Tert-expressing cells contribute to salivary gland homeostasis and tissue regeneration after radiation therapy.

Salivary gland homeostasis and regeneration after radiotherapy depend significantly on progenitor cells. However, the lineage of submandibular gland (SMG) progenitor cells remains less defined compared with other normal organs. Here, using a mouse strain expressing regulated CreERT2 recombinase from the endogenous Tert locus, we identify a distinct telomerase-expressing (TertHigh) cell population located in the ductal region of the adult SMG. These TertHigh cells contribute to ductal cell generation during SMG homeostasis and to both ductal and acinar cell renewal 1 year after radiotherapy. TertHigh cells maintain self-renewal capacity during in vitro culture, exhibit resistance to radiation damage, and demonstrate enhanced proliferative activity after radiation exposure. Similarly, primary human SMG cells with high Tert expression display enhanced cell survival after radiotherapy, and CRISPR-activated Tert in human SMG spheres increases proliferation after radiation. RNA sequencing reveals upregulation of "cell cycling" and "oxidative stress response" pathways in TertHigh cells following radiation. Mechanistically, Tert appears to modulate cell survival through ROS levels in SMG spheres following radiation damage. Our findings highlight the significance of TertHigh cells in salivary gland biology, providing insights into their response to radiotherapy and into their use as a potential target for enhancing salivary gland regeneration after radiotherapy.

LPA5-Dependent signaling regulates regeneration of the intestinal epithelium following irradiation.

Lysophosphatidic acid (LPA) is a bioactive lipid molecule that regulates a wide array of cellular functions, including proliferation, differentiation, and survival, via activation of cognate receptors. The LPA5 receptor is highly expressed in the intestinal epithelium, but its function in restoring intestinal epithelial integrity following injury has not been examined. Here, we use a radiation-induced injury model to study the role of LPA5 in regulating intestinal epithelial regeneration. Control mice (Lpar5f/f) and mice with an inducible, epithelial cell-specific deletion of Lpar5 in the small intestine (Lpar5IECKO) were subjected to 10 Gy total body X-ray irradiation and analyzed during recovery. Repair of the intestinal mucosa was delayed in Lpar5IECKO mice with reduced epithelial proliferation and increased crypt cell apoptosis. These effects were accompanied by reduced numbers of OLFM4+ intestinal stem cells (ISCs). The effects of LPA5 on ISCs were corroborated by studies using organoids derived from Lgr5-lineage tracking reporter mice with deletion of Lpar5 in Lgr5+-stem cells (Lgr5Cont or Lgr5ΔLpar5). Irradiation of organoids resulted in fewer numbers of Lgr5ΔLpar5 organoids retaining Lgr5+-derived progenitor cells compared with Lgr5Cont organoids. Finally, we observed that impaired regeneration in Lpar5IECKO mice was associated with reduced numbers of Paneth cells and decreased expression of Yes-associated protein (YAP), a critical factor for intestinal epithelial repair. Our study highlights a novel role for LPA5 in regeneration of the intestinal epithelium following irradiation and its effect on the maintenance of Paneth cells that support the stem cell niche.NEW & NOTEWORTHY We used mice lacking expression of the lysophosphatidic acid receptor 5 (LPA5) in intestinal epithelial cells and intestinal organoids to show that the LPA5 receptor protects intestinal stem cells and progenitors from radiation-induced injury. We show that LPA5 induces YAP signaling and regulates Paneth cells.

Genotoxic stress abrogates renewal of melanocyte stem cells by triggering their differentiation.

Somatic stem cell depletion due to the accumulation of DNA damage has been implicated in the appearance of aging-related phenotypes. Hair graying, a typical sign of aging in mammals, is caused by the incomplete maintenance of melanocyte stem cells (MSCs) with age. Here, we report that irreparable DNA damage, as caused by ionizing radiation, abrogates renewal of MSCs in mice. Surprisingly, the DNA-damage response triggers MSC differentiation into mature melanocytes in the niche, rather than inducing their apoptosis or senescence. The resulting MSC depletion leads to irreversible hair graying. Furthermore, deficiency of Ataxia-telangiectasia mutated (ATM), a central transducer kinase of the DNA-damage response, sensitizes MSCs to ectopic differentiation, demonstrating that the kinase protects MSCs from their premature differentiation by functioning as a "stemness checkpoint" to maintain the stem cell quality and quantity.

Low-level laser activates Wnt/ß-catenin signaling pathway-promoting hair follicle stem cell regeneration and wound healing: Upregulate the expression of key downstream gene Lef 1.

BACKGROUND: The objective of this study is to investigate the mechanism by which low-level laser stimulation promotes the proliferation of intraepithelial hair follicle stem cells (HFSCs) in wounds. This research aims to expand the applications of laser treatment, enhance wound repair methods, and establish a theoretical and experimental foundation for achieving accelerated wound healing. METHODS: The experimental approach involved irradiating a cell model with low-level laser to assess the proliferation of HFSCs and examine alterations in the expression of proteins related to the Wnt/ß-catenin signaling pathway. A mouse back wound model was established to investigate the effects of low-level laser irradiation on wound healing rate, wound microenvironment, and the proliferation of HFSCs in relation to the Wnt/ß-catenin signaling pathway. RESULTS: The research findings indicate that low-level laser light effectively activates the Wnt signaling pathway, leading to the increased accumulation of core protein ß-catenin and the upregulation of key downstream gene Lef 1. Consequently, this regulatory mechanism facilitates various downstream biological effects, including the notable promotion of HFSC proliferation and differentiation into skin appendages and epithelial tissues. As a result, the process of wound healing is significantly accelerated. CONCLUSION: Low levels of laser activates the Wnt signalling pathway, promotes the regeneration of hair follicle stem cells and accelerates wound healing.

Carbon Dioxide Fractional Laser Treatment Induces Lgr5+ Stem Cell Activation and Hair Regrowth Through the Canonical Wnt/ß-Catenin Pathway.

BACKGROUND: Different types of alopecia have negative impacts on patients. Recently, some kinds of laser or light therapies have been reported to effectively alleviate hair loss. Carbon dioxide fractional laser (CO2FL) treatment is one of the most effective laser treatments, but its beneficial effects and exact mechanism in hair regrowth have not been reported in detail. The purpose of this study was to investigate the effect and molecular mechanism further. METHODS: C57 and Lgr5-Cre: Rosa-mTmG mouse models of hair regrowth were established by CO2FL treatment, and the parameters that induced the best effect were determined. Tissues were harvested on the day prior to the treatment day and on days 3, 5, 7, 10 and 14 after CO2FL. H&E and immunofluorescence staining, RNA sequencing (RNA-seq), quantitative real-time polymerase chain reaction (qPCR), Western blotting (WB) and related inhibitor were used to determine the molecular mechanism underlying the effect of CO2FL treatment on the hair cycle and hair regrowth. In clinical trial, five participants were treated three sessions at 1-month intervals to obverse the effects. RESULTS: Hair regrew and covered the treatment area on the tenth day after CO2FL treatment with the best parameters, while the control group showed signs of hair growth on the 14th day. H&E and immunofluorescence staining showed that the transition of hair follicles (HFs) from telogen to anagen was accelerated, and the rapid activation and proliferation of Lgr5+ hair follicle stem cells (HFSCs) were observed in the treatment group. The RNA-seq, qPCR and WB results indicated that the Wnt pathway was significantly activated after CO2FL treatment. Improvement achieved with CO2FL treatment in clinical trial. CONCLUSIONS: The results of this study suggest that CO2FL treatment can promote hair regrowth by activating Lgr5+ HFSCs and upregulating the Wnt/ß-catenin pathway. Clinical trial results demonstrated that CO2FL treatment will be a promising therapeutic regimen for alopecia. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Innate immune receptor NOD2 mediates LGR5+ intestinal stem cell protection against ROS cytotoxicity via mitophagy stimulation.

The nucleotide-binding oligomerization domain-containing protein 2 (NOD2) agonist muramyl dipeptide (MDP), a peptidoglycan motif common to all bacteria, supports leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5)+ intestinal stem cell (ISC) survival through NOD2 activation upon an otherwise lethal oxidative stress-mediated signal. However, the underlying protective mechanisms remain unknown. Here, using irradiation as stressor and primarily murine-derived intestinal organoids as a model system, we show that MDP induced a significant reduction of total and mitochondrial reactive oxygen species (ROS) within ISCs, which was associated with mitophagy induction. ATG16L1 knockout (KO) and NOD2 KO organoids did not benefit from the MDP-induced cytoprotection. We confirmed the MDP-dependent induction of ISC mitophagy upon stress in vivo. These findings elucidate the NOD2-mediated mechanism of cytoprotection involving the clearance of the lethal excess of ROS molecules through mitophagy, triggered by the coordinated activation of NOD2 and ATG16L1 by a nuclear factor κB (NF-κB)-independent pathway.

Sirolimus augments hematopoietic stem and progenitor cell regeneration following hematopoietic insults.

The role of mammalian target of rapamycin and its suppressor sirolimus in the regulation of hematopoietic stem and progenitor cells (HSPCs) is controversial. We show here that sirolimus enhanced regeneration of HSPCs in mice exposed to sublethal total body irradiation (TBI) and other regenerative stressors. Sorted Lin- CD150+ bone marrow cells from sirolimus-treated TBI mice had increased expression of c-Kit and other hematopoietic genes. HSPCs from sirolimus-treated TBI mice were functionally competent when tested by competitive engraftment in vivo. Postradiation regeneration of HSPCs in mice treated with sirolimus was accompanied by decreased γ-H2AX levels detected by flow cytometry and increased expression of DNA repair genes by quantitative polymerase chain reaction. Reduction of cell death and DNA damage post-radiation by sirolimus was associated with enhanced clearance of cellular reactive oxygen species (ROS) in HSPCs. Increased HSPC recovery with sirolimus was also observed in mice injected with hematoxic agents, busulfan and 5-fluorouracil. In contrast, sirolimus showed no effect on HSPCs in normal mice at steady state, but stimulated HSPC expansion in mice carrying the Wv mutation at the c-Kit locus. In human to mouse xenotransplantation, sirolimus enhanced engraftment of irradiated human CD34+ cells. In summary, our results are consistent with sirolimus' acceleration of HSPC recovery in response to hematopoietic stress, associated with reduced DNA damage and ROS. Sirolimus might have clinical application for the treatment and prevention of hematopoietic injury.

NIR irradiation of human buccal fat pad adipose stem cells and its effect on TRP ion channels.

The effect of near infrared (NIR) laser irradiation on proliferation and osteogenic differentiation of buccal fat pad-derived stem cells and the role of transient receptor potential (TRP) channels was investigated in the current research. After stem cell isolation, a 940 nm laser with 0.1 W, 3 J/cm2 was used in pulsed and continuous mode for irradiation in 3 sessions once every 48 h. The cells were cultured in the following groups: non-osteogenic differentiation medium/primary medium (PM) and osteogenic medium (OM) groups with laser-irradiated (L +), without irradiation (L -), laser treated + Capsazepine inhibitor (L + Cap), and laser treated + Skf96365 inhibitor (L + Skf). Alizarin Red staining and RT-PCR were used to assess osteogenic differentiation and evaluate RUNX2, Osterix, and ALP gene expression levels. The pulsed setting showed the best viability results (P < 0.05) and was used for osteogenic differentiation evaluations. The results of Alizarin red staining were not statistically different between the four groups. Osterix and ALP expression increased in the (L +) group. This upregulation abrogated in the presence of Capsazepine, TRPV1 inhibitor (L + Cap); however, no significant effect was observed with Skf96365 (L + Skf).

Dental pulp stem cell-derived small extracellular vesicle in irradiation-induced senescence.

Small extracellular vesicles (sEV) facilitate signaling molecule transfer among cells. We examined the therapeutic efficacy of human dental pulp stem cell-derived sEV (hDPSC-sEV) against cellular senescence in an irradiated-submandibular gland mouse model. Seven-week-old mice were exposed to 25 Gy radiation and randomly assigned to control, phosphate-buffered saline (PBS), or hDPSC-sEV groups. At 18 days post-irradiation, saliva production was measured; histological and reverse transcription-quantitative PCR analyses of the submandibular glands were performed. The salivary flow rate did not differ significantly between the PBS and hDPSC-sEV groups. AQP5-expressing acinar cell numbers and AQP5 expression levels in the submandibular glands were higher in the hDPSC-sEV group than in the other groups. Furthermore, compared with non-irradiated mice, mice in the 25 Gy + PBS group showed a high senescence-associated-ß-galactosidase-positive cell number and upregulated senescence-related gene (p16INK4a, p19Arf, p21) and senescence-associated secretory phenotypic factor (MMP3, IL-6, PAI-1, NF-κB, and TGF-ß) expression, all of which were downregulated in the hDPSC-sEV group. Superoxide dismutase levels were lower in the PBS group than in the hDPSC-sEV group. In summary, hDPSC-sEV reduced inflammatory cytokine and senescence-related gene expression and reversed oxidative stress in submandibular cells, thereby preventing irradiation-induced cellular senescence. Based on these results, we hope to contribute to the development of innovative treatment methods for salivary gland dysfunction that develops after radiotherapy for head and neck cancer.

Exosomes from adipose-derived stem cells attenuate UVB-induced apoptosis, ROS, and the Ca2+ level in HLEC cells.

Cartilage acid protein 1 (CRTAC1) encodes a protein containing the Ca2+binding domain, which can promote apoptosis of human lens epithelial cells (HLECs) induced by ultraviolet B radiation. Exosomes secreted from adipose-derived stem cells (ASC-exo) have been used to treat many diseases, but the effect of ASC-exo on cataracts has not been established. We hypothesized that ASC-exo has a therapeutic effect on cataracts by regulating CRTAC1. We established the UVB-induced injured HLECs model to test the interactions between CRTAC1 and miR-10a-5p, and the effect on the Ca2+ level and reactive oxygen species (ROS) generation in apoptotic HLECs. We found that UVB significantly increased the level of CRTAC1 expression and induced HLEC apoptosis, while ASC-exo inhibited the induction of UVB and exosome inhibitor reduced the inhibition of ASC-exo. The qRT-PCR results showed that miR-10a-5p had a low level of expression in cataract lesions, whereas CRTAC1 was highly expressed. There was a negative correlation between the expression of CRTAC1 and miR-10a-5p. ASC-exo reversed UVB-inhibited miR-10a-5p expression and miR-10a-5p negatively regulated CRTAC1. In vitro data showed that miR-10a-5p reversed UVB-induced ROS, apoptosis, and the Ca2+ level in HLECs. Overexpression of CRTAC1 reversed the induction of ASC-exo in UVB-injured HLECs, and low expression of CRTAC1 reversed the induction of miR-10a-5p inhibitor. By upregulating the level of miR-10a-5p expression and downregulating the level of CRTAC1 expression, exosomes from ASCs attenuated UVB-induced apoptosis, ROS generation, and the Ca2+ level in HLECs. Our research provides novel insight into the treatment methods and associated mechanisms underlying cataracts.

Yap-dependent reprogramming of Lgr5(+) stem cells drives intestinal regeneration and cancer.

The gut epithelium has remarkable self-renewal capacity that under homeostatic conditions is driven by Wnt signalling in Lgr5(+) intestinal stem cells (ISCs). However, the mechanisms underlying ISC regeneration after injury remain poorly understood. The Hippo signalling pathway mediates tissue growth and is important for regeneration. Here we demonstrate in mice that Yap, a downstream transcriptional effector of Hippo, is critical for recovery of intestinal epithelium after exposure to ionizing radiation. Yap transiently reprograms Lgr5(+) ISCs by suppressing Wnt signalling and excessive Paneth cell differentiation, while promoting cell survival and inducing a regenerative program that includes Egf pathway activation. Accordingly, growth of Yap-deficient organoids is rescued by the Egfr ligand epiregulin, and we find that non-cell-autonomous production of stromal epiregulin may compensate for Yap loss in vivo. Consistent with key roles for regenerative signalling in tumorigenesis, we further demonstrate that Yap inactivation abolishes adenomas in the Apc(Min) mouse model of colon cancer, and that Yap-driven expansion of Apc(-/-) organoids requires the Egfr module of the Yap regenerative program. Finally, we show that in vivo Yap is required for progression of early Apc mutant tumour-initiating cells, suppresses their differentiation into Paneth cells, and induces a regenerative program and Egfr signalling. Our studies reveal that upon tissue injury, Yap reprograms Lgr5(+) ISCs by inhibiting the Wnt homeostatic program, while inducing a regenerative program that includes activation of Egfr signalling. Moreover, our findings reveal a key role for the Yap regenerative pathway in driving cancer initiation.

Ionizing radiation induces stem cell-like properties in a caspase-dependent manner in Drosophila.

Cancer treatments including ionizing radiation (IR) can induce cancer stem cell-like properties in non-stem cancer cells, an outcome that can interfere with therapeutic success. Yet, we understand little about what consequences of IR induces stem cell like properties and why some cancer cells show this response but not others. In previous studies, we identified a pool of epithelial cells in Drosophila larval wing discs that display IR-induced stem cell-like properties. These cells are resistant to killing by IR and, after radiation damage, change fate and translocate to regenerate parts of the disc that suffered more cell death. Here, we report the identification of two new pools of cells with IR-induced regenerative capability. We addressed how IR exposure results in the induction of stem cell-like behavior, and found a requirement for IR-induced caspase activity and for Zfh2, a transcription factor and an effector in the JAK/STAT pathway. Unexpectedly, the requirement for caspase activity was cell-autonomous within cell populations that display regenerative behavior. We propose a model in which the requirement for caspase activity and Zfh2 can be explained by apoptotic and non-apoptotic functions of caspases in the induction of stem cell-like behavior.

Comparative evaluation of low-level laser therapy on proliferation of long-term cryopreserved human dental pulp cells isolated from deciduous and permanent teeth.

The aim of the current study was to evaluate the proliferative effect of low-level laser therapy on long-term cryopreserved dental pulp stem cells (DPSCS) and stem cells from human exfoliated deciduous teeth (SHEDS). The DPSCS and SHEDS were divided into 2 main groups according to gallium aluminum arsenide (GaAIAs) diode laser irradiation densities as 5 J/cm2 and 7 J/cm2. Each main group was further divided into 4 groups according to laser irradiation periods as 0, 24, 48, 72 h groups. During the incubation periods, cells received laser irradiation in every 24 h according to their groups and were put into incubator after irradiation. Cell groups that were not subjected to laser irradiation were served as control groups. Viabilities of cells were determined via MTT assay at the end of all incubation periods, and data were statistically analyzed. Laser irradiation demonstrated significant effects on proliferation rate of DPSCs and SHEDs in comparison with control. Intragroup comparison data of DPSCS revealed that repetitive laser irradiation for long term (72 h) increased the cellular viability significantly in comparison with all other treatment groups; however, no significant differences were found when energy densities were compared within each time interval, except for 48 h group at which irradiation with 7 J/cm2 provided significantly higher cell viability rates of SHEDS. DPSCs showed significantly higher cellular viability than SHEDs only for the 7 J/cm2 energy density in 72 h. Longer term (72 h) repetitive laser irradiation with energy densities of 5 and 7 J/cm2 (wavelength of 980 nm) may be recommended to induce the proliferative effect on long-term cryopreserved DPSCS and SHEDS.

Comparison of responses of melanocyte lineages from p75(+) and p75(-) human scalp-derived neural crest stem cells under phototherapy.

Phototherapy is an effective therapeutic option in the treatment of vitiligo; however, responses varied among the different types. The underlying mechanism has scarcely been investigated. To investigate and compare the effects of phototherapy on the mutation of melanocyte lineage differentiated from human scalp-derived neural crest stem cells (HS-NCSCs) with p75 neurotrophin receptor expression positive and p75 neurotrophin receptor expression negative group in vitro, the HS-NCSCs were isolated from fetal scalp tissue, which is identified by immunofluorescent staining. The p75(+) and p75(-) cells from HS-NCSCs were isolated by magnetic cell sorting, respectively. The embryonic neural crest stem cell biomarkers were detected by RT-PCR. Narrow-band UVB (NB-UVB) was used to irradiate the cells. Cell proliferation was evaluated by cell count. Tyrosinase, Tyrp1, and Tyrp2 gene expression were measured by quantitative RT-PCR. Tyrosinase and GRCR protein levels were investigated by Western blot analysis. The electrophoretic strip showed that Sox2, Oct4, Sox10, and Nestin of p75(+) HS-NCSCs were brighter than the p75(-) HS-NCSCs. After the same dose radiation with NB-UVB, the cell proliferation of p75(+) group showed less inhibitory rate compared with the p75(-) HS-NCSCs. The tyrosinase mRNA and protein expression of differentiated melanocytes increased significantly in the group of p75(+) HS-NCSCs compared with the p75(-) group. The melanocytic mutation of p75(+) HS-NCSCs increased significantly compared with the p75(-) HS-NCSCs under NB-UVB, which indicated there were more melanocyte precursors in the differentiated cells from p75(+) HS-NCSCs. This may provide new insights for the different repigmentation efficacy of segmental and non-segmental vitiligo.

Pulsed Electromagnetic Fields in Bone Healing: Molecular Pathways and Clinical Applications.

In this article, we provide an extensive review of the recent literature of the signaling pathways modulated by Pulsed Electromagnetic Fields (PEMFs) and PEMFs clinical application. A review of the literature was performed on two medical electronic databases (PubMed and Embase) from 3 to 5 March 2021. Three authors performed the evaluation of the studies and the data extraction. All studies for this review were selected following these inclusion criteria: studies written in English, studies available in full text and studies published in peer-reviewed journal. Molecular biology, identifying cell membrane receptors and pathways involved in bone healing, and studying PEMFs target of action are giving a solid basis for clinical applications of PEMFs. However, further biology studies and clinical trials with clear and standardized parameters (intensity, frequency, dose, duration, type of coil) are required to clarify the precise dose-response relationship and to understand the real applications in clinical practice of PEMFs.

Novel Strategies for Nanoparticle-Based Radiosensitization in Glioblastoma.

Radiotherapy (RT) is one of the cornerstones in the current treatment paradigm for glioblastoma (GBM). However, little has changed in the management of GBM since the establishment of the current protocol in 2005, and the prognosis remains grim. Radioresistance is one of the hallmarks for treatment failure, and different therapeutic strategies are aimed at overcoming it. Among these strategies, nanomedicine has advantages over conventional tumor therapeutics, including improvements in drug delivery and enhanced antitumor properties. Radiosensitizing strategies using nanoparticles (NP) are actively under study and hold promise to improve the treatment response. We aim to describe the basis of nanomedicine for GBM treatment, current evidence in radiosensitization efforts using nanoparticles, and novel strategies, such as preoperative radiation, that could be synergized with nanoradiosensitizers.

BHLHA15-Positive Secretory Precursor Cells Can Give Rise to Tumors in Intestine and Colon in Mice.

BACKGROUND & AIMS: The intestinal epithelium is maintained by long-lived intestinal stem cells (ISCs) that reside near the crypt base. Above the ISC zone, there are short-lived progenitors that normally give rise to lineage-specific differentiated cell types but can dedifferentiate into ISCs in certain circumstances. However, the role of epithelial dedifferentiation in cancer development has not been fully elucidated. METHODS: We performed studies with Bhlha15-CreERT, Lgr5-DTR-GFP, Apcflox/flox, LSL-Notch (IC), and R26-reporter strains of mice. Some mice were given diphtheria toxin to ablate Lgr5-positive cells, were irradiated, or were given 5-fluorouracil, hydroxyurea, doxorubicin, or dextran sodium sulfate to induce intestinal or colonic tissue injury. In intestinal tissues, we analyzed the fate of progeny that expressed Bhlha15. We used microarrays and reverse-transcription PCR to analyze gene expression patterns in healthy and injured intestinal tissues and in tumors. We analyzed gene expression patterns in human colorectal tumors using The Cancer Genome Atlas data set. RESULTS: Bhlha15 identified Paneth cells and short-lived secretory precursors (including pre-Paneth label-retaining cells) located just above the ISC zone in the intestinal epithelium. Bhlha15+ cells had no plasticity after loss of Lgr5-positive cells or irradiation. However, Bhlha15+ secretory precursors started to supply the enterocyte lineage after doxorubicin-induced epithelial injury in a Notch-dependent manner. Sustained activation of Notch converts Bhlha15+ secretory precursors to long-lived enterocyte progenitors. Administration of doxorubicin and expression of an activated form of Notch resulted in a gene expression pattern associated with enterocyte progenitors, whereas only sustained activation of Notch altered gene expression patterns in Bhlha15+ precursors toward those of ISCs. Bhlha15+ enterocyte progenitors with sustained activation of Notch formed intestinal tumors with serrated features in mice with disruption of Apc. In the colon, Bhlha15 marked secretory precursors that became stem-like, cancer-initiating cells after dextran sodium sulfate-induced injury, via activation of Src and YAP signaling. In analyses of human colorectal tumors, we associated activation of Notch with chromosome instability-type tumors with serrated features in the left colon. CONCLUSIONS: In mice, we found that short-lived precursors can undergo permanent reprogramming by activation of Notch and YAP signaling. These cells could mediate tumor formation in addition to traditional ISCs.

Preconditioning adipose-derived stem cells with photobiomodulation significantly increased bone healing in a critical size femoral defect in rats.

We assessed the combined impacts of human demineralized bone matrix (hDBM) scaffold, adipose-derived stem cells (hADS), and photobiomodulation (PBM) on bone repair of a critical size femoral defect (CSFD) in 72 rats. The rats were divided into six groups: control (group 1); ADS (group 2 - ADS transplanted into hDBM); PBM (group 3 - PBM-treated CSFDs); ADS + PBM in vivo (group 4 - ADS transplanted into hDBM and the CSFDs were treated with PBM in vivo); ADS + PBM in vitro (group 5 - ADS were treated with PBM in vitro, then seeded into hDBM); and ADS + PBM in vitro+in vivo (group 6 - PBM-treated ADS were seeded into hDBM, and the CSFDs were treated with PBM in vivo. At the anabolic phase (2 weeks after surgery), bone strength parameters of the groups 5, 6, and 4 were statistically greater than the control, ADS, and PBM in vivo groups (all, p = 0.000). Computed tomography (CT) scans during the catabolic phase (6 weeks after surgery) of bone healing revealed that the Hounsfield unit (HU) of CSFD in the groups 2 (p = 0.000) and 5 (p = 0.019) groups were statistically greater than the control group. The groups 5, 4, and 6 had significantly increased bone strength parameters compared with the PBM in vivo, control, and ADS groups (all, p = 0.000). The group 5 was statistically better than the groups 4, and 6 (both, p = 0.000). In vitro preconditioned of hADS with PBM significantly increased bone repair in a rat model of CSFD in vivo.

Clinically Approved Carbon Nanoparticles with Oral Administration for Intestinal Radioprotection via Protecting the Small Intestinal Crypt Stem Cells and Maintaining the Balance of Intestinal Flora.

The exploration of an old drug for new biomedical applications has an absolute predominance in shortening the clinical conversion time of drugs for clinical application. In this work, carbon nanoparticles suspension injection (CNSI), the first clinically approved carbon nanoparticles in China, is explored as a new nano-radioprotective agent for potent intestinal radioprotection. CNSI shows powerful radioprotective performance in the intestine under oral administration, including efficient free radical scavenging ability, good biosafety, high chemical stability, and relatively long retention time. For example, CNSI shows high reactive oxygen species (ROS) scavenging activities, which effectively alleviates the mitochondrial dysfunction and DNA double-strand breaks to protect the cells against radiation-induced damage. Most importantly, this efficient ROS scavenging ability greatly helps restrain the apoptosis of the small intestinal epithelial and crypt stem cells, which decreases the damage of the mechanical barrier and thus relieves radiation enteritis. Moreover, CNSI helps remove the free radicals in the intestinal microenvironment and thus maintain the balance of intestinal flora so as to mitigate the radiation enteritis. The finding suggests a new application of clinically approved carbon nanoparticles, which not only promotes the development of new intestinal radioprotector, but also has a great potential for clinical transformation.

ß-Arrestin1-mediated decrease in endoplasmic reticulum stress impairs intestinal stem cell proliferation following radiation.

Gastrointestinal toxicity limits the clinical application of abdominal and pelvic radiotherapy and currently has no effective treatment. Intestinal leucine-rich-repeat-containing GPCR 5 (Lgr5)-positive stem cell depletion and loss of proliferative ability due to radiation may be the primary factors causing intestinal injury following radiation. Here, we report the critical role of ß-arrestin1 (ßarr1) in radiation-induced intestinal injury. Intestinal ßarr1 was highly expressed in radiation enteritis and in a radiation model. ßarr1 knockout (KO) or knockdown mice exhibited increased proliferation in intestinal Lgr5+ stem cell, crypt reproduction, and survival following radiation. Unexpectedly, the beneficial effects of ßarr1 deficiency on intestinal stem cells in response to radiation were compromised when the endoplasmic reticulum stress-related protein kinase RNA-like ER kinase (PERK)/eukaryotic initiation factor-2α (eIF2α) pathway was inhibited, and this result was further supported in vitro. Furthermore, we found that ßarr1 knockdown with small interfering RNA significantly enhanced intestinal Lgr5+ stem cell proliferation after radiation via directly targeting PERK. ßarr1 offers a promising target for mitigating radiation-induced intestinal injury.-Liu, Z., Jiang, J., He, Q., Liu, Z., Yang, Z., Xu, J., Huang, Z., Wu, B. ß-Arrestin1-mediated decrease in endoplasmic reticulum stress impairs intestinal stem cell proliferation following radiation.