Comparison on collagen gene expression in the developing chick embryo tendon and heart. Tissue and development time-dependent action of dexamethasone

Current Practices for Reference Gene Selection in RT-qPCR of Aspergillus: Outlook and Recommendations for the Future

Aspergillus is a genus of filamentous fungi with vast geographic and ecological distributions. Species within this genus are clinically, agriculturally and biotechnologically relevant, leading to increasing interest in elucidating gene expression dynamics of key metabolic and physiological processes. Reverse-transcription quantitative Polymerase Chain Reaction (RT-qPCR) is a sensitive and specific method of quantifying gene expression. A crucial step for comparing RT-qPCR results between strains and experimental conditions is normalisation to experimentally validated reference gene(s). In this review, we provide a critical analysis of current reference gene selection and validation practices for RT-qPCR gene expression analyses of Aspergillus. Of 90 primary research articles obtained through our PubMed query, 17 experimentally validated the reference gene(s) used. Twenty reference genes were used across the 90 studies, with beta-tubulin being the most used reference gene, followed by actin, 18S rRNA and glyceraldehyde 3-phosphate dehydrogenase. Sixteen of the 90 studies used multiple reference genes for normalisation. Failing to experimentally validate the stability of reference genes can lead to conflicting results, as was the case for four studies. Overall, our review highlights the need to experimentally validate reference genes in RT-qPCR studies of Aspergillus.

The Effects of Glucocorticoid on Tendon and Tendon Derived Cells

Glucocorticoids are generally used to relieve pain and/or inflammation in a wide variety of musculoskeletal disorders including osteoarthritis, inflammatory arthritis, tendinopathy and degenerative spine disease. Glucocorticoids reduce tendon derived cell proliferation in vitro and reduce extracellular matrix synthesis both in vitro and in vivo, in particular type I collagen synthesis. Glucocorticoids also appear to result in acute deleterious changes in healthy in vivo tendon including collagen necrosis, collagen disorganisation and inflammatory cell infiltration; while the overall effect of glucocorticoid administration on the mechanical properties of healthy in vivo tendon are generally negative. Overall the existing in vitro and in vivo evidence suggests that glucocorticoids should be used with caution in treating painful tendinopathy. Certainly a real need exists to follow up the long term clinical effects of glucocorticoid in treating tendinopathy, as there is currently a paucity of evidence in this area. However in this context while the short term benefits are clear, glucocorticoids remain a useful treatment option provided they are used in the right patients in sensible moderation.

The mRNA and Protein Levels of Tubulin and β-Actin Are Greatly Reduced in the Proximal Duodenum of Mice Relative to the Rest of the Small Intestines

To accurately quantify mRNA and protein levels, it is critical to choose appropriate internal standards. As the expression of housekeeping genes is assumed to remain constant, they are often employed to normalize signals to correct for sample-to-sample variations. However, recent studies have documented that β-actin and Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression levels change in response to various stimuli during proliferation, activation, and differentiation. We investigated levels of α-, β-, γ-tubulin, β-actin, and GAPDH vary across the gastrointestinal tract of mice. We found that different regions of the small intestines had dramatically different expression profiles, as measured by western blot, quantitative Reverse transcription polymerase chain reaction (RT-PCR), and immunohistochemical staining. These results revealed that the expression levels of tubulins and β-actin were dramatically lower in the proximal duodenum, relative to the rest of the small intestines. These varying levels of housekeeping genes may reflect differences in the activities of specialized tissues and suggest unique requirements for tubulins in these tissue types. We conclude that the use of a single housekeeping gene to normalize gene expression in the gastrointestinal tracts of mice may introduce errors, as measured differences in gene expression may reflect regulation of the internal control rather than the mRNA or protein under investigation.

The risks and benefits of glucocorticoid treatment for tendinopathy: a systematic review of the effects of local glucocorticoid on tendon

OBJECTIVE

Our primary objective was to summarise the known effects of locally administered glucocorticoid on tendon tissue and tendon cells.

METHODS

We conducted a systematic review of the scientific literature using the PRISMA and Cochrane guidelines of the Medline database using specific search criteria. The search yielded 50 articles, which consisted of 13 human studies, 36 animal studies and one combined human/animal study.

RESULTS

Histologically, there was a loss of collagen organisation (6 studies) and an increase in collagen necrosis (3 studies). The proliferation (8 studies) and viability (9 studies) of fibroblasts was reduced. Collagen synthesis was decreased in 17 studies. An increased inflammatory cell infiltrate was shown in 4 studies. Increased cellular toxicity was demonstrated by 3 studies. The mechanical properties of tendon were investigated by 18 studies. Descriptively, 6 of these studies showed a decrease in mechanical properties, 3 showed an increase, while the remaining 9 showed no significant change. A meta-analysis of the mechanical data revealed a significant deterioration in mechanical properties, with an overall effect size of -0.67 (95% CI = 0.01 to -1.33) (data from 9 studies).

CONCLUSIONS

Overall it is clear that the local administration of glucocorticoid has significant negative effects on tendon cells in vitro, including reduced cell viability, cell proliferation and collagen synthesis. There is increased collagen disorganisation and necrosis as shown by in vivo studies. The mechanical properties of tendon are also significantly reduced. This review supports the emerging clinical evidence that shows significant long-term harms to tendon tissue and cells associated with glucocorticoid injections.

Evaluation of potential reference genes for qRT-PCR studies in human hepatoma cell lines treated with TNF-α

In this study, the expression of eight candidate reference genes, B2M, ACTB, GAPDH, HMBS, HPRT1, TBP, UBC, and YWHAZ, was examined to identify optimal reference genes by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis in two human hepatoma cell lines, BEL-7402 and SMMC-7721, treated with tumor necrosis factor-α (TNF-α) for different time periods. The expression stability of these genes was analyzed by three independent algorithms: geNorm, NormFinder, and BestKeeper. Results showed that TBP was the most stably expressed gene in BEL-7402 and SMMC-7721 cell lines under current experimental conditions, and that the optimal set of reference genes required for accurate normalization was TBP and HMBS, based on the pairwise variation value determined with geNorm. UBC and ACTB were ranked as the least stable genes by same algorithms. Our findings provide evidence that using TBP alone or in combination with HMBS as endogenous controls could be a reliable method for normalizing qRT-PCR data in human hepatoma cell lines treated with TNF-α.

Perinatal and postnatal expression of Cav1.3 α1D Ca²⁺ channel in the rat heart

The novel Cav1.3 (α1D) L-type Ca²⁺ channel plays a significant role in sinoatrial (SA) and atrioventricular (AV) nodes function and in atrial fibrillation. However, the characterization of α1D Ca²⁺ channel during heart development is very limited. We used real-time RT-PCR, Western blotting, and indirect immunostaining to characterize the developmental expression and localization of α1D Ca²⁺ channel in rat hearts. Both protein and mRNA levels of α1D Ca²⁺ channel decreased postnatally. Two forms of α1D Ca²⁺ channel protein (250 and 190 kD) were observed, with the full-length (250 kD) channel protein being predominant in the prenatal stages. Both Western blots and confocal imaging demonstrated that α1D Ca²⁺ channel protein was expressed in both atria and ventricles at fetal and neonatal stages but was absent in the adult ventricles. Interestingly, α1D Ca²⁺ channel was also found at the nucleus/perinucleus of immature but not adult atrial cells. Furthermore, the nuclear staining was reproduced in adult atrial cell line, HL-1 cells, which possess immature properties. The data are first to show that α1D Ca²⁺ channel has unique age-dependent expression profile and subcellular localization in the heart, suggesting a developmental stage-dependent specific function.

Cellular localization of genes and proteins for tumor necrosis factor-α (TNF), TNF receptor types I and II in bovine endometrium

To determine which cell types produce tumor necrosis factor-α (TNF) and its receptors (TNFRI and TNFRII) in bovine endometrium, we investigated the expression and cellular localization of their mRNAs and proteins. TNF transcripts and proteins were co-localized in endometrial epithelial cells, glandular epithelial cells and endothelial cells of microvessels but not in the stromal cells. TNF protein was detected in the lysate and the cultured media of epithelial cells, but was only weakly detected in the stromal cells. Both TNFRI (TNFRSF1A) and TNFRII (TNFRSF1B) transcripts were expressed in the epithelial cells, glandular epithelial cells and the stromal cells, whereas their proteins were weakly expressed in the stroma. TNF mRNA and protein expressions in the cultured epithelial cells were increased by TNF and interleukin-1α, and the TNFRII mRNA expressions were stimulated by oxytocin. Together, TNF secreted by the endometrial cells may locally play a role in regulating uterine function throughout the estrous cycle.

Identification of endogenous control genes for normalisation of real-time quantitative PCR data in colorectal cancer

Background

Gene expression analysis has many applications in cancer diagnosis, prognosis and therapeutic care. Relative quantification is the most widely adopted approach whereby quantification of gene expression is normalised relative to an endogenously expressed control (EC) gene. Central to the reliable determination of gene expression is the choice of control gene. The purpose of this study was to evaluate a panel of candidate EC genes from which to identify the most stably expressed gene(s) to normalise RQ-PCR data derived from primary colorectal cancer tissue.

Results

The expression of thirteen candidate EC genes: B2M, HPRT, GAPDH, ACTB, PPIA, HCRT, SLC25A23, DTX3, APOC4, RTDR1, KRTAP12-3, CHRNB4 and MRPL19 were analysed in a cohort of 64 colorectal tumours and tumour associated normal specimens. CXCL12, FABP1, MUC2 and PDCD4 genes were chosen as target genes against which a comparison of the effect of each EC gene on gene expression could be determined. Data analysis using descriptive statistics, geNorm, NormFinder and qBasePlus indicated significant difference in variances between candidate EC genes. We determined that two genes were required for optimal normalisation and identified B2M and PPIA as the most stably expressed and reliable EC genes.

Conclusion

This study identified that the combination of two EC genes (B2M and PPIA) more accurately normalised RQ-PCR data in colorectal tissue. Although these control genes might not be optimal for use in other cancer studies, the approach described herein could serve as a template for the identification of valid ECs in other cancer types.

Validation of suitable house keeping genes for hypoxia-cultured human chondrocytes

Background

Hypoxic culturing of chondrocytes is gaining increasing interest in cartilage research. Culturing of chondrocytes under low oxygen tension has shown several advantages, among them increased synthesis of extracellular matrix and increased redifferentiation of dedifferentiated chondrocytes. Quantitative gene expression analyses such as quantitative real-time PCR (qRT-PCR) are powerful tools in the investigation of underlying mechanisms of cell behavior and are used routinely for differentiation and phenotype assays. However, the genes used for normalization in normoxic cell-cultures might not be suitable in the hypoxic environment. The objective of this study was to determine hypoxia-stable housekeeping genes (HKG) for quantitative real-time PCR (qRT-PCR) in human chondrocytes cultured in 21%, 5% and 1% oxygen by geNorm and NormFinder analyses.

Results

The chondrocytic response to the hypoxic challange was validated by a significant increase in expression of the hypoxia-inducible gene ankyrin repeat 37 as well as SOX9 in hypoxia. When cultured on the 3-dimentional (3D) scaffold TATA-binding protein (TBP) exhibited the highest expression stability with NormFinder while Ribosomal protein L13a (RPL13A) and beta2-microglobulin (B2M) were the most stable using geNorm analysis. In monolayer RPL13A were the most stable gene using NormFinder, while geNorm assessed RPL13A and human RNA polymerase II (RPII) as most stable. When examining the combination of (3D) culturing and monolayer RPL13A and B2M showed the highest expression stability from geNorm analysis while RPL13A also showed the highest expression stability using NormFinder. Often used HKG such as beta actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were the most unstable genes investigated in all comparisons. The pairwise variations for the two most stable HKG in each group were all below the cut-off value of 0.15, suggesting that the two most stable HKG from geNorm analysis would be sufficient for qRT-PCR.

Conclusion

All data combined we recommend RPL13A, B2M and RPII as the best choice for qRT-PCR analyses when comparing normoxic and hypoxic cultured human chondrocytes although other genes might also be suitable. However, the matching of HKG to target genes by means of a thorough investigation of the stability in each study would always be preferable.

The effect of glucocorticoids on tendon cell viability in human tendon explants

BACKGROUND AND PURPOSE

Previous studies on the culture of human tenocytes have shown that dexamethasone and triamcinolone reduce cell viability, suppress cell proliferation, and reduce collagen synthesis. However, such cell cultures lack the extracellular matrix and three-dimensional structure of normal tendons, which affects their response to stimuli. We established a human tendon explant culture system and tested the effects of dexamethasone and triamcinolone on cell viability.

METHODS

Primary human tendon explant cultures were prepared from healthy hamstring tendons. Tendon strips were harvested from hamstring tendons and cultured in 24-well plates in Dulbecco's modification of Eagle's Medium (DMEM) supplemented with 2% fetal calf serum. The tendon explants were treated with 0 microM (control), 10 microM, or 100 microM dexamethasone sodium phosphate or 0 microM (control), 10 microM, or 100 microM triamcinolone acetonide in DMEM for 96 h. Cell viability was measured by Alamar blue assay before and after glucocorticoid treatment.

RESULTS

Incubation with 10 microM and 100 microM dexamethasone reduced cell viability in human tendon explants by 35% and 45%, respectively, as compared to a 6% increase in the controls (p = 0.01, mixed-effects ANOVA). Triamcinolone at 10 microM and 100 microM reduced cell viability by 33% and 36%, respectively, as compared to a 9% increase in the controls (p = 0.07, mixed-effects ANOVA).

INTERPRETATION

Human tendon explant cultures can be used to study the effects of glucocorticoids on human tendon. Dexamethasone and triamcinolone suppress the cell viability of human tendon in its natural 3-dimensional environment with matrix anchorage. Human tendon explant cultures provide a species-specific model for further investigation of the effects of glucocorticoids on the metabolism of the extracellular matrix of human tendon, and on its mechanical properties.

GAPDH, 18S rRNA and YWHAZ are suitable endogenous reference genes for relative gene expression studies in placental tissues from human idiopathic fetal growth restriction

Comparative gene expression studies in the placenta may provide insights into molecular mechanisms of important genomic alterations in pregnancy disorders. Endogenous reference genes often referred to as housekeeping genes, are routinely used to normalise gene expression levels. For this reason, it is important that these genes be empirically evaluated for stability between placental samples including samples from complicated pregnancies. To address this issue, six candidate housekeeping genes including several commonly used ones (ACTB, GAPDH, 18S rRNA, TBP, SDHA and YWHAZ) were investigated for their expression stability in placentae obtained from pregnancies complicated by idiopathic FGR (n=25) and gestation-matched control pregnancies (n=25). Real-time PCR was performed using pre-validated gene expression assay kits. The geNorm program was used for gene stability measure (M) for the entire housekeeping genes in all control and FGR-affected placental samples. Results showed that GAPDH and 18S rRNA were most stable, with an average expression stability of M=0.441 and 0.443, respectively, followed by YWHAZ (M=0.472). SDHA, ACTB and TBP were the least stable housekeeping genes (M=0.495, 0.548 and 1.737, respectively). We recommend geometric averaging of two or more housekeeping genes to determine relative gene expression levels between FGR-affected and control placentae.

Glucocorticoids inhibit tenocyte proliferation and Tendon progenitor cell recruitment

Corticosteroid injection is commonly used to treat tendon injuries but is often associated with tendon rupture and impaired tendon healing. The effects of dexamethasone on tenocytes have been studied in vitro but only using high concentrations of dexamethasone in monolayer cultures of tenocytes over short periods of time. We have therefore investigated the effects of physiological and pharmacological concentrations of dexamethasone on monolayer cultures of tenocytes over extended time periods. We have also used fibroblastic-colony forming unit cultures to examine the effects of dexamethasone on a progenitor cell population located in tendons. Culturing tenocytes in the presence of dexamethasone for a period of 24 days resulted in a concentration-related decrease in cell number and collagen synthesis as compared to control cultures. This effect was time dependent with cell number in both dexamethasone-treated and control cultures leveling off after 14 days with the control cultures reaching higher cell densities. In contrast in control cultures, collagen accumulation continued to increase until week 4, whereas in the presence of dexamethasone, this tended to level off after 14 days. To study the role of progenitor cell recruitment, the effects of dexamethasone were investigated using the fibroblastic-colony forming unit assay. Treatment with dexamethasone at concentrations of 0.1 nM to 10 microM leads to a progressive reduction in mean colony size as compared to control cultures. Colony number remained constant at concentrations below 10 nM but fell progressively at concentrations above this. In conclusion, dexamethasone reduces both cell number and collagen synthesis in tenocyte cultures in a concentration-dependent manner by both direct effects on tenocyte proliferation and collagen accumulation, and also by modulating the recruitment of tendon progenitor cells.

Effects of Histone Deacetylase Inhibitor (HDACi); Trichostatin-A (TSA) on the expression of housekeeping genes

In quantitative RT-PCR (qRT-PCR), analysis of gene expression is dependent on normalization using housekeeping genes such as 18S rRNA, GAPDH and beta actin. However, variability in their expression has been reported to be caused by factors like drug treatment, pathological states and cell-cycle phase. An emerging area of cancer research focuses on identifying the role of epigenetic alterations such as histone modifications and DNA methylation in the initiation and progression of cancer. Histone acetylation is the best studied modification so far and has been probed through the use of histone deacetylase inhibitors (HDACi). Further, modulation of histone acetylation is currently being explored as a therapeutic strategy in the treatment of cancer and HDACis have shown promise in inhibiting tumorigenesis and metastasis. Trichostatin-A (TSA) is the most widely used HDACi. Therefore, we were driven to identify a suitable internal control for RT-PCR following TSA treatment. We performed quantitative RT-PCR analysis using mouse prostate tissue explants, human prostate cancer (LNCaP) cells and human breast cancer (T-47D and ZR-75-1) cells following TSA treatment. Expression of housekeeping genes including 18S rRNA, beta actin, GAPDH and ribosomal highly-basic 23-kDa protein (rb 23-kDa, RPL13A) were compared in vehicle versus TSA treated samples. Our results showed marked variations in 18S rRNA, beta actin mRNA and GAPDH mRNA levels in mouse prostate explants and a human prostate cancer (LNCaP) cell line following TSA treatment. Furthermore, in two human breast cancer cell lines (T-47D and ZR-75-1) 18S rRNA, beta actin mRNA and GAPDH mRNA levels varied significantly. However, RPL13A mRNA levels remained constant in all the conditions tested. Therefore, we recommend use of RPL13A as a standard for normalization during TSA treatment.

Glucocorticoids suppress proteoglycan production by human tenocytes

BACKGROUND

The role of glucocortiocid injection therapy in spontaneous tendon rupture is controversial. We hypothesized that glucocorticoids suppress proteoglycan production in tendon and studied the in vitro effects of dexamethasone and triamcinolone on proteoglycan production by cultured human tenocytes.

MATERIAL AND METHODS

We obtained primary cultures of human tenocytes from explants of healthy human patellar tendon. The human tenocytes were treated with 1 microM dexamethasone or 1 microM triamcinolone. The amount of proteoglycan production was measured by 35S-sulfate incorporation assay and compared with control cultures. The reversibility of the effect of dexamethasone by co-incubation with 10 ng platelet-derived growth factor (PDGFBB) was also tested.

RESULTS

Treatment with 1 microM triamcinolone reduced the amount of 35S-sulfate incorporation to 80% of control cultures (p = 0.007), whereas 1 microM dexamethasone reduced it to 72% (p = 0.01). Co-incubation of 10 ng/mL PDGFBB with 1 microM dexamethasone returned the 35S-sulfate incorporation to a level that was significantly higher than for dexamethasone treatment alone (108%; p = 0.01).

INTERPRETATION

Glucocorticoids suppressed proteoglycan production in cultured human tenocytes. The suppression by dexamethasone was reversed by simultaneous addition of PDGFBB. Suppressed proteoglycan production may affect the viscoelastic properties of tendon and increase the risk of spontaneous rupture.

Housekeeping gene variability in normal and cancerous colorectal, pancreatic, esophageal, gastric and hepatic tissues

Careful normalization is essential for the accurate quantitation of mRNA levels in biopsy-sized tissue samples. Commonly, normalization of the target gene with an endogenous standard, mainly housekeeping genes (HKGs), is applied. However, differences in the expression levels of endogenous reference genes have been reported between different tissues and pathological states. Therefore, we were challenged to identify a set of endogenous reference genes whose mRNA expression levels would not change significantly between normal and cancerous tissues. Quantitative real-time PCR (Q-RT-PCR) analysis was applied to evaluate the variability in gene expression among 21 classical housekeeping genes in colorectal, pancreatic, esophageal and gastric cancer as well as in liver metastases in comparison to the corresponding normal tissue. Our results indicated that some housekeeping genes were candidates with relatively stable gene expression in several of the investigated tissues but for most of the HKGs under investigation our data have revealed distinct differences in the extent of variability in gene expression between the different tissues and pathological states. However, for each of the five tissues investigated we found a group of genes that were expressed at a constant level thus representing a panel of candidates that we can recommend as housekeeping genes in the respective tissue types. In summary, our results can be used as guidance for other scientists studying various carcinomas for tissue-specific selection of the optimal housekeeping gene (HKG) to be used in normalizing target gene expression.

Triamcinolone suppresses human tenocyte cellular activity and collagen synthesis

Glucocorticoid injection is widely used in tendon disorders. Despite previous studies on the histologic and biomechanical changes in tendons after glucocorticoid injections, the role of glucocorticoid in tendon rupture still is controversial. It was hypothesized that glucocorticoid has a direct deleterious effect on human tenocytes, suppressing its cellular activity and collagen production. Primary cultures of human tenocytes were obtained from explants of healthy patellar tendon harvested during anterior cruciate ligament reconstructions. The effects on cell viability and cell proliferation were measured by [3-(4,5-demethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and 5-bromo-deoxyuridine incorporations. The effect on collagen synthesis was measured by H-proline incorporation assay. Triamcinolone acetonide at 10 to 10 mol/L decreased human tenocyte viability to 45% to 88% of control in a dose-dependent manner. Cell proliferation was suppressed to 87% +/- 8% at all doses. Treatment with 1 micromol/L triamcinolone acetonide reduced the amount of collagen synthesis as measured by H-proline incorporation from 40 +/- 2 cpm/1000 cells to 27 +/- 4 cpm/1000 cells. The suppressed human tenocyte cellular activity and reduced collagen production may lead to disturbed tendon structure and predispose the tendon to subsequent spontaneous rupture.

Effect of dexamethasone on cultured human tenocytes and its reversibility by platelet-derived growth factor

BACKGROUND

Many cases of tendon rupture after glucocorticoid injections have been reported in the literature. Despite previous studies on the histological and biomechanical changes in tendons after glucocorticoid injections, the role of glucocorticoid in causing tendon rupture still remains controversial. The objective of this study was to determine whether glucocorticoid has deleterious effects on the cellular metabolism and collagen production of cultured human tenocytes and the reversibility of these effects by platelet-derived growth factor-BB (PDGFBB).

METHODS

Primary cultures of human tenocytes obtained from explants of healthy patellar tendon, harvested during anterior cruciate ligament reconstructions, were performed. The effects on cell viability, cell proliferation, and induction of apoptosis were measured by [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, 5-bromo-deoxyuridine incorporation, and DNA fragmentation assay, respectively. The effect on collagen synthesis was measured by (3) H-proline incorporation assay.

RESULTS

The number of viable cells was decreased, in a dose-dependent manner, by the administration of 10 (-9) to 10 (-4) -M dexamethasone. This dose range also suppressed cell proliferation. No apoptotic effect was detected. Treatment with 10 (-6) -M dexamethasone significantly reduced the amount of collagen synthesis. Co-incubation with 10 ng/mL of PDGFBB significantly reversed the effects caused by 10 (-6) -M dexamethasone.

CONCLUSIONS

Dexamethasone significantly decreased cell viability, suppressed cell proliferation, and reduced collagen synthesis in cultured human tenocytes. The effects were reversed by the simultaneous administration of PDGFBB.

Glyceraldehyde-3-phosphate dehydrogenase expression varies with age and nutrition status

OBJECTIVE

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme in the glycolytic pathway, and it is a popular internal standard for northern blot analysis. We examined GAPDH expression early in life when feed is either provided or not provided to animals.

METHODS

Male broiler chickens were provided a standard starter diet plus Oasis nutritional supplement (fed group; Novus International, St. Louis, MO, USA) or no feed (starved group) for the first 3 d posthatch. Subsequently, the standard starter diet was provided to all chickens between 3 and 7 d posthatch. RNA was extracted from the pectoralis thoracicus, and GAPDH expression was evaluated with quantitative northern analysis.

RESULTS

GAPDH expression was significantly (P < 0.05) higher in the fed than in the starved group at 3 d posthatch, suggesting that nutritional manipulations can alter GAPDH transcription. Similarly, GAPDH mRNA levels were significantly (P < 0.05) higher at 7 d posthatch compared with all younger animals, suggesting that GAPDH is developmentally upregulated with advancing age.

CONCLUSION

GAPDH expression changes with age and nutrition status in the early posthatch chick, suggesting that GAPDH is not a proper internal standard for muscle studies using quantitative northern analysis.

Differentiating embryonic stem cells: GAPDH, but neither HPRT nor beta-tubulin is suitable as an internal standard for measuring RNA levels

Embryonic stem (ES) cells are pluripotent cell lines that possess virtually unlimited self-renewal and differentiation capacity. Such characteristics make them potentially an invaluable cell source for diverse tissue-engineering applications. In vitro ES cell differentiation occurs spontaneously in three-dimensional structures termed "embryoid bodies" that mimic postimplantation embryonic tissue. HPRT, beta-tubulin, and GAPDH are commonly used as internal RNA standards in ES cell-derived gene transcription studies so that corrected sample mRNA levels can be obtained for (semi) quantitative gene expression data. However, if reliable data is to be obtained, it is essential that such housekeeping gene expression remains constant, and this has not been demonstrated for differentiating ES cell cultures, which represent a mixed and changing population of cells with time in culture. Therefore, in the present study, we tested the suitability of these housekeeping genes to act as true internal standards for differentiating murine ES cells cultured as embryoid bodies. PCR-amplified gene-specific products were quantified from digital images of ethidium bromide-stained gels using a computer software package. Both HPRT and beta-tubulin mRNA levels varied markedly in spontaneously differentiating and growth factor-supplemented (TGF-beta) ES cell cultures (p < 0.001, ANOVA), while GAPDH expression remained relatively constant (p > 0.2). Our results demonstrate the importance of fully validating housekeeping gene expression in in vitro ES cell gene transcription studies and suggest that GAPDH may be a suitable candidate to act as an internal RNA standard, while both HPRT and beta-tubulin appear to be inappropriate. Finally, we demonstrate enhanced mesodermal differentiation of ES cell-derived cultures by treatment with TGF-beta through significant upregulation of Brachyury T expression, with a concomitant decrease in expression of the undifferentiated ES cell marker Oct-4.

Ribosomal 18S RNA prevails over glyceraldehyde-3-phosphate dehydrogenase and beta-actin genes as internal standard for quantitative comparison of mRNA levels in invasive and noninvasive human melanoma cell subpopulations

The comparison of the gene expression profiles between two subpopulations of melanoma cells (1C8 and T1C3) derived from the tumor of one patient by cDNA array revealed differences in GAPDH and beta-actin gene levels. These two housekeeping genes were up-regulated in invasive T1C3 melanoma cells compared to noninvasive 1C8 cells. Since cDNA array results were not confirmed by conventional RT-PCR throughout the exponential phase of amplification, we performed duplex relative RT-PCR using ribosomal 18S RNA as internal standard including competimer technology. Statistical analyses provided significant evidence that invasive T1C3 melanoma cells exhibited a twofold higher mRNA level of both GAPDH and beta-actin than noninvasive 1C8 cells. This study demonstrates that the duplex relative RT-PCR procedure including ribosomal 18S RNA as internal standard and competimer technology is precise for RNA quantification and is tailored for cDNA array validation. Our data provide molecular evidence that cellular subpopulations of the same pathological origin are highly heterogeneous and extend the concept that the selection of an appropriate internal control for comparative mRNA analysis should be adapted to each model of human cancers.

Dexamethasone induced cardiac hypertrophy in newborn rats is accompanied by changes in myosin heavy chain phenotype and gene transcription

Cardiac hypertrophy has been observed in newborn infants treated with dexamethasone (DEX). This study was undertaken to examine whether DEX-induced hypertrophy in newborn rats is associated with redistribution of cardiac myosin heavy chain (MHC) isoforms and, if so, the effects involve transcriptional regulation. Newborn rats were injected with either DEX (1 mg/kg/day; s.c.) or equivalent volume normal saline for 1, 3, 5, 7 or 9 days. Hypertrophy was quantified by heart dry/wet wt ratios, heart/body wt ratios, and total protein content of the myocardium. Changes in the expression of cardiac MHC mRNA were characterized by northern blot and slot blot analyses, using isoform specific probes for alpha- and beta-MHC genes. DEX effect on alpha-MHC gene transcription was analyzed by transiently transfecting various alpha-MHC promoter/CAT reporter constructs into primary cultures of cardiac myocytes derived from one day old rat pups. DEX administration into newborn rats produced significant cardiac hypertrophy ranging from 23% at day 1 to 59% at 9 days. The hypertrophy was accompanied by immediate increase (83%) in steady state level of the alpha-MHC mRNA within one day and a maximum increase (148%) at 7 days of treatment. The steady state level of beta-MHC mRNA declined by 25% at day 1 and a maximum decrease of 54% at day 7 of DEX treatment. The changes in MHC mRNA were also reflected in their protein levels as determined by V1 and V3 isozyme analysis. DEX treatment of primary cultures of cardiomyocytes following transfection with alpha-MHC promoter/CAT reporter constructs resulted in increased CAT expression in a dose dependent manner. The minimum alpha-MHC gene sequences responding to DEX treatment were located between the -200 to -74-bp region of the gene, resulting in 2-fold and 6-fold activation of CAT reporter after 0.05 and 0.1 mM doses of DEX, respectively. Our data indicate that DEX induced cardiac hypertrophy in newborn rats is accompanied by increased expression of alpha-MHC and decreased expression of beta-MHC. The alpha-MHC effects are mediated in part through transcriptional mechanisms.

Analysis of tyrosine hydroxylase gene transcription using an intron specific probe

The nuclear run-on assay is the most commonly used technique to determine transcription rates of specific genes such as tyrosine hydroxylase. Its application to studies in the nervous system is problematic, however, as a result of limitations in sensitivity and the loss of anatomical integrity. We observed that the relative levels of tyrosine hydroxylase intron 2-containing RNA using a ribonuclease protection assay in the adrenal medulla changed in response to pharmacological treatments consistently with changes shown by the nuclear run-on assay. Our results indicate that measures of tyrosine hydroxylase primary transcript levels offer an alternative to the nuclear run-on assay and validate the application of intron-specific in situ hybridization as a means of assessing the relative transcriptional activity of the tyrosine hydroxylase gene. Similar quantitative results were obtained using intron-specific in situ hybridization with oligonucleotide probes specific for rat tyrosine hydroxylase intron 2. Furthermore, we observed that intron-specific in situ hybridization could be used to measure tyrosine hydroxylase transcription rates in the locus coeruleus, providing resolution at the level of single neurons. Thus, measuring the levels of tyrosine hydroxylase intron 2 provides a sensitive measure of tyrosine hydroxylase transcription rate that can be applied to the study of brain catecholaminergic neurons.

Cloning and sequencing hybrid striped bass (Morone saxatilis x M. chrysops) transforming growth factor-beta (TGF-beta), and development of a reverse transcription quantitative competitive polymerase chain reaction (RT-qcPCR) assay to measure TGF-beta mRNA of teleost fish

A transforming growth factor (TGF)-beta was isolated and cloned from hybrid striped bass (Morone saxatilis x M. chrysops) anterior kidney mononuclear cells. This isolate (Genbank accession number AF140363) contains an open reading frame of 1146 bases coding for a 382 amino acid protein most similar to rainbow trout TGF-beta (57.3 and 78.6% identity with precursor and active protein, respectively) and rat TGF-beta 1 (41.1 and 68.8% identity with precursor and active protein, respectively). Consensus primers were demonstrated to amplify specifically by polymerase chain reaction (PCR), a TGF-beta segment from 14 species of teleost fish comprising 10 taxonomic families in 7 orders. A reverse transcription quantitative competitive polymerase chain reaction (RT-qcPCR) assay was devised to measure TGF-beta mRNA expression in teleost fish. Higher levels of TGF-beta mRNA expression were detected in mononuclear cells of peripheral blood than from spleen or anterior kidney.

Direct comparison of GAPDH, beta-actin, cyclophilin, and 28S rRNA as internal standards for quantifying RNA levels under hypoxia

The appropriate choice of an internal standard is critical for quantitative RNA analyses. As housekeeping genes, GAPDH, beta-actin, cyclophilin, and 28S rRNA are commonly employed as RNA internal standards with the assumption that their expression levels remain relatively constant in different experimental conditions. We tested this assumption under hypoxia (1% O2, 24 hours) compared to normoxia (20% O2, 24 hours) and compared RNA levels of these 4 housekeeping genes head to head using ribonuclease protection assays. Four biologically diverse cell lines with respect to clonal origin, neoplastic transformation, and growth rates were used in the comparison. Expression levels of 28S rRNA were constant, independent of O2 tension, but levels of GAPDH, beta-actin, and cyclophilin varied widely with hypoxia. In particular, GAPDH mRNA expression was increased by 21.2-75.1% under hypoxic conditions. Increased GAPDH transcription in hypoxia was correlated in the cancer cell lines with upregulation of the transcription factor Hypoxia Inducible Factor-1alpha protein levels in identical experimental conditions. These results suggest that 28S rRNA is a reliable internal control for comparative analyses of transcription under hypoxia; GAPDH appears particularly unfavorable for this purpose either in hypoxia or other experimental conditions that upregulate HIF-1alpha.

Indicators of delayed maturation of rat heart treated prenatally with dexamethasone

We investigated the effects of prenatal dexamethasone treatment on indicators of cardiac maturation: heart weight/body weight ratios, myosin heavy chain (MHC) expression, cell proliferation, and extracellular matrix. We administered dexamethasone, a synthetic glucocorticoid (approximately 48 microg/d, 3-wk slow release pellets), to pregnant rats (n = 8) beginning at 17 d postconception. Control dams were unmanipulated (n = 8). After approximately 4-5 d of dexamethasone exposure, hearts were collected from neonatal rats (12-24 h after birth). The prenatal dexamethasone treatment produced smaller pups with larger heart/body weight ratios, accompanied by a higher proliferative index and a reduction in extracellular matrix in the ventricles (with lowest values in the septal region) compared with control pups. We also report that, although there were no sex differences in body mass or heart and heart/body weight ratios, females had a greater proportion of cells synthesizing DNA in the heart. In addition, ventricles of male pups treated with dexamethasone contained lower levels of alpha-MHC mRNA, as reflected in a sex by treatment interaction. The changes in each parameter are consistent with delayed maturation. Our findings suggest that exposure to excess glucocorticoids in utero can affect cardiac development in potentially detrimental ways and that assessment of cardiac function should be closely monitored when such circumstances arise.

Pancreatic GAPDH gene expression during ontogeny and acute pancreatitis induced by caerulein

Recent studies indicated that expression of the housekeeping gene GAPDH is highly regulated during proliferation and differentiation. The objective of this study was to characterize by Northern blot the GAPDH mRNA expression in rat pancreas development and regeneration following acute pancreatitis induction by caerulein. Pancreatic GAPDH mRNA levels were the highest between fetal day 19 and the 11 postnatal day; they decreased to their lowest level after weaning on day 26. In acute pancreatitis, GAPDH mRNA levels were clearly increased 18 h after its initiation, were maximal during the first two days of induction and then decreased to control values after 9 days. These data demonstrate that overexpression of GAPDH may be implicated in pancreatic development, maturation and pancreas regeneration after acute pancreatitis.

Corticosteroids increase procollagen gene expression, synthesis, and secretion by human intestinal smooth muscle cells

BACKGROUND & AIMS

Collagen synthesis by smooth muscle cells plays an important role in intestinal fibrosis. Corticosteroids inhibit collagen synthesis in fibroblasts. The aim of this study was to examine the effect of corticosteroids on the expression of collagen by human intestinal smooth muscle (HISM) cells in vitro.

METHODS

Collagen synthesis was determined by the sensitivity of radiolabeled protein to collagenase. Secretion was determined by polyacrylamide gel electrophoresis of radiolabeled procollagen in the medium. Procollagen messenger RNA was determined by Northern blot analysis.

RESULTS

Collagen synthesis by confluent HISM cells was not affected by corticosteroids at 10(-10) to 10(-5) mol/L but, in subconfluent cultures, was nonspecifically increased 50% at 10(-5) mol/L. Procollagen secretion was nonspecifically increased 60% at 10(-6) mol/L dexamethasone without any effect on the type III/I ratio. Procollagen I and III messenger RNA levels responded in a biphasic manner: a 45%-65% increase at 10(-10) mol/L and a 15% and 30% decrease at 10(-8) and 10(-6) mol/L. In fibroblasts, collagen synthesis was inhibited 85% by dexamethasone, procollagen secretion was decreased 70%, the type III/I ratio decreased from 70:1 to 18:1, and procollagen messenger RNA was inhibited 25% and 60% (types I and III).

CONCLUSIONS

Collagen expression by HISM cells is refractory to corticosteroids and, at certain concentrations, is augmented.

Postnatal rat lung retinoic acid receptor (RAR) mRNA expression and effects of dexamethasone on RAR beta mRNA

Retinoids exert multiple effects upon lung differentiation and growth. Although the mechanisms involved are presently poorly understood, increasing evidence points to a central role of nuclear retinoic acid receptors (RAR). The purpose of this study was to determine RAR mRNA expression profile during postnatal alveolarization, compared with the expression in prenatal and adult rat lung, and to describe the effects of dexamethasone (DEX) and oxygen on postnatal lung RAR gene expression. Total RNA was isolated from lungs of Sprague-Dawley rats on prenatal day 19, on postnatal days 1, 3, 7, 10, and 14 of life, and from adults. One subgroup of littermate pups was treated with DEX daily for 3 or 7 days. In a second experiment, rats were exposed to room air or to 95% oxygen for 72 hours, and received either DEX or saline. Northern hybridization showed that the levels of all RAR subtypes in fetal lung were 45% or less of levels at postnatal day 1. The 3.7 kb RAR alpha transcript levels were lower than day 1 on days 10 and 14 (relative to day 1, day 10 = 0.54 +/- 0.05; day 14 = 0.54 +/- 0.08), but there was no change in a 2.7 kb RAR alpha transcript over this time period. By contrast, RAR beta mRNA levels were significantly higher at days 3, 10, and 14 compared with day 1 (day 3 = 1.79 +/- 0.19; day 10 = 1.41 +/- 0.14; day 14 = 1.53 +/- 0.05). Similarly, RAR gamma mRNA expression levels were higher on day 10 (1.45 +/- 0.09), but by day 14 there was no difference from day 1. Adult lung 3.7 kb RAR alpha, 2.7 kb RAR alpha, and RAR gamma were lower than day 1, but RAR beta was significantly greater (3.7 alpha = 0.52 +/- 0.05; 2.7 alpha = 0.49 +/- 0.26; gamma = 0.74 +/- 0.06; beta = 1.63 +/- 0.22). Treatment with DEX prevented the rise in RAR beta mRNA occurring on day 3 and significantly lowered (0.65 +/- 0.06) the amount of RAR beta mRNA in day 7 lung. Exposure of rat pups to oxygen caused an increase in RAR beta mRNA (1.21 +/- 0.03). DEX treatment again decreased RAR beta mRNA in both control (0.55 +/- 0.06) and oxygen-exposed pups (0.67 +/- 0.12). In addition, 2.7 kb RAR alpha mRNA was decreased with the combination of DEX and oxygen exposure (0.63 +/- 0.06). The differential gene expression profiles and the response to DEX and oxygen of the various members of the RAR family suggest that each subtype may have a specific role during the period of alveolarization in rat lung.

A fibroblast cell line cultured from a hypertrophic scar displays selective downregulation of collagen gene expression: barely detectable messenger RNA levels of the pro alpha 1(III) chain of type III collagen

The present study was designed to investigate the expression of type I, III and VI collagens by a fibroblast cell line initiated from a hypertrophic scar. The same tissue has previously been demonstrated to display markedly elevated expression of type I and III collagen mRNAs in vivo. Unexpectedly, slot-blot and Northern hybridizations revealed a barely detectable steady-state level of pro alpha 1(III) collagen chain mRNA in cultured hypertrophic scar fibroblasts. The levels of pro alpha 1(I) and alpha 2(VI) collagen chain mRNAs were essentially the same in fibroblasts cultured from hypertrophic scar and in fibroblasts cultured from normal skin. However, Northern blot analyses indicated that the ratio of 5.8 kb to 4.8 kb species of pro alpha 1(I) collagen mRNA was slightly reduced in fibroblasts originating from the hypertrophic scar compared to that in normal fibroblasts. When normal fibroblasts were incubated in conditioned medium from hypertrophic scar cultures, the expression of pro alpha 1(III) collagen chain mRNA decreased to a markedly lower level. Our studies suggest that collagen synthesis by fibroblasts in hypertrophic scars is stimulated by humoral factors which are active only in vivo. Furthermore, the results suggest that fibroblasts cultured from hypertrophic scar display a selective downregulation of different collagen genes and that this downregulation is exerted through an autocrine mechanism.

Low-dose glucocorticoids after in vitro fertilization and embryo transfer have no significant effect on pregnancy rate

OBJECTIVE

To determine the effect on pregnancy rate (PR) of low-dose glucocorticoid treatment in cycles without micromanipulation.

DESIGN

Randomized, prospective, double-blinded, placebo-controlled trial.

SETTING

One university-based tertiary infertility center and two private infertility centers.

PATIENTS

All patients receiving standard stimulation IVF-ET or transfer of cryopreserved embryos at the participating facilities from January to September 1993 were asked to participate in this study. Patients having micromanipulation were excluded from this study.

INTERVENTIONS

Participating patients were randomized to either 16 mg oral 6-alpha-methylprednisolone for four evenings starting the evening of retrieval or the evening before thawing cryopreserved embryos or to placebo administered in an identical fashion. Both groups were treated with 250 mg oral tetracycline four times per day starting with initiation of the study medication and continuing for 4 days. Cryopreservation and stimulation cycles were managed according to pre-established protocols for all patients. A clinical pregnancy was confirmed by an appropriately rising hCG titer and a gestational sac on ultrasound.

RESULTS

A total of 206 stimulation patients and 61 cryopreservation patients were randomized and had an ET. Patient characteristics were similar between groups. The clinical pregnancy and implantation rates between placebo and glucocorticoid groups were 35.9% versus 40.8% and 12.8% versus 11.7% for stimulation cycles and 30.3% versus 25% and 9.9% versus 7.4% for cryopreservation cycles, respectively. None of these differences were statistically significant.

CONCLUSIONS

Glucocorticoid plus antibiotic treatment at these doses for transfers of nonmicromanipulated embryos does not appear to have a significant effect on pregnancy or implantation rates.

Extended expression of cartilage components in experimental pseudoarthrosis

The healing of femoral fractures in an experimental rat pseudoarthrosis model was followed by studying the expression of cartilage specific genes coding for type II and X collagens and aggrecan, soft tissue and bone specific type I collagen, and decorin. Severe impairment of healing was observed with cartilage gene expression continuing until the seventh week and then declining rapidly. The abnormal healing pattern results in an inactive scar-like callus after the ninth week of healing even though house-keeping (e.g., GAPDH) genes are continuously expressed in the tissue. These results could be explained on the basis of continuous chondrogenic stimulus extending much beyond the normal range. If union is not achieved because of mechanical instability, signal of endochondral ossification persists until it becomes exhausted and callus at the fracture gap becomes an inactive fibrous scar. The disturbed matrix gene expression was confirmed by histology.