Keratin Gene Expression Research Articles

Expression Localization of the KRT32 Gene and Its Association of Genetic Variation with Wool Traits.

Changes in keratin gene expression and spatiotemporal regulation determine the compositional content and cellular localization of wool keratin, thereby affecting wool traits. Therefore, keratin gene family member 32 (KRT32) was selected for a study using RT-qPCR, immunofluorescence, and penta-primer amplification refractory mutation system (PARMS) techniques. The results showed that KRT32 mRNA was highly expressed in the skin and localized to the inner root sheath (IRS), outer root sheath (ORS) and dermal papilla (DP). Sequencing results identified eight SNPs in KRT32, and association analyses revealed that the variations were significantly associated with multiple traits in wool (p < 0.05), including MFD, CF and MFC. The constructed haplotype combination H2H3 has higher CF and smaller MFD than other haplotype combination (p < 0.05). In conclusion, KRT32 can be used as a candidate gene for molecular genetic improvement of wool in Gansu Alpine Fine-wool sheep.

A Kaleidoscope of Keratin Gene Expression and the Mosaic of Its Regulatory Mechanisms

Keratins are a family of intermediate filament-forming proteins highly specific to epithelial cells. A combination of expressed keratin genes is a defining property of the epithelium belonging to a certain type, organ/tissue, cell differentiation potential, and at normal or pathological conditions. In a variety of processes such as differentiation and maturation, as well as during acute or chronic injury and malignant transformation, keratin expression undergoes switching: an initial keratin profile changes accordingly to changed cell functions and location within a tissue as well as other parameters of cellular phenotype and physiology. Tight control of keratin expression implies the presence of complex regulatory landscapes within the keratin gene loci. Here, we highlight patterns of keratin expression in different biological conditions and summarize disparate data on mechanisms controlling keratin expression at the level of genomic regulatory elements, transcription factors (TFs), and chromatin spatial structure.

Seasonal Variability in Transcript Expression of Type I and Type II Keratins in Wool Follicles of Lustrous Fleece-Producing Magra Sheep

ABSTRACT Magra sheep reared around the Bikaner area of Rajasthan, India is famous for producing lustrous fleece as compared to other wool-producing native sheep breeds. Three clips of Magra wool, namely, February, July, and October months of the year are showing variations in luster and gross appearance. Present work has been conducted to unravel seasonal variations, in transcript expression patterns in major type I and type II keratin genes, that occur in wool follicles of lustrous wool-producing Magra sheep. Wool samples randomly collected were graded in high and low luster by Gloss 60° values. Wool follicles of the sheep with low (gloss 60° values; < 2.5) and high (gloss 60° values; > 2.5) luster were used for the analysis of type I and type II keratin transcripts. The results of Quantitative PCR had shown up-regulated expression of keratin genes in high-lustrous sheep as compared to low-lustrous sheep. K32, K40, and K82 transcript expression differed significantly (P ≤ .05) between high- and low-lustrous sheep. Nucleotide sequence analysis of the K40 and K82 genes revealed five and four non-synonymous mutations, respectively. From the present study, it can be speculated that the higher amount of keratin protein may play a crucial role in determining the luster property of the wool.

183 Reduced FLG expression in atopic eczema reduces expression of key barrier genes and increases BMP signalling

Filaggrin (FLG) is a key cornified envelope and epidermal barrier protein. FLG mutations are the most strongly implicated genetic risk factor for atopic eczema (AE). FLG is part of a gene complex, called the epidermal differentiation complex (EDC), the genes of which contribute to various aspects of epidermal barrier function. FLG siRNA knockdown in keratinocytes caused a global reduction in EDC and Keratin (KRT) gene expression concomitant with up-regulation of bone morphogenetic protein (BMP) signalling.

Revisiting the significance of keratin expression in complex epithelia.

A large group of keratin genes (n=54 in the human genome) code for intermediate filament (IF)-forming proteins and show differential regulation in epithelial cells and tissues. Keratin expression can be highly informative about the type of epithelial tissue, differentiation status of constituent cells and biological context (e.g. normal versus diseased settings). The foundational principles underlying the use of keratin expression to gain insight about epithelial cells and tissues primarily originated in pioneering studies conducted in the 1980s. The recent emergence of single cell transcriptomics provides an opportunity to revisit these principles and gain new insight into epithelial biology. Re-analysis of single-cell RNAseq data collected from human and mouse skin has confirmed long-held views regarding the quantitative importance and pairwise regulation of specific keratin genes in keratinocytes of surface epithelia. Furthermore, such analyses confirm and extend the notion that changes in keratin gene expression occur gradually as progenitor keratinocytes commit to and undergo differentiation, and challenge the prevailing assumption that specific keratin combinations reflect a mitotic versus a post-mitotic differentiating state. Our findings provide a blueprint for similar analyses in other tissues, and warrant a more nuanced approach in the use of keratin genes as biomarkers in epithelia.

Keratin 75 Is a Component of the LINC Complex and Has an Essential Role in Mediating the SOX2 Rapid Healing Response during Wound Repair

Keratin 75 Is a Component of the LINC Complex and Has an Essential Role in Mediating the SOX2 Rapid Healing Response during Wound Repair

A Proteomic Study of the Effect of N-acetylcysteine on the Regulation of Early Pregnancy in Goats.

Simple SummaryEarly pregnancy regulation is an extremely complex process that is influenced by various factors. We previously mined the differentially expressed genes affected by N-acetyl-L-cysteine (NAC) in early pregnancy in goats via transcriptome sequencing. We found that NAC increased the number of lambs by affecting the immune pathway in ewes and enhancing antioxidation. Based on this, we here explored the effect of NAC on early pregnancy in goats at the protein level. The results showed a difference in the expression of uterine keratin and increases in the levels of antioxidant indices and hormones in doe serum.Dietary supplementation with N-acetyl-L-cysteine (NAC) may support early pregnancy regulation and fertility in female animals. The purpose of this study was to investigate the effect of supplementation with 0.07% NAC on the expression of the uterine keratin gene and protein in Qianbei-pockmarked goats during early pregnancy using tandem mass spectrometry (TMT) relative quantitative proteomics. The results showed that there were significant differences in uterine keratin expression between the experimental group (NAC group) and the control group on day 35 of gestation. A total of 6271 proteins were identified, 6258 of which were quantified by mass spectrometry. There were 125 differentially expressed proteins (DEPs), including 47 upregulated and 78 downregulated proteins, in the NAC group. Bioinformatic analysis showed that these DEPs were mainly involved in the transport and biosynthesis of organic matter and were related to the binding of transition metal ions, DNA and proteins and the catalytic activity of enzymes. They were enriched in the Jak-STAT signalling pathway, RNA monitoring pathway, amino acid biosynthesis, steroid biosynthesis and other pathways that may affect the early pregnancy status of does through different pathways and thus influence early embryonic development. Immunohistochemistry, real-time quantitative PCR and Western blotting were used to verify the expression and localization of glial fibrillary acidic protein (GFAP) and pelota mRNA surveillance and ribosomal rescue factor (PELO) in uterine horn tissue. The results showed that both PELO and GFAP were localized to endometrial and stromal cells, consistent with the mass spectrometry data at the transcriptional and translational levels. Moreover, NAC supplementation increased the levels of the reproductive hormones follicle-stimulating hormone (FSH), luteinizing hormone (LH), oestradiol (E2), progesterone (P4), superoxide dismutase (SOD), glutamate peroxidase (GSH-Px) and nitric oxide (NO) in the serum of does. These findings provide new insight into the mechanism by which NAC regulates early pregnancy and embryonic development in goats.

Dynamic changes in protein concentrations of keratins in crop milk and related gene expression in pigeon crops during different incubation and chick rearing stages

ABSTRACT 1. The objective of this study was to examine the keratin composition of crop milk, the variation of epithelial thickness and keratin (K) gene expression in samples from young pigeon during incubation and chick rearing. 2. Crop milk was collected from 1-, 3- and 5-day-old squab crops for keratin content analysis. Results showed that K4 accounted for the highest proportion of all detected keratins. 3. In total, 42 pairs of adult pigeons were allocated to seven groups according to different stages to collect crop samples. Gene expression studies showed that the K3 gene expression was maximised at rearing Day 15 (15) and R1 in males and females, respectively. K6a gene level was the greatest at R15 in females, whereas it peaked at incubation Day 4 (I4) in males. The K12, K13, K23 and K80 gene levels were inhibited at the peak period of crop milk formation in comparison with I4. In females, K cochleal expression peaked at I10, whereas it was the greatest at R25 in males. K4 and K14 gene expression was the highest at I10 in females, while K4 and K14 were minimised at I17 and R7 in males, respectively. Gene expressions of K5, K8, K19 and K20 in males and K19 in females were maximised at R1. The K5, K20 and K75 gene levels in females peaked at R7. K75 and K8 expressions in males and females reached a maximum value at R25 and I17, respectively. 4. The epithelial thickness of male and female crops reached their greatest levels at R1 and had the highest correlation with K19. 5. These results emphasised the importance of keratinisation in crop milk formation, and different keratins probably play various roles during this period. The K19 was probably a marker for pigeon crop epithelium development. The sex of the parent pigeon affected keratin gene expression profiles.

Essential Role of STAT3 Signaling in Hair Follicle Homeostasis

Dominant-negative mutations associated with signal transducer and activator of transcription 3 (STAT3) signaling, which controls epithelial proliferation in various tissues, lead to atopic dermatitis in hyper IgE syndrome. This dermatitis is thought to be attributed to defects in STAT3 signaling in type 17 helper T cell specification. However, the role of STAT3 signaling in skin epithelial cells remains unclear. We found that STAT3 signaling in keratinocytes is required to maintain skin homeostasis by negatively controlling the expression of hair follicle-specific keratin genes. These expression patterns correlated with the onset of dermatitis, which was observed in specific pathogen-free conditions but not in germ-free conditions, suggesting the involvement of Toll-like receptor-mediated inflammatory responses. Thus, our study suggests that STAT3-dependent gene expression in keratinocytes plays a critical role in maintaining the homeostasis of skin, which is constantly exposed to microorganisms.

604 DNA dioxygenases TET regulate keratin gene expression and enhancer networks within lineage-specific gene loci during epidermal and hair follicle-specific keratinocyte differentiation

604 DNA dioxygenases TET regulate keratin gene expression and enhancer networks within lineage-specific gene loci during epidermal and hair follicle-specific keratinocyte differentiation

Whole genome sequencing identifies novel genetic mutations in patients with eczema herpeticum.

Eczema herpeticum (EH) is a rare complication of atopic dermatitis (AD) caused by disseminated herpes simplex virus (HSV) infection. The role of rare and/or deleterious genetic variants in disease etiology is largely unknown. This study aimed to identify genes that harbor damaging genetic variants associated with HSV infection in AD with a history of recurrent eczema herpeticum (ADEH+). Whole genome sequencing (WGS) was performed on 49 recurrent ADEH+ (≥3 EH episodes), 491 AD without a history of eczema herpeticum (ADEH-) and 237 non-atopic control (NA) subjects. Variants were annotated, and a gene-based approach (SKAT-O) was used to identify genes harboring damaging genetic variants associated with ADEH+. Genes identified through WGS were studied for effects on HSV responses and keratinocyte differentiation. Eight genes were identified in the comparison of recurrent ADEH+to ADEH-and NA subjects: SIDT2, CLEC7A, GSTZ1, TPSG1, SP110, RBBP8NL, TRIM15, and FRMD3. Silencing SIDT2 and RBBP8NL in normal human primary keratinocytes (NHPKs) led to significantly increased HSV-1 replication. SIDT2-silenced NHPKs had decreased gene expression of IFNk and IL1b in response to HSV-1 infection. RBBP8NL-silenced NHPKs had decreased gene expression of IFNk, but increased IL1b. Additionally, silencing SIDT2 and RBBP8NL also inhibited gene expression of keratinocyte differentiation markers keratin 10 (KRT10) and loricrin (LOR). SIDT2 and RBBP8NL participate in keratinocyte's response to HSV-1 infection. SIDT2 and RBBP8NL also regulate expression of keratinocyte differentiation genes of KRT10 and LOR.

Epidermal Renewal after Treatment of Primary Canine Hypothyroidism using Levothyroxine

Background: Primary canine hypothyroidism, an endocrine disorder that causes imbalances in the hypothalamus-pituitarythyroid axis, is a common cause of endocrine dermatoses, which frequently presents with opaque dry brittle hair. Tissue changes are also visible, such as myxedema, hyperkeratosis, epidermal atrophy, alopecia, and others. This paper describes the skin changes caused by primary hypothyroidism in a female dog before and after treatment with levothyroxine.Case: This case study involved a 7-year-old Dalmatian bitch with a history of weight gain and changes such as rough dry brittle hair. For about a year, the dog also had also presented symmetrical erythematous and alopecia skin lesions in the regions of the hind limbs, lower back and tail, progressive lethargy and fatigue after exercise. A hemogram showed mild normocytic and normochromic regenerative anemia, as well as mild leukopenia and neutropenia. Biochemical tests revealed increased levels of creatinine, total cholesterol, and triglycerides. Skin biopsy revealed the presence of comedones in the epidermis and acanthosis and trichilemmal keratinization. Hormonal tests revealed high TSH and low free T4 and total T4 levels. A cervical ultrasound scan showed changes in the thyroid glands, with hypoechoic parenchyma, in addition to increased size of the right lobe, suggesting thyroiditis. Based on these exams, the patient was diagnosed with primary hypothyroidism, and treatment with levothyroxine was instituted.Discussion: Around 90% of dogs with hypothyroidism show a decrease in total T4 and about 65-75% of them show an increase in TSH levels. In endocrinopathy, there is a decrease in the expression of T3 receptors in the keratinocytes and genes responsible for epidermal renewal. Also, molecules that affect epidermal differentiation bind to intracellular receptors belonging to the steroid/thyroid hormone superfamily. In this study, however, the application of the minimum levothyroxine dose restored the normal epidermal pattern for the species and the remaining parameters returned to normal. The hormone T3 acts in the differentiation of keratinocytes, a fact that, although not yet proven, is believed to be indirect and mediated by the epidermal growth factor or by the expression of the genes responsible for the renewal of the epidermis. Besides, some effects on the epidermis caused by deficiency of thyroid hormones may be due to secondary vitamin A deficiency, which is necessary for epithelial differentiation and binding epidermal growth factor (EGF) to the cell. Still, there is a theory that sex hormones also affect the differentiation of the epidermis, as studies show that deficiency causes effects similar to those caused by hypothyroidism. Some studies indicate the investigation of the relationship between secondary vitamin D deficiency and the increased cellularity of the epidermis of the spayed hypothyroid female rats. Additionally, the mechanism of the formation of hyperkeratosis in hypothyroidism is not yet elucidated. T3 is known to regulate keratingene expression and perhaps also epidermal maturation, epithelial cycle, and normal keratin synthesis. The single treatment with levothyroxine in the female dog was effective in promoting the restoration of gene expression to T3 in keratinocytes.Keywords: dermatopathies, endocrinopathies, hypothyroidism, levothyroxine, synthetic hormone.

Differential gene expression in skin RNA of horses affected with degenerative suspensory ligament desmitis

BackgroundEquine degenerative suspensory ligament desmitis (DSLD) is a systemic connective tissue disorder first identified in Peruvian Paso horses but afflicting other horse breeds as well. Inappropriate accumulation of proteoglycans in connective tissues, most prominently in tendons and ligaments, leads to progressive and debilitating lameness and pain. It is largely unknown what drives the overproduction of proteoglycans, but our previous studies suggest involvement of bone morphogenetic protein 2 (BMP2), a member of the transforming growth factor-β (TGFβ) family, impacting synthesis of proteoglycans. To identify potential players in pathogenesis of DSLD a new approach utilizing next generation sequencing was undertaken.MethodsNext generation sequencing was performed using RNA extracted from skin biopsies of six control Peruvian Pasos and six horses with DSLD (4 Peruvian Pasos and 2 warmbloods). The CuffDiff result sets were validated with algorithms used to run them. This was based on the determined false discovery rates derived from the P values adjusted for multiple testing for any given result.ResultsBioinformatics analysis of transcriptomes revealed differential expression of over 1500 genes, including increased expression of genes for several growth factors (most prominently BMP2, FGF5, CTGF, many members of the EGF family), and mediators of signaling (Fos, Myc, MAPK system), and keratins. Two genes encoding for enzymes involved in synthesis of hyaluronan were also overexpressed. Gene expression was decreased for protein cores of many proteoglycans, several growth factors, most collagens, and many peptides with immune function.ConclusionsThe overexpression of BMP2 correlates well with our previous data. However, the decrease in expression of numerous proteoglycans was unexpected. A mutation in a gene of a less characterized proteoglycan and/or glycosyltransferase with subsequent increased production of hyaluronan and/or a proteoglycan(s) undetected in our study could account for the systemic proteoglycan deposition. Decreased collagen gene expression indicates abnormal connective tissue metabolism. The increased expression of keratin genes and FGF5 supports reports of skin abnormalities in DSLD. Underexpression of immune function genes corresponds with lack of inflammation in DSLD tissues. Finally, though the proteoglycan and/or glycosaminoglycan abundant in DSLD has not been identified, we validated our previous data, including overexpression of BMP2, and systemic nature of DSLD due to disturbed metabolism of the extracellular matrix.

764 DNA dioxygenases Tet1/2/3 control hair matrix keratinocyte differentiation and hair shaft shape via regulation of hair keratin gene expression

764 DNA dioxygenases Tet1/2/3 control hair matrix keratinocyte differentiation and hair shaft shape via regulation of hair keratin gene expression

Skin transcriptome reveals the periodic changes in genes underlying cashmere (ground hair) follicle transition in cashmere goats

BackgroundCashmere goats make an outstanding contribution to the livestock textile industry and their cashmere is famous for its slenderness and softness and has been extensively studied. However, there are few reports on the molecular regulatory mechanisms of the secondary hair follicle growth cycle in cashmere goats. In order to explore the regular transition through the follicle cycle and the role of key genes in this cycle, we used a transcriptome sequencing technique to sequence the skin of Inner Mongolian cashmere goats during different months. We analyzed the variation and difference in genes throughout the whole hair follicle cycle. We then verified the regulatory mechanism of the cashmere goat secondary hair follicle growth cycle using fluorescence quantitative PCR.ResultsThe growth cycle of cashmere hair could be divided into three distinct periods: a growth period (March–September), a regression period (September–December), and a resting period (December–March). The results of differential gene analyses showed that March was the most significant month. Cluster analysis of gene expression throughout the whole growth cycle further supported the key nodes of the three periods of cashmere growth, and the differential gene expression of keratin corresponding to the ground haircashmere growth cycle further supported the results from tissue slices. Quantitative fluorescence analysis showed that KAP3–1, KRTAP 8–1, and KRTAP 24–1 genes had close positive correlation with the cashmere growth cycle, and their regulation was consistent with the growth cycle of cashmere.ConclusionThe growth cycle of cashmere cashmere could be divided into three distinct periods: a growth period (March–September), a regression period (September–December) and a resting period (December–March). March was considered to be the beginning of the cycle. KAP and KRTAP showed close positive correlation with the growth cycle of secondary hair follicle cashmere growth, and their regulation was consistent with the cashmere growth cycle. But hair follicle development-related genes are expressed earlier than cashmere growth, indicating that cycle regulation could alter the temporal growth of cashmere. This study laid a theoretical foundation for the study of the cashmere development cycle and provided evidence for key genes during transition through the cashmere cycle. Our study provides a theoretical basis for cashmere goat breeding.

Epithelial differentiation of human adipose-derived stem cells (hASCs) undergoing three-dimensional (3D) cultivation with collagen sponge scaffold (CSS) via an indirect co-culture strategy

BackgroundThree-dimensional (3D) cultivation with biomaterials was proposed to facilitate stem cell epithelial differentiation for wound healing. However, whether human adipose-derived stem cells (hASCs) on collagen sponge scaffold (CSS) better differentiate to keratinocytes remains unclear.Methods3D cultivation with CSS on hASC epidermal differentiation co-cultured with HaCaT cells at air-liquid interface (ALI) was compared with two-dimensional (2D) form and cultivation without “co-culture” or “ALI.” Cellular morphology, cell adhesion, and growth condition were evaluated, followed by the protein and gene expression of keratin 14 (K14, keratinocyte specific marker).ResultsTypical cobblestone morphology of keratinocytes was remarkably observed in co-cultured hASCs at ALI, but those seeded on the CSS exhibited more keratinocyte-like cells under an invert microscope and scanning electron microscope. Desired cell adhesion and proliferation were confirmed in 3D differentiation groups by rhodamine-labeled phalloidin staining, consistent with H&E staining. Compared with those cultured in 2D culture system or without “ALI,” immunofluorescence staining and gene expression analysis revealed hASCs co-cultured over CSS expressed K14 at higher levels at day 15.ConclusionsCSS is positive to promote epithelial differentiation of hASCs, which will foster a deeper understanding of artificial dermis in skin wound healing and regeneration.

Expression profiling revealed keratins and interleukins as potential biomarkers in squamous cell carcinoma of horn in Indian bullocks (Bos indicus).

Horn cancer is most prevalent in Bos indicus and poorly defined genetic landscape makes disease diagnosis and treatment difficult. In this study, RNA-Seq and data analysis using CLC Genomics Workbench was employed to identify biomarkers associated with horn cancer. As a result, a total of 149 genes were found significant differentially expressed in horn cancer samples compared to horn normal samples. The study revealed 'keratins' and 'interleukins' as apex groups of significant differentially expressed genes (DEGs). Functional analysis showed that the upregulated keratins support metastasis of tumor via cell proliferation, migration, and affecting cell stability, while downregulated interleukins along with other associated chemokine receptors deprive the immune response to tumor posing clear path for metastasis of horn cancer. Combi-action of both the group facilitates the tumor microenvironment to reproduce tumorigenesis. Analysis of pathways enriched in DEGs and exemplified protein-protein interaction network indicated actual role of DEGs in horn cancer at a fine level. Important effect of deregulated expression of keratin and interleukin genes in horn cancer enrolling their candidacy as potential biomarkers for horn cancer prognosis. This study appraises the possibility to mitigate horn cancer at fine resolution to extract attainable identification of prognostic molecular portraits.

A loss of estrogen signaling in the aromatase deficient mouse penis results in mild hypospadias

Hypospadias is the abnormal opening of the urethra on the underside of the penis and occurs in approximately 1/125 live male births worldwide. The incidence rate of hypospadias has dramatically increased over the past few decades. This is now attributed, at least in part, to our exposure to endocrine-disrupting chemicals (EDCs) which alter the hormonal signals required for development of the penis. In humans androgens are the main drivers of fusion of the urethral folds to form the urethra within the shaft of the penis, a process required for termination of the urethra in its normal location at the tip of the penis. However, recent research has suggested that estrogen also plays a role in this process. To better understand how EDCs impact urethral development it is essential that we understand the normal function of hormones during development of the penis. To define the role of estrogen in urethral development we examined development of the penis in the aromatase (Cyp19a1) Knockout (ArKO) mouse strain in which endogenous estrogen production is completely ablated. We found that the ArKO penis had a mild hypospadias phenotype. The developing ArKO postnatal penis displayed an early disruption in preputial development, which likely causes the mild hypospadias observed in adults. Using qPCR, we found altered expression of keratin genes and key urethral patterning genes in response to the disrupted estrogen signaling. The hypospadias phenotype was almost identical to that reported for the estrogen receptor α (ERα) knockout confirming that ERα is the predominant receptor for mediating estrogen action during development of the mouse penis. Our results show that estrogen is required for normal prepucial development and placement of the mature urethral opening at the distal aspect of the penis. We also identified several genes which are potential downstream targets of estrogen during normal urethral closure. With this knowledge, we can now better understand how anti-estrogenic as well as estrogenic EDCs disrupt urethral closure to cause mild hypospadias in both mice and humans.

Keratin Gene Expression Differences in Wool Follicles and Sequence Diversity of High Glycine-Tyrosine Keratin-Associated Proteins (Kaps) in Magra Sheep of India

ABSTRACT Wool fibers consist of proteins with majority belongs to keratin family. Longitudinally arrayed keratin intermediate filaments constitute a matrix surrounded by keratin-associated proteins (KAPs). These KAPs play essential role in providing the physico-mechanical properties of the wool fiber. Real time PCR assay revealed that type 1 hair cortex keratin K33A (K1.2) was significantly (p ≤ 0.05) upregulated in lustrous Magra wool follicles however other keratin and keratin associated protein (KAP) genes were found down regulated. Furthermore, nucleotide sequence analysis revealed 4, 30, and 7 single nucleotide polymorphisms (SNPs) in KAP6, KAP7, and KAP8 genes, respectively. The presence of differing amount of type I and type II keratin and hydrophobic high glycine-tyrosine proteins in wool might be partially responsible for different glass transitions exhibited by wool and consequently imparts different physical properties like wool luster.

Gene expression profile associated with thymus regeneration in dexamethasone-treated beef cattle

Glucocorticoids (GCs) are illegally used as growth promoters in cattle, and the analytical methods officially applied most likely underestimate the precise frequency of the abuse. As a side effect, the administration of GCs causes fat infiltration, apoptosis, and atrophy of the thymus. However, gross and histological observations carried out previously showed that the thymus preserves an intrinsic ability to regenerate. The aim of this work was to study the transcriptional effects of GCs on genes likely involved in regeneration of the epithelial cell network in the cervical and thoracic thymus of beef cattle treated with dexamethasone (DEX) or prednisolone (PRD) in comparison with a control group. Moreover, the ratio of bax/bcl2 genes was examined to verify a possible antiapoptotic activity occurring at the same time. In the cervical thymus, DEX administration increased the gene expression of c-myc (P < 0.01), tcf3 (P < 0.05), tp63 (P < 0.01), and keratin 5 (krt5; P < 0.01). In the thoracic thymus of DEX-treated cattle, the gene expression of tcf3 (P < 0.01), tp63 (P < 0.01), and krt5 (P < 0.05) was increased. These results suggested that thymic regeneration is underway in the DEX-treated animals. However, the bax/bcl2 ratio was decreased in both cervical and thoracic thymus of DEX-treated cattle (P < 0.01 and P < 0.05, respectively), showing an antiapoptotic effect through the mitochondrial pathway. Conversely, PRD administration caused no change in the expression of all considered genes. These results sustain the hypothesis that regeneration occurs in the thymus parenchyma 6 d after the DEX treatment was discontinued. This hypothesis is also supported by the absence of alterations in the thymus of PRD-treated beef cattle. Indeed, previous studies showed the inability of PRD to induce macroscopic and microscopic lesions in the thymus. Therefore, in this context, it is not surprising that PRD induced no alteration of genes involved in the regeneration pathway.