Pathology of Stromal-Vascular Dystrophy (mesenchymal, extracellular degenerations) develops as a result of metabolism disorder in the connective tissue and is identified in the stroma of organs and the vascular wall. Development of Stromal Vascular Dystrophy occurs in the gistion. Gistion is complex, which includes the microvasculature with the surrounding elements of connective tissue: ground substance, fibrous structures, and connective tissue cells. In the case of metabolism disorder, there is an accumulation of metabolism products, which are brought with the blood and lymph, or may be accumulated due to perverted synthesis, in the intercellular substance.
Morphogenetic mechanisms of Stromal Vascular Dystrophy are such mechanisms as infiltration and perverted synthesis of substances.
Causes of Stromal Vascular Dystrophy according to pathology, are infectious and allergic diseases, rheumatic diseases, diseases of blood circulatory system, in particular, multiple myeloma; hereditary factors associated with the synthesis of abnormal protein, are of great importance. Development of Stromal Vascular Dystrophy is possible in chronic destructive processes and chronic purulent inflammation; there are other causes. Due to the commonality of morphogenetic mechanisms in the development of Dystrophy, combination of different types of Stromal Vascular Dystrophy or their transformation from one type to another is possible. According to the type of metabolism disorder, Stromal Vascular Dystrophy can be divided into: proteinosis, fatty degenerations or lipidoses and carbohydrate degenerations
PROTEINOSES DYSTROPHY IN STROMAL VASCULAR DYSTROPHY – PATHOLOGY OF PROTEINS
Proteinoses Dystrophy – There are the following types of proteinoses that, as a rule, are also development stages: mucoid degeneration, fibrinoid degeneration, hyalinosis, amyloidosis (Table 5).
Mucoid degeneration is superficial and reversible changes associated with the changes in the metabolism of proteins and glycosaminoglycans leading to plasmorrhagia and swelling of collagen fibers, surface disorganization of connective tissue due to accumulation and redistribution of glycosaminoglycans by increasing the content of hyaluronic acid. This stage is characterized by the phenomenon «metachromasia» – tissue discoloration from toluidine blue to li lac-bleu,
Macroscopically Pathology – there are no visual specific characteristics, the organ becomes dull
Microscopic changes are characterized by swelling of collagen fibers, fibrillary fraying, but fasciculate structure of fibers is preserved. There is color change of the stain – “metachromasia” in histochemical reaction in mucoid degeneration (Fig. 10).
Morphogenesis of proteinosis
Ground substance and connective tissue fibers
Changes in the metabolism of proteins and glycosaminoglycans, plasmorrhagia, swelling of collagen fibers → Mucoid degeneration
Destruction plasmorrhagia, formation of protein-polysaccharide complexes (fibrinoid) → Fibrinoid degeneration
Destruction, plasmorrhagia, precipitation of plasma proteins, the formation of hyaline → Hyalinosis
Synthesis of abnormal fibrillar protein with the cells amyloidoblasts, plasmorrhagia, formation of glycoprotein – amyloid. → Amyloidosis
|Figure 10. Mucoid degeneration of the mitral valve in rheumatic disease Phenomenon “metachromasia” Stained with toluidine blue. 200-fold.|
They become sensitive to collagenase; having been stained with picrofuchsin, they are yellow-orange instead of brick-red.
Outcome is reversible or the disease may enter the next stage of fibrinoid changes.
Fibrinoid degeneration dystrophy is deep and irreversible disorganization of connective tissue, which is based on the destruction (decomposition of the ground substance and fibers, accompanied by a sharp increase in vascular permeability, plasmorrhagia and the formation of the protein-polysaccharide complex called fibrinoid. Histochemical fibrinoid is different in various diseases, but its main component is fibrin.
The process may be local or systemic, widespread in nature.
Macroscopically – the organs and tissues are little changed.
Pathology of Microscopic changes are identified in histochemical reactions in the form of fibrinoid necrosis.
Collagen fibers are subject to destruction, fasciculate structure disappears, they become homogeneous, well discolored with eosin, picrofuchsin to yellow according to van Gieson’s stain, Schick’s test is positive; pyroninophilic.
Fibrioid necrosis of collagen fibers may develop in the mitral valves of the heart in rheumatic disease. It is characterized by destruction of collagen fi bers, they lose their structural properties. There is cellular response of macro phages and histiocytes around the area of necrosis (Fig. 11).
|Figure 11. Fibrinoid necrosis of the mitral valve in rheumatic disease. Stained with toluidine blue. 200-fold.|
Outcome is the development of necrosis, the replacement of the hearth of destruction with connective tissue (sclerosis) or the development of hyalinosis. Functional significance – it may lead to organ dysfunction and often to loss of this function due to functional abnormality.
Hyalinosis dystrophy in Stromal Vascular Dystrophy – Pathology of hyaline
Hyalinosis dystrophy is a Stromal Vascular Dystrophy which is characterized by the formation of translucent homogeneous dense mass (hyaline) in connective tissue. This is a stage of subsequent de struction, plasmorrhagia and precipitation of plasma proteins with the formation of hyaline. Hyaline is resistant to acids, enzymes, alkalies, Schick’s test is positive, acid stains are receptive.
Classification of hyalinosis. According to the localization of the process, there are two types: hyalinosis of vessels and hyalinosis of connective tissue. According to the prevalence, hyalinosis may be systemic and local.
Hyalinosis of vessels – According to pathology, it is characterized by the deposition of hyaline masses in the subendothelium of small arteries and arterioles, damage of lamina elas tic, thinning of tunica media of the vessel; finally, arterioles transform into thickened glassy tubes with a sharply narrowed or completely closed lumen of blood vessels, for example, in tension (Fig. 12).
|Figure 12. Hyalinosis of the capillaries of glomeruli of the renal corpuscle and arterioles of the kidneys. Stained with hematoxylin and eosin. 400-fold.|
Hyalinosis of the stroma (Pathology of connective tissue) – the process develops as the result of fibrinoid degeneration, is accompanied by the destruction of colla gen protein and fiber impregnation with plasma proteins and polysaccharides. Hyalinosis of the stroma may develop in sclerosis, plasmatic impregnation, as the result of inflammation, necrosis. The macroscopic manifestations in hyalinosis depend on the localization and prevalence of the process. It often leads to hypertrophy of the organ, its deformation, shrinkage, and is accompanied by functional insufficiency of the impaired organ. Tissue mucilagination, formation of keloid scars (keloids) is also possible.
Amyloidosis (amyloid degeneration) in Stromal Vascular Dystrophy – Pathology of protein metabolism disorder
Amyloidosis (amyloid degeneration) is a Stromal Vascular Dystrophy which is characterized by profound protein metabolism disorder and synthesis of abnormal fibrillar protein with the cells called «amyloidoblasts» and the formation of complex substance amyloid in the interstitial tissue and vascular walls.
Amyloidosis may be in tumors, multiple myeloma, chronic purulent de structive processes, in old age and other diseases.
Macroscopically the organ is increased in size, has dense consistency, the cut is lardaccous (waxy). The process may be local, f.e. in the spleen, in splenic lymph follicles. The cut organ looks like sago grains, that is why it has been called “sago spleen”, they may be equally spaced throughout the splenic pulp, it is the case of “lardaceous spleen”.
Microscopic changes typical for amyloidosis are revealed in special histo chemical reactions.
Specific stains used for revealing of amyloid in tissues.
In order to verify histologically the presence of amyloid in the tissues, Congo red, iodine green, gentian violet, methyl violet staining is most frequently used. Having been stained with mentioned above dyestuff, amyloid localized in the collagen and reticular fibers of basement membranes and stroma, is discolored to different tones of brick-red. The parenchyma takes different color tones in these methods. So, in Congo red staining, the parenchyma is light brick-red; in iodine green staining, the parenchyma is light green (salad); in gentian violet and methyl violet staining, the parenchyma is light blue. The cell nuclei are dis colored to dark blue, and amyloid deposits are discolored to various tones – from red to intense brick-red.
Depending on the localization of the process and the deposition of amyloid, it is the case of perireticular amyloidosis (the deposition of amyloid in the reticular fibers) or pericollagenous amyloidosis (the deposition of amyloid in the collagen fibers).
The process of amyloid deposition may be of generalized diffuse nature, for example, in the stroma of the organs in “lardaceous spleen” (Fig. 13) or of focal nature and lead to amyloidosis.
Amyloid masses displace and replace parenchymatous elements of tissue and lead to the development of their functional insufficiency. Amyloid may be identified intravitam in the urine, if the urine having been stained with specific dye becomes brick-red, it indicates a negative reaction, if the dyestuff is not detected in the urine, it is a case of the positive reaction and the presence of amyloidosis, as specific dye is retained in the tissues.
|Figure 13. Lardaceous spleen. There is diffuse amyloid deposition in the stroma of the spleen tissue Stained with Congo red. 200-fold.|
In local amyloidosis, focal deposition of fibrillar amyloid protein occurs, such as “sago spleen”, when amyloid is revealed in splenic lymph follicles, or in lardaceous kidney, in the walls of blood vessels, anses capillaries, renal glomer uli, basement membrane of the epithelium of the renal tubules (Fig. 14, 15). Outcome is adverse, the process leads to functional insufficiency of the organ, sclerosis or atrophy.
|Figure 14. Sago spleen. Focal amyloid deposition around splenic lymph follicles. Stained with Congo red 200-fold.|
|Figure 15. Lardaceous kidney. The deposition of amyloid in the blood vessels of the renal glomeruli and arterioles of the kidney Stained with Congo red. 400-fold.|
STROMAL-VASCULAR FATTY DEGENERATIONS OR DYSTROPHY (PATHOLOGY OF LIPIDOSES)
Lipidoses are Stromal Vascular Dystrophy associated with metabolism disorder of neutral fats or cholesterol and its esters.
Metabolism disorder of neutral fats manifests itself as increase in fat stores in the adipose tissue, may be local and general, and is referred to as obesity.
Obesity is the process of general nature; there is an increase in the amount of neutral fats in the fat depot. Macroscopically there is excessive accumulation and appearance of adipose tissue in the hypoderm, omentum, mesentery, mediastinum and under the epicardium. Fatty heart, when the organ is in “fatty coat”, increased in volume (Fig. l6), is of great clinical importance.
|Figure 16. Fatty heart, yellow fat deposition under the epicardium, the heart is increased in volume.|
Growth of subepicardial fat leads to atrophy of the cardiomyocytes, invasion to the stroma of the myocardium, what may lead to cardia rupture. Outcome is adverse and depends on the localization and prevalence of the process, the functional significance of the organ.
Metabolism disorder of cholesterol and its esters is the basis for the development of such severe disease as atherosclerosis. The development of atherosclerosis is based on metabolism disorder of fats and proteins with the lesion of the aorta and its branches (In Pathology). Coronary arteries and blood vessels of the brain are most frequently affected. Not only cholesterol and its esters, but also low density lipoproteins, plasma proteins are accumulated in the intima of the vessels increasing vascular permeability and deposition of the lipoprotein complexes in the intima, which lead to their destruction and proliferation of connective tissue (sclerosis, dense vessel wall).
Pathological anatomy (Anatomical Pathology) depends on the stage of atherosclerosis; there are lipoprotein complexes in the form of yellow spots containing lipid complexes in the areas vasovasorum, formation of lipid or lipid-fibrous plaques, later formation of atherosclerotic plaques with calcification. These changes are found throughout the aorta and in other blood vessels of arterial type,
Macroscopic changes in pathology of metabolism disorder of fats and proteins, in atherosclerosis, are characterized by impaired elasticity of the aorta wall, the coronary vessels, the arteries of the brain base, narrowing of the lumen of blood vessels, even their complete obliteration, what is of great clinical importance in connection with circulatory failure in these organs (Fig. 17, 18)
|Figure 17. Atherosclerosis of the arteries of the brain base|
|Figure 18. Macropreparation atherosclerosis of the aorta|
Microscopically, lipid complexes are discolored with Sudan-III to yellow cholesterol crystals as fancy “spiders” are discolored to brown in atherosclerosis of the aorta (Fig. 19).
Lipid complexes in the vascular walls in atherosclerosis are revealed in microscopic examination (in pathology) with the help of special histochemical reaction in staining with Sudan III. In this procedure, lipid complexes are discolored todifferent tones of yellow-orange: fat cells containing fat droplets in the cyto- plasm are also discolored to yellow; nuclei are shifted to the periphery,
Outcome is adverse: the functional significance for the organ depends on the stage of the process and the development of complications of atherosclerosis.
|Figure 19. Atherosclerosis of the aorta. The deposition of yellow lipid complexes. Stained with Sudan III. 400-fold.|