Radio-resistant mesenchymal stem cells: mechanisms of resistance and potential implications for the clinic

Research Progress on the Application of Injectable Hydrogel in Oral Tissue Regeneration

BACKGROUND

Oral and maxillofacial tissue defects resulting from factors such as trauma or infection, can significantly impact both facial function and aesthetics. Additionally, the complex anatomical structure of the face often increases the difficulty of treatment. With the advantages of controlled release, targeted delivery, and enhanced mechanical properties, injectable hydrogels have been investigated for the treatment of oral and maxillofacial diseases. In the field of regeneration, injectable hydrogels have a structure similar to the extracellular matrix (ECM) and are biocompatible, which can be used as scaffolds for tissue regeneration.

OBJECTIVE

This review aims to summarize the literature on the current status and limitations of injectable hydrogels in the field of oral tissue regeneration.

METHODS

We searched Pubmed and Web of Science databases to find and summarize the articles on the application of injectable hydrogels in tissue regeneration.

CONCLUSIONS

This review focuses on the current status and limitations of injectable hydrogels in the field of tissue regeneration (periodontal tissue, dentin-pulp complex, bone and cartilage, salivary gland regeneration, and mucosal repair). Although fully studied in animal models, there are still challenges in clinical transformation of injectable hydrogels in promoting tissue regeneration.

Molecular mechanisms of poor osseointegration in irradiated bone: In vivo study in a rat tibia model

AIM

Radiotherapy is associated with cell depletion and loss of blood supply, which are linked to compromised bone healing. However, the molecular events underlying these effects at the tissue-implant interface have not been fully elucidated. This study aimed to determine the major molecular mediators associated with compromised osseointegration due to previous exposure to radiation.

MATERIALS AND METHODS

Titanium implants were placed in rat tibiae with or without pre-exposure to 20 Gy irradiation. Histomorphometric, biomechanical, quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay analyses were performed at 1 and 4 weeks after implantation.

RESULTS

The detrimental effects of irradiation were characterized by reduced bone-implant contact and removal torque. Furthermore, pre-exposure to radiation induced different molecular dysfunctions such as (i) increased expression of pro-inflammatory (Tnf) and osteoclastic (Ctsk) genes and decreased expression of the bone formation (Alpl) gene in implant-adherent cells; (ii) increased expression of bone formation (Alpl and Bglap) genes in peri-implant bone; and (iii) increased expression of pro-inflammatory (Tnf) and pro-fibrotic (Tgfb1) genes in peri-implant soft tissue. The serum levels of pro-inflammatory, bone formation and bone resorption proteins were greater in the irradiated rats.

CONCLUSIONS

Irradiation causes the dysregulation of multiple biological activities, among which perturbed inflammation seems to play a common role in hindering osseointegration.

Hematopoietic Stem Cells and Their Niche in Bone Marrow

Extensive research has explored the functional correlation between stem cells and progenitor cells, particularly in blood. Hematopoietic stem cells (HSCs) can self-renew and regenerate tissues within the bone marrow, while stromal cells regulate tissue function. Recent studies have validated the role of mammalian stem cells within specific environments, providing initial empirical proof of this functional phenomenon. The interaction between bone and blood has always been vital to the function of the human body. It was initially proposed that during evolution, mammalian stem cells formed a complex relationship with the surrounding microenvironment, known as the niche. Researchers are currently debating the significance of molecular-level data to identify individual stromal cell types due to incomplete stromal cell mapping. Obtaining these data can help determine the specific activities of HSCs in bone marrow. This review summarizes key topics from previous studies on HSCs and their environment, discussing current and developing concepts related to HSCs and their niche in the bone marrow.

Salivary gland regeneration: from salivary gland stem cells to three-dimensional bioprinting

Hyposalivation and severe dry mouth syndrome are the most common complications in patients with head and neck cancer (HNC) after receiving radiation therapy. Conventional treatment for hyposalivation relies on the use of sialogogues such as pilocarpine; however, their efficacy is constrained by the limited number of remnant acinar cells after radiation. After radiotherapy, the salivary gland (SG) secretory parenchyma is largely destroyed, and due to the reduced stem cell niche, this gland has poor regenerative potential. To tackle this, researchers must be able to generate highly complex cellularized 3D constructs for clinical transplantation via technologies, including those that involve bioprinting of cells and biomaterials. A potential stem cell source with promising clinical outcomes to reserve dry mouth is adipose mesenchymal stem cells (AdMSC). MSC-like cells like human dental pulp stem cells (hDPSC) have been tested in novel magnetic bioprinting platforms using nanoparticles that can bind cell membranes by electrostatic interaction, as well as their paracrine signals arising from extracellular vesicles. Both magnetized cells and their secretome cues were found to increase epithelial and neuronal growth of in vitro and ex vivo irradiated SG models. Interestingly, these magnetic bioprinting platforms can be applied as a high-throughput drug screening system due to the consistency in structure and functions of their organoids. Recently, exogenous decellularized porcine ECM was added to this magnetic platform to stimulate an ideal environment for cell tethering, proliferation, and/or differentiation. The combination of these SG tissue biofabrication strategies will promptly allow for in vitro organoid formation and establishment of cellular senescent organoids for aging models, but challenges remain in terms of epithelial polarization and lumen formation for unidirectional fluid flow. Current magnetic bioprinting nanotechnologies can provide promising functional and aging features to in vitro craniofacial exocrine gland organoids, which can be utilized for novel drug discovery and/or clinical transplantation.

ROS-sensitive Crocin-loaded chitosan microspheres for lung targeting and attenuation of radiation-induced lung injury

Radiation-induced lung injury (RILI) is one of the major complications in patients exposed to accidental radiation and radiotherapy for thoracic malignancies. However, there is no reliable radioprotector for effective clinical treatment of RILI so far. Herein, a novel Crocin-loaded chitosan microsphere is developed for lung targeting and attenuation of RILI. The chitosan microspheres are modified with 4-carboxyphenylboronic acid and loaded with the natural antioxidant Crocin-I to give the drug-loaded microspheres (~10 μm). The microspheres possess good biocompatibility in vivo and in vitro. In a mouse model, they exhibit effective passive targeting performance and a long retention time in the lung after intravenous administration. Furthermore, they improve the radioprotective effect of Crocin-I for the treatment of RILI by reducing the level of inflammatory cytokines in bronchoalveolar lavage fluid and by regulating oxidative stress in lung tissues. The targeted agents significantly improved the bioavailability and radioprotection of Crocin-I by the outstanding passive targeting effect. This work may provide a promising strategy for efficient radioprotection on RILI using passive lung targeting microspheres.

The cellular composition and function of the bone marrow niche after allogeneic hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative therapy for patients with a variety of malignant and non-malignant diseases. Despite its life-saving potential, HCT is associated with significant morbidity and mortality. Reciprocal interactions between hematopoietic stem cells (HSCs) and their surrounding bone marrow (BM) niche regulate HSC function during homeostatic hematopoiesis as well as regeneration. However, current pre-HCT conditioning regimens, which consist of high-dose chemotherapy and/or irradiation, cause substantial short- and long-term toxicity to the BM niche. This damage may negatively affect HSC function, impair hematopoietic regeneration after HCT and predispose to HCT-related morbidity and mortality. In this review, we summarize current knowledge on the cellular composition of the human BM niche after HCT. We describe how pre-HCT conditioning affects the cell types in the niche, including endothelial cells, mesenchymal stromal cells, osteoblasts, adipocytes, and neurons. Finally, we discuss therapeutic strategies to prevent or repair conditioning-induced niche damage, which may promote hematopoietic recovery and improve HCT outcome.

Human Mesenchymal Stromal Cells Do Not Cause Radioprotection of Head-and-Neck Squamous Cell Carcinoma

Radiotherapy of head-and-neck squamous cell carcinoma (HNSCC) can cause considerable normal tissue injuries, and mesenchymal stromal cells (MSCs) have been shown to aid regeneration of irradiation-damaged normal tissues. However, utilization of MSC-based treatments for HNSCC patients undergoing radiotherapy is hampered by concerns regarding potential radioprotective effects. We therefore investigated the influence of MSCs on the radiosensitivity of HNSCCs. Several human papillomavirus (HPV)-negative and HPV-positive HNSCCs were co-cultured with human bone marrow-derived MSCs using two-dimensional and three-dimensional assays. Clonogenic survival, proliferation, and viability of HNSCCs after radiotherapy were assessed depending on MSC co-culture. Flow cytometry analyses were conducted to examine the influence of MSCs on irradiation-induced cell cycle distribution and apoptosis induction in HNSCCs. Immunofluorescence stainings of γH2AX were conducted to determine the levels of residual irradiation-induced DNA double-strand breaks. Levels of connective tissue growth factor (CTGF), a multifunctional pro-tumorigenic cytokine, were analyzed using enzyme-linked immunosorbent assays. Neither direct MSC co-culture nor MSC-conditioned medium exerted radioprotective effects on HNSCCs as determined by clonogenic survival, proliferation, and viability assays. Consistently, three-dimensional microwell arrays revealed no radioprotective effects of MSCs. Irradiation resulted in a G2/M arrest of HNSCCs at 96 h independently of MSC co-culture. HNSCCs’ apoptosis rates were increased by irradiation irrespective of MSCs. Numbers of residual γH2AX foci after irradiation with 2 or 8 Gy were comparable between mono- and co-cultures. MSC mono-cultures and HNSCC-MSC co-cultures exhibited comparable CTGF levels. We did not detect radioprotective effects of human MSCs on HNSCCs. Our results suggest that the usage of MSC-based therapies for radiotherapy-related toxicities in HNSCC patients may be safe in the context of absent radioprotection.

Evidence for Recombinant GRP78, CALR, PDIA3 and GPI as Mediators of Genetic Instability in Human CD34+ Cells

Soluble factors released from irradiated human mesenchymal stromal cells (MSC) may induce genetic instability in human CD34+ cells, potentially mediating hematologic disorders. Recently, we identified four key proteins in the secretome of X-ray-irradiated MSC, among them three endoplasmic reticulum proteins, the 78 kDa glucose-related protein (GRP78), calreticulin (CALR), and protein disulfide-isomerase A3 (PDIA3), as well as the glycolytic enzyme glucose-6-phosphate isomerase (GPI). Here, we demonstrate that exposition of CD34+ cells to recombinant GRP78, CALR, PDIA3 and GPI induces substantial genetic instability. Increased numbers of γH2AX foci (p < 0.0001), centrosome anomalies (p = 0.1000) and aberrant metaphases (p = 0.0022) were detected in CD34+ cells upon incubation with these factors. Specifically, γH2AX foci were found to be induced 4−5-fold in response to any individual of the four factors, and centrosome anomalies by 3−4 fold compared to control medium, which contained none of the recombinant proteins. Aberrant metaphases, not seen in the context of control medium, were detected to a similar extent than centrosome anomalies across the four factors. Notably, the strongest effects were observed when all four factors were collectively provided. In summary, our data suggest that specific components of the secretome from irradiated MSC act as mediators of genetic instability in CD34+ cells, thereby possibly contributing to the pathogenesis of radiation-induced hematologic disorders beyond direct radiation-evoked DNA strand breaks.

Bone Marrow Adiposity in Models of Radiation- and Aging-Related Bone Loss Is Dependent on Cellular Senescence

Oxidative stress-induced reactive oxygen species, DNA damage, apoptosis, and cellular senescence have been associated with reduced osteoprogenitors in a reciprocal fashion to bone marrow adipocyte tissue (BMAT); however, a direct (causal) link between cellular senescence and BMAT is still elusive. Accumulation of senescent cells occur in naturally aged and in focally radiated bone tissue, but despite amelioration of age- and radiation-associated bone loss after senescent cell clearance, molecular events that precede BMAT accrual are largely unknown. Here we show by RNA-Sequencing data that BMAT-related genes were the most upregulated gene subset in radiated bones of C57BL/6 mice. Using focal radiation as a model to understand age-associated changes in bone, we performed a longitudinal assessment of cellular senescence and BMAT. Using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), RNA in situ hybridization of p21 transcripts and histological assessment of telomere dysfunction as a marker of senescence, we observed an increase in senescent cell burden of bone cells from day 1 postradiation, without the presence of BMAT. BMAT was significantly elevated in radiated bones at day 7, confirming the qRT-PCR data in which most BMAT-related genes were elevated by day 7, and the trend continued until day 42 postradiation. Similarly, elevation in BMAT-related genes was observed in bones of aged mice. The senolytic cocktail of Dasatinib (D) plus Quercetin (Q) (ie, D + Q), which clears senescent cells, reduced BMAT in aged and radiated bones. MicroRNAs (miRNAs or miRs) linked with senescence marker p21 were downregulated in radiated and aged bones, whereas miR-27a, a miR that is associated with increased BMAT, was elevated both in radiated and aged bones. D + Q downregulated miR-27a in radiated bones at 42 days postradiation. Overall, our study provides evidence that BMAT occurrence in oxidatively stressed bone environments, such as radiation and aging, is induced following a common pathway and is dependent on the presence of senescent cells. © 2022 American Society for Bone and Mineral Research (ASBMR).

MSCs in Space: Mesenchymal Stromal Cell Therapeutics as Enabling Technology for Long-Distance Manned Space Travel

Purpose of Review

Advancements in space travel, such as space tourism into Earth’s orbit, but also the prospect of long-distance manned space travel to other celestial bodies such as Mars, has generated a clinical need for new enabling technologies to support the long-term well-being of humans during their passage. Here, we will give an outline on the clinical need and practical considerations to MSC therapy as enabling technology for long-distance manned space travel.

Recent Findings

Long-distance space travel entails a threat to the health of astronaut crews due to the low gravity environment and exposure to toxic radiation in space. Multi-organ-system degenerative changes, such as decline in musculoskeletal, hematopoietic, immune system function, and in particular risk of genetic mutations and cancer, are major health concerns. Physical training, pharmacological agents, and protective shielding are among the currently available methods to counteract harmful effects. However, a potential lack of adequate shielding, side effects of pharmacological compounds, and limitations to physical training suggest a need for new countermeasures, to protect space travellers to the best extent. Here, the prospect of cell-based therapy, e.g. mesenchymal stromal/stem cells (MSCs), has been subject to intense research, due to their potent regenerative and immunomodulatory properties. Off-the-shelf MSC therapeutics can be easily maintained in space due to the ambient extremely low-temperature environment, and cryorecovery and even culturing of MSCs under microgravity were shown to be feasible.

Summary

Designing new therapy against harmful radiation is urgent need in space travel. Here we will discuss aspects related to clinical MSC administration to optimize their therapeutic benefit. MSC-based therapy may aid in evolving protective countermeasures for space travellers.

Refining the mandibular osteoradionecrosis rat model by in vivo longitudinal µCT analysis

Osteoradionecrosis (ORN) is one of the most feared side effects of radiotherapy following cancers of the upper aero-digestive tract and leading to severe functional defects in patients. Today, our lack of knowledge about the physiopathology restricts the development of new treatments. In this study, we refined the ORN rat model and quantitatively studied the progression of the disease. We tested the impact of radiation doses from 20 to 40 Gy, delivered with incident 4MV X-ray beams on the left mandible of the inbred Lewis Rat. We used micro-computed tomography (µCT) to obtain in vivo images for longitudinal bone imaging and ex vivo images after animal perfusion with barium sulphate contrast agent for vessel imaging. We compared quantification methods by analyzing 3D images and 2D measurements to determine the most appropriate and precise method according to the degree of damage. We defined 25 Gy as the minimum irradiation dose combined with the median molar extraction necessary to develop non-regenerative bone necrosis. µCT image analyses were correlated with clinical and histological analyses. This refined model and accurate methods for bone and vessel quantification will improve our knowledge of the progression of ORN pathology and allow us to test the efficacy of new regenerative medicine procedures.

Sclerostin antibody increases trabecular bone and bone mechanical properties by increasing osteoblast activity damaged by whole-body irradiation in mice

Irradiation therapy causes bone deterioration and increased risk for skeletal-related events. Irradiation interferes with trabecular architecture through increased osteoclastic activity, decreased osteoblastic activity, and increased adipocyte expansion in the bone marrow (BM), which further compounds bone-related disease. Neutralizing antibodies to sclerostin (Scl-Ab) increase bone mass and strength by increasing bone formation and reducing bone resorption. We hypothesized that treatment with Scl-Ab would attenuate the adverse effects of irradiation by increasing bone volume and decreasing BM adipose tissue (BMAT), resulting in better quality bone. In this study, 12-week-old female C57BL/6J mice were exposed to 6 Gy whole-body irradiation or were non-irradiated, then administered Scl-Ab (25 mg/kg) or vehicle weekly for 5 weeks. Femoral μCT analysis confirmed that the overall effect of IR significantly decreased trabecular bone volume/total volume (Tb.BV/TV) (2-way ANOVA, p < 0.0001) with a -43.8% loss in Tb.BV/TV in the IR control group. Scl-Ab independently increased Tb.BV/TV by 3.07-fold in non-irradiated and 3.6-fold in irradiated mice (2-way ANOVA, p < 0.0001). Irradiation did not affect cortical parameters, although Scl-Ab increased cortical thickness and area significantly in both irradiated and non-irradiated mice (2-way ANOVA, p < 0.0001). Femoral mechanical testing confirmed Scl-Ab significantly increased bending rigidity and ultimate moment independently of irradiation (2-way ANOVA, p < 0.0001). Static and dynamic histomorphometry of the femoral metaphysis revealed osteoblast vigor, not number, was significantly increased in the irradiated mice treated with Scl-Ab. Systemic alterations were assessed through serum lipidomic analysis, which showed that Scl-Ab normalized lipid profiles in the irradiated group. This data supports the theory of sclerostin as a novel contributor to the regulation of osteoblast activity after irradiation. Overall, our data support the hypothesis that Scl-Ab ameliorates the deleterious effects of whole-body irradiation on bone and adipose tissue in a mouse model. Our findings suggest that future research into localized and systemic therapies after irradiation exposure is warranted.

Extracellular Vesicles for the Treatment of Radiation Injuries

Normal tissue injury from accidental or therapeutic exposure to high-dose radiation can cause severe acute and delayed toxicities, which result in mortality and chronic morbidity. Exposure to single high-dose radiation leads to a multi-organ failure, known as acute radiation syndrome, which is caused by radiation-induced oxidative stress and DNA damage to tissue stem cells. The radiation exposure results in acute cell loss, cell cycle arrest, senescence, and early damage to bone marrow and intestine with high mortality from sepsis. There is an urgent need for developing medical countermeasures against radiation injury for normal tissue toxicity. In this review, we discuss the potential of applying secretory extracellular vesicles derived from mesenchymal stromal/stem cells, endothelial cells, and macrophages for promoting repair and regeneration of organs after radiation injury.

CD40 Activity on Mesenchymal Cells Negatively Regulates OX40L to Maintain Bone Marrow Immune Homeostasis Under Stress Conditions

Background

Within the bone marrow (BM), mature T cells are maintained under homeostatic conditions to facilitate proper hematopoietic development. This homeostasis depends upon a peculiar elevated frequency of regulatory T cells (Tregs) and immune regulatory activities from BM-mesenchymal stem cells (BM-MSCs). In response to BM transplantation (BMT), the conditioning regimen exposes the BM to a dramatic induction of inflammatory cytokines and causes an unbalanced T-effector (Teff) and Treg ratio. This imbalance negatively impacts hematopoiesis, particularly in regard to B-cell lymphopoiesis that requires an intact cross-talk between BM-MSCs and Tregs. The mechanisms underlying the ability of BM-MSCs to restore Treg homeostasis and proper B-cell development are currently unknown.

Methods

We studied the role of host radio-resistant cell-derived CD40 in restoring Teff/Treg homeostasis and proper B-cell development in a murine model of BMT. We characterized the host cellular source of CD40 and performed radiation chimera analyses by transplanting WT or Cd40-KO with WT BM in the presence of T-reg and co-infusing WT or - Cd40-KO BM-MSCs. Residual host and donor T cell expansion and activation (cytokine production) and also the expression of Treg fitness markers and conversion to Th17 were analyzed. The presence of Cd40+ BM-MSCs was analyzed in a human setting in correlation with the frequency of B-cell precursors in patients who underwent HSCT and variably developed acute graft-versus-host (aGVDH) disease.

Results

CD40 expression is nearly undetectable in the BM, yet a Cd40-KO recipient of WT donor chimera exhibited impaired B-cell lymphopoiesis and Treg development. Lethal irradiation promotes CD40 and OX40L expression in radio-resistant BM-MSCs through the induction of pro-inflammatory cytokines. OX40L favors Teff expansion and activation at the expense of Tregs; however, the expression of CD40 dampens OX40L expression and restores Treg homeostasis, thus facilitating proper B-cell development. Indeed, in contrast to dendritic cells in secondary lymphoid organs that require CD40 triggers to express OX40L, BM-MSCs require CD40 to inhibit OX40L expression.

Conclusions

CD40+ BM-MSCs are immune regulatory elements within BM. Loss of CD40 results in uncontrolled T cell activation due to a reduced number of Tregs, and B-cell development is consequently impaired. GVHD provides an example of how a loss of CD40+ BM-MSCs and a reduction in B-cell precursors may occur in a human setting.

The Particle Radiobiology of Multipotent Mesenchymal Stromal Cells: A Key to Mitigating Radiation-Induced Tissue Toxicities in Cancer Treatment and Beyond?

Mesenchymal stromal cells (MSCs) comprise a heterogeneous population of multipotent stromal cells that have gained attention for the treatment of irradiation-induced normal tissue toxicities due to their regenerative abilities. As the vast majority of studies focused on the effects of MSCs for photon irradiation-induced toxicities, little is known about the regenerative abilities of MSCs for particle irradiation-induced tissue damage or the effects of particle irradiation on the stem cell characteristics of MSCs themselves. MSC-based therapies may help treat particle irradiation-related tissue lesions in the context of cancer radiotherapy. As the number of clinical proton therapy centers is increasing, there is a need to decidedly investigate MSC-based treatments for particle irradiation-induced sequelae. Furthermore, therapies with MSCs or MSC-derived exosomes may also become a useful tool for manned space exploration or after radiation accidents and nuclear terrorism. However, such treatments require an in-depth knowledge about the effects of particle radiation on MSCs and the effects of MSCs on particle radiation-injured tissues. Here, the existing body of evidence regarding the particle radiobiology of MSCs as well as regarding MSC-based treatments for some typical particle irradiation-induced toxicities is presented and critically discussed.

Mesenchymal Stem Cells Early Response to Low-Dose Ionizing Radiation

Introduction

Mesenchymal stem cells (MSCs) are applied as the therapeutic agents, e.g., in the tumor radiation therapy.

Purpose of the Study

To evaluate the human adipose MSC early response to low-dose ionizing radiation (LDIR).

Materials and Methods

We investigated different LDIR (3, 10, and 50 cGy) effects on reactive oxygen species production, DNA oxidation (marker 8-oxodG), and DNA breaks (marker ɣ H2AX) in the two lines of human adipose MSC. Using reverse transcriptase-polymerase chain reaction, fluorescence-activated cell sorting, and fluorescence microscopy, we determined expression of genes involved in the oxidative stress development (NOX4), antioxidative response (NRF2), antiapoptotic and proapoptotic response (BCL2, BCL2A1, BCL2L1, BIRC2, BIRC3, and BAX1), in the development of the nuclear DNA damage response (DDR) (BRCA1, BRCA2, ATM, and P53). Cell cycle changes were investigated by genes transcription changes (CCND1, CDKN2A, and CDKN1A) and using proliferation markers KI-67 and proliferating cell nuclear antigen (PCNA).

Results

Fifteen to 120 min after exposure to LDIR in MSCs, transient oxidative stress and apoptosis of the most damaged cells against the background of the cell cycle arrest were induced. Simultaneously, DDR and an antiapoptotic response were found in other cells of the population. The 10-cGy dose causes the strongest and fastest DDR following cell nuclei DNA damage. The 3-cGy dose induces a less noticeable and prolonged response. The maximal low range dose, 50 cGy, causes a damaging effect on the MSCs.

Conclusion

Transient oxidative stress and the death of a small fraction of the damaged cells are essential components of the MSC population response to LDIR along with the development of DDR and antiapoptotic response. A scheme describing the early MSC response to LDIR is proposed.

Human umbilical cord perivascular cells maintain regenerative traits following exposure to cyclophosphamide

Chemotherapies can cause germ cell depletion and gonadal failure. When injected post-chemotherapy, mesenchymal stromal cells (MSCs) from various sources have been shown to have regenerative effects in rodent models of chemotherapy-induced gonadal injury. Here, we evaluated two properties of a novel source of MSC, first trimester (FTM) human umbilical cord perivascular cells (HUCPVCs) (with increased regenerative potential compared to older sources), that may render them a promising candidate for chemotherapeutic gonadal injury prevention. Firstly, their ability to resist the cytotoxic effects of cyclophosphamide (CTX) in vitro, as compared to term HUCPVCs and bone marrow cells (BMSCs); and secondly, whether they prevent gonadal dysfunction if delivered prior to gonadotoxic therapy in vivo. BMSC, FTM HUCPVC, term HUCPVC, and control NTERA2 cells were treated with moderate (150 μmol/L) and high (300 μmol/L) doses of CTX in vitro. Viability, proliferative capacity, mesenchymal cell lineage markers and differentiation capacity, immunogenicity, and paracrine gene expression were assessed. CTX was administered to Wistar rats 2 days following an intra-ovarian injection of FTM HUCPVC. HUCPVC survival and ovarian follicle numbers were assessed using histological methods. We conclude that FTM HUCPVC maintain key regenerative properties following chemotherapy exposure and that pre-treatment with these cells may prevent CTX-induced ovarian damage in vivo. Therefore, HUCPVCs are promising candidates for fertility preservation.

3-D Cell Culture Systems in Bone Marrow Tissue and Organoid Engineering, and BM Phantoms as In Vitro Models of Hematological Cancer Therapeutics-A Review

We review the state-of-the-art in bone and marrow tissue engineering (BMTE) and hematological cancer tissue engineering (HCTE) in light of the recent interest in bone marrow environment and pathophysiology of hematological cancers. This review focuses on engineered BM tissue and organoids as in vitro models of hematological cancer therapeutics, along with identification of BM components and their integration as synthetically engineered BM mimetic scaffolds. In addition, the review details interaction dynamics of various BM and hematologic cancer (HC) cell types in co-culture systems of engineered BM tissues/phantoms as well as their relation to drug resistance and cytotoxicity. Interaction between hematological cancer cells and their niche, and the difference with respect to the healthy niche microenvironment narrated. Future perspectives of BMTE for in vitro disease models, BM regeneration and large scale ex vivo expansion of hematopoietic and mesenchymal stem cells for transplantation and therapy are explained. We conclude by overviewing the clinical application of biomaterials in BM and HC pathophysiology and its challenges and opportunities.

Extended in vitro culture of primary human mesenchymal stem cells downregulates Brca1-related genes and impairs DNA double-strand break recognition

Mesenchymal stem cells (MSCs) are multilineage adult stem cells with considerable potential for cell‐based regenerative therapies. In vitro expansion changes their epigenetic and cellular properties, with a poorly understood impact on DNA damage response (DDR) and genome stability. We report here results of a transcriptome‐based pathway analysis of in vitro‐expanded human bone marrow‐derived mesenchymal stem cell (hBM‐MSCs), supplemented with cellular assays focusing on DNA double‐strand break (DSB) repair. Gene pathways affected by in vitro aging were mapped using gene ontology, KEGG, and GSEA, and were found to involve DNA repair, homologous recombination (HR), cell cycle control, and chromosomal replication. Assays for the recognition (γ‐H2AX + 53BP1 foci) and repair (pBRCA1 + γ‐H2AX foci) of X‐ray‐induced DNA DSBs in hBM‐MSCs show that over a period of 8 weeks of in vitro aging (i.e., about 10 doubling times), cells exhibit a reduced DDR and a higher fraction of residual DNA damage. Furthermore, a distinct subpopulation of cells with impaired DNA DSB recognition was observed. Several genes that participate in DNA repair by HR (e.g., Rad51, Rad54, BRCA1) show a 2.3‐ to fourfold reduction of their mRNA expression by qRT‐PCR. We conclude that the in vitro expansion of hMSCs can lead to aging‐related impairment of the recognition and repair of DNA breaks.

Intraoperative radiotherapy for breast cancer treatment efficiently targets the tumor bed preventing breast adipose stromal cell outgrowth

OBJECTIVES

Mesenchymal stromal cells (MSC) in bone marrow have been shown to be radioresistant, which is related to pronounced DNA repair mechanisms. Intraoperative radiotherapy (IORT) during breast-conserving surgery for early breast cancer is an innovative technique applying low energy x‑ray to the tumor bed immediately after removal of the tumor. IORT is considered to reduce the risk of local tumor recurrence by directly targeting cells of the tumor bed and altering the local microenvironment. Aim of this study was to investigate whether IORT affects the outgrowth potential of breast adipose tissue-derived MSC (bASC) as part of the tumor bed.

MATERIALS AND METHODS

After surgical tumor resection, biopsies of the tumor bed were taken before (pre IORT) and after IORT (post IORT) and processed applying well-established protocols for ASC isolation and characterization.

RESULTS

In all, 95% of pre IORT tumor bed samples yielded persistently outgrowing bASC with typical ASC characteristics: fibroblastoid morphology, proliferation, adipogenic and osteogenic differentiation and ASC surface marker expression. However, none of the post IORT samples yielded persistent outgrowth of bASC.

CONCLUSIONS

After breast-conserving surgery, approximately 90% of local recurrences emerge in close proximity to the initial tumor bed, potentially reflecting a significant contribution of the tumor bed to relapse. Our data show that IORT, besides the proven effect on breast cancer cells, efficiently modifies the tumor environment by having an impact on tumor bed bASC. This effect on tumor bed stromal cells might contribute to reduce the risk of tumor relapse and metastases.

Enhancing the Bystander and Abscopal Effects to Improve Radiotherapy Outcomes

In this paper, we summarize published articles and experiences related to the attempt to improve radiotherapy outcomes and, thus, to personalize the radiation treatment according to the individual characteristics of each patient. The evolution of ideas and the study of successively published data have led us to envisage new biophysical models for the interpretation of tumor and healthy normal tissue response to radiation. In the development of the model, we have shown that when mesenchymal stem cells (MSCs) and radiotherapy are administered simultaneously in experimental radiotherapy on xenotumors implanted in a murine model, the results of the treatment show the existence of a synergic mechanism that is able to enhance the local and systemic actions of the radiation both on the treated tumor and on its possible metastasis. We are convinced that, due to the physical hallmarks that characterize the neoplastic tissues, the physical-chemical tropism of MSCs, and the widespread functions of macromolecules, proteins, and exosomes released from activated MSCs, the combination of radiotherapy plus MSCs used intratumorally has the effect of counteracting the pro-tumorigenic and pro-metastatic signals that contribute to the growth, spread, and resistance of the tumor cells. Therefore, we have concluded that MSCs are appropriate for therapeutic use in a clinical trial for rectal cancer combined with radiotherapy, which we are going to start in the near future.

Radiotherapy-induced heart disease: a review of the literature

Radiotherapy as one of the four pillars of cancer therapy plays a critical role in the multimodal treatment of thoracic cancers. Due to significant improvements in overall cancer survival, radiotherapy-induced heart disease (RIHD) has become an increasingly recognized adverse reaction which contributes to major radiation-associated toxicities including non-malignant death. This is especially relevant for patients suffering from diseases with excellent prognosis such as breast cancer or Hodgkin's lymphoma, since RIHD may occur decades after radiotherapy. Preclinical studies have enriched our knowledge of many potential mechanisms by which thoracic radiotherapy induces heart injury. Epidemiological findings in humans reveal that irradiation might increase the risk of cardiac disease at even lower doses than previously assumed. Recent preclinical studies have identified non-invasive methods for evaluation of RIHD. Furthermore, potential options preventing or at least attenuating RIHD have been developed. Ongoing research may enrich our limited knowledge about biological mechanisms of RIHD, identify non-invasive early detection biomarkers and investigate potential treatment options that might attenuate or prevent these unwanted side effects. Here, we present a comprehensive review about the published literature regarding clinical manifestation and pathological alterations in RIHD. Biological mechanisms and treatment options are outlined, and challenges in RIHD treatment are summarized.

GLUT-1 siRNA Enhances Radiosensitization Of Laryngeal Cancer Stem Cells Via Enhanced DNA Damage, Cell Cycle Redistribution, And Promotion Of Apoptosis In Vitro And In Vivo

Background

Radiotherapy does not show good efficacy against laryngeal cancer due to radioresistance. Cancer stem cells (CSCs) are considered among the causes of radioresistance. Inhibition of glucose transporter-1 (GLUT-1) using GLUT-1 small interfering RNA (siRNA) may enhance the radiosensitivity of laryngeal cancer cells, but the underlying cellular mechanisms remain unclear.

Methods

The CD133⁺-Hep-2R cell line was established with repeated irradiation and magnetic-activated cell sorting. The effects of irradiation on CD133⁺-Hep-2R cells were examined by CCK-8 assay, Transwell assay, quantitative real-time polymerase chain reaction (RT-PCR), and Western blotting. The effects of GLUT-1 siRNA on the radiosensitivity of CD133⁺-Hep-2/2R cells were examined by RT-PCR, Western blotting, CCK-8 assay, colony formation assay, and Transwell assay in vitro and in a xenograft tumor model in nude mice. The cellular mechanism of enhanced radiosensitivity associated with GLUT-1 siRNA was investigated. The cell cycle and apoptosis rate were analyzed by flow cytometry, and the repair capability was examined by determining the levels of RAD51 and DNA-PKcs.

Results

CD133⁺-Hep-2/2R cells showed stronger proliferation, lower apoptosis rate, lower percentage of G0/G1 phase cells, higher percentages of S and G2/M phase cells, and higher expression levels of GLUT-1 than Hep-2/2R cells. Transfection with GLUT-1 siRNA inhibited the proliferation and invasive capability of CD133⁺-Hep-2R cells by inhibiting GLUT-1 expression, which also caused a redistribution of the cell cycle (higher proportion of cells in the G0/G1 phase and lower proportion in the S and G2/M phases), increased the apoptosis rate, and reduced DNA repair capability by suppressing RAD51 and DNA-PKcs expression.

Conclusion

The results of this study suggest that GLUT-1 siRNA can enhance the radiosensitivity of CD133⁺-Hep-2R cells by inducing a redistribution of cell cycle phases, inhibiting DNA repair capability, and increasing apoptosis. Inhibition of GLUT-1 may have therapeutic potential for interventions to increase the radiosensitivity of laryngeal CSCs.

Adipose-derived mesenchymal stem cells regenerate radioiodine-induced salivary gland damage in a murine model

After radioiodine (RI) therapy, patients with thyroid cancer frequently suffer from painful salivary gland (SG) swelling, xerostomia, taste alterations, and oral infections. This study was aimed to determine whether adipose-derived mesenchymal stem cells (AdMSCs) might restore RI-induced SG dysfunction in a murine model. Forty -five mice were divided into three groups; a PBS sham group, a RI+ PBS sham group (0.01 mCi/g mouse, orally), and an RI+AdMSCs (1 × 10⁵ cells/150 uL, intraglandular injection on experimental day 28) treated group. At 16 weeks after RI treatment, body weights, SG weight, salivary flow rates (SFRs), and salivary lag times were measured. Morphologic and histologic examinations and immunohistochemistry (IHC) were performed and the activities of amylase and EGF in saliva were also measured. Changes in salivary ^99mTc pertechnetate excretion were followed by SPECT and TUNEL assays were performed. The body and SG weights were similar in the AdMSCs and sham groups. Hematoxylin and eosin staining revealed the AdMSCs group had more mucin-containing acini than the RI group. Furthermore, AdMSCs treatment resulted in tissue remodeling and elevated expressions of epithelial (AQP5) and endothelial (CD31) markers, and increased SFRs. The activities of amylase and EGF were higher in the AdMSCs group than in the RI treated group. ^99mTc pertechnetate excretions were similar in the AdMSCs and sham group. Also, TUNEL positive apoptotic cell numbers were less in the AdMSCs group than in the RI group. Local delivery of AdMSCs might regenerate SG damage induced by RI.

Resistance of human primary mesenchymal stem cells to cytotoxic effects of nutlin-3 in vitro

BACKGROUND

The small-molecule nutlin-3 was found to be an effective therapeutic compound and p53 activator, and acts as a murine double minute 2 antagonist, although these findings need to be clinically confirmed. The essential components of the bone marrow include mesenchymal stem cells (MSCs), which play a key role in protecting, regenerating, and proliferating hematopoietic stem cells (HSCs). This feature is vital for HSC after exposure to myelotoxic anticancer agents; nevertheless, the effects of nutlin-3 on MSCs remain to be disclosed. The present research study was conducted to examine the antiproliferative and proapoptotic effectiveness of nutlin-3 in bone marrow MSCs (BMSCs).

MATERIALS AND METHODS

Human-derived BMSCs were cultured for different durations, that is, 24, 48, and 72 hours, and treated using various concentrations of nutlin-3, including 5, 10, 25, 50, and 100 μΜ. To investigate the effect of nutlin-3 on the apoptosis, cell vitality and proliferation in BMSCs, the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), thiazolyl blue tetrazolium bromide, propidium iodide (PI) and annexin V assay, as well as real-time polymerase chain reaction, were used.

RESULTS

BMSCs viability significantly decreased (P < .05) in the cells treated at concentrations of 50 and 100 μM for 24 hours and concentrations of 25, 50, and 100 μM for 48 hours and at all concentrations for 72 hours. The apoptosis of BMSCs (TUNEL positive) was significantly more visible at concentrations of 25 and 50 μM compared with that in the controls (P < .05), while this increased through dose-dependent processes. Annexin V/PI staining revealed negligible dose-dependent increases in all the apoptotic cells after 72 hours of incubation, and this apoptosis elevation was significant at 25 and 50 μM (P < .05).

CONCLUSION

Resistance to nutlin-3 was observed in human bone marrow-derived MSCs; nevertheless, further clinical data are required to be obtained with long-duration exposure to confirm the present findings.

[Normal tissue: radiosensitivity, toxicity, consequences for planning]

Along with chemotherapy, surgery and immunotherapy, radiotherapy is a mainstay of cancer treatment. Considering the improving survival rates for various malignancies during the past decades, the importance of radiation-induced late normal tissue response is increasing. Quality of life is becoming an important issue in modern cancer treatment and is correlated with acute and late normal tissue response after radiotherapy. A profound understanding of radiation-induced normal tissue response is necessary to sufficiently diagnose and treat radiation-induced side effects and thereby increase the patients' quality of life. Here, the various normal tissue responses in consideration of the radiation biology are specified and prospective options to attenuate radiation-induced side effects are discussed.

The Role of Mesenchymal Stem Cells in Radiation-Induced Lung Fibrosis

Radiation therapy is one of the most important treatment modalities for thoracic tumors. Despite significant advances in radiation techniques, radiation-induced lung injury (RILI) still occurs in up to 30% of patients undergoing thoracic radiotherapy, and therefore remains the main dose-limiting obstacle. RILI is a potentially lethal clinical complication of radiotherapy that has 2 main stages: an acute stage defined as radiation pneumonitis, and a late stage defined as radiation-induced lung fibrosis. Patients who develop lung fibrosis have a reduced quality of life with progressive and irreversible organ malfunction. Currently, the most effective intervention for the treatment of lung fibrosis is lung transplantation, but the lack of available lungs and transplantation-related complications severely limits the success of this procedure. Over the last few decades, advances have been reported in the use of mesenchymal stem cells (MSCs) for lung tissue repair and regeneration. MSCs not only replace damaged lung epithelial cells but also promote tissue repair through the secretion of anti-inflammatory and anti-fibrotic factors. Here, we present an overview of MSC-based therapy for radiation-induced lung fibrosis, focusing in particular on the molecular mechanisms involved and describing the most recent preclinical and clinical studies carried out in the field.

Effects of ionizing irradiation and interface backscatter on human mesenchymal stem cells cultured on titanium surfaces

Radiotherapy to the head and neck region negatively influences the osseointegration and survival of dental implants. The effects of cobalt 60 (⁶⁰ Co) ionizing radiation and the impact of backscatter rays were investigated on human mesenchymal stem cells cultured on titanium surfaces. Bone marrow-derived human mesenchymal stem cells were seeded on titanium (Ti), fluoride-modified titanium (TiF), and tissue culture plastic. Cells were exposed to ionizing γ-radiation in single doses of 2, 6, or 10 Gy using a ⁶⁰ Co source. Density and distribution of cells were evaluated using confocal laser-scanning microscopy, 21 d post-irradiation. Lactate dehydrogenase concentration and the levels of total protein and cytokines/chemokines were measured in the cell-culture medium on days 1, 3, 7, 14, and 21 post-irradiation. Unirradiated cells were used as the control. Irradiation had no effect on cell viability, collagen and actin expression, or cell distribution, but induced an initial increase in the secretion of interleukin (IL)-6, IL-8, monocyte chemotactic protein 1 (MCP-1), and vascular endothelial growth factor (VEGF), followed by a decrease in secretion after 3 or 7 d. Irradiation resulted in secretion of a lower amount of all analytes examined compared with controls on day 21, irrespective of radiation dose and growth surface. Backscattering from titanium did not influence the cell response significantly, suggesting a clinical potential for achieving successful osseointegration of dental implants placed before radiotherapy.

Differential response of esophageal cancer cells to particle irradiation

Background

Radiation therapy is a mainstay in the treatment of esophageal cancer (EC) patients, and photon radiotherapy has proved beneficial both in the neoadjuvant and the definitive setting. However, regarding the still poor prognosis of many EC patients, particle radiation employing a higher biological effectiveness may help to further improve patient outcomes. However, the influence of clinically available particle radiation on EC cells remains largely unknown.

Methods

Patient-derived esophageal adenocarcinoma and squamous cell cancer lines were treated with photon and particle irradiation using clinically available proton (¹H), carbon (¹²C) or oxygen (¹⁶O) beams at the Heidelberg Ion Therapy Center. Histology-dependent clonogenic survival was calculated for increasing physical radiation doses, and resulting relative biological effectiveness (RBE) was calculated for each radiation modality. Cell cycle effects caused by photon and particle radiation were assessed, and radiation-induced apoptosis was measured in adenocarcinoma and squamous cell EC samples by activated caspase-3 and sub-G1 populations. Repair kinetics of DNA double strand breaks induced by photon and particle radiation were investigated.

Results

While both adenocarcinoma EC cell lines demonstrated increasing sensitivities for ¹H, ¹²C and ¹⁶O radiation, the two squamous cell carcinoma lines exhibited a more heterogeneous response to photon and particle treatment; average RBE values were calculated as 1.15 for ¹H, 2.3 for ¹²C and 2.5 for ¹⁶O irradiation. After particle irradiation, squamous cell EC samples reacted with an increased and prolonged block in G2 phase of the cell cycle compared to adenocarcinoma cells. Particle radiation resulted in an incomplete repair of radiation-induced DNA double strand breaks in both adenocarcinoma and squamous cell carcinoma samples, with the levels of initial strand break induction correlating well with the individual cellular survival after photon and particle radiation. Similarly, EC samples demonstrated heterogeneous levels of radiation-induced apoptosis that also corresponded to the observed cellular survival of individual cell lines.

Conclusions

Esophageal cancer cells exhibit differential responses to irradiation with photons and ¹H, ¹²C and ¹⁶O particles that were independent of tumor histology. Therefore, yet unknown molecular markers beyond histology may help to establish which esophageal cancer patients benefit from the biological effects of particle treatment.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1326-9) contains supplementary material, which is available to authorized users.

Mitochondrial adaptation in human mesenchymal stem cells following ionizing radiation

Mitochondria are highly dynamic organelles that respond rapidly to a number of stressors to regulate energy transduction, cell death signaling, and reactive oxygen species generation. We hypothesized that mitochondrial remodeling, comprising both structural and functional alterations, following ionizing radiation (IR) may underlie some of the tenets of radiobiology. Mesenchymal stem cells (MSCs) are precursors of bone marrow stroma and are altered in acute myeloid leukemia and by radiation and chemotherapy. Here, we report on changes in mitochondrial remodeling in human MSCs following X-ray IR. Mitochondrial function was significantly increased in MSCs  4 h after IR as measured by mitochondrial oxygen consumption. Consistent with this elevated functional effect, electron transport chain supercomplexes were also increased in irradiated samples. In addition, mitochondria were significantly, albeit modestly, elongated, as measured by high-throughput automated confocal imaging coupled with automated mitochondrial morphometric analyses. We also demonstrate in fibroblasts that mitochondrial remodeling is required for the adaptation of cells to IR. To determine novel mechanisms involved in mitochondrial remodeling, we performed quantitative proteomics on isolated mitochondria from cells following IR. Label-free quantitative mitochondrial proteomics revealed notable changes in proteins in irradiated samples and identified prosaposin, and potentially its daughter protein saposin-B, as a potential candidate for regulating mitochondrial function following IR. Whereas research into the biologic effects of cellular irradiation has long focused on nuclear DNA effects, our experimental work, along with that of others, is finding that mitochondrial effects may have broader implications in the field of stress adaptation and cell death in cancer (including leukemia) and other disease states.-Patten, D. A., Ouellet, M., Allan, D. S., Germain, M., Baird, S. D., Harper, M.-E., Richardson, R. B. Mitochondrial adaptation in human mesenchymal stem cells following ionizing radiation.

Radiation-induced sensitivity of tissue-resident mesenchymal stem cells in the head and neck region

BACKGROUND

Tissue-resident mesenchymal stem cells (MSCs) possess the ability to migrate to areas of inflammation and promote the regeneration of damaged tissue. However, it remains unclear how radiation influences this capacity of MSC in the head and neck region.

METHODS

Two types of MSCs of the head and neck region (mucosa [mMSC] and parotid gland [pMSC]) were isolated, cultured and exposed to single radiation dosages of 2 Gy/day up to 10 days. Effects on morphology, colony forming ability, apoptosis, chemokine receptor expression, cytokine secretion, and cell migration were analyzed.

RESULTS

Although MSC preserved MSC-specific regenerative abilities and immunomodulatory properties following irradiation in our in vitro model, we found a deleterious impact on colony forming ability, especially in pMSC.

CONCLUSIONS

MSC exhibited robustness and activation upon radiation for the support of tissue regeneration, but lost their potential to replicate, thus possibly leading to depletion of the local MSC-pool after irradiation.

Long noncoding RNA TUG1 inhibits osteogenesis of bone marrow mesenchymal stem cells via Smad5 after irradiation

Irradiation can greatly inhibit osteogenesis of bone marrow mesenchymal stem cells (BM-MSCs). However, the mechanism remains unclear.

Methods: We analyzed the expression profile of long noncoding RNAs (lncRNAs) in BM-MSCs using microarray data. LncRNA TUG1 (Taurine Upregulated Gene 1) was selected and tested in radiated BM-MSCs and non-radiated BM-MSCs. Functional analyses (in vitro) were performed to confirm the role of TUG1 in the osteogenic inhibition induced by irradiation. A RIP (RNA immunoprecipitation) assay was performed to detect the interaction of TUG1 and Smad5. Smad5 and the phosphorylated Smad5 (p-Smad5) were tested by western blot. The nuclear translocation of p-Smad5 were tested by immunofluorescence analysis. Furthermore, a series of Smad5 deletions was constructed to identify the TUG1 binding site of Smad5.

Results: We found that numerous lncRNAs, including TUG1, exhibit significant expression differences after irradiation. After irradiation TUG1 was significantly increased in BM-MSCs and inhibited osteogenesis. Furthermore, TUG1 directly bound to Smad5, an osteogenic enhancer. Although the phosphorylation level of Smad5 was increased following irradiation, osteogenesis of BM-MSCs was decreased. Mechanistically, TUG1 interacting with the 50-90 aa region of Smad5 and blocks the nuclear translocation of p-Smad5, abolishing osteogenic signalling after irradiation.

Conclusion: These results indicate that TUG1 is a negative regulator of Smad5 signalling and suppresses osteogenesis of BM-MSCs after irradiation.

Immune Modulation by Transplanted Calcium Phosphate Biomaterials and Human Mesenchymal Stromal Cells in Bone Regeneration

A wide variety of biomaterials have been developed as both stabilizing structures for the injured bone and inducers of bone neoformation. They differ in chemical composition, shape, porosity, and mechanical properties. The most extensively employed and studied subset of bioceramics are calcium phosphate materials (CaPs). These materials, when transplanted alongside mesenchymal stem cells (MSCs), lead to ectopic (intramuscular and subcutaneous) and orthotopic bone formation in preclinical studies, and effective fracture healing in clinical trials. Human MSC transplantation in pre-clinical and clinical trials reveals very low engraftment in spite of successful clinical outcomes and their therapeutic actions are thought to be primarily through paracrine mechanisms. The beneficial role of transplanted MSC could rely on their strong immunomodulatory effect since, even without long-term engraftment, they have the ability to alter both the innate and adaptive immune response which is critical to facilitate new bone formation. This study presents the current knowledge of the immune response to the implantation of CaP biomaterials alone or in combination with MSC. In particular the central role of monocyte-derived cells, both macrophages and osteoclasts, in MSC-CaP mediated bone formation is emphasized. Biomaterial properties, such as macroporosity and surface microstructure, dictate the host response, and the ultimate bone healing cascade. Understanding intercellular communications throughout the inflammation, its resolution and the bone regeneration phase, is crucial to improve the current therapeutic strategies or develop new approaches.

In vitro expansion affects the response of human bone marrow stromal cells to irradiation

BACKGROUND

Bone marrow stromal cells (BMSCs) are extensively used in regeneration therapy and cytology experiments simulate how BMSCs respond to radiation. Due to the small number and the heterogeneity of primary isolated BMSCs, extensive in vitro expansion is usually required before application, which affects the cellular characteristics and gene expression of BMSCs. However, whether the radiation response of BMSCs changes during in vitro expansion is unclear.

METHODS

In this study, BMSCs were passaged in vitro and irradiated at passage 6 (P6) and passage 10 (P10). Then, apoptosis, the cell cycle, senescence, the cytokine secretion and the gene expression profile were analysed for the P6, P10, and non-irradiated (control) BMSCs at different post-irradiation time points.

RESULTS

The P6 BMSCs had a lower percentage of apoptotic cells than the P10 BMSCs at 24 and 48 h post-irradiation but not compared to that of the controls at 2 and 8 h post-irradiation. The P6 BMSCs had a lower percentage of cells in S phase and a higher percentage in G1 phase than the P10 BMSCs at 2 and 8 h post-irradiation. The radiation had similar effects on the senescent cell level and impaired immunomodulation capacity of the P6 and P10 BMSCs. Regardless of whether they were irradiated, the P6 and P10 BMSCs always expressed a distinctive set of genes. The upregulated genes were enriched in pathways including the cell cycle, DNA replication and oocyte meiosis. Then, a subset of conserved irradiation response genes across the BMSCs was identified, comprising 12 differentially upregulated genes and 5 differentially downregulated genes. These genes were especially associated with the p53 signaling pathway, DNA damage and DNA repair. Furthermore, validation experiments revealed that the mRNA and protein levels of these conserved genes were different between the P6 and P10 BMSCs after irradiation. Weighted gene co-expression network analysis supported these findings and further revealed the effects of cell passage on the irradiation response in BMSCs.

CONCLUSION

The results indicated that cell passage in vitro affected the irradiation response of BMSCs via molecular mechanisms that mediated differences in apoptosis, the cell cycle, senescence and the cytokine secretion. Thus, accurate cell passage information is not only important for transplantation therapy but also for future studies on the radiation response in BMSCs.

Clinically Relevant Solution for the Hypothermic Storage and Transportation of Human Multipotent Mesenchymal Stromal Cells

The wide use of human multipotent mesenchymal stromal cells (MSCs) in clinical trials requires a full-scale safety and identity evaluation of the cellular product and subsequent transportation between research/medical centres. This necessitates the prolonged hypothermic storage of cells prior to application. The development of new, nontoxic, and efficient media, providing high viability and well-preserved therapeutic properties of MSCs during hypothermic storage, is highly relevant for a successful clinical outcome. In this study, a simple and effective trehalose-based solution was developed for the hypothermic storage of human bone marrow MSC suspensions for further clinical applications. Human bone marrow MSCs were stored at 4°C for 24, 48, and 72 hrs in the developed buffered trehalose solution and compared to several research and clinical grade media: Plasma-Lyte® 148, HypoThermosol® FRS, and Ringer's solution. After the storage, the preservation of viability, identity, and therapeutically associated properties of MSCs were assessed. The hypothermic storage of MSCs in the new buffered trehalose solution provided significantly higher MSC recovery rates and ability of cells for attachment and further proliferation, compared to Plasma-Lyte® 148 and Ringer's solution, and was comparable to research-grade HypoThermosol® FRS. There were no differences in the immunophenotype, osteogenic, and adipogenic differentiation and the immunomodulatory properties of MSCs after 72 hrs of cold storage in these solutions. The obtained results together with the confirmed therapeutic properties of trehalose previously described provide sufficient evidence that the developed trehalose medium can be applied as a low-cost and efficient solution for the hypothermic storage of MSC suspensions, with a high potential for translation into clinical practice.

Therapeutic Irradiation: Consequences for Bone and Bone Marrow Adipose Tissue

Radiotherapy continues to be one of the most accepted medical treatments for cancer. Localized irradiation is the most common treatment for prostate, pancreatic, rectal, cervical and endometrial malignancies. Conventional localized fractions are total doses of 30-62Gy at 1.8-2Gy per fraction, with administration of ~60Gy often used for tumor ablation. However, even the lowest dose of localized irradiation exposure can result in adverse complications to adjacent organs, tissues, and vessels, which absorb a portion of the treatment. Skeletal complications are common amongst cancer patients undergoing these localized treatments. Irradiation exposure causes deterioration to the overall quantity and quality of bone by interfering with the trabecular architecture through increased osteoclast activity and decreased osteoblast activity. Irradiation-induced bone damage parallels adipocyte infiltration of the bone marrow (BM) resulting in compositional alterations of the microenvironment that may further affect bone quality and disease state. There may also be direct effects of irradiation on the BM adipocyte/pre-adipocyte, although in vitro findings do not always agree and cellular response is dependent on irradiation dosage. Hematopoietic cells also become apoptotic upon irradiation, which causes a range of skeletal effects. Bone loss leaves patients at a greater risk for osteopenia, osteoporosis, osteonecrosis, and skeletal fractures that drastically reduce quality of life. Osteoanabolic agents stimulate bone formation and reduce fracture risk in patients with low bone density; thus, osteoanabolic or anti-resorptive agents may be useful co-treatments with irradiation. This review discusses these topics and proposes further research directions using novel or combination therapies to enhance bone health during irradiation.

Therapeutic ionizing radiation induced bone loss: a review of in vivo and in vitro findings

Radiation therapy is one of the routine treatment modalities for cancer patients. Ionizing radiation (IR) can induce bone loss, and consequently increases the risk of fractures with delayed and nonunion of the bone in the cancer patients who receive radiotherapy. The orchestrated bone remodeling can be disrupted due to the affected behaviors of bone cells, including bone mesenchymal stem cells (BMSCs), osteoblasts and osteoclasts. BMSCs and osteoblasts are relatively radioresistant compared with osteoclasts and its progenitors. Owing to different radiosensitivities of bone cells, unbalanced bone remodeling caused by IR is closely associated with the dose absorbed. For doses less than 2 Gy, osteoclastogenesis and adipogenesis by BMSCs are enhanced, while there are limited effects on osteoblasts. High doses (>10 Gy) induce disrupted architecture of bone, which is usually related to decreased osteogenic potential. In this review, studies elucidating the biological effects of IR on bone cells (BMSCs, osteoblasts and osteoclasts) are summarized. Several potential preventions and therapies are also proposed.

Impact of X-ray Exposure on the Proliferation and Differentiation of Human Pre-Adipocytes

Radiotherapy is a widely used treatment option for cancer patients as well as for patients with musculoskeletal disorders. Adipocytes, the dominant cell type of adipose tissue, are known to constitute an active part of the tumor microenvironment. Moreover, adipocytes support inflammatory processes and cartilage degradation in chronic inflammatory diseases, i.e., rheumatoid and osteoarthritis. Since the production of inflammatory factors is linked to their differentiation stages, we set out to explore the radiation response of pre-adipocytes that may influence their inflammatory potential and differentiation capacity. This is the first study investigating the effects of X-ray irradiation on the proliferation and differentiation capacity of human primary pre-adipocytes, in comparison to Simpson–Golabi–Behmel Syndrome (SGBS) pre-adipocytes, an often-used in vitro model of human primary pre-adipocytes. Our results demonstrate a dose-dependent reduction of the proliferation capacity for both cell strains, whereas the potential for differentiation was mostly unaffected by irradiation. The expression of markers of adipogenic development, such as transcription factors (PPARγ, C/EBPα and C/EBPβ), as well as the release of adipokines (visfatin, adiponectin and leptin) were not significantly changed upon irradiation. However, after irradiation with high X-ray doses, an increased lipid accumulation was observed, which suggests a radiation-induced response of adipocytes related to inflammation. Our results indicate that pre-adipocytes are radio-resistant, and it remains to be elucidated whether this holds true for the overall inflammatory response of adipocytes upon irradiation.

Radiation Induces Apoptosis and Osteogenic Impairment through miR-22-Mediated Intracellular Oxidative Stress in Bone Marrow Mesenchymal Stem Cells

Bone marrow mesenchymal stem cells (BMSCs) were characterized by their multilineage potential and were involved in both bony and soft tissue repair. Exposure of cells to ionizing radiation (IR) triggers numerous biological reactions, including reactive oxygen species (ROS), cellular apoptosis, and impaired differentiation capacity, while the mechanisms of IR-induced BMSC apoptosis and osteogenic impairment are still unclear. Through a recent study, we found that 6 Gy IR significantly increased the apoptotic ratio and ROS generation, characterized by ROS staining and mean fluorescent intensity. Intervention with antioxidant (NAC) indicated that IR-induced cellular apoptosis was partly due to the accumulation of intracellular ROS. Furthermore, we found that the upregulation of miR-22 in rBMSCs following 6 Gy IR played an important role on the ROS generation and subsequent apoptosis. In addition, we firstly demonstrated that miR-22-mediated ROS accumulation and cell injury had an important regulated role on the osteogenic capacity of BMSCs both in vitro and in vivo. In conclusion, IR-induced overexpression of miR-22 regulated the cell viability and differentiation potential through targeting the intracellular ROS.

The current understanding of mesenchymal stem cells as potential attenuators of chemotherapy-induced toxicity

Chemotherapeutic agents are part of the standard treatment algorithms for many malignancies; however, their application and dosage are limited by their toxic effects to normal tissues. Chemotherapy-induced toxicities can be long-lasting and may be incompletely reversible; therefore, causative therapies for chemotherapy-dependent side effects are needed, especially considering the increasing survival rates of treated cancer patients. Mesenchymal stem cells (MSCs) have been shown to exhibit regenerative abilities for various forms of tissue damage. Preclinical data suggest that MSCs may also help to alleviate tissue lesions caused by chemotherapeutic agents, mainly by establishing a protective microenvironment for functional cells. Due to the systemic administration of most anticancer agents, the effects of these drugs on the MSCs themselves are of crucial importance to use stem cell-based approaches for the treatment of chemotherapy-induced tissue toxicities. Here, we present a concise review of the published data regarding the influence of various classes of chemotherapeutic agents on the survival, stem cell characteristics and physiological functions of MSCs. Molecular mechanisms underlying the effects are outlined, and resulting challenges of MSC-based treatments for chemotherapy-induced tissue injuries are discussed.

The Differentiation Balance of Bone Marrow Mesenchymal Stem Cells Is Crucial to Hematopoiesis

Bone marrow mesenchymal stem cells (BMSCs), the important component and regulator of bone marrow microenvironment, give rise to hematopoietic-supporting stromal cells and form hematopoietic niches for hematopoietic stem cells (HSCs). However, how BMSC differentiation affects hematopoiesis is poorly understood. In this review, we focus on the role of BMSC differentiation in hematopoiesis. We discussed the role of BMSCs and their progeny in hematopoiesis. We also examine the mechanisms that cause differentiation bias of BMSCs in stress conditions including aging, irradiation, and chemotherapy. Moreover, the differentiation balance of BMSCs is crucial to hematopoiesis. We highlight the negative effects of differentiation bias of BMSCs on hematopoietic recovery after bone marrow transplantation. Keeping the differentiation balance of BMSCs is critical for hematopoietic recovery. This review summarises current understanding about how BMSC differentiation affects hematopoiesis and its potential application in improving hematopoietic recovery after bone marrow transplantation.

Bone marrow-derived mesenchymal stromal cells promote colorectal cancer cell death under low-dose irradiation

BACKGROUND

Radiotherapy remains one of the cornerstones to improve the outcome of colorectal cancer (CRC) patients. Radiotherapy of the CRC not only help to destroy cancer cells but also remodel the tumour microenvironment by enhancing tumour-specific tropism of bone marrow-derived mesenchymal stromal cell (BM-MSC) from the peripheral circulation. However, the role of local MSCs and recruited BM-MSC under radiation were not well defined. Indeed, the functions of BM-MSC without irradiation intervention remained controversial in tumour progression: BM-MSC was previously shown to modulate the immune function of major immune cells, resulting in an impaired immunological sensitivity and to induce an increased risk of tumour recurrence. In contrast, it could also secrete various cytokines and possess anticancer effect.

METHODS

Three co-cultivation modules, 3D culture modules, and cancer organoids were established. The induction of cytokines secretion in hBM-MSCs after irradiation was analysed by ELISA array and flow cytometry. AutoMac separator was used to separate hBM-MSC and CRC automatically. Cells from the co-cultured group and the control group were then irradiated by UV-C lamp and X-ray. Proliferation assay and viability assay were performed.

RESULTS

In this study, we show that BM-MSCs can induce the EMT progression of CRC cells in vitro. When irradiated with low doses of ultraviolet radiation and X-rays, BM-MSCs show an anti-tumour effect by secreting certain cytokine (TNF-α, IFN-γ) that lead to the inhibition of proliferation and induction of apoptosis of CRC cells. This was further verified in a 3D culture model of a CRC cell in vitro. Furthermore, irradiation on the co-culture system induced the cleavage of caspase3, and attenuated the phosphorylation of phosphatidylinositol 3-kinase (PI3K)/AKT and extracellular signal-regulated kinase in cancer cells. The signal pathways above might contribute to the cancer cell death.

CONCLUSIONS

Taken together, we show that BM-MSC can potentially promote the effect of radiotherapy in CRC.

Human mesenchymal stem cells lose their functional properties after paclitaxel treatment

Mesenchymal stem cells (MSCs) are an integral part of the bone marrow niche and aid in the protection, regeneration and proliferation of hematopoietic stem cells after exposure to myelotoxic taxane anti-cancer agents, but the influence of taxane compounds on MSCs themselves remains incompletely understood. Here, we show that bone marrow-derived MSCs are highly sensitive even to low concentrations of the prototypical taxane compound paclitaxel. While MSCs remained metabolically viable, they were strongly impaired regarding both their proliferation and their functional capabilities after exposure to paclitaxel. Paclitaxel treatment resulted in reduced cell migration, delays in cellular adhesion and significant dose-dependent inhibition of the stem cells’ characteristic multi-lineage differentiation potential. Cellular morphology and expression of the defining surface markers remained largely unaltered. Paclitaxel only marginally increased apoptosis in MSCs, but strongly induced premature senescence in these stem cells, thereby explaining the preservation of the metabolic activity of functionally inactivated MSCs. The reported sensitivity of MSC function to paclitaxel treatment may help to explain the severe bone marrow toxicities commonly caused by taxane-based anti-cancer treatments.

The Radiation Resistance of Human Multipotent Mesenchymal Stromal Cells Is Independent of Their Tissue of Origin

PURPOSE

Human mesenchymal stromal cells (MSCs) may aid the regeneration of ionizing radiation (IR)-induced tissue damage. They can be harvested from different tissues for clinical purposes; however, the role of the tissue source on the radiation response of human MSCs remains unknown.

METHODS AND MATERIALS

Human MSCs were isolated from adipose tissue, bone marrow, and umbilical cord, and cellular survival, proliferation, and apoptosis were measured after irradiation. The influence of IR on the defining functions of MSCs was assessed, and cell morphology, surface marker expression, and the differentiation potential were examined. Western blot analyses were performed to assess the activation of DNA damage signaling and repair pathways.

RESULTS

MSCs from adipose tissue, bone marrow, and umbilical cord exhibited a relative radioresistance independent of their tissue of origin. Defining properties including cellular adhesion and surface marker expression were preserved, and irradiated MSCs maintained their potential for multilineage differentiation irrespective of their tissue source. Analysis of activated DNA damage recognition and repair pathways demonstrated an efficient repair of IR-induced DNA double-strand breaks in MSCs from different tissues, thereby influencing the induction of apoptosis.

CONCLUSIONS

These data show for the first time that MSCs are resistant to IR and largely preserve their defining functions after irradiation irrespective of their tissue of origin. Efficient repair of IR-induced DNA double-strand breaks and consecutive reduction of apoptosis induction may contribute to the tissue-independent radiation resistance of MSCs.

Mesenchymal Stem Cells Secretory Responses: Senescence Messaging Secretome and Immunomodulation Perspective

Mesenchymal stem/stromal cells (MSC) have been tested in a significant number of clinical trials, where they exhibit regenerative and repair properties directly through their differentiation into the cells of the mesenchymal origin or by modulation of the tissue/organ microenvironment. Despite various clinical effects upon transplantation, the functional properties of these cells in natural settings and their role in tissue regeneration in vivo is not yet fully understood. The omnipresence of MSC throughout vascularized organs equates to a reservoir of potentially therapeutic regenerative depots throughout the body. However, these reservoirs could be subjected to cellular senescence. In this review, we will discuss current progress and challenges in the understanding of different biological pathways leading to senescence. We set out to highlight the seemingly paradoxical property of cellular senescence: its beneficial role in the development and tissue repair and detrimental impact of this process on tissue homeostasis in aging and disease. Taking into account the lessons from the different cell systems, this review elucidates how autocrine and paracrine properties of senescent MSC might impose an additional layer of complexity on the regulation of the immune system in development and disease. New findings that have emerged in the last few years could shed light on sometimes seemingly controversial results obtained from MSC therapeutic applications.