Selenium deficiency and fulvic acid supplementation induces fibrosis of cartilage and disturbs subchondral ossification in knee joints of mice: an animal model study of Kashin-Beck disease

Nano-elemental selenium particle developed via supramolecular self-assembly of chondroitin sulfate A and Na2SeO3 to repair cartilage lesions

Cartilage repair is a significant clinical issue due to its restricted ability to regenerate and self-heal after cartilage lesions or degenerative disease. Herein, a nano-elemental selenium particle (chondroitin sulfate A‑selenium nanoparticle, CSA-SeNP) is developed by the supramolecular self-assembly of Na₂SeO₃ and negatively charged chondroitin sulfate A (CSA) via electrostatic interactions or hydrogen bonds followed by in-situ reducing of l-ascorbic acid for cartilage lesions repair. The constructed micelle exhibits a hydrodynamic particle size of 171.50 ± 2.40 nm and an exceptionally high selenium loading capacity (9.05 ± 0.03 %) and can promote chondrocyte proliferation, increase cartilage thickness, and improve the ultrastructure of chondrocytes and organelles. It mainly enhances the sulfation modification of chondroitin sulfate by up-regulating the expression of chondroitin sulfate 4-O sulfotransferase-1, -2, -3, which in turn promotes the expression of aggrecan to repair articular and epiphyseal-plate cartilage lesions. The micelles combine the bio-activity of CSA with selenium nanoparticles (SeNPs), which are less toxic than Na₂SeO₃, and low doses of CSA-SeNP are even superior to inorganic selenium in repairing cartilage lesions in rats. Thus, the developed CSA-SeNP is anticipated to be a promising selenium supplementation preparation in clinical application to address the difficulty of healing cartilage lesions with outstanding repair effects.

The Localized Ionic Microenvironment in Bone Modelling/Remodelling: A Potential Guide for the Design of Biomaterials for Bone Tissue Engineering

Bone is capable of adjusting size, shape, and quality to maintain its strength, toughness, and stiffness and to meet different needs of the body through continuous remodeling. The balance of bone homeostasis is orchestrated by interactions among different types of cells (mainly osteoblasts and osteoclasts), extracellular matrix, the surrounding biological milieus, and waste products from cell metabolisms. Inorganic ions liberated into the localized microenvironment during bone matrix degradation not only form apatite crystals as components or enter blood circulation to meet other bodily needs but also alter cellular activities as molecular modulators. The osteoinductive potential of inorganic motifs of bone has been gradually understood since the last century. Still, few have considered the naturally generated ionic microenvironment's biological roles in bone remodeling. It is believed that a better understanding of the naturally balanced ionic microenvironment during bone remodeling can facilitate future biomaterial design for bone tissue engineering in terms of the modulatory roles of the ionic environment in the regenerative process.

Long-Term Selenium-Yeast Supplementation Does Not Affect Bone Turnover Markers: A Randomized Placebo-Controlled Trial

Higher selenium status has been associated with lower bone turnover markers (BTM) in epidemiological studies. However, the long-term impact of selenium supplementation on BTMs has not been studied. We investigated the effects of selenium supplementation on BTMs including osteocalcin (OC), procollagen type I N-terminal propeptide (PINP), collagen type I cross-linked C-telopeptide (CTX), and bone alkaline phosphatase (BALP) in the short (6 months) and long term (5 years). A total of 481 Danish men and women (60-74 years) were randomized to receive placebo-yeast versus 100, 200, or 300 μg selenium as selenium-enriched yeast daily for 5 years. Plasma selenium concentration was measured using inductively coupled plasma mass spectrometry, and BTMs were measured in nonfasted samples at baseline, 6 months, and 5 years. Data were analyzed by ANCOVA to investigate the shape of the dose-response relationships. Covariates included age, body mass index, baseline selenium status, baseline BTM, smoking, alcohol, supplement use, and medication. Plasma selenium concentration (mean 86.5 μg/d at baseline) increased significantly with increasing selenium supplementation to 152.6, 209.1, and 253.7 μg/L after 6 months and remained elevated at 5 years (158.4, 222.4, and 275.9 μg/L for 100, 200, and 300 μg supplemental selenium/d, respectively (p < 0.001)). There was no change in plasma selenium concentration in the placebo-treated group. There was no significant effect of selenium supplementation on OC (6 months p = 0.37; 5 years p = 0.63), PINP (6 months p = 0.37; 5 years p = 0.79), CTX (6 months p = 0.91; 5 years p = 0.58) or BALP (6 months p = 0.17; 5 years p = 0.53). The relatively replete baseline selenium status in the study participants may explain this lack of effect. Testing in more deficient populations may provide further insights into the impact of selenium supplementation on bone health. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons

The main etiological mechanism for Kashin-Beck disease (KBD) is deep chondrocyte necrosis induced by environmental risk factors (ERFs). The scholars have conducted several epidemiological, cellular, and animal model studies on ERFs. Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound etiology theory hypothesis. The animal models of KBD have been replicated based on the previous etiological hypotheses. The different species of animals (monkey, rat, dog, pig, chicken, and rabbit) were treated with different ERFs interventions, and the clinical manifestations and pathological changes of articular cartilages were observed. The animals in the experimental group were fed with endemic water, endemic grain, low nutrition, thallium sulfate, FA, Se, T-2 toxin, and iodine. The dose of thallium sulfate was 1154 μg/d; the doses range of FA were 5, 50, 150, 200, and 211 mg/kg; the doses range of Se were 0.00035, 0.00175, 0.005, 0.02, 0.031, 0.1, 0.15, 0.314, 0.5, and 10 mg/kg; the doses range of T-2 toxin were 40, 100, 200, 600, 1000, 1500, 3000, 6000, and 9000 ng/g; and the doses range of iodine were 0.04, 0.18, and 0.4-0.5 μg/g. The sample size ranged from 9 to 230 depending on the interventions and grouping; the follow-up duration ranged from 1 week to 18 months. Moreover, the methods and comparisons of different animal models of KBD had been summarized to provide a useful basis for studying the pathogenesis of KBD. In conclusion, the rhesus monkeys administrated endemic water and grain were susceptible animals to replicate KBD. The rats treated with T-2 toxin combined with Se/nutrition deficiency could be a suitable and widely used animal model.

Selenophosphate synthetase 1 deficiency exacerbates osteoarthritis by dysregulating redox homeostasis

Aging and mechanical overload are prominent risk factors for osteoarthritis (OA), which lead to an imbalance in redox homeostasis. The resulting state of oxidative stress drives the pathological transition of chondrocytes during OA development. However, the specific molecular pathways involved in disrupting chondrocyte redox homeostasis remain unclear. Here, we show that selenophosphate synthetase 1 (SEPHS1) expression is downregulated in human and mouse OA cartilage. SEPHS1 downregulation impairs the cellular capacity to synthesize a class of selenoproteins with oxidoreductase functions in chondrocytes, thereby elevating the level of reactive oxygen species (ROS) and facilitating chondrocyte senescence. Cartilage-specific Sephs1 knockout in adult mice causes aging-associated OA, and augments post-traumatic OA, which is rescued by supplementation of N-acetylcysteine (NAC). Selenium-deficient feeding and Sephs1 knockout have synergistic effects in exacerbating OA pathogenesis in mice. Therefore, we propose that SEPHS1 is an essential regulator of selenium metabolism and redox homeostasis, and its dysregulation governs the progression of OA.

Osteoarthritis is caused by the gradual accumulation of oxidative stress in cartilage. Here, the authors show that dysregulation of the selenium metabolic pathway underlies a shift in redox homeostasis in chondrocytes, leading to chronic osteoarthritic changes in joints.

Dysregulation of Cells Cycle and Apoptosis in Human Induced Pluripotent Stem Cells Chondrocytes Through p53 Pathway by HT-2 Toxin: An in vitro Study

Kashin–Beck disease (KBD) mainly damages growth plate of adolescents and is susceptible to both gene and gene–environmental risk factors. HT-2 toxin, which is a primary metabolite of T-2 toxin, was regarded as one of the environmental risk factors of KBD. We used successfully generated KBD human induced pluripotent stem cells (hiPSCs) and control hiPSCs, which carry different genetic information. They have potential significance in exploring the effects of HT-2 toxin on hiPSC chondrocytes and interactive genes with HT-2 toxin for the purpose of providing a cellular disease model for KBD. In this study, we gave HT-2 toxin treatment to differentiating hiPSC chondrocytes in order to investigate the different responses of KBD hiPSC chondrocytes and control hiPSC chondrocytes to HT-2 toxin. The morphology of HT-2 toxin-treated hiPSC chondrocytes investigated by transmission electron microscope clearly showed that the ultrastructure of organelles was damaged and type II collagen expression in hiPSC chondrocytes was downregulated by HT-2 treatment. Moreover, dysregulation of cell cycle was observed; and p53, p21, and CKD6 gene expressions were dysregulated in hiPSC chondrocytes after T-2 toxin treatment. Flow cytometry also demonstrated that there were significantly increased amounts of late apoptotic cells in KBD hiPSC chondrocytes and that the mRNA expression level of Fas was upregulated. In addition, KBD hiPSC chondrocytes presented stronger responses to HT-2 toxin than control hiPSC chondrocytes. These findings confirmed that HT-2 is an environmental risk factor of KBD and that p53 pathway interacted with HT-2 toxin, causing damaged ultrastructure of organelles, accelerating cell cycle in G1 phase, and increasing late apoptosis in KBD hiPSC chondrocytes.

The role of selenium metabolism and selenoproteins in cartilage homeostasis and arthropathies

As an essential nutrient and trace element, selenium is required for living organisms and its beneficial roles in human health have been well recognized. The role of selenium is mainly played through selenoproteins synthesized by the selenium metabolic system. Selenoproteins have a wide range of cellular functions including regulation of selenium transport, thyroid hormones, immunity, and redox homeostasis. Selenium deficiency contributes to various diseases, such as cardiovascular disease, cancer, liver disease, and arthropathy—Kashin–Beck disease (KBD) and osteoarthritis (OA). A skeletal developmental disorder, KBD has been reported in low-selenium areas of China, North Korea, and the Siberian region of Russia, and can be alleviated by selenium supplementation. OA, the most common form of arthritis, is a degenerative disease caused by an imbalance in matrix metabolism and is characterized by cartilage destruction. Oxidative stress serves as a major cause of the initiation of OA pathogenesis. Selenium deficiency and dysregulation of selenoproteins are associated with impairments to redox homeostasis in cartilage. We review the recently explored roles of selenium metabolism and selenoproteins in cartilage with an emphasis on two arthropathies, KBD and OA. Moreover, we discuss the potential of therapeutic strategies targeting the biological functions of selenium and selenoproteins for OA treatment.

Selenium, a micronutrient found in brazil nuts, shiitake mushrooms, and most meats, may aid in treating joint diseases, including the most common form of arthritis, osteoarthritis (OA). In addition to thyroid hormone metabolism and immunity, selenium is important in antioxidant defense. Oxidative damage can destroy cartilage and harm joints, and selenium deficiency is implicated in several joint diseases. Jin-Hong Kim at Seoul National University in South Korea and co-workers reviewed selenium metabolism, focusing on OA and and Kashin–Beck disease, a skeletal development disorder prevalent in selenium-deficient areas of northeast Asia. They report that selenium-containing proteins protect cells against oxidative damage and that selenium is crucial to cartilage production. Further investigation of selenium metabolism may point the way to new treatments for OA and other joint diseases.

RNA-seq analysis reveals different gene ontologies and pathways in rheumatoid arthritis and Kashin-Beck disease

AIMS

To understand the pathogenesis of cartilage damage in Kashin-Beck disease (KBD) and rheumatoid arthritis (RA) which similar clinical symptoms.

METHODS

RNA sequencing (RAN-seq) analysis was used to reveal the different pathogeneses between KBD and RA. The messenger RNA expression profiles of articular cartilage isolated from KBD patients (n = 3) and RA patients (n = 3) were compared using RNA-seq analysis. Differentially expressed genes (DEGs) were determined using the Benjamini-Hochberg approach. The Database for Annotation, Visualization and Integrated Discovery (DAVID 6.7) was employed to assess functional categories and Gene Ontology (GO). The Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology Based Annotation System (KOBAS 2.0) was used to identify significantly enriched KEGG pathways.

RESULTS

In the individually sequenced dataset, we identified 1568 significant DEGs in KBD compared to RA (232 up-regulated genes and 1336 down-regulated genes). GO function analysis identified nine significant biological processes (BPs), eight molecular functions (MFs), and five cell components (CCs) in KBD, and also the top ten ranked significant BPs, MFs and CCs were found in RA. The KEGG pathway enrichment analysis identified biosynthesis of amino acids involved in KBD. The chemokine signaling pathway, nuclear factor-kappa B signaling pathway, B cell receptor signaling pathway, leukocyte transendothelial migration, and osteoclast differentiation were involved in RA.

CONCLUSIONS

RNA-seq revealed that proteoglycan-mediated metabolic disorders contributed to the onset of KBD, whereas immune dysregulation was apparently involved in the pathogenesis of RA.

Changes in Trace Element Contents and Morphology in Bones of Duck Exposed to Molybdenum or/and Cadmium

Cadmium (Cd) and high molybdenum (Mo) can lead to adverse reactions on animals, but the coinduced toxicity of Mo and Cd to bone in ducks was not well understood. The objective of this study was to investigate the changes in trace elements' contents and morphology in bones of duck exposed to Mo or/and Cd. One hundred twenty healthy 11-day-old male ducks were randomly divided into six groups and treated with commercial diet containing Cd or/and Mo. On the 60th and 120th days, the blood, excretion, and metatarsals were collected to determine alkaline phosphatase (ALP) activity and the contents of Mo, Cd, calcium (Ca), phosphorus (P), copper (Cu), iron (Fe), zine (Zn), and selenium (Se). In addition, metatarsals were subjected to histopathological analysis with the optical microscope and radiography. The results indicated that Mo and Cd contents significantly increased while Ca, P, Cu, and Se contents remarkably decreased in metatarsals in coexposure groups (P < 0.01). Contents of Fe and Zn in metatarsals had no significant difference among groups (P > 0.05). Ca content in serum had no significant difference among experimental groups (P > 0.05), but P content was significantly decreased in HMo and HMo + Cd groups (P < 0.05). Contents of Ca and P in excretion and ALP activity were significantly increased in coinduced groups (P < 0.05). Furthermore, osteoporotic lesions, less and thinner trabecular bone were observed in combination groups. The findings suggested that dietary of Cd or/and Mo could lead to bone damages in ducks via disturbing the balance of Ca and P in body and homeostasis of Cu, Fe, Zn, and Se in bones; moreover, the two elements showed a possible synergistic relationship.

Effects of thirty elements on bone metabolism

The human skeleton, made of 206 bones, plays vital roles including supporting the body, protecting organs, enabling movement, and storing minerals. Bones are made of organic structures, intimately connected with an inorganic matrix produced by bone cells. Many elements are ubiquitous in our environment, and many impact bone metabolism. Most elements have antagonistic actions depending on concentration. Indeed, some elements are essential, others are deleterious, and many can be both. Several pathways mediate effects of element deficiencies or excesses on bone metabolism. This paper aims to identify all elements that impact bone health and explore the mechanisms by which they act. To date, this is the first time that the effects of thirty minerals on bone metabolism have been summarized.

Magnetic resonance imaging in the tibial epiphyseal growth plate development of Wistar rat

OBJECTIVE

This research aims to investigate magnetic resonance imaging (MRI) in the tibial epiphyseal growth plate development of Wistar rat.

METHODS

Fifty weanling Wistar rats were divided by a computerized blocking procedure into five groups. The rats received standard commercial feed with or without T-2 toxin additive, low-protein feed with or without T-2 toxin additive, and Kashin-Beck disease (KBD)-affected feed.

RESULTS

Compared with the control group rat, MRI showed localized epiphyseal plate swelling, rough appearance, and uneven signal on the tibia of rats fed with KBD-affected feed. Histology confirmed the epiphyseal plate degeneration seen by MRI, and the degenerative changes were characterized by abnormal distribution of chondrocytes with loss and clustering, cartilage fragmentation, and erosion in group E.

CONCLUSIONS

The MR image of the rat epiphyseal plate is altered in the KBD model rats, and epiphyseal plate MRI appearance has been reproduced by using T-2 toxin and KBD-affected feed of epidemic district.

Selenium, the thyroid, and the endocrine system

Recent identification of new selenocysteine-containing proteins has revealed relationships between the two trace elements selenium (Se) and iodine and the hormone network. Several selenoproteins participate in the protection of thyrocytes from damage by H(2)O(2) produced for thyroid hormone biosynthesis. Iodothyronine deiodinases are selenoproteins contributing to systemic or local thyroid hormone homeostasis. The Se content in endocrine tissues (thyroid, adrenals, pituitary, testes, ovary) is higher than in many other organs. Nutritional Se depletion results in retention, whereas Se repletion is followed by a rapid accumulation of Se in endocrine tissues, reproductive organs, and the brain. Selenoproteins such as thioredoxin reductases constitute the link between the Se metabolism and the regulation of transcription by redox sensitive ligand-modulated nuclear hormone receptors. Hormones and growth factors regulate the expression of selenoproteins and, conversely, Se supply modulates hormone actions. Selenoproteins are involved in bone metabolism as well as functions of the endocrine pancreas and adrenal glands. Furthermore, spermatogenesis depends on adequate Se supply, whereas Se excess may impair ovarian function. Comparative analysis of the genomes of several life forms reveals that higher mammals contain a limited number of identical genes encoding newly detected selenocysteine-containing proteins.

Long-time fulvic acid supplementation modulates hydroxylysyl glycosylation of collagen in mice

In order to investigate the impact of fulvic acid (FA) on the hydroxylysyl glycosylation in collagen bio-synthesis, 40 NMRI mice were divided into two groups (n = 20 in each group, consisting 10 females and 10 males). The animal was maintained for two generations by different diets: control group with normal water and food and study group with water containing 30 mg/L FA and normal food. The second generation of the animal was slaughtered, and the biochemical parameters of collagen content and the degree of collagen hydroxylysyl glycosylation in skin, rib and tibia were detected by biochemical methods. The mean value of collagen in the study group was increased slightly, and no significant difference between study group and control group was found (P > 0.05), but the content of glucose-glactose-hydroxylysine (GGH) was significantly decreased in the study group in comparison with the control group (P<0.01). It was suggested that through the decrease of GGH 30 mg/L FA could inhibit the activity of galactosyl-hydroxylysylglucosyl-transferase and further disturb the post-translational modification of collagen intracellularly.

Subchondral bone in osteoarthritis: a biologic link with articular cartilage leading to abnormal remodeling

PURPOSE OF REVIEW

This review deals with new findings highlighting the concept of cross-talk between subchondral bone tissue and articular cartilage that may be crucial for the initiation and/or progression of osteoarthritis. In this review, new factors either produced by subchondral bone tissue or modifying osteoblast metabolism, yet implicated in osteoarthritis, are discussed.

RECENT FINDINGS

The development of cartilage degeneration is concomitant with subchondral bone thickness in osteoarthritis, whereas it is related to higher subchondral bone activity and dysregulation in the synthesis of bone proteins. As an immediate consequence, homotrimers of type 1 collagen are formed that could lead to undermineralization of this tissue. This dysregulation also leads to abnormal production of different factors by osteoblasts such as prostaglandins, leukotrienes, and growth factors. Because microcracks or neovascularization provide a link between the subchondral bone tissue and articular cartilage, these factors could contribute to the abnormal remodeling of osteoarthritic cartilage.

SUMMARY

These findings have an immediate implication for research because new tools need to be developed to study the subchondral bone-cartilage functional unit. Moreover, it could lead to a possible cure for osteoarthritis because this pathology should be considered both a bone and cartilage disease.

Effects of humic substances and phenolic compounds on the in vitro toxicity of aluminium

The effects of natural chelators [humic acids (HA), caffeic acid (CFA), p-coumaric acid (PCA), protocatechuic acid (PA), vanillic acid (VA), salicylic acid (SA), and 4-hydroxyacetophenone (HY)] and effects of well-known chelators [EDTA and citric acid (CA)] on the in vitro toxicity of aluminium (Al) were investigated with the L-929 murine, Vero simian, and MRC-5 human cell lines. Moderate in vitro cytotoxic effects were induced by Al on the three cell lines (IC(50) values ranking from 5.6 to 7.6 mM). Furthermore, an increased toxicity was observed when Al was concurrently administered with CA, SA, VA, PCA, and HY. Inversely, significant cytoprotective effects were noted with EDTA, HA, CFA, and PA. The role of chelators, and especially the position and the number of reactive moieties of the phenolic compounds tested, can be highlighted to explain the different toxicological Al behavior observed.

Osteoblast-like cells from human subchondral osteoarthritic bone demonstrate an altered phenotype in vitro: possible role in subchondral bone sclerosis

OBJECTIVE

Osteoarthritis (OA) is accompanied by subchondral bone sclerosis. The present study was undertaken to determine whether osteoblast-like cells in patients with OA show an abnormal phenotype that could contribute to this sclerosis.

METHODS

Explants and primary in vitro osteoblast-like cell cultures were prepared from subchondral bone specimens from OA patients or from bone removed at autopsy from individuals showing no signs of OA or metabolic bone disease. We measured the abundance and activity of urokinase plasminogen activator (uPA), and the levels of PA inhibitor (PAI-1) and insulin-like growth factor 1 (IGF-1) in conditioned media from both explants and osteoblast-like cells. The expression of osteoblast phenotypic biomarkers was also evaluated.

RESULTS

OA explants showed increased levels and activity of uPA, no changes in PAI-1 abundance, and increases in IGF-1 release, as compared with preparations from normal individuals. In vitro primary osteoblast-like cells showed results similar to the ex vivo findings for uPA, PAI-1, and IGF-1. Primary OA osteoblast-like cells also expressed higher alkaline phosphatase activity and osteocalcin release than normal cells, both under basal conditions and with 1,25(OH)2D3 (1,25-dihydroxyvitamin D) stimulation. Conversely, OA osteoblast-like cells showed blunted cAMP synthesis in response to human parathyroid hormone and prostaglandin E2 in contrast to the finding with normal osteoblast-like cells, a result that could not be attributed to altered adenylate cyclase activity.

CONCLUSION

Ex vivo and in vitro results indicate similar altered activities of OA osteoblasts as compared with normal cells. This suggests that an altered phenotype of subchondral osteoblasts may be a contributing factor in human OA.

Effect of dietary selenium and vitamin E on the biomechanical properties of rabbit bones

It is generally agreed that combined deficiency of selenium and vitamin E leads to several abnormalities including Kashin-Beck disease which is an endemic and chronic degenerative osteoarthrosis. The abnormalities can be reversed by the administration of various forms of selenium and vitamin E. The present study was designed to investigate the effects of dietary selenium and vitamin E on bone tissue and on the biomechanical properties of bone. Young rabbits of both sexes were fed with either a selenium- and vitamin E-adequate diet (control group), or a selenium- and vitamin E-deficient diet or a selenium-excess diet. The selenium-deficient diet resulted in a significant decrease in plasma selenium level and the selenium-excess diet resulted in a significant increase in the plasma selenium level with respect to the corresponding control values (p < 0.05). The diets did not affect the blood cell counts considerably but erythrocyte glutathione peroxidase activity increased (decreased) relatively when the plasma selenium level increased (decreased) (p < 0.05). The light microscopic investigations of the bone tissues of the two experimental groups indicate that the findings of the present work are compatible with osteomalacia. The biomechanical properties of the bones from the three groups were determined experimentally with bending tests. Both the Se- and vitamin E-deficient diet and the Se-excess diet decreased the biomechanical strength of the bones significantly while the bones belonging to the control group always had the largest modulus of elasticity (p < 0.05).

Selenium deficiency and thyroid fibrosis. A key role for macrophages and transforming growth factor beta (TGF-beta)

Free radical damage and fibrosis caused by selenium deficiency are thought to be involved in the pathogenesis of myxoedematous cretinism. So far, no pathway explains the link between selenium deficiency and tissue fibrosis. Pharmacological doses of iodine induce necrosis in iodine-deficient thyroids. Necrosis is much increased if the glands are also selenium-deficient, which then evolve to fibrosis. This rat model was reproduced to explore the role of selenium deficiency in defective tissue repair. At first, proliferation indexes of epithelial cells and fibroblasts were comparable between selenium-deficient and control groups. Then, in selenium-deficient thyroids the inflammatory reaction was more marked being mainly composed of macrophages. The proliferation index of the epithelial cells decreased, while that of the fibroblasts increased. These thyroids evolved to fibrosis. TGF-beta immunostaining was prominent in the macrophages of selenium-deficient rats. Anti TGF-beta antibodies restored the proliferation indexes, and blocked the evolution to fibrosis. In selenium deficiency, an active fibrotic process occurs in the thyroid, in which the inflammatory reaction and an excess of TGF-beta play a key role.