title: Excess maternal and postnatal thyroxine alters chondrocyte numbers and the composition of the extracellular matrix of growth cartilage in rats.
abstract: Purpose/Aim: The aim of this study was to evaluate the effects of excess maternal and postnatal thyroxine on chondrocytes and the extracellular matrix (ECM) of growth cartilage.
  
  
  
  We used 16 adult female Wistar rats divided into two groups: thyroxine treatment and control. From weaning to 40 days of age, offspring of the treated group (n = 8) received L-thyroxine. Plasma free T4 was measured. Histomorphometric analysis was performed on thyroids and femurs of all offspring. Alcian blue histochemical staining and real-time reverse transcription polymerase chain reaction measurements of gene expression levels of Sox9, Runx2, Aggrecan, Col I, Col II, Alkaline phosphatase, Mmp2, Mmp9, and Bmp2 were performed. Data were analyzed for statistical significance by student's t-test.
  
  
  
  Excess maternal and postnatal thyroxine reduced the intensity of Alcian blue staining, altered the number of chondrocytes in proliferative and hypertrophic zones in growth cartilage, and reduced the gene expression of Sox9, Mmp2, Mmp9, Col II, and Bmp2 in the growth cartilage of all offspring. Additionally, excess thyroxine altered the gene expression of Runx2, Aggrecan and Col I, and this effect was dependent on age.
  
  
  
  Excess thyroxine in neonates suppresses chondrocyte proliferation, stimulates chondrocyte hypertrophy and changes the ECM composition by reducing the amount of proteoglycans and glycosaminoglycans (GAGs). Prolonged exposure to excess thyroxine suppresses chondrocyte activity in general, with a severe reduction in the proteoglycan content of cartilage and the expression of gene transcripts essential for endochondral growth and characteristics of the chondrocyte phenotype.
authors.affiliation: a Núcleo de Células Tronco e Terapia Celular Animal (NCT-TCA), Escola de Veterinária , Universidade Federal de Minas Gerais , Belo Horizonte, Brazil.
authors.forename: Lorena Gabriela Rocha
authors.initials: LGR
authors.lastname: Ribeiro
authors.affiliation: b Laboratório de Endocrinologia e Metabolismo, Departamento de Fisiologia e Biofísica , Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais , Belo Horizonte, Brazil.
authors.forename: Juneo Freitas
authors.initials: JF
authors.lastname: Silva
authors.affiliation: a Núcleo de Células Tronco e Terapia Celular Animal (NCT-TCA), Escola de Veterinária , Universidade Federal de Minas Gerais , Belo Horizonte, Brazil.
authors.forename: Natália de Melo
authors.initials: NM
authors.lastname: Ocarino
authors.affiliation: c Departamento de Clínica e Cirurgia Veterinárias , Escola de Veterinária, Universidade Federal de Minas Gerais , Belo Horizonte, Brazil.
authors.forename: Eliane Gonçalves
authors.initials: EG
authors.lastname: de Melo
authors.affiliation: a Núcleo de Células Tronco e Terapia Celular Animal (NCT-TCA), Escola de Veterinária , Universidade Federal de Minas Gerais , Belo Horizonte, Brazil.
authors.forename: Rogéria
authors.initials: R
authors.lastname: Serakides
mesh_terms: D000818:Animals; D002356:Cartilage / Q000254:growth & development* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects*; D019902:Chondrocytes / Q000378:metabolism* / Q000473:pathology; D005109:Extracellular Matrix / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005269:Femur / Q000254:growth & development / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D013974:Thyroxine / Q000009:adverse effects* / Q000494:pharmacology
chemical_list: D013974:Thyroxine
keywords: Bone; extracellular matrix; growth cartilage; hyperthyroidism; rats; thyroid