Nephrology beyondJASN

Amelioration of Acute Renal Failure by Stem Cell Therapy—Paracrine SecretionVersusTransdifferentiation into Resident Cells

Administered Mesenchymal Stem Cells Protect against Ischemic Acute Renal Failure through Differentiation-Independent Mechanisms.Am J Physiol Renal PhysiolE-pub February 15, 2005

F. Togel, Z. Hu, K. Weiss, J. Isaac, C. Lange, C. Westenfelder

Although the kidney has been suspected, though not definitively proven, to contain organ-specific pluripotent stem cells, their role in regeneration after renal injury is uncertain (^1–3). Recently, however, several investigators found evidence for a renoprotective role of non-organ-specific stem cells in acute renal failure. Arriero et al. (⁴) reported dramatic protection of the kidney against ischemia/ reperfusion injury after injection of in vitro expanded skeletal muscle-derived stem cells, differentiated along the endothelial lineage (but not after injection of nondifferentiated stem cells). The renal function after ischemia was improved and engraftment of the transplanted cells into the renal microvasculature was documented. Morigi et al. (⁵) studied the cisplatin model of acute renal failure: Injection of mesenchymal stem cells (MSC) of bone marrow origin, but not injection of hematopoietic cells, protected syngeneic female mice against severe tubular injury and renal functional impairment. Furthermore, engraftment of MSC into the vigorously proliferating tubular epithelial cell layer was documented by demonstration of Y-chromosome-containing cells. In the same model, Iwasaki et al. (⁶) showed that pretreatment with G-CSF and M-CSF with the rationale to mobilize bone marrow-derived stem cells prevented renal tubular injury and accelerated recovery of renal function. Furthermore, cells expressing markers of bone marrow-derived cells were documented in the tubular epithelial cell layer. Finally, in acute renal failure after ischemia/reperfusion injury, Lin et al. (⁷) showed that hematopoietic stem cells contributed to the regeneration of renal tubular epithelial cells. In the kidneys of nontransgenic female recipients that had been subjected to unilateral ischemia, the authors showed that still after 4 wk β-galactosidase-expressing Y chromosome-positive cells from transgenic male donors were detected. The authors suggested that their findings are accounted for by “transdifferentiation,” i.e., phenotypic conversion of pluripotent somatic stem cells of one tissue type to another tissue type as had previously been postulated by other authors (^8,9). The authors could not exclude, however, cell hybridization, i.e., the possibility that bone marrow-derived cells adopted the phenotype of other cell lineages by fusion (^10,11).

The recent paper of Tögel et al. now introduces a possibility which is alternative or complementary to the above interpretations. Some background information may be helpful at this point. Stem cell therapy has gained much attention in cardiology after controlled trials suggested its efficacy (^12,13), but the mechanism involved has not been clearly defined (¹⁴). Apart from differentiation of stem cells into cardiomyocytes (¹⁵), somewhat dubious because of the above caveat (^10,11) and some new evidence (¹⁶) against this possibility, alternative possibilities have been suggested such as angiogenesis (i.e., capillary formation) (^17,18) and paracrine effects by stem cell secretions. The latter mechanism was suggested after bone marrow-derived mononuclear cells were shown to express vascular endothelial growth factor (VEGF), basic fibroblast growth factor, and angiopoietins (^19–21). An impressive example of paracrine effects has also been provided by the documentation of an immunomodulatory effect, in this case of allogeneic MSC in cocultures with immune cells: T(H)1 cells decreased IFN-γ and T(H)2 cells increased IL-4 secretion (²²). There are even unpublished observations that graft-versus-host reactions are mitigated by such stem cells.

In this study by Tögel et al., MSC were isolated from rat femurs. They were well characterized by isolation as adherent cells and their specificity was validated by their ability to differentiate into osteocytes and adipocytes. The MSC were fluorescence-labeled by carboxy-fluorescein diacetate (CFDA). Two different rat strains were used. The renal arteries were clamped for 40 min and thereafter 10⁶ MSC (or equal numbers of fibroblasts) were injected into the carotid artery. Administration of the cells immediately after ischemia/reperfusion or after 24 h caused faster recovery of serum creatinine compared with injection of vehicle or syngeneic fibroblasts. Using different techniques including genetic markers (Y-chromosome), the fluorescence-labeled MSC could be transiently detected in control and postischemic kidneys, surprisingly mostly in the glomerular capillaries although some were attached to peritubular capillaries. After 24 and 72 h, however, MSC were no longer demonstrable in the kidneys using different techniques for detection. Renal injury scores by histology as well as apoptosis scores were lower and the mitogenic index was higher in the MSC-treated animals. Measurement of gene expression in the kidney provided support for the hypothesis of paracrine actions. By real time PCR after injection of MSC, but not of fibroblast control injection, the expression of proinflammatory cytokines (IL-1β, TNF-α, INFγ, iNOS) was lower and the expression of the anti-inflammatory cytokine IL-10 was higher, while no difference was found with respect to some molecules known to play a role in the recovery from acute renal failure (e.g., VEGF-A,-B,-C,-D; EGF; IGF-1; bone morphogenetic protein-7 [BMP7]).

The authors concluded that in this model the beneficial effect of MSC did not result from transdifferentiation of stem cells into renal parenchymal cells, but was primarily the result of paracrine effects causing downregulation of proinflammatory and upregulation of anti-inflammatory cytokines. The study was well controlled and a laudable effort was made to strictly characterize the injected stem cells. The conclusion would also be in line with recent findings with stem cell therapy in other organs (^21,22).

To explain the differences with previous renal studies on this topic, one has to point to several important differences with respect to species, type of stem cells, time course of renal injury, etc. Nevertheless, this fascinating paper illustrates that matters are much more complex than we thought only a few years ago. Most likely stem cell therapy will not be a panacea and before drawing definite conclusions with respect to its therapeutic potential, safety and feasibility issues must be resolved. Currently, to quote G.B. Shaw, “We have the privilege to be confused on a much higher level.”

References

1. Oliver JA, Maarouf O, Cheema FH, Martens TP, Al-Awqati Q: The renal papilla is a niche for adult kidney stem cells. J Clin Invest 114: 795-804, 2004

2. Lin F, Igarashi P: Searching for stem/progenitor cells in the adult mouse kidney. J Am Soc Nephrol 14: 3290-3292, 2003

3. Imai E, Ito T: Can bone marrow differentiate into renal cells? Pediatr Nephrol 17: 790-794, 2002

4. Arriero M, Brodsky SV, Gealekman O, Lucas PA, Goligorsky MS: Adult skeletal muscle stem cells differentiate into endothelial lineage and ameliorate renal dysfunction after acute ischemia. Am J Physiol Renal Physiol 287: F621-F627, 2004

5. Morigi M, Imberti B, Zoja C, Corna D, Tomasoni S, Abbate M, Rottoli D, Angioletti S, Benigni A, Perico N, Alison M, Remuzzi G: Mesenchymal stem cells are renotropic, helping to repair the kidney and improve function in acute renal failure. J Am Soc Nephrol 15: 1794-1804, 2004

6. Iwasaki M, Adachi Y, Minamino K, Suzuki Y, Zhang Y, Okigaki M, Nakano K, Koike Y, Wang J, Mukaide H, Taketani S, Mori Y, Takahashi H, Iwasaka T, Ikehara S: Mobilization of bone marrow cells by G-CSF rescues mice from cisplatin-induced renal failure, and M-CSF enhances the effects of G-CSF. J Am Soc Nephrol 16: 658-666, 2005

7. Lin F, Cordes K, Li L, Hood L, Couser WG, Shankland SJ, Igarashi P: Hematopoietic stem cells contribute to the regeneration of renal tubules after renal ischemia-reperfusion injury in mice. J Am Soc Nephrol 14: 1188-1199, 2003

8. Poulsom R, Forbes SJ, Hodivala-Dilke K, Ryan E, Wyles S, Navaratnarasah S, Jeffery R, Hunt T, Alison M, Cook T, Pusey C, Wright NA: Bone marrow contributes to renal parenchymal turnover and regeneration. J Pathol 195: 229-235, 2001

9. Gupta S, Verfaillie C, Chmielewski D, Kim Y, Rosenberg ME: A role for extrarenal cells in the regeneration following acute renal failure. Kidney Int 62: 1285-1290, 2002

10. Terada N, Hamazaki T, Oka M, Hoki M, Mastalerz DM, Nakano Y, Meyer EM, Morel L, Petersen BE, Scott EW: Bone marrow cells adopt the phenotype of other cells by spontaneous cell fusion. Nature 416: 542-545, 2002

11. Medvinsky A, Smith A: Stem cells: Fusion brings down barriers. Nature 422: 823-825, 2003

12. Wollert KC, Meyer GP, Lotz J, Ringes-Lichtenberg S, Lippolt P, Breidenbach C, Fichtner S, Korte T, Hornig B, Messinger D, Arseniev L, Hertenstein B, Ganser A, Drexler H: Intracoronary autologous bone-marrow cell transfer after myocardial infarction: The BOOST randomised controlled clinical trial. Lancet 364: 141-148, 2004

13. Schachinger V, Assmus B, Britten MB, Honold J, Lehmann R, Teupe C, Abolmaali ND, Vogl TJ, Hofmann WK, Martin H, Dimmeler S, Zeiher AM: Transplantation of progenitor cells and regeneration enhancement in acute myocardial infarction: Final one-year results of the TOPCARE-AMI Trial. J Am Coll Cardiol 44: 1690-1699, 2004

14. Pittenger MF, Martin BJ: Mesenchymal stem cells and their potential as cardiac therapeutics. Circ Res 95: 9-20, 2004

15. Kehat I, Kenyagin-Karsenti D, Snir M, Segev H, Amit M, Gepstein A, Livne E, Binah O, Itskovitz-Eldor J, Gepstein L: Human embryonic stem cells can differentiate into myocytes with structural and functional properties of cardiomyocytes. J Clin Invest 108: 407-414, 2001

16. Balsam LB, Wagers AJ, Christensen JL, Kofidis T, Weissman IL, Robbins RC: Haematopoietic stem cells adopt mature haematopoietic fates in ischaemic myocardium. Nature 428: 668-673, 2004

17. Kocher AA, Schuster MD, Szabolcs MJ, Takuma S, Burkhoff D, Wang J, Homma S, Edwards NM, Itescu S: Neovascularization of ischemic myocardium by human bone-marrow-derived angioblasts prevents cardiomyocyte apoptosis, reduces remodeling and improves cardiac function. Nat Med 7: 430-436, 2001

18. Orlic D, Kajstura J, Chimenti S, Jakoniuk I, Anderson SM, Li B, Pickel J, McKay R, Nadal-Ginard B, Bodine DM, Leri A, Anversa P: Bone marrow cells regenerate infarcted myocardium. Nature 410: 701-705, 2001

19. Kamihata H, Matsubara H, Nishiue T, Fujiyama S, Tsutsumi Y, Ozono R, Masaki H, Mori Y, Iba O, Tateishi E, Kosaki A, Shintani S, Murohara T, Imaizumi T, Iwasaka T: Implantation of bone marrow mononuclear cells into ischemic myocardium enhances collateral perfusion and regional function via side supply of angioblasts, angiogenic ligands, and cytokines. Circulation 104: 1046-1052, 2001

20. Honold J, Assmus B, Lehman R, Zeiher AM, Dimmeler S: Stem cell therapy of cardiac disease: An update. Nephrol Dial Transplant 19: 1673-1677, 2004

21. Losordo DW, Dimmeler S: Therapeutic angiogenesis and vasculogenesis for ischemic disease: Part II: Cell-based therapies. Circulation 109: 2692-2697, 2004

22. Aggarwal S, Pittenger MF: Human mesenchymal stem cells modulate allogeneic immune cell responses. Blood 105: 1815-1822, 2005

Posttransplant Skin Carcinoma—Fighting Immunosuppression by Local Immunostimulation

Guidelines for the Management of Squamous Cell Carcinoma in Organ Transplant Recipients.Dermatol Surg30: 642-650, 2004

T. Stasko, M.D. Brown, J.A. Carucci, S. Euvrard, T.M. Johnson, R.D. Sengelmann, E. Stockfleth, W.D. Tope; International Transplant-Skin Cancer Collaborative; European Skin Care in Organ Transplant Patients Network

Malignancy after renal transplantation has become an ever more important clinical issue after longer graft survival rates have been achieved and increasingly older patients are accepted for transplantation (1). The magnitude of the issue had been underestimated in the past because in clinical practice other issues such as rejection and infection had dominated. When adult patients survived long enough, however, it was noted that 10 yr after transplantation the risk of malignancy was 13.8-fold higher than in the background population (2) and 10 times higher than in hemodialyzed patients (3). It is also of note that an increased frequency is not found for all types of cancer, but preferentially for squamous cell carcinoma of the skin, lip, cervix, vulva (4) and for posttransplant lymphoproliferative disorders (1). In most countries, squamous-cell carcinoma, but also basal-cell carcinoma, account for >90% of all skin cancers in transplanted patients (5–7), with the notable exception of Japan (8). The frequency of squamous skin cancers is particularly remarkable in young adults having received their graft during childhood (9). The highest frequency of squamous skin cancer has been reported from Australia where a mostly fair-skinned population is exposed to intense ultraviolet sunlight: The cumulative incidence, calculated by life-table analysis, increased progressively from 7% after 1 yr to 45% after 11 yr and to 70% after 20 yr (7^,10^,11). The deleterious effect of ultraviolet light is apparently related to DNA mutations leading to the formation of thymidine dimers and inactivation of the tumor suppressor gene p53 (1). Papillomaviruses apparently play an ancillary role in skin cancer formation (12).

Not only is the risk of onset of squamous cell carcinoma increased, but the risk of a second skin cancer is also impressive: 25% of patients will have a second lesion after 13 mo, and 50% will have a second lesion after 3.5 yr (13). This is presumably so because squamous cell carcinoma arises on the “soil” of an actinic keratosis as a precancerous epidermal lesion in sun-exposed areas of the skin (14). Other precursor lesions comprise multiple warts, keratoacanthomas (difficult to distinguish from squamous cell carcinoma even by histology) and occasionally Bowen's disease, an intraepidermal carcinoma (4).

In renal graft recipients, not only is the incidence of squamous cell carcinoma of the skin higher and does one see more frequently local recurrence as well as de novo second tumors; the skin tumors also grow more rapidly than in non-immunosuppressed individuals and they metastasize more frequently (15^,16). The incidence of skin cancer is dependent on the degree of immunosupression (10^,11). An important role of immunosuppression is also suggested by the greater frequency in graft recipients on triple (prednisolone, azathioprine, cyclosporine) as compared with double agent (prednisolone, azathioprine) immunosuppressive therapy (6). Furthermore, a 5-yr randomized controlled trial documented a lower incidence of skin cancer on low-dose than on standard-dose cyclosporine (17). In line with this notion, decreased skin cancer was noted after cessation of immunosuppressants (18). Finally, skin cancers are more frequent in the more heavily immunosuppressed heart transplant recipients (6^,19) and less frequent in the less heavily immunosuppressed liver transplant recipients (20). More detailed data will come forward from the International Transplant Skin Cancer Collaborative (ITSCC) and the Skin Care in Organ Transplant Patients (SCOP) Collaborative Group (11). The novel immunosuppressant rapamycine inhibits tumor growth in vitro and in experimental models (21)—whether it will ultimately reduce the tumor burden in transplanted patients remains to be seen, although preliminary short-term observations look encouraging (22).

The management of skin carcinoma has become an important clinical issue and was the subject of a recent review and of a consensus conference of the ITSCC and the European Skin Care in Organ Transplant Patients Network (4^,23). We refer the reader to these publications and touch here only on some points that are of specific interest to the nephrologist. The mainstay is histologically-controlled surgical excision with potential adjuvant radiotherapy and chemotherapy (bleomycin, fluorouracil, cisplatin) for metastasizing tumors. There is a role for isoretinoin (24), but the often recommended use of IFNα risks graft loss from rejection.

In view of the high risks of recurrence and the appearance of new tumors on the soil of predisposing skin lesions, the main challenge is prevention. This necessitates patient education (sun protection), follow-up, and dermatological monitoring (1^,25).

What else can one do?

One intervention, although risky, is tapering (18) or even stopping immunosuppressive medication (16). There is controlled evidence documenting benefit from topical and systemic administration of retinoids in graft recipients (26–31), although the latter possibly not without risk because of induction of IFN-γ production (32) and the resulting potential risk of acute rejection (26^,32). A rebound is also often seen when the treatment is terminated. Schaier et al. found that retinoids are highly renoprotective in experimental renal disease (33), including allografts (34). There may therefore be benefits beyond the skin, although this has not been proven in humans.

A new aspect has been the recent introduction of topical treatment with immune response modifiers, e.g., imiquimod and resiquimod (4^,35). They have been used for superficial basal-cell carcinoma (36) and actinic keratosis in nontransplanted patients (37), and more recently in graft recipients (32^,38^,39). The action of imiquimod, approved in 1997 by the US Food and Drug Administration for external genital and perianal warts, is based on a novel principle, i.e., stimulation of both the innate and adaptive arms of the immune system resulting in (locally) enhanced immune function. This action is mediated through the pathogen recognition or Toll-like receptor-7. Interaction with this receptor stimulates both the release of cytokines such as IFNα, interleukins (IL-1, IL-6, and IL-12), as well as TNFα (40); it promotes intracellular and extracellular killing by nonphagocytic and phagocytic cells (41), and activates the transcription factors AP-1 and NFκB (42^,43). In parallel the adaptive immune response is upregulated, resulting in stimulation of the TH1 and inhibition of the TH2 pathways. Langerhans-type antigen-presenting cells are activated, migrate to lymph nodes, and present antigen to T cells (44).

What is the clinical evidence for its efficacy? In a randomized, double-blind, vehicle-controlled study, the efficacy and safety of locally applied 5% imiquimod cream was examined in 36 elderly patients with actinic keratosis. The lesions were totally cleared in 84% of the patients and partially cleared in a further 8%, leaving no scarring or discoloration (45), and the success was maintained long-term (46). A heavy inflammatory reaction of the skin predicted success, suggesting that it is part of the substance's mechanism of action.

This strategy has by now been successfully applied in renal transplant recipients with premalignant skin lesions, particularly actinic keratosis and viral warts. Some observations suggest that part of the imiquimod action is related to TH1 cellular-mediated elimination of human papillomavirus by this local immune response modifier (12).

If these preliminary results are born out by more complete long-term observations, this strategy may offer the possibility to outsmart the deleterious effects of systemic immunosuppression by stimulating the immune response locally in the skin.

References

1. Morath C, Mueller M, Goldschmidt H, Schwenger V, Opelz G, Zeier M: Malignancy in renal transplantation. J Am Soc Nephrol 15: 1582-1588, 2004

2. Yang TC, Shu KH, Cheng CH, Wu MJ, Lian JD: Malignancy following renal transplantation. Zhonghua Yi Xue Za Zhi (Taipei) 61: 281-288, 1998

3. Maisonneuve P, Agodoa L, Gellert R, Stewart JH, Buccianti G, Lowenfels AB, Wolfe RA, Jones E, Disney AP, Briggs D, McCredie M, Boyle P: Cancer in patients on dialysis for end-stage renal disease: An international collaborative study. Lancet 354: 93-99, 1999

4. Euvrard S, Kanitakis J, Claudy A: Skin cancers after organ transplantation. N Engl J Med 348: 1681-1691, 2003

5. Winkelhorst JT, Brokelman WJ, Tiggeler RG, Wobbes T: Incidence and clinical course of de novo malignancies in renal allograft recipients. Eur J Surg Oncol 27: 409-413, 2001

6. Jensen P, Hansen S, Moller B, Leivestad T, Pfeffer P, Geiran O, Fauchald P, Simonsen S: Skin cancer in kidney and heart transplant recipients and different long-term immunosuppressive therapy regimens. J Am Acad Dermatol 40: 177-186, 1999

7. Hartevelt MM, Bavinck JN, Kootte AM, Vermeer BJ, Vandenbroucke JP: Incidence of skin cancer after renal transplantation in The Netherlands. Transplantation 49: 506-509, 1990

8. Ishikawa N, Tanabe K, Tokumoto T, Shimmura H, Yagisawa T, Goya N, Nakazawa H, Toma H: Clinical study of malignancies after renal transplantation and impact of routine screening for early detection: A single-center experience. Transplant Proc 32: 1907-1910, 2000

9. Euvrard S, Kanitakis J, Cochat P, Claudy A: Skin cancers following pediatric organ transplantation. Dermatol Surg 30: 616-621, 2004

10. Bouwes Bavinck JN, Hardie DR, Green A, Cutmore S, MacNaught A, O'Sullivan B, Siskind V, Van Der Woude FJ, Hardie IR: The risk of skin cancer in renal transplant recipients in Queensland, Australia. A follow-up study. Transplantation 61: 715-721, 1996

11. Ulrich C, Schmook T, Sachse MM, Sterry W, Stockfleth E: Comparative epidemiology and pathogenic factors for nonmelanoma skin cancer in organ transplant patients. Dermatol Surg 30: 622-627, 2004

12. Stockfleth E, Nindl I, Sterry W, Ulrich C, Schmook T, Meyer T: Human papillomaviruses in transplant-associated skin cancers. Dermatol Surg 30: 604-609, 2004

13. Lindelof B, Sigurgeirsson B, Gabel H, Stern RS: Incidence of skin cancer in 5356 patients following organ transplantation. Br J Dermatol 143: 513-519, 2000

14. Cockerell CJ: Pathology and pathobiology of the actinic (solar) keratosis. Br J Dermatol 149[Suppl 66]: 34-36, 2003

15. Martinez JC, Otley CC, Stasko T, Euvrard S, Brown C, Schanbacher CF, Weaver AL: Defining the clinical course of metastatic skin cancer in organ transplant recipients: A multicenter collaborative study. Arch Dermatol 139: 301-306, 2003

16. Euvrard S, Kanitakis J, Pouteil-Noble C, Disant F, Dureau G, Finaz de Villaine J, Claudy A, Thivolet J: Aggressive squamous cell carcinomas in organ transplant recipients. Transplant Proc 27: 1767-1768, 1995

17. Dantal J, Hourmant M, Cantarovich D, Giral M, Blancho G, Dreno B, Soulillou JP: Effect of long-term immunosuppression in kidney-graft recipients on cancer incidence: Randomised comparison of two cyclosporin regimens. Lancet 351: 623-628, 1998

18. Otley CC, Coldiron BM, Stasko T, Goldman GD: Decreased skin cancer after cessation of therapy with transplant-associated immunosuppressants. Arch Dermatol 137: 459-463, 2001

19. Adamson R, Obispo E, Dychter S, Dembitsky W, Moreno-Cabral R, Jaski B, Gordon J, Hoagland P, Moore K, King J, Andrews J, Rich M, Daily PO: High incidence and clinical course of aggressive skin cancer in heart transplant patients: A single-center study. Transplant Proc 30: 1124-1126, 1998

20. Frezza EE, Fung JJ, van Thiel DH: Non-lymphoid cancer after liver transplantation. Hepatogastroenterology 44: 1172-1181, 1997

21. Guba M, von Breitenbuch P, Steinbauer M, Koehl G, Flegel S, Hornung M, Bruns CJ, Zuelke C, Farkas S, Anthuber M, Jauch KW, Geissler EK: Rapamycin inhibits primary and metastatic tumor growth by antiangiogenesis: Involvement of vascular endothelial growth factor. Nat Med 8: 128-135, 2002

22. Euvrard S, Ulrich C, Lefrancois N: Immunosuppressants and skin cancer in transplant patients: Focus on rapamycin. Dermatol Surg 30: 628-633, 2004

23. Stasko T, Brown MD, Carucci JA, Euvrard S, Johnson TM, Sengelmann RD, Stockfleth E, Tope WD: Guidelines for the management of squamous cell carcinoma in organ transplant recipients. Dermatol Surg 30: 642-650, 2004

24. Lippman SM, Parkinson DR, Itri LM, Weber RS, Schantz SP, Ota DM, Schusterman MA, Krakoff IH, Gutterman JU, Hong WK: 13-cis-retinoic acid and interferon alpha-2a: Effective combination therapy for advanced squamous cell carcinoma of the skin. J Natl Cancer Inst 84: 235-241, 1992

25. London NJ, Farmery SM, Will EJ, Davison AM, Lodge JP: Risk of neoplasia in renal transplant patients. Lancet 346: 403-406, 1995

26. Rook AH, Shapiro M: Cutaneous squamous-cell carcinoma. N Engl J Med 345: 296; author reply 296-297, 2001

27. Bavinck JN, Tieben LM, Van der Woude FJ, Tegzess AM, Hermans J, ter Schegget J, Vermeer BJ: Prevention of skin cancer and reduction of keratotic skin lesions during acitretin therapy in renal transplant recipients: A double-blind, placebo-controlled study. J Clin Oncol 13: 1933-1938, 1995

28. McKenna DB, Murphy GM: Skin cancer chemoprophylaxis in renal transplant recipients: 5 years of experience using low-dose acitretin. Br J Dermatol 140: 656-660, 1999

29. Rook AH, Jaworsky C, Nguyen T, Grossman RA, Wolfe JT, Witmer WK, Kligman AM: Beneficial effect of low-dose systemic retinoid in combination with topical tretinoin for the treatment and prophylaxis of premalignant and malignant skin lesions in renal transplant recipients. Transplantation 59: 714-719, 1995

30. Yuan ZF, Davis A, Macdonald K, Bailey RR: Use of acitretin for the skin complications in renal transplant recipients. N Z Med J 108: 255-256, 1995

31. Kelly JW, Sabto J, Gurr FW, Bruce F: Retinoids to prevent skin cancer in organ transplant recipients. Lancet 338: 1407, 1991

32. Fox FE, Kubin M, Cassin M, Niu Z, Trinchieri G, Cooper KD, Rook AH: Retinoids synergize with interleukin-2 to augment IFN-gamma and interleukin-12 production by human peripheral blood mononuclear cells. J Interferon Cytokine Res 19: 407-415, 1999

33. Schaier M, Liebler S, Schade K, Shimizu F, Kawachi H, Grone HJ, Chandraratna R, Ritz E, Wagner J: Retinoic acid receptor alpha and retinoid X receptor specific agonists reduce renal injury in established chronic glomerulonephritis of the rat. J Mol Med 82: 116-125, 2004

34. Kiss E, Adams J, Grone HJ, Wagner J: Isotretinoin ameliorates renal damage in experimental acute renal allograft rejection. Transplantation 76: 480-489, 2003

35. Johnson R, Stockfleth E: Imiquimod 5% cream for the treatment of cutaneous lesions in immunocompromised patients. Acta Derm Venereol Suppl (Stockh): 23-27, 2003

36. Stockfleth E, Trefzer U, Garcia-Bartels C, Wegner T, Schmook T, Sterry W: The use of Toll-like receptor-7 agonist in the treatment of basal cell carcinoma: an overview. Br J Dermatol 149[Suppl 66]: 53-56, 2003

37. Tran H, Chen K, Shumack S: Summary of actinic keratosis studies with imiquimod 5% cream. Br J Dermatol 149 Suppl 66: 37-39, 2003

38. Ulrich C, Schmook T, Nindl I, Meyer T, Sterry W, Stockfleth E: Cutaneous precancers in organ transplant recipients: An old enemy in a new surrounding. Br J Dermatol 149[Suppl 66]: 40-42, 2003

39. Stockfleth E, Ulrich C, Meyer T, Christophers E: Epithelial malignancies in organ transplant patients: Clinical presentation and new methods of treatment. Recent Results Cancer Res 160: 251-258, 2002

40. Miller RL, Gerster JF, Owens ML, Slade HB, Tomai MA: Imiquimod applied topically: A novel immune response modifier and new class of drug. Int J Immunopharmacol 21: 1-14, 1999

41. Sieling PA, Modlin RL: Toll-like receptors: Mammalian “taste receptors” for a smorgasbord of microbial invaders. Curr Opin Microbiol 5: 70-75, 2002

42. Akira S, Takeda K, Kaisho T: Toll-like receptors: Critical proteins linking innate and acquired immunity. Nat Immunol 2: 675-680, 2001

43. Akira S: Mammalian Toll-like receptors. Curr Opin Immunol 15: 5-11, 2003

44. Suzuki H, Wang B, Shivji GM, Toto P, Amerio P, Tomai MA, Miller RL, Sauder DN: Imiquimod, a topical immune response modifier, induces migration of Langerhans cells. J Invest Dermatol 114: 135-141, 2000

45. Stockfleth E, Meyer T, Benninghoff B, Salasche S, Papadopoulos L, Ulrich C, Christophers E: A randomized, double-blind, vehicle-controlled study to assess 5% imiquimod cream for the treatment of multiple actinic keratoses. Arch Dermatol 138: 1498-1502, 2002

46. Stockfleth E, Christophers E, Benninghoff B, Sterry W: Low incidence of new actinic keratoses after topical 5% imiquimod cream treatment: A long-term follow-up study. Arch Dermatol 140: 1542, 2004

Treating Microalbuminuria—Cosmetic Exercises with Urine Chemistry or Effective Reduction of Clinical Events?

Effects of Fosinopril and Pravastatin on Cardiovascular Events in Subjects with Microalbuminuria.Circulation110: 2809-2816, 2004

F.W. Asselbergs, G.F. Diercks, H.L. Hillege, A.J. van Boven, W.M. Janssen, A.A. Voors, D. de Zeeuw, P.E. de Jong, D.J. van Veldhuisen, W.H. van Gilst; Prevention of Renal and Vascular Endstage Disease Intervention Trial (PREVEND IT) Investigators

Recently there has been intense interest in the issue of microalbuminuria as reflected by a number of reviews and guidelines. Microalbuminuria was first described by diabetologists (1^,2) as a predictor of cardiovascular and renal risk in diabetic patients (3–5). Today microalbuminuria has become a well established risk factor in nondiabetic subjects as well. Several observational studies established that in nondiabetic subjects microalbuminuria and even high normal albuminuria increase the risk of cardiovascular events and cardiovascular death (6–9). In some studies the risk increased parallel to increasing albumin excretion rates.

In diabetic subjects it has been found that even albuminuria in the upper normal range caused a striking increase of cardiovascular risk (by a factor of 9.8) and renal risk (by a factor of 12.4) (10). Similarly, in nondiabetic individuals with normoalbuminuria as well, the results of the Heart Outcomes Prevention Evaluation (HOPE) Study (11) and the Losartan Intervention For Endpoint Reduction (LIFE) Study (12) show a progressive increase of cardiovascular end points when albuminuria is higher than the approximate population median. High normal albumin excretion rates in nondiabetic subjects are equally associated with a higher risk to develop frank microalbuminuria (13), just as they are in diabetic patients (10)

In diabetic (14) as well as in nondiabetic patients with overt proteinuria it has been shown that treatment with blockers of the renin-angiotensin system diminishes the cardiovascular risk and that this goes in parallel with the reduction of proteinuria.

What had not been shown so far was whether interventions reduce cardiovascular endpoints in individuals who have nothing but microalbuminuria as a risk factor. Clarification of this point would be of considerable interest to justify screening for albuminuria in nondiabetic patients.

Asselbergs et al. selected an angiotensin-converting enzyme (ACE) inhibitor and a statin for intervention in such subjects, the latter particularly because, in the past, reduction of albuminuria during administration of statins had been seen in some (15^,16) but not all studies. It is not easy to find a suitable cohort of patients for such a trial, but the PREVEND Study provided a unique opportunity for this endeavor. In the Dutch city of Groningen, 40,856 subjects (47.8% of the inhabitants) had sent in their morning urine. A subgroup of 1439 individuals with persistent urinary albumin concentration >10 mg/L in the morning urine, BP <160/100 mmHg, and total cholesterol <8 mmol/L was randomized to receive either the ACE inhibitor fosinopril (20 mg/d) or matching placebo on the one hand, or the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor pravastatin (40 mg/d) or matching placebo on the other hand. The mean duration of follow-up was 46 mo. This population was relatively healthy: Mean age 51 yr, mean systolic BP 130/76 mmHg, mean cholesterol 5.8 mmol/L, and only 3.4% had a history of a cardiovascular event. The median urinary albumin excretion was no more than 22.8 mg/24 h (range 15.8 to 41.3). The primary endpoint was the combined incidence of cardiovascular death or hospitalization for one (or several) of the following: Nonfatal myocardial infarction or myocardial ischemia, heart failure, peripheral vascular disease, cerebrovascular accident.

The results are truly remarkable for a middle-aged population with albumin excretion in the upper normal or low microalbuminuric range, with a low prevalence of diabetes, relatively normal BP and cholesterol, as well as with few individuals having a history of cardiovascular events—and despite a sobering compliance (about 65% in this asymptomatic population).

Fosinopril caused an extremely modest reduction of BP while pravastatin lowered LDL-cholesterol substantially from 4.0 to 3.8 mmol/L. As anticipated, fosinopril lowered urinary albumin from 23.5 to 17.6 mg/24 h while pravastatin, in contrast to previous reports (15^,16), failed to do so.

What about cardiovascular endpoints? Subjects receiving fosinopril had a 40% lower incidence of the primary cardiovascular endpoint compared with the placebo arm, i.e., 3.9% versus 6.5%, but P < 0.098. The reduction of cerebrovascular accidents was striking (0.2 versus 2.3% (P < 0.05). Subjects with urinary albumin in the highest quintile (>50 mg/d) had a significantly higher risk for developing a cardiovascular event on placebo than on fosinopril. The risk in this subgroup was reduced by fosinopril from 13% to 5.2%, reducing the relative risk by 60%. In contrast, pravastatin did not lower the incidence of the primary endpoint (−13%; P = 0.649).

The data of this interventional trial are in line with observational data in the LIFE Study suggesting that reduction of albumin excretion is associated with a lower risk for the primary cardiovascular endpoint (17).

What can we learn from this trial, which assessed a relatively small cohort with very low cardiovascular risk and urinary albumin values considerably lower than in previous studies?

The HOPE Trial (18) and the Europa (EURopean trial On reduction of cardiac events with Perindopril in stable coronary Artery disease) trial (19) had shown that ACE inhibitors reduce cardiovascular endpoints in populations at high cardiovascular risk. Despite the biostatistical borderline significance, the results of the PREVEND IT study suggest that screening for urinary albumin concentrations in the high normal or microalbuminuric range will identify individuals at high cardiovascular risk who might benefit from treatment with an ACE inhibitor (but somewhat surprisingly not with a statin).

Why is microalbuminuria such a powerful predictor? Although microalbuminuria is an independent predictor of risk, it is also associated with an array of other cardiovascular risk indicators, the metabolic syndrome (20), insulin resistance (21) and a high risk of de novo diabetes (22) which is reduced, however, by renin-angiotensin system blockade (23), high body mass index (24), evidence of oxidative stress (25), smoking (26), hypertension (27), and even developmental abnormalities of the kidney (“nephron underdosing”) (28).

What is currently not well understood is the link between albuminuria and the cardiovascular risk, and this continues to be a fascinating challenge to nephrology. The time-honored Steno hypothesis ascribed the cardiovascular risk in microalbuminuric patients to microinflammation and endothelial dysfunction (29). There is indeed substantial evidence for this hypothesis in microalbuminuric patients (30). Recent findings of cross-talk between podocytes and endothelial cells in the glomerulus may provide a potential link between endothelial cell dysfunction and deranged glomerular permselectivity (31–33).

Open questions remain. Apart from the obvious need to see the results confirmed in a larger prospective study, the following issues immediately come to one's mind. Which is the best method for detecting urinary albumin in the kidney (34)? Which are the most appropriate cut-offs? In this age where economic aspects are of ever more importance in medicine we also need information on whether screening for albuminuria is cost-effective. We should also know the frequency of side effects in the long run and compliance problems. Even in the short run compliance was remarkably low in the disciplined but asymptomatic Dutch.

Nevertheless, the study raises the hope that blockade of the renin-angiotensin system provides benefits beyond BP lowering (35), even in low-risk individuals presenting with nothing but urinary albumin values in the high normal or microalbuminuric range. The public health importance of this issue is obvious.

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