell-based regenerative medicine is a novel strategy for treating tissue damages regarding stem cells unique properties such as differentiation potential, paracrine impacts, and self-renewal ability. However, the current cell-based treatments encounter considerable challenges to be translated into clinical practice, including low cell survival, migration, and differentiation rate of transplanted stem cells. The poor stem cell therapy outcomes mainly originate from the unfavorable condition of damaged tissues for transplanted stem cells. The promising method of preconditioning improves cell resistance against the host environment's stress by imposing certain conditions similar to the harsh microenvironment of the damaged tissues on the transplanted stem cells. Various pharmacological, biological, and physical inducers are able to establish preconditioning. In addition to their known pharmacological effects on tissues and cells, these preconditioning agents improve cell biological aspects such as cell survival, proliferation, differentiation, migration, immunomodulation, paracrine impacts, and angiogenesis. This review focuses on different protocols and inducers of preconditioning along with underlying molecular mechanisms of their effects on stem cell behavior. Moreover, preclinical applications of preconditioned stem cells in various damaged organs such as heart, lung, brain, bone, cartilage, liver, and kidney are discussed with prospects of their translation into the clinic.

Stem Cell-Derived Exosomes: a New Strategy of Neurodegenerative Disease Treatment

Short-term symptomatic treatment and dose-dependent side effects of pharmacological treatment for neurodegenerative diseases have forced the medical community to seek an effective treatment for this serious global health threat. Therapeutic potential of stem cell for treatment of neurodegenerative disorders was identified in 1980 when fetal nerve tissue was used to treat Parkinson's disease (PD). Then, extensive studies have been conducted to develop this treatment strategy for neurological disease therapy. Today, stem cells and their secretion are well-known as a therapeutic environment for the treatment of neurodegenerative diseases. This new paradigm has demonstrated special characteristics related to this treatment, including neuroprotective and neurodegeneration, remyelination, reduction of neural inflammation, and recovery of function after induced injury. However, the exact mechanism of stem cells in repairing nerve damage is not yet clear; exosomes derived from them, an important part of their secretion, are introduced as responsible for an important part of such effects. Numerous studies over the past few decades have evaluated the therapeutic potential of exosomes in the treatment of various neurological diseases. In this review, after recalling the features and therapeutic history, we will discuss the latest stem cell-derived exosome-based therapies for these diseases.

The Effect of Inflammatory Priming on the Therapeutic Potential of Mesenchymal Stromal Cells for Spinal Cord Repair

Mesenchymal stromal cells (MSC) are used for cell therapy for spinal cord injury (SCI) because of their ability to support tissue repair by paracrine signaling. Preclinical and clinical research testing MSC transplants for SCI have revealed limited success, which warrants the exploration of strategies to improve their therapeutic efficacy. MSC are sensitive to the microenvironment and their secretome can be altered in vitro by exposure to different culture media. Priming MSC with inflammatory stimuli increases the expression and secretion of reparative molecules. We studied the effect of macrophage-derived inflammation priming on MSC transplants and of primed MSC (pMSC) acute transplants (3 days) on spinal cord repair using an adult rat model of moderate-severe contusive SCI. We found a decrease in long-term survival of pMSC transplants compared with unprimed MSC transplants. With a pMSC transplant, we found significantly more anti-inflammatory macrophages in the contusion at 4 weeks post transplantation (wpt). Blood vessel presence and maturation in the contusion at 1 wpt was similar in rats that received pMSC or untreated MSC. Nervous tissue sparing and functional recovery were similar across groups. Our results indicate that macrophage-derived inflammation priming does not increase the overall therapeutic potential of an MSC transplant in the adult rat contused spinal cord.

Inhibiting PHD2 in human periodontal ligament cells via lentiviral vector-mediated RNA interference facilitates cell osteogenic differentiation and periodontal repair

Periodontal defect regeneration in severe periodontitis remains a challenging task in clinic owing to poor survival of seed cells caused by the remaining oxidative stress microenvironment. Recently, the reduction of prolyl hydroxylase domain-containing protein 2 (PHD2), a primary cellular oxygen sensor, has shown an incredible extensive effect on skeletal muscle tissue regeneration by improving cell resistance to reactive oxygen species, whereas its role in periodontal defect repair is unclear. Here, through lentivirus vector-mediated RNA interference, the PHD2 gene in human periodontal ligament cells (hPDLCs) is silenced, leading to hypoxia-inducible factor-1α stabilization in normoxia. In vitro, PHD2 silencing not only exhibited a satisfactory effect on cell proliferation, but also induced distinguished osteogenic differentiation of hPDLCs. Real-time polymerase chain reaction and Western blotting revealed significant up-regulation of osteocalcin, alkaline phosphatase (ALP), runt-related transcription factor 2, and collagen type I (COL I). Under oxidative stress conditions, COL I and ALP expression levels, suppressed by 100 μM H₂ O₂ , were elevated by PHD2-gene-silencing in hPDLCs. In vivo, periodontal fenestration defects were established in 18 female Sprague-Dawley rats aged 6 wk old, followed by implantation of PHD2 silencing hPDLCs in situ for 21 d. Persistent and stable silencing of PHD2 in hPDLCs promoted better new bone formation according to microcomputed tomography 3D reconstruction and related bone parameter analysis. This work demonstrates the therapeutic efficiency of PHD2 gene interference in osteogenic differentiation and periodontal defect repair for highly efficient periodontal regeneration.

Mesenchymal stem/stromal cells as a valuable source for the treatment of immune-mediated disorders

Over recent years, mesenchymal stem/stromal cells (MSCs) and their potential biomedical applications have received much attention from the global scientific community in an increasing manner. Firstly, MSCs were successfully isolated from human bone marrow (BM), but in the next steps, they were also extracted from other sources, mostly from the umbilical cord (UC) and adipose tissue (AT). The International Society for Cellular Therapy (ISCT) has suggested minimum criteria to identify and characterize MSCs as follows: plastic adherence, surface expression of CD73, D90, CD105 in the lack of expression of CD14, CD34, CD45, and human leucocyte antigen-DR (HLA-DR), and also the capability to differentiate to multiple cell types including adipocyte, chondrocyte, or osteoblast in vitro depends on culture conditions. However, these distinct properties, including self-renewability, multipotency, and easy accessibility are just one side of the coin; another side is their huge secretome which is comprised of hundreds of mediators, cytokines, and signaling molecules and can effectively modulate the inflammatory responses and control the infiltration process that finally leads to a regulated tissue repair/healing or regeneration process. MSC-mediated immunomodulation is a direct result of a harmonic synergy of MSC-released signaling molecules (i.e., mediators, cytokines, and chemokines), the reaction of immune cells and other target cells to those molecules, and also feedback in the MSC-molecule-target cell axis. These features make MSCs a respectable and eligible therapeutic candidate to be evaluated in immune-mediated disorders, such as graft versus host diseases (GVHD), multiple sclerosis (MS), Crohn's disease (CD), and osteoarthritis (OA), and even in immune-dysregulating infectious diseases such as the novel coronavirus disease 2019 (COVID-19). This paper discussed the therapeutic applications of MSC secretome and its biomedical aspects related to immune-mediated conditions. Sources for MSC extraction, their migration and homing properties, therapeutic molecules released by MSCs, and the pathways and molecular mechanisms possibly involved in the exceptional immunoregulatory competence of MSCs were discussed. Besides, the novel discoveries and recent findings on immunomodulatory plasticity of MSCs, clinical applications, and the methods required for their use as an effective therapeutic option in patients with immune-mediated/immune-dysregulating diseases were highlighted.

Small Molecule Treatments Improve Differentiation Potential of Human Amniotic Fluid Stem Cells

Human amniotic fluid stem cells (AFSC) are an exciting and very promising source of stem cells for therapeutic applications. In this study we investigated the effects of short-term treatments of small molecules to improve stem cell properties and differentiation capability. For this purpose, we used epigenetically active compounds, such as histone deacetylase inhibitors Trichostatin A (TSA) and sodium butyrate (NaBut), as well as multifunctional molecules of natural origin, such as retinoic acid (RA) and vitamin C (vitC). We observed that combinations of these compounds triggered upregulation of genes involved in pluripotency (KLF4, OCT4, NOTCH1, SOX2, NANOG, LIN28a, CMYC), but expression changes of these proteins were mild with only significant downregulation of Notch1. Also, some alterations in cell surface marker expression was established by flow cytometry with the most explicit changes in the expression of CD105 and CD117. Analysis of cellular energetics performed using Seahorse analyzer and assessment of gene expression related to cell metabolism and respiration (NRF1, HIF1α, PPARGC1A, ERRα, PKM, PDK1, LDHA, NFKB1, NFKB2, RELA, RELB, REL) revealed that small molecule treatments stimulate AFSCs toward a more energetically active phenotype. To induce cells to differentiate toward neurogenic lineage several different protocols including commercial supplements N2 and B27 together with RA were used and compared to the same differentiation protocols with the addition of a pre-induction step consisting of a combination of small molecules (vitC, TSA and RA). During differentiation the expression of several neural marker genes was analyzed (Nestin, MAP2, TUBB3, ALDH1L1, GFAP, CACNA1D, KCNJ12, KCNJ2, KCNH2) and the beneficial effect of small molecule treatment on differentiation potential was observed with upregulated gene expression. Differentiation was also confirmed by staining TUBB3, NCAM1, and Vimentin and assessed by secretion of BDNF. The results of this study provide valuable insights for the potential use of short-term small molecule treatments to improve stem cell characteristics and boost differentiation potential of AFSCs.

Apoptotic bodies derived from mesenchymal stem cells promote cutaneous wound healing via regulating the functions of macrophages

BACKGROUND

As the major interface between the body and the external environment, the skin is liable to various injuries. Skin injuries often lead to severe disability, and the exploration of promising therapeutic strategies is of great importance. Exogenous mesenchymal stem cell (MSC)-based therapy is a potential strategy due to the apparent therapeutic effects, while the underlying mechanism is still elusive. Interestingly, we observed the extensive apoptosis of exogenous bone marrow mesenchymal stem cells (BMMSCs) in a short time after transplantation in mouse skin wound healing models. Considering the roles of extracellular vesicles (EVs) in intercellular communication, we hypothesized that the numerous apoptotic bodies (ABs) released during apoptosis may partially contribute to the therapeutic effects.

METHODS

ABs derived from MSCs were extracted, characterized, and applied in mouse skin wound healing models, and the therapeutic effects were evaluated. Then, the target cells of ABs were explored, and the effects of ABs on macrophages were investigated in vitro.

RESULTS

We found ABs derived from MSCs promoted cutaneous wound healing via triggering the polarization of macrophages towards M2 phenotype. In addition, the functional converted macrophages further enhanced the migration and proliferation abilities of fibroblasts, which together facilitated the wound healing process.

CONCLUSIONS

Collectively, our study demonstrated that transplanted MSCs promoted cutaneous wound healing partially through releasing apoptotic bodies which could convert the macrophages towards an anti-inflammatory phenotype that plays a crucial role in the tissue repair process.

Fusion peptide engineered "statically-versatile" titanium implant simultaneously enhancing anti-infection, vascularization and osseointegration

Although antimicrobial titanium implants can prevent biomaterial-associated infection (BAI) in orthopedics, they display cytotoxicity and delayed osseointegration. Therefore, versatile implants are desirable for simultaneously inhibiting BAI and promoting osseointegration, especially "statically-versatile" ones with nonessential external stimulations for facilitating applications. Herein, we develop a "statically-versatile" titanium implant by immobilizing an innovative fusion peptide (FP) containing HHC36 antimicrobial sequence and QK angiogenic sequence via sodium borohydride reduction promoted Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC-SB), which shows higher immobilization efficiency than traditional CuAAC with sodium ascorbate reduction (CuAAC-SA). The FP-engineered implant exhibits over 96.8% antimicrobial activity against four types of clinical bacteria (S. aureus, E. coli, P. aeruginosa and methicillin-resistant S. aureus), being stronger than that modified with mixed peptides. This can be mechanistically attributed to the larger bacterial accessible surface area of HHC36 sequence. Notably, the implant can simultaneously enhance cellular proliferation, up-regulate expressions of angiogenesis-related genes/proteins (VEGF and VEGFR-2) of HUVECs and osteogenesis-related genes/proteins (ALP, COL-1, RUNX-2, OPN and OCN) of hBMSCs. In vivo assay with infection and non-infection bone-defect model reveals that the FP-engineered implant can kill 99.63% of S. aureus, and simultaneously promote vascularization and osseointegration. It is believed that this study presents an excellent strategy for developing "statically-versatile" orthopedic implants.

All-trans-retinoic acid inhibits mink hair follicle growth via inhibiting proliferation and inducing apoptosis of dermal papilla cells through TGF-β2/Smad2/3 pathway

Dermal papilla cells (DPCs), an important component of hair follicles, its proliferation and apoptosis directly regulate and maintain the growth of hair follicles. All-trans-retinoic acid (ATRA) plays a critical role in hair growth. In this study, the effects of ATRA on cultured mink hair follicle growth were studied by administration of different concentrations of ATRA for 12 days in vitro. In addition, the proliferation and apoptosis of DPCs were measured after treating with ATRA. The mRNA and protein levels of hair follicle growth associated factor transforming growth factor-β2 (TGF-β2) and the phosphorylation levels of Smad2/3 were determined. Moreover, TGF-β type I and type II receptor inhibitor LY2109761 and specific inhibitor of Smad3 (SIS3) were administered to investigate the underlying molecular mechanism. The results showed that ATRA inhibited hair follicle growth, promoted TGF-β2 expression and activated phosphorylation of Smad2/3. In addition, ATRA inhibited cell proliferation by arresting the cell cycle at G1 phase and induced apoptosis of DPCs by enhancing the ratio of Bax/Bcl-2 and promoted the cleavage of caspase-3. Furthermore, LY2109761 or SIS3 partially reversed the decreased cell viability, increased apoptosis that were induced by ATRA. In conclusion, ATRA could inhibit hair follicle growth via inhibiting proliferation and inducing apoptosis of DPCs partially through the TGF-β2/Smad2/3 pathway.

Phorbol ester activates human mesenchymal stem cells to inhibit B cells and ameliorate lupus symptoms in MRL.Fas lpr mice

Rationale: Systemic lupus erythematosus (SLE) is a multi-organ autoimmune disease characterized by autoantibody production by hyper-activated B cells. Although mesenchymal stem cells (MSCs) ameliorate lupus symptoms by inhibiting T cells, whether they inhibit B cells has been controversial. Here we address this issue and reveal how to prime MSCs to inhibit B cells and improve the efficacy of MSCs in SLE.

Methods: We examined the effect of MSCs on purified B cells in vitro and the therapeutic efficacy of MSCs in lupus-prone MRL.Fas^lpr mice. We screened chemicals for their ability to activate MSCs to inhibit B cells.

Results: Mouse bone marrow-derived MSCs inhibited mouse B cells in a CXCL12-dependent manner, whereas human bone marrow-derived MSCs (hMSCs) did not inhibit human B (hB) cells. We used a chemical approach to overcome this hurdle and found that phorbol myristate acetate (PMA), phorbol 12,13-dibutyrate, and ingenol-3-angelate rendered hMSCs capable of inhibiting IgM production by hB cells. As to the mechanism, PMA-primed hMSCs attracted hB cells in a CXCL10-dependent manner and induced hB cell apoptosis in a PD-L1-dependent manner. Finally, we showed that PMA-primed hMSCs were better than naïve hMSCs at ameliorating SLE progression in MRL.Fas^lpr mice.

Conclusion: Taken together, our data demonstrate that phorbol esters might be good tool compounds to activate MSCs to inhibit B cells and suggest that our chemical approach might allow for improvements in the therapeutic efficacy of hMSCs in SLE.

Exosomes released from educated mesenchymal stem cells accelerate cutaneous wound healing via promoting angiogenesis

Objectives

Skin serves as the major interface between the external environment and body which is liable to many kinds of injuries. Mesenchymal stem cell (MSC) therapy has been widely used and became a promising strategy. Pre‐treatment with chemical agents, hypoxia or gene modifications can partially protect MSCs against injury, and the pre‐treated MSCs show the improved differentiation, homing capacity, survival and paracrine effects regard to attenuating injury. The aim of this study was to investigate whether the exosomes from the educated MSCs contribute to accelerate wound healing process.

Materials and methods

We extracted the exosomes from the two educated MSCs and utilized them in the cutaneous wound healing model. The pro‐angiogenetic effect of exosomes on endothelial cells was also investigated.

Results

We firstly found that MSCs pre‐treated by exosomes from neonatal serum significantly improved their biological functions and the effect of therapy. Moreover, we extracted the exosomes from the educated MSCs and utilized them to treat the cutaneous wound model directly. We found that the released exosomes from MSCs which educated by neonatal serum before had the more outstanding performance in therapeutic effect. Mechanistically, we revealed that the recipient endothelial cells (ECs) were targeted and the exosomes promoted their functions to enhance angiogenesis via regulating AKT/eNOS pathway.

Conclusions

Our findings unravelled the positive effect of the upgraded exosomes from the educated MSCs as a promising cell‐free therapeutic strategy for cutaneous wound healing.

All-Trans Retinoic Acid Grafted Poly Beta-Amino Ester Nanoparticles: A Novel Anti-angiogenic Drug Delivery System

Purpose: Developing chemotherapy with nanoplatforms offers a promising strategy for effective cancer treatment. In the present study, we propose a novel all-trans retinoic acid (ATRA) grafted poly beta-amino ester (PBAE) copolymer for preparing nanoparticles (NPs). Methods: ATRA grafted PBAE (ATRA-g-PBAE) copolymer was synthesized by grafting ATRA to PBAE; it was characterized by proton nuclear magnetic resonance, Fourier transform infrared, and thermogravimetric analysis. ATRA-g-PBAE NPs were prepared by the solvent displacement method. Design-Expert software was employed to optimize size of NPs. The morphology was evaluated by transmission electron microscope, and ultraviolet-visible spectroscopy was applied for drug release. Cytotoxicity was evaluated toward HUVEC cell line, and the 3D collagencytodex model was used to evaluate anti-angiogenic property of PBAE, ATRA, and NPs. Results: The optimum size of the NPs was 139.4 ± 1.41 nm. After 21 days, 66.09% ± 1.39 and 42.14% ± 1.07 of ATRA were released from NPs at pH 5.8 and 7.4, respectively. Cell culture studies demonstrated antiangiogenic effects of ATRA-g-PBAE NPs. Anti-angiogenesis IC50 was 0.007 mg/mL for NPs (equal to 0.002 mg/mL of ATRA) and 0.005 mg/mL for free ATRA. Conclusion: This study proposes the ATRA-g-PBAE NPs with inherent anti-angiogenic effects as promising carrier for anticancer drugs with purpose of dual drug delivery.

Resveratrol Preincubation Enhances the Therapeutic Efficacy of hUC-MSCs by Improving Cell Migration and Modulating Neuroinflammation Mediated by MAPK Signaling in a Mouse Model of Alzheimer's Disease

Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) are promising for the treatment of Alzheimer's disease (AD). However, their low rate of migration and survival in the brain limit their clinical applicability. This study is designed to improve the therapeutic potential of hUC-MSCs by preincubating them with resveratrol, a natural polyphenol capable of regulating cell destiny. Herein, we demonstrate that resveratrol preincubation enhances the migration of hUC-MSCs in vitro, as well as their survival and homing into the hippocampus of AD mice in vivo. Moreover, resveratrol-primed MSCs were better able to inhibit amyloid-β peptide (Aβ) deposition, Tau hyperphosphorylation, and oxidative stress, all while improving learning and memory. Notably, we found that hUC-MSCs inhibited neuroinflammation by reacting with astrocytes and microglial cells and suppressing mitogen-activated protein kinases (MAPKs), extracellular signal kinases (ERK), p38 kinases (p38), and c-Jun N-terminal kinases (JNK) signaling pathways in the hippocampus of AD mice. Furthermore, resveratrol pretreatment enhanced these effects. Conclusively, the current study revealed that resveratrol preconditioning protected hUC-MSCs against the hostile microenvironment characteristic of AD and enhanced their viability and homing into the brain of AD mice. The use of resveratrol-pretreated hUC-MSCs is thereby proposed to be a promising therapy for AD.

Meloxicam, a Selective COX-2 Inhibitor, Mediates Hypoxia-Inducible Factor- (HIF-) 1α Signaling in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is regarded as a leading cause of cancer-related deaths, and its progression is associated with hypoxia and the induction of hypoxia-inducible factor (HIF). Meloxicam, a selective cyclooxygenase-2 (COX-2) inhibitor, induces cell death in various malignancies. However, the underlying mechanism remains to be elucidated in HCC, especially under hypoxic conditions. The alteration of COX-2 and HIF-1α oncogenicity was evaluated in HCC specimens by tissue microarray. Cell viability, angiogenesis assays, and xenografted nude mice were used to evaluate the effects of meloxicam, along with flow cytometry to detect the cell cycle, apoptosis, and mitochondrial membrane potential (ΔΨm) of HCC. qRT-PCR, Western blotting, immunofluorescence, immunohistochemistry, luciferase assay, and RNAi were carried out to determine the HIF-1α signaling affected by meloxicam. In this study, we showed that meloxicam exerts antiproliferative and antiangiogenesis efficacy in vitro and in vivo and causes disruption of mitochondrial membrane potential (ΔΨm), thus leading to caspase-dependent apoptosis under hypoxic environments. Exposure to meloxicam significantly reduced HIF-1α transcriptional activation and expression through sequestering it in the cytoplasm and accelerating degradation via increasing the von Hippel-Lindau tumor suppressor protein (pVHL) in HCC. These data demonstrated that inhibition of HIF-1α by meloxicam could suppress angiogenesis and enhance apoptosis of HCC cells. This discovery highlights that COX-2 specific inhibitors may be a promising therapy in the treatment of HCC.

Insight into adipokines to optimize therapeutic effects of stem cell for tissue regeneration

Stem cell therapy is considered as a promising regenerative medicine for repairing and treating damaged tissues and/or preventing various diseases. But there are still some obstacles such as low cell migration, poor stem cell engraftment and decreased cell survival that need to be overcome before transplantation. Therefore, a large body of studies has focused on improving the efficiency of stem cell therapy. For instance, preconditioning of stem cells has emerged as an effective strategy to reinforce therapeutic efficacy. Adipokines are signaling molecules, secreted by adipose tissue, which regulate a variety of biological processes in adipose tissue and other organs including the brain, liver, and muscle. In this review article, we shed light on the biological effects of some adipokines including apelin, oncostatin M, omentin-1 and vaspin on stem cell therapy and the most recent preclinical advances in our understanding of how these functions ameliorate stem cell therapy outcome.

Understanding and leveraging cell metabolism to enhance mesenchymal stem cell transplantation survival in tissue engineering and regenerative medicine applications

In tissue engineering and regenerative medicine, stem cell-specifically, mesenchymal stromal/stem cells (MSCs)-therapies have fallen short of their initial promise and hype. The observed marginal, to no benefit, success in several applications has been attributed primarily to poor cell survival and engraftment at transplantation sites. MSCs have a metabolism that is flexible enough to enable them to fulfill their various cellular functions and remarkably sensitive to different cellular and environmental cues. At the transplantation sites, MSCs experience hostile environments devoid or, at the very least, severely depleted of oxygen and nutrients. The impact of this particular setting on MSC metabolism ultimately affects their survival and function. In order to develop the next generation of cell-delivery materials and methods, scientists must have a better understanding of the metabolic switches MSCs experience upon transplantation. By designing treatment strategies with cell metabolism in mind, scientists may improve survival and the overall therapeutic potential of MSCs. Here, we provide a comprehensive review of plausible metabolic switches in response to implantation and of the various strategies currently used to leverage MSC metabolism to improve stem cell-based therapeutics.

Retinoic acid receptor α as a novel contributor to adrenal cortex structure and function through interactions with Wnt and Vegfa signalling

Primary aldosteronism (PA) is the most frequent form of secondary arterial hypertension. Mutations in different genes increase aldosterone production in PA, but additional mechanisms may contribute to increased cell proliferation and aldosterone producing adenoma (APA) development. We performed transcriptome analysis in APA and identified retinoic acid receptor alpha (RARα) signaling as a central molecular network involved in nodule formation. To understand how RARα modulates adrenal structure and function, we explored the adrenal phenotype of male and female Rarα knockout mice. Inactivation of Rarα in mice led to significant structural disorganization of the adrenal cortex in both sexes, with increased adrenal cortex size in female mice and increased cell proliferation in males. Abnormalities of vessel architecture and extracellular matrix were due to decreased Vegfa expression and modifications in extracellular matrix components. On the molecular level, Rarα inactivation leads to inhibition of non-canonical Wnt signaling, without affecting the canonical Wnt pathway nor PKA signaling. Our study suggests that Rarα contributes to the maintenance of normal adrenal cortex structure and cell proliferation, by modulating Wnt signaling. Dysregulation of this interaction may contribute to abnormal cell proliferation, creating a propitious environment for the emergence of specific driver mutations in PA.

Multi-drug hybrid delivery systems with distinct release profiles based on gelatin/collagen containing vesicles derived from block copolymers

Hybrid delivery systems can release multiple drugs with different profiles and have several applications, including skin dressing. In this work, the co-solvent technique was used for the preparation of nanometric vesicles based on poly(styrene-b-ethylene oxide) block copolymer (BCPVs) containing adapalene (AD). The BCPVs were incorporated into collagen and gelatin matrices together with free AD and silver sulfadiazine (SSD). The AD content of BCPVs and their release capacity were analyzed by using ultraviolet-visible spectroscopy (UV-Vis). The gelatin and collagen matrices were evaluated for their ability to release AD and SSD through an in vitro release study. The obtained results confirmed that the production of empty and AD-loaded BCPVs was viable. The degree of AD encapsulation in BCPVs was 9.0% and the in vitro test revealed a constant, slow, and prolonged release of AD content from AD-loaded BCPVs. The combination of free and encapsulated multiple drugs in hybrid delivery systems based on gelatin and collagen matrices was shown to act as a skin dressing that combined the progressive release of large amounts of drugs within the first hours of use (to restrict infection) with a more prolonged and slow release of AD to enhance skin healing.