Mesenchymal stem cell-based therapies for treating well-studied neurological disorders: a systematic review.

Background: Millions of people across the globe are affected by conditions like Amyotrophic Lateral Sclerosis (ALS), Parkinson's Disease (PD), Multiple Sclerosis (MS), Spinal Cord Injury (SCI), and Traumatic Brain Injury (TBI), although most occurrences are common in the elderly population. This systematic review aims to highlight the safety of the procedures, their tolerability, and efficacy of the available therapies conducted over the years using mesenchymal stem cells (MSCs) in treating the neurological conditions mentioned above. Methods: PubMed was used to search for published data from clinical trials performed using mesenchymal stem cells. Studies that provided the necessary information that mentioned the efficacy and adverse effects of the treatment in patients were considered for this review. Results: In total, 43 manuscripts were selected after a strategic search, and these studies have been included in this systematic review. Most included studies reported the safety of the procedures used and the treatment's good tolerability, with mild adverse events such as fever, headache, mild pain at the injection site, or nausea being common. A few studies also reported death of some patients, attributed to the progression of the disease to severe stages before the treatment. Other severe events, such as respiratory or urinary infections reported in some studies, were not related to the treatment. Different parameters were used to evaluate the efficacy of the treatment based on the clinical condition of the patient. Conclusion: Mesenchymal stem cells transplantation has so far proven to be safe and tolerable in select studies and patient types. This systematic review includes the results from the 43 selected studies in terms of safety and tolerability of the procedures, and several adverse events and therapeutic benefits during the follow-up period after administration of MSCs.

Local Glucocorticoid Administration Impairs Embryonic Wound Healing.

Understanding the complex processes of fetal wound healing and skin regeneration can help to improve fetal surgery. As part of the integumentary system, the skin protects the newborn organism against environmental factors and serves various functions. Glucocorticoids can enter the fetal circulatory system by either elevated maternal stress perception or through therapeutic administration and are known to affect adult skin composition and wound regeneration. In the present study, we aimed at investigating the effects of local glucocorticoid administration on the process of embryonic wound healing. We performed in-ovo bead implantation of dexamethasone beads into skin incisional wounds of avian embryos and observed the local effects of the glucocorticoid on the process of skin regeneration through histology, immunohistochemistry and in-situ hybridization, using vimentin, fibronectin, E-cadherin, Dermo-1 and phospho-Histone H3 as investigational markers. Local glucocorticoid administration decelerated the healing of the skin incisional wounds by impairing mesenchymal contraction and re-epithelialization resulting in morphological changes, such as increased epithelialization and disorganized matrix formation. The results contribute to a better understanding of scarless embryonic wound healing and how glucocorticoids might interfere with the underlying molecular processes, possibly indicating that glucocorticoid therapies in prenatal clinical practice should be carefully evaluated.

Zebrafish as an Orthotopic Tumor Model for Retinoblastoma Mimicking Routes of Human Metastasis.

BACKGROUND: Retinoblastoma (RB) is the most common eye cancer in children that has a high mortality rate when left untreated. Mouse models for retinoblastoma have been established but are time- and cost-intensive. The aim of this work was to evaluate an orthotopic transplantation model of retinoblastoma in zebrafish that also allows for tracking migratory routes and to explore advantages and disadvantages with respect to drug testing. METHODS: Three fluorescence-labeled retinoblastoma cell lines (RB355, WERI-RB-1, Y79) were injected into the left eye of two-day-old zebrafish, while the un-injected right eye served as control. The migratory trajectories of injected retinoblastoma cells were observed until 8 days post injection (dpi), both in lateral and dorsal view, and measuring fluorescence intensity of injected cells was done for RB355 cells. RESULTS: Time until the onset of migration and routes for all three retinoblastoma cell lines were comparable and resulted in migration into the brain and ventricles of the forebrain, midbrain and hindbrain. Involvement of the optic nerve was observed in 10% of injections with the RB355 cell line, 15% with Y79 cells and 5% with WERI-RB-1 cells. Fluorescence intensity of injected RB355 cells showed an initial increase until five dpi, but then decreased with high variability until the end of observation. CONCLUSION: The zebrafish eye is well suited for the analysis of migratory routes in retinoblastoma and closely mirrors patterns of retinoblastoma metastases in humans.

Atoh8 in Development and Disease.

Atoh8 belongs to a large superfamily of transcriptional regulators called basic helix-loop-helix (bHLH) proteins. bHLH proteins have been identified in a wide range of organisms from yeast to humans. The members of this special group of transcription factors were found to be involved not only in embryonic development but also in disease initiation and its progression. Given their importance in several fundamental processes, the translation, subcellular location and turnover of bHLH proteins is tightly regulated. Alterations in the expression of bHLH proteins have been associated with multiple diseases also in context with Atoh8 which seems to unfold its functions as both transcriptional activator and repressor. Like many other bHLH transcription factors, so far, Atoh8 has also been observed to be involved in both embryonic development and carcinogenesis where it mainly acts as tumor suppressor. This review summarizes our current understanding of Atoh8 structure, function and regulation and its complex and partially controversial involvement in development and disease.

Nano-sulforaphane attenuates PhIP-induced early abnormal embryonic neuro-development.

BACKGROUND: 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyrimidine (PhIP), one of the most abundant heterocyclic aromatic amines (HAA) formed by cooking meat at high temperatures, may modify humans and rodents through the metabolic process prior to affecting nervous system development. In humans and rodents may be modified by metabolic processes and then affecting nervous system development. METHODS: In this paper, PhIP was used to prepare a chicken embryo model with abnormal embryonic nervous system defects. Sulforaphane (SFN) is a derivative of a glucosinolate, which is abundant in cruciferous vegetables, and can pass through the placental barrier. Moreover, SFN has antioxidant and anti-apoptotic functions and is considered as a bioactive antioxidant with significant neuroprotective effects. Nano-sulforaphane (Nano-SFN, sulforaphane nanoparticles) was prepared by self-assembly using biocompatible, biodegradable methoxy polyethylene glycol 5000-b-polyglutamic acid 10,000 (mPEG5K-PGA10K) as the substrate, to explore the new application of Nano-SFN and its modified compounds as leading compounds in protecting against the abnormal development of the embryonic nervous system. RESULTS: The results show that Nano-SFN could protect against PhIP-induced central nervous system (CNS, derived from neural tube) and peripheral nervous system (PNS, derived from neural crest cells, NCCs) defects and neural tube defects (NTDs), and increase the embryo survival rate. CONCLUSIONS: This study indicates that Nano-SFN can effectively alleviate the developmental defects of embryonic nervous system induced by PhIP in the microenvironment and has a protective effect on embryonic development. It not only helps with expanding the application of SFN and improving its medicinal value, but also provides a possibility of SFN being developed as a novel drug for neuroprotection.

Zinc oxide nanoparticles exposure-induced oxidative stress restricts cranial neural crest development during chicken embryogenesis.

Zinc oxide Nanoparticles (ZnO NPs) are widely used as emerging materials in agricultural and food-related fields, which exists potential safety hazards to public health and environment while bringing an added level of convenience to our original life. It has been proved that ZnO NPs could be taken up by pregnant women and passed through human placental barrier. However, the toxic potential for embryo development remains largely unanswered. In this study, we discovered that ZnO NPs caused the cytotoxicity in vitro. Inhibition of free Zn2+ ions in solution by EDTA or inhibition of Zn2+ ions absorption by CaCl2 could partially eliminate ZnO NPs-mediated cell toxicity, though not redeem completely. This indicated that both nanoparticles and the release of Zn2+ ions were involved in ZnO NPs-mediated cytotoxicity. In addition, we also found that both nanoparticles and Zn2+ ion release triggered reactive oxygen species (ROS) production, which further induced cell toxicity, inflammation and apoptosis, which are mediated by NF-κB signaling cascades and the mitochondria dysfunction, respectively. Eventually, these events lead to the suppressed production and migration of cranial neural crest cells (CNCCs), which subsequently prompts the craniofacial defects in chicken embryos. The application of the antioxidant N-Acetyl-L-cysteine (NAC) rescued the ZnO NPs-induced cell toxicity and malformation of the CNCCs, which further verified our hypothesis. Our results revealed the relevant mechanism of ZnO NPs exposure-inhibited the development of CNCCs, which absolutely contribute to assess the risk of nanoparticles application.

bHLH Transcription Factor Math6 Antagonizes TGF-ß Signalling in Reprogramming, Pluripotency and Early Cell Fate Decisions.

The basic helix-loop-helix (bHLH) transcription factor Math6 (Atonal homolog 8; Atoh8) plays a crucial role in a number of cellular processes during embryonic development, iron metabolism and tumorigenesis. We report here on its involvement in cellular reprogramming from fibroblasts to induced pluripotent stem cells, in the maintenance of pluripotency and in early fate decisions during murine development. Loss of Math6 disrupts mesenchymal-to-epithelial transition during reprogramming and primes pluripotent stem cells towards the mesendodermal fate. Math6 can thus be considered a regulator of reprogramming and pluripotent stem cell fate. Additionally, our results demonstrate the involvement of Math6 in SMAD-dependent TGF beta signalling. We furthermore monitor the presence of the Math6 protein during these developmental processes using a newly generated Math6Flag-tag mouse. Taken together, our results suggest that Math6 counteracts TGF beta signalling and, by this, affects the initiating step of cellular reprogramming, as well as the maintenance of pluripotency and early differentiation.

Cell survival controlled by lens-derived Sema3A-Nrp1 is vital on caffeine-suppressed corneal innervation during chick organogenesis.

In this study, we investigated the effect of caffeine overexposure on corneal innervation in the early chicken embryo. Caffeine administration restricted corneal innervation by affecting trigeminal nerve development. Immunohistochemistry for phospho-Histone3 (pHIS3) and C-caspase3 revealed that cell survival was repressed by caffeine administration. Whole-mount in situ hybridization against semaphorin 3A (Sema3A) and neuropilin-1 (Nrp1) showed that both caffeine and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH, a free radical generator) administration upregulates the expression of both Sema3A and Nrp1. Next, we demonstrated that lens ablation in the developing chicken embryos significantly affected NF-labeled periocular nerve fascicles and innervation to the central eye region. Subsequently, we used a neuroblastoma cell line to investigate in vitro whether or not Sema3A-Nrp1 signaling exerts a key role on the caffeine-suppressed neuron survival. Knocking-down Sema3A through transfection with Sema3A-siRNA dramatically decreased the responsiveness of cells to caffeine administration, as well as cell apoptosis. We suggest that Sema3A-Nrp1 signaling regulates Trp53 and Cdkn1a through Slit2-Robo1 and Ephb2. Taken together, we speculate here that caffeine-enhanced reactive oxygen species upregulates Sema3A-Nrp1 expression in the lens and periocular tissues, resulting in corneal cell apoptosis, accompanied by its chemorepellent role on the invasion of the developing cornea by trigeminal sensory fibers.

The role of autophagy in morphogenesis and stem cell maintenance.

During embryonic development, cells need to undergo a number of morphological changes that are decisive for the shaping of the embryo's body, initiating organogenesis and differentiation into functional tissues. These remodeling processes are accompanied by profound changes in the cell membrane, the cytoskeleton, organelles, and extracellular matrix composition. While considerably detailed insight into the role of autophagy in stem cells biology has been gained in the recent years, information regarding the participation of autophagy in morphogenetic processes is only sparse. This review, therefore, focuses on the role of autophagy in cell morphogenesis through its regulatory activity in TGFß signaling, expression of adhesion molecules and cell cycle modification. It also discusses the role of autophagy in stem cell maintenance which is very fundamental for cell renewal and replacement during development, pathogenesis of certain diseases and development of therapies. We are thus addressing here perspectives for further potentially rewarding research topics.

Qualitative and Quantitative Analysis of Cardiac Progenitor Cells in Cases of Myocarditis and Cardiomyopathy.

We aimed to identify and quantify CD117+ and CD90+ endogenous cardiac progenitor cells (CPC) in human healthy and diseased hearts. We hypothesize that these cells perform a locally acting, contributing function in overcoming medical conditions of the heart by endogenous means. Human myocardium biopsies were obtained from 23 patients with the following diagnoses: Dilatative cardiomyopathy (DCM), ischemic cardiomyopathy (ICM), myocarditis, and controls from healthy cardiac patients. High-resolution scanning microscopy of the whole slide enabled a computer-based immunohistochemical quantification of CD117 and CD90. Those signals were evaluated by Definiens Tissue Phenomics® Technology. Co-localization of CD117 and CD90 was determined by analyzing comparable serial sections. CD117+/CD90+ cardiac cells were detected in all biopsies. The highest expression of CD90 was revealed in the myocarditis group. CD117 was significantly higher in all patient groups, compared to healthy specimens (*p < 0.05). The highest co-expression was found in the myocarditis group (6.75 ± 3.25 CD90+CD117+ cells/mm2) followed by ICM (4 ± 1.89 cells/mm2), DCM (1.67 ± 0.58 cells/mm2), and healthy specimens (1 ± 0.43 cells/mm2). We conclude that the human heart comprises a fraction of local CD117+ and CD90+ cells. We hypothesize that these cells are part of local endogenous progenitor cells due to the co-expression of CD90 and CD117. With novel digital image analysis technologies, a quantification of the CD117 and CD90 signals is available. Our experiments reveal an increase of CD117 and CD90 in patients with myocarditis.

GGNBP2 is necessary for testis morphology and sperm development.

Gametogenetin Binding Protein 2 (GGNBP2) was identified as a tumor suppressor and verified as such by several studies. GGNBP2 has also been reported to be essential for pregnancy maintenance via regulation of trophoblast stem cells. Gametogenetin (GGN) is a testicular germ cell-specific gene expressed in adult testes. As a potential GGN1-interacting protein, the role of GGNBP2 in spermatogenesis has not yet been clarified. We generated heterozygous GGNBP2 knockout mice and bred them by intercrossing. We found that among the offspring, homozygous GGNBP2 knockout (KO) mice were present in severely reduced numbers. The GGNBP2 KO pups developed normally, but the male siblings showed dramatically reduced fertility. In these male homozygous GGNBP2 KO mice, the only pathological finding was abnormal morphology of the testes and absence of spermatozoa. In addition, increased apoptosis was observed in the testes of GGNBP2 KO mice. SOX9 staining revealed that SOX9-positive Sertoli cells were absent in the seminiferous tubules. In homozygous mice, proliferating cell nuclear antigen (PCNA)-positive cells were localized in the lumen of the convoluted seminiferous tubules. These results suggest that GGNBP2 plays a key role in spermatogenesis by affecting the morphology and function of SOX9-positive Sertoli cells.

Thymosin ß4 overexpression regulates neuron production and spatial distribution in the developing avian optic tectum.

Thymosin ß4 (Tß4), the principal G-actin regulating entity in eukaryotic cells, has also multiple intra- and extracellular functions related to tissue regeneration and healing. While its effect in adult organs is being widely investigated, currently, little is known about its influence on embryonic tissues, i.e., in the developing nervous system. The importance of Tß4 for neural stem cell proliferation in the embryonic chicken optic tectum (OT) has previously been shown by us for the first time. In the present study, using in ovo electroporation, we carried out a quantification of the effects of the Tß4-overexpression on the developing chicken OT between E4 and E6 at the hemisphere as well as cellular level. We precisely examined tissue growth and characterized cells arising from the elevated mitotic activity of progenitor cells. By using spinning-disk confocal laser scanning microscopy, we were able to visualize these effects across whole OT sections. Our experiments now demonstrate more clearly that the overexpression of Tß4 leads to a tangential expansion of the treated OT-hemisphere and that, under these circumstances, overall density of tectal and in particular of postmitotic neuronal cells is increased. Thanks to this new quantitative approach, the present results extend our previous findings that Tß4 is important for the proliferation of progenitor cells, neurogenesis, tangential expansion, and tissue growth in the young embryonic chicken optic tectum. Taken together, our results further illustrate and support the current idea that Tß4 is widely implicated in shaping and maintenance of the nervous system.

Inflammation and neuronal death in the motor cortex of the wobbler mouse, an ALS animal model.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder of the upper and lower motor neurons, characterized by rapid progressive weakness, muscle atrophy, dysarthria, dysphagia, and dyspnea. Whereas the exact cause of ALS remains uncertain, the wobbler mouse (phenotype WR; genotype wr/wr) equally develops a progressive degeneration of motor neurons in the spinal cord and motor cortex with striking similarities to sporadic human ALS, suggesting the possibility of a common pathway to cell death. METHODS: With the aid of immunohistochemistry, confocal laser scanning microscopy, and transmission electron microscopy techniques, we analyze the proliferation behavior of microglial cells and astrocytes. We also investigate possible motor neuron death in the mouse motor cortex at different stages of the wobbler disease, which so far has not received much attention. RESULTS: An abnormal density of Iba-1-positive microglial cells expressing pro-inflammatory tumor necrosis factor (TNF) alpha- and glial fibrillary acidic protein (GFAP)-positive activated astroglial cells was detected in the motor cortex region of the WR mouse 40 days postnatal (d.p.n.). Motor neurons in the same area show caspase 3 activation indicating neurodegenerative processes, which may cause progressive paralysis of the WR mice. It could also cause cell degeneration, such as vacuolization, dilation of the ER, and swollen mitochondria at the same time, and support the assumption that inflammation might be an important contributing factor of motor neuron degeneration. This would appear to be confirmed by the fact that there was no conspicuous increase of microglial cells and astrocytes in the motor cortex of control mice at any time. CONCLUSIONS: Activated microglial cells secrete a variety of pro-inflammatory and neurotoxic factors, such as TNF alpha, which could initiate apoptotic processes in the affected wobbler motor neurons, as reflected by caspase 3 activation, and thus, the neuroinflammatory processes might influence or exacerbate the neurodegeneration. Although it remains to be clarified whether the immune response is primary or secondary and how harmful or beneficial it is in the WR motor neuron disease, anti-inflammatory treatment might be considered.

Regression of Gastric Cancer by Systemic Injection of RNA Nanoparticles Carrying both Ligand and siRNA.

Gastric cancer is the second leading cause of cancer-related death worldwide. RNA nanotechnology has recently emerged as an important field due to recent finding of its high thermodynamic stability, favorable and distinctive in vivo attributes. Here we reported the use of the thermostable three-way junction (3WJ) of bacteriophage phi29 motor pRNA to escort folic acid, a fluorescent image marker and BRCAA1 siRNA for targeting, imaging, delivery, gene silencing and regression of gastric cancer in animal models. In vitro assay revealed that the RNA nanoparticles specifically bind to gastric cancer cells, and knock-down the BRCAA1 gene. Apoptosis of gastric cancer cells was observed. Animal trials confirmed that these RNA nanoparticles could be used to image gastric cancer in vivo, while showing little accumulation in crucial organs and tissues. The volume of gastric tumors noticeably decreased during the course of treatment. No damage to important organs by RNA nanoparticles was detectible. All the results indicated that this novel RNA nanotechnology can overcome conventional cancer therapeutic limitations and opens new opportunities for specific delivery of therapeutics to stomach cancer without damaging normal cells and tissues, reduce the toxicity and side effect, improve the therapeutic effect, and exhibit great potential in clinical tumor therapy.

ATOH8: a novel marker in human muscle fiber regeneration.

Regenerating muscle fibers emerge from quiescent satellite cells, which differentiate into mature multinuclear myofibers upon activation. It has recently been found that ATOH8, a bHLH transcription factor, is regulated during myogenic differentiation. In this study, expression and localization of ATOH8, the other well-described regeneration markers, vimentin, nestin and neonatal myosin, and the satellite cell marker Pax7 were analyzed on protein level in human myopathy samples by immunofluorescence studies. On mRNA level, expression levels of ATOH8 and vimentin were studied by quantitative real-time PCR. ATOH8 is expressed in activated satellite cells and proliferating myoblasts of human skeletal muscle tissue. Quantitative analyses of ATOH8+, Pax7+, vimentin+, nestin+ and neonatal myosin+ muscle fibers showed the highest amount of regenerating muscle fibers in inflammatory myopathies, followed by muscular dystrophy. The relative co-expression of ATOH8 with the above-mentioned markers did not vary among the disorders. These results show that the novel regeneration marker ATOH8 contributes to muscle cell differentiation in healthy and diseased human muscle tissue.

New aspects of progesterone interactions with the actin cytoskeleton and neurosteroidogenesis in the cerebellum and the neuronal growth cone.

The impact of progesterone on neuronal tissues in the central (CNS) and peripheral (PNS) nervous system is of significant scientific and therapeutic interest. Glial and neuronal cells of vertebrates express steroidogenic enzymes, and are able to synthesize progesterone de novo from cholesterol. Progesterone is described to have neuroprotective, neuroreparative, anti-degenerative, and anti-apoptotic effects in the CNS and the PNS. Thus, the first clinical studies promise new therapeutic options using progesterone in the treatment of patients with traumatic brain injury. Additionally, experimental data from different animal models suggest further positive effects of progesterone on neurological diseases such as cerebral ischemia, peripheral nerve injury and amyothropic lateral sclerosis. In regard to this future clinical use of progesterone, we discuss in this review the underlying physiological principles of progesterone effects in neuronal tissues. Mechanisms leading to morphological reorganizations of neurons in the CNS and PNS affected by progesterone are addressed, with special focus on the actin cytoskeleton. Furthermore, new aspects of a progesterone-dependent regulation of neurosteroidogenesis mediated by the recently described progesterone binding protein PGRMC1 in the nervous system are discussed.

Retrograde migration of pectoral girdle muscle precursors depends on CXCR4/SDF-1 signaling.

In vertebrates, muscles of the pectoral girdle connect the forelimbs with the thorax. During development, the myogenic precursor cells migrate from the somites into the limb buds. Whereas most of the myogenic precursors remain in the limb bud to form the forelimb muscles, several cells migrate back toward the trunk to give rise to the superficial pectoral girdle muscles, such as the large pectoral muscle, the latissimus dorsi and the deltoid. Recently, this developing mode has been referred to as the "In-Out" mechanism. The present study focuses on the mechanisms of the "In-Out" migration during formation of the pectoral girdle muscles. Combining in ovo electroporation, tissue slice-cultures and confocal laser scanning microscopy, we visualize live in detail the retrograde migration of myogenic precursors from the forelimb bud into the trunk region by live imaging. Furthermore, we present for the first time evidence for the involvement of the chemokine receptor CXCR4 and its ligand SDF-1 during these processes. After microsurgical implantations of CXCR4 inhibitor beads in the proximal forelimb region of chicken embryos, we demonstrate with the aid of in situ hybridization and live-cell imaging that CXCR4/SDF-1 signaling is crucial for the retrograde migration of pectoral girdle muscle precursors. Moreover, we analyzed the MyoD expression in CXCR4-mutant mouse embryos and observed a considerable decrease in pectoral girdle musculature. We thus demonstrate the importance of the CXCR4/SDF-1 axis for the pectoral girdle muscle formation in avians and mammals.

Induction of neoplasia after deep anterior lamellar keratoplasty in a CXL-treated cornea.

PURPOSE: Corneal collagen crosslinking (CXL) with ultraviolet-A energy plus riboflavin has become a ubiquitous treatment in early keratoconus, although its long-term safety is unknown. We describe severe sequelae in a CXL-treated patient after he underwent a standard deep anterior lamellar keratoplasty procedure. METHODS: In April 2009, a healthy 49-year-old male patient (R.H.) underwent bilateral CXL according to the Dresden protocol for progressive keratoconus stage 3. The best-corrected visual acuity did not improve over 20/100 within a postoperative period of 2 years, and contact lenses were not tolerated. Consequently, a unilateral deep anterior lamellar keratoplasty was performed, to transplant an 8-mm fully epithelialized button onto an 8-mm bed with a bared Descemet membrane (surgeon: J.H.K.). RESULTS: The postoperative healing course was unusually disturbed. Sutures pulled through the recipient tissue, which required suture replacement. Portions of the epithelium sloughed off repeatedly, and bulky regrowth displayed no attachment to the Bowman membrane. Within the first weeks, the transplant became cloudy. Two biopsies were removed from the limbus area and submitted to independent histopathological laboratories, both of which diagnosed the condition as epithelial neoplasia. Pathology tests indicated conjunctival intraepithelial neoplasia, the preliminary stage of invasive squamous cell carcinoma, in the keratocyte-voided bed of the recipient. CONCLUSIONS: This case suggests that CXL might hamper the ocular healing process and, combined with subsequent corneal surgery, could potentially initiate neoplasia. Further investigation is warranted to determine the safety of the combination of ultraviolet-A/riboflavin treatment and subsequent corneal tissue transplantation.

A thymosin beta15-like peptide promotes intersegmental myotome extension in the chicken embryo.

Beta-thymosins constitute a group of small actin-sequestering peptides. These highly conserved peptides are involved in cytoskeleton dynamics and can influence different cell properties such as motility, substrate adhesion, shape and chemotaxis. As a marker for tumour metastasis, the mammalian thymosin beta15 is believed to have an important diagnostic relevance in cancer prognosis, although little is known about its physiological function. In order to study the role of thymosin beta15(avian) in embryogenesis, we cloned the chicken and quail orthologues of thymosin beta15 and used the chicken as a model for vertebrate development. Avian thymosin beta15, the first known non-mammalian thymosin beta15-like gene, encodes a peptide that possesses a cysteine at position one after the methionine which is a significant difference compared to its mammalian counterparts. Thymosin beta15(avian) expression starts at an early stage of development. The expression pattern changes rapidly with development and differs from that of the related thymosin beta4 gene. The most prominent expression domain is seen in developing muscles of limbs and trunk. Gain-of-function experiments revealed that thymosin beta15(avian) has a function in normal myotome development. Ectopic over-expression of thymosin beta15(avian) leads to premature elongation of myotome cells trespassing segment borders. We conclude that thymosin beta15(avian) has a still undescribed function in promoting myocyte elongation.

Trachea: anatomy and physiology.

The windpipe (trachea) is a tube of 12 cm length connecting the larynx to the principal bronchi that lead to the lungs. The main functions of the trachea comprise air flow into the lungs, mucociliary clearance, and humidification and warming of air. Mucociliary clearance is achieved by kinocilia and goblet cells in the mucosa, and by tracheal glands. The trachea develops from the endodermal lining of the foregut in interaction with the visceral mesoderm. During adult life, different types of stem cells reside in the mucosal epithelium and glandular ducts. Recently, cholinergic chemosensory cells have been described in the trachea.