Emphatically Lymphatic

Clinicopathological study of expression of lymphatic vessels in renal allograft biopsy after treatment for acute rejection

BACKGROUND

Lymph vessel expression is related to inflammatory cell infiltration, around renal tubules in acute rejection episodes (ARE) of transplanted kidneys. However, there is little information on the lymph vessels after treatment of an ARE, particularly in relation to renal function and histological findings.

PATIENTS AND METHODS

We investigated 13 cases of ARE diagnosed by kidney transplant biopsy performed from 1997 to 2005 within 3 years of transplantation. Treatment of the ARE lead to an improved serum creatinine level in all cases. There was neither an ABO-incompatible nor an acute humoral rejection case. Lymphatic vessels in re-biopsies were examined using immunohistochemical staining with D2-40 antibody that detected lymphatic endothelium. Re-biopsy cases in which the baseline creatinine had increased by more than 20% despite treatment were considered the severe group; the others, as the stable group. The relation between lymphatic vessel density (LVD) and renal function was examined using Banff scores.

RESULTS

LVD was significantly higher in the severe than the stable group. The expression of lymph vessels versus the Banff score showed a direct relation: greater Banff scores showed higher expressions of lymph vessels.

CONCLUSIONS

The expression of lymph vessels in renal allograft specimens after treatment of an ARE was related to deterioration of renal function and inflammatory cell invasion. We plan a further examination of the relationship between the expression of lymph vessels and long-term prognosis.

Differential expression of proteoglycans in tissue remodeling and lymphangiogenesis after experimental renal transplantation in rats

Background

Chronic transplant dysfunction explains the majority of late renal allograft loss and is accompanied by extensive tissue remodeling leading to transplant vasculopathy, glomerulosclerosis and interstitial fibrosis. Matrix proteoglycans mediate cell-cell and cell-matrix interactions and play key roles in tissue remodeling. The aim of this study was to characterize differential heparan sulfate proteoglycan and chondroitin sulfate proteoglycan expression in transplant vasculopathy, glomerulosclerosis and interstitial fibrosis in renal allografts with chronic transplant dysfunction.

Methods

Renal allografts were transplanted in the Dark Agouti-to-Wistar Furth rat strain combination. Dark Agouti-to-Dark Agouti isografts and non-transplanted Dark Agouti kidneys served as controls. Allograft and isograft recipients were sacrificed 66 and 81 days (mean) after transplantation, respectively. Heparan sulfate proteoglycan (collXVIII, perlecan and agrin) and chondroitin sulfate proteoglycan (versican) expression, as well as CD31 and LYVE-1 (vascular and lymphatic endothelium, respectively) expression were (semi-) quantitatively analyzed using immunofluorescence.

Findings

Arteries with transplant vasculopathy and sclerotic glomeruli in allografts displayed pronounced neo-expression of collXVIII and perlecan. In contrast, in interstitial fibrosis expression of the chondroitin sulfate proteoglycan versican dominated. In the cortical tubular basement membranes in both iso- and allografts, induction of collXVIII was detected. Allografts presented extensive lymphangiogenesis (p<0.01 compared to isografts and non-transplanted controls), which was associated with induced perlecan expression underneath the lymphatic endothelium (p<0.05 and p<0.01 compared to isografts and non-transplanted controls, respectively). Both the magnitude of lymphangiogenesis and perlecan expression correlated with severity of interstitial fibrosis and impaired graft function.

Interpretation

Our results reveal that changes in the extent of expression and the type of proteoglycans being expressed are tightly associated with tissue remodeling after renal transplantation. Therefore, proteoglycans might be potential targets for clinical intervention in renal chronic transplant dysfunction.

Multipotent mesenchymal stem cells acquire a lymphendothelial phenotype and enhance lymphatic regeneration in vivo

BACKGROUND

The importance and therapeutic value of stem cells in lymphangiogenesis are poorly understood. We evaluated the potential of human and murine mesenchymal stem cells (MSCs) to acquire a lymphatic phenotype in vitro and to enhance lymphatic regeneration in vivo.

METHODS AND RESULTS

We assessed the lymphendothelial differentiation of human and murine MSCs after induction with supernatant derived from human dermal microvascular endothelial cells, isolated lymphatic endothelial cells, and purified vascular endothelial growth factor (VEGF)-C in vitro. We used human or murine progenitor MSC lines and then characterized the lymphatic phenotype by morphology, migratory capacity, and the expression of lymphatic markers such as Prox-1, podoplanin, Lyve-1, VEGF receptor-2, and VEGF receptor-3. Using a murine lymphatic edema model, we assessed the potential of these cells to form a functional lymphatic vasculature in vivo after injection of syngeneic MSCs. Incubation with supernatant from lymphatic endothelial cells induced an endothelium-like morphology and the expression of lymphendothelial markers in both human and murine MSCs in vitro. MSCs showed migratory activity along a VEGF-C gradient, which was enhanced by VEGF-C conditioning. In vivo, the local application of MSCs resulted in a significant decrease in edema formation (-20.1%; P<0.01 versus untreated tails) after 3 weekly cell injections and restored the drainage of intradermally injected methylene blue after 7 weekly injections.

CONCLUSIONS

MSCs were capable of expressing a lymphatic phenotype when exposed to lymph-inductive media and purified VEGF-C. Migratory activity toward VEGF-C in vitro suggests homing capability in vivo. Restoration of lymphatic drainage after injection of MSCs in a lymphedema model indicates that MSCs play a role in lymphatic regeneration. The potential clinical application of MSC in wound healing and reduction of lymphatic edema warrants further research.

Schlemm??s Canal Endothelia, Lymphatic, or Blood Vasculature?

In the human eye, the final barrier for aqueous humor to cross before returning to systemic circulation is the inner wall of Schlemm's canal. Unfortunately, the specific contribution of the inner wall to total outflow resistance in the conventional pathway is unknown in both normal and glaucomatous eyes. To better understand inner wall physiology, we contrasted it with 2 specialized continuous endothelia, initial lymphatic, and blood capillary endothelia. Specifically, we compare their developmental origin, morphology, junctional complexes, microenvironment, and physiologic responses to different biomechanical factors. Our evaluation concludes that the inner wall of Schlemm's canal is unique, sharing extraordinary characteristics with both types of specialized endothelia in addition to having distinctive features of its own.

Lymphatic neoangiogenesis in human renal allografts: results from sequential protocol biopsies

Neoangiogenesis of lymphatic vessels may be important for the cellular immune response in renal transplants. To determine the prevalence and chronology of lymph vessel proliferation and its relation to cellular infiltrates and allograft function, we analyzed sequential protocol biopsies (n = 162), taken at 6, 12 and 26 weeks after transplantation. Biopsies were stained with an antibody against podoplanin and lymphatic vessel density was quantified per square millimeter. The prevalence of lymph vessel-positive biopsies and the lymph vessel density were similar at 6, 12 and 26 weeks after transplantation. Biopsies with acute cellular rejection showed no significantly different lymph vessel density compared to those below the threshold for acute rejection or chronic allograft nephropathy. While lymphatic neoangiogenesis was equally prevalent in biopsies with and without infiltrates, the lymph vessel density was significantly higher in areas with cellular infiltrates than in areas without. Graft function at 1 year after transplantation was better in cases with lymph vessels in their infiltrates compared to cases with lymph vessel-free infiltrates. In conclusion, lymphangiogenesis not only shows a clear association with cellular infiltrates but might also have an impact on the pathogenicity of these cellular infiltrates.