Annals of RSCB Vol. XV, Issue 1

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1 AFFECTION OF SANGUINE VESSELS AND BILIARY DUCTS IN CHRONIC INTERSTITIAL FIBROUS HEPATITIS CAUSED BY MIGRATION OF ASCARIS SUUM LARVAE THROUGH PIGLETS LIVER A. F. Gal, V. Miclăuş, C. Cătoi, V. Rus, L. Oana, A. Damian FACULTY OF VETERINARY MEDICINE CLUJ-NAPOCA Summary Parasitical infestation with Ascaris suum induces hemorrhagic and necrotic hepatitis in acute state, but there are affected as well the wall of sinusoid capillaries and cholangioles. Actual report makes some histological investigations about hepatic vessels and cholangioles in liver provided by piglets infested with Ascaris suum. The liver samples were harvested from piglets with this parasite. The samples had been proceed by paraffin technique and stained by usual methods. Parasitic hepatic fibrosis leads to hyperplastic arteriolosclerosis (medial hyperplasia, adventitial fibrosis). Increased vascular tension leads to increased permeability and fibrinoid degeneration of arterial vessel wall. Fibromuscular walls of new formed veins are usually loosed, disorganized, and with thrombosis. Chronic interstitial fibrosis of hepatic tissue leads to the formation of new cholangioles, the apoptosis being as well increased. Key words: vasculitis, fibrinoid necrosis, arteriolosclerosis, liver. Introduction Modern systems utilized for pigs growth decreased parasitical infestation, but it seems that Ascaris suum is still encountered in farms (Roepstorff et al., 1994). During their migration Ascaris suum larvae reach into liver, producing necrotic lesions in acute phase (Cătoi, 2003; Cătoi, 2006). In this context we considered to make some histological investigations in liver provided by piglets infested with Ascaris suum that induced some vascular reactions. The response of vessels to injury involves a complex interaction among the cellular and noncellular elements of the vessel wall and the cellular and noncellular elements of the blood. The key cells of vessels in these reactions are endothelial cells and smooth muscle cells. Endothelial cells are metabolically active and provide a thromboresistant monolayer at the interface of blood and the vessel wall. Injury of endothelial cells is followed by separation 118 from underlying basement membrane and increased permeability to movement of plasma proteins into the subendothelium. Necrosis of endothelium will expose subendothelial collagen and elicit thrombus formation (Jubb et al., 1985; Maruyama et al., 1996). Endothelial cells at the margins of denuded areas proliferate and reendothelialize the damaged area. The other major cellular component of vessels involved in reaction to injury is the smooth muscle cell. These cells have important functions, including production of extracellular components such as collagen, elastin and proteoglycans, maintenance of vascular tone, blood monocyte recruitment, etc (McGalvin et al., 2007). These functions can be regulated by inflammatory mediators. The chronic fibrous parasitical hepatitis (Cătoi, 2006) leads sub sequentially to some disturbances of cholagioles that are usually obstructed by fibrous mass.

2 Material and methods The study was realized in 6 piglets of 4 months that had positive coproparasitological exam for Ascaris suum. From slaughtered animals had been harvested liver fragments represented by 5 mm slices that were fixed during 24 hours in Susa Heidenhain mixture. Fixed samples were dehydrated in ethylic alcohol clarified into butylic alcohol, and embedded into paraffin. Embedded paraffin samples were sectioned to about 5 µm and stained by trichrome Goldner method. Results and discussions Hepatic lobules containing fresh parasitical migration trajectories had hemorrhagic and necrotic character. During traumatic parasitical migration the wall of sinusoid capillaries suffer necrosis inducing large infiltrating hemorrhages. In liver that had some chronic lesions due to some previous parasitical migrations throughout parenchyma were identified some reparatory processes. There are numerous blood vessels with normal structure, but there are some with interesting structural changes. The changes in affected vessels seem to have a multistage evolution. In the first stage is affected the endothelium, being represented by vacuolar degeneration and dethatching from basement membrane. In some other vessels could be noticed endothelial cell hyperplasia with their tendency to occupy vessel lumen. On the other hand there are some vessels which present medial changes involving both muscular and conjunctive component. Proliferating connective tissue from medial vessel wall region become dominant in detriment of muscular tissue. In this manner muscular cells are dislocated and anarchically oriented. In some situations some small vessels suffer complete fibrosis. There will be described both arterial and venous lesions in chronic hepatitis induced by parasitic migration of Ascaris suum larvae throughout the liver. As a consequence of hepatic fibrosis there were encountered hyperplastic arteriolosclerosis that was characterized by medial hyperplasia (Fig 1) and adventitial fibrosis. Increased vascular tension (hypertension) leads to medial smooth muscle cell proliferation, and later to intimal anomalies characterized by increased permeability and fibrinoid degeneration of arterial vessel wall (Fig 2). Fibrinoid degeneration is characterized by amorphous, brightly eosinophilic material in vessel walls, which has the consequence arteriolar wall necrosis, thickening of the arteriolar wall, luminal narrowing, and ischemia (Fig 4). Fibrinoid vascular necrosis leads in some cases to vasculitis by invading necrotized wall with inflammatory cells such as macrophages and neutrophils (Fig 3). Fibrinoid necrosis of arteries is associated with endothelial damage and is characterized by entry and accumulation of serum proteins followed by fibrin polymerization in vessel wall. These materials form an intensely eosinophilic collar that obliterates cellular detail. The lesion is frequent in many acute degenerative and inflammatory diseases of small arteries and arterioles (Cătoi, 2006; Jubb et al., 1985; McGalvin and Zachary, 2007). The fibrinoid necrosis is widespread and is accompanied by endothelial damage and fibrin thrombi. As a consequence of medial fibrinoid necrosis and surrounding hemorrhage, the healing lesions will have perivascular and vascular wall fibrosis (McGalvin and Zachary, 2007). Interstitial veins from portal spaces are enlarged with large lumen as a consequence of interstitial fibroplasia. Furthermore, endothelial cells from veins wall are hypertrophied indicating endothelial proliferation and neoangiogenesis. 119

3 Fig 1. Medial arterial hyperplasia due to post-fibrotic hypertension; smooth muscle cell mitosis (arrow) trichrome Goldner x400. Fig 2. Fibrinoid arteriolar degeneration, medial necrosis - trichrome Goldner x400. Fig 3. Fibrinoid arteriolar necrosis (arrow) with adventitial fibroplasia, and scattered inflammatory cells into the vessels wall; luminal narrowing - trichrome Goldner x200. Fig 4. Fibrinoid arteriolar necrosis with adventitial fibroplasia- detail; trichrome Goldner x400. In some veins are obvious multinucleated cells that have in cytoplasm engulfed red blood cells (Fig 5). Fibromuscular walls of new formed veins are usually decomposed, disorganized, being characterized by irregular smooth muscle proliferation that are interposed with irregular collagen fibers (Fig 6-8). The disorganization of the intima facility the edema of the medial fibromuscular wall which also is disintegrated (Fig 9). As a consequence of endothelial damage there is quite possible to have not only intimal and medial edema, but also vascular thrombosis that obstruct the vessels lumen (Fig 10). Is seems that endothelial cell hyperplasia, fibrinoid vascular necrosis, vasculitis, arteriolar hyperplasia, vascular wall edema and thrombosis, and vascular wall disorganization and fibrosis, are all the consequence of toxic and irritant action induced by Ascaris suum larvae migration throughout the liver, our dates being presented also by some other reports too (Jubb et al., 1985; Maruyama et al., 1996; McGalvin and Zachary, 2007). 120

4 Fig 5. Hypertrophied endothelial cells and multinucleated cells into the vessel lumen; trichrome Goldner x400. Fig 6. Anarchic smooth muscle cell proliferation and disorganization of veins wall; trichrome Goldner x400. Fig 7-8. Anarchic smooth muscle cell proliferation, disorganization and fibrosis of veins wall; trichrome Goldner x400. Fig 9. Endothelial damage with medial edema of vessel wall; trichrome Goldner x400. Fig 10. Vascular thrombosis, intimal and medial edema and vessels wall disorganization; trichrome Goldner x400. Chronic interstitial fibrosis of hepatic tissue leads also to the formation of new cholangioles during existent ones is augmented and their epithelium becomes columnar with large lumen. There are obvious apoptotic cells (Fig 11). In some cholangioles where the bile stasis is intense the apoptosis is increased (Fig 12). In fact the bile stasis and drainage is difficult due to interstitial fibrosis. Augmented biliary ducts may present some desquamated epithelial cells that appear in some microscopic fields, the nuclear morphology indicating necrotic cells that undergo desquamation (Fig 13). 121

5 Fig 11. Cholangioles proliferation and cellular apoptosis; trichrome Goldner x200. Fig 12. Apoptotic cells in cholangioles, especially in distended ones (arrow); trichrome Goldner x200. Fig 13. Desquamation of necrotized (apoptotic) cells in augmented biliary ducts; trichrome Goldner x200. Fig 14. Islands of hepatocytes (central necrosis) encased by fibrous tissue with numerous cholangioles and lymphoeosinofilic infiltrate within; trichrome Goldner x100. Fig 15. Liver cirrhosis characterized by formation of pseudolobules, liver fibrosis and proliferation of cholangioles; trichrome Goldner x50. As a consequence of parasitic migration, the lobular pattern of the liver isn t maintained anymore. There are some islands of hepatocytes (remained from one or several hepatic lobules) encased by fibrous tissue, the last one being dominated by thick collagen fibers, fibroblasts, and eosinophilic infiltrate. In addition there are numerous new formed cholangioles as a consequence of impaired bile drainage (Fig 14). In fact described lesions are similar with that from liver cirrhosis where encased islands of hepatocytes are termed 122 pseudolobules (Jubb et al., 1985; Cătoi, 2006). In addition there is present diffuse fibrosis that dissects the parenchyma during impaired bile drainage leads to cholangiole proliferation (Fig 15). Conclusions Arterial and venous changes in parasitic chronic hepatitis: 1. Parasitic hepatic fibrosis leads to hyperplastic arteriolosclerosis that was characterized by medial hyperplasia and adventitial fibrosis.

6 2. Increased vascular tension (hypertension) leads to medial smooth muscle cell proliferation but also to intimal anomalies such as increased permeability and fibrinoid degeneration of arterial vessel wall. 3. Fibrinoid degeneration has the consequence arteriolar wall necrosis, thickening of the arteriolar wall, luminal narrowing, ischemia, and in some cases to vasculitis by invading necrotized wall with inflammatory cells. 4. Endothelial cells from veins wall are hypertrophied indicating endothelial proliferation and angiogenesis. 5. Fibromuscular walls of new formed veins are usually loosed, disorganized, being characterized by irregular smooth muscle proliferation that are interposed with irregular collagen fibers. 6. The disorganization of the vessels wall structure has the consequence not only intimal and medial edema, but also vascular thrombosis that obstructs the vessels lumen. Biliary duct changes in parasitic chronic hepatitis: 7. Chronic interstitial fibrosis of hepatic tissue leads to the formation of new cholangioles during existent ones is augmented and their epithelium becomes columnar with large lumen. 8. In cholangioles where the bile stasis is intense the apoptosis is increased, some of them being desquamated into the cholangioles lumen. References Cătoi C.: Diagnostic Necropsic Veterinar, pg , 2003, Ed. Academic Press Cluj- Napoca, Cătoi C.: Anatomie patologică specială, pg , 2006, Ed. Academic Press Cluj- Napoca, McGalvin M.D., Zachary J.F.: Pathologic basis of veterinary disease, fourth edition, Mosby Elsevier Inc., pg , 2007 Maruyama H., Nawa Y., Noda S., Mimori T., Choi W-Y.: An outbreak of visceral larva migrans due to Ascaris suum in Kyusha, Japan, Lancet 347: Roepstorff A., Nansen P.: Epidemiology and control of infections in pigs under intensive and non-intensive production systems. Vet. Parasitol. 54: , 1994 Jubb K.V.F., Kennedy P.C., Palmer N.: Pathology of domestic animals, third edition vol 3, Academic Press Inc., pg , 1985 Jubb K.V.F., Kennedy P.C., Palmer N.: Pathology of domestic animals, third edition vol 2, Academic Press Inc., pg