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.

Comparison of Three Antagonists of Hedgehog Pathway to Promote Skeletal Muscle Regeneration after High Dose Irradiation

The current geopolitical context has brought the radiological nuclear risk to the forefront of concerns. High-dose localized radiation exposure leads to the development of a musculocutaneous radiation syndrome affecting the skin and subcutaneous muscles. Despite the implementation of a gold standard treatment based on an invasive surgical procedure coupled with autologous cell therapy, a muscular defect frequently persists. Targeting the modulation of the Hedgehog (Hh) signaling pathway appears to be a promising therapeutic approach. Activation of this pathway enhances cell survival and promotes proliferation after irradiation, while inhibition by Cyclopamine facilitates differentiation. In this study, we compared the effects of three antagonists of Hh, Cyclopamine (CA), Vismodegib (VDG) and Sonidegib (SDG) on differentiation. A stable cell line of murine myoblasts, C2C12, was exposed to X-ray radiation (5 Gy) and treated with CA, VDG or SDG. Analysis of proliferation, survival (apoptosis), morphology, myogenesis genes expression and proteins production were performed. According to the results, VDG does not have a significant impact on C2C12 cells. SDG increases the expression/production of differentiation markers to a similar extent as CA, while morphologically, SDG proves to be more effective than CA. To conclude, SDG can be used in the same way as CA but already has a marketing authorization with an indication against basal cell cancers, facilitating their use in vivo. This proof of concept demonstrates that SDG represents a promising alternative to CA to promotes differentiation of murine myoblasts. Future studies on isolated and cultured satellite cells and in vivo will test this proof of concept.

Dynamic role of CUL4B in radiation-induced intestinal injury-regeneration

CUL4B, a crucial scaffolding protein in the largest E3 ubiquitin ligase complex CRL4B, is involved in a broad range of physiological and pathological processes. While previous research has shown that CUL4B participates in maintaining intestinal homeostasis and function, its involvement in facilitating intestinal recovery following ionizing radiation (IR) damage has not been fully elucidated. Here, we utilized in vivo and in vitro models to decipher the role of CUL4B in intestinal repair after IR-injury. Our findings demonstrated that prior to radiation exposure, CUL4B inhibited the ubiquitination modification of PSME3, which led to the accumulation of PSME3 and subsequent negative regulation of p53-mediated apoptosis. In contrast, after radiation, CUL4B dissociated from PSME3 and translocated into the nucleus at phosphorylated histones H2A (γH2AX) foci, thereby impeding DNA damage repair and augmenting p53-mediated apoptosis through inhibition of BRCA1 phosphorylation and RAD51. Our study elucidated the dynamic role of CUL4B in the repair of radiation-induced intestinal damage and uncovered novel molecular mechanisms underlying the repair process, suggesting a potential therapeutic strategy of intestinal damage after radiation therapy for cancers.

Corticosteroids impair epithelial regeneration in immune-mediated intestinal damage

Corticosteroid treatment (CST) failure is associated with poor outcomes for patients with gastrointestinal (GI) graft-versus-host disease (GVHD). CST is intended to target the immune system, but the glucocorticoid receptor (GR) is widely expressed, including within the intestines, where its effects are poorly understood. Here, we report that corticosteroids (CS) directly targeted intestinal epithelium, potentially worsening immune-mediated GI damage. CS administered to mice in vivo and intestinal organoid cultures ex vivo reduced epithelial proliferation. Following irradiation, immediate CST mitigated GI damage but delayed treatment attenuated regeneration and exacerbated damage. In a murine steroid-refractory (SR) GVHD model, CST impaired epithelial regeneration, worsened crypt loss, and reduced intestinal stem cell (ISC) frequencies. CST also exacerbated immune-mediated damage in organoid cultures with SR, GR-deficient T cells or IFN-γ. These findings correlated with CS-dependent changes in apoptosis-related gene expression and STAT3-related epithelial proliferation. Conversely, IL-22 administration enhanced STAT3 activity and overcame CS-mediated attenuation of regeneration, reducing crypt loss and promoting ISC expansion in steroid-treated mice with GVHD. Therefore, CST has the potential to exacerbate GI damage if it fails to control the damage-inducing immune response, but this risk may be countered by strategies augmenting epithelial regeneration, thus providing a rationale for clinical approaches combining such tissue-targeted therapies with immunosuppression.

Differential gene expression analysis identified determinants of cell fate plasticity during radiation-induced regeneration in Drosophila

Ionizing radiation (IR) is used to treat half of all cancer patients because of its ability to kill cells. IR, however, can induce stem cell-like properties in non-stem cancer cells, potentiating tumor regrowth and reduced therapeutic success. We identified previously a subpopulation of cells in Drosophila larval wing discs that exhibit IR-induced stem cell-like properties. These cells reside in the future wing hinge, are resistant to IR-induced apoptosis, and are capable of translocating, changing fate, and participating in regenerating the pouch that suffers more IR-induced apoptosis. We used here a combination of lineage tracing, FACS-sorting of cells that change fate, genome-wide RNAseq, and functional testing of 42 genes, to identify two key changes that are required cell-autonomously for IR-induced hinge-to-pouch fate change: (1) repression of hinge determinants Wg (Drosophila Wnt1) and conserved zinc-finger transcription factor Zfh2 and (2) upregulation of three ribosome biogenesis factors. Additional data indicate a role for Myc, a transcriptional activator of ribosome biogenesis genes, in the process. These results provide a molecular understanding of IR-induced cell fate plasticity that may be leveraged to improve radiation therapy.

Ionizing radiation (IR) is used to treat half of all cancer patients because of its ability to kill cells but treatment failures are common because tumors grow back (regenerate). Here, we asked which changes in the properties of cells facilitate regeneration in Drosophila (fruit flies) after exposure to radiation. We identified six genes whose products increase or decrease the regenerative potential of cells. These results help us understand how tissues regenerate after IR damage and will aid in designing better therapies that involve radiation.

Exposure of Human Skin Organoids to Low Genotoxic Stress Can Promote Epithelial-to-Mesenchymal Transition in Regenerating Keratinocyte Precursor Cells

For the general population, medical diagnosis is a major cause of exposure to low genotoxic stress, as various imaging techniques deliver low doses of ionizing radiation. Our study investigated the consequences of low genotoxic stress on a keratinocyte precursor fraction that includes stem and progenitor cells, which are at risk for carcinoma development. Human skin organoids were bioengineered according to a clinically-relevant model, exposed to a single 50 mGy dose of γ rays, and then xeno-transplanted in nude mice to follow full epidermis generation in an in vivo context. Twenty days post-xenografting, mature skin grafts were sampled and analyzed by semi-quantitative immuno-histochemical methods. Pre-transplantation exposure to 50 mGy of immature human skin organoids did not compromise engraftment, but half of xenografts generated from irradiated precursors exhibited areas displaying focal dysplasia, originating from the basal layer of the epidermis. Characteristics of epithelial-to-mesenchymal transition (EMT) were documented in these dysplastic areas, including loss of basal cell polarity and cohesiveness, epithelial marker decreases, ectopic expression of the mesenchymal marker α-SMA and expression of the EMT promoter ZEB1. Taken together, these data show that a very low level of radiative stress in regenerating keratinocyte stem and precursor cells can induce a micro-environment that may constitute a favorable context for long-term carcinogenesis.

Opposite effects of low intensity light of different wavelengths on the planarian regeneration rate

Planarian freshwater flatworms have the unique ability to regenerate due to stem cell activity. The process of regeneration is extremely sensitive to various factors, including light radiation. Here, the effect of low-intensity LED light of different wavelengths on regeneration, stem cell proliferation and gene expression associated with these processes was studied. LED matrices with different wavelengths (red (λ_max = 635 nm), green (λ_max = 520 nm) and blue (λ_max = 463 nm), as well as LED laser diodes (red (λ_max = 638.5 nm), green (λ_max = 533 nm) and blue (λ_max = 420 nm), were used in the experiments. Computer-assisted morphometry, whole-mount immunocytochemical study and RT-PCR were used to analyze the biological effects of LED light exposure on the planarian regeneration in vivo. It was found that a one-time exposure of regenerating planarians with low-intensity red light diodes stimulated head blastema growth in a dose-dependent manner (up to 40%). The green light exposure of planarians resulted in the opposite effect, showing a reduced head blastema growth rate by up to 21%. The blue light exposure did not lead to any changes in the rate of head blastema growth. The maximum effects of light exposure were observed at a dose of 175.2 mJ/cm². No significant differences were revealed in the dynamics of neoblasts' (planarian stem cells) proliferation under red and green light exposure. However, the RT-PCR gene expression analysis of 46 wound-induced genes revealed their up-regulation upon red LED light exposure, and down-regulation upon green light exposure. Thus, we have demonstrated that the planarian regeneration process is rather sensitive to the effects of low-intensity light radiation of certain wavelengths, the biological activity of red and green light being dictated by the different expression of the genes regulating transcriptional activity.

Self-Activated Electrical Stimulation for Effective Hair Regeneration via a Wearable Omnidirectional Pulse Generator

Hair loss, a common and distressing symptom, has been plaguing humans. Various pharmacological and nonpharmacological treatments have been widely studied to achieve the desired effect for hair regeneration. As a nonpharmacological physical approach, physiologically appropriate alternating electric field plays a key role in the field of regenerative tissue engineering. Here, a universal motion-activated and wearable electric stimulation device that can effectively promote hair regeneration via random body motions was designed. Significantly facilitated hair regeneration results were obtained from Sprague-Dawley rats and nude mice. Higher hair follicle density and longer hair shaft length were observed on Sprague-Dawley rats when the device was employed compared to conventional pharmacological treatments. The device can also improve the secretion of vascular endothelial growth factor and keratinocyte growth factor and thereby alleviate hair keratin disorder, increase the number of hair follicles, and promote hair regeneration on genetically defective nude mice. This work provides an effective hair regeneration strategy in the context of a nonpharmacological self-powered wearable electronic device.

PTPσ inhibitors promote hematopoietic stem cell regeneration

Receptor type protein tyrosine phosphatase-sigma (PTPσ) is primarily expressed by adult neurons and regulates neural regeneration. We recently discovered that PTPσ is also expressed by hematopoietic stem cells (HSCs). Here, we describe small molecule inhibitors of PTPσ that promote HSC regeneration in vivo. Systemic administration of the PTPσ inhibitor, DJ001, or its analog, to irradiated mice promotes HSC regeneration, accelerates hematologic recovery, and improves survival. Similarly, DJ001 administration accelerates hematologic recovery in mice treated with 5-fluorouracil chemotherapy. DJ001 displays high specificity for PTPσ and antagonizes PTPσ via unique non-competitive, allosteric binding. Mechanistically, DJ001 suppresses radiation-induced HSC apoptosis via activation of the RhoGTPase, RAC1, and induction of BCL-XL. Furthermore, treatment of irradiated human HSCs with DJ001 promotes the regeneration of human HSCs capable of multilineage in vivo repopulation. These studies demonstrate the therapeutic potential of selective, small-molecule PTPσ inhibitors for human hematopoietic regeneration.

Sutureless repair of corneal injuries using naturally derived bioadhesive hydrogels

Corneal injuries are common causes of visual impairment worldwide. Accordingly, there is an unmet need for transparent biomaterials that have high adhesion, cohesion, and regenerative properties. Herein, we engineer a highly biocompatible and transparent bioadhesive for corneal reconstruction using a visible light cross-linkable, naturally derived polymer, GelCORE (gel for corneal regeneration). The physical properties of GelCORE could be finely tuned by changing prepolymer concentration and photocrosslinking time. GelCORE revealed higher tissue adhesion compared to commercial adhesives. Furthermore, in situ photopolymerization of GelCORE facilitated easy delivery to the cornea, allowing for bioadhesive curing precisely according to the required geometry of the defect. In vivo experiments, using a rabbit stromal defect model, showed that bioadhesive could effectively seal corneal defects and induce stromal regeneration and re-epithelialization. Overall, GelCORE has many advantages including low cost and ease of production and use. This makes GelCORE a promising bioadhesive for corneal repair.

1-(4-nitrobenzenesulfonyl)-4-penylpiperazine increases the number of Peyer's patch-associated regenerating crypts in the small intestines after radiation injury

OBJECTIVE

Exposure to lethal doses of radiation has severe effects on normal tissues. Exposed individuals experience a plethora of symptoms in different organ systems including the gastrointestinal (GI) tract, summarized as Acute Radiation Syndrome (ARS). There are currently no approved drugs for mitigating GI-ARS. A recent high-throughput screen performed at the UCLA Center for Medical Countermeasures against Radiation identified compounds containing sulfonylpiperazine groups with radiation mitigation properties to the hematopoietic system and the gut. Among these 1-[(4-Nitrophenyl)sulfonyl]-4-phenylpiperazine (Compound #5) efficiently mitigated gastrointestinal ARS. However, the mechanism of action and target cells of this drug is still unknown. In this study we examined if Compound #5 affects gut-associated lymphoid tissue (GALT) with its subepithelial domes called Peyer's patches.

METHODS

C3H mice were irradiated with 0 or 12 Gy total body irradiation (TBI). A single dose of Compound #5 or solvent was administered subcutaneously 24 h later. 48 h after irradiation the mice were sacrificed, and the guts examined for changes in the number of visible Peyer's patches. In some experiments the mice received 4 daily injections of treatment and were sacrificed 96 h after TBI. For immune histochemistry gut tissues were fixed in formalin and embedded in paraffin blocks. Sections were stained with H&E, anti-Ki67 or a TUNEL assay to assess the number of regenerating crypts, mitotic and apoptotic indices. Cells isolated from Peyer's patches were subjected to immune profiling using flow cytometry.

RESULTS

Compound #5 significantly increased the number of visible Peyer's patches when compared to its control in non-irradiated and irradiated mice. Additionally, assessment of total cells per Peyer's patch isolated from these mice demonstrated an overall increase in the total number of Peyer's patch cells per mouse in Compound #5-treated mice. In non-irradiated animals the number of CD11b^high in Peyer's patches increased significantly. These Compound #5-driven increases did not coincide with a decrease in apoptosis or an increase in proliferation in the germinal centers inside Peyer's patches 24 h after drug treatment. A single dose of Compound #5 significantly increased the number of CD45⁺ cells after 12 Gy TBI. Importantly, 96 h after 12 Gy TBI Compound #5 induced a significant rise in the number of visible Peyer's patches and the number of Peyer's patch-associated regenerating crypts.

CONCLUSION

In summary, our study provides evidence that Compound #5 leads to an influx of immune cells into GALT, thereby supporting crypt regeneration preferentially in the proximity of Peyer's patches.

Infrared Laser-Mediated Gene Induction at the Single-Cell Level in the Regenerating Tail of Xenopus laevis Tadpoles

We describe a precise and reproducible gene-induction method in the amphibian, Xenopus laevis Tetrapod amphibians are excellent models for studying the mechanisms of three-dimensional organ regeneration because they have an exceptionally high regenerative ability. However, spatial and temporal manipulation of gene expression has been difficult in amphibians, hindering studies on the molecular mechanisms of organ regeneration. Recently, however, development of a Xenopus transgenic system with a heat-shock-inducible gene has enabled the manipulation of specific genes. Here, we applied an infrared laser-evoked gene operator (IR-LEGO) system to the regenerating tail of Xenopus tadpoles. In this method, a local heat shock by laser irradiation induces gene expression at the single-cell level. After amputation, Xenopus tadpoles regenerate a functional tail, including spinal cord. The regenerating tail is flat and transparent enabling the targeting of individual cells by laser irradiation. In this protocol, a single neural progenitor cell in the spinal cord of the regenerating tail is labeled with heat-shock-inducible green fluorescent protein (GFP). Gene induction at the single-cell level provides a method for rigorous cell-lineage tracing and for analyzing gene function in both cell-autonomous and noncell-autonomous contexts. The method can be modified to study the regeneration of limbs or organs in other amphibians, including Xenopus tropicalis, newts, and salamanders.

[Low level laser therapy : A narrative literature review on the efficacy in the treatment of rheumatic orthopaedic conditions]

BACKGROUND

In low level laser therapy (LLLT) low wattage lasers are used to irradiate the affected skin areas, joints, nerves, muscles and tendons without any sensation or thermal damage. Although the exact mechanism of its effect is still unknown, it seems beyond dispute that LLLT induces a variety of stimulating processes at the cellular level affecting cell repair mechanisms, the vascular system and lymphatic system. LLLT has been popular among orthopaedic practitioners for many years, whereas university medicine has remained rather sceptical about it.

OBJECTIVES

Overview of studies on the efficacy of LLLT in the treatment of rheumatic orthopaedic conditions, i. e. muscle, tendon lesions and arthropathies.

MATERIALS AND METHODS

Narrative literature review (PubMed, Web of Science).

RESULTS

While earlier studies often failed to demonstrate the efficacy of LLLT, several recent studies of increasing quality proved the efficacy of LLLT in the treatment of multiple musculoskeletal pain syndromes like neck or lower back pain, tendinopathies (especially of the Achilles tendon) and epicondylolpathies, chronic inflammatory joint disorders like rheumatoid arthritis or chronic degenerative osteoarthritis of the large and small joints. In addition, there is recent evidence that LLLT can have a preventive capacity and can enhance muscle strength and accelerate muscle regeneration.

CONCLUSION

LLLT shows potential as an effective, noninvasive, safe and cost-efficient means to treat and prevent a variety of acute and chronic musculoskeletal conditions. Further randomized controlled studies, however, are required to confirm this positive assessment.

Suppression of luteinizing hormone enhances HSC recovery after hematopoietic injury

There is a substantial unmet clinical need for new strategies to protect the hematopoietic stem cell (HSC) pool and regenerate hematopoiesis after radiation injury from either cancer therapy or accidental exposure. Increasing evidence suggests that sex hormones, beyond their role in promoting sexual dimorphism, regulate HSC self-renewal, differentiation, and proliferation. We and others have previously reported that sex-steroid ablation promotes bone marrow (BM) lymphopoiesis and HSC recovery in aged and immunodepleted mice. Here we found that a luteinizing hormone (LH)-releasing hormone antagonist (LHRH-Ant), currently in wide clinical use for sex-steroid inhibition, promoted hematopoietic recovery and mouse survival when administered 24 h after an otherwise-lethal dose of total-body irradiation (L-TBI). Unexpectedly, this protective effect was independent of sex steroids and instead relied on suppression of LH levels. Human and mouse long-term self-renewing HSCs (LT-HSCs) expressed high levels of the LH/choriogonadotropin receptor (LHCGR) and expanded ex vivo when stimulated with LH. In contrast, the suppression of LH after L-TBI inhibited entry of HSCs into the cell cycle, thus promoting HSC quiescence and protecting the cells from exhaustion. These findings reveal a role of LH in regulating HSC function and offer a new therapeutic approach for hematopoietic regeneration after hematopoietic injury.

Rack1 function in intestinal epithelia: regulating crypt cell proliferation and regeneration and promoting differentiation and apoptosis

Previously, we showed that receptor for activated C kinase 1 (Rack1) regulates growth of colon cells in vitro, partly by suppressing Src kinase activity at key cell cycle checkpoints, in apoptotic and cell survival pathways and at cell-cell adhesions. Here, we generated mouse models of Rack1 deficiency to assess Rack1's function in intestinal epithelia in vivo. Intestinal Rack1 deficiency resulted in proliferation of crypt cells, diminished differentiation of crypt cells into enterocyte, goblet, and enteroendocrine cell lineages, and expansion of Paneth cell populations. Following radiation injury, the morphology of Rack1-deleted small bowel was strikingly abnormal with development of large polypoid structures that contained many partly formed villi, numerous back-to-back elongated and regenerating crypts, and high-grade dysplasia in surface epithelia. These abnormalities were not observed in Rack1-expressing areas of intestine or in control mice. Following irradiation, apoptosis of enterocytes was strikingly reduced in Rack1-deleted epithelia. These novel findings reveal key functions for Rack1 in regulating growth of intestinal epithelia: suppressing crypt cell proliferation and regeneration, promoting differentiation and apoptosis, and repressing development of neoplasia. NEW & NOTEWORTHY Our findings reveal novel functions for receptor for activated C kinase 1 (Rack1) in regulating growth of intestinal epithelia: suppressing crypt cell proliferation and regeneration, promoting differentiation and apoptosis, and repressing development of neoplasia.

Effect of radiation-induced endothelial cell injury on platelet regeneration by megakaryocytes

Thrombocytopenia is an important cause of hemorrhage and death after radiation injury, but the pathogenesis of radiation-induced thrombocytopenia has not been fully characterized. Here, we investigated the influence of radiation-induced endothelial cell injury on platelet regeneration. We found that human umbilical vein endothelial cells (HUVECs) underwent a high rate of apoptosis, accompanied by a significant reduction in the expression of vascular endothelial growth factor (VEGF) at 96 h after radiation. Subsequent investigations revealed that radiation injury lowered the ability of HUVECs to attract migrating megakaryocytes (MKs). Moreover, the adhesion of MKs to HUVECs was markedly reduced when HUVECs were exposed to radiation, accompanied by a decreased production of platelets by MKs. In vivo study showed that VEGF treatment significantly promoted the migration of MKs into the vascular niche and accelerated platelet recovery in irradiated mice. Our studies demonstrate that endothelial cell injury contributes to the slow recovery of platelets after radiation, which provides a deeper insight into the pathogenesis of thrombocytopenia induced by radiation.

The Potential of Bone Marrow Stem Cells to Correct Liver Dysfunction in a Mouse Model of Wilson's Disease

Metabolic liver diseases are excellent targets for correction using novel stem cell, hepatocyte, and gene therapies. In this study, the use of bone marrow stem cell transplantation to correct liver disease in the toxic milk (tx) mouse, a murine model for Wilson's disease, was evaluated. Preconditioning with sublethal irradiation, dietary copper loading, and the influence of cell transplantation sites were assessed. Recipient tx mice were sublethally irradiated (4 Gy) prior to transplantation with bone marrow stem cells harvested from normal congenic (DL) littermates. Of 46 transplanted tx mice, 11 demonstrated genotypic repopulation in the liver. Sublethal irradiation was found to be essential for donor cell engraftment and liver repopulation. Dietary copper loading did not improve cell engraftment and repopulation results. Both intravenously and intrasplenically transplanted cells produced similar repopulation successes. Direct evidence of functionality and disease correction following liver repopulation was observed in the 11 mice where liver copper levels were significantly reduced when compared with mice with no liver repopulation. The reversal of copper loading with bone marrow cells is similar to the level of correction seen when normal congenic liver cells are used. Transplantation of bone marrow cells partially corrects the metabolic phenotype in a mouse model for Wilson's disease.

Biological effects and medical applications of infrared radiation

Infrared (IR) radiation is electromagnetic radiation with wavelengths between 760nm and 100,000nm. Low-level light therapy (LLLT) or photobiomodulation (PBM) therapy generally employs light at red and near-infrared wavelengths (600-100nm) to modulate biological activity. Many factors, conditions, and parameters influence the therapeutic effects of IR, including fluence, irradiance, treatment timing and repetition, pulsing, and wavelength. Increasing evidence suggests that IR can carry out photostimulation and photobiomodulation effects particularly benefiting neural stimulation, wound healing, and cancer treatment. Nerve cells respond particularly well to IR, which has been proposed for a range of neurostimulation and neuromodulation applications, and recent progress in neural stimulation and regeneration are discussed in this review. The applications of IR therapy have moved on rapidly in recent years. For example, IR therapy has been developed that does not actually require an external power source, such as IR-emitting materials, and garments that can be powered by body heat alone. Another area of interest is the possible involvement of solar IR radiation in photoaging or photorejuvenation as opposites sides of the coin, and whether sunscreens should protect against solar IR? A better understanding of new developments and biological implications of IR could help us to improve therapeutic effectiveness or develop new methods of PBM using IR wavelengths.

Periodontal and peri-implant wound healing following laser therapy

Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

Single-cell imaging of normal and malignant cell engraftment into optically clear prkdc-null SCID zebrafish

Cell transplantation into immunodeficient mice has revolutionized our understanding of regeneration, stem cell self-renewal, and cancer; yet models for direct imaging of engrafted cells has been limited. Here, we characterize zebrafish with mutations in recombination activating gene 2 (rag2), DNA-dependent protein kinase (prkdc), and janus kinase 3 (jak3). Histology, RNA sequencing, and single-cell transcriptional profiling of blood showed that rag2 hypomorphic mutant zebrafish lack T cells, whereas prkdc deficiency results in loss of mature T and B cells and jak3 in T and putative Natural Killer cells. Although all mutant lines engraft fluorescently labeled normal and malignant cells, only the prkdc mutant fish reproduced as homozygotes and also survived injury after cell transplantation. Engraftment into optically clear casper, prkdc-mutant zebrafish facilitated dynamic live cell imaging of muscle regeneration, repopulation of muscle stem cells within their endogenous niche, and muscle fiber fusion at single-cell resolution. Serial imaging approaches also uncovered stochasticity in fluorescently labeled leukemia regrowth after competitive cell transplantation into prkdc mutant fish, providing refined models to assess clonal dominance and progression in the zebrafish. Our experiments provide an optimized and facile transplantation model, the casper, prkdc mutant zebrafish, for efficient engraftment and direct visualization of fluorescently labeled normal and malignant cells at single-cell resolution.

[WEAK COMBINED MAGNETIC FIELDS ADJUSTED TO THE PARAMETRIC RESONANCE FOR Ca2+ INTENSIFY DYSTROPHIN SYNTHESIS IN MDX MICE SKELETAL MUSCLES AFTER CELL THERAPY]

The mdx mice are an X-linked myopathic mutants, an animal model for human Duchenne muscular dystrophy (DMD). Mdx mice muscles are characterized by high level of striated muscle fibers (SMF) death followed by regeneration. As a result most SMFs of mdx mice have centrally located nuclei. The possibility of using stem cells therapy for the correction of DMD is actively being studied. One of the approaches to the usage of bone marrow stem cells for cellular therapy of DMD is the replacement of bone marrow after irradiation by X-rays. This method however does not give significant increase of dystrophin synthesis in mdx mice muscles fibers. We have tried to affect the mice after bone marrow transplantation by weak combined magnetic fields adjusted to the parametric resonance for Ca2+(Ca(2+)-MF) based on the data that the weak combined magnetic fields influence on tissues regeneration. We observed a significant increase in the proportion of dystrophin-positive SMFs in group of mdx mice radiation chimera 5 Gy and 3 Gy which was additionally exposed in Ca(2+)-MF in comparison with the control mdx mice and the group of mdx mice radiation chimera 5 Gy and 3 Gy which was kept in terrestrial magnetic field 2 months after chimera preparation--up to 15.8 and 18.3%, respectively. Also, there was an accumulation of SMFs without central nuclei. These data indicate a significanly increased efficacy of cell therapy in the case of additional exposition in Ca(2+)-MF. Thus, the efficiency of bone marrow transplantation mdx mice after both in doses 3 and 5 Gy was considerably enhanced by additional exposition to Ca(2+)-MF. Apparently, such magnetic field can intensify functioning of donor's nuclei which had been incorporated into muscle fibers.

Light Inhibition of Shoot Regeneration Is Regulated by Endogenous Abscisic Acid Level in Calli Derived from Immature Barley Embryos

Shoot regeneration in calli derived from immature barley embryos is regulated by light conditions during the callus-induction period. Barley cultivars Kanto Nijo-5 (KN5) and K-3 (K3) showed lower efficiency of shoot regeneration in a 16-h photoperiod during callus-induction than those in continuous darkness, whereas shoot regeneration was enhanced in cultures under a 16-h photoperiod in Golden Promise (GP) and Lenins (LN). These cultivars were classified as photo-inhibition type (KN5 and K3) or photo-induction type (GP and LN) according to their response to light. Contents of endogenous plant hormones were determined in calli cultured under a 16-h photoperiod and continuous darkness. In photo-inhibition type, higher accumulation of abscisic acid (ABA) was detected in calli cultured under a 16-h photoperiod, whereas calli showed lower levels of endogenous ABA in continuous darkness. However, cultivars of photo-induction type showed lower levels of ABA in calli cultured under both light conditions, similarly to photo-inhibition type in continuous darkness. Exogenous ABA inhibited the callus growth and shoot regeneration independent of light conditions in all cultivars. In photo-inhibition type, lower levels of endogenous ABA induced by ABA biosynthesis inhibitor, fluridone, reduced the photo-inhibition of shoot regeneration. Expression of ABA biosynthesis gene, HvNCED1, in calli was regulated by the light conditions. Higher expression was observed in calli cultured under a 16-h photoperiod. These results indicate that ABA biosynthesis could be activated through the higher expression of HvNCED1 in a 16-h photoperiod and that the higher accumulations of ABA inhibit shoot regeneration in the photo-inhibition type cultivars.

Simulation of Low-Intensity Ultrasound Propagating in a Beagle Dog Dentoalveolar Structure to Investigate the Relations between Ultrasonic Parameters and Cementum Regeneration

The therapeutic effect of low-intensity pulsed ultrasound on orthodontically induced inflammatory root resorption is believed to be brought about through mechanical signals induced by the low-intensity pulsed ultrasound. However, the stimulatory mechanism triggering dental cell response has not been clearly identified yet. The aim of this study was to evaluate possible relations between the amounts of new cementum regeneration and ultrasonic parameters such as pressure amplitude and time-averaged energy density. We used the finite-element method to simulate the previously published experiment on ultrasonic wave propagation in the dentoalveolar structure of beagle dogs. Qualitative relations between the thickness of the regenerated cementum in the experiment and the ultrasonic parameters were observed. Our results indicated that the areas of the root surface with greater ultrasonic pressure were associated with larger amounts of cementum regeneration. However, the establishment of reliable quantitative correlations between ultrasound parameters and cementum regeneration requires more experimental data and simulations.

Similar ex vivo expansion and post-irradiation regenerative potential of juvenile and aged salivary gland stem cells

BACKGROUND AND PURPOSE

Salivary gland dysfunction is a major side effect of radiotherapy for head and neck cancer patients, which in the future might be salvaged by autologous adult salivary gland stem cell (SGSC) therapy. Since frail elderly patients may have decreased activity of SGSCs, we aimed to characterize the potential of aged SGSC-population in a murine model.

MATERIALS AND METHODS

Salivary glands and salisphere-derived cells from young and old mice were tested for CD24 and CD29 stem cell marker expression using FACS. Moreover, in vitro expansion capability and in vivo regeneration potential upon post-irradiation transplantation of young and aged SGSCs were measured.

RESULTS

An increase in CD24(hi)/CD29(hi) putative stem cells was detected in aged salivary glands albeit with a decrease in functional ability to form salispheres. However, the salispheres formed from aged mice salivary glands expressed CD24(hi)/CD29(hi) to the same extent as the ones from young mice. Moreover, following exposure to adequate growth conditions old and young SGSCs exhibited similar in vitro expansion- and in vivo regeneration potential.

CONCLUSIONS

Aged SGSCs although reduced in number are in vitro indistinguishable from young SGSCs and could potentially be used to ameliorate age- or treatment related salivary gland dysfunction.

Low-Level Laser Therapy (LLLT) in Dystrophin-Deficient Muscle Cells: Effects on Regeneration Capacity, Inflammation Response and Oxidative Stress

The present study evaluated low-level laser therapy (LLLT) effects on some physiological pathways that may lead to muscle damage or regeneration capacity in dystrophin-deficient muscle cells of mdx mice, the experimental model of Duchenne muscular dystrophy (DMD). Primary cultures of mdx skeletal muscle cells were irradiated only one time with laser and analyzed after 24 and 48 hours. The LLLT parameter used was 830 nm wavelengths at 5 J/cm² fluence. The following groups were set up: Ctrl (untreated C57BL/10 primary muscle cells), mdx (untreated mdx primary muscle cells), mdx LA 24 (mdx primary muscle cells - LLLT irradiated and analyzed after 24 h), and mdx LA 48 (mdx primary muscle cells - LLLT irradiated and analyzed after 48 h). The mdx LA 24 and mdx LA 48 groups showed significant increase in cell proliferation, higher diameter in muscle cells and decreased MyoD levels compared to the mdx group. The mdx LA 48 group showed significant increase in Myosin Heavy Chain levels compared to the untreated mdx and mdx LA 24 groups. The mdx LA 24 and mdx LA 48 groups showed significant increase in [Ca2+]i. The mdx group showed significant increase in H2O2 production and 4-HNE levels compared to the Ctrl group and LLLT treatment reduced this increase. GSH levels and GPx, GR and SOD activities increased in the mdx group. Laser treatment reduced the GSH levels and GR and SOD activities in dystrophic muscle cells. The mdx group showed significant increase in the TNF-α and NF-κB levels, which in turn was reduced by the LLLT treatment. Together, these results suggest that the laser treatment improved regenerative capacity and decreased inflammatory response and oxidative stress in dystrophic muscle cells, indicating that LLLT could be a helpful alternative therapy to be associated with other treatment for dystrophinopathies.

Dietary supplement enriched in antioxidants and omega-3 protects from progressive light-induced retinal degeneration

In the present study, we have evaluated one of the dietary supplements enriched with antioxidants and fish oil used in clinical care for patient with age-related macular degeneration. Rats were orally fed by a gastric canula daily with 0.2 ml of water or dietary supplement until they were sacrificed. After one week of treatment, animals were either sacrificed for lipid analysis in plasma and retina, or used for evaluation of rod-response recovery by electroretinography (ERG) followed by their sacrifice to measure rhodopsin content, or used for progressive light-induced retinal degeneration (PLIRD). For PLIRD, animals were transferred to bright cyclic light for one week. Retinal damage was quantified by ERG, histology and detection of apoptotic nuclei. Animals kept in dim-cyclic-light were processed in parallel. PLIRD induced a thinning of the outer nuclear layer and a reduction of the b-wave amplitude of the ERG in the water group. Retinal structure and function were preserved in supplemented animals. Supplement induced a significant increase in omega-3 fatty acids in plasma by 168% for eicosapentaenoic acid (EPA), 142% for docosapentaenoic acid (DPA) and 19% for docosahexaenoic acid (DHA) and a decrease in the omega-6 fatty acids, DPA by 28%. In the retina, supplement induced significant reduction of linolenic acid by 67% and an increase in EPA and DPA by 80% and 72%, respectively, associated with significant decrease in omega-6 DPA by 42%. Supplement did not affect rhodopsin content or rod-response recovery. The present data indicate that supplement rapidly modified the fatty acid content and induced an accumulation of EPA in the retina without affecting rhodopsin content or recovery. In addition, it protected the retina from oxidative stress induced by light. Therefore, this supplement might be beneficial to slow down progression of certain retinal degeneration.

[Age-related peculiarities of thymus reaction to the exposure to helium-neon laser and injured muscle alloplasty with the muscle tissue from the animals of the same age]

Histological, cytological and morphometric changes in the thymus of 1 month-old, adult (3-4 months-old) and old (24-30 months-old) rats (24 animals in each group) were studied during muscle regeneration after the alloplasty of the injured area with the muscle tissue from the animal of the same age. Muscles of the donor or recipient were subjected to the course of preliminary irradiation with He-Ne laser (dose: 4.5-5.4 J/cm2 for each extremity; total dose of 9.0-10.8 J/cm2 per animal). It was shown that the exposure of gastrocnemius muscles that were prepared for the operation to He-Ne laser radiation decreased morpho-functional activity of the thymus in young, adult and old recipient rats the before surgery. This was demonstrated by its weaker reaction to the allograft during the early time intervals after surgery. The observed effect was more pronounced with the increasing age of an animal.

[On the issue of non-mutagenic non-targeted effects in low renewable tissues. Analysis of low dose radiation effects on the rat renal tubule epithelium]

Irradiation of rats with γ-quanta at relatively low doses induces a sustainable dose-independent increase in the occurrence of lethal cytoplasmic disorders in the renal tubules epithelium together with sustainable and as well dose-independent subcelluar compensation and restorative processes. Over the period of research (6 months) these processes led to no population recovery. The detected alterations are referred to the category of non-targeted non-mutagenic effects and they are of interest because they address the issue of the sensitivity of low renewable tissues to radiation.

Optimization and regeneration kinetics of lymphatic-specific photodynamic therapy in the mouse dermis

Lymphatic vessels transport fluid, antigens, and immune cells to the lymph nodes to orchestrate adaptive immunity and maintain peripheral tolerance. Lymphangiogenesis has been associated with inflammation, cancer metastasis, autoimmunity, tolerance and transplant rejection, and thus, targeted lymphatic ablation is a potential therapeutic strategy for treating or preventing such events. Here we define conditions that lead to specific and local closure of the lymphatic vasculature using photodynamic therapy (PDT). Lymphatic-specific PDT was performed by irradiation of the photosensitizer verteporfin that effectively accumulates within collecting lymphatic vessels after local intradermal injection. We found that anti-lymphatic PDT induced necrosis of endothelial cells and pericytes, which preceded the functional occlusion of lymphatic collectors. This was specific to lymphatic vessels at low verteporfin dose, while higher doses also affected local blood vessels. In contrast, light dose (fluence) did not affect blood vessel perfusion, but did affect regeneration time of occluded lymphatic vessels. Lymphatic vessels eventually regenerated by recanalization of blocked collectors, with a characteristic hyperplasia of peri-lymphatic smooth muscle cells. The restoration of lymphatic function occurred with minimal remodeling of non-lymphatic tissue. Thus, anti-lymphatic PDT allows control of lymphatic ablation and regeneration by alteration of light fluence and photosensitizer dose.

Physiology and growth of advance Picea rubens and Abies balsamea regeneration following different canopy openings

We examined the ecophysiology and growth of 0.3-1.3 m tall advance red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea [L.] Mill.) regeneration during a 5-year period following the application of different harvest types producing three sizes of canopy openings: (i) small gaps (<100 m(2) in area; SMA) created by partial uniform single-tree harvest; (ii) irregular gaps of intermediate size (100-300 m(2); INT) created by group-selection harvest (removal of groups of trees, mainly balsam fir, with uniform partial removal between groups); and (iii) large circular gaps (700 m(2); LAR) created by patch-selection harvest (removal of trees in 30-m diameter circular areas with uniform partial removal between gaps). An unharvested control (CON) was monitored for comparison. At the ecophysiological level, we mainly found differences in light-saturated photosynthesis of red spruce and specific leaf area of balsam fir among treatments. Consequently, we observed good height growth of both species in CON and INT, but fir surpassed spruce in SMA and LAR. Results suggest that intermediate 100-300 m(2) irregular openings create microenvironmental conditions that may promote short-term ecophysiology and growth of red spruce, allowing the species to compete with balsam fir advance regeneration. Finally, results observed for spruce in large 700-m(2) openings confirm its inability to grow as rapidly as fir in comparable open conditions.

Lgr5+ stem cells are indispensable for radiation-induced intestinal regeneration

The intestinal epithelium continually self-renews and can rapidly regenerate after damage. Lgr5 marks mitotically active intestinal stem cells (ISCs). Importantly, intestinal homeostasis can be maintained after depletion of Lgr5(+) cells due to the activation of Lgr5(-) reserve ISCs. The Lgr5(-) ISC populations are thought to play a similar role during intestinal regeneration following radiation-induced damage. We tested this regeneration hypothesis by combining depletion of Lgr5(+) ISCs with radiation exposure. In contrast to the negligible effect of Lgr5(+) ISC loss during homeostasis, depletion of Lgr5(+) cells during radiation-induced damage and subsequent repair caused catastrophic crypt loss and deterioration of crypt-villus architecture. Interestingly though, we found that crypts deficient for Lgr5(+) cells are competent to undergo hyperplasia upon loss of Apc. These data argue that Lgr5(-) reserve stem cells are radiosensitive and that Lgr5(+) cells are crucial for robust intestinal regeneration following radiation exposure but are dispensable for premalignant hyperproliferation.

[Dynamics of T-Cell receptor gene rearrangement and T-lymphocytes migration from thymus during post-radiation regeneration]

Recovery and migration of T-cells from the thymus to the secondary lymphoid organs in mice after sublethal gamma irradiation were investigated by measuring T-cell receptor excision circles (TRECs). The TRECs level practically represents the cellularity of thymus, in particular it correlates with the quantity of T-cells which have rearranged TCR genes and express the receptor complex CD3-TCR. So, TRECs can be considered as one of the markers of these cells. TREC-containing cells form a subset of recent thymic emigrants in the secondary lymphoid organs. After a significant TREC decrease in the lymph nodes within the early phase (4 days) after irradiation, we registered the increase of their number during urgent organ recovery due to T-cell migration from the thymus (the maximum is on the 10th day). The secondary thymic atrophy is accompanied by a weakening migration of the T-cells containing TRECs to lymph nodes. A significant TREC increase in the spleen was registered on the 4th day after irradiation. The rest of the recovery period. (up to 60 days) is characterized by the low TREC level. Thus, determination of TREC level allows obtaining additional information about recovery and migratory processes in lymphoid organs during post-radiation regeneration.

Light and competition gradients fail to explain the coexistence of shade-tolerant Fagus sylvatica and shade-intermediate Quercus petraea seedlings

BACKGROUND AND AIMS

The coexistence of forest tree species has often been linked to differences among species in terms of their response to light availability during the regeneration stage. From this perspective, species coexistence results from growth-growth or mortality-growth trade-offs along spatial light gradients. Experimental evidence of growth-growth trade-offs in natural conditions is sparse due to various confounding factors that potentially hinder the relationship. This study examined growth hierarchies along light gradients between two tree species with contrasting shade tolerance by controlling potential confounding factors such as seedling size, seedling status, seedling density and species composition.

METHODS

Natural regenerated shade-tolerant Fagus sylvatica and shade-intermediate Quercus petraea seedlings were used, and growth rankings over a 4-year period were compared in 8- to 10-year-old tree seedlings.

KEY RESULTS

No rank reversal occurs between the two species along the light gradient, or along the density, mixture or seedling size gradients. The shade-tolerant species was always the more competitive of the two. Pronounced effects of initial size on seedling growth were observed, whereas the effects of light and competition by neighbours were of secondary importance. The paramount effect of size, which results from the asymmetric nature of interseedling competition, gives a strong advantage to tall seedlings over the long term.

CONCLUSIONS

This study extends previous efforts to identify potential drivers of rank reversals in young tree mixtures. It does not support the classical assumption that spatial heterogeneity in canopy opening explains the coexistence of the two species studied. It suggests that spatial variation in local size hierarchies among seedlings that may be caused by seedling emergence time or seedling initial performance is the main driver of the dynamics of these mixed stands.

Induction of intestinal stem cells by R-spondin 1 and Slit2 augments chemoradioprotection

Cancer research has been rightly and successfully focused on prevention, early detection, and identification of specific molecular targets that distinguish the malignant cells from the neighbouring benign cells. However, reducing lethal tissue injury caused by intensive chemoradiotherapy during treatment of late-stage metastatic cancers remains a key clinical challenge. Here we tested whether the induction of adult stem cells could repair chemoradiation-induced tissue injury and prolong overall survival in mice. We found that intestinal stem cells (ISCs) expressed Slit2 and its single-span transmembrane cell-surface receptor roundabout 1 (Robo1). Partial genetic deletion of Robo1 decreased ISC numbers and caused villus hypotrophy, whereas a Slit2 transgene increased ISC numbers and triggered villus hypertrophy. During lethal dosages of chemoradiation, administering a short pulse of R-spondin 1 (Rspo1; a Wnt agonist) plus Slit2 reduced ISC loss, mitigated gut impairment and protected animals from death, without concomitantly decreasing tumour sensitivity to chemotherapy. Therefore Rspo1 and Slit2 may act as therapeutic adjuvants to enhance host tolerance to aggressive chemoradiotherapy for eradicating metastatic cancers.

γ irradiation with different dose rates induces different DNA damage responses in Petunia x hybrida cells

In plants, there is evidence that different dose rate exposures to gamma (γ) rays can cause different biological effects. The dynamics of DNA damage accumulation and molecular mechanisms that regulate recovery from radiation injury as a function of dose rate are poorly explored. To highlight dose-rate dependent differences in DNA damage, single cell gel electrophoresis was carried out on regenerating Petunia x hybrida leaf discs exposed to LDR (total dose 50 Gy, delivered at 0.33 Gy min(-1)) and HDR (total doses 50 and 100 Gy, delivered at 5.15 Gy min(-1)) γ-ray in the 0-24h time period after treatments. Significant fluctuations of double strand breaks and different repair capacities were observed between treatments in the 0-4h time period following irradiation. Dose-rate-dependent changes in the expression of the PhMT2 and PhAPX genes encoding a type 2 metallothionein and the cytosolic isoform of ascorbate peroxidase, respectively, were detected by Quantitative RealTime-Polymerase Chain Reaction. The PhMT2 and PhAPX genes were significantly up-regulated (3.0- and 0.7-fold) in response to HDR. The results are discussed in light of the potential practical applications of LDR-based treatments in mutation breeding.

Donor hematopoietic stem cells confer long-term marrow reconstitution by self-renewal divisions exceeding to that of host cells

Dormant hematopoietic stem cells (HSCs) are activated by microenvironmental cues of the niche in response to the injury of bone marrow (BM). It is not clearly understood how engrafted cells respond to these cues and are involved in marrow regeneration. The purpose of this study was to decipher this cellular response in competitive environment. BM cells of CD45.2 mice were transplanted in sub-lethally irradiated CD45.1 mice. The status of the donor and recipient stem cells (LSK: Lin⁻Sca-1⁺c-Kit⁺) were determined by flowcytometry using CD45 alleles specific antibodies. The presence of long-term engraftable stem cells was confirmed by marrow repopulation assay in secondary hosts, and cell cycle status was determined by staining with Ho33342 and pyronin Y, and BrdU retention assay. The expressions of different hematopoietic growth factor genes in stromal compartment (CD45⁻ cells) were assessed by real-time reverse transcriptase- polymerase chain reaction (RT-PCR). The presence of donor cells initially stimulated the proliferation of host LSK cells compared with control mice without transplantation. This was expected due to pro-mitotic and anti-apoptotic factors secreted by the donor hematopoietic cells. Upon transplantation, a majority of the donor LSK cells entered into cell cycle, and later they maintained cell cycle status similar to that in the normal mouse. Donor-derived LSK cells showed 1000-fold expansion within 15 days of transplantation. Donor-derived cells not only regenerated BM in the primary irradiated host for long-term, they were also found to be significantly involved in marrow regeneration after the second cycle of irradiation. The proliferation of LSK cells was associated with the onset of colossal expression of different hematopoietic growth factor genes in non-hematopoietic cellular compartment. Activation of donor LSK cells was found to be dynamically controlled by BM cellularity. Long-term study showed that a high level of hematopoietic reconstitution could be possible by donor cells in a sub-lethally irradiated host.

Transition pattern and mechanism of B-lymphocyte precursors in regenerated mouse bone marrow after subtotal body irradiation

Little is known about the effects of ionizing radiation on the transition and the related signal transduction of progenitor B cells in the bone marrow. Thus, using an NIH Swiss mouse model, we explored the impact of ionizing radiation on the early stage of B-cell development via an examination of the transition of CLP to pro-B to pre-B cells within bone marrow as a function of radiation doses and times. Our results showed that while the total number of bone marrow lymphoid cells at different stages were greatly reduced by subtotal body irradiation (sub-TBI), the surviving cells continued to transition from common lymphoid progenitors to pro-B and then to pre-B in a reproducible temporal pattern. The rearrangement of the immunoglobulin heavy chain increased significantly 1-2 weeks after irradiation, but no change occurred after 3-4 weeks. The rearrangement of the immunoglobulin light chain decreased significantly 1-2 weeks after sub-TBI but increased dramatically after 3-4 weeks. In addition, several key transcription factors and signaling pathways were involved in B-precursor transitions after sub-TBI. The data indicate that week 2 after irradiation is a critical time for the transition from pro-B cells to pre-B cells, reflecting that the functional processes for different B-cell stages are well preserved even after high-dose irradiation.

Murine P-glycoprotein deficiency alters intestinal injury repair and blunts lipopolysaccharide-induced radioprotection

P-glycoprotein (P-gp) has been reported to increase stem cell proliferation and regulate apoptosis. Absence of P-gp results in decreased repair of intestinal epithelial cells after chemical injury. To further explore the mechanisms involved in the effects of P-gp on intestinal injury and repair, we used the well-characterized radiation injury model. In this model, injury repair is mediated by production of prostaglandins (PGE(2)) and lipopolysaccharide (LPS) has been shown to confer radioprotection. B6.mdr1a(-/-) mice and wild-type controls were subjected to 12 Gy total body X-ray irradiation and surviving crypts in the proximal jejunum and distal colon were evaluated 3.5 days after irradiation. B6.mdr1a(-/-) mice exhibited normal baseline stem cell proliferation and COX dependent crypt regeneration after irradiation. However, radiation induced apoptosis was increased and LPS-induced radioprotection was blunted in the C57BL6.mdr1a(-/-) distal colon, compared to B6 wild-type controls. The LPS treatment induced gene expression of the radioprotective cytokine IL-1α, in B6 wild-type controls but not in B6.mdr1a(-/-) animals. Lipopolysaccharid-induced radioprotection was absent in IL-1R1(-/-) animals, indicating a role for IL-1α in radioprotection, and demonstrating that P-gp deficiency interferes with IL-1α gene expression in response to systemic exposure to LPS.

[Structural architectonics of apical root meristems in coherence with the quantitative assessment of its damage by radiation]

The dose dependencies of the aberrant anaphases frequency in the root meristem in 48 hours after irradiation in the range of doses of 4-10 Gy is characterized by threshold and plateau at 33% aberrant anaphase. The plateau indicates the activation of the recovery processes. Topology of cell rows in the primary meristem of the dose to 8 Gy are conserved and recovered damages. New cell rows are formed by local cell pools in the distal meristem, pericycle cells and subepidermy. It grows by intrusive character displacing the rows of damaged cells. Apparently the competition between clones of normal and aberrant cells plays the primary role in the mechanisms of recovery. Resulting to competition the promotion of aberrant cells to the extension zone is slowed down or blocked. So critical level of damage of the root apical meristem was defined about 50% of aberrant anaphase. Exceeding of this level leads to lethal consequence for meristem and it is accompanied by the inclusion of more radical process of restoration through regeneration. Regeneration leads to complete replacement of the apex tissues including the extension zone.

Using the Tg(nrd:egfp)/albino zebrafish line to characterize in vivo expression of neurod

In this study, we used a newly-created transgenic zebrafish, Tg(nrd:egfp)/albino, to further characterize the expression of neurod in the developing and adult retina and to determine neurod expression during adult photoreceptor regeneration. We also provide observations regarding the expression of neurod in a variety of other tissues. In this line, EGFP is found in cells of the developing and adult retina, pineal gland, cerebellum, olfactory bulbs, midbrain, hindbrain, neural tube, lateral line, inner ear, pancreas, gut, and fin. Using immunohistochemistry and in situ hybridization, we compare the expression of the nrd:egfp transgene to that of endogenous neurod and to known retinal cell types. Consistent with previous data based on in situ hybridizations, we show that during retinal development, the nrd:egfp transgene is not expressed in proliferating retinal neuroepithelium, and is expressed in a subset of retinal neurons. In contrast to previous studies, nrd:egfp is gradually re-expressed in all rod photoreceptors. During photoreceptor regeneration in adult zebrafish, in situ hybridization reveals that neurod is not expressed in Müller glial-derived neuronal progenitors, but is expressed in photoreceptor progenitors as they migrate to the outer nuclear layer and differentiate into new rod photoreceptors. During photoreceptor regeneration, expression of the nrd:egfp matches that of neurod. We conclude that Tg(nrd:egfp)/albino is a good representation of endogenous neurod expression, is a useful tool to visualize neurod expression in a variety of tissues and will aid investigating the fundamental processes that govern photoreceptor regeneration in adults.

Gynogenesis in gentians (Gentiana triflora, G. scabra): production of haploids and doubled haploids

Gynogenesis was investigated on gentian (Gentiana triflora, G. scabra and their hybrids), which is an important ornamental flower. When unfertilized ovules were cultured in 1/2 NLN medium containing a high concentration of sucrose (100 g/l), embryo-like structures (ELS) were induced. Although genotypic variation was observed in ELS induction, all four genotypes produced ELSs ranging from 0.93 to 0.04 ELSs per flower bud. The ovules collected from flower buds of later stages (just before anthesis or flower anthesis) tended to exhibit higher response. The dark culture condition produced more than four times as many ELSs than in 16-h light condition. A significant number of plantlets were directly regenerated from ELSs on MS regeneration medium. The ploidy levels of 179 regenerated plants were determined by flow cytometry, revealing that the majority of them were diploid (55.9%) and haploid (31.3%). When a total of 54 diploid plants were examined by molecular genetic markers, 52 (96.3%) were considered as doubled haploids (DHs). This is the first report showing successful gynogenesis in gentian. The production of haploids and DHs by unfertilized ovule culture opens a novel prospect in gentian F1 hybrid breeding.

No effect of low-level lasers on in vitro myoblast culture

Effects of phototherapy using low-level lasers depend on irradiation parameters and the type of laser used. The aim of the present study was to evaluate the effect of phototherapy on the proliferation of cultured C2C12 myoblasts under different nutritional conditions using low-level GaAlAs and InGaAlP lasers with different parameters and incubation periods. C2C12 cells cultured in regular and nutrient-deficient medium were irradiated with low-level GaAlAs (780 nm) and InGaA1P (660 nm) lasers with energy densities of 3.8, 6.3 and 10 J/cm2, and 3.8, 10 and 17.5 J/cm2, respectively. Cell proliferation was assessed 48 and 72 h after irradiation by MTT assay. There were no significant differences in cell proliferation between laser-treated myoblasts and control cultures for any of the parameters and incubation periods. Further studies are necessary to determine the correct laser parameters for optimizing the biostirhulation of myoblasts.

GATA3 expression is decreased in psoriasis and during epidermal regeneration; induction by narrow-band UVB and IL-4

Psoriasis is characterized by hyperproliferation of keratinocytes and by infiltration of activated Th1 and Th17 cells in the (epi)dermis. By expression microarray, we previously found the GATA3 transcription factor significantly downregulated in lesional psoriatic skin. Since GATA3 serves as a key switch in both epidermal and T helper cell differentiation, we investigated its function in psoriasis. Because psoriatic skin inflammation shares many characteristics of epidermal regeneration during wound healing, we also studied GATA3 expression under such conditions.

Psoriatic lesional skin showed decreased GATA3 mRNA and protein expression compared to non-lesional skin. GATA3 expression was also markedly decreased in inflamed skin of mice with a psoriasiform dermatitis induced with imiquimod. Tape-stripping of non-lesional skin of patients with psoriasis, a standardized psoriasis-triggering and skin regeneration-inducing technique, reduced the expression of GATA3. In wounded skin of mice, low GATA3 mRNA and protein expression was detected. Taken together, GATA3 expression is downregulated under regenerative and inflammatory hyperproliferative skin conditions. GATA3 expression could be re-induced by successful narrow-band UVB treatment of both human psoriasis and imiquimod-induced psoriasiform dermatitis in mice. The prototypic Th2 cytokine IL-4 was the only cytokine capable of inducing GATA3 in skin explants from healthy donors. Based on these findings we argue that GATA3 serves as a key regulator in psoriatic inflammation, keratinocyte hyperproliferation and skin barrier dysfunction.

[Critical level of radiation damage of root apical meristem and mechanisms for its recovery in Pisum sativum L]

The dose dependencies of growth and cytogenetical values have been built to determine the critical level of root apical meristem damage induced by cute irradiation in the range from 2 to 20 Gr. We have analyzed the frequencies of aberrant anaphases and the aberration distribution per cell, on the one hand, and the growth of biomass, the survival and regeneration of the root meristem, on the other hand. The critical level of damage to the stem apical meristem and root of seedlings was defined as 44-48% of aberrant anaphase. Exceeding of this level leads to the launch of suicidal program through induction of multiaberrant damages and interphase cell death. It appears that competition of clones of non-aberrant cells, the cells bearing 1 and 2 damages and multiaberrant cells plays the primary role in the mechanisms of recovery. The regeneration provides full or partial restoration of the main root apical meristem. However these local processes are insufficient to restore morphogenesis and survival of seedlings in excess of the critical level damage.

[Tripeptide restorates structure of duodenum at accelerated aging]

Effect of tripeptide on the process of postradiational restoration of duodenum in rats has been studied in model of accelerated aging. Geroprotective effect of tripeptide was connected with reparation of bloodstream in duodenum and increase proliferative activity of duodenal epiteliocytes.

[Activation of reconstructive processes in rat tissues under the action of radiofrequency current with a periodic impulse mode of modulation]

The action of a current in the radio frequency range with a periodic impulse mode of modulation on the activation of recovery processes in the skin and skeletal muscles has been studied. The action of a radio frequency current with a power of 1 W, as opposed to that of the weaker action (0.1 W) and stronger (4 W) action, leads to the activation of recovery processes in the skin and skeletal muscles. Recovery processes are manifested in the increase in proliferation and activation of angiogenesis in the skin, and also in formation of new muscle fibers. Recovery processes in muscles are accompanied by activation and migration of satellite cells of muscle tissue in the zone of action of the radio frequency current.

[Muscle regeneration and the state of the thymus in adult rats under laser irradiation and alloplasty of the gastrocnemius muscles and diaphragm of newborn rats]

The regeneration of gastrocnemius muscles of adult rats under implantation conditions in areas of muscle tissue damage in newborn rats has been studied. Alloplasty was performed using minced gastrocnemius and diaphragm muscles, which differs at birth in animals by degree of differentiation. The rat-recipient area of alloplasty was subjected to He-Ne laser radiation before operation, with the aim of reducing the immune response to allogenic muscle tissue. It has been shown that the number of regenerating myofibers produced in implanted gastrocnemius muscles is more than in alloplants from diaphragms. However, the formation of cartilage, bone, and adipose tissue foci were observed in the alloplastic region throughout the whole regeneration period. After implantation of minced diaphragm muscles, cartilage nodes were observed only in 7-day regenerates. At the end of observation, in the first instance, the area of muscle trauma in adult rat muscles was replaced by adipose tissue, even in the case of initial laser irradiation. During the implantation of diaphragm muscles, the area of trauma was filled with regenerating muscle tissue.