The morphology of GCA / C. Nordborg et al. The pathogenesis of giant : Morphological aspects

C. Nordborg1, E. Nordborg2, V. Petursdottir1

1Department of Pathology, 2Department of ABSTRACT in GCA. When studying V-beta families Rheumatology, Sahlgrenska University The light-microscopic, electron-micro- of the T-cell infiltrate with flow cyto- Hospital, Göteborg, Sweden. scopic and immunocytochemical charac- metry, Schaufelberger et al. found that These studies were supported by grants teristics of (GCA) the infiltrating lymphocytes are polyclo- from the Göteborg Medical Society, the have been investigated in a number of nal (3). On the other hand, Weyand et Swedish Heart-Lung Foundation, the studies on temporal arteries. Arterial al. (4) demonstrated the identical clonal Swedish Rheumatism Association, Rune atrophy and calcification of the internal expansion of a small proportion of the och Ulla Amlöfs Stiftelse and Syskonen elastic membrane appear to be prere- T-lymphocytes in separate segments of Holmströms Donationsfond. quisites for the evolution of the inflam- the same artery, which indicates antigen Please address correspondence and reprint matory process. giant cells stimulation. A correlation between va- requests to: Claes Nordborg, Department form close to calcifications, apparently rious and the onset of GCA of Pathology, Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden. without connection with other inflam- has been reported; it has been speculated E-mail: [email protected] matory cells and probably by the fusion that infectious disorders might trigger the of modified vascular smooth muscle inflammatory process (5). Zoster-vari- Clin Exp Rheumatol 2000: 18 (Suppl. 20): cells. The foreign body giant cells attack cella may induce - S18-S21. the calcifications. Lymphocytes accumu- tous angiitis. However, immunocyto- © Copyright CLINICAL AND EXPERIMENTAL late around them and may be found in chemistry or PCR did not reveal this type RHEUMATOLOGY 2000. pockets in their cell surface. of virus in inflamed temporal arterial tis- This focal reaction is found in atrophic, sue from 10 GCA patients (6). Key words: Giant cell arteritis, calcified arterial segments in a minority light microscopy, electron microscopy, of inflamed temporal artery . Atrophy and calcification of the morphometry, immunocytochemistry. More commonly seen is a diffuse mo- temporal artery nonuclear attack of the vessel wall in A previous morphometric study showed atrophic as well as non-atrophic seg- that asymmetric atrophy of the temporal ments which leads to severe arterial dila- artery media and an accompanying fo- tation. Langhans giant cells form by the cal calcification of the internal elastic fusion of in the diffuse membrane (IEM) are significantly more inflammatory infiltrate. pronounced in non-inflamed arterial seg- The fact that the diffusely inflamed arte- ments in than ries are markedly widened compared to in controls (7). This type of atrophy the focally inflamed vessels suggests that should not be confused with post-inflam- the inflammatory process starts as a fo- matory scarring. The atrophic arteries cal foreign body giant cell reaction di- display an asymmetric reduction of the rected at calcifications which in turn ini- media, which may be lost in part of the tiates a more diffuse and widespread in- circumference but there is no fibroblastic flammation. or microvascular proliferation. More- over, morphometry showed that the Introduction atrophic, calcified arterial segments had Giant cell arteritis is a chronic form of a significantly smaller outer diameter which predominantly affects than the inflamed vessels (7). This indi- women over 50 years of age. Its etiology cates that the atrophy and calcification and pathogenesis are incompletely are not the result of scarring after arteritic understood. Genetic factors are of rele- since arteries which are vance; the disease is more common in dilated due to a weakening of their wall Caucasians and in patients expressing the do not regain their original circumfer- histocompatibility antigen HLA-DR4 ence. Finally, the fact that the same type (1). Immunological analysis of the in- of calcification and media asymmetry flammatory infiltrate in the vessel wall may be seen in normal arterial aging, indicates the local activation of T-lym- although to a lesser extent, speaks in fa- phocytes (2), which supports the theory vour of a primary atrophy which is not that cell-mediated immunity is involved the result of previous inflammation.

S-18 Hypothalamus-pituitary-adrenocortical and -gonadal axis in RA / M. Cutolo The morphology of GCA / C. EDITORIALNordborg et al. The morphology of the inflamma- Once widened by the weakening of their is rarely seen before the age of 50 be re- tory process wall, arteries do never regain their ori- lated to differences in sex hormone me-

According to a light-microscopic exami- ginal outer diameter. tabolism ? The estrogen production of nation of semi-thin plastic sections, for- pre-menopausal women is cyclic, with eign-body giant cells form focally Giant cell aortitis a higher secretion rate than in men. around the calcifications in atrophic seg- Morphological and morphometric ana- Moreover, menopause implies a major ments of the temporal artery. Serial sec- lyses thus indicate that atrophy and calci- change in estrogen metabolism. A recent tioning revealed giant cells in segments fication are a prerequisite for the initia- epidemiologic study indicates that for- which were devoid of other inflamma- tion of the inflammatory process in tem- mer pregnancies may be a protective fac- tory cells (7). The immuno-phenotype poral arteries. Analogously, the aortic tor against GCA (14), which supports the and ultrastructure of the foreign-body inflammatory reaction in GCA is related contention that GCA may be related to giant cells and the polygonal cells with to smooth muscle atrophy and calcifica- estrogen metabolism. Theoretically, it which they fuse indicate that they might tion. Petursdottir et al. (10) showed la- could influence the pathogenesis of GCA be formed by the fusion of modified ar- minar smooth muscle atrophy and calci- in several ways. Functioning estrogen terial smooth muscle cells (7, 8). The in- fication in the aortic media from patients receptors have been detected in cultured duction of this fusion, which always with GCA. The inflammatory reaction human vascular smooth muscle cells, takes place close to calcifications, needs and the breakdown of elastic lamellae indicating that estrogen may be involved further clarification. was confined to the borders of such atro- in vessel wall metabolism. Moreover, a Mononuclear cells accumulate around phic lesions. The findings support the number of studies suggest that estrogen the foreign-body giant cells; some lym- contention that atrophy and calcification plays an important role in . phocytes may even be found in shallow preceed the inflammatory reaction which In a recent immunocytochemical study pockets in the giant cell surface. It re- is, in fact, primarily directed at calcified we found that the inflamed arteries in mains to be shown whether the foreign- tissue. Moreover, the coupling to arte- GCA expressed distinct cytoplasmic body giant cells present antigen to these rial atrophy and calcification may ex- immunoreactivity to estrogen receptor surrounding lymphocytes, thereby initi- plain why GCA is a disorder of elderly alpha (ERa ) in activated mononuclear ating T-cell activation. An association be- people. inflammatory cells and in giant cells tween the foreign-body giant cell reac- (15). Furthermore, biopsies from GCA tion and T-cell activation has previously The origin of the inflammatory patients and from non-GCA controls dis- been suggested around silicone gel breast infiltrate played cytoplasmic immunopositivity in implants (9). The distribution of inflammatory cells in smooth muscle cells. Western blot ana- The fact that the foreign-body giant cell the arterial wall indicates that the ma- lysis revealed a band corresponding to granuloma, in its pure form, is only found jority of the invading cells are recruited the wild type ERa in inflamed arteries in a minority of temporal artery biopsies from microvessels in the adventitia, and in controls and RT-PCR analysis re- may be due to its focality but may also whereas a minority seem to emanate vealed a strong band corresponding to indicate that it is a short-lasting reaction from the lumen of the inflamed artery approximately 670 bp, as expected (15). which is soon replaced by a diffuse (11, 12). One evidence of cellular migra- These findings justify further studies re- mononuclear cell invasion. In most biop- tion from the adventitia into the vessel garding the roles of estrogen metabolism sies the mononuclear infiltration is more wall is the crowding of inflammatory in vascular aging and GCA. widespread, involving the whole circum- cells at the outer margin of the media, as ference of the artery in atrophic as well would be expected if cells were migra- Hypothesis as non-atrophic arterial segments. Lang- ting from the loose adventital connec- Based on our morphological observa- hans giant cells form in the diffuse in- tive tissue into the tighter smooth mus- tions we have formed the following hy- flammatory infiltrate by the fusion of cle layer. Within the intima, the inflam- pothesis regarding the evolution of the macrophages (7, 8). matory cells accumulate peripherally inflammatory reaction in GCA; this hy- Consequently, according to the light- around the IEM (11). The current obser- pothesis is also illustrated in Figure 1. microscopic findings the site of ignition vations thus suggest that the inflam- Arterial atrophy and calcification are for the inflammatory reaction in GCA matory cells are mainly recruited from prerequisites. Foreign-body giant cells appears to be the foreign-body giant cell the adventitial microvessels, whereas the form close to elastin-related calcifica- reaction to calcified IEM. The mononu- target of the inflammatory reaction is tions without apparent connection with clear inflammation subsequently be- situated in the peripheral intima. CD4+ other inflammatory cells, probably by the comes more diffuse and spreads also into T cells dominated the inflammatory in- fusion of modified smooth muscle cells. non-atrophic arterial segments (7, 8). filtrate, which is in accordance with other The foreign-body giant cells attack cal- This order of the inflammatory events is investigations (11, 13). cifications. Lymphocytes are attracted to supported by the fact that the diffusely the giant cells and may be found in pock- inflamed arteries were significantly Estrogen metabolism in GCA ets at their periphery. It remains to be wider than those which displayed the Could the fact that GCA is far more com- shown if the giant cells present antigens, focal foreign-body giant cell reaction (7). mon among women than among men and thereby initiating the subsequent diffuse

S-19 The morphology of GCA / C. Nordborg et al.

Fig. 1. Suggested morphological evolution of the inflammatory reaction in GCA. (a) Normal artery media: brown; intima: yellow; internal elastic membrane: blue. (b) Asymmetric atrophy of the media and focal calcification (dark brown) of the internal elastic membrane are more pronounced in temporal arteries in GCA. (c) The starting point of the inflammatory reaction is a focal foreign-body giant cell attack on the calcifications. The foreign-body giant cells (red) attract mononuclear cells (dark points). Lymphocytes may be seen in pockets in the giant cell surface. (d) The inflammatory reaction then spreads to other parts of the atrophic arterial segment. The inflammatory cells are mainly recruited from the adventitia and migrate through the media, causing cell crowding at its outer border. (e) The severely inflamed atrophic segment dilates due to destruction of the media and internal elastic membrane. The foreign-body giant cell reaction is now less pronounced. Langhans giant cells (green) form by the fusion of macrophages. (f) The inflammation also spreads to non-atrophic, non-calcified segments. Mononuclear cells (dark points) are recruited mainly from the adventitia and invade the arterial wall, causing crowding outside the media. (g) The inflammation also increases in non-atrophic segments, causing dilatation due to destruction of the media and internal elastic membrane. Mononuclear cells accumulate in the peripheral intima. Langhans giant cells (green) form by the fusion of macrophages.

S-20 Hypothalamus-pituitary-adrenocortical and -gonadal axis in RA / M. Cutolo The morphology of GCA / C. EDITORIALNordborg et al. mononuclear attack which leads to se- 4. WEYAND CM, SCHONBERGER J, OPPITZ U, 10. PETURSDOTTIR V, NORDBORG E, NORD- vere destruction and dilatation of the ar- HUNDER NN, HICOK KC, GORONZY JJ: Di- BORG C: Atrophy of the aortic media in giant terial wall. The diffuse inflammation also stinct vascular lesions in giant cell arteritis cell arteritis. APMIS 1996; 104: 191-8. share identical T cell clonotypes. J Exp Med 11. NORDBORG E, NORDBORG C: The inflamma- spreads into non-atrophic segments. In 1994; 179: 951-60. tory reaction in giant cell arteritis. An immu- the diffuse phase, Langhans giant cells 5. RUSSO MG, WAXMAN J, ABDOH AA, SEREBRO nohistochemical study. Clin Exp Rheumatol form by the fusion of macrophages. LH: Correlation between infection and the on- 1998; 16: 165-8. set of the giant cell (temporal) arteritis syn- 12. WAGNER AD, BJÖRNSSON J, BARTLEY GB,

drome. A trigger mechanism ? Arthritis Rheum GORONZY JJ, WEYAND CM: References 1995; 38: 374-80. producing T-cells in giant cell vasculitis rep- 1. WEYAND CM, HUNDER NN, HICOK KC, 6. NORDBORG C, NORDBORG E, PETURSDOT- resent a minority of tissue infiltrating cells and HUNDER GG, GORONZY JJ: HLA-DRB1 al- TIR V, et al.: Search for varicella zoster virus are located distant from the site of pathology. leles in polymyalgia rheumatica, giant cell arte- in giant cell arteritis. Ann Neurol 1998; 44: 413- Am J Pathol 1996; 148: 1925-33. ritis and rheumatoid arthritis. Arthritis Rheum 4. 13. BANKS PM, COHEN MD, GINSBURG WW, 1994; 37: 514-20. 7. NORDBORG E, BENGTSSON B-Å, NORDBORG HUNDER GG: Immunologic and cytochemical 2. ANDERSSON R, JONSSON R, TARKOWSKI A, C: Temporal artery morphology and morpho- studies of temporal arteritis. Arthritis Rheum BENGTSSON BÅ, MALMVALL BE: T cell sub- metry in giant cell arteritis. APMIS 1991; 99: 1983; 26: 1201-7. sets and expression of immunological acti- 1013-23. 14. DUHAUT P, PINÈDE L, DEMOLOMBE-RAGUÉ vation markers in the arterial walls of patients 8. NORDBORG E, BENGTSSON B-Å, PETURS- S et al.: Giant cell arteritis and polymyalgia with giant cell arteritis. Ann Rheum Dis 1987; DOTTIR V, NORDBORG C: Morphological as- rheumatica: Are pregnancies a protective fac- 46: 915-21. pects on giant cells in giant cell arteritis. An tor ? A prospective, multicentre case-control 3. SCHAUFELBERGER C, STEMME S, ANDERS- electron microscopic and immunocytochemi- study. Rheumatology 1999; 38: 118-23. SON R, HANSSON GK: T lymphocytes in giant cal study. Clin Exp Rheumatol 1997;15:129-34. 15. PETURSDOTTIR V, NORDBORG E, MORA- cell arteritic lesions are polyclonal cells expres- 9. KATZIN WE, FENG LJ, ABBUHL M, KLEIN MA: GHEBI N, PERSSON M, NORDBORG C: Estro- sing alpha-beta type antigen receptors and Phenotype of lymphocytes associated with the gen receptors in giant cell arteritis. An immu- VLA-1 integrin receptors. Clin Exp Immunol Inflammatory reaction to silicone gel breast im- nocytochemical, Western blot and RT-PCR 1993; 91: 421-8. plants. Clin Diagn Lab Immunol 1996;3:156-61. study. Clin Exp Rheumatol 1999; 17: 671-7.

S-21