help button home button Endocrine Society JCEM
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Submit a related Letter to the Editor
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Valyasevi, R. W.
Right arrow Articles by Bahn, R. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Valyasevi, R. W.
Right arrow Articles by Bahn, R. S.
The Journal of Clinical Endocrinology & Metabolism Vol. 84, No. 7 2557-2562
Copyright © 1999 by The Endocrine Society


Original Studies

Differentiation of Human Orbital Preadipocyte Fibroblasts Induces Expression of Functional Thyrotropin Receptor1

Rosanee W. Valyasevi, Dana Z. Erickson, Debra A. Harteneck, Charyl M. Dutton, Armin E. Heufelder, Soma C. Jyonouchi and Rebecca S. Bahn

Division of Endocrinology, Mayo Clinic/Foundation (R.W.V., D.Z.E., D.A.H., C.M.D., S.C.J., R.S.B.), Rochester, Minnesota 55905; and Medizinische Klinik, Klinikum Innenstadt, University of Munich (A.E.H.), 80336 Munich, Germany

Address all correspondence and requests for reprints to: Rebecca S. Bahn, M.D., Division of Endocrinology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905. E-mail: bahn.rebecca{at}mayo.edu


    Abstract
 Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Although the autoantigen involved in Graves’ hyperthyroidism is known to be the TSH receptor (TSHr), whether this antigen plays a primary role in the pathogenesis of Graves’ ophthalmopathy (GO) is unclear. We sought to determine whether fibroblasts derived from orbital adipose/connective tissue are capable of differentiating into adipocytes that bear immunoreactive and functional TSHr. In addition, we assessed relative levels of TSHr gene expression in normal and GO orbital adipose/connective tissue specimens.

GO and normal orbital preadipocyte fibroblasts, cultured under conditions known to stimulate adipocyte differentiation, showed evidence of adipogenesis and positive immunostaining for TSHr protein. In addition, significantly more cAMP was produced in response to TSH stimulation in the differentiated cultures than in undifferentiated cultures derived from the same individuals’ cells. Other studies demonstrated relatively greater TSHr gene expression in GO than in normal orbital tissue specimens.

These results indicate that orbital preadipocyte fibroblasts increase their TSHr expression with differentiation and suggest that these cells play an important role in the pathogenesis of GO. Furthermore, our studies support the concept that TSHr may be an important target antigen in this condition. Factors that stimulate adipocyte differentiation and TSHr expression in the orbit in GO have yet to be defined.


    Introduction
 Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 
MANY OF the clinical signs and symptoms of Graves’ ophthalmopathy (GO) can be explained mechanically by the increase in volume of the orbital tissues that has been measured on computed tomography scanning of patients’ orbits (1, 2). This volume increase involves the fatty connective tissues as well as the extraocular muscle bodies. Histological examination of affected orbital tissues reveals an accumulation of hydrophilic glycosaminoglycans as well as an increase in the mass of the orbital adipose tissue (3). Thus, the overall increase in the volume of orbital tissues may be secondary to local tissue edema as well as to the generation of new fat cells from adipose precursor cells responding to adipogenic stimuli.

Adipocyte precursor cells have been isolated from the stromal-vascular fraction of neonatal and adult human adipose/connective tissues from several regions of the body (4). These cells are thought to be a subpopulation of fibroblasts, termed preadipocyte fibroblasts, having the potential to undergo adipocyte differentiation when cultured in appropriate medium (5, 6). Indeed, a recent report by Sorisky and colleagues showed that human orbital fibroblasts contain such a subpopulation capable of in vitro adipogenesis (7). Orbital fibroblasts also produce increased quantities of glycosaminoglycans in vitro after treatment with cytokines known to be present in the orbit in GO (8). Thus, it appears that functional changes in orbital fibroblasts might account for the histological changes characteristic of GO orbital tissues.

Although the autoantigen involved in Graves’ hyperthyroidism is known to be the TSH receptor (TSHr), whether this antigen plays a primary role in the ocular manifestations of the disease is unclear. Several laboratories have detected the presence of TSHr messenger ribonucleic acid (mRNA) or protein in various human orbital cell preparations (9, 10, 11, 12, 13, 14, 15). However, the physiological relevance of this mRNA and the precise nature of the orbital cells expressing this receptor have not been clarified. In the current study, we subjected human orbital preadipocyte fibroblasts from GO patients and normal individuals to adipogenic culture conditions and sought to determine whether the differentiated cells express immunoreactive and functional TSHr. In addition, we examined relative levels of TSHr gene expression in GO and normal orbital adipose/connective tissue specimens.


    Materials and Methods
 Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 
RNA preparation

Orbital adipose/connective tissue specimens were obtained in the course of orbital decompression surgery for severe GO (n = 23). Normal orbital and abdominal adipose/connective tissue specimens were collected at early autopsy from patients with no history of thyroid disease (n = 2). Tissue specimens were stored frozen at -70 C until processed for RNA isolation.

Total RNA was isolated directly from tissue specimens using the Totally RNA Kit (Ambion, Inc., Austin, TX). Orbital tissue samples (0.5–1.0 mg each) from 11–12 different GO patients were combined before RNA extraction to obtain sufficient material to perform each ribonuclease protection assay (RPA). Thus, 2 different orbital tissue pools were examined, each containing specimens from 11–12 different GO patients. In contrast, each single piece of normal orbital adipose/connective tissue or normal abdominal adipose/connective tissue was large enough to supply sufficient RNA for analysis. Positive control RNA was prepared in the same manner from cultured Chinese hamster ovary cells that had been transfected with plasmid containing the human TSHr (JPO9 line) or from a negative control counterpart (JPO2 line) (16).

RPA

As described previously (9), the antisense RNA probe for TSHr RPA was transcribed from a 320-bp PCR product with a T7 phage promotor at its 3'-end in the presence of T7 RNA polymerase (10 U) and [32P]UTP (50 µCi) for labeling. The DNA template used for the PCR was a pBluescript II (SK+) plasmid containing TSHr complementary DNA. The resulting high specific activity probe encompassed nucleotides 576–873 (exons 6–9) of the human TSHr complementary DNA sequence, as reported by Nagayama (17), and was designed to detect both the 2.4-kb intact TSHr (protecting a product of 298 bp) and the 1.3-kb variant form (protecting a product of 217 bp). The antisense RNA probe for human glyceraldehyde-3-phosphate dehydrogenase (GAPDH) RPA was generated from pTRI-GAPDH human antisense control template (Ambion, Inc.), which was digested with restriction enzyme DdeI to generate a 154-nucleotide GAPDH probe.

Total RNA (63–80 µg) was combined with 300,000 cpm TSHr probe and 3,000 cpm GAPDH probe in hybridization buffer, denatured at 95 C, and hybridized at 45 C for 16 h. Nonhybridized total RNA and probe were digested for 1 h at 37 C with ribonuclease A (RNase A; 0.175 U) and RNase T1 (25 U; RNase protection kit, Boehringer Mannheim, Indianapolis, IN). Hybridized samples were digested with proteinase K (50 µg) in the presence of 0.5% SDS and extracted with phenol-chloroform-isoamyl alcohol. The resulting ethanol-precipitated protected fragments were resuspended in loading buffer and resolved on a denaturing polyacrylamide gel (5% acrylamide-8 mol/L urea).

Cell culture and adipocyte differentiation

Orbital adipose/connective tissue explants were obtained from patients undergoing orbital decompression surgery for severe GO (n = 7). All patients had been treated previously for Graves’ hyperthyroidism with 131I; none was currently taking antithyroid drugs. One of the patients was currently taking corticosteriods, whereas none of the others had ever been prescribed this medication for treatment of eye disease. Control cells were obtained in the course of orbital surgery for other conditions from patients with no history of GO or Graves’ disease (n = 4). GO or normal tissue samples were minced and placed directly in plastic culture dishes, allowing preadipocyte fibroblasts to proliferate as described previously (18). Cells were propagated in medium 199 containing 20% FBS (HyClone Laboratories, Inc., Logan, UT), penicillin (100 U/mL), and gentamicin (20 µg/mL) in a humidified 5% CO2 incubator at 37 C and maintained in 80-mm2 flasks with medium 199 containing 10% FBS and antibiotics.

To initiate adipocyte differentiation, orbital cells were grown to confluence in six-well plates. Differentiation was carried out as reported previously (7, 19) with minor modifications; cultures were changed to serum-free DMEM-Ham’s F-12 (1:1; Sigma Chemical Co., St. Louis, MO) supplemented with biotin (33 µmol/L), pantothenic acid (17 µmol/L), transferrin (10 µg/mL), T3 (0.2 nmol/L), insulin (1 µmol/L), carbaprostacyclin (cPGI2; 0.2 µmol/L; Calbiochem, La Jolla, CA), and, for the first 4 days only, dexamethasone (1 µmol/L) and isobutylmethylxanthine (IBMX; 0.1 mmol/L). The differentiation protocol was continued for 10 days, during which time the media were replaced every 3–4 days. Control fibroblasts derived from the same patients’ orbital tissues were cultured similarly, except for the omission in the medium of cPGI2, dexamethasone, and IBMX, as cells cultured in this way do not undergo complete differentiation into mature adipocytes (7). As another control, orbital fibroblasts were cultured for the same period of time in medium 199 with 10% FBS without being switched to differentiation medium.

Oil Red O staining

Orbital preadipocyte fibroblast cultures were plated in one-well culture chamber slides (Nalge Nunc International, Rochester, NY) in medium 199 containing 10% FBS, grown to confluence, and subjected to the differentiation protocol or control conditions. Cells were washed twice with 1 x PBS, fixed in 10% formalin overnight at room temperature, and rinsed in 60% isopropanol before staining with filtered 0.21% Oil Red O in isopropanol-water for 1 h (19). Washed cells were exposed to Mayer’s hematoxylin solution (Sigma Chemical Co., MHS-32) for 5 min and rinsed with tap water before being visualized and photographed at x40 and x100 using an Olympus Corp. BX60 light microscope (Olympus Corp., Melville, NY).

TSHr immunocytochemistry

Orbital preadipocytes were seeded onto glass chamber slides (Nalge Nunc International, Naperville, IL), grown to confluence as monolayers, and subjected to the differentiation protocol as described above. These cells as well as control JPO2 and JPO9 cells were chilled on ice, washed, and fixed in methanol for 15 min at -20 C. Nonspecific binding was blocked using an avidin-biotin blocking kit (SP-2001, Vector Laboratories, Inc., Burlingame, CA) and incubating the cells in 5% sheep serum for 30 min. Monoclonal mouse anti-TSHr antibody directed against TSHr extracellular domain amino acids 32–41 (1:1000 dilution; MA3–217; Affinity BioReagents, Inc., Golden, CO) was applied for 2 h at room temperature. Slides were washed several times with Tris-buffered saline (TBS)-Tween-20 and incubated with biotinylated antimouse IgG (1:300 dilution; RPN 1001, Amersham International, Arlington Heights, IL) at room temperature for 30 min. After multiple washings, slides were exposed to avidin-biotinylated enzyme complex alkaline phosphatase reagent (Vectastain ABC-AP kit, AK 5000, Vector Laboratories, Inc., Burlingame, CA) for 30 min at room temperature. The reaction product was visualized after incubation in the dark for 30 min with an alkaline phosphatase substrate kit (SK-5100; Vector Laboratories, Inc.) containing levamisole to block endogenous alkaline phosphatase activity. Slides were counterstained with Mayer’s hematoxylin solution. Parallel slides with secondary or primary antibodies replaced, in turn, by TBS-Tween-20 and isotype-matched nonimmune mouse IgG were processed to assure specificity and exclude cross-reactivities between the antibodies and conjugates used. Cells were examined at x40 and x100 using an Olympus Corp. BX60 light microscope.

cAMP measurement

Differentiated or control orbital cells in six-well culture plates were preincubated in medium containing IBMX (1 mmol/L; 1 mL/well) for 2 h at 37 C. Recombinant human TSH (rhTSH; 3 x 10-7 mol/L; Genzyme, San Carlos, CA) was added to duplicate wells, and incubation was continued for 1 and 2 h until it was terminated with the addition of hydrochloric acid (0.1 mol/L; 1 mL/well) for 10 min. The culture media were subjected to centrifugation (600 x g), and cAMP production was measured using a commercially available kit (R&D Systems, Minneapolis, MN). Each data point represents the mean of duplicate determinations.


    Results
 Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 
TSHr gene expression

Strongly positive protected bands at 298 and 217 bp, indicating the presence of intact (2.4 kb) and variant (1.3 kb) TSHr mRNA, respectively, were apparent in RPA gel lanes corresponding to GO orbital adipose/connective tissue (Fig. 1Go). In contrast, only weakly positive protected bands were present in all lanes containing mRNA from normal orbital tissue samples. No TSHr mRNA was detected in lanes corresponding to normal abdominal adipose/connective tissue samples. The intact receptor transcript (2.4 kb) was present in positive control JPO9 lanes, whereas negative control JPO2 lanes contained no bands.



View larger version (71K):
[in this window]
[in a new window]
 
Figure 1. RNase protection assay of TSHr mRNA. Lane 1, Mol wt standards; lane 2, blank lane; lane 3, undigested 320-bp probe; lane 4, digested probe; lane 5, normal orbital adipose/connective tissue; lane 6, normal abdominal adipose/connective tissue; lane 7, normal orbital tissue; lane 8, normal abdominal tissue; lane 9, GO orbital tissue. Positive protected bands at 298 bp correspond to 2.4-kb intact TSHr, whereas those at 217 bp correspond to the 1.3-kb variant form TSHr. GAPDH bands are apparent at 154 bp in all sample lanes.

 
Adipocyte differentiation

These studies were carried out to assess and document the morphological changes in orbital cells undergoing adipogenesis. Confluent GO or normal preadipocyte fibroblasts were subjected to the differentiation protocol for 4–10 days. Cells were then either stained with Oil Red O and examined under light microscopy or were left unstained and examined using phase contrast. Control cells from the same patients or normal individuals were maintained in medium 199 with 10% FBS or in control medium (i.e. differentiation medium lacking cPGI2, dexamethasone, and IBMX). During the process of differentiation, orbital cells lost their stellate (fibroblastic) morphology and converted to a spherical (adipocytic) shape. Discrete vacuoles were apparent under phase contrast in the cytoplasm of the differentiating cells (not shown). The morphology of the differentiated GO or normal cultures was clearly distinguishable from that of control undifferentiated cultures, with cytoplasmic inclusions apparent in approximately 10–20% of the cells. However, some of the normal cultures had evidence of adipocyte differentiation in a greater proportion of cells containing particularly large cytoplasmic inclusions. This feature was notable despite the fact that there was significant individual to individual variation in the proportion of cells (whether GO or normal) acquiring these inclusions and in the average size of the inclusions.

TSHr immunostaining

TSHr-specific staining was clearly evident in GO orbital preadipocyte fibroblasts that had been subjected to the adipocyte differentiation protocol (Fig. 2CGo). This immunoreactivity was most intense in the perinuclear and nuclear regions. In contrast, GO preadipocytes from the same patients cultured for the same period of time in control medium 199 with 10% FBS showed no staining of TSHr protein (Fig. 2DGo), whereas only very faint reactivity was apparent in cells cultured in control differentiation medium (not shown). Differentiated normal orbital preadipocytes exhibited similar, but somewhat more intense, staining than was seen in the differentiated GO cultures. Normal preadipocytes grown in control medium 199 with 10% FBS or in the control differentiation medium showed only very faint TSHr immunoreactivity (not shown). Positive control JPO9 cells exhibited strong TSHr immunoreactivity (Fig. 2AGo), whereas the negative control JPO2 cells showed no staining for this protein (not shown). Further, JPO9 cells or differentiated GO or normal preadipocytes, processed with the primary or secondary antibody replaced, in turn, with TBS-Tween-20 or isotype-matched nonimmune mouse IgG, showed no TSHr staining (Fig. 2BGo). The method of fixation used for these studies did not allow for assessment of cell surface staining independent of intracellular staining.



View larger version (98K):
[in this window]
[in a new window]
 
Figure 2. Immunocytochemical analysis of TSHr protein (x100) using an antibody directed against TSHr extracellular domain amino acids 32–41. A, Positive control JPO9 cells; B, differentiated GO orbital cells processed with the primary antibody replaced by TBS-Tween-20; C, orbital cells from a patient with GO cultured in adipocyte differentiation medium; D, undifferentiated orbital cells from the same patient cultured in control medium 199 containing 10% FBS. Studies were performed using orbital cells derived from two GO patients and one normal individual with similar results.

 
Functional TSHr expression

cAMP production in response to rhTSH stimulation was measured in GO or normal preadipocyte fibroblasts that had been subjected to the adipocyte differentiation protocol. Paired control cultures of cells derived from the same GO patient or normal individual were grown in control differentiation medium that lacked cPGI2, dexamethasone, and IBMX. At baseline, both GO and normal differentiated orbital cells produced barely measurable quantities of cAMP. However, after the addition of 3 x 10-8 mol/L rhTSH (corresponding to ~1000-fold the normal serum TSH concentration), cAMP production increased in these cells; maximal values were measured with 3 x 10-7 mol/L rhTSH (Fig. 3Go). At 2 h after the addition of rhTSH, cAMP production in differentiated GO cultures was 16- to 63-fold greater than that in paired undifferentiated cultures (Fig. 4Go). In normal cultures, the differentiated cells produced 2.0- to 10-fold more cAMP than did paired undifferentiated cultures (Fig. 5Go). Although the increase in cAMP production noted in the undifferentiated control GO cultures after rhTSH stimulation was barely detectable (Fig. 4Go), there was a modest rise in cAMP measured in the undifferentiated control normal cultures (Fig. 5Go). A marked individual to individual variation was apparent in the maximal cAMP responses in normal cultures (range, 212- to 9305-fold over baseline) and GO orbital cultures (range, 4- to 183-fold over baseline; Fig. 6Go). However, the magnitude of the maximal responses was generally greater in differentiated normal cultures (mean, 2654-fold over baseline) than in differentiated GO cultures (mean, 72-fold; Fig. 6Go).



View larger version (8K):
[in this window]
[in a new window]
 
Figure 3. TSH dose-response of cAMP production in differentiated orbital cells derived from a patient with GO. Each datum point represents the mean of duplicate determinations. Similar results were obtained using orbital cells derived from another GO patient.

 


View larger version (13K):
[in this window]
[in a new window]
 
Figure 4. cAMP response in differentiated (solid line) and undifferentiated (dashed line) GO orbital cells after stimulation with rhTSH (3 x 10-7 mol/L). Symbols that are the same indicate results from paired cultures of cells derived from two patients with GO. Each datum point represents the mean of duplicate determinations.

 


View larger version (14K):
[in this window]
[in a new window]
 
Figure 5. cAMP response in differentiated (solid line) and undifferentiated (dashed line) normal orbital cells after stimulation with rhTSH (3 x 10-7 mol/L). Symbols that are the same indicate results from paired cultures of cells derived from two normal individuals. Each datum point represents the mean of duplicate determinations.

 


View larger version (12K):
[in this window]
[in a new window]
 
Figure 6. Maximal TSH-dependent cAMP responses in differentiated GO (n = 5) and differentiated normal orbital cultures (n = 4). Values represent fold increases in cAMP production over baseline (unstimulated) levels, and the mean fold increase in each group is indicated. Each datum point represents the mean of duplicate determinations.

 

    Discussion
 Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Evidence that extrathyroidal cells may express TSHr was first presented by Rodbell, who demonstrated TSH-stimulated lipolysis in rat epididymal cells (20). Subsequent reports demonstrated specific TSH binding to guinea pig adipose and retroorbital tissues (21) or to porcine orbital connective tissue membranes (22). In addition, guinea pig brown and white adipose tissues were shown to express TSHr mRNA (23), and the differentiation of rat preadipocytes was shown to be accompanied by TSHr expression (24). Studies concerning the expression of TSHr in human extrathyroidal tissues have been more controversial, especially with regard to whether adult fat cell membranes contain low affinity TSH-binding sites (21, 25). More convincing evidence supports the presence in human neonatal adipocytes of TSHr that declines rapidly with age and is undetectable in adult adipocytes (26).

In a previous report, we demonstrated the presence of mRNA corresponding to TSHr extracellular domain in uncultured GO orbital adipose/connective tissue specimens using RPA, but were unable to detect TSHr mRNA in normal orbital fatty connective tissue samples (9). This apparent acquisition of TSHr expression in GO orbital tissues was the first direct evidence that this antigen may play an important role in the pathogenesis of the disease. In the current study, we again demonstrated TSHr RNA in uncultured orbital tissues from patients with GO. However, this time we used an even more sensitive RPA with longer exposure times and were able to detect faint TSHr expression in normal orbital tissues as well. These mRNA levels were consistently lower than those seen in the GO tissues. In contrast, even with this ultrasensitive method, we could not detect TSHr in normal abdominal adipose/connective tissues. Because normal orbital tissue appears to express TSHr to a greater degree than does normal abdominal fatty tissue, it may be that orbital tissue is more sensitive to local or circulating factors that stimulate TSHr expression than is adipose stromal tissue from other regions of the body.

In earlier studies, we demonstrated TSHr mRNA and protein expression in primary cultures of GO preadipocyte fibroblasts that were grown in medium 199 with 10% FBS (9). These early passage cultures contained mature adipocytes, as determined by Oil Red O staining. In contrast, neither adipocytes nor TSHr expression was detected in late (fourth to fifth) passage cultures of these cells. Because cell passaging and the particular culture conditions used appeared to selected against adipocytes and cells expressing TSHr, we reasoned that the adipocytes in these cultures might be the TSHr-bearing cells.

In the current study, we began to explore the potential link between adipogenesis and TSHr expression in human orbital fibroblasts. After exposure in vitro to adipogenic conditions, TSH-dependent cAMP production and TSHr protein expression increased in GO and normal cultures. Therefore, both TSHr expression and adipogenesis appeared to be stimulated by the same culture conditions. This finding is similar to that reported in rat epididymal, subcutaneous, and perirenal preadipocytes by Haraguchi and colleagues (24). Whether TSHr and adipocyte-specific genes are coregulated in these cells remains to be determined. Of note is that the EC50 of the cAMP response in the orbital cells was higher than that generally observed in either thyroid cells or TSHr-transfected nonthyroid cells. This finding is compatible with the low levels of TSHr mRNA and protein present in these orbital cells.

A striking finding was that the cAMP response to rhTSH in the differentiated normal cultures was, on the average, 40-fold greater than that in the differentiated GO cultures. Likewise, our immunocytochemical studies revealed more intense TSHr staining in differentiated normal than in differentiated GO orbital cells. A related observation was that normal orbital cells cultured in the control differentiation medium (lacking cPGI2, dexamethasone, and IBMX) did, in fact, show a modest increase in cAMP after rhTSH stimulation. In contrast, similarly undifferentiated GO cells did not respond to rhTSH. Thus, differentiated or undifferentiated normal orbital cells were found to express significantly more TSHr than did GO orbital cells exposed to the same culture conditions.

On the surface, these observations may appear to contradict our finding that uncultured GO orbital tissue specimens express TSHr to a greater extent than do normal orbital specimens. However, in the setting of GO, the subpopulation of orbital preadipocytes most sensitive to TSHr-stimulating (and perhaps adipogenic) factors may encounter and respond to such factors in vivo. If terminally differentiated into adipocytes, these cells would not passage in culture. However, they would serve to increase the level of TSHr expression measured in uncultured orbital adipose/connective tissue specimens. In contrast, this same subpopulation of orbital cells from normal individuals would not have been exposed to these factors in vivo. They would therefore remain as adipocyte precursor cells able to be passaged in culture and capable of mounting a vigorous response to in vitro stimuli for TSHr expression and adipocyte differentiation. In further support of this hypothesis is the fact that in some differentiated normal (but not GO) orbital cell cultures there is evidence of adipocyte differentiation in a particularly large proportion of cells containing especially large inclusions.

In summary, these studies support the concept that a subpopulation of orbital fibroblasts may be target cells in GO. In the setting of Graves’ disease, these orbital preadipocytes may be stimulated by unknown factors to differentiate into mature adipocytes that express increased levels of TSHr. As a result, the orbital tissue volume might expand, and TSHr-reactive T cells might infiltrate the orbit. The local release of inflammatory cytokines, TSHr-directed antibodies, or other factors could result in further adipogenesis, stimulation of glycosaminoglycan synthesis, and the expression of immunomodulatory proteins within the orbit. It is also possible that some of these factors might act as counterbalancing inhibitors of adipogenesis or TSHr expression. However, if the net effect of these changes were to significantly increase the volume of the adipose and connective tissues within the orbit, then proptosis, extraocular muscle dysfunction, and congestion would ensue.


    Footnotes
 
1 This work was supported in part by NIH Grant EYO8819 (to R.S.B.) from the National Eye Institute. Back

Received January 19, 1999.

Revised March 4, 1999.

Accepted March 24, 1999.


    References
 Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Forbes G, Gorman CA, Brennan MD, Gehring DG, Ilstrup DM, Earnest F. 1986 Ophthalmopathy of Graves’ disease: computerized volume measurements of the orbital fat and muscle. Am J Neuroradiol. 7:651–656.[Abstract]
  2. Peyster RG, Ginsberg F, Silber JH, Adler LP. 1986 Exophthalmos caused by excessive fat: CT volumetric analysis and differential diagnosis. Am J Neuroradiol. 7:35–40.
  3. Hufnagel TJ, Hickey WJ, Cobbs WH, Jacobiec FA, Iwamoto T, Eagle RC. 1984 Immunohistochemical and ultrastructural studies on the exenterated orbital tissues of a patient with Graves’ disease. Ophthalmopathy. 91:1411–1419.
  4. Chen X, Hausman DB, Dean RG, Hausman GJ. 1997 Differentiation-dependent expression of obese (ob) gene by preadipocytes and adipocytes in primary cultures of porcine stromal-vascular cells. Biochim Biophys Acta. 1359:136–142.[Medline]
  5. Wiederer O, Loffler. 1987 Hormonal regulation of the differentiation of rat adipocyte precursor cells in primary culture. J Lipid Res. 28:649–658.[Abstract]
  6. Hausman GJ, Richardson RL. 1998 Newly recruited and pre-existing preadipocytes in cultures of porcine stromal-vascular cells: morphology, expression of extracellular matrix components, and lipid accretion. J Anim Sci. 76:48–60.[Abstract/Free Full Text]
  7. Sorisky A, Pardasani D, Gagnon A, Smith TJ. 1996 Evidence of adipocyte differentiation in human orbital fibroblasts in primary culture. J Clin Endocrinol Metab. 81:3428–3431.[Abstract]
  8. Bahn RS, Heufelder AE. 1993 Pathogenesis of Graves’ ophthalmopathy. N Engl J Med. 329:1468–1475.[Free Full Text]
  9. Bahn RS, Dutton CM, Natt N, Joba W, Spitzweg C, Heufelder AE. 1998 Thyrotropin receptor expression in Graves’ orbital adipose/connective tissues: potential autoantigen in Graves’ ophthalmopathy. J Clin Endocrinol Metab. 83:998–1002.[Abstract/Free Full Text]
  10. Heufelder AE, Dutton CM, Sarkar G, Donovan KA, Bahn RS. 1993 Detection of TSH receptor RNA in cultured fibroblasts from patients with Graves’ ophthalmopathy and pretibial dermopathy. Thyroid. 3:297–300.[Medline]
  11. Feliciello A, Porcellini A, Ciullo, Bonavolonta G, Avvedimento EV, Fenzi G. 1993 Expression of thyrotropin-receptor mRNA in healthy and Graves’ retro-orbital tissue. Lancet. 342:337–338.[CrossRef][Medline]
  12. Mengistu M, Lukes YG, Nagy EV, et al. 1994 TSH receptor expression in retroocular fibroblasts. J Endocrinol Invest. 17:437–441.[Medline]
  13. Ludgate M, Crisp M, Lane C, et al. 1998 The thyrotropin receptor in thyroid eye disease. Thyroid. 8:411–413.[Medline]
  14. Burch HB, Selletti D, Barnes S, Nagy EV, Bahn RS, Burman KD. 1994 Thyrotropin receptor antisera for the detection of immunoreactive protein species in retroocular fibroblasts obtained from patients with Graves’ ophthalmopathy. J Clin Endocrinol Metab. 78:1384–1391.
  15. Spitzweg C, Joba W, Hunt N, Heufelder AE. 1997 Analysis of human thyrotropin receptor gene expression and immunoreactivity in human orbital tissue. Eur J Endocrinol. 136:599–607.[Abstract/Free Full Text]
  16. Perret J, Ludgate M, Libet F, Gerard C, Dumont JE, Vassart G, Parmentier M. 1990 Stable expression of the human TSH receptor in CHO cells and characterization of differentially expressing clones. Biochem Biophys Res Commun. 171:1044–1050.[CrossRef][Medline]
  17. Nagayama Y, Kaufman KD, Seto P, Rapoport B. 1989 Molecular cloning, sequence and functional expression of the cDNA for the human thyrotropin receptor. Biochem Biophys Res Commun. 165:1184–1190.[CrossRef][Medline]
  18. Bahn RS, Gorman CA, Woloschak GE, David CS, Johnson PM, Johnson CM. 1987 Human retroocular fibroblasts in vitro: a model for the study of Graves’ ophthalmopathy. J Clin Endocrinol Metab. 54:665–670.[Abstract/Free Full Text]
  19. Strutt B, Khalil W, Killinger D. 1996 Growth and differentiation of human adipose stromal cells in culture. In: Jones GE, ed. Methods in molecular medicine. Totowa: Humana Press; vol2 :41–51.
  20. Rodbell M. 1964 Metabolism of isolated fat cells. I. Effects of hormones on glucose metabolism and lipolysis. J Biol Chem. 239:375–380.[Free Full Text]
  21. Davies TF, Teng CS, McLachlan SM, Smith BR, Hall R. 1978 Thyrotropin receptors in adipose tissue, retro-orbital tissue and lymphocytes. Mol Cell Endocrinol. 9:303–310.[CrossRef][Medline]
  22. Perros P, Kendall-Taylor P. 1994 Demonstration of thyrotropin binding sites in orbital connective tissue: possible role in the pathogenesis of thyroid-associated ophthalmopathy. J Endocrinol Invest. 17:163–170.[Medline]
  23. Roselli-Rehfuss L, Robbins LS, Cone RD. 1992 Thyrotropin receptor messenger ribonucleic acid is expressed in most brown and white adipose tissues in the guinea pig. Endocrinology. 130:1857–1861.[Abstract/Free Full Text]
  24. Haraguchi K, Shimura H, Ling Lin, Saito T, Endo T, Onaya T. 1996 Differentiation of rat preadipocytes is accompanied by expression of thyrotropin receptors. Endocrinology. 137:3200–3205.[Abstract]
  25. Mullin BR, Lee G, Ledley FD, Winand RJ, Kohn LD. 1976 Thyrotropin interactions with human fat cell membrane preparations and the finding of a soluble thyrotropin binding component. Biochem Biophys Res Commun. 69:55–62.[CrossRef][Medline]
  26. Marcus C, Ehren H, Bolme P, Arner P. 1988 Regulation of lipolysis during the neonatal period: importance of thyrotropin. J Clin Invest. 82:1793–1797.



This article has been cited by other articles:


Home page
J. Clin. Endocrinol. Metab.Home page
F. Traisk, L. Tallstedt, M. Abraham-Nordling, T. Andersson, G. Berg, J. Calissendorff, B. Hallengren, P. Hedner, M. Lantz, E. Nystrom, et al.
Thyroid-Associated Ophthalmopathy after Treatment for Graves' Hyperthyroidism with Antithyroid Drugs or Iodine-131
J. Clin. Endocrinol. Metab., October 1, 2009; 94(10): 3700 - 3707.
[Abstract] [Full Text] [PDF]


Home page
J. Clin. Endocrinol. Metab.Home page
P. Kok, F. Roelfsema, M. Frolich, J. van Pelt, A. E. Meinders, and H. Pijl
Bromocriptine Reduces Augmented Thyrotropin Secretion in Obese Premenopausal Women
J. Clin. Endocrinol. Metab., April 1, 2009; 94(4): 1176 - 1181.
[Abstract] [Full Text] [PDF]


Home page
J. Immunol.Home page
S. Tsui, V. Naik, N. Hoa, C. J. Hwang, N. F. Afifiyan, A. Sinha Hikim, A. G. Gianoukakis, R. S. Douglas, and T. J. Smith
Evidence for an Association between Thyroid-Stimulating Hormone and Insulin-Like Growth Factor 1 Receptors: A Tale of Two Antigens Implicated in Graves' Disease
J. Immunol., September 15, 2008; 181(6): 4397 - 4405.
[Abstract] [Full Text] [PDF]


Home page
J EndocrinolHome page
M. Lu and R.-Y. Lin
TSH stimulates adipogenesis in mouse embryonic stem cells
J. Endocrinol., January 1, 2008; 196(1): 159 - 169.
[Abstract] [Full Text] [PDF]


Home page
J. Clin. Endocrinol. Metab.Home page
T. J. Cawood, P. Moriarty, C. O'Farrelly, and D. O'Shea
Smoking and Thyroid-Associated Ophthalmopathy: A Novel Explanation of the Biological Link
J. Clin. Endocrinol. Metab., January 1, 2007; 92(1): 59 - 64.
[Abstract] [Full Text] [PDF]


Home page
IOVSHome page
L. Zhang, G. Baker, D. Janus, C. A. Paddon, D. Fuhrer, and M. Ludgate
Biological Effects of Thyrotropin Receptor Activation on Human Orbital Preadipocytes
Invest. Ophthalmol. Vis. Sci., December 1, 2006; 47(12): 5197 - 5203.
[Abstract] [Full Text] [PDF]


Home page
Eur J EndocrinolHome page
T J Cawood, P Moriarty, C O'Farrelly, and D O'Shea
The effects of tumour necrosis factor-{alpha} and interleukin1 on an in vitro model of thyroid-associated ophthalmopathy; contrasting effects on adipogenesis
Eur. J. Endocrinol., September 1, 2006; 155(3): 395 - 403.
[Abstract] [Full Text] [PDF]


Home page
Endocr. Rev.Home page
A. Schaffler, U. Muller-Ladner, J. Scholmerich, and C. Buchler
Role of Adipose Tissue as an Inflammatory Organ in Human Diseases
Endocr. Rev., August 1, 2006; 27(5): 449 - 467.
[Abstract] [Full Text] [PDF]


Home page
IOVSHome page
S. E. Feldon, D. J. J. Park, C. W. O'Loughlin, V. T. Nguyen, S. Landskroner-Eiger, D. Chang, T. H. Thatcher, and R. P. Phipps
Autologous T-Lymphocytes Stimulate Proliferation of Orbital Fibroblasts Derived from Patients with Graves' Ophthalmopathy
Invest. Ophthalmol. Vis. Sci., November 1, 2005; 46(11): 3913 - 3921.
[Abstract] [Full Text] [PDF]


Home page
Endocr. Rev.Home page
S. M. McLachlan, Y. Nagayama, and B. Rapoport
Insight into Graves' Hyperthyroidism from Animal Models
Endocr. Rev., October 1, 2005; 26(6): 800 - 832.
[Abstract] [Full Text] [PDF]


Home page
J. Clin. Endocrinol. Metab.Home page
S. Kumar, A. Leontovich, M. J. Coenen, and R. S. Bahn
Gene Expression Profiling of Orbital Adipose Tissue from Patients with Graves' Ophthalmopathy: A Potential Role for Secreted Frizzled-Related Protein-1 in Orbital Adipogenesis
J. Clin. Endocrinol. Metab., August 1, 2005; 90(8): 4730 - 4735.
[Abstract] [Full Text] [PDF]


Home page
Br J OphthalmolHome page
A Boschi, C. Daumerie, M Spiritus, C Beguin, M Senou, D Yuksel, M Duplicy, S Costagliola, M Ludgate, and M C Many
Quantification of cells expressing the thyrotropin receptor in extraocular muscles in thyroid associated orbitopathy
Br J Ophthalmol, June 1, 2005; 89(6): 724 - 729.
[Abstract] [Full Text] [PDF]


Home page
Eur J EndocrinolHome page
P. Agretti, G. De Marco, M. De Servi, C. Marcocci, P. Vitti, A. Pinchera, and M. Tonacchera
Evidence for protein and mRNA TSHr expression in fibroblasts from patients with thyroid-associated ophthalmopathy (TAO) after adipocytic differentiation
Eur. J. Endocrinol., May 1, 2005; 152(5): 777 - 784.
[Abstract] [Full Text] [PDF]


Home page
EndocrinologyHome page
G. Baker, G. Mazziotti, C. von Ruhland, and M. Ludgate
Reevaluating Thyrotropin Receptor-Induced Mouse Models of Graves' Disease and Ophthalmopathy
Endocrinology, February 1, 2005; 146(2): 835 - 844.
[Abstract] [Full Text] [PDF]


Home page
J. Clin. Endocrinol. Metab.Home page
S. Kumar, M. J. Coenen, P. E. Scherer, and R. S. Bahn
Evidence for Enhanced Adipogenesis in the Orbits of Patients with Graves' Ophthalmopathy
J. Clin. Endocrinol. Metab., February 1, 2004; 89(2): 930 - 935.
[Abstract] [Full Text] [PDF]


Home page
Endocr. Rev.Home page
B. S. Prabhakar, R. S. Bahn, and T. J. Smith
Current Perspective on the Pathogenesis of Graves' Disease and Ophthalmopathy
Endocr. Rev., December 1, 2003; 24(6): 802 - 835.
[Abstract] [Full Text] [PDF]


Home page
J. Clin. Endocrinol. Metab.Home page
R. S. Bahn
Pathophysiology of Graves' Ophthalmopathy: The Cycle of Disease
J. Clin. Endocrinol. Metab., May 1, 2003; 88(5): 1939 - 1946.
[Full Text] [PDF]


Home page
Am. J. Physiol. Cell Physiol.Home page
A. Bell, A. Gagnon, P. Dods, D. Papineau, M. Tiberi, and A. Sorisky
TSH signaling and cell survival in 3T3-L1 preadipocytes
Am J Physiol Cell Physiol, October 1, 2002; 283(4): C1056 - C1064.
[Abstract] [Full Text] [PDF]


Home page
J. Clin. Endocrinol. Metab.Home page
R. W. Valyasevi, D. A. Harteneck, C. M. Dutton, and R. S. Bahn
Stimulation of Adipogenesis, Peroxisome Proliferator-Activated Receptor-{gamma} (PPAR{gamma}), and Thyrotropin Receptor by PPAR{gamma} Agonist in Human Orbital Preadipocyte Fibroblasts
J. Clin. Endocrinol. Metab., May 1, 2002; 87(5): 2352 - 2358.
[Abstract] [Full Text] [PDF]


Home page
Arch OphthalmolHome page
M. Kazim, R. A. Goldberg, and T. J. Smith
Insights Into the Pathogenesis of Thyroid-Associated Orbitopathy: Evolving Rationale for Therapy
Arch Ophthalmol, March 1, 2002; 120(3): 380 - 386.
[Full Text] [PDF]


Home page
J. Clin. Endocrinol. Metab.Home page
T. J. Smith, L. Koumas, A. Gagnon, A. Bell, G. D. Sempowski, R. P. Phipps, and A. Sorisky
Orbital Fibroblast Heterogeneity May Determine the Clinical Presentation of Thyroid-Associated Ophthalmopathy
J. Clin. Endocrinol. Metab., January 1, 2002; 87(1): 385 - 392.
[Abstract] [Full Text] [PDF]


Home page
J. Clin. Endocrinol. Metab.Home page
R. W. Valyasevi, S. C. Jyonouchi, C. M. Dutton, N. Munsakul, and R. S. Bahn
Effect of Tumor Necrosis Factor-{{alpha}}, Interferon-{{gamma}}, and Transforming Growth Factor-{beta} on Adipogenesis and Expression of Thyrotropin Receptor in Human Orbital Preadipocyte Fibroblasts
J. Clin. Endocrinol. Metab., February 1, 2001; 86(2): 903 - 908.
[Abstract] [Full Text]


Home page
IOVSHome page
M. Crisp, K. J. Starkey, C. Lane, J. Ham, and M. Ludgate
Adipogenesis in Thyroid Eye Disease
Invest. Ophthalmol. Vis. Sci., October 1, 2000; 41(11): 3249 - 3255.
[Abstract] [Full Text]


Home page
Endocr. Rev.Home page
L. Bartalena, A. Pinchera, and C. Marcocci
Management of Graves' Ophthalmopathy: Reality and Perspectives
Endocr. Rev., April 1, 2000; 21(2): 168 - 199.
[Abstract] [Full Text]


This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Submit a related Letter to the Editor
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Valyasevi, R. W.
Right arrow Articles by Bahn, R. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Valyasevi, R. W.
Right arrow Articles by Bahn, R. S.


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology Endocrine Reviews J. Clin. End. & Metab.
Molecular Endocrinology Recent Prog. Horm. Res. All Endocrine Journals