Bi-directional exchange of membrane components occurs during co-culture of mesenchymal stem cells and nucleus pulposus cells

Single Mesenchymal Stromal Cell Migration Tracking into Glioblastoma Using Photoconvertible Vesicles

Reliable cell labeling and tracking techniques are imperative for elucidating the intricate and ambiguous interactions between mesenchymal stromal cells (MSCs) and tumors. Here, we explore fluorescent photoconvertible nanoengineered vesicles to study mMSC migration in brain tumors. These 3 μm sized vesicles made of carbon nanoparticles, Rhodamine B (RhB), and polyelectrolytes are readily internalized by cells. The dye undergoes photoconversion under 561 nm laser exposure with a fluorescence blue shift upon demand. The optimal laser irradiation duration for photoconversion was 0.4 ms, which provided a maximal blue shift of the fluorescent signal label without excessive laser exposure on cells. Vesicles modified with an extra polymer layer demonstrated enhanced intracellular uptake without remarkable effects on cell viability, motility, or proliferation. The optimal ratio of 20 vesicles per mMSC was determined. Moreover, the migration of individual mMSCs within 2D and 3D glioblastoma cell (EPNT-5) colonies over 2 days and in vivo tumor settings over 7 days were traced. Our study provides a robust nanocomposite platform for investigating MSC-tumor dynamics and offers insights into envisaged therapeutic strategies. Photoconvertible vesicles also present an indispensable tool for studying complex fundamental processes of cell-cell interactions for a wide range of problems in biomedicine.

Homing of vertebral‐delivered mesenchymal stromal cells for degenerative intervertebral discs repair – an in vivo proof‐of‐concept study

Introduction

Cell transplantation shows promising results for intervertebral disc (IVD) repair, however, contemporary strategies present concerns regarding needle puncture damage, cell retention, and straining the limited nutrient availability. Mesenchymal stromal cell (MSC) homing is a natural mechanism of long-distance cellular migration to sites of damage and regeneration. Previous ex vivo studies have confirmed the potential of MSC to migrate over the endplate and enhance IVD-matrix production. In this study, we aimed to exploit this mechanism to engender IVD repair in a rat disc degeneration model.

Methods

Female Sprague Dawley rats were subjected to coccygeal disc degeneration through nucleus pulposus (NP) aspiration. In part 1; MSC or saline was transplanted into the vertebrae neighboring healthy or degenerative IVD subjected to irradiation or left untouched, and the ability to maintain the IVD integrity for 2 and 4 weeks was assessed by disc height index (DHI) and histology. For part 2, ubiquitously GFP expressing MSC were transplanted either intradiscally or vertebrally, and regenerative outcomes were compared at days 1, 5, and 14 post-transplantation. Moreover, the homing potential from vertebrae to IVD of the GFP⁺ MSC was assessed through cryosection mediated immunohistochemistry.

Results

Part 1 of the study revealed significantly improved maintenance of DHI for IVD vertebrally receiving MSC. Moreover, histological observations revealed a trend of IVD integrity maintenance. Part 2 of the study highlighted the enhanced DHI and matrix integrity for discs receiving MSC vertebrally compared with intradiscal injection. Moreover, GFP rates highlighted MSC migration and integration in the IVD at similar rates as the intradiscally treated cohort.

Conclusion

Vertebrally transplanted MSC had a beneficial effect on the degenerative cascade in their neighboring IVD, and thus potentially present an alternative administration strategy. Further investigation will be needed to determine the long-term effects, elucidate the role of cellular homing versus paracrine signaling, and validate our observations on a large animal model.

Tracking the Endosomal Escape: A Closer Look at Calcein and Related Reporters

Crossing the cellular membrane and delivering active pharmaceuticals or biologicals into the cytosol of cells is an essential step in the development of nanomedicines. One of the most important intracellular processes regarding the cellular uptake of biologicals is the endolysosomal pathway. Sophisticated nanocarriers have been developed overcoming a major hurdle, the endosomal entrapment, and delivering their cargo to the required site of action. In parallel, in vitro assays have been established analyzing the performance of these nanocarriers. Among them, the release of the membrane-impermeable dye calcein has become a popular and straightforward method. It is accessible for most researchers worldwide, allows for rapid conclusions about the release potential, and enables the study of release mechanisms. This review is intended to provide an overview and guidance for scientists applying the calcein release assay. It comprises a survey of several applications in the study of endosomal escape, considerations of potential pitfalls, challenges and limitations of the assay, and a brief summary of complementary methods. Based on this review, we hope to encourage further research groups to take advantage of the calcein release assay for their own purposes and help to create a database for more efficient cross-correlations between nanocarriers. This article is protected by copyright. All rights reserved.

Mesenchymal Stem Cell-Derived Exosomes and Intervertebral Disc Regeneration: Review

Intervertebral disc degeneration (IVDD) is a common cause of lower back pain (LBP), which burdens individuals and society as a whole. IVDD occurs as a result of aging, mechanical trauma, lifestyle factors, and certain genetic abnormalities, leads to loss of nucleus pulposus, alteration in the composition of the extracellular matrix, excessive oxidative stress, and inflammation in the intervertebral disc. Pharmacological and surgical interventions are considered a boon for the treatment of IVDD, but the effectiveness of those strategies is limited. Mesenchymal stem cells (MSCs) have recently emerged as a possible promising regenerative therapy for IVDD due to their paracrine effect, restoration of the degenerated cells, and capacity for differentiation into disc cells. Recent investigations have shown that the pleiotropic effect of MSCs is not related to differentiation capacity but is mediated by the secretion of soluble paracrine factors. Early studies have demonstrated that MSC-derived exosomes have therapeutic potential for treating IVDD by promoting cell proliferation, tissue regeneration, modulation of the inflammatory response, and reduced apoptosis. This paper highlights the current state of MSC-derived exosomes in the field of treatment of IVDD with further possible future developments, applications, and challenges.

Cell therapies for chondral defects of the talus: a systematic review

Background

This systematic review investigated the efficacy and safety of surgical procedures augmented with cell therapies for chondral defects of the talus.

Methods

The present systematic review was conducted according to the 2020 PRISMA guidelines. PubMed, Google scholar, Embase, and Scopus databases were accessed in March 2022. All the clinical trials investigating surgical procedures for talar chondral defects augmented with cell therapies were accessed. The outcomes of interest were to investigate whether surgical procedures augmented with cell therapies promoted improvement in patients reported outcomes measures (PROMs) with a tolerable rate of complications.

Results

Data from 477 procedures were retrieved. At a mean follow-up of 34.8 ± 9.7 months, the Visual Analogic Scale (VAS) improved of 4.4/10 (P = 0.002) and the American Orthopaedic Foot and Ankle Score (AOFAS) of 31.1/100 (P = 0.0001) points. No improvement was found in Tegner score (P = 0.4). Few articles reported data on complications. At last follow-up, the rate of reoperation and failure were 0.06% and 0.03%, respectively. No graft delamination or hypertrophy was observed.

Conclusion

The current evidence suggests that cell therapies may be effective and safe to enhance surgical procedures for chondral defects of the talus. These results should be considered within the limitations of the present study. The current literature should be enriched with randomized controlled clinical trials with larger population size and longer follow-up.

Self-Assembling Peptide Hydrogels as Functional Tools to Tackle Intervertebral Disc Degeneration

Low back pain (LBP), caused by intervertebral disc (IVD) degeneration, is a major contributor to global disability. In its healthy state, the IVD is a tough and well-hydrated tissue, able to act as a shock absorber along the spine. During degeneration, the IVD is hit by a cell-driven cascade of events, which progressively lead to extracellular matrix (ECM) degradation, chronic inflammation, and pain. Current treatments are divided into palliative care (early stage degeneration) and surgical interventions (late-stage degeneration), which are invasive and poorly efficient in the long term. To overcome these limitations, alternative tissue engineering and regenerative medicine strategies, in which soft biomaterials are used as injectable carriers of cells and/or biomolecules to be delivered to the injury site and restore tissue function, are currently being explored. Self-assembling peptide hydrogels (SAPHs) represent a promising class of de novo synthetic biomaterials able to merge the strengths of both natural and synthetic hydrogels for biomedical applications. Inherent features, such as shear-thinning behaviour, high biocompatibility, ECM biomimicry, and tuneable physiochemical properties make these hydrogels appropriate and functional tools to tackle IVD degeneration. This review will describe the pathogenesis of IVD degeneration, list biomaterials requirements to attempt IVD repair, and focus on current peptide hydrogel materials exploited for this purpose.

Exosomes Immunity Strategy: A Novel Approach for Ameliorating Intervertebral Disc Degeneration

Low back pain (LBP), which is one of the most severe medical and social problems globally, has affected nearly 80% of the population worldwide, and intervertebral disc degeneration (IDD) is a common musculoskeletal disorder that happens to be the primary trigger of LBP. The pathology of IDD is based on the impaired homeostasis of catabolism and anabolism in the extracellular matrix (ECM), uncontrolled activation of immunologic cascades, dysfunction, and loss of nucleus pulposus (NP) cells in addition to dynamic cellular and biochemical alterations in the microenvironment of intervertebral disc (IVD). Currently, the main therapeutic approach regarding IDD is surgical intervention, but it could not considerably cure IDD. Exosomes, extracellular vesicles with a diameter of 30–150 nm, are secreted by various kinds of cell types like stem cells, tumor cells, immune cells, and endothelial cells; the lipid bilayer of the exosomes protects them from ribonuclease degradation and helps improve their biological efficiency in recipient cells. Increasing lines of evidence have reported the promising applications of exosomes in immunological diseases, and regarded exosomes as a potential therapeutic source for IDD. This review focuses on clarifying novel therapies based on exosomes derived from different cell sources and the essential roles of exosomes in regulating IDD, especially the immunologic strategy.

Mesenchymal stem cell-derived exosome mediated long non-coding RNA KLF3-AS1 represses autophagy and apoptosis of chondrocytes in osteoarthritis

Osteoarthritis is a degenerative joint disease and a leading cause of adult disability. Our previous study has reported that mesenchymal stem cell-derived exosomes (MSC-Exo) mediated long non-coding RNA KLF3-AS1 improves osteoarthritis. This study aims to investigate the molecular mechanism of KLF3-AS1 in osteoarthritis. Chondrocytes were treated with IL-1β to induce chondrocyte injury, followed by MSC-Exo treatment. We found that MSC-Exo enhanced KLF3-AS1 expression in IL-1β-treated chondrocytes. IL-1β treatment reduced cell viability and enhanced apoptosis in chondrocytes. MSC-Exo-mediated KLF3-AS1 promoted cell viability and repressed apoptosis of IL-1β-treated chondrocytes. Rapamycin (autophagy activator) promoted cell viability and suppressed apoptosis of chondrocytes by activating autophagy. Moreover, KLF3-AS1 interacted with YBX1 in chondrocytes. MSC-Exo-mediated KLF3-AS1 activated PI3K/Akt/mTOR signaling pathway, which was abrogated by YBX1 silencing. MSC-Exo-mediated KLF3-AS1 repressed autophagy and apoptosis of chondrocytes by activating PI3K/Akt/mTOR signaling pathway. In conclusion, our data demonstrate that MSC-Exo-mediated KLF3-AS1 inhibits autophagy and apoptosis of IL-1β-treated chondrocyte through PI3K/Akt/mTOR signaling pathway. KLF3-AS1 activates PI3K/Akt/mTOR signaling pathway by targeting YBX1 to improve the progression of osteoarthritis. Thus, this work suggests that MSC-Exo-mediated KLF3-AS1 may be a potential therapeutic target for osteoarthritis.

Stem cells in intervertebral disc regeneration-more talk than action?

Pain and lifestyle changes are common consequences of intervertebral disc degeneration (IVDD) and affect a large part of the aging population. The stemness of cells is exploited in the field of regenerative medicine as key to treat degenerative diseases. Transplanted cells however often face delivery and survival challenges, especially in tissues with a naturally harsh microniche environment such as the intervertebral disc. Recent interest in the secretome of stem cells, especially cargo protected from microniche-related decay as frequently present in degenerating tissues, provides new means of rejuvenating ailing cells and tissues. Exosomes, a type of extracellular vesicles with purposeful cargo gained particular interest in conveying stem cell related attributes of rejuvenation, which will be discussed here in the context of IVDD.

Probing Multicellular Tissue Fusion of Cocultured Spheroids-A 3D-Bioassembly Model

While decades of research have enriched the knowledge of how to grow cells into mature tissues, little is yet known about the next phase: fusing of these engineered tissues into larger functional structures. The specific effect of multicellular interfaces on tissue fusion remains largely unexplored. Here, a facile 3D-bioassembly platform is introduced to primarily study fusion of cartilage-cartilage interfaces using spheroids formed from human mesenchymal stromal cells (hMSCs) and articular chondrocytes (hACs). 3D-bioassembly of two adjacent hMSCs spheroids displays coordinated migration and noteworthy matrix deposition while the interface between two hAC tissues lacks both cells and type-II collagen. Cocultures contribute to increased phenotypic stability in the fusion region while close initial contact between hMSCs and hACs (mixed) yields superior hyaline differentiation over more distant, indirect cocultures. This reduced ability of potent hMSCs to fuse with mature hAC tissue further underlines the major clinical challenge that is integration. Together, this data offer the first proof of an in vitro 3D-model to reliably study lateral fusion mechanisms between multicellular spheroids and mature cartilage tissues. Ultimately, this high-throughput 3D-bioassembly model provides a bridge between understanding cellular differentiation and tissue fusion and offers the potential to probe fundamental biological mechanisms that underpin organogenesis.

Uncovering the secretome of mesenchymal stromal cells exposed to healthy, traumatic, and degenerative intervertebral discs: a proteomic analysis

BACKGROUND

Mesenchymal stromal cells (MSCs) have been introduced as promising cell source for regenerative medicine. Besides their multilineage differentiation capacity, MSCs release a wide spectrum of bioactive factors. This secretome holds immunomodulatory and regenerative capacities. In intervertebral disc (IVD) cells, application of MSC secretome has been shown to decrease the apoptosis rate, induce proliferation, and promote production of extracellular matrix (ECM). For clinical translation of secretome-based treatment, characterization of the secretome composition is needed to better understand the induced biological processes and identify potentially effective secretomes.

METHODS

This study aimed to investigate the proteome released by bone marrow-derived MSCs following exposure to a healthy, traumatic, or degenerative human IVD environment by mass spectroscopy and quantitative immunoassay analyses. Exposure of MSCs to the proinflammatory stimulus interleukin 1β (IL-1β) was used as control.

RESULTS

Compared to MSC baseline secretome, there were 224 significantly up- or downregulated proteins following healthy, 179 following traumatic, 223 following degenerative IVD, and 160 proteins following IL-1β stimulus. Stimulation of MSCs with IVD conditioned media induced a more complex MSC secretome, involving more biological processes, compared to stimulation with IL-1β. The MSC response to stimulation with IVD conditioned medium was dependent on their pathological status.

CONCLUSIONS

The MSC secretome seemed to match the primary need of the IVD: homeostasis maintenance in the case of healthy IVDs, versus immunomodulation, adjustment of ECM synthesis and degradation disbalance, and ECM (re) organization in the case of traumatic and degenerative IVDs. These findings highlight the importance of cell preconditioning in the development of tailored secretome therapies. The secretome of human bone marrow-derived mesenchymal stromal cells (MSCs) stimulated with intervertebral disc (IVD) conditioned medium was analyzed by proteomic profiling. Depending on the pathological state of the IVD, the MSC secretome protein composition indicated immunomodulatory or anabolic activity of the secretome. These findings may have implications for tailored secretome therapy for the IVD and other tissues.

Extracellular vesicles from human mesenchymal stem cells expedite chondrogenesis in 3D human degenerative disc cell cultures

Background

Extracellular vesicles (EVs) from human mesenchymal stem cells (hMSCs) are known to be mediators of intercellular communication and have been suggested as possible therapeutic agents in many diseases. Their potential use in intervertebral disc (IVD) degeneration associated with low back pain (LBP) is yet to be explored. Since LBP affects more than 85% of the western population resulting in high socioeconomic consequences, there is a demand for exploring new and possibly mini-invasive treatment alternatives. In this study, the effect of hMSC-derived small EVs (sEVs) on degenerated disc cells (DCs) isolated from patients with degenerative discs and chronic LBP was investigated in a 3D in vitro model.

Methods

hMSCs were isolated from bone marrow aspirate, and EVs were isolated from conditioned media of the hMSCs by differential centrifugation and filtration. 3D pellet cultures of DCs were stimulated with the sEVs at 5 × 10¹⁰ vesicles/ml concentration for 28 days and compared to control. The pellets were harvested at days 7, 14, and 28 and evaluated for cell proliferation, viability, ECM production, apoptotic activity, chondrogenesis, and cytokine secretions.

Results

The findings demonstrated that treatment with sEVs from hMSCs resulted in more than 50% increase in cell proliferation and decrease in cellular apoptosis in degenerated DCs from this patient group. ECM production was also observed as early as in day 7 and was more than three times higher in the sEV-treated DC pellets compared to control cultures. Further, sEV treatment suppressed secretion of MMP-1 in the DCs.

Conclusion

hMSC-derived sEVs improved cell viability and expedited chondrogenesis in DCs from degenerated IVDs. These findings open up for new tissue regeneration treatment strategies to be developed for degenerative disorders of the spine.

Exosomal miR-532-5p from bone marrow mesenchymal stem cells reduce intervertebral disc degeneration by targeting RASSF5

The transplantation of bone marrow mesenchymal stem cells (BMSCs) has been found to be used as an effective therapy of intervertebral disc degeneration (IDD). However, the underlying mechanisms of BMSCs in the progress of IDD are not fully explained. In this study, we found that exosomes derived from BMSCs (BMSCs-Exos) inhibited the apoptotic rate, extracellular matrix (ECM) degradation, and fibrosis deposition in TNF-α-induced nucleus pulposus cells (NPCs). Importantly, the level of miR-532-5p was observed to be decreased in apoptotic NPCs, but abundant in BMSCs-Exos with TNF-α treatment. The results showed that BMSCs-Exos under TNF-α stimuli exerted better effects on NPCs than BMSCs-Exos, which might be mitigated by the inhibition of miR-532-5p in BMSCs-Exos. The gain-of-function results suggested that the direct overexpression of miR-532-5p in NPCs could inhibit TNF-α-induced increase of apoptotic process, activation of apoptotic proteins, imbalance of anabolism/catabolism levels, and accumulation of collagen I. In addition, RASSF5 was demonstrated to be a target of miR-532-5p. Knockdown of RASSF5 could decrease the apoptotic cells and reduce the activated apoptotic protein levels in TNF-α-induced NPCs. Overall, these data indicate that exosomes from BMSCs may suppress TNF-α-induced apoptosis, ECM degradation, and fibrosis deposition in NPCs through the delivery of miR-532-5p via targeting RASSF5. This work provides a promising therapeutic strategy for the progress of IDD.

Combinatorial conditioning of adipose derived-mesenchymal stem cells enhances their neurovascular potential: Implications for intervertebral disc degeneration

BACKGROUND

Mesenchymal stem cells (MSCs) are becoming an increasingly attractive option for regenerative therapies due to their availability, self-renewal capacity, multilineage potential, and anti-inflammatory properties. Clinical trials are underway to test the efficacy of stem cell-based therapies for the repair and regeneration of the degenerate intervertebral disc (IVD), a major cause of back pain. Recently, both bone marrow-derived MSCs and adipose-derived stem cells (ASCs) have been assessed for IVD therapy but there is a lack of knowledge surrounding the optimal cell source and the response of transplanted cells to the low oxygen, pro-inflammatory niche of the degenerate disc. Here, we investigated several neurovascular factors from donor-matched MSCs and ASCs that may potentiate the survival and persistence of sensory nerve fibers and blood vessels present within painful degenerate discs and their regulation by oxygen tensions and inflammatory cytokines.

METHODS

Donor-matched ASCs and MSCs were conditioned with either IL-1β or TNFα under normoxic (21% O2) or hypoxic (5% O2) conditions. Expression and secretion of several potent neurovascular factors were assessed using qRT-PCR and human magnetic Luminex assay.

RESULTS

ASCs and MSCs expressed constitutive levels of key neurotrophic factors; and stimulation of ASCs with hypoxia triggered increased secretion of both angiogenic factors (Ang-2 and VEGF-A) and neurotrophic (NGF and NT-3) compared to MSCs. We also report increased transcriptional regulation of pain-associated neuropeptides in hypoxia stimulated ASCs compared to those in normoxic conditions. We demonstrate transcriptional and translational upregulation of NGF, NT-3, Ang-1, and FGF-2 in response to cytokines in ASCs in 21% and 5% O2.

CONCLUSIONS

This work highlights fundamental differences between the neurovascular secretome of donor-matched ASCs and MSCs, demonstrating the importance of cell-selection for tissue specific regeneration to reduce ectopic sensory nerve and blood vessel survival and improve patient outcomes.

Identification of the xenograft and its ascendant sphere-forming cell line as belonging to EBV-induced lymphoma, and characterization of the status of sphere-forming cells

BACKGROUND

We have characterized the human cell line arised from the Epstein-Barr virus (EBV) positive multiple myeloma aspirate subjected to the long-term cultivation. This cell line has acquired the ability to form free-floating spheres and to produce a xenograft upon transplantation into NOD/SCID mice.

METHODS

Cells from both in vitro culture and developed xenografts were investigated with a number of analytical approaches, including pathomorphological analysis, FISH analysis, and analysis of the surface antigens and of the VDJ locus rearrangement.

RESULTS

The obtained results, as well as the confirmed presence of EBV, testify that both biological systems are derived from B-cells, which, in turn, is a progeny of the EBV-transformed B-cellular clone that supplanted the primordial multiple myeloma cells. Next we assessed whether cells that (i) were constantly present in vitro in the investigated cell line, (ii) were among the sphere-forming cells, and (iii) were capable of internalizing a fluorescent TAMRA-labeled DNA probe (TAMRA+ cells) belonged to one of the three types of undifferentiated bone marrow cells of a multiple myeloma patient: CD34+ hematopoietic stem cells, CD90+ mesenchymal stem cells, and clonotypic multiple myeloma cell.

CONCLUSION

TAMRA+ cells were shown to constitute the fourth independent subpopulation of undifferentiated bone marrow cells of the multiple myeloma patient. We have demonstrated the formation of ectopic contacts between TAMRA+ cells and cells of other types in culture, in particular with CD90+ mesenchymal stem cells, followed by the transfer of some TAMRA+ cell material into the contacted cell.

Human Bone Marrow Mesenchymal Stem Cells Rescue Endothelial Cells Experiencing Chemotherapy Stress by Mitochondrial Transfer Via Tunneling Nanotubes

Tunneling nanotubes (TNTs) are newly discovered tubular structures between two distant cells that facilitate the intercellular exchange of signals and components. Recent reports show that mesenchymal stem cells (MSCs) can rescue injured target cells and promote recovery from a variety of stresses via TNT-mediated mitochondrial transfer. In this study, we explored how TNTs form between bone marrow MSCs and endothelial cells (ECs) by using a human umbilical cord vein endothelial cell (HUVEC) model. TNT formation between MSCs and HUVECs could be induced by treating HUVECs with cytarabine (Ara-C), and human bone marrow mesenchymal stem cells (hBMMSCs) could transfer mitochondria to injured HUVECs through TNTs. Mitochondrial transfer from hBMMSCs to HUVECs via TNTs rescued the injured HUVECs by reducing apoptosis, promoting proliferation and restoring the transmembrane migration ability as well as the capillary angiogenic capacity of HUVECs. This study provides novel insights into the cell-cell communication between MSCs and ECs and supports the results of prior studies indicating that ECs promote hematopoietic regeneration. An improved understanding of MSC-EC cross-talk will promote the development of MSC-directed strategies for improving EC function and hematopoietic system regeneration following myelosuppressive and myeloablative injuries.

Exosomes Derived from Human Primed Mesenchymal Stem Cells Induce Mitosis and Potentiate Growth Factor Secretion

Mesenchymal stem cells (MSCs) facilitate functional recovery in numerous animal models of inflammatory and ischemic tissue-related diseases with a growing body of research suggesting that exosomes mediate many of these therapeutic effects. It remains unclear, however, which types of proteins are packaged into exosomes compared with the cells from which they are derived. In this study, using comprehensive proteomic analysis, we demonstrated that human primed MSCs secrete exosomes (pMEX) that are packaged with markedly higher fractions of specific protein subclasses compared with their cells of origin, indicating regulation of their contents. Notably, we found that pMEX are also packaged with substantially elevated levels of extracellular-associated proteins. Fibronectin was the most abundant protein detected, and data established that fibronectin mediates the mitogenic properties of pMEX. In addition, treatment of SHSY5Y cells with pMEX induced the secretion of growth factors known to possess mitogenic and neurotrophic properties. Taken together, our comprehensive analysis indicates that pMEX are packaged with specific protein subtypes, which may provide a molecular basis for their distinct functional properties.

Extracellular vesicles mediate improved functional outcomes in engineered cartilage produced from MSC/chondrocyte cocultures

Several recent studies have demonstrated that coculture of chondrocytes (CHs) with bone marrow-derived mesenchymal stem cells (MSCs) improves their chondrogenesis. This implies that intercellular communication dictates fate decisions in recipient cells and/or reprograms their metabolic state to support a differentiated function. While this coculture phenomenon is compelling, the differential chondroinductivity of zonal CHs on MSC cocultures, the nature of the molecular cargo, and their transport mechanisms remains undetermined. Here, we demonstrate that juvenile CHs in coculture with adult MSCs promote functional differentiation and improved matrix production. We further demonstrate that close proximity between the two cell types is a prerequisite for this response and that the outcome of this interaction improves viability, chondrogenesis, matrix formation, and homeostasis in the recipient MSCs. Furthermore, we visualized the transfer of intracellular contents from CHs to nearby MSCs and showed that inhibition of extracellular vesicle (EV) transfer blocks the synergistic effect of coculture, identifying EVs as the primary mode of communication in these cocultures. These findings will forward the development of therapeutic agents and more effective delivery systems to promote cartilage repair.

Mesenchymal stem cells-microvesicle-miR-451a ameliorate early diabetic kidney injury by negative regulation of P15 and P19

Microvesicles (MVs) from mesenchymal stem cells (MSCs) have been reported as a new communicated way between cells. This study evaluated the influence and underlying mechanism of MVs-shuttled miR-451a on renal fibrosis and epithelial mesenchymal transformation (EMT) in diabetic nephropathy (DN) with hyperuricemia. MVs were isolated from MSCs-cultured medium by gradient ultracentrifugation. The level of miR-451a in MSCs and MVs was analyzed by qPCR. The changes of miR-451a, E-cadherin, α-SMA, P15INK4b (P15), and P19INK4d (P19) were measured in hyperglycosis and hyperuricemia-induced cell (HK-2) and mouse models. The changes of cell cycle were analyzed by flow cytometry. The ability of proliferation and viability was measured by BrdU and CCK8, respectively. Dual-luciferase reporter assays were conducted to determine the target binding sites. The renal function and histological changes of mice were analyzed. MVs showed the same surface markers as MSCs but much higher miR-451a expression (4.87 ± 2.03 fold higher than MSCs). miR-451a was decreased to 26% ± 11% and 6.7% ± 0.82% in injured HK-2 cells and kidney, respectively. MV-miR-451a enhanced the HK2 cells proliferation and viability in vitro, and decreased the morphologic and functional injury of kidney in vivo. Moreover, infusion of MV-miR-451a reduced the level of α-SMA and raised E-cadherin expression. These effects were responsible for the improved arrested cell cycle and down-regulation of P15 and P19 via miR-451a targeting their 3′-UTR sites. This study demonstrated that MSC–MV-miR-451a could inhibit cell cycle inhibitors P15 and P19 to restart the blocked cell cycle and reverse EMT in vivo and in vitro, and thus miR-451a is potentially a new target for DN therapy.

Impact statement

The mechanism of MSCs repairing the injured kidney in diabetic nephropathy is not yet clear. In the research, MVs showed the same surface markers as MSCs but much higher MiR-451a expression. miR-451a was decreased in both injured HK-2 cells and kidneys. MV-miR-451a stimulated the cell proliferation and viability in vitro and promoted structural and functional improvements of injured kidney in vivo. Infusion of MV-miR-451a ameliorated EMT by reducing α-SMA and increasing E-cadherin. These effects relied on the improved cell cycle arrest and the down-regulation of P15 and P19 via miR-451a binding to their 3′-UTR region. This study demonstrated that MSC–MV-miR-451a could specifically inhibit cell cycle inhibitors to restart the blocked cell cycle and reverse EMT in vivo and in vitro. Therefore, miR-451a may be a new target for DN therapy.

Mesenchymal Stromal Cell Secretome: Influencing Therapeutic Potential by Cellular Pre-conditioning

Mesenchymal stromal cells (MSCs) are self-renewing, culture-expandable adult stem cells that have been isolated from a variety of tissues, and possess multipotent differentiation capacity, immunomodulatory properties, and are relatively non-immunogenic. Due to this unique set of characteristics, these cells have attracted great interest in the field of regenerative medicine and have been shown to possess pronounced therapeutic potential in many different pathologies. MSCs' mode of action involves a strong paracrine component resulting from the high levels of bioactive molecules they secrete in response to the local microenvironment. For this reason, MSCs' secretome is currently being explored in several clinical contexts, either using MSC-conditioned media (CM) or purified MSC-derived extracellular vesicles (EVs) to modulate tissue response to a wide array of injuries. Rather than being a constant mixture of molecular factors, MSCs' secretome is known to be dependent on the diverse stimuli present in the microenvironment that MSCs encounter. As such, the composition of the MSCs' secretome can be modulated by preconditioning the MSCs during in vitro culture. This manuscript reviews the existent literature on how preconditioning of MSCs affects the therapeutic potential of their secretome, focusing on MSCs' immunomodulatory and regenerative features, thereby providing new insights for the therapeutic use of MSCs' secretome.

Autogenic mesenchymal stem cells for intervertebral disc regeneration

PURPOSE

A systematic review of the literature was conducted to clarify the outcomes of autologous mesenchymal stem cells (MSC) injections for the regeneration of the intervertebral disc (IVD).

METHODS

The following databases were accessed: PubMed, Medline, CINAHL, Cochrane, Embase and Google Scholar bibliographic databases. Articles including previous or planned surgical interventions were excluded. Only articles reporting percutaneous autologous MSC injection to regenerate IVD in humans were included. We referred to the Coleman Methodology Score for the methodological quality assessment. The statistical analysis was performed using Review Manager Software 5.3.

RESULTS

After the databases search and cross-references of the bibliographies, seven studies were included in the present work. The funnel plot detected low risk of publication bias. The Coleman Methodology Score reported a good result, scoring 61.07 points. A total of 98 patients were enrolled, with 122 treated levels. All the patients underwent conservative therapies prior to injection. A remarkable improvement in the quality of life were reported after the treatment. The average Oswestry Disability Index (ODI) improved from "severe disability" to "minimal disability" at one year follow-up. The visual analogue scale (VAS) showed an improvement of ca. 30% at one year follow-up. Only one case of herniated nucleus pulposus was reported. No other adverse events at the aspiration or injection site were observed.

CONCLUSIONS

This systematic review of the literature proved MSC injection to be a safe and feasible option for intervertebral disc regeneration in the early-degeneration stage patients. Irrespective of the source of the MSCs, an overall clinical and radiological improvement of the patients has been evidenced, as indeed a very low complication rate during the follow-up.

Transforming growth factor β mediates communication of co-cultured human nucleus pulposus cells and mesenchymal stem cells

Intervertebral disc (IVD) consists of surrounding tissue annulus fibrosus and central nucleus pulposus, which are partially degenerative in scoliotic IVDs. Successful regeneration of scoliotic alterations requires cognition of critical paracrine mediators of cell-to-cell contact in the IVD. In this work, we hypothesized that transforming growth factor β (TGF-β) is involved in the intercellular communication of nucleus pulposus cells (NPCs) and mesenchymal stem cells (MSCs). We observed that in cultured NPCs TGF-β1 stimulated COL1A1 expression, encoding collagen I, and in MSCs stimulated COL1A1 and SOX9 expressions. We subsequently co-cultured NPCs and MSCs together using direct and indirect transwell systems. The expression of miR-140 and miR-145 were decreased in co-cultured NPCs. We observed that direct co-culture system stronger than the indirect system decreased expression of three miRNA. The expression of COL1A1, ACAN, encoding aggrecan, and SOX9 genes was increased in MSCs co-cultured with NPCs. Co-cultures were incubated with two inhibitors of TGF-β type I receptor: SB-431542 and SB-525334. In co-cultured NPCs, SB-431542 and SB-525334 annulated downregulation of miR-140 and miR-145. In MSCs these inhibitors diminished stimulation of COL1A1, ACAN, and SOX9. We concluded that stimulation of COL1A1, ACAN, and SOX9 in co-cultured MSCs and regulation of miR-140 and miR-145 in NPCs were TGF-β-dependent and TGF-β is involved in the communication of NPCs and MSCs in co-culture. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3023-3032, 2018.

Induction of Expression of CD271 and CD34 in Mesenchymal Stromal Cells Cultured as Spheroids

Cultured mesenchymal stromal cells (MSCs) are cells that can be used for tissue engineering or cell therapies owing to their multipotency and ability to secrete immunomodulatory and trophic molecules. Several studies suggest that MSCs can become pericytes when cocultured with endothelial cells (ECs) but failed to use pericyte markers not already expressed by MSCs. We hypothesized ECs could instruct MSCs to express the molecules CD271 or CD34, which are expressed by pericytes in situ but not by MSCs. CD271 is a marker of especial interest because it is associated with multipotency, a characteristic that wanes in MSCs as they are culture expanded. Consequently, surface expression of CD271 and CD34 was detected in roughly half of the MSCs cocultured with ECs as spheroids in the presence of insulin-like growth factor 1 (IGF-1). Conversely, expression of CD271 and CD34 was detected in a similar proportion of MSCs cultured under these conditions without ECs, and expression of these markers was low or absent when no IGF-1 was added. These findings indicate that specific culture conditions including IGF-1 can endow cultured MSCs with expression of CD271 and CD34, which may enhance the multipotency of these cells when they are used for therapeutic purposes.

Mesenchymal stem cells deliver exogenous miR-21 via exosomes to inhibit nucleus pulposus cell apoptosis and reduce intervertebral disc degeneration

Although mesenchymal stem cells (MSCs) transplantation into the IVD (intervertebral disc) may be beneficial in inhibiting apoptosis of nucleus pulposus cells (NPCs) and alleviating IVD degeneration, the underlying mechanism of this therapeutic process has not been fully explained. The purpose of this study was to explore the protective effect of MSC‐derived exosomes (MSC‐exosomes) on NPC apoptosis and IVD degeneration and investigate the regulatory effect of miRNAs in MSC‐exosomes and associated mechanisms for NPC apoptosis. MSC‐exosomes were isolated from MSC medium, and its anti‐apoptotic effect was assessed in a cell and rat model. The down‐regulated miRNAs in apoptotic NPCs were identified, and their contents in MSC‐exosomes were detected. The target genes of eligible miRNAs and possible downstream pathway were investigated. Purified MSC‐exosomes were taken up by NPCs and suppressed NPC apoptosis. The levels of miR‐21 were down‐regulated in apoptotic NPCs while MSC‐exosomes were enriched in miR‐21. The exosomal miR‐21 could be transferred into NPCs and alleviated TNF‐α induced NPC apoptosis by targeting phosphatase and tensin homolog (PTEN) through phosphatidylinositol 3‐kinase (PI3K)‐Akt pathway. Intradiscal injection of MSC‐exosomes alleviated the NPC apoptosis and IVD degeneration in the rat model. In conclusion, MSC‐derived exosomes prevent NPCs from apoptotic process and alleviate IVD degeneration, at least partly, via miR‐21 contained in exosomes. Exosomal miR‐21 restrains PTEN and thus activates PI3K/Akt pathway in apoptotic NPCs. Our work confers a promising therapeutic strategy for IVD degeneration.

Exosomes as potential alternatives to stem cell therapy for intervertebral disc degeneration: in-vitro study on exosomes in interaction of nucleus pulposus cells and bone marrow mesenchymal stem cells

Background

The stem cell-based therapies for intervertebral disc degeneration have been widely studied. However, the mechanisms of mesenchymal stem cells interacting with intervertebral disc cells, such as nucleus pulposus cells (NPCs), remain unknown. Exosomes as a vital paracrine mechanism in cell–cell communication have been highly focused on. The purpose of this study was to detect the role of exosomes derived from bone marrow mesenchymal stem cells (BM-MSCs) and NPCs in their interaction with corresponding cells.

Methods

The exosomes secreted by BM-MSCs and NPCs were purified by differential centrifugation and identified by transmission electron microscope and immunoblot analysis of exosomal marker proteins. Fluorescence confocal microscopy was used to examine the uptake of exosomes by recipient cells. The effects of NPC exosomes on the migration and differentiation of BM-MSCs were determined by transwell migration assays and quantitative RT-PCR analysis of NPC phenotypic genes. Western blot analysis was performed to examine proteins such as aggrecan, sox-9, collagen II and hif-1α in the induced BM-MSCs. Proliferation and the gene expression profile of NPCs induced by BM-MSC exosomes were measured by Cell Counting Kit-8 and qRT-PCR analysis, respectively.

Results

Both the NPCs and BM-MSCs secreted exosomes, and these exosomes underwent uptake by the corresponding cells. NPC-derived exosomes promoted BM-MSC migration and induced BM-MSC differentiation to a nucleus pulposus-like phenotype. BM-MSC-derived exosomes promoted NPC proliferation and healthier extracellular matrix production in the degenerate NPCs.

Conclusion

Our study indicates that the exosomes act as an important vehicle in information exchange between BM-MSCs and NPCs. Given a variety of functions and multiple advantages, exosomes alone or loaded with specific genes and drugs would be an appropriate option in a cell-free therapy strategy for intervertebral disc degeneration.

Intervertebral disc response to stem cell treatment is conditioned by disc state and cell carrier: An ex vivo study

In vitro and in vivo studies evidenced that mesenchymal stem cells (MSCs) contribute to intervertebral disc (IVD) regeneration by differentiation towards the disc phenotype and matrix synthesis and/or by paracrine signalling to endogenous cells, thereby promoting a healthier disc phenotype in degenerative discs. The aim of this study was to investigate IVD response to human MSC (hMSC) treatment based on the disc degenerative state and hMSC carrier. Bovine caudal IVDs with endplates were cultured in a bioreactor under simulated physiological (0.1 Hz load and sufficient glucose) or degenerative (10 Hz load and limited glucose) conditions for 7 days. Discs were partially nucleotomised, restored with hMSCs in either fibrin gel or saline solution and cultured under physiological conditions for 7 days. Controls included fibrin and saline without hMSCs. Cell viability, histology, disc height, and gene expression analyses were performed to evaluate regeneration. hMSCs in fibrin were viable and homogenously distributed following 7 days of culture under dynamic loading in partially nucleotomised discs. IVD response to hMSCs was conditioned by both disc degenerative state and hMSC carrier. The effect of the regenerative treatment was stronger on simulated-degenerative discs than on simulated-physiological discs. hMSCs in fibrin induced a superior anabolic response in degenerative IVDs compared with fibrin alone, thus suggesting an added value of the cellular therapy compared with an acellular solution. When comparing fibrin and saline as a hMSC carrier, a significantly higher anabolic response was observed in IVDs treated with hMSCs in fibrin. Moreover, it was found that the degenerative state of the disc influenced hMSC differentiation. Indeed, a significantly higher expression of specific discogenic markers (ACAN and CA12) was observed in hMSCs implanted into physiological discs than in those implanted into degenerative discs. In conclusion, host disc cells and donor hMSC response depend on the degenerative state of the host disc and carrier used for hMSC delivery, and these two aspects need to be considered for a successful translation of hMSC therapies for the treatment of IVD degeneration.

RNA in situ hybridization characterization of non-enzymatic derived bovine intervertebral disc cell lineages suggests progenitor cell potential

Degeneration of the intervertebral disc (IVD) is a meritorious target for therapeutic cell based regenerative medicine approaches, however, controversy over what defines the precise identity of mature IVD cells and lack of single cell based quality control measures is of concern. Bos taurus and human IVDs are histologically more similar than is Mus musculus. The mature bovine IVD is well suited as model system for technology development to be translated into therapeutic cell based regenerative medicine applications. We present a reproducible non-enzymatic protocol to isolate cell progenitor populations of three distinct areas of the mature bovine IVD. Bovine specific RNA probes were validated in situ and employed to assess fate changes, heterogeneity, stem cell characteristics and differentiation potential of the cultures. Quality control measures with single cell resolution like RNA in situ hybridization to assess culture heterogeneity (PISH) followed by optimization of culture conditions could be translated to human IVD cell culture to increase the safety of cell based regenerative medicine.

Cell-based therapies for intervertebral disc and cartilage regeneration- Current concepts, parallels, and perspectives

Lower back pain from degenerative disc disease represents a global health burden, and presents a prominent opportunity for regenerative therapeutics. While current regenerative therapies such as autologous disc chondrocyte transplantation (ADCT), allogeneic juvenile chondrocyte implantation (NuQu®), and immunoselected allogeneic adipose derived precursor cells (Mesoblast) show exciting clinical potential, limitations remain. The heterogeneity of preclinical approaches and the paucity of clinical guidance have limited translational outcomes in disc repair, lagging almost a decade behind cartilage repair. Advances in cartilage repair have evolved to single step approaches with improved orthopedic repair and regeneration. Elements from cartilage regeneration endeavors could be adopted and applied to harness translatable approaches and deliver a clinically and economically feasible regenerative surgery for back pain. In this article, we trace the developments behind the translational success of cartilage repair, examine elements to consider in achieving disc regeneration, and the need for surgical redesign. We further discuss clinical parameters, objectives, and coordination required to deliver improved regenerative surgery. Cell source, processing, and delivery modalities are key issues to be addressed in considering surgical redesign. Advances in biomanufacturing, tissue cryobanking, and point of care cell processing technology may enable intraoperative solutions for single step procedures. To maximize translational success a triad partnership between clinicians, industry, and researchers will be critical in providing instructive clinical guidelines for design as well as practical and economic considerations. This will allow a consensus in research ventures and add regenerative surgery into the algorithm in managing and treating a debilitating condition such as back pain. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:8-22, 2017.

Effects of cell type and configuration on anabolic and catabolic activity in 3D co-culture of mesenchymal stem cells and nucleus pulposus cells

Tissue engineering constructs to treat intervertebral disc degeneration must adapt to the hypoxic and inflammatory degenerative disc microenvironment. The objective of this study was to determine the effects of two key design factors, cell type and cell configuration, on the regenerative potential of nucleus pulposus cell (NPC) and mesenchymal stem cell (MSC) constructs. Anabolic and catabolic activity was quantified in constructs of varying cell type (NPCs, MSCs, and a 50:50 co-culture) and varying configuration (individual cells and micropellets). Anabolic and catabolic outcomes were both dependent on cell type. Gene expression of Agg and Col2A1, glycosaminoglycan (GAG) content, and aggrecan immunohistochemistry (IHC), were significantly higher in NPC-only and co-culture groups than in MSC-only groups, with NPC-only groups exhibiting the highest anabolic gene expression levels. However, NPC-only constructs also responded to inflammation and hypoxia with significant upregulation of catabolic genes (MMP-1, MMP-9, MMP-13, and ADAMTS-5). MSC-only groups were unaffected by degenerative media conditions, and co-culture with MSCs modulated catabolic induction of the NPCs. Culturing cells in a micropellet configuration dramatically reduced catabolic induction in co-culture and NPC-only groups. Co-culture micropellets, which take advantage of both cell type and configuration effects, had the most immunomodulatory response, with a significant decrease in MMP-13 and ADAMTS-5 expression in hypoxic and inflammatory media conditions. Co-culture micropellets were also found to self-organize into bilaminar formations with an MSC core and NPC outer layer. Further understanding of these cell type and configuration effects can improve tissue engineering designs. © 2016 The Authors. Journal of Orthopaedic Research published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 35:61-73, 2017.

Lost in translation: applying 2D intercellular communication via tunneling nanotubes in cell culture to physiologically relevant 3D microenvironments

Tunneling nanotubes (TNTs) are membranous conduits for direct cell-to-cell communication. Until the past decade, little had been known about their composite structure, function, and mechanisms of action in both normal physiologic conditions as well as in disease states. Now TNTs are attracting increasing interest for their key role(s) in the pathogenesis of disease, including neurodegenerative disorders, inflammatory and infectious diseases, and cancer. The field of TNT biology is still in its infancy, but inroads have been made in determining potential mechanisms and function of these remarkable structures. For example, TNTs function as critical conduits for cellular exchange of information; thus, in cancer, they may play an important role in critical pathophysiologic features of the disease, including cellular invasion, metastasis, and emergence of chemotherapy drug resistance. Although the TNT field is still in a nascent stage, we propose that TNTs can be investigated as novel targets for drug-based treatment of cancer and other diseases.

Systemic Delivery of Bone Marrow Mesenchymal Stem Cells for In Situ Intervertebral Disc Regeneration

Cell therapies for intervertebral disc (IVD) regeneration presently rely on transplantation of IVD cells or stem cells directly to the lesion site. Still, the harsh IVD environment, with low irrigation and high mechanical stress, challenges cell administration and survival. In this study, we addressed systemic transplantation of allogeneic bone marrow mesenchymal stem cells (MSCs) intravenously into a rat IVD lesion model, exploring tissue regeneration via cell signaling to the lesion site. MSC transplantation was performed 24 hours after injury, in parallel with dermal fibroblasts as a control; 2 weeks after transplantation, animals were killed. Disc height index and histological grading score indicated less degeneration for the MSC‐transplanted group, with no significant changes in extracellular matrix composition. Remarkably, MSC transplantation resulted in local downregulation of the hypoxia responsive GLUT‐1 and in significantly less herniation, with higher amounts of Pax5+ B lymphocytes and no alterations in CD68+ macrophages within the hernia. The systemic immune response was analyzed in the blood, draining lymph nodes, and spleen by flow cytometry and in the plasma by cytokine array. Results suggest an immunoregulatory effect in the MSC‐transplanted animals compared with control groups, with an increase in MHC class II+ and CD4+ cells, and also upregulation of the cytokines IL‐2, IL‐4, IL‐6, and IL‐10, and downregulation of the cytokines IL‐13 and TNF‐α. Overall, our results indicate a beneficial effect of systemically transplanted MSCs on in situ IVD regeneration and highlight the complex interplay between stromal cells and cells of the immune system in achieving successful tissue regeneration. Stem Cells Translational Medicine2017;6:1029–1039

Quantification of the asymmetric migration of the lipophilic dyes, DiO and DiD, in homotypic co-cultures of chondrosarcoma SW-1353 cells

DiO and DiD are lipophilic cell labelling dyes used in the staining of cells in vivo and in vitro. The aim of the present study was to quantify the asymmetrical distribution of dyes in co-cultured cells and to measure the intercellular transfer of DiO and DiD. DiO and DiD were applied separately to stain two identical populations of SW-1353 human chondrosarcoma cells that were subsequently co-cultured (homotypic co-culture). The intercellular migration of dyes in the co-cultured cells was measured by flow cytometry and recorded under a fluorescent microscope. DiD and DiO caused no effect on the proliferation of cells, the degradation rate of the two dyes was comparable and crossover effects between dyes were negligible. The results of the present study suggested that asymmetrical intercellular migration of DiD and DiO was responsible for the asymmetrical distribution of these dyes in co-cultured cells. To take advantage of the lipophilic dyes migration in the double-stained co-cultured cells we suggest to apply mixed-dyes controls prior to the flow cytometric analysis. These controls are performed by staining cells with a 1:1 mix of the two dyes and would enable the estimation of the intensity of intercellular contact in co-culture systems. A 1:1 premix of DiO and DiD was applied to estimate cellular effect on intercellular exchange of lipid dyes in co-cultures incubated with cycloheximide and cytochalasin B. The cellular effect contributed 6–7% of intercellular migration of the lipophilic dyes, DiO and DiD. The majority of the observed intercellular transfer of these dyes was due to non-cellular, passive transfer.

Thermally triggered injectable hydrogel, which induces mesenchymal stem cell differentiation to nucleus pulposus cells: Potential for regeneration of the intervertebral disc

There is an urgent need for new therapeutic options for low back pain, which target degeneration of the intervertebral disc (IVD). Here, we investigated a pNIPAM hydrogel system, which is liquid at 39°C ex vivo, where following injection into the IVD, body temperature triggers gelation. The combined effects of hypoxia (5% O2) and the structural environment of the hydrogel delivery system on the differentiation of human mesenchymal stem cells (hMSCs), towards an NP cell phenotype was investigated. hMSCs were incorporated into the liquid hydrogel, the mixture solidified and cultured for up to 6weeks under 21% O2 or 5% O2 where viability was maintained. Immunohistochemistry revealed significant increases in NP matrix components: aggrecan; collagen type II and chondroitin sulphate after culture for 1week in 5% O2, accompanied by increased matrix staining for proteoglycans and collagen, observed histologically. NP markers HIF1α, PAX1 and FOXF1 were also significantly increased where hMSC were incorporated into hydrogels with accelerated expression observed when cultured in 5% O2. hMSCs cultured under hypoxic conditions, which mimic the native disc microenvironment, accelerate differentiation of hMSCs within the hydrogel system, towards the NP phenotype without the need for chondrogenic inducing medium or additional growth factors, thus simplifying the treatment strategy for the repair of IVD degeneration.

Mesenchymal Stem/Stromal Cells in Stromal Evolution and Cancer Progression

The study of cancer biology has mainly focused on malignant epithelial cancer cells, although tumors also contain a stromal compartment, which is composed of stem cells, tumor-associated fibroblasts (TAFs), endothelial cells, immune cells, adipocytes, cytokines, and various types of macromolecules comprising the extracellular matrix (ECM). The tumor stroma develops gradually in response to the needs of epithelial cancer cells during malignant progression initiating from increased local vascular permeability and ending to remodeling of desmoplastic loosely vascularized stromal ECM. The constant bidirectional interaction of epithelial cancer cells with the surrounding microenvironment allows damaged stromal cell usage as a source of nutrients for cancer cells, maintains the stroma renewal thus resembling a wound that does not heal, and affects the characteristics of tumor mesenchymal stem/stromal cells (MSCs). Although MSCs have been shown to coordinate tumor cell growth, dormancy, migration, invasion, metastasis, and drug resistance, recently they have been successfully used in treatment of hematopoietic malignancies to enhance the effect of total body irradiation-hematopoietic stem cell transplantation therapy. Hence, targeting the stromal elements in combination with conventional chemotherapeutics and usage of MSCs to attenuate graft-versus-host disease may offer new strategies to overcome cancer treatment failure and relapse of the disease.

Horizontal gene transfer from macrophages to ischemic muscles upon delivery of naked DNA with Pluronic block copolymers

Intramuscular administration of plasmid DNA (pDNA) with non-ionic Pluronic block copolymers increases gene expression in injected muscles and lymphoid organs. We studied the role of immune cells in muscle transfection upon inflammation. Local inflammation in murine hind limb ischemia model (MHLIM) drastically increased DNA, RNA and expressed protein levels in ischemic muscles injected with pDNA/Pluronic. The systemic inflammation (MHLIM or peritonitis) also increased expression of pDNA/Pluronic in the muscles. When pDNA/Pluronic was injected in ischemic muscles the reporter gene, Green Fluorescent Protein (GFP) co-localized with desmin(+) muscle fibers and CD11b(+) macrophages (MØs), suggesting transfection of MØs along with the muscle cells. P85 enhanced (∼ 4 orders) transfection of MØs with pDNA in vitro. Moreover, adoptively transferred MØs were shown to pass the transgene to inflamed muscle cells in MHLIM. Using a co-culture of myotubes (MTs) and transfected MØs expressing a reporter gene under constitutive (cmv-luciferase) or muscle specific (desmin-luciferase) promoter we demonstrated that P85 enhances horizontal gene transfer from MØ to MTs. Therefore, MØs can play an important role in muscle transfection with pDNA/Pluronic during inflammation, with both inflammation and Pluronic contributing to the increased gene expression. pDNA/Pluronic has potential for therapeutic gene delivery in muscle pathologies that involve inflammation.

Mesenchymal stem cells in regenerative medicine: Focus on articular cartilage and intervertebral disc regeneration

Musculoskeletal disorders represent a major cause of disability and morbidity globally and result in enormous costs for health and social care systems. Development of cell-based therapies is rapidly proliferating in a number of disease areas, including musculoskeletal disorders. Novel biological therapies that can effectively treat joint and spine degeneration are high priorities in regenerative medicine. Mesenchymal stem cells (MSCs) isolated from bone marrow (BM-MSCs), adipose tissue (AD-MSCs) and umbilical cord (UC-MSCs) show considerable promise for use in cartilage and intervertebral disc (IVD) repair. This review article focuses on stem cell-based therapeutics for cartilage and IVD repair in the context of the rising global burden of musculoskeletal disorders. We discuss the biology MSCs and chondroprogenitor cells and specifically focus on umbilical cord/Wharton's jelly derived MSCs and examine their potential for regenerative applications. We also summarize key components of the molecular machinery and signaling pathways responsible for the control of chondrogenesis and explore biomimetic scaffolds and biomaterials for articular cartilage and IVD regeneration. This review explores the exciting opportunities afforded by MSCs and discusses the challenges associated with cartilage and IVD repair and regeneration. There are still many technical challenges associated with isolating, expanding, differentiating, and pre-conditioning MSCs for subsequent implantation into degenerate joints and the spine. However, the prospect of combining biomaterials and cell-based therapies that incorporate chondrocytes, chondroprogenitors and MSCs leads to the optimistic view that interdisciplinary approaches will lead to significant breakthroughs in regenerating musculoskeletal tissues, such as the joint and the spine in the near future.

Stem Cell Approaches to Intervertebral Disc Regeneration: Obstacles from the Disc Microenvironment

Intervertebral disc (IVD) degeneration results in segmental instability and irritates neural compressive symptoms, such as low back pain and motor deficiency. The transplanting of stem cell into degenerative discs has attracted increasing clinical attention, as a new and proven approach to alleviating disc degeneration and to relieving discogenic pains. Aside from supplementation with stem cells, the IVD itself already contains a pool of stem and progenitor cells. Since the resident disc stem cells are incapable of reversing the pathologic changes that occur during aging and disc degeneration, it has been debated as to whether transplanted stem cells are capable of providing an efficient and durable therapeutic effect, even though there have been positive outcomes in both animal models and in clinical trials. This review aims to decipher the interactions between the stem cell and the disc microenvironment. Within their new niches in the IVD, the exogenous stem cell shows metabolic adaptation to the low-glucose supply, hypoxia, and compressive loadings, but demonstrates little tolerance to the disc-like acidity and hypertonicity. Similarly, the survival of endogenous stem cells is threatened as well by the harsh disc microenvironment, which may exhaust the stem cell resources and restrict the self-repair capacity of a degenerating IVD. To eliminate the intrinsic obstacles within the stressful disc niches, stem cells should be delivered with an injectable scaffold that provides both survival and mechanical support. Quick healing or concretion of the injection injuries, which minimizes stem cell leakage and disturbance to disc homeostasis, is of equal importance toward achieving efficient stem cell-based disc regeneration.

Advancing the cellular and molecular therapy for intervertebral disc disease

The healthy intervertebral disc (IVD) fulfils the essential function of load absorption, while maintaining multi-axial flexibility of the spine. The interrelated tissues of the IVD, the annulus fibrosus, the nucleus pulposus, and the cartilaginous endplate, are characterised by their specific niche, implying avascularity, hypoxia, acidic environment, low nutrition, and low cellularity. Anabolic and catabolic factors balance a slow physiological turnover of extracellular matrix synthesis and breakdown. Deviations in mechanical load, nutrient supply, cellular activity, matrix composition and metabolism may initiate a cascade ultimately leading to tissue dehydration, fibrosis, nerve and vessel ingrowth, disc height loss and disc herniation. Spinal instability, inflammation and neural sensitisation are sources of back pain, a worldwide leading burden that is challenging to cure. In this review, advances in cell and molecular therapy, including mobilisation and activation of endogenous progenitor cells, progenitor cell homing, and targeted delivery of cells, genes, or bioactive factors are discussed.

Mesenchymal stem cell-mediated suppression of hypertrophic scarring is p53 dependent in a rabbit ear model

Introduction

Mesenchymal stem cells (MSCs) are considered to play important roles in wound repair and tissue remodeling. Hypertrophic scar (HTS) is a cutaneous condition characterized by deposits of excessive amount of collagen after an acute skin injury. However, currently there is little knowledge about the direct relationship between MSCs and HTS.

Methods

The hypertrophic scar model was established on rabbit ears. MSCs were isolated from rabbit femur bone marrow and transplanted through ear artery injection. Hypertrophic scar formation was examined using frozen-section analysis, hematoxylin and eosin (HE) staining, Masson’s trichrome staining, and scar elevation index. The role of p53 in the MSCs-mediated anti-scarring effect was examined by gene knockdown using p53 shRNA.

Results

In this study, MSCs engraftment through ear artery injection significantly inhibited the hypertrophic scarring in a rabbit ear hypertrophic scar model, while this anti-scarring function could be abrogated by p53 gene knockdown in MSCs. Additionally, we found that MSCs down-regulated the expression of TGF-β receptor I (TβRI) and alpha-smooth muscle actin (α-SMA) at both mRNA and protein levels in a paracrine manner, and this down-regulation was rescued by p53 gene knockdown. Moreover, our results showed that MSCs with p53 gene knockdown promoted the proliferation of fibroblasts through increasing nitric oxide (NO) production.

Conclusions

These results suggest that MSCs inhibit the formation of HTS in a p53 dependent manner through at least two mechanisms: inhibition of the transformation of HTS fibroblast to myofibroblast; and inhibition of the proliferation of fibroblasts through inhibition of NO production.

Intercellular communication in malignant pleural mesothelioma: properties of tunneling nanotubes

Malignant pleural mesothelioma is a particularly aggressive and locally invasive malignancy with a poor prognosis despite advances in understanding of cancer cell biology and development of new therapies. At the cellular level, cultured mesothelioma cells present a mesenchymal appearance and a strong capacity for local cellular invasion. One important but underexplored area of mesothelioma cell biology is intercellular communication. Our group has previously characterized in multiple histological subtypes of mesothelioma a unique cellular protrusion known as tunneling nanotubes (TnTs). TnTs are long, actin filament-based, narrow cytoplasmic extensions that are non-adherent when cultured in vitro and are capable of shuttling cellular cargo between connected cells. Our prior work confirmed the presence of nanotube structures in tumors resected from patients with human mesothelioma. In our current study, we quantified the number of TnTs/cell among various mesothelioma subtypes and normal mesothelial cells using confocal microscopic techniques. We also examined changes in TnT length over time in comparison to cell proliferation. We further examined potential approaches to the in vivo study of TnTs in animal models of cancer. We have developed novel approaches to study TnTs in aggressive solid tumor malignancies and define fundamental characteristics of TnTs in malignant mesothelioma. There is mounting evidence that TnTs play an important role in intercellular communication in mesothelioma and thus merit further investigation of their role in vivo.

Evidence for Transfer of Membranes from Mesenchymal Stem Cells to HL-1 Cardiac Cells

This study examined the interaction of mouse bone marrow mesenchymal stem cells (MSC) with cardiac HL-1 cells during coculture by fluorescent dye labeling and then flow cytometry. MSC were layered onto confluent HL-1 cell cultures in a 1 : 4 ratio. MSC gained gap junction permeant calcein from HL-1 cells after 4 hours which was partially reduced by oleamide. After 20 hours, 99% MSC gained calcein, unaffected by oleamide. Double-labeling HL-1 cells with calcein and the membrane dye DiO resulted in transfer of both calcein and DiO to MSC. When HL-1 cells were labeled with calcein and MSC with DiO, MSC gained calcein while HL-1 cells gained DiO. Very little fusion was observed since more than 90% Sca-1 positive MSC gained DiO from HL-1 cells while less than 9% gained gap junction impermeant CMFDA after 20 hours with no Sca-1 transfer to HL-1 cells. Time dependent transfer of membrane DiD was observed from HL-1 cells to MSC (100%) and vice versa (50%) after 20 hours with more limited transfer of CMFDA. These results demonstrate that MSC and HL-1 cells exchange membrane components which may account for some of the beneficial effect of MSC in the heart after myocardial infarction.

Mesenchymal stem cells: potential application in intervertebral disc regeneration

Chronic low back pain is one of the leading public health problems in developed countries. Degeneration of the intervertebral disc (IVD) is a major pathological process implicated in low back pain, which is characterized by cellular apoptosis and senescence with reduced synthesis of extracellular matrix (ECM). Currently, there is no clinical therapy targeting the reversal of disc degeneration. Recent advances in cellular and molecular biology have provided an exciting approach to disc regeneration that focuses on the delivery of viable cells to the degenerative disc. Adult mesenchymal stem cells (MSCs) are multipotent stem cells with self-renewal capacities and are able to differentiate into diverse specialized cell types, including chondrocyte lineages. The potential of stem cell therapy in disc degeneration is to repopulate the disc with viable cells capable of producing the ECM and restoring damaged tissue. The present literature review summarizes recent advances in basic research and clinical trials of MSCs to provide an outline of the key roles of MSCs therapies in disc repair. The review also discusses the controversies, challenges and therapeutic concepts for the future.

Potential regenerative treatment strategies for intervertebral disc degeneration in dogs

Pain due to spontaneous intervertebral disc (IVD) disease is common in dogs. In chondrodystrophic (CD) dogs, IVD disease typically develops in the cervical or thoracolumbar spine at about 3–7 years of age, whereas in non-chondrodystrophic (NCD) dogs, it usually develops in the caudal cervical or lumbosacral spine at about 6–8 years of age. IVD degeneration is characterized by changes in the biochemical composition and mechanical integrity of the IVD. In the degenerated IVD, the content of glycosaminoglycan (GAG, a proteoglycan side chain) decreases and that of denatured collagen increases. Dehydration leads to tearing of the annulus fibrosus (AF) and/or disc herniation, which is clinically characterized by pain and/or neurological signs. Current treatments (physiotherapy, anti-inflammatory/analgesic medication, surgery) for IVD disease may resolve neurological deficits and reduce pain (although in many cases insufficient), but do not lead to repair of the degenerated disc. For this reason, there is interest in new regenerative therapies that can repair the degenerated disc matrix, resulting in restoration of the biomechanical function of the IVD. CD dogs are considered a suitable animal model for human IVD degeneration because of their spontaneous IVD degeneration, and therefore studies investigating cell-, growth factor-, and/or gene therapy-based regenerative therapies with this model provide information relevant to both human and canine patients. The aim of this article is to review potential regenerative treatment strategies for canine IVD degeneration, with specific emphasis on cell-based strategies.