Circadian clock in choroid plexus is resistant to immune challenge but dampens in response to chronodisruption

The choroid plexus (ChP) in the brain ventricles has a major influence on brain homeostasis. In this study, we aimed to determine whether the circadian clock located in ChP is affected by chronodisruption caused by misalignment with the external light/dark cycle and/or inflammation. Adult mPer2Luc mice were maintained in the LD12:12 cycle or exposed to one of two models of chronic chronodisruption - constant light for 22-25 weeks (cLL) or 6-hour phase advances of the LD12:12 cycle repeated weekly for 12 weeks (cLD-shifts). Locomotor activity was monitored before the 4th ventricle ChP and suprachiasmatic nuclei (SCN) explants were recorded in real time for PER2-driven population and single-cell bioluminescence rhythms. In addition, plasma immune marker concentrations and gene expression in ChP, prefrontal cortex, hippocampus and cerebellum were analyzed. cLL dampened the SCN clock but did not shorten the inactivity interval (sleep). cLD-shifts had no effect on the SCN clock, but transiently affected sleep duration and fragmentation. Both chronodisruption protocols dampened the ChP clock. Although immune markers were elevated in plasma and hippocampus, levels in ChP were unaffected, and unlike the liver clock, the ChP clock was resistant to lipopolysaccharide treatment. Importantly, both chronodisruption protocols reduced glucocorticoid signaling in ChP. The data demonstrate the high resistance of the ChP clock to inflammation, highlighting its role in protecting the brain from neuroinflammation, and on the other hand its high sensitivity to chronodisruption. Our results provide a novel link between human lifestyle-induced chronodisruption and the impairment of ChP-dependent brain homeostasis.

Lithium affects the circadian clock in the choroid plexus - A new role for an old mechanism

Lithium is an effective mood stabilizer, but the mechanism of its therapeutic action is not well understood. We investigated the effect of lithium on the circadian clock located in the ventricle barrier complex containing the choroid plexus (CP), a part of the glymphatic system that influences gross brain function via the production of cerebrospinal fluid. The mPer2^Luc mice were injected with lithium chloride (LiCl) or vehicle, and their effects on the clock gene Nr1d1 in CP were detected by RT qPCR. CP organotypic explants were prepared to monitor bioluminescence rhythms in real time and examine the responses of the CP clock to LiCl and inhibitors of glycogen synthase kinase-3 (CHIR-99021) and protein kinase C (chelerythrine). LiCl affected Nr1d1 expression levels in CP in vivo and dose-dependently delayed the phase and prolonged the period of the CP clock in vitro. LiCl and CHIR-99021 had different effects on 1] CP clock parameters (amplitude, period, phase), 2] dexamethasone-induced phase shifts of the CP clock, and 3] dynamics of PER2 degradation and de novo accumulation. LiCl-induced phase delays were significantly reduced by chelerythrine, suggesting the involvement of PKC activity. The effects on the CP clock may be involved in the therapeutic effects of lithium and hypothetically improve brain function in psychiatric patients by aligning the function of the CP clock-related glymphatic system with the sleep-wake cycle. Importantly, our data argue for personalized timing of lithium treatment in BD patients.

Misaligned feeding schedule elicits divergent circadian reorganizations in endo- and exocrine pancreas clocks

Misaligned feeding may lead to pancreatic insufficiency, however, whether and how it affects circadian clock in the exocrine pancreas is not known. We exposed rats to a reversed restricted feeding regimen (rRF) for 10 or 20 days and analyzed locomotor activity, daily profiles of hormone levels (insulin, glucagon, and corticosterone) in plasma, and clock gene expression in the liver and endocrine and exocrine pancreas. In addition, we monitored responses of the exocrine pancreatic clock in organotypic explants of mPer2Luc mice in real time to acetylcholine, insulin, and glucocorticoids. rRF phase-reversed the clock in the endocrine pancreas, similar to the clock in the liver, but completely abolished clock gene rhythmicity and significantly downregulated the expression of Cpb1 and Cel in the exocrine pancreas. rRF desynchronized the rhythms of plasma insulin and corticosterone. Daily profiles of their receptor expression differed in the two parts of the pancreas and responded differently to rRF. Additionally, the pancreatic exocrine clock responded differently to treatments with insulin and the glucocorticoid analog dexamethasone in vitro. Mathematical simulation confirmed that the long-term misalignment between these two hormonal signals, as occurred under rRF, may lead to dampening of the exocrine pancreatic clock. In summary, our data suggest that misaligned meals impair the clock in the exocrine part of the pancreas by uncoupling insulin and corticosterone rhythms. These findings suggest a new mechanism by which adverse dietary habits, often associated with shift work in humans, may impair the clock in the exocrine pancreas and potentially contribute to exocrine pancreatic insufficiency.

Early rhythmicity in the fetal suprachiasmatic nuclei in response to maternal signals detected by omics approach

The suprachiasmatic nuclei (SCN) of the hypothalamus harbor the central clock of the circadian system, which gradually matures during the perinatal period. In this study, time-resolved transcriptomic and proteomic approaches were used to describe fetal SCN tissue-level rhythms before rhythms in clock gene expression develop. Pregnant rats were maintained in constant darkness and had intact SCN, or their SCN were lesioned and behavioral rhythm was imposed by temporal restriction of food availability. Model-selecting tools dryR and CompareRhythms identified sets of genes in the fetal SCN that were rhythmic in the absence of the fetal canonical clock. Subsets of rhythmically expressed genes were assigned to groups of fetuses from mothers with either intact or lesioned SCN, or both groups. Enrichment analysis for GO terms and signaling pathways revealed that neurodevelopment and cell-to-cell signaling were significantly enriched within the subsets of genes that were rhythmic in response to distinct maternal signals. The findings discovered a previously unexpected breadth of rhythmicity in the fetal SCN at a developmental stage when the canonical clock has not yet developed at the tissue level and thus likely represents responses to rhythmic maternal signals.

Circadian Rhythms and Sleep Are Dependent Upon Expression Levels of Key Ubiquitin Ligase Ube3a

Normal neurodevelopment requires precise expression of the key ubiquitin ligase gene Ube3a. Comparing newly generated mouse models for Ube3a downregulation (models of Angelman syndrome) vs. Ube3a upregulation (models for autism), we find reciprocal effects of Ube3a gene dosage on phenotypes associated with circadian rhythmicity, including the amount of locomotor activity. Consistent with results from neurons in general, we find that Ube3a is imprinted in neurons of the suprachiasmatic nuclei (SCN), the pacemaking circadian brain locus, despite other claims that SCN neurons were somehow exceptional to these imprinting rules. In addition, Ube3a-deficient mice lack the typical drop in wake late in the dark period and have blunted responses to sleep deprivation. Suppression of physical activity by light in Ube3a-deficient mice is not due to anxiety as measured by behavioral tests and stress hormones; quantification of stress hormones may provide a mechanistic link to sleep alteration and memory deficits caused by Ube3a deficiency, and serve as an easily measurable biomarker for evaluating potential therapeutic treatments for Angelman syndrome. We conclude that reduced Ube3a gene dosage affects not only neurodevelopment but also sleep patterns and circadian rhythms.

High Sensitivity of the Circadian Clock in the Hippocampal Dentate Gyrus to Glucocorticoid- and GSK3-Beta-Dependent Signals

AIMS

Circadian clocks in the hippocampus (HPC) align memory processing with appropriate time of day. Our study was aimed at ascertaining the specificity of glycogen synthase kinase 3-beta (GSK3β)- and glucocorticoid (GC)-dependent pathways in the entrainment of clocks in individual HPC regions, CA1-3, and dentate gyrus (DG).

METHODS

The role of GCs was addressed in vivo by comparing the effects of adrenalectomy (ADX) and subsequent dexamethasone (DEX) supplementation on clock gene expression profiles (Per1, Per2, Nr1d1, and Bmal1). In vitro the effects of DEX and the GSK3β inhibitor, CHIR-99021, were assessed from recordings of bioluminescence rhythms in HPC organotypic explants of mPER2Luc mice.

RESULTS

Circadian rhythms of clock gene expression in all HPC regions were abolished by ADX, and DEX injections to the rats rescued those rhythms in DG. The DEX treatment of the HPC explants significantly lengthened periods of the bioluminescence rhythms in all HPC regions with the most significant effect in DG. In contrast to DEX, CHIR-99021 significantly shortened the period of bioluminescence rhythm. Again, the effect was most significant in DG which lacks the endogenously inactivated (phosphorylated) form of GSK3β. Co-treatment of the explants with CHIR-99021 and DEX produced the CHIR-99021 response. Therefore, the GSK3β-mediated pathway had dominant effect on the clocks.

CONCLUSION

GSK3β- and GC-dependent pathways entrain the clock in individual HPC regions by modulating their periods in an opposite manner. The results provide novel insights into the mechanisms connecting the arousal state-relevant signals with temporal control of HPC-dependent memory and cognitive functions.

Targeted modification of the Per2 clock gene alters circadian function in mPer2luciferase (mPer2Luc) mice

Modification of the Per2 clock gene in mPer2Luc reporter mice significantly alters circadian function. Behavioral period in constant dark is lengthened, and dissociates into two distinct components in constant light. Rhythms exhibit increased bimodality, enhanced phase resetting to light pulses, and altered entrainment to scheduled feeding. Mechanistic mathematical modelling predicts that enhanced protein interactions with the modified mPER2 C-terminus, combined with differential clock regulation among SCN subregions, can account for effects on circadian behavior via increased Per2 transcript and protein stability. PER2::LUC produces greater suppression of CLOCK:BMAL1 E-box activity than PER2. mPer2Luc carries a 72 bp deletion in exon 23 of Per2, and retains a neomycin resistance cassette that affects rhythm amplitude but not period. The results show that mPer2Luc acts as a circadian clock mutation illustrating a need for detailed assessment of potential impacts of c-terminal tags in genetically modified animal models.

Challenging the Integrity of Rhythmic Maternal Signals Revealed Gene-Specific Responses in the Fetal Suprachiasmatic Nuclei

During fetal stage, maternal circadian system sets the phase of the developing clock in the suprachiasmatic nuclei (SCN) via complex pathways. We addressed the issue of how impaired maternal signaling due to a disturbed environmental light/dark (LD) cycle affects the fetal SCN. We exposed pregnant Wistar rats to two different challenges - a 6-h phase shift in the LD cycle on gestational day 14, or exposure to constant light (LL) throughout pregnancy - and detected the impact on gene expression profiles in 19-day-old fetuses. The LD phase shift, which changed the maternal SCN into a transient state, caused robust downregulation of expression profiles of clock genes (Per1, Per2, and Nr1d1), clock-controlled (Dbp) genes, as well as genes involved in sensing various signals, such as c-fos and Nr3c1. Removal of the rhythmic maternal signals via exposure of pregnant rats to LL abolished the rhythms in expression of c-fos and Nr3c1 in the fetal SCN. We identified c-fos as the gene primarily responsible for sensing rhythmic maternal signals because its expression profile tracked the shifted or arrhythmic maternal SCN clock. Pathways related to the maternal rhythmic behavioral state were likely not involved in driving the c-fos expression rhythm. Instead, introduction of a behavioral rhythm to LL-exposed mothers via restricted feeding regime strengthened rhythm in Vip expression in the fetal SCN. Our results revealed for the first time that the fetal SCN is highly sensitive in a gene-specific manner to various changes in maternal signaling due to disturbances of environmental cycles related to the modern lifestyle in humans.

Generation of a Novel Rat Model of Angelman Syndrome with a Complete Ube3a Gene Deletion

Angelman syndrome (AS) is a rare genetic disorder characterized by severe intellectual disability, seizures, lack of speech, and ataxia. The gene responsible for AS was identified as Ube3a and it encodes for E6AP, an E3 ubiquitin ligase. Currently, there is very little known about E6AP's mechanism of action in vivo or how the lack of this protein in neurons may contribute to the AS phenotype. Elucidating the mechanistic action of E6AP would enhance our understanding of AS and drive current research into new avenues that could lead to novel therapeutic approaches that target E6AP's various functions. To facilitate the study of AS, we have generated a novel rat model in which we deleted the rat Ube3a gene using CRISPR. The AS rat phenotypically mirrors human AS with loss of Ube3a expression in the brain and deficits in motor coordination as well as learning and memory. This model offers a new avenue for the study of AS. Autism Res 2020, 13: 397-409. © 2020 International Society for Autism Research,Wiley Periodicals, Inc. LAY SUMMARY: Angelman syndrome (AS) is a rare genetic disorder characterized by severe intellectual disability, seizures, difficulty speaking, and ataxia. The gene responsible for AS was identified as UBE3A, yet very little is known about its function in vivo or how the lack of this protein in neurons may contribute to the AS phenotype. To facilitate the study of AS, we have generated a novel rat model in which we deleted the rat Ube3a gene using CRISPR. The AS rat mirrors human AS with loss of Ube3a expression in the brain and deficits in motor coordination as well as learning and memory. This model offers a new avenue for the study of AS.

Development and Entrainment of the Fetal Clock in the Suprachiasmatic Nuclei: The Role of Glucocorticoids

The adult circadian clock in the suprachiasmatic nucleus (SCN) of the hypothalamus is resilient to glucocorticoids (GCs). The fetal rodent SCN resembles that of the adult in its organization of GC-sensitive peripheral tissues. We tested the hypothesis that the fetal SCN clock is sensitive to changes in GC levels. Maternal GCs must pass through the placenta to reach the fetal SCN. We show that the maternal but not the fetal part of the placenta harbors the autonomous circadian clock, which is reset by dexamethasone (DEX) and rhythmically expresses Hsd11b2. The results suggest the presence of a mechanism for rhythmic GC passage through the placental barrier, which is adjusted according to actual GC levels. GC receptors are expressed rhythmically in the laser-dissected fetal SCN samples. We demonstrate that hypothalamic explants containing the SCN of the mPer2 ^Luc mouse prepared at embryonic day (E)15 spontaneously develop rhythmicity within several days of culture, with dynamics varying among fetuses from the same litter. Culturing these explants in media enriched with DEX accelerates the development. At E17, treatment of the explants with DEX induces phase advances and phase delays of the rhythms depending on the timing of treatments, and the shifts are completely blocked by the GC receptor antagonist, mifepristone. The DEX-induced phase-response curve differs from that induced by the vehicle. The fetal SCN is sensitive to GCs in vivo because DEX administration to pregnant rats acutely downregulates c-fos expression specifically in the laser-dissected fetal SCN. Our results provide evidence that the rodent fetal SCN clock may respond to changes in GC levels.

Implicit time-place conditioning alters Per2 mRNA expression selectively in striatum without shifting its circadian clocks

Animals create implicit memories of the time of day that significant events occur then anticipate the recurrence of those conditions at the same time on subsequent days. We tested the hypothesis that implicit time memory for daily encounters relies on the setting of the canonical circadian clockwork in brain areas involved in the formation or expression of context memories. We conditioned mice to avoid locations paired with a mild foot shock at one of two Zeitgeber times set 8 hours apart. Place avoidance was exhibited only when testing time matched the prior training time. The suprachiasmatic nucleus, dorsal striatum, nucleus accumbens, cingulate cortex, hippocampal complex, and amygdala were assessed for clock gene expression. Baseline phase dependent differences in clock gene expression were found in most tissues. Evidence for conditioned resetting of a molecular circadian oscillation was found only in the striatum (dorsal striatum and nucleus accumbens shell), and specifically for Per2 expression. There was no evidence of glucocorticoid stress response in any tissue. The results are consistent with a model where temporal conditioning promotes a selective Per2 response in dopamine-targeted brain regions responsible for sensorimotor integration, without resetting the entire circadian clockwork.

The McGill Transgenic Rat Model of Alzheimer's Disease Displays Cognitive and Motor Impairments, Changes in Anxiety and Social Behavior, and Altered Circadian Activity

The McGill-R-Thy1-APP transgenic rat is an animal model of the familial form of Alzheimer's disease (AD). This model mirrors several neuropathological hallmarks of the disease, including the accumulation of beta-amyloid and the formation of amyloid plaques (in homozygous animals only), neuroinflammation and the gradual deterioration of cognitive functions even prior to plaque formation, although it lacks the tauopathy observed in human victims of AD. The goal of the present study was a thorough characterization of the homozygous model with emphasis on its face validity in several domains of behavior known to be affected in AD patients, including cognitive functions, motor coordination, emotionality, sociability, and circadian activity patterns. On the behavioral level, we found normal locomotor activity in spontaneous exploration, but problems with balance and gait coordination, increased anxiety and severely impaired spatial cognition in 4–7 month old homozygous animals. The profile of social behavior and ultrasonic communication was altered in the McGill rats, without a general social withdrawal. McGill rats also exhibited changes in circadian profile, with a shorter free-running period and increased total activity during the subjective night, without signs of sleep disturbances during the inactive phase. Expression of circadian clock gene Bmal1 was found to be increased in the parietal cortex and cerebellum, while Nr1d1 expression was not changed. The clock-controlled gene Prok2 expression was found to be elevated in the parietal cortex and hippocampus, which might have contributed to the observed changes in circadian phenotype. We conclude that the phenotype in the McGill rat model is not restricted to the cognitive domain, but also includes gait problems, changes in emotionality, social behavior, and circadian profiles. Our findings show that the model should be useful for the development of new therapeutic approaches targeting not only memory decline but also other symptoms decreasing the quality of life of AD patients.

Registered Replication Report: Rand, Greene, and Nowak (2012)

In an anonymous 4-person economic game, participants contributed more money to a common project (i.e., cooperated) when required to decide quickly than when forced to delay their decision (Rand, Greene & Nowak, 2012), a pattern consistent with the social heuristics hypothesis proposed by Rand and colleagues. The results of studies using time pressure have been mixed, with some replication attempts observing similar patterns (e.g., Rand et al., 2014) and others observing null effects (e.g., Tinghög et al., 2013; Verkoeijen & Bouwmeester, 2014). This Registered Replication Report (RRR) assessed the size and variability of the effect of time pressure on cooperative decisions by combining 21 separate, preregistered replications of the critical conditions from Study 7 of the original article (Rand et al., 2012). The primary planned analysis used data from all participants who were randomly assigned to conditions and who met the protocol inclusion criteria (an intent-to-treat approach that included the 65.9% of participants in the time-pressure condition and 7.5% in the forced-delay condition who did not adhere to the time constraints), and we observed a difference in contributions of -0.37 percentage points compared with an 8.6 percentage point difference calculated from the original data. Analyzing the data as the original article did, including data only for participants who complied with the time constraints, the RRR observed a 10.37 percentage point difference in contributions compared with a 15.31 percentage point difference in the original study. In combination, the results of the intent-to-treat analysis and the compliant-only analysis are consistent with the presence of selection biases and the absence of a causal effect of time pressure on cooperation.

Registered Replication Report

Finkel, Rusbult, Kumashiro, and Hannon (2002, Study 1) demonstrated a causal link between subjective commitment to a relationship and how people responded to hypothetical betrayals of that relationship. Participants primed to think about their commitment to their partner (high commitment) reacted to the betrayals with reduced exit and neglect responses relative to those primed to think about their independence from their partner (low commitment). The priming manipulation did not affect constructive voice and loyalty responses. Although other studies have demonstrated a correlation between subjective commitment and responses to betrayal, this study provides the only experimental evidence that inducing changes to subjective commitment can causally affect forgiveness responses. This Registered Replication Report (RRR) meta-analytically combines the results of 16 new direct replications of the original study, all of which followed a standardized, vetted, and preregistered protocol. The results showed little effect of the priming manipulation on the forgiveness outcome measures, but it also did not observe an effect of priming on subjective commitment, so the manipulation did not work as it had in the original study. We discuss possible explanations for the discrepancy between the findings from this RRR and the original study.

Mechanisms of hormonal regulation of the peripheral circadian clock in the colon

Colonic function is controlled by an endogenous clock that allows the colon to optimize its function on the daytime basis. For the first time, this study provided evidence that the clock is synchronized by rhythmic hormonal signals. In rat colon, adrenalectomy decreased and repeated applications of dexamethasone selectively rescued circadian rhythm in the expression of the clock gene Per1. Dexamethasone entrained the colonic clock in explants from mPer2^Luc mice in vitro. In contrast, pinealectomy had no effect on the rat colonic clock, and repeated melatonin injections were not able to rescue the clock in animals maintained in constant light. Additionally, melatonin did not entrain the clock in colonic explants from mPer2^Luc mice in vitro. However, melatonin affected rhythmic regulation of Nr1d1 gene expression in vivo. The findings provide novel insight into possible beneficial effects of glucocorticoids in the treatment of digestive tract-related diseases, greatly exceeding their anti-inflammatory action.

Melatonin is a redundant entraining signal in the rat circadian system

The role of melatonin in maintaining proper function of the circadian system has been proposed but very little evidence for such an effect has been provided. To ascertain the role, the aim of the study was to investigate impact of long-term melatonin absence on regulation of circadian system. The parameters of behavior and circadian clocks of rats which were devoid of the melatonin signal due to pinealectomy (PINX) for more than one year were compared with those of intact age-matched controls. PINX led to a decrease in spontaneous locomotor activity and a shortening of the free-running period of the activity rhythm driven by the central clock in the suprachiasmatic nuclei (SCN) in constant darkness. However, the SCN-driven rhythms in activity and feeding were not affected and remained well entrained in the light/dark cycle. In contrast, in these conditions PINX had a significant effect on amplitudes of the clock gene expression rhythms in the duodenum and also partially in the liver. These results demonstrate the significant impact of long-term melatonin absence on period of the central clock in the SCN and the amplitudes of the peripheral clocks in duodenum and liver and suggest that melatonin might be a redundant but effective endocrine signal for these clocks.

In vivo initiation of clock gene expression rhythmicity in fetal rat suprachiasmatic nuclei

The mammalian suprachiasmatic nuclei (SCN) and their intrinsic rhythmicity develop gradually during ontogenesis. In the rat, the SCN forms between embryonic day (E) 14 and E17, with gestation terminating at E21–22. Overt SCN rhythmicity is already present in the late embryonic stage. The aim of the present study was to determine when the fetal SCN clock develops in vivo and whether overt rhythmicity results from a functional fetal clock. To achieve this goal, the prenatal development of rhythmic expression of clock genes was measured with a more sensitive method for detection of the clock gene expression than previously. Fetal SCN were collected at 3 h intervals during the 24 h period on E19 and E21 by laser dissection and expression of clock genes (Per2, Nr1d1 and Bmal1) and genes related to cellular activity (c-fos, Avp and Vip) was measured by qRT PCR. At E19, the expression of canonical clock genes Per2 and Bmal1 was not rhythmic; however, the expression of all other studied genes followed clear circadian rhythms. At E21, Per2 and Bmal1 expression exhibited low amplitude but significant rhythmicity. From E19 to E21, the levels of the non-rhythmic transcripts (Per2 and Bmal1) decreased; however, the levels of the rhythmic transcripts (Nr1d1, c-fos, Avp and Vip) increased. In summary, these data demonstrate that at E19, rhythms in Per2 and Bmal1 expression were absent in the fetal SCN; however, the expression of Nr1d1 and other genes related to cellular activity was driven rhythmically. Therefore, at the early stage in vivo, the developing fetal SCN clock could theoretically be entrained by oscillation of Nr1d1 which may be driven by the maternal rather than fetal circadian system.

An ex-vivo oral mucosa infection model for the evaluation of the topical activity of antifungal agents

Although Nystatin has been used since 1950s as a non-absorbable antifungal agent, there is still no reliable in-vivo data available stating a dose-effect relationship of Nystatin-suspension in the treatment of oropharyngeal infection with Candida albicans. Here, we studied the efficacy of a commercially available topical Nystatin suspension in a new ex-vivo model of candidiasis using porcine oral mucosa. After 48 and 96 h of C. albicans infection, 230 IU Nystatin (standard dosage), 100 IU and 20 IU proved to be equally efficacious. Multiple applications of Nystatin were not superior compared with single application. In dosages of 10 and 0.1 IU the activity of Nystatin suspension against C. albicans was no longer confirmed. In an agar diffusion model, the minimal biocidal concentration of Nystatin proved to be 0.25 IU. Our results suggest that the proposed porcine ex-vivo model is much closer to the in-vivo situation compared with other established in-vitro models of the treatment of muco-cutaneous candidiasis and may provide a substitute for animal models in the investigation of antifungal agents. Additionally, it seems to be a valuable tool for further investigations of the pathogenesis of C. albicans infections.

Tight Junction Proteins in the Skin

It has long been accepted that tight junctions (TJ) are crucial for the formation and maintenance of the paracellular barrier and for cell polarity in simple epithelia and endothelia. Moreover, it is long known that they play a role in barrier function of amphibian skin. However, only in recent years were TJ and TJ proteins identified in the epidermis of men and mice. Their involvement in the barrier function of mammalian skin has been shown. This review summarizes our current knowledge about TJ and TJ proteins in mammalian skin.

Telomerase activity of Merkel cell carcinomas and Merkel cell carcinoma-derived cell cultures

Merkel cell carcinomas are rare malignant tumors of the skin, which are predominantly observed in elderly patients (mean age 65-70 years). It is believed but not yet proven that these tumors are derived from the Merkel cells of the epidermis and hair follicles. The Merkel cells themselves probably originate from an asymmetric cell division of basal keratinocytes and the resulting differentiated Merkel cells have presumably, at least in humans, lost their growth potential. The capability of indefinite cell division in germ line cells and in the great majority of malignant tumors as well as an increased growth potential in certain somatic cells (such as basal cells of renewable tissues) is correlated with cellular telomerase activity, which is absent in differentiated somatic cells. In this study the telomerase activity in cryostat sections of frozen Merkel cell tumor biopsies and in in vitro cultivated Merkel cell carcinoma cells was analyzed. We detected telomerase activity in four tumors and three of four cell cultures. These results show that despite their pronounced neuroendocrine differentiation and their occurrence in patients of advanced age, Merkel cell carcinomas possess telomerase activity similar to that of common carcinoma types.

Diversity of desmosomal proteins in regenerating epidermis: immunohistochemical study using a human skin organ culture model

We recently established a skin organ culture model for epithelial healing by creating a central defect in freshly excised human skin specimens and keeping them in culture for up to 7 days, either untreated or with transplantation of allogenic or autologous keratinocytes. In this study the molecular diversity of cell-cell junction proteins in the regenerating epidermis was analysed immunohistochemically using a broad spectrum of monoclonal antibodies against glycoproteins (cadherins) and plaque proteins of desmosomes. At all stages studied the entire set of desmosomal cadherins [desmogleins (Dsg) 1-3 and desmocollins (Dsc) 1-3] was detected, with Dsg3, Dsc2 and Dsc3 being the most prominent. In the disordered neoepithelium at day 3 (after transplantation) some desmosomal cadherins appeared in their respective stratum compartments. In regenerating epidermis on day 7, which exhibited a more ordered stratification and a compact horny layer, stratification-related patterns of desmosomal cadherins were more pronounced. However, some immaturity of the day-7 neoepidermis was reflected by relatively low levels of the maturation-associated Dsgl and Dsc1 and a strong basal layer expression of Dsg2 which is sparse in normal epidermis. Desmosomal plaque proteins showed expression patterns similar to those in normal healthy epidermis. The adherens junction-related E-cadherin was also detected. Dendritic cells (melanocytes, Langerhans cells) were mainly present at the wound margins. In conclusion, this study demonstrated partial but not complete epidermal maturation and junction development during regeneration up to day 7. This model should also be useful in future studies to evaluate the effects of growth hormones to be used in therapeutic trials on chronic leg ulcers.

Characterization of epidermal wound healing in a human skin organ culture model: acceleration by transplanted keratinocytes

Few data are available on early regeneration of human epidermis in vivo. We have established a supravital skin organ culture model for epidermal wound healing by setting a central defect (3 mm diameter) in freshly excised skin specimens and culturing under air exposure. Re-epithelialization was followed for up to 7 d by histology and immunohistologic analysis of various markers for differentiation and proliferation. In 12 of 19 cases (63%; 5% fetal calf serum) or six of 21 cases (29%; 2% fetal calf serum), the wounds were re-epithelialized spontaneously after 7 d. After transplantation to the wounds of 1-2 x 10(6) dissociated allogenic cultured epidermal or about 1 x 10(6) autologous outer root sheath keratinocytes, 18 of 21 cases (86%; 5% fetal calf serum) or 17 of 21 cases (81%; 2% fetal calf serum) were healed within the same period. Histologically, early neoepithelium (3 d) was disordered after keratinocyte transplantation, whereas later (7 d) it had gained a more ordered stratification, exhibiting a thin discontinuous granular and a compact horny layer. At this stage, not only hyperproliferative (CK 6) but also, abundantly, maturation-associated cytokeratins (CK 1, CK 10) were detected immunohistochemically. Analyses of regenerated epidermis after transplantation of (i) keratinocytes labeled in vitro with BrdU and (ii) heterosexual keratinocytes by immunohistochemistry and fluorescence in situ hybridization for the Y chromosome, respectively, clearly showed that external keratinocytes are physically integrated into the regenerated epidermis and extendedly contribute to its formation. The data presented here demonstrate improvement and acceleration of epidermal re-epithelialization by transplantation of keratinocytes.

Radioresistance in murine solid tumors induced by interleukin-1

Interleukin-1 (IL-1) has radioprotective activity in hematopoietic lineages and in other normal cell renewal systems, but little is known about the effects of IL-1 alpha on the radiosensitivity of tumor cell populations. The present studies were conducted to investigate the effects of IL-1 alpha on the radiosensitivity of clonogenic cells in RIF-1 and SCC-7 tumors. Radioresistance was detected within 2-4 after administration of IL-1 alpha (0.5 micrograms/mouse, ip) and characterized by increases in D(o), Dq, alpha/beta and SF2. This radioresistance was similar to that seen in tumors rendered totally hypoxic before X irradiation. Tirapazamine, a hypoxic cell cytotoxin, and IL-1 alpha had synergistic schedule-dependent antitumor activity in vivo, suggesting that IL-1-induced radioresistance in vivo is due to hypoxia. Radioresistance induced by IL-1 alpha was transient, and the data suggested reoxygenation within 12 h. In vitro, IL-1 alpha had no direct effect on the radiosensitivity of SCC-7 cells in tissue culture under aerobic conditions. However, an increase in D(o), alpha/beta and SF2 was seen in clonogenic tumor cells from primary cultures treated with IL-1 alpha under aerobic conditions. Superoxide dismutase and catalase prevented the induction of radioresistance by IL-1 alpha in vitro, suggesting that oxidative responses from tumor macrophages after administration of IL-1 alpha may be responsible for induced radioresistance by IL-1 in vitro. Although oxidant stress induced by IL-1 and in vitro in our models, the mechanisms by which such responses modulate tumor radiosensitivity in vivo and in vitro are likely quite different.

Conservative surgery and radiation therapy for intraductal carcinoma of the breast

Nineteen women with intraductal carcinoma of the breast were treated with conservative surgery and radiotherapy from 1982 to 1990. All underwent excisional biopsy or wide local excision of the primary tumor. Definitive irradiation consisted of 4500 cGy in 180 cGy fractions given through tangential fields followed by a breast boost to the primary site to a total dose of 5900-6500 cGy. No patient received regional node irradiation. Median follow-up was 38 months. The five year actuarial rate of local failure was 9%. One patient failed with an infiltrating ductal carcinoma in the treated breast 31 months after initial treatment. Salvage mastectomy was performed. She remains without evidence of disease 43 months after initial treatment. Metastatic breast carcinoma has not developed in any of the patients. Cosmetic result was good to excellent in all patients. With short-term follow-up, conservative surgery and radiotherapy appear to be an acceptable alternative to mastectomy in carefully selected patients with ductal carcinoma in situ. As retrospective and randomized trials mature, the natural history of these lesions treated with conservative surgery and irradiation will be further defined.

Conservative surgery and radiation therapy for early stage breast cancer. Can large trial experiences be reproduced in a community hospital setting?

Conservative surgery and radiation therapy were used to treat 212 patients with AJC clinical Stage I or II breast carcinoma at the Baptist Hospital of Miami. All had lumpectomy and most axillary lymph node dissection, followed by breast irradiation to a dose of 45 Gy and a boost dose of 14 to 16 Gy to the surgical bed. Median follow-up was 55 months. The five-year actuarial local control and survival rates were 94% and 86% respectively. Eighty-six percent of the patients had excellent or good cosmetic results with minimal differences between the treated and untreated breasts. Treatment-related complications were minor and infrequent. These results appear comparable to retrospective reviews at major university centers and ongoing prospective randomized trials.

A multipurpose CT-guided stereotactic instrument of simple design

The instrument is based upon a radiolucent ring fixed to the skull by four pins. This locks into a frame for CT scanning from which the x, y and z stereotactic coordinates are derived. The head ring may be locked into a compatible support on the operating table for biopsy. A similar support and localization system is used for rotational radiotherapy. With the current 14 MeV apparatus, fields as small as 2 cm in diameter are available with 90% dosage fall-off in the surrounding 1-cm shell.