Articular cartilage chondrocytes express aromatase and use enzymes involved in estrogen metabolism.

INTRODUCTION: Sex hormones, especially estrogens, have been implicated in articular cartilage metabolism and the pathogenesis of postmenopausal osteoarthritis. The conversion by aromatase (CYP19A1) of androstenedione into estrone (E1) and of testosterone into 17ß-estradiol (E2) plays a key role in the endogenous synthesis of estrogens in tissue. METHODS: We analyzed the expression of aromatase (CYP19A1) in immortalized C-28/I2 and T/C-28a2 chondrocytes, as well as in cultured primary human articular chondrocytes and human articular cartilage tissue, by means of RT-PCR, Western blotting and immunohistochemistry. By means of quantitative RT-PCR and enzyme-linked immunosorbent assay, we also determined whether the aromatase inhibitor letrozole influences estrogen metabolism of cultured chondrocytes in immortalized C-28/I2 chondrocytes. RESULTS: Aromatase mRNA was detected in both immortalized chondrocyte cell lines, in cultured primary human chondrocytes, and in human articular cartilage tissue. By means of Western blot analysis, aromatase was detected at the protein level in articular cartilage taken from various patients of both sexes and different ages. Cultured primary human articular chondrocytes, C-28/I2 and T/C-28a2, and human articular cartilage tissue reacted with antibodies for aromatase. Incubation of C-28/I2 chondrocytes with 10⁻¹¹ M to 10⁻7M letrozole as an aromatase inhibitor revealed significantly increased amounts of the mRNAs of the enzyme cytochrome P4501A1 (CYP1A1), which is involved in the catagen estrogen metabolism, and of the estrogen receptors ER-α and ER-ß. Concomitantly, synthesis of estrone (E1) was significantly downregulated after incubation with letrozole. CONCLUSIONS: We demonstrate that human articular cartilage expresses aromatase at the mRNA and protein levels. Blocking of estrone synthesis by the aromatase inhibitor letrozole is counteracted by an increase in ER-α and ER-ß. In addition, CYP1A1, an enzyme involved in catabolic estrogen metabolism, is upregulated. This suggests that articular chondrocytes use ERs functionally. The role of endogenous synthesized estrogens in articular cartilage health remains to be elucidated.

Calcified myocardial necrosis in pediatric patients after cardiopulmonary resuscitation.

We report three autopsy cases of wide-spread myocardial necrosis with calcification in pediatric patients after temporary generalized hypoxia and initially successful cardiopulmonary resuscitation, but subsequent in-hospital death. Autopsy and histological workup in all three cases showed multiple circumscribed calcified and necrotic areas in progressive stages of organization within the myocardium. We conclude that these macro- and microscopic autopsy features appear to be related to reperfusion injuries in children as a consequence of hypoxic-ischemic changes occurring in the peri- and postresuscitation period.

Fatal spontaneous subdural bleeding due to neonatal giant cell hepatitis: a rare differential diagnosis of shaken baby syndrome.

A 7-week-old girl showed vomiting after feeding, facial pallor, loss of muscle tone and respiratory depression. An emergency doctor performed successful resuscitation and after arrival in hospital, cranial ultrasound showed left-sided subdural hemorrhage, cerebral edema with a shift of the midline, and a decrease in cerebral perfusion. Ophthalmologic examination showed retinal hemorrhage. In view of this, the doctors suspected shaken baby syndrome and approached the parents with their suspicions, but they denied any shaking or trauma. Despite surgery for the subdural hemorrhage the girl died a few hours later with a severe coagulopathy. Autopsy verified subdural hemorrhage, cerebral edema and retinal hemorrhage, but also revealed intact bridging veins and a lack of optic nerve sheath hemorrhage, therefore shaken baby syndrome could not be proven by autopsy. Histological examination showed severe neonatal giant cell hepatitis as the cause of the severe coagulopathy and the associated spontaneous subdural bleeding. Neonatal giant cell hepatitis may be responsible for unexpected deaths in infancy and, although rarely associated with subdural bleeding, must be considered as a potential differential diagnosis of shaken baby syndrome.

Fast erg K+ currents in rat embryonic serotonergic neurones.

Ether-á-go-go-related gene (erg) channels form one subfamily of the ether-á-go-go (EAG) K(+) channels and all three erg channels (erg1-3) are expressed in the brain. In the present study we characterize a fast erg current in neurones in primary culture derived from the median part of rat embryonic rhombencephala (E15-16). The relatively uniform erg current was regularly found in large multipolar serotonergic neurones, and occurred also in other less well characterized neurones. The erg current was blocked by the antiarrhythmic substance E-4031. Single-cell RT-PCR revealed the expression of erg1a, erg1b, erg2 and erg3 mRNA in different combinations in large multipolar neurones. These cells also contained neuronal tryptophan hydroxylase, a key enzyme for serotonin production. To characterize the molecular properties of the channels mediating the native erg current, we compared the voltage and time dependence of activation and deactivation of the neuronal erg current to erg1a, erg1b, erg2 and erg3 currents heterologously expressed in CHO cells. The biophysical properties of the neuronal erg current were well within the range displayed by the different heterologously expressed erg currents. Activation and deactivation kinetics of the neuronal erg current were fast and resembled those of erg3 currents. Our data suggest that the erg channels in rat embryonic rhombencephalon neurones are heteromultimers formed by different erg channel subunits.