Localization of estrogen receptors in long bones and vertebrae of human fetuses

Estrogen deficiency affects tooth formation and gene expression in the odontogenic region of female rats

BACKGROUND

There is some evidence that estrogen regulates the expression of several genes in different cells, including dental cells. Therefore, the aim of this study was to investigate the role of estrogen deficiency during tooth development regarding tooth structure morphology and its impact on the expression of odontogenesis-related genes.

METHODS

A total of 40 female Wistar rats was divided into OVX (estrogen deficiency) and Sham (control) groups. Bilateral ovariectomy was performed in the OVX group, while Sham surgery was performed in the control group at the age of 21 days. At an age of 56 days, 16 rats were euthanized for gene expression analyses of Bmp4, Smad6, Tgfb1 and Runx2. At the age of 63 days, the remaining rats were euthanized for histological and morphometric analyses of teeth. The mandibles of the rats were submitted to μCT analysis. Tooth structures (enamel, dentin and dental pulp) were analyzed. T test was used to compare the mean differences between groups (p<0.05).

RESULTS

In the μCT analysis, enamel and dentin thickness were significantly increased in the control group (p<0.0001). Pulp dimensions were significantly larger in the OVX group (p<0.0001). A reduction of tooth structures in the OVX group was confirmed in HE staining. Smad6 was differentially expressed in the OVX group (p=0.04).

CONCLUSION

Estrogen deficiency affects gene expression in the odontogenic region and tooth structure morphology.

Oestrogen receptor alpha, growth hormone receptor, and developmental defect of enamel

BACKGROUND

Oestrogen (ES) and growth hormone (GH) are hormones that may have a role in caries aetiology and developmental defects of enamel (DDE) since their receptors (ERs and GHR) are expressed during amelogenesis.

AIM

To evaluate whether genetic polymorphisms in the genes that codify the ERα (ESR1) and GHR are associated with caries experience and DDE in children.

DESIGN

Two hundred and sixteen children of both genders, aged 9-12 years, were examined and classified according to caries and DDE phenotype. Genomic DNA was extracted from buccal cells in saliva. Genetic polymorphisms in ERS1 (rs1884051 and rs12154178) and GHR (rs297305, rs2940913, rs2910875, and rs1509460) were genotyped using TaqMan chemistry. Data were analysed by PLINK, while the chi-square test was used to compare allele and genotype distributions (alpha of 5%).

RESULTS

A total of 131 children (60.7%) had caries experience, and 43 (19.9%) presented DDE. Genotype and allele distributions were not associated with caries experience (P > 0.05). Genotype and allele distributions between DDE, affected and unaffected, were associated with the polymorphism rs12154178 in ESR1 (P = 0.01 and P = 0.001, respectively) and with the polymorphism rs1509460 in GHR (P = 0.05 and P = 0.02, respectively).

CONCLUSIONS

Genetic polymorphisms in ERS1 (rs12154178) and GHR (rs1509460) are associated with DDE.

Small heat shock protein expression and functions during development

The expression of small heat shock proteins is tightly regulated during development in multiple organisms. As housekeeping proteins, small heat shock proteins help protect cells from apoptosis, stabilize the cytoskeleton and contribute to proteostasis. Consistently, depletion of one small heat shock protein is usually not detrimental due to a certain level of redundancy between the functions of each small heat shock protein. However, while their stress-induced expression is regulated by heat shock factors, their constitutive expression is under the control of other specific transcription factors, suggesting the existence of very specialized functions. This review focuses on the expression patterns and functions of small heat shock proteins in various organisms during development. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.

Gender- and region-specific variations of estrogen receptor α and β expression in the growth plate of spine and limb during development and adulthood

Although estrogen action is indispensable for normal bone growth in both genders, the roles of estrogen receptors (ERs) in mediating bone growth are not fully understood. The effects of ER inactivation on bone growth are sex and age dependent, and may differ between the axial and appendicular regions. In this study, the spatial and temporal expression of ERα and β in the tibial and spinal growth plates of the female and male rats during postnatal development was examined to explore the possible mechanisms. The level of mRNA was examined and compared with quantitative real-time PCR. The spatial location was determined by immunohistochemical analysis. The 1-, 4-, 7-, 12- and 16-week age stages correspond to early life, puberty and early adulthood after puberty, respectively. Gender- and region-specific differences in ERα and β expression were shown in the growth plates. Mainly nuclear staining of ERα and β immunoreactivity was demonstrated in the spinal and tibial growth plate chondrocytes for both genders. Moreover, our study indicated significant effect of gender on temporal ERα and β expression and of region on temporal ERα/ERβ expression ratio. However, spatial differences of region-related ERα and β expression were not observed. Gender-related spatial changes were detected only at 16 weeks of both spine and limb growth plates. ERα and β immunoreactivity was detected in the resting, proliferative and prehypertrophic chondrocytes in the early life stage and during puberty. After puberty, ERα expression was mainly located in the late proliferative and hypertrophic chondrocytes in female, whereas the expression still extended from the resting to hypertrophic chondrocytes in males. Gender- and region-specific expression patterns of ERα and β gene might be one possible reason for differences in sex- and region-related body growth phenotypes. Gender, age and region differences should be taken into consideration when the roles of ERs in the growth plate are investigated.

Sex hormones receptors play a crucial role in the control of femoral and mandibular growth in newborn mice

Sex hormones are important for bone growth. However, the mechanism by which sex hormone receptors influence bone growth remains unclear. In orthodontic treatment, there is a need to develop an indicator of bone maturity to accurately predict the beginning and end of growth. This indicator might be developed from the screening of sex hormones. The purpose of this study was to investigate the role of each sex hormone receptor on bone growth in newborn mice. Five-day-old C57BL/6J mice were used in this experiment. Forty mice underwent an orchiectomy (ORX), ovariectomy (OVX), or sham surgery. One week after surgery, the femur and the mandible were resected for immunohistochemical staining. Alternatively, 80 mice were daily injected with antagonist against receptors oestrogen alpha (ERα), beta (ERβ), or androgen receptor (AR). One week after the first injection, radiographs of the femur and mandible were taken and then measured. Analysis of variance and pairwise comparisons (Fisher) were performed to examine the differences in values measured among the groups In the sham-operated male and female mice, ERβ was found to be more prominent than ERα and AR during all experimental periods. In the ORX and OVX groups, the expressions of all receptors were significantly reduced in comparison with the sham-operated control group throughout the experiment. Moreover, femur and mandibular growth were significantly affected in the group injected with ERβ antagonist. The deficiency of any sex hormone leads to reduced bone growth. In particular, a disturbance in ERβ produces a greater aberrance in both male and female mice immediately after birth.

Restrain of bone growth by estrogen-mimetic peptide-1 (EMP-1): a micro-computed tomographic study

Estrogen has a key role in the regulation of skeletal growth and maintenance of bone mass. Recently, we developed peptides having estrogen-like activity as potential estrogen-based new drugs. The aim of the present study was to evaluate the influence of long-term administration of the most efficacious of these peptides, the hexapeptide EMP-1 (VSWFFE), on bone mass and development. EMP-1 was injected daily to ovariectomized (OVX) and intact young, sexually mature female mice for 10 weeks. Whole femora, including the cartilaginous growth plates were analyzed by micro-computed tomography (microCT). We found that peptide EMP-1 restrains bone growth in OVX mice: it inhibited dramatically bone longitudinal growth (40%), and decreased femoral diaphyseal diameter. Peptide EMP-1 had no effect on bone growth in normal mice, and did not influence the OVX-induced bone loss. We then developed a new microCT methodology to evaluate uncalcified and calcified growth plate parameters. In the OVX mice, peptide EMP-1 reduced volume and thickness of the uncalcified growth plate, a possible cause for the inhibition of bone longitudinal growth. Peptide EMP-1 may be used as a lead compound for the development of drugs to treat acromegalic patients.

Evaluation of the relationship between inducible nitric oxide synthase (iNOS) activity and effects of melatonin in experimental osteoporosis in the rat

Inducible nitric oxide synthase (iNOS) plays a critical role in the pathogenesis of osteoporosis. iNOS generates nitric oxide (NO), a free radical contributing to the imbalance between bone formation and resorption caused by estrogen depletion. Melatonin is the major product of the pineal gland which is known to diminish iNOS expression and NO production significantly. The aim of this study was to determine the distribution of iNOS and the amount of apoptotic cells after melatonin treatment in ovariectomized rats. Since previous studies have shown that constitution of bone formation is primarily sustained in nucleus pulposus and epiphyseal cartilage, experiments were carried out on nucleus pulposus and epiphyseal cartilage; additional quantitation of osteoblasts and osteoclasts were evaluated on vertebral area as well. Vertebral sections of ovariectomized rats were obtained from formalin-fixed and parafin-embedded blocks. iNOS expression and quantitation of apoptotic cells in nucleus pulposus and epiphyseal cartilage were evaluated using indirect immunoperoxidase and TUNEL techniques, respectively. The number of osteoclasts and osteoblasts in trabecular bone was determined using histomorphometry. Ovariectomy increased iNOS expression and the number of apoptotic cells in nucleus pulposus and epiphyseal cartilage, whereas a 4-week treatment with melatonin (10 mg/kg/day) resulted in the reduction of both effects. These data indicate that there is strong influence of melatonin application on expression of iNOS, apoptosis, osteoclast and osteoblast numbers after ovariectomy. In conclusion, melatonin besides its usual use as an antiaging hormone, may also be an effective hormone in treatment of bone changes in estrogen deficiency states.

Immunolocalization of heat shock protein 27 in developing jaw bones and tooth germs of human fetuses

27 kDa Heat shock protein (Hsp27), which is also identified as p29 estrogen-receptor associated protein, plays a crucial role in specific growth stages. It also seems to be involved in the balance between differentiation and apoptosis. To determine whether Hsp27 is involved during craniofacial development and odontogenesis, its expression was studied through immunohistochemistry of developing jaw bone as well as the odontogenesis of heads from human fetuses. Formalin-fixed paraffin-embedded specimens of 7 human fetuses (3 female, 4 male), obtained from miscarriages occurring between the 9th and 16th weeks of pregnancy, were examined by using a monoclonal antibody against Hsp27. Staining intensity (weak, +; moderate, ++; strong, +++) was evaluated semiquantitatively. The sample slice was cut through a coronal plane, which included eyes, nasal cavities, tongue, and primitive dental lamina with tooth germs. A transient and spatially restricted expression of Hsp27 in developing human jaw bones and teeth was observed. Osteoblasts around the uncalcified bone matrix showed Hsp27 immunoreaction products (+++), whereas osteocytes were not immunolabeled. In mandibular condyle, immunolabeling was restricted to hypertrophic chondrocytes (++). In developing tooth germs, Hsp27 immunostaining was detected throughout the bud (+++). At the early cap stage, a strong immunolabeling for Hsp27 was seen in the dental lamina (+++), and a moderate staining was seen in the outer dental epithelium (++). At the late cap stage, Hsp27 expression was detected in the outer dental epithelium (++) as well as in the cells of the future stellate reticulum (++). The spatiotemporal-restricted expression of Hsp27 in craniofacial bones during development suggests that this protein could be involved in the balance between differentiation and apoptosis, by modulating the viability of osteoblasts and chondrocytes. The specific regional and temporal expression patterns of Hsp27 during tooth development sustains that this small Hsp might be related to the morphogenesis and cytodifferentiation processes of tooth germs.

Relationship between osteopenia and lumbar intervertebral disc degeneration in ovariectomized rats

Ovariectomy (OVX) can cause bone loss in rats, but little is known about how it also induces lumbar intervertebral disc degeneration (LVD). This study investigated how estrogen deficiency affected intervertebral discs in OVX rats. Thirty 3-month-old female Sprague-Dawley rats were divided randomly into three equal groups. The baseline control group (BL) was killed at the beginning of the experiment. An ovariectomy was performed in 10 rats (OVX group) and another group of 10 rats was subjected to a sham surgery (Sham group). The OVX rats were untreated after the surgery to allow for the development of moderate osteopenia. Bone mineral density (BMD) measurement and bone histomorphometric analysis were applied to the segments of lumbar spines in all rats killed 6 months after surgery. The pathological changes of intervertebral discs were observed and the degree of LVD was scored by a histological scoring system. The BMD of the spines (L3-L5) in the OVX group decreased significantly compared with the Sham group. The bone volume indices in the OVX group were significantly lower, but the bone turnover rate parameters were significantly higher than those in the Sham group (P < 0.01). The histological scores for LVD in the OVX group were significantly higher than those in the Sham group (P < 0.01). There was a significant negative correlation between the BMD and Grade II discs in the OVX rats (P = 0.042). In conclusion, LVD occurs in the OVX rats and the degeneration of cartilage end plates may be a pathogenic factor in disc degeneration.

Androgens and bone

Loss of estrogens or androgens increases the rate of bone remodeling by removing restraining effects on osteoblastogenesis and osteoclastogenesis, and also causes a focal imbalance between resorption and formation by prolonging the lifespan of osteoclasts and shortening the lifespan of osteoblasts. Conversely, androgens, as well as estrogens, maintain cancellous bone mass and integrity, regardless of age or sex. Although androgens, via the androgen receptor (AR), and estrogens, via the estrogen receptors (ERs), can exert these effects, their relative contribution remains uncertain. Recent studies suggest that androgen action on cancellous bone depends on (local) aromatization of androgens into estrogens. However, at least in rodents, androgen action on cancellous bone can be directly mediated via AR activation, even in the absence of ERs. Androgens also increase cortical bone size via stimulation of both longitudinal and radial growth. First, androgens, like estrogens, have a biphasic effect on endochondral bone formation: at the start of puberty, sex steroids stimulate endochondral bone formation, whereas they induce epiphyseal closure at the end of puberty. Androgen action on the growth plate is, however, clearly mediated via aromatization in estrogens and interaction with ERalpha. Androgens increase radial growth, whereas estrogens decrease periosteal bone formation. This effect of androgens may be important because bone strength in males seems to be determined by relatively higher periosteal bone formation and, therefore, greater bone dimensions, relative to muscle mass at older age. Experiments in mice again suggest that both the AR and ERalpha pathways are involved in androgen action on radial bone growth. ERbeta may mediate growth-limiting effects of estrogens in the female but does not seem to be involved in the regulation of bone size in males. In conclusion, androgens may protect men against osteoporosis via maintenance of cancellous bone mass and expansion of cortical bone. Such androgen action on bone is mediated by the AR and ERalpha.

Estrogens, cartilage, and osteoarthritis

A role for estrogens in osteoarthritis is consistent with the larger increases in women than in men in the incidence and prevalence of hip, knee, and finger osteoarthritis after 50 years of age. Furthermore, hormone replacement therapy for the menopause seems to be associated with a decrease in the prevalence of symptoms and radiological alterations related to hip and knee osteoarthritis. The two estrogen receptors alpha and beta (ERalpha and Erbeta) have been identified in normal and osteoarthritic cartilage, indicating that cartilage can respond to estrogens. Finally, in vivo experiments in animals and in vitro studies have shed light on the mechanisms by which estrogens may influence chondrocyte metabolism.

Relaxin is a key mediator of prostate growth and male reproductive tract development

Male mice deficient in relaxin showed retarded growth and marked deficiencies in the reproductive tract within 1 month of age. At 3 months of age, male reproductive organ weight (including the testis, epididymis, prostate, and seminal vesicle) from relaxin null (RLX-/-) mice were significantly (p < 0.05) smaller than those of wild-type (RLX+/+) male mice. Histologic examination of RLX-/- mouse tissues demonstrated decreased sperm maturation (testis), increased collagen, and decreased epithelial proliferation in the prostate compared with tissues obtained from RLX+/+ animals. The degree of sperm maturation in the testes of sexually mature RLX-/- mice (3 months) resembled that of immature (1 month) RLX+/+ mice and correlated with a decrease in fertility in RLX-/- mice. The marked differences in the extracellular matrix of the testis and prostate in RLX-/- males also correlated with an increase in the rate of cell apoptosis. Relaxin and LGR7 (relaxin receptor) mRNA expression was demonstrated in the prostate gland and testis of the normal mouse. Data from this study demonstrate that relaxin is an important factor in the development and function of the male reproductive tract in mice and has an essential role in the growth of the prostate and maintenance of male fertility. Relaxin may mediate its effects on growth and development by serving as an antiapoptotic factor.

Immunohistochemical detection of estrogen receptor alpha in articular chondrocytes from cows, pigs and humans: in situ and in vitro results

Clinical observations suggest that estrogens are involved in the pathogenesis of postmenopausal osteoarthritis, but only little is known about the influence of these hormones on articular cartilage cells. The effect of estradiol is mediated by estrogen receptors alpha and beta. The goal of the present study was to search for estrogen receptor alpha in articular tissue from cows, pigs and humans by immunohistochemistry to form a basis for in vitro studies. In addition, we also tried to detect estrogen receptor alpha in cultivated articular chondrocytes from cows and bulls under certain culture conditions. Estrogen receptor alpha is detected by the use of antibody 13H2 in articular chondrocytes from cows, bulls, pigs and humans. Chondrocytes are physiologically exposed to reduced oxygen tension. In isolated articular chondrocytes from cows and bulls incubated either with 21% O2 or with 5% O2 positive cells were also found. These positive results therefore encourage testing the influence of estradiol on cultivated articular cartilage cells in these species under different culture conditions.

Age and gender specific stimulation of creatine kinase specific activity by gonadal steroids in human bone-derived cells in culture

We previously reported a non-enzymatic method for isolation of human bone cells in culture that display osteoblastic features and respond to 1,25 dihydroxy vitamin D (1,25) and to parathyroid hormone (PTH). The present study was undertaken to analyze the response of cultured human bone cells to 17beta-estradiol (E2) and to dihydrotestosterone (DHT) as a function of gender and age. Cultured human bone cells, obtained from biopsies during orthopedic surgery, were divided into four groups defined by gender and age: pre- and post-menopausal healthy non-osteoporotic women that were not under hormone replacement therapy (HRT) and mature (<55-year-old) and older (>60-year-old) men. We found gender specific responses to gonadal steroids using the specific activity of the brain type (BB) isozyme of creatine kinase (CK) as a response marker. Constitutive levels of CK activity did not change with age or gender and the enzyme extracted from cells from the different sexes and ages did not respond to either progesterone (P) or to 1,25. CK from the different cells responded to gonadal steroids in a gender specific manner, i.e. CK from female derived cells responded to E2 only and the enzyme from male derived cells responded to DHT only. In female derived cells the response to E2 declined significantly with age, while the response to DHT in CK from male derived cells did not vary with age. This may be due to either decreased proportion of mature osteoblasts and/or their differentiation state and/or changes in the levels of estrogen receptor(s), coactivators or corepressors in these cells. These results extend our knowledge of human osteoblast biology (beyond murine cells) and are therefore more relevant for developing models for treatment of human metabolic bone diseases such as post-menopausal osteoporosis.

Hormonal changes affect the bone and bone marrow cells in a rat model

In this study, we used a rat model to investigate the effects of gonad hormones and replacement therapy on bone structure and the immune system. In the first phase of the study, 3- and 11-month-old F344 rats underwent ovariectomy (OVX) or were sham operated. Three months later, severe osteopenia was histologically observed in OVX rats of both age groups. The changes in the bone marrow structure of OVX rats included deterioration of cancellous bone that was associated with a remarkable increase of adipocyte cells. Furthermore, differential analyses for the expression of cell surface antigens by lymph-myeloid cells was studied using flow cytometry (FACS). The number of myeloid cells expressing ED-9(+) or CD-44(+) was similar in both age groups, and unaffected by OVX. However, an augmentation of T-lymphoid cells expressing CD4(+), CD5(+), or both, were observed with age, as well as after OVX. In the second phase of the study, 11-month-old rats were divided into five experimental groups: sham-operated, OVX, and OVX treated with sustained-release pellets of 17beta-estradiol (OVX-E), progesterone (OVX-P), or both (OVX-E/P). Hormone replacement therapy maintained low physiological levels, and rats were tested 12 weeks after treatment initiation. Administration of 17beta-E, with or without the addition of progesterone, prevented the rise of T lymphoid cells observed in OVX rats, whereas progesterone alone had no effect. In agreement with findings from the first phase, neither OVX nor replacement therapy affected the myeloid cells expression of ED-9 or CD-44. In summary, the cellular changes in the bone marrow of OVX rats were associated with an increase in adipocytes that was correlated with bone atrophy. An augmentation of T-lymphopoiesis was noted with increase in age or after OVX. This increase was reversed to baseline levels by 17beta-E treatment.

Estrogen agonist (zeranol) treatment in a castrated male lamb model: effects on growth and bone mineral accretion

The mechanism of estrogen's action on bone mineralization in children has received little attention. Our objective was to determine the effect of time (developmentally) and duration of exposure to an estrogen agonist (zeranol) on bone growth and mineralization using a castrated male lamb model. At birth, 40 male lambs were castrated and within 14 days of birth (day = 0) they were assigned (n = 10 per group) to age-matched control lambs (C-AGE) or to receive a 12.5-mg zeranol implant as follows: E-0, implanted on days 0, 45, 90, and 135; E-90, implanted on days 90 and 135; and E-0, 90, implanted on days 0, 90, and 135. Lambs were studied for 163 days. Serum was collected on days 28, 73, 118, 135, and 163 and analyzed for minerals (Ca, P, and Mg), markers of bone remodeling (bone alkaline phosphatase [ALP] and tartrate resistant acid phosphatase [TRAP]), 1,25-dihydroxyvitamin D [1,25(OH)2D], growth hormone (GH), and insulin-like growth factor I (IGF-I). Whole-body bone mineral content (BMC), bone mineral density (BMD), fat mass, and lean mass were determined by dual energy X-ray absorptiometry (DEXA) on days 28, 73, 118, and 163. There was a linear increase in growth at all time points. Whole-body BMC, weight, and lean mass of C-AGE and E-90 lambs were less than E-0, and E-0, 90 lambs at all time points. Whole-body BMD of C-AGE and E-90 lambs was less than E-0 and E-0, 90 lambs at 28 days and 73 days; however, after implantation at day 90 whole-body BMD of E-90 lambs was similar to E-0 and E-0, 90 lambs at day 118 and day 163 and all three were greater than C-AGE lambs. There was no effect of treatment on calcium absorption, serum minerals, hormones, or markers of bone remodeling. We conclude from these data that treatment of growing castrated lambs with an estrogen agonist from birth augments growth, whereas delaying estrogen agonist treatment does not facilitate growth but appears to augment bone mineral accretion. We suggest these observations may have clinical relevance, and deserve consideration when treating children with delays in growth and bone mineral accretion.

Estrogen receptor specificity in the regulation of skeletal growth and maturation in male mice

Androgens may regulate the male skeleton directly through a stimulation of androgen receptors or indirectly through aromatization of androgens into estrogen and, thereafter, through stimulation of estrogen receptors (ERs). The relative importance of ER subtypes in the regulation of the male skeleton was studied in ERalpha-knockout (ERKO), ERbeta-knockout (BERKO), and double ERalpha/beta-knockout (DERKO) mice. ERKO and DERKO, but not BERKO, demonstrated decreased longitudinal as well as radial skeletal growth associated with decreased serum levels of insulin-like growth factor I. Therefore, ERalpha, but not ERbeta, mediates important effects of estrogen in the skeleton of male mice during growth and maturation.

Effect of raloxifene-analog (LY 117018-Hcl) on the bone marrow of ovariectomized mice

The effects of LY117018-Hcl (Ralox-A) on body metabolism and differentiation of bone marrow cells were studied in ovariectomized (OVX) mice. We used a mouse model in which estrogen depletion was established for a period of three months before treatment. After that period the animals were divided into three experimental groups consisting of sham-operated, OVX, and OVX-Ralox-A-treated mice. The OVX animals received daily treatment of Ralox-A during two time periods (35 and 65 days). After the treatment we measured the serum levels of protein, ion(s), lipid content, liver, and kidney functions. Our findings indicated that a change in hormonal state did not affect basic body metabolism except for causing an increase in triglycerides (TG) in the OVX mice, which was lowered by the Ralox-A. A higher alkaline phosphatase (ALK-P) level was observed in serum of the OVX-Ralox-A-treated mice than in serum of the OVX mice. We investigated the effects of estrogen depletion on the differentiation of hematopoietic and stromal cells that directly affect bone resorption and formation. OVX and OVX-treated mice were compared with the sham group and assessed for the alteration of these cells' differentiation. The proliferation of stromal stem cells was measured by CFU-F assay in vitro. A decrease in CFU-F colonies derived from OVX mice was observed and after the Ralox-A treatment the number of CFU-F reached sham levels. On the contrary, an upregulation of myeloid cells was observed when analyzed by FACS and by granulocyte/macrophage-colony forming unit (G/M-CFU) assay in selective culture conditions. The G/M-CFUs were increased in the OVX mice and were reduced to sham levels after Ralox-A treatment. In this study, we demonstrated cellular changes of stromal and hemopoietic cells in OVX mice and a beneficial Ralox-A effect that protected such cellular changes.

Disproportional body growth in female estrogen receptor-alpha-inactivated mice

Estrogens play an important role in the regulation of longitudinal bone growth in man, as demonstrated by recent descriptions of individuals with estrogen insensitivity or aromatase deficiency. Two estrogen receptors, ERalpha and ERbeta, have been cloned. The aim of the present study was to investigate the function of ERalpha in the regulation of body growth and skeletal growth. Adult female mice with inactivated ERalpha (ERalpha-/-) demonstrated an increased body weight compared with wild-type mice (114% of control). However, the length of the appendicular skeleton was decreased in adult ERalpha-/- mice (femur 93% of control). In contrast, the axial skeleton was normal (crown-rump length 98% of control). The decreased growth of the appendicular skeleton was associated with decreased serum levels of IGF-I (77% of control), indicating that the GH/IGF-I axis may be involved in the decreased longitudinal bone growth seen in female ERalpha-/- mice.

Estrogen and progesterone receptors in normal and varicose saphenous veins

The presence of estrogen and progesterone receptors was investigated in the walls of normal and varicose veins. Cryostat sections from the saphenous veins of 29 normal individuals, and varicose and normal vein segments of 32 patients with varicose veins, were stained with anti-estrogen or anti-progesterone receptor antibodies. Nuclear stain intensity was scored by three independent observers. Receptors to both hormones were detected in the nuclear regions of the intima and media in females and males. In the adventitia, estrogen and the progesterone receptors were found only in nuclei of the vasa vasorum. Estrogen receptor levels were lower in non-varicose segments of varicose veins compared with normal veins. In varicose segments, estrogen receptors were more abundant than in the non-varicose parts of the same vein, especially in females. Similarly, progesterone receptor levels in the non-varicose portions were higher in females. These gender differences may be related to hormonal action. However, these differences may also be age related. These findings may be related to the involvement of sex-hormones in varicosis, by mechanisms as yet unknown.

Immunofluorescent localization of estrogen receptor-alpha in growth plates of rabbits, but not in rats, at sexual maturity

Estrogens are considered essential to the mechanism for closure of epiphyses in both males and females. The mechanism for this, however, is still unclear. It is likely that estrogen acts directly on growth plate chondrocytes, but the localization of the cells expressing the estrogen receptor (ER) has yet to be ascertained. Moreover, in rodents, growth plates remain open well into adult life. Whether the distribution of estrogen target cells in rodent epiphyses differs from that in other species, is also unclear. We therefore compared localization of estrogen target cells (denoted by ER-alpha protein expression) in species in which growth plates fuse, with that in rodents. Thus, we have investigated ER-alpha protein expression in femoral growth plates from male and female rabbits, just at sexual maturity (6 months), when growth plate fusion was just commencing, and in rats of equivalent developmental stage (9 weeks). ER-alpha was detected in undecalcified cryosections by immunofluorescence with 1D5 monoclonal antibody, raised to human ER-alpha; uterine sections were positive controls. ER-alpha-positive cells were localized to the proliferative/early hypertrophic zone of male and female rabbits. By contrast, cells in the similar region of the mature rat growth plate were ER-alpha-negative in both genders, although receptor could be readily detected in uteri of mature female rats. In growth plates of immature male and female rats (6 weeks), however, ER-alpha was clearly expressed by cells of the proliferative/early hypertrophic zone, but was barely detectable in uteri from immature females. Our findings support the view that estrogen may act directly on the growth plate and, in species in which there is epiphyseal fusion, may thus have a role in this process. If ER-alpha expression is lost at sexual maturity, as in rodents, growth plates may remain open into adulthood. Our results also show the changes in ER-alpha expression in growth plates of maturing rats may be opposite to that in the uterus and raise the possibility that receptor expression may be controlled differently in reproductive and skeletal tissues.

Localization of estrogen-receptor-related antigen in human odontoblasts

Estrogen receptors have been demonstrated in many osteogenic cell lines. Recently, we showed that estrogen deficiency induced by ovariectomy caused enhanced dentin formation in adult rats, suggesting that estrogen receptors may be present in dental tissues. Nothing is known about estrogen receptors in human teeth. We used immunohistochemical staining and immuno-blotting to demonstrate the presence of estrogen receptors in human pulp and/or the pulpo-dentinal border. Unerupted human wisdom teeth were surgically removed, frozen in liquid nitrogen, and prepared for immunological studies. Western blot analysis with monoclonal antibodies specific for human estrogen-receptor-related antigens demonstrated an approximately 29-kDa clear double band in the material scraped from the predentin-odontoblast border and in the fluid that emerged into the pulpal chamber, evidently from the odontoblasts. A weaker double band was also present in pulpal tissue samples. By immunohistochemical staining, estrogen-receptor-related antigens were visualized in the predentinal-odontoblast region and in the pulpal blood vessels. Our results suggest the presence of estrogen receptors in human teeth, and thus the previously reported enhancement of the dentin formation in rats after ovariectomy may be mediated via these receptors.

Bone morphogenetic protein-6 production in human osteoblastic cell lines. Selective regulation by estrogen

Bone morphogenetic proteins (BMPs) induce differentiation of osteoblast and chondroblast lineage cells from uncommitted mesenchymal precursors. Because estrogen has potent osteochondrogenic actions, we investigated its effect on BMP production in two estrogen-responsive, human immortalized cell lines (hFOB/ER3 and hFOB/ER9) that display the mature osteoblast phenotype. These cell lines were produced by stable transfection of the estrogen receptor (ER) gene into immortalized fetal osteoblasts at low ( approximately 800 ER/ nucleus) and at high ( approximately 3, 900 ER/nucleus) levels, respectively. As assessed by reverse transcriptase PCR, treatment with 17beta-estradiol (10(-)10 - 10(-)7 M) increased steady-state levels of BMP-6 mRNA dose dependently by twofold in the hFOB/ER3 cells and by over threefold in the hFOB/ER9 cells. Messenger RNA levels for transforming growth factors-beta1 and -beta2 and BMPs-1 through -5 and -7 levels were unchanged. The results were confirmed by sequence determination of the PCR product and by Northern blot analysis for total RNA. 17beta-estradiol increased BMP-6 protein production sixfold by Western analysis. Cotreatment with antiestrogens (ICI 182,780 or 4-hydroxytamoxifen) antagonized the effects of 17beta-estradiol. These data suggest that some of the skeletal effects of estrogen on bone and cartilage may be mediated by increased production of BMP-6 by osteoblasts.

Menopause is associated with a significant increase in blood monocyte number and a relative decrease in the expression of estrogen receptors in human peripheral monocytes

PROBLEM

The clinical significance of the differential expression of estrogen receptor (ER) in human monocytes was evaluated.

METHOD

Two color flow cytometry analysis was used on peripheral blood samples of young and postmenopausal females and postmenopausal females treated with estrogen replacement therapy. In addition, the monocyte and lymphocyte counts and the blood estrogen levels of each patient were determine.

RESULTS

During menopause there is a significant decrease in the percentage of ER positive monocytes, and an increase in blood monocyte number, which declines following estrogen replacement therapy to values of the young.

CONCLUSIONS

These findings suggest that estrogen modulates the monocyte numbers and its effects may be mediated through the ER in the monocytes.

Preliminary in situ identification of estrogen target cells in bone

Although estrogens profoundly influence skeletal growth and maturation, their mechanism of action is still unclear. To identify their target cells in bone, estrogen receptors were located by immunofluorescence using the H222 monoclonal antibody in cryosections (both undecalcified and briefly decalcified) of hyperplastic mandibular condyle (persistent asymmetric mandibular growth) from a 14-year-old girl and radius and ulna from an 18-month-old female pig (epiphyseal fusion) and from a 3-month-old guinea pig (epiphyses open). Bone was removed from the animals at the peak of estrus. The most striking feature in all three species was the high proportion (approximately 50%) of receptor positive osteocytes. Although all sections contained active bone-forming surfaces, we were unable to identify clearly osteoblasts or lining cells that were estrogen receptor positive. In pig bone only, distinctive groups of receptor positive chondrocytes, with a pericellular localization of collagen type 1, were detected above the growth plate but below secondary centers of ossification. This observation suggests that osteocytes are major skeletal estrogen target cells and may be involved in coordinating the response of surface bone cells to the hormone, and further that chondrocytes may be involved in estrogen-induced epiphyseal growth plate fusion.