Osteopontin activates mesenchymal stem cells to repair skin wound

The critical role of osteopontin (OPN) in fibrotic diseases

Fibrosis is a pathological condition characterized by the excessive deposition of extracellular matrix components in tissues and organs, leading to progressive architectural remodelling and contributing to the development of various diseases. Osteopontin (OPN), a highly phosphorylated glycoprotein, has been increasingly recognized for its involvement in the progression of tissue fibrosis. This review provides a comprehensive overview of the genetic and protein structure of OPN and focuses on our current understanding of the role of OPN in the development of fibrosis in the lungs and other tissues. Additionally, special attention is given to the potential of OPN as a biomarker and a novel therapeutic target in the treatment of fibrosis.

Downregulation of RUNX1-Activated Osteopontin Facilitates Burn Wound Healing by Activating the MAPK Pathways

Burn wounds require intervention to ensure timely progression to reduce morbidity and mortality. The migrative and proliferative capabilities of keratinocytes are impaired in wounds. Matrix metalloproteinases (MMPs) can degrade the extracellular matrix (ECM), allowing epithelial cells to migrate. As reported, osteopontin can regulate cell migration, cell adhesion, and ECM invasion in endothelial and epithelial cells, and its expression is significantly increased in chronic wounds. Therefore, this study investigates the biological functions of osteopontin and its related mechanisms involved in burn wounds. We established cellular and animal models of burn injury. Levels of osteopontin, RUNX1, MMPs, collagen I, CK19, PCNA, and pathway-associated proteins were measured by RT-qPCR, western blotting, and immunofluorescence staining. Cell viability and migration were examined by CCK-8 and wound scratch assays. Histological changes were analyzed by hematoxylin and eosin staining and Masson's trichrome staining. For in vitro analysis, osteopontin silencing facilitated the growth and migration of HaCaT cells and promoted ECM degradation in HaCaT cells. Mechanistically, RUNX1 bound to osteopontin promoter, and RUNX1 upregulation attenuated the promoting efficacy of osteopontin silencing on cell growth and migration and ECM degradation. Additionally, RUNX1-activated osteopontin inactivated the MAPK signaling pathway. For in vivo analysis, osteopontin depletion facilitated burn wound healing by promoting reepithelialization and ECM degradation. In conclusion, RUNX1 activates the osteopontin expression at the transcriptional level and osteopontin depletion facilitates the recovery of burn wounds by promoting the migration of keratinocytes and reepithelization and ECM degradation by activating the MAPK pathway.

Reduced Bone Regeneration in Rats With Type 2 Diabetes Mellitus as a Result of Impaired Stromal Cell and Osteoblast Function-A Computer Modeling Study

Bone has the fascinating ability to self-regenerate. However, under certain conditions, such as type 2 diabetes mellitus (T2DM), this ability is impaired. T2DM is a chronic metabolic disease known by the presence of elevated blood glucose levels that is associated with reduced bone regeneration capability, high fracture risk, and eventual non-union risk after a fracture. Several mechanical and biological factors relevant to bone regeneration have been shown to be affected in a diabetic environment. However, whether impaired bone regeneration in T2DM can be explained due to mechanical or biological alterations remains unknown. To elucidate the relevance of either one, the aim of this study was to investigate the relative contribution of T2DM-related alterations on either cellular activity or mechanical stimuli driving bone regeneration. A previously validated in silico computer modeling approach that was capable of explaining bone regeneration in uneventful conditions of healing was further developed to investigate bone regeneration in T2DM. Aspects analyzed included the presence of mesenchymal stromal cells (MSCs), cellular migration, proliferation, differentiation, apoptosis, and cellular mechanosensitivity. To further verify the computer model findings against in vivo data, an experimental setup was replicated, in which regeneration was compared in healthy and diabetic after a rat femur bone osteotomy stabilized with plate fixation. We found that mechanical alterations had little effect on the reduced bone regeneration in T2DM and that alterations in MSC proliferation, MSC migration, and osteoblast differentiation had the highest effect. In silico predictions of regenerated bone in T2DM matched qualitatively and quantitatively those from ex vivo μCT at 12 weeks post-surgery when reduced cellular activities reported in previous in vitro and in vivo studies were included in the model. The presented findings here could have clinical implications in the treatment of bone fractures in patients with T2DM. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Allele-specific expression reveals genetic drivers of tissue regeneration in mice

In adult mammals, skin wounds typically heal by scarring rather than through regeneration. In contrast, "super-healer" Murphy Roths Large (MRL) mice have the unusual ability to regenerate ear punch wounds; however, the molecular basis for this regeneration remains elusive. Here, in hybrid crosses between MRL and non-regenerating mice, we used allele-specific gene expression to identify cis-regulatory variation associated with ear regeneration. Analyzing three major cell populations (immune, fibroblast, and endothelial), we found that genes with cis-regulatory differences specifically in fibroblasts were associated with wound-healing pathways and also co-localized with quantitative trait loci for ear wound-healing. Ectopic treatment with one of these proteins, complement factor H (CFH), accelerated wound repair and induced regeneration in typically fibrotic wounds. Through single-cell RNA sequencing (RNA-seq), we observed that CFH treatment dramatically reduced immune cell recruitment to wounds, suggesting a potential mechanism for CFH's effect. Overall, our results provide insights into the molecular drivers of regeneration with potential clinical implications.

Cas9-mediated knockout of Ndrg2 enhances the regenerative potential of dendritic cells for wound healing

Chronic wounds impose a significant healthcare burden to a broad patient population. Cell-based therapies, while having shown benefits for the treatment of chronic wounds, have not yet achieved widespread adoption into clinical practice. We developed a CRISPR/Cas9 approach to precisely edit murine dendritic cells to enhance their therapeutic potential for healing chronic wounds. Using single-cell RNA sequencing of tolerogenic dendritic cells, we identified N-myc downregulated gene 2 (Ndrg2), which marks a specific population of dendritic cell progenitors, as a promising target for CRISPR knockout. Ndrg2-knockout alters the transcriptomic profile of dendritic cells and preserves an immature cell state with a strong pro-angiogenic and regenerative capacity. We then incorporated our CRISPR-based cell engineering within a therapeutic hydrogel for in vivo cell delivery and developed an effective translational approach for dendritic cell-based immunotherapy that accelerated healing of full-thickness wounds in both non-diabetic and diabetic mouse models. These findings could open the door to future clinical trials using safe gene editing in dendritic cells for treating various types of chronic wounds.

Effects of Progestin on Modulation of the Expression of Biomarkers in Endometriosis

BACKGROUND

Our study aimed to examine the osteopontin (OPN) serum levels and tissue expression of CD44 and OPN in endometriosis-affected women both undergoing and not undergoing progestin treatment, and also to determine their involvement in the pathogenesis of endometriosis.

METHODS

Using an ELISA kit, we evaluated the OPN serum levels of healthy and endometriosis-affected women both undergoing and not undergoing progestin treatment. Immunohistochemical (IHC) analyses were used to assess the endometriotic tissue expressions of CD44 and OPN.

RESULTS

There were statistically significant higher OPN serum levels in the healthy control group compared to the women with endometriosis. Furthermore, there were higher OPN serum levels in the endometriosis-affected women undergoing the progestin treatment, but the difference did not reach statistical significance. In comparison to OPN, CD44 expression was significantly higher in all the endometriotic tissue glands and stroma, regardless of the patient's treatment status. Compared to the group receiving therapy, the OPN levels were higher in the endometriosis group not receiving therapy. OPN's robust cytoplasmic expression seemed to be associated with the non-treatment group.

CONCLUSION

Endometriosis, CD44, and OPN appear to be closely related. This study suggests that endometriosis that has not been treated has an immunological profile distinct to endometriosis that has received treatment.

Human Amniotic Membrane Promotes Angiogenesis in an Oxidative Stress Chronic Diabetic Murine Wound Model

Objective: The development of animal models, which adequately replicate the pathophysiology of chronic wounds, has been challenging. In this study, we utilized an oxidative stress (OS) murine model, which was previously developed by our group, to study the effect of a human amniotic membrane (AM) on chronic wound healing. Approach: Forty-five diabetic (genetically obese leptin receptor-deficient mice [db/db]) mice were separated into three groups. Thirty mice received an OS regimen and a 1 - × 1 cm² full-thickness excisional dorsal wound. The wounds were either covered with AM and occlusive dressing (db/db^OS-AM) or occlusive dressing only (db/db^OS). Fifteen mice did not receive the OS regimen, and were covered with AM and occlusive dressing (db/db-AM). The wounds were photographed, and tissue was harvested at various time points. Results: Vascular density was higher in the AM-treated groups (db/db^OS-AM: 34 ± 12; db/db-AM: 37 ± 14; vs. db/db^OS: 19 ± 9 cluster of differentiation 31 [CD31⁺]/high power field [HPF] photograph; p = 0.04 and p = 0.003). Vessel maturity was lowest in the db/db^OS group (21% ± 4%; vs. db/db^OS-AM: 38% ± 10%, p = 0.004; db/db-AM: 40% ± 11%, p = 0.0005). Leukocyte infiltration was higher in the AM groups (db/db^OS-AM: 15 ± 4; db/db-AM: 16 ± 4 vs. db/db^OS: 8 ± 3 lymphocyte common antigen [CD45⁺]/HPF; p = 0.005 and p = 0.06). AM upregulated various proangiogenic factors, including vascular endothelial growth factor (VEGF), and downregulated genes involved in chronicity, such as osteopontin, as visualized through proteome analysis and western blotting. Cell death was lower in the AM groups (db/db^OS-AM: 28 ± 10, db/db-AM: 7 ± 5 vs. db/db^OS: 17% ± 9% Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling [TUNEL⁺]; p = 0.03 and p < 0.0001). Innovation: This study offers new insight on the mechanisms of action of human AM in chronic wound healing. Conclusion: AM treatment promoted healing in mice with complex chronic wounds. The AM stimulated angiogenesis through upregulation of proangiogenic factors, improving the wound milieu by increasing leukocyte and growth factor delivery and decreasing cell death.

Periosteal skeletal stem cells can migrate into the bone marrow and support hematopoiesis after injury

Functional stromal cells are known to support bone marrow regeneration after chemotherapy or radiation-induced injury to prevent prolonged myelosuppression. However, it is not known how stromal cells within the bone marrow are regenerated after injury. We have utilized a whole bone transplantation model that mimics the initial bone marrow necrosis and fatty infiltration that is seen after bone marrow injury and subsequent recovery. We demonstrate that periosteal skeletal stem cells (P-SSCs) can migrate into the bone marrow and contribute to stromal regeneration and hematopoietic recovery. Once in the bone marrow, P-SSCs are phenotypically and functionally reprogrammed into bone marrow mesenchymal stem cells (BM-MSCs), expressing high levels of hematopoietic stem cell (HSC) niche factors, such as Cxcl12 and Kitl. Additionally, our results further indicate that P-SSCs are more resistant to acute stress than BM-MSCs. Here, we report a new function of P-SSCs, highlighting their major plasticity and the role of the periosteum as a potential source of BM-MSCs following acute bone marrow injury.

Osteopontin Splicing Isoforms Contribute to Endometriotic Proliferation, Migration, and Epithelial-Mesenchymal Transition in Endometrial Epithelial Cells

Osteopontin (OPN) isoforms, including OPNb and OPNc, promote malignancy and may contribute to the pathogenesis of endometriosis, a benign disorder with multiple characteristics resembling malignant tumors. In our experiments, OPNb and OPNc were significantly overexpressed in both endometriosis and adenomyosis compared to the normal endometrium. Upregulation of CD44v and the epithelial-mesenchymal transition (EMT) process was also present in endometriotic lesions. Overexpression of OPNb and OPNc splicing variants in endometriotic cells evoked morphological changes, actin remodeling, cell proliferation, cell migration, and EMT through binding OPN ligand receptors CD44 and αvβ3, subsequently activating the PI3K and NF-ĸB pathways. We elucidated the causal role of OPN splice variants in regulating endometriotic cell growth, which may promote the development of OPN-targeted therapies for patients suffering from endometriotic disorders.

Matricellular proteins in cutaneous wound healing

Cutaneous wound healing is a complex process that encompasses alterations in all aspects of the skin including the extracellular matrix (ECM). ECM consist of large structural proteins such as collagens and elastin as well as smaller proteins with mainly regulative properties called matricellular proteins. Matricellular proteins bind to structural proteins and their functions include but are not limited to interaction with cell surface receptors, cytokines, or protease and evoking a cellular response. The signaling initiated by matricellular proteins modulates differentiation and proliferation of cells having an impact on the tissue regeneration. In this review we give an overview of the matricellular proteins that have been found to be involved in cutaneous wound healing and summarize the information known to date about their functions in this process.

A hybrid hydrogel encapsulating human umbilical cord mesenchymal stem cells enhances diabetic wound healing

BACKGROUND

Diabetic wound is a severe complication of diabetes. Stem cell is considered as a promising therapy for diabetic skin wounds. Hydrogel can supply niche for cells adhesion and survival to improve the efficacy of stem cell therapy, but the development of hydrogel with suitable properties remains a great challenge. Thus, our study was conducted to combine an optimized hydrogel with stem cell to improve complex diabetic wound treatment.

METHODS

This study constructed a hydrogel with low toxicity and adjustable mechanical properties from gelatin methacrylate (GelMA) and chitosan-catechol (Chi-C), and encapsulated human umbilical cord-mesenchymal stem cells (hUMSCs) to repair full-thickness diabetic wound.

RESULTS

We explored the relationship between mechanical stiffness and cell proliferation and differentiation potency, and found 10% GelMA hydrogel with an optimal stiffness improved hUMSCs adhesion, proliferation, and differentiation potency maintenance in vitro. Assistant with optimized hydrogel encapsulating hUMSCs, diabetic wound healing process was greatly accelerated, including accelerated wound closure, inhibited secretion of inflammatory factors TNF-α and IL-1β, promoted vascular regeneration and collagen deposition after treatment of hUMSCs.

CONCLUSIONS

The optimized hydrogel encapsulating hUMSCs improved diabetic wound healing, and has a broad implication for the treatment of diabetic complication. Diabetic wound is a severe complication of diabetes. Stem cell is considered as a promising therapy for diabetic skin wounds. Hydrogel can supply niche for cells adhesion and survival to improve the efficacy of stem cell therapy. This study constructed a hydrogel with low toxicity and adjustable mechanical properties from gelatin methacrylate (GelMA) and chitosan-catechol (Chi-C), and encapsulated human umbilical cord-mesenchymal stem cells (hUMSCs) to repair full-thickness diabetic wound. Hydrogel of 10% GelMA with an optimal stiffness improved hUMSCs adhesion, proliferation, and differentiation potency maintenance in vitro. Assistant with optimized hydrogel encapsulating hUMSCs, diabetic wound healing process was greatly accelerated, including accelerated wound closure, inhibited secretion of inflammatory factors TNF-α and IL-1β, promoted vascular regeneration and collagen deposition after treatment of hUMSCs. The study supplies an alternative treatment for diabetic complication. Hydrogel-hUMSCs combined treatment accelerates wound closure in diabetic mice. A. Representative images of wounds during 21-day in vivo experiments. B. Quantification of wound closure rate (%) over 21-day period. C. HE staining of wounds at days 7, 14 and 21. The bar corresponds to 200 μm.

Constant Activation of STAT3 Contributes to the Development of Adenomyosis in Females

Adenomyosis is a benign uterine disease that causes dysmenorrhea, heavy menstrual bleeding, and infertility; however, its pathophysiology remains unclear. Since signal transducer and activator of transcription 3 (STAT3) is crucial for endometrial regeneration, we hypothesized that STAT3 participates in adenomyosis pathophysiology. To investigate the influence of STAT3 on adenomyosis development, this study was performed using a novel mouse model of adenomyosis and human specimens of eutopic endometria and adenomyosis lesions. We established a novel mouse model of adenomyosis by puncturing entire mouse uterine layers with a thin needle. Mouse eutopic and ectopic endometria showed a positive immunoreactivity for phosphorylated STAT3 (pSTAT3), the active form of STAT3. Decreased numbers of adenomyotic lesions and reduced expression of Cxcl1, Icam1, and Spp1, which are associated with immune cell chemotaxis and tissue regeneration, were observed in uterine Stat3-deficient mice compared with the controls. In humans, pSTAT3 was intensely expressed at both the eutopic endometrium and the adenomyotic lesions regardless of the menstrual cycle phases. Conversely, it was limitedly expressed in the eutopic endometrium during the menstrual and proliferative phases in women without adenomyosis. Our findings indicate that continuous STAT3 activation promotes adenomyosis development. STAT3 inhibition can be a promising treatment strategy in patients with adenomyosis.

Exosome loaded genipin crosslinked hydrogel facilitates full thickness cutaneous wound healing in rat animal model

Full thickness cutaneous wound therapy and regeneration remains a critical challenge in clinical therapeutics. Recent reports have suggested that mesenchymal stem cells exosomes therapy is a promising technology with great potential to efficiently promote tissue regeneration. Multifunctional hydrogel composed of both synthetic materials and natural materials is an effective carrier for exosomes loading. Herein, we constructed a biodegradable, dual-sensitive hydrogel encapsulated human umbilical cord-mesenchymal stem cells (hUCMSCs) derived exosomes to facilitate wound healing and skin regeneration process. The materials characterization, exosomes identification, and in vivo full-thickness cutaneous wound healing effect of the hydrogels were performed and evaluated. The in vivo results demonstrated the exosomes loaded hydrogel had significantly improved wound closure, re-epithelialization rates, collagen deposition in the wound sites. More skin appendages were observed in exosomes loaded hydrogel treated wound, indicating the potential to achieve complete skin regeneration. This study provides a new access for complete cutaneous wound regeneration via a genipin crosslinked dual-sensitive hydrogel loading hUCMSCs derived exosomes.

Transcriptional Suppression of Diabetic Nephropathy with Novel Gene Silencer Pyrrole-Imidazole Polyamides Preventing USF1 Binding to the TGF-β1 Promoter

Upstream stimulatory factor 1 (USF1) is a transcription factor that is increased in high-glucose conditions and activates the transforming growth factor (TGF)-β1 promoter. We examined the effects of synthetic pyrrole-imidazole (PI) polyamides in preventing USF1 binding on the TGF-β1 promoter in Wistar rats in which diabetic nephropathy was established by intravenous administration of streptozotocin (STZ). High glucose induced nuclear localization of USF1 in cultured mesangial cells (MCs). In MCs with high glucose, USF1 PI polyamide significantly inhibited increases in promoter activity of TGF-β1 and expression of TGF-β1 mRNA and protein, whereas it significantly decreased the expression of osteopontin and increased that of h-caldesmon mRNA. We also examined the effects of USF1 PI polyamide on diabetic nephropathy. Intraperitoneal injection of USF1 PI polyamide significantly suppressed urinary albumin excretion and decreased serum urea nitrogen in the STZ-diabetic rats. USF1 PI polyamide significantly decreased the glomerular injury score and tubular injury score in the STZ-diabetic rats. It also suppressed the immunostaining of TGF-β1 in the glomerulus and proximal tubules and significantly decreased the expression of TGF-β1 protein from kidney in these rats. These findings indicate that synthetic USF1 PI polyamide could potentially be a practical medicine for diabetic nephropathy.

Adjunctive S100A8/A9 Immunomodulation Hinders Ciprofloxacin Resistance in Pseudomonas aeruginosa in a Murine Biofilm Wound Model

Objective

Pseudomonas aeruginosa is known to contribute to the pathogenesis of chronic wounds by biofilm-establishment with increased tolerance to host response and antibiotics. The neutrophil-factor S100A8/A9 has a promising adjuvant effect when combined with ciprofloxacin, measured by quantitative bacteriology, and increased anti- and lowered pro-inflammatory proteins. We speculated whether a S100A8/A9 supplement could prevent ciprofloxacin resistance in infected wounds.

Method

Full-thickness 2.9cm²-necrosis was inflicted on 32 mice. On day 4, P.aeruginosa in seaweed alginate was injected sub-eschar to mimic a mono-pathogenic biofilm. Mice were randomized to receive ciprofloxacin and S100A8/A9 (n=14), ciprofloxacin (n=12) or saline (n=6). Half of the mice in each group were euthanized day 6 and the remaining day 10 post-infection. Mice were treated until sacrifice. Primary endpoint was the appearance of ciprofloxacin resistant P.aeruginosa. The study was further evaluated by genetic characterization of resistance, means of quantitative bacteriology, wound-size and cytokine-production.

Results

Three mice receiving ciprofloxacin monotherapy developed resistance after 14 days. None of the mice receiving combination therapy changed resistance pattern. Sequencing of fluoroquinolone-resistance determining regions in the ciprofloxacin resistant isolates identified two high-resistant strains mutated in gyrA C248T (MIC>32µg/ml) and a gyr B mutation was found in the sample with low level resistance (MIC=3µg/ml). Bacterial densities in wounds were lower in the dual treated group compared to the placebo group on both termination days.

Conclusion

This study supports the ciprofloxacin augmenting effect and indicates a protective effect in terms of hindered ciprofloxacin resistance of adjuvant S100A8/A9 in P.aeruginosa biofilm infected chronic wounds.

Comprehensive Profiling of Secretome Formulations from Fetal- and Perinatal Human Amniotic Fluid Stem Cells

We previously reported that c-KIT+ human amniotic-fluid derived stem cells obtained from leftover samples of routine II trimester prenatal diagnosis (fetal hAFS) are endowed with regenerative paracrine potential driving pro-survival, anti-fibrotic and proliferative effects. hAFS may also be isolated from III trimester clinical waste samples during scheduled C-sections (perinatal hAFS), thus offering a more easily accessible alternative when compared to fetal hAFS. Nonetheless, little is known about the paracrine profile of perinatal hAFS. Here we provide a detailed characterization of the hAFS total secretome (i.e., the entirety of soluble paracrine factors released by cells in the conditioned medium, hAFS-CM) and the extracellular vesicles (hAFS-EVs) within it, from II trimester fetal- versus III trimester perinatal cells. Fetal- and perinatal hAFS were characterized and subject to hypoxic preconditioning to enhance their paracrine potential. hAFS-CM and hAFS-EV formulations were analyzed for protein and chemokine/cytokine content, and the EV cargo was further investigated by RNA sequencing. The phenotype of fetal- and perinatal hAFS, along with their corresponding secretome formulations, overlapped; yet, fetal hAFS showed immature oxidative phosphorylation activity when compared to perinatal ones. The profiling of their paracrine cargo revealed some differences according to gestational stage and hypoxic preconditioning. Both cell sources provided formulations enriched with neurotrophic, immunomodulatory, anti-fibrotic and endothelial stimulating factors, and the immature fetal hAFS secretome was defined by a more pronounced pro-vasculogenic, regenerative, pro-resolving and anti-aging profile. Small RNA profiling showed microRNA enrichment in both fetal- and perinatal hAFS-EV cargo, with a stably- expressed pro-resolving core as a reference molecular signature. Here we confirm that hAFS represents an appealing source of regenerative paracrine factors; the selection of either fetal or perinatal hAFS secretome formulations for future paracrine therapy should be evaluated considering the specific clinical scenario.

ECM-regulation of autophagy: The yin and the yang of autophagy during wound healing

Wound healing is a complex sequence of tissue protection, replacement, and reorganization leading to regenerated tissue. Disruption of any of these steps results in the process being incomplete as an ulcer or over-exuberant as a hypertrophic scar. Over the past decade, it has become evident that the extracellular matrix and associated components orchestrate this process. However, the cellular events that are induced by the extracellular matrix to accomplish wound healing remain to be defined. Herein we propose that matrix-regulated cellular macro-autophagy is key to both the tissue replacement and resolution stages of healing by directing cellular function or apoptosis. Further, disruptions in matrix turnover alter autophagic function leading to chronic wounds or scarring. While the literature that directly investigates autophagy during wound healing is sparse, the emerging picture supports our proposing a model of the centrality of the matrix-autophagy modulation as central to physiologic and pathologic healing.

The Yin-Yang of osteopontin in nervous system diseases: damage versus repair

Osteopontin is a broadly expressed pleiotropic protein, and is attracting increased attention because of its role in the pathophysiology of several inflammatory, degenerative, autoimmune, and oncologic diseases. In fact, in the last decade, several studies have shown that osteopontin contributes to tissue damage not only by recruiting harmful inflammatory cells to the site of lesion, but also increasing their survival. The detrimental role of osteopontin has been indeed well documented in the context of different neurological conditions (i.e., multiple sclerosis, Parkinson's, and Alzheimer's diseases). Intriguingly, recent findings show that osteopontin is involved not only in promoting tissue damage (the Yin), but also in repair/regenerative mechanisms (the Yang), mostly triggered by the inflammatory response. These two apparently discordant roles are partly related to the presence of different functional domains in the osteopontin molecule, which are exposed after thrombin or metalloproteases cleavages. Such functional domains may in turn activate intracellular signaling pathways and mediate cell-cell and cell-matrix interactions. This review describes the current knowledge on the Yin and Yang features of osteopontin in nervous system diseases. Understanding the mechanisms behind the Yin/Yang would be relevant to develop highly specific tools targeting this multifunctional protein.

Osteopontin Signaling in Shaping Tumor Microenvironment Conducive to Malignant Progression

Context-dependent reciprocal crosstalk between cancer and surrounding stromal cells in the tumor microenvironment is imperative for the regulation of various hallmarks of cancer. A myriad of growth factors, chemokines, and their receptors aids in the interaction between cancer cells and tumor microenvironmental components. Osteopontin is a chemokine-like protein, overexpressed in different types of cancers. Osteopontin plays a crucial role in orchestrating dialogue between cancer and stromal cells. Osteopontin, in tumor microenvironment, is produced in tumor as well as stromal cells. Tumor-derived osteopontin regulates proliferation, migration, activation, and differentiation of different types of stromal cells. Osteopontin secreted from tumor cells regulates the generation of cancer-associated fibroblasts from resident fibroblasts and mesenchymal stem cells. Osteopontin also shapes immunosuppressive tumor microenvironment by controlling regulatory T cells and tumor-associated macrophages. Moreover, secretion of osteopontin from tumor stroma has been highly documented. Stromal cell-derived osteopontin induces epithelial-to-mesenchymal transition, angiogenesis, metastasis, and cancer stem cell enrichment. Tumor- or stroma-derived osteopontin mainly functions through binding with cell surface receptors, integrins and CD44, and activates downstream signaling events like PI-3 kinase/Akt and MAPK pathways. Presumably, disrupting the communication between the tumor cells and surrounding microenvironment by targeting osteopontin-regulated signaling using specific antibodies, small-molecule inhibitors, and chemotherapeutic agents is a novel therapeutic strategy for clinical management of cancer.

Mesenchymal Stem Cells for Chronic Wound Healing: Current Status of Preclinical and Clinical Studies

Healing skin wounds with anatomic and functional integrity, especially under chronic pathological conditions, remain an enormous challenge. Due to their outstanding regenerative potential, mesenchymal stem cells (MSCs) have been explored in many studies to determine the healing ability for difficult-to-treat diseases. In this article, we review current animal studies and clinical trials of MSC-based therapy for chronic wounds, and discuss major challenges that confront future clinical applications. We found that a wealth of animal studies have revealed the versatile roles and the benefits of MSCs for chronic wound healing. MSC treatment results in enhanced angiogenesis, facilitated reepithelialization, improved granulation, and accelerated wound closure. There are some evidences of the transdifferentiation of MSCs into skin cells. However, the healing effect of MSCs depends primarily on their paracrine actions, which alleviate the harsh microenvironment of chronic wounds and regulate local cellular responses. Consistent with the findings of preclinical studies, some clinical trials have shown improved wound healing after transplantation of MSCs in chronic wounds, mainly lower extremity ulcers, pressure sores, and radiation burns. However, there are some limitations in these clinical trials, especially a small number of patients and imperfect methodology. Therefore, to better define the safety and efficiency of MSC-based wound therapy, large-scale controlled multicenter trials are needed in the future. In addition, to build a robust pool of clinical evidence, standardized protocols, especially the cultivation and quality control of MSCs, are recommended. Altogether, based on current data, MSC-based therapy represents a promising treatment option for chronic wounds. Impact statement Chronic wounds persist as a significant health care problem, particularly with increasing number of patients and the lack of efficient treatments. The main goal of this article is to provide an overview of current status of mesenchymal stem cell (MSC)-based therapy for chronic wounds. The roles of MSCs in skin wound healing, as revealed in a large number of animal studies, are detailed. A critical view is made on the clinical application of MSCs for lower extremity ulcers, pressure sores, and radiation burns. Main challenges that confront future clinical applications are discussed, which hopefully contribute to innovations in MSC-based wound treatment.

Exosomes of Antler Mesenchymal Stem Cells Improve Postoperative Cognitive Dysfunction in Cardiopulmonary Bypass Rats through Inhibiting the TLR2/TLR4 Signaling Pathway

Postoperative cognitive dysfunction (POCD) is a severe complication of cardiopulmonary bypass (CPB) and has common characteristics such as acute cognitive dysfunction, impaired memory, and inattention. Mesenchymal stem cells (MSCs) are multipotent cells that have therapeutic potentials mainly through paracrine action via secreting growth factors and cytokines. Exosomes are one of the important paracrine factors and have been reported as potential cell-free therapy for the treatment of autoimmune and central nervous system disorders. In this study, we examined exosomes derived from antler MSCs (AMSCs) of POCD rats after CPB and evaluated their potential regulatory mechanisms. AMSC-derived exosomes reduced neurological damage and brain damage and prevent apoptosis in CPB rats. Furthermore, AMSC-derived exosomes were found to reduce hippocampal neuronal apoptosis and the expression of TLR2, TLR4, MyD88, and NF-κB in CPB rats. However, the above effects of AMSC-derived exosomes on CPB rats were abolished partially by toll-like receptor 2/4 (TLR2/TLR4) agonist (LPS-EB). In conclusion, AMSC-derived exosomes can improve cognitive function in CPB rats through inhibiting the TLR2/TLR4 signaling pathway.

CD44 expression in stem cells and niche microglia/macrophages following ischemic stroke

Background

CD44, an adhesion molecule in the hyaluronate receptor family, plays diverse and important roles in multiple cell types and organs. Increasing evidence is mounting for CD44 expression in various types of stem cells and niche cells surrounding stem cells. However, the precise phenotypes of CD44⁺ cells in the brain under pathologic conditions, such as after ischemic stroke, remain unclear.

Methods

In the present study, using a mouse model for cerebral infarction by middle cerebral artery (MCA) occlusion, we examined the localization and traits of CD44⁺ cells.

Results

In sham-mice operations, CD44 was rarely observed in the cortex of MCA regions. Following ischemic stroke, CD44⁺ cells emerged in ischemic areas of the MCA cortex during the acute phase. Although CD44 at ischemic areas was, in part, expressed in stem cells, it was also expressed in hematopoietic lineages, including activated microglia/macrophages, surrounding the stem cells. CD44 expression in microglia/macrophages persisted through the chronic phase following ischemic stroke.

Conclusions

These data demonstrate that CD44 is expressed in stem cells and cells in the niches surrounding them, including inflammatory cells, suggesting that CD44 may play an important role in reparative processes within ischemic areas under neuroinflammatory conditions; in particular, strokes.

The Tumor Microenvironment: Focus on Extracellular Matrix

The extracellular matrix (ECM) regulates the development and maintains tissue homeostasis. The ECM is composed of a complex network of molecules presenting distinct biochemical properties to regulate cell growth, survival, motility, and differentiation. Among their components, proteoglycans (PGs) are considered one of the main components of ECM. Its composition, biomechanics, and anisotropy are exquisitely tuned to reflect the physiological state of the tissue. The loss of ECM's homeostasis is seen as one of the hallmarks of cancer and, typically, defines transitional events in tumor progression and metastasis. In this chapter, we discuss the types of proteoglycans and their roles in cancer. It has been observed that the amount of some ECM components is increased, while others are decreased, depending on the type of tumor. However, both conditions corroborate with tumor progression and malignancy. Therefore, ECM components have an increasingly important role in carcinogenesis and this leads us to believe that their understanding may be a key in the discovery of new anti-tumor therapies. In this book, the main ECM components will be discussed in more detail in each chapter.

An osteopontin-derived peptide inhibits human hair growth at least in part by decreasing fibroblast growth factor-7 production in outer root sheath keratinocytes

BACKGROUND

Given that unwanted hair growth (hirsutism, hypertrichosis) can cause major psychological distress, new pharmacological treatment strategies with safe and effective hair growth inhibitors that do not destroy the hair follicle (HF) and its stem cells need to be developed.

OBJECTIVES

To establish if osteopontin-derived fragments may modulate human hair growth given that human HFs express the multifunctional, immunomodulatory glycoprotein, osteopontin.

METHODS

Our hypothesis was tested ex vivo and in vivo by using a newly generated, toxicologically well-characterized, modified osteopontin-derived peptide (FOL-005), which binds to the HF.

RESULTS

In organ-cultured human HFs and scalp skin, and in human scalp skin xenotransplants onto SCID mice, FOL-005 treatment (60 nmol L^-1 to 3 μmol L^-1 ) significantly promoted premature catagen development without reducing the number of keratin 15-positive HF stem cells or showing signs of drug toxicity. Genome-wide DNA microarray, quantitative reverse-transcriptase polymerase chain reaction and immunohistochemistry revealed decreased expression of the hair growth promoter, fibroblast growth factor-7 (FGF7) by FOL-005, while cotreatment of HFs with recombinant FGF7 partially abrogated FOL-005-induced catagen promotion.

CONCLUSIONS

With caveats in mind, our study identifies this osteopontin-derived peptide as an effective, novel inhibitory principle for human hair growth ex vivo and in vivo, which deserves systematic clinical testing in hirsutism and hypertrichosis. What's already known about this topic? The treatment of unwanted hair growth (hypertrichosis, hirsutism) lacks pharmacological intervention, with only few and often unsatisfactory treatments available. Osteopontin is prominently expressed in human HFs and has been reported to be elevated during catagen in the murine hair cycle. What does this study add? We tested the effects on hair growth of a novel, osteopontin-derived fragment (FOL-005) ex vivo and in vivo. In human hair follicles, high-dose FOL-005 significantly reduces hair growth both ex vivo and in vivo. What is the translational message? High-dose FOL-005 may provide a new therapeutic opportunity as a treatment for unwanted hair growth.

Cellular and Molecular Mechanisms in the Pathogenesis of Classical, Vascular, and Hypermobile Ehlers‒Danlos Syndromes

The Ehlers‒Danlos syndromes (EDS) constitute a heterogenous group of connective tissue disorders characterized by joint hypermobility, skin abnormalities, and vascular fragility. The latest nosology recognizes 13 types caused by pathogenic variants in genes encoding collagens and other molecules involved in collagen processing and extracellular matrix (ECM) biology. Classical (cEDS), vascular (vEDS), and hypermobile (hEDS) EDS are the most frequent types. cEDS and vEDS are caused respectively by defects in collagen V and collagen III, whereas the molecular basis of hEDS is unknown. For these disorders, the molecular pathology remains poorly studied. Herein, we review, expand, and compare our previous transcriptome and protein studies on dermal fibroblasts from cEDS, vEDS, and hEDS patients, offering insights and perspectives in their molecular mechanisms. These cells, though sharing a pathological ECM remodeling, show differences in the underlying pathomechanisms. In cEDS and vEDS fibroblasts, key processes such as collagen biosynthesis/processing, protein folding quality control, endoplasmic reticulum homeostasis, autophagy, and wound healing are perturbed. In hEDS cells, gene expression changes related to cell-matrix interactions, inflammatory/pain responses, and acquisition of an in vitro pro-inflammatory myofibroblast-like phenotype may contribute to the complex pathogenesis of the disorder. Finally, emerging findings from miRNA profiling of hEDS fibroblasts are discussed to add some novel biological aspects about hEDS etiopathogenesis.

Bone Marrow-Derived CD44+ Cells Migrate to Tissue-Engineered Constructs via SDF-1/CXCR4-JNK Pathway and Aid Bone Repair

Background and Aims

Host-derived cells play crucial roles in the regeneration process of tissue-engineered constructs (TECs) during the treatment of large segmental bone defects (LSBDs). However, their identity, source, and cell recruitment mechanisms remain elusive.

Methods

A complex model was created using mice by combining methods of GFP⁺ bone marrow transplantation (GFP-BMT), parabiosis (GFP⁺-BMT and wild-type mice), and femoral LSBD, followed by implantation of TECs or DBM scaffolds. Postoperatively, the migration of host BM cells was detected by animal imaging and immunofluorescent staining. Bone repair was evaluated by micro-CT. Signaling pathway repressors including AMD3100 and SP600125 associated with the migration of BM CD44⁺ cells were further investigated. In vitro, transwell migration and western-blotting assays were performed to verify the related signaling pathway. In vivo, the importance of the SDF-1/CXCR4-JNK pathway was validated by ELISA, fluorescence-activated cell sorting (FACS), immunofluorescent staining, and RT-PCR.

Results

First, we found that host cells recruited to facilitate TEC-mediated bone repair were derived from bone marrow and most of them express CD44, indicating the significance of CD44 in the migration of bone marrow cells towards donor MSCs. Then, the predominant roles of SDF-1/CXCR4 and downstream JNK in the migration of BM CD44⁺ cells towards TECs were demonstrated.

Conclusion

Together, we demonstrated that during bone repair promoted by TECs, BM-derived CD44⁺ cells were essential and their migration towards TECs could be regulated by the SDF-1/CXCR4-JNK signaling pathway.

Biomimetic matrices for rapidly forming mineralized bone tissue based on stem cell-mediated osteogenesis

Bone regeneration, following fracture, relies on autologous and allogenic bone grafts. However, majority of fracture population consists of older individuals with poor quality bone associated with loss and/or modification of matrix proteins critical for bone formation and mineralization. Allografts suffer from same limitations and carry the risk of delayed healing, infection, immune rejection and eventual fracture. In this work, we apply a synergistic biomimetic strategy to develop matrices that rapidly form bone tissue - a critical aspect of fracture healing of weight bearing bones. Collagen matrices, enhanced with two selected key matrix proteins, osteocalcin (OC) and/or osteopontin (OPN), increased the rate and quantity of synthesized bone matrix by increasing mesenchymal stem/stromal cell (MSC) proliferation, accelerating osteogenic differentiation, enhancing angiogenesis and showing a sustained bone formation response from MSC obtained from a variety of human tissue sources (marrow, fat and umbilical cord). In vivo assessment of OC/OPN mineralized scaffolds in a critical sized-defect rabbit long-bone model did not reveal any foreign body reaction while bone tissue was being formed. We demonstrate a new biomimetic strategy to rapidly form mineralized bone tissue and secure a sustained bone formation response by MSC from multiple sources, thus facilitating faster patient recovery and treatment of non-union fractures in aging and diseased population. Acellular biomimetic matrices elicit bone regeneration response from MSC, obtained from multiple tissue sources, and can be used in variety of scaffolds and made widely available.

Lipid rafts regulate the lamellipodia formation of melanoma A375 cells via actin cytoskeleton-mediated recruitment of β1 and β3 integrin

Lipid rafts, distinct liquid-ordered plasma membrane microdomains, have been shown to regulate tumor cell migration by internalizing and recycling cell-surface proteins. The present study reports that lipid rafts are a prerequisite for lamellipodia formation, which is the first step in the processes of tumor cell migration. The results from the wound-healing assay and immunostaining indicated that lipid rafts were asymmetrically distributed to the leading edge of migrating melanoma A375 cells during lamellipodia formation. When the integrity of lipids rafts was disrupted, lamellipodia formation was inhibited. The investigation of possible molecular mechanisms indicated that lipid rafts recruited β1 and β3 integrins, two important adhesion proteins for cell migration, to the lamellipodia. However, the different distribution characteristics of β1 and β3 integrins implied disparate functions in lamellipodia formation. Further immunostaining experiments showed that the actin cytoskeleton was responsible for lipid raft-mediated β1 and β3 integrin distribution in the lamellipodia. Together, these findings provide novel insights into the regulation of lipid rafts in lamellipodia formation, and suggest that lipid rafts may be novel and attractive targets for cancer therapy.

Adaptive Regulation of Osteopontin Production by Dendritic Cells Through the Bidirectional Interaction With Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) exert immunosuppressive effects on immune cells including dendritic cells (DCs). However, many details of the bidirectional interaction of MSCs with DCs are still unsolved and information on key molecules by which DCs can modulate MSC functions is limited. Here, we report that osteopontin (OPN), a cytokine involved in homeostatic and pathophysiologic responses, is constitutively expressed by DCs and regulated in the DC/MSC cocultures depending on the activation state of MSCs. Resting MSCs promoted OPN production, whereas the production of OPN was suppressed when MSCs were activated by proinflammatory cytokines (i.e., TNF-α, IL-6, and IL-1β). OPN induction required cell-to-cell contact, mediated at least in part, by β1 integrin (CD29). Conversely, activated MSCs inhibited the release of OPN via the production of soluble factors with a major role played by Prostaglandin E₂ (PGE₂). Accordingly, pretreatment with indomethacin significantly abrogated the MSC-mediated suppression of OPN while the direct addition of exogenous PGE₂ inhibited OPN production by DCs. Furthermore, DC-conditioned medium promoted osteogenic differentiation of MSCs with a concomitant inhibition of adipogenesis. These effects were paralleled by the repression of the adipogenic markers PPARγ, adiponectin, and FABP4, and induction of the osteogenic markers alkaline phosphatase, RUNX2, and of the bone-anabolic chemokine CCL5. Notably, blocking OPN activity with RGD peptides or with an antibody against CD29, one of the OPN receptors, prevented the effects of DC-conditioned medium on MSC differentiation and CCL5 induction. Because MSCs have a key role in maintenance of bone marrow (BM) hematopoietic stem cell niche through reciprocal regulation with immune cells, we investigated the possible MSC/DC interaction in human BM by immunohistochemistry. Although DCs (CD1c⁺) are a small percentage of BM cells, we demonstrated colocalization of CD271⁺ MSCs with CD1c⁺ DCs in normal and myelodysplastic BM. OPN reactivity was observed in occasional CD1c⁺ cells in the proximity of CD271⁺ MSCs. Altogether, these results candidate OPN as a signal modulated by MSCs according to their activation status and involved in DC regulation of MSC differentiation.

Cellular therapies and stem cell applications in trauma

BACKGROUND

As the leading cause of mortality in the United States, trauma management have improved drastically over the past few decades with improved resuscitation and hemorrhage control. Stem cells are being used in an attempt to augment healing from trauma.

DATA SOURCES

PubMed and ClinicalTrials.gov were searched for published and registered pre-clinical and clinical trials for the application of stem cells to AKI, ARDS, shock, infection, TBI, wound healing, and bone healing.

CONCLUSIONS

Stem cell therapy for augmentation of healing traumatic injuries appears safe, as demonstrated by completed phase I/II trials. Further large scale studies are needed to assess the clinical efficacy.