Kidney International, Vol. 63 (2003), pp. 1162–1163

EDITORIAL

Hyaline arteriolosclerosis: New meaning for an old lesion

Hyaline arteriolosclerosis is a common vascular lesion In this issue of Kidney International, Hill and Barietycharacterized by the accumulation of various serum pro- [6] examine the relationship between hyaline arteriolo-teins in the subendothelial space often extending into sclerosis and glomerular structure in aging humans. Theythe media. Hyalin has a characteristic morphologic ap- identify three types of changes in the afferent arteriolepearance, staining bright magenta with periodic acid- (no hyalin, nonobstructing hyalin, or obstructing hyalin)Schiff (PAS) stain and having a glassy texture. This lesion and four glomerular types (normal, hypertrophic, seg-is seen in many different situations, including aging, hyper- mental sclerosis, and ischemic). Hyalin is considered non-tension, diabetes mellitus, and focal segmental glomerulo- obstructing when it does not intrude into the vessel lumen.sclerosis (FSGS). Moritz and Oldt [1] first described the Hill and Bariety found that the afferent arterioles withfrequent occurrence of hyaline arteriolosclerosis with in- nonobstructing hyaline deposits had increased lumen di-creasing age. He also noted that hypertension increased ameter and wall thickness as compared to the other twothe frequency of hyaline arteriolosclerosis more in the kid- types of arterioles. Of note, the muscle layer was thinnerney than in other organs. Hyaline arteriolosclerosis is one in the areas of hyaline deposition, possibly impairing thecomponent of the constellation of findings seen in diabetic ability of the vessel to constrict. Most of the glomerulinephropathy. The lesion is also seen in FSGS to a greater associated with these large arterioles had increased tuftextent than in other renal diseases affecting glomeruli

size, dilated hilar capillaries, increased mean area of indi-such as immunoglobulin A (IgA) nephropathy [2].

vidual capillaries, and increased total capillary area.Previous studies have suggested that hyaline arteriolo-As recognized by Hill and Bariety, the finding of ansclerosis is associated with impaired autoregulation. Auto-

association between hyalin and increased arteriolar sizeregulation is the process that allows the kidney to main-does not establish the cause of hyaline deposition. Onetain a constant blood flow and glomerular filtration ratepossible explanation is that increased wall tension trig-(GFR) at mean blood pressure that varies between 80gers injury in enlarged vessels. Hill and Bariety [6] sug-and 160 mm Hg [3]. This response is mediated by angest that whatever the mechanism of its formation, theas yet imperfectly understood combination of myogenicpresence of hyalin is associated with impaired autoregu-reflexes and tubuloglomerular feedback. Little is knownlation. They propose that autoregulation is lost in thoseabout the effects of aging on autoregulation. In early hyper-individual nephron units in the aging kidney with an en-tension, the autoregulatory curve is shifted to the rightlarged arteriole and its accompanying large glomerulus.so that renal blood flow and GFR remain stable at higherLocal loss of autoregulation, of course, cannot be provedthan normal blood pressures [3]. It has been suggested,in pathologic material alone. However, experimental stud-however, that autoregulation is impaired when long-ies using the renal ablation model suggest that nephronstanding hypertension is accompanied by hyaline arte-

riolosclerosis [3]. One consequence of this loss of auto- enlargement is accompanied by loss of autoregulationregulation may be transmission of increased systemic [7, 8]. Impaired autoregulation has also been recognizedpressure to the glomerulus. A similar picture is seen in in a model of FSGS, the fawn-hooded rat [9]. An interest-patients with diabetic nephropathy. Christensen and Parv- ing unanswered question is whether hyalin in arterial wallsing [4] found that diabetic patients with hypertension contributes to loss of autoregulation or whether hyalin isand nephropathy had diminished autoregulatory capac- deposited only after autoregulation becomes impaired.ity. Four of the 14 patients tested had a completely pres- What can be gained by paying new attention to thissure-passive vasculature. In these patients, the preglo- old lesion, hyaline arteriolosclerosis? Does hyaline arte-merular vessels appeared not to respond to changes in riolosclerosis make a difference? We know that this le-mean arterial pressure so that peaks in systemic pressure sion is seen with glomerulosclerosis. Does its presencecould be transmitted to the glomeruli, increasing the risk accelerate glomerulosclerosis so that we might be able toof glomerular injury. Impaired autoregulation has also use it to predict the later occurrence of glomerular scar-been described in a variety of glomerulopathies associ- ring? The extent of hyaline arteriolosclerosis has beenated with proteinuria, including one case of FSGS [5]. associated with prognosis in FSGS [10]. It could be that

interfering with the development of hyaline arteriolo-Key words: hyaline arteriolosclerosis, autoregulation, aging kidney. sclerosis could provide another avenue for therapeutic

intervention in the war on progression of renal disease. 2003 by the International Society of Nephrology

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Editorial 1163

An immediately practical question also arises. What does REFERENCESthe possible association between hyaline arterioloscle- 1. Moritz AR, Oldt ME: Arteriolar sclerosis in hypertensive and

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rosis is a marker for loss of autoregulation, then it may glomerulonephropathy and focal glomerular sclerosis. Nephron 47:262–265, 1987predict the loss of additional glomeruli in a single kidney.

3. Palmer BA: Renal dysfunction complicating the treatment of hy-Finally, we should congratulate Hill and Bariety for re- pertension. N Engl J Med 347:1256–1261, 2002

4. Christensen PK, Hansen HP, Parving H-H: Impaired autoregula-minding us that we need to look at vessels as well as attion of GFR in hypertensive non-insulin dependent diabetic pa-glomeruli. After all, renal pathologists teach medical stu-tients. Kidney Int 52:1369–1374, 1997

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iol 252:F1003–F1010, 19878. Lee GS, Nast CS, Peng SC, et al: Differential response of glomeru-Jean L. Olson

lar epithelial and mesangial cells after subtotal nephrectomy. Kid-San Francisco, Californianey Int 53:1389–1398, 1998

9. von Dokkum RP, Sun CW, Provoost AP, et al: Altered renalCorrespondence to Jean L. Olson, M.D., Professor of Clinical Pathol- hemodynamics and impaired myogenic responses in the fawn-

ogy, Department of Pathology, S-568A, University of California San hooded rat. Am J Physiol 276:R855–R863, 1999Francisco, 505 Parnassus Avenue, San Francisco, CA 94143, USA. 10. Lee HS, Spargo BH: Significance of renal hyaline arteriolosclerosis

in focal segmental glomeruloslcerosis. Nephron 41:86–93, 1985E-mail: jolson@itsa.ucsf.edu