[The role of podocyte damage in the pathogenesis of glomerulosclerosis and possible repair mechanisms]. / Ruolo del danno podocitario nella patogenesi della glomerulosclerosi e possibili meccanismi di riparazione.

Converging evidence suggests that damage to podocytes plays a key role in progression towards glomerulosclerosis, in particular as the primary cause of all forms of focal segmental glomerulosclerosis (FSGS), the most common glomerular disease leading to end-stage renal disease. Any damage occurring to the complex architecture of specialized proteins that constitute the podocyte foot processes, essential to the highly specialized functions of podocytes, leads inevitably to loss of function in the glomerular filtration barrier, and ultimately to proteinuria. Recent studies have also highlighted that a reduction of the podocyte number in a damaged glomerulus is a critical factor for the development of proteinuria and glomerulosclerosis. As long as the podocyte loss is limited, restitution or repair is possible, which shows that the glomerular architecture can be remodeled. However, mature podocytes have limited capacity to divide and display all the phenotypic and functional features of highly specialized, terminally differentiated cells. A potential mechanism for podocyte replacement might be stem-cell-based regeneration, since it has been established that the developmental source of podocytes are resident renal progenitors. Podocyte damage could then be potentially repaired by a stem cell population resident in the kidney.

[The role of endothelial progenitor cells in renal disease]. / Ruolo dei progenitori endoteliali nelle malattie renali.

Recent evidence suggests that injury to the renal vasculature may play an important role in the pathogenesis of both chronic and acute ischemic kidney injury. Early alterations in peritubular capillary blood flow during reperfusion have been documented and associated with loss of normal endothelial cell function. In addition, ischemia induces alterations in endothelial cells that may promote inflammation and procoagulant activity, thus contributing to vascular congestion. Reduction of the microvasculature density increases hypoxia-mediated fibrosis and alters proper hemodynamics, which may lead to hypertension. This may play a critical role in the progression of chronic kidney disease following initial recovery from ischemia/reperfusion-induced acute kidney injury. The turnover and replacement of endothelial cells is therefore an important mechanism in the maintenance of vascular integrity also in the kidney. It is becoming clear that impaired vascular repair mechanisms as a result of a reduced number and/or impaired function of endothelial progenitor cells may contribute to renal disease. Moreover, investigators have begun to identify potential mechanisms responsible for the loss of function of endothelial progenitors in renal disease. In allografts, persistent injury results in excessive turnover of graft vascular endothelial cells. Moreover, chronic damage elicits a response that is associated with the recruitment of both leukocytes and endothelial progenitors, facilitating an overlapping process of inflammation and angiogenesis. In conclusion, angiogenesis and endothelial cell turnover play a pivotal role in renal disease and allograft rejection. Manipulation of these processes might have important implications for the development of novel therapeutic strategies in the near future.

Cell cycle-dependent expression of CXC chemokine receptor 3 by endothelial cells mediates angiostatic activity.

Endothelial cell receptors for the angiostatic chemokines IFN-gamma-inducible protein of 10 kDa (IP-10) and monokine induced by IFN-gamma (Mig) have not yet been identified, and the mechanisms responsible for the effects of these chemokines on angiogenesis are still unclear. IP-10 and Mig share a common functional receptor on activated T lymphocytes, named CXC chemokine receptor 3 (CXCR3). Using in situ hybridization and immunohistochemistry, we show that CXCR3 is expressed by a small percentage of microvascular endothelial cells in several human normal and pathological tissues. Primary cultures of human microvascular endothelial cells (HMVECs) likewise express CXCR3, although this expression is limited to the S/G2-M phase of their cell cycle. Both IP-10 and Mig, as well as the IFN-gamma-inducible T-cell alpha chemoattractant (I-TAC), which all share high-affinity binding for CXCR3, block HMVEC proliferation in vitro, an effect that can be inhibited by an anti-CXCR3 antibody. These data provide definitive evidence of CXCR3 expression by HMVEC and open new avenues for therapeutic interventions in all conditions in which an angiostatic effect may be beneficial.

Pharmacological modulation of stem cell function.

The discovery of stem cells (SC) has shed new light on the understanding of mechanisms responsible for ischemic and degenerative disorders, and opened a new field for regenerative medicine. Furthermore, dysregulation of SC self-renewal and their transformation seem to be involved also in the development of cancer, suggesting that pharmacological treatment devoted to regulate SC genomic and phenotypic functions might represent a potential new strategy even for the treatment of neoplastic disorders. SC display a promiscuous set of transcription factors and an open chromatin structure which are required to maintain their multipotentiality, while they are progressively quenched during differentiation into specific multiple lineages. The mechanisms that govern stem cell fate decisions are under tight control but remain potentially alterable. Recent studies have shown that several currently used drugs such as colony stimulating factors, statins, angiotensin-II receptor antagonists/ACE-inhibitors, Erythropoietin, nitric oxide donors, estrogens and glitazones, have modulatory activity on SC functions. These drugs mostly enhance SC survival and mobilization. Furthermore, a series of new pharmacological agents such as the chemokine receptor antagonist AMD3100, glycogen synthase kinase-3 (GSK-3) inhibitors and histone deacetylase inhibitors (HDACi), that modulate the growth, differentiation and mobilization of SC, have been recently discovered and are currently under evaluation in both in vivo experimental models and preliminary clinical trials. Thus, modulation of SC properties through pharmacological treatment represents a new field of investigation which may lead to the development of novel strategies for the treatment not only of ischemic and degenerative disorders, but also of cancer.

Bolus versus 5-day continuous infusion of cisplatin with mitomycin and vindesine in the treatment of advanced non-small cell lung cancer (NSCLC): a phase III prospective randomised trial of the Italian Oncology Group for Clinical Research (GOIRC).

The aim of this randomised trial was to compare the efficacy of bolus versus continuous infusion cisplatin combined with mitomycin C and vindesine (MVP) for chemotherapy-naive patients with stage IIIB-IV non-small cell lung cancer (NSCLC). 97 patients (49 given bolus cisplatin-arm A and 48 given continuous infusion cisplatin--arm B) were evaluable for response. In arm A, 2 patients achieved a complete response (CR), 21 achieved a partial response (PR), whilst in arm B, 14 patients achieved a PR (29%) (P = 0.07). Median survival was 8 months in both arms. Myelosuppression was the most frequent and severe toxicity, with a higher incidence of grade 3-4 leucopenia in arm A when compared with arm B (44% versus 25%). In conclusion, there is no advantage for a cisplatin 5 day infusion in the MVP regimen.

Protective effect of gangliosides on myocardial hypoxic damage in the rat.

The size of the infarct produced by ligation of the left coronary artery in the rat was decreased significantly in animals treated i.p. with 40 mg/kg per day of a ganglioside mixture (GMIX) for 7 days after surgery. Rats treated with GMIX had lower ventricular myeloperoxidase activity, indicating a lower leukocyte infiltration after infarction. The underperfused zone was also smaller in animals treated daily with GMIX 30 days after surgery. Control hearts, but not hearts obtained from animals pretreated for 15 days with 40 mg/kg per day of GMIX, released lactate dehydrogenase (LDH) during perfusion in a Langerdorff apparatus after ligation and reperfusion of the left coronary artery in vitro. Hearts made hypoxic in vitro by changing the perfusion gas to nitrogen for 20 min and later reoxygenating with 95% O2 -5% CO2 released LDH in the perfusate, but did not do so in the presence of 10 microM monosialotetraesosylganglioside. Gangliosides, therefore, seem to protect the rat heart against hypoxic damage.

[Cytokines and chemokines in nephropathies and renal transplant]. / Citochine e chemochine nelle nefropatie e nel trapianto renale.

Cytokines are soluble factors that are critical for the pathophysiology of the immune system and exhibit other important functions. Cytokines produced by type 1 helper T (Th1) lymphocytes, such as interferon (IFN)-g, play a pathogenic role in proliferative glomerulonephrites (GN), as well as in the acute rejection of kidney allografts. Cytokines produced by type 2 Th (Th2) lymphocytes, such as interleukin (IL)-4, IL-5, and IL-13), predominate in membranous GN and in minimal change disease. More recently, the pathogenic role of some members of the family of chemotactic cytokines (chemokines) in different nephropathies and in the acute and chronic rejection of kidney allografts has also been demonstrated. In particular, the chemokine MCP1/CCL2 has been found to be expressed in the kidneys of subjects with tubulo-interstitial nephritis and seems to play an important role in the sclerotic evolution of both inflammatory and metabolic nephropathies. Interactions between IP-10/CXCL10, Mig/CXCL9 and I-TAC/CXCL11 and their shared receptor, CXCR3, seem to be responsible not only for Th1 cell infiltration in acute allograft rejection and in proliferative GN, but also for mesangial cell proliferation typical of the latter condition. In proliferative GN, mesangial cells indeed express both these chemokines and their receptor. Moreover, in the kidneys of subjects suffering from chronic allograft nephropathy, IP-10/CXCL10, Mig/CXCL9 and I-TAC/CXCL11 have been found to be produced by and to act on the proxymal tubular epithelial cells, endothelial cells and smooth muscle vessel cells, suggesting their possible role in both the genesis of tubular atrophy and allograft artheriosclerosis.

Podocyte mitosis - a catastrophe.

Podocyte loss plays a key role in the progression of glomerular disorders towards glomerulosclerosis and chronic kidney disease. Podocytes form unique cytoplasmic extensions, foot processes, which attach to the outer surface of the glomerular basement membrane and interdigitate with neighboring podocytes to form the slit diaphragm. Maintaining these sophisticated structural elements requires an intricate actin cytoskeleton. Genetic, mechanic, and immunologic or toxic forms of podocyte injury can cause podocyte loss, which causes glomerular filtration barrier dysfunction, leading to proteinuria. Cell migration and cell division are two processes that require a rearrangement of the actin cytoskeleton; this rearrangement would disrupt the podocyte foot processes, therefore, podocytes have a limited capacity to divide or migrate. Indeed, all cells need to rearrange their actin cytoskeleton to assemble a correct mitotic spindle and to complete mitosis. Podocytes, even when being forced to bypass cell cycle checkpoints to initiate DNA synthesis and chromosome segregation, cannot complete cytokinesis efficiently and thus usually generate aneuploid podocytes. Such aneuploid podocytes rapidly detach and die, a process referred to as mitotic catastrophe. Thus, detached or dead podocytes cannot be adequately replaced by the proliferation of adjacent podocytes. However, even glomerular disorders with severe podocyte injury can undergo regression and remission, suggesting alternative mechanisms to compensate for podocyte loss, such as podocyte hypertrophy or podocyte regeneration from resident renal progenitor cells. Together, mitosis of the terminally differentiated podocyte rather accelerates podocyte loss and therefore glomerulosclerosis. Finding ways to enhance podocyte regeneration from other sources remains a challenge goal to improve the treatment of chronic kidney disease in the future.

Novel strategies of regenerative medicine using chemical compounds.

Many diseases and/or physical defects due to injury result in the loss of specialized cells within organ systems and lead to organ system dysfunction. The ultimate goal of cell-based therapies is to regenerate and restore normal function. Populations of embryonic, fetal, adult stem cells and inducible pluripotent stem cells generated by reprogramming of adult cells show promise for the treatment of a variety of diseases. In addition, the recent advancements in adult stem cell biology in both normal and pathological conditions have led to the identification of some intrinsic and extrinsic factors that govern the decision between self renewal versus differentiation of tissue-resident adult stem cells. This is of primary importance for the design of an approach of stem cell-based therapy focused on their in vivo modulation by conventional chemical and biological therapeutics capable to stimulate endogenous cell regeneration. Such therapeutics can act in vivo to promote cell survival, proliferation, differentiation, reprogramming and homing of stem cells or can modulate their niches. In this review, we will highlight the burst of recent literature on novel perspectives of regenerative medicine and their possible clinical applications.

CXCR3 and alphaEbeta7 integrin identify a subset of CD8+ mature thymocytes that share phenotypic and functional properties with CD8+ gut intraepithelial lymphocytes.

BACKGROUND: We previously demonstrated the existence of two distinct subsets of T cell receptor (TCR)alphabeta+CD8alphabeta+ single positive (SP) cells in human postnatal thymus which express the chemokine receptor CCR7 or CXCR3 and migrate in vitro in response to their specific ligands. AIM: To investigate whether these two CD8+ thymocyte subsets had distinct peripheral colonisation. METHODS: TCRalphabeta+CD8+ SP cells were obtained from normal postnatal thymus, mesenteric lymph node (LNs), small bowel, and peripheral blood (PB) specimens. Cells were then evaluated for expression of surface molecules, cytolytic potential, telomere length, and profile of cytokine production. RESULTS: CD8+CCR7+CXCR3- thymocytes exhibited CD62L, in common with those which localise to LNs. In contrast, CD8+CCR7-CXCR3+ thymocytes lacked CD62L but exhibited CD103, similar to intraepithelial lymphocytes (IELs) present in the gut mucosa where the CXCR3 ligand, CXCL10, and the CD103 ligand, E-cadherin, are highly and consistently expressed. In addition, thymocytes and gut CD8+CXCR3+CD103+ cells showed comparable telomere length, which was higher than that of PB CXCR3+CD8+ T cells. However, both of these populations contained perforin and granzyme A, and displayed the ability to produce interferon gamma and interleukin 2. Of note, CXCR3 deficient, in comparison with wild-type C57Black/6, mice showed decreased proportions of CD3+CD8alphabeta+ and increased proportions of CD3+CD8alphaalpha+ lymphocytes at gut level. Moreover, adoptive transfer of CD3+CD8alphabeta+ thymocytes from wild-type into CXCR3 deficient mice resulted in a significant increase in CD3+CD8alphabeta+ T cells in the gut mucosa but not in other tissues. CONCLUSIONS: The results of this study demonstrate the existence of a previously unrecognised subset of TCRalphabeta+CD8alphabeta+ SP CXCR3+CD103+ thymocytes which share phenotypic and functional features with CD8+ IELs, thus suggesting the possibility of their direct colonisation of the gut mucosa.

Catecholamines modulate growth and differentiation of human preosteoclastic cells.

Using a clonal cell line of human osteoclast precursors (FLG 29.1 cells), that after treatment with 12-O-tetradecanoyl phorbol 13-acetate (TPA) show many functional characteristics of osteoclasts, we demonstrated that catecholamines act as inducers of osteoclast maturation in vitro and as stimulators of osteoclast activity via the binding to beta 2 adrenergic receptors. Scatchard analysis of 125I-labelled iodocyanopindolol to untreated (undifferentiated) or TPA-treated (differentiated) FLG 29.1 cells revealed the presence of a single high-affinity site with a Kd value around 24 pM and 8 pM respectively and with superimposable binding capacity (1.18 fmol/mg protein). Catecholamines increased in a dose-dependent fashion the intracellular cyclic AMP (cAMP) accumulation in both undifferentiated and TPA-treated FLG 29.1 cells. Pretreatment of untreated and TPA-treated FLG 29.1 cells with propranolol inhibited the catecholamine effect on cAMP accumulation, while pretreatment with clonidine had no effect. Catecholamines also reduced cell proliferation, increased tartrate-resistant acid phosphatase (TRAcP) activity, interleukin 6 (IL-6) production, multi-nuclearity and response to salmon calcitonin (sCT) in undifferentiated FLG 29.1 cells. In differentiated FLG 29.1 cells only IL-6 release was induced by catecholamine treatment. These findings support a potential role for catecholamines in modulating osteoclast differentiation and mature osteoclast activity.

Comparison of immuno- and HPLC-assays for the measurement of urinary collagen cross-links.

Pyridinoline (Pyr) and deoxypyridinoline (D-Pyr) are two cross-links of collagen molecules, that are present in the extracellular matrix and released during its degradation. Pyr is present in bone and cartilage, but not in significant amounts in other connective tissues and D-Pyr appears to be specific for bone tissue. Therefore, the urinary excretion of Pyr and D-Pyr might be a sensitive marker of bone matrix degradation. For the determination of urinary Pyr and D-Pyr two methods are available: a chromatographic method (HPLC) by which it is possible to measure separately Pyr and D-Pyr, and a new immunoassay which measures total free and low molecular weight pyridinoline released in the urine. We compared the results obtained by HPLC analysis of 205 urinary samples from normal subjects and patients affected by various bone disorders with those obtained by the immunoassay. The overall correlation coefficient between the results obtained by the two methods was 0.34. When calculated in a range of pyridinoline concentrations from 0 to 30, 30 to 60, and over 60 pmol/mumol creatinine the correlation coefficient was respectively -0.094, 0.38, and 0.12. The two methods yielded variable profiles in the detection of circadian rhythms and these differences did not segregate with normal or pathological conditions. We conclude that the immunoassay proposed for the determination of urinary collagen cross-links is not immediately applicable to clinical use. The improvement of the antibody specificity will probably contribute to replace the HPLC method with the immunoassay.

Inducible nitric oxide synthase expression in vascular and glomerular structures of human chronic allograft nephropathy.

Nitric oxide (NO) plays an important role in the cytotoxic mechanisms responsible for acute renal allograft rejection, where macrophages produce high levels of inducible nitric oxide synthase (iNOS). By contrast, both the source and the role of NO in chronic allograft nephropathy (CAN) are still unclear. In this study, the expression of iNOS mRNA and protein was assessed in the kidneys of patients with graft failure due to chronic rejection. As controls, kidney specimens were obtained from patients undergoing nephrectomies for primary renal tumours, and from patients suffering from IgA nephropathy or mesangial-proliferative glomerulonephritis. In normal kidneys, iNOS production was absent or limited to a low signal, while it was found only in the inflammatory infiltrate of kidneys affected by glomerulonephritis, as assessed by immunohistochemistry and in situ hybridization. In contrast, in CAN, iNOS protein was localized not only in inflammatory cells, but also in vascular, glomerular, and, more rarely, tubular structures. Accordingly, in situ hybridization localized iNOS mRNA in both macrophages and lymphocytes, as well as in vascular structures and glomeruli. Double immunostaining for iNOS and a-smooth muscle actin (a-SMA) or von Willebrand factor (vWf) revealed that smooth muscle cells were the main vascular source of iNOS, while both mesangial and inflammatory cells were immunostained at the glomerular level. These data demonstrate that macrophages and lymphocytes are not the only source of iNOS mRNA and protein in human CAN. Vascular smooth muscle and mesangial cells also synthesize iNOS, raising the question of heterogeneous regulation and function of iNOS in this disease.

Functional and structural interactions between osteoblastic and preosteoclastic cells in vitro.

Osteoblasts are involved in the bone resorption process by regulating osteoclast maturation and activity. In order to elucidate the mechanisms underlying osteoblast/preosteoclast cell interactions, we developed an in vitro model of co-cultured human clonal cell lines of osteoclast precursors (FLG 29.1) and osteoblastic cells (Saos-2), and evaluated the migratory, adhesive, cytochemical, morphological, and biochemical properties of the co-cultured cells. In Boyden chemotactic chambers, FLG 29.1 cells exhibited a marked migratory response toward the Saos-2 cells. Moreover, they preferentially adhered to the osteoblastic monolayer. Direct co-culture of the two cell types induced: (1) positive staining for tartrate-resistant acid phosphatase in FLG 29.1 cells; (2) a decrease of the alkaline phosphatase activity expressed by Saos-2 cells; (3) the appearance of typical ultrastructural features of mature osteoclasts in FLG 29.1 cells; (4) the release into the culture medium of granulocyte-macrophage colony stimulating factor. The addition of parathyroid hormone to the co-culture further potentiated the differentiation of the preosteoclasts, the cells tending to fuse into large multinucleated elements. These in vitro interactions between osteoblasts and osteoclast precursors offer a new model for studying the mechanisms that control osteoclastogenesis in bone tissue.

Localization of endothelin-converting enzyme-1 in human kidney.

The distribution of endothelin-converting enzyme-1 (ECE-1) mRNA and protein was investigated in human kidney excised because of renal tumors. ECE-1 immunoreactivity was detected by immunohistochemistry throughout the different areas of the kidney in the vascular and tubular structures. In the cortex, ECE-1 immunostaining was present in the endothelial surface of arcuate and interlobular arteries and in arterioles. Weak specific immunoreactivity was present over some proximal and distal tubules. Few endothelial glomerular cells contained ECE-1 protein. In the medulla, ECE-1 immunoreactivity was observed in the vasa recta bundles and capillaries. ECE-1 immunostaining was also detected in the outer and inner medullary collecting ducts and thin limbs of Henle's loops. Immunohistochemical detection of the von Willebrand factor on adjacent sections confirmed the endothelial nature of the vascular cells that exhibited ECE-1 immunostaining. The distribution patterns of ECE-1 mRNA, investigated by in situ hybridization, appeared similar to that obtained by immunohistochemistry in the cortical and medullary vasculature and in different portions of the nephron. Northern blot and densitometric analyses demonstrated that ECE-1 mRNA levels were quantitatively similar in both the renal cortex and medulla. These results demonstrate that vascular endothelial and tubular epithelial cells in the cortex and medulla of the human kidney synthesize ECE-1, which, in turn, may play an important role in regulating endothelin production in physiological and pathological conditions.

Angiotensin II stimulates the synthesis and secretion of vascular permeability factor/vascular endothelial growth factor in human mesangial cells.

The aim of the present study was to evaluate the role of angiotensin II (AngII) in regulating both the gene expression and secretion of vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) in human mesangial cells (HMC) in culture. Densitometric analysis of Northern blot experiments demonstrated that AngII increases VPF/VEGF mRNA in a dose-dependent manner. The levels of VPF/VEGF mRNA in HMC exposed for 3 h to 10 nM, 100 nM, and 1 microM AngII were, respectively, 1.5-, 2.3-, and 1.6-fold higher than control cells (P < 0.05, P < 0.0001, and P < 0.05, respectively). This effect was blocked by the pretreatment with losartan (1 microM) (P < 0.005), a selective antagonist of the AngII AT1 receptor. Reverse transcription-PCR performed in HMC using oligonucleotide primers specific for all VPF/VEGF mRNA splicing variants detected three bands corresponding to VEGF 189, 165, and 121. Exposure of the cells to 100 nM AngII resulted in an increase of all the mRNA transcripts. Furthermore, in situ hybridization experiments showed that the levels of hybridization signals for VPF/VEGF mRNA resulted consistently higher in HMC exposed for 3 h to AngII (100 nM) than in control cells. The effects of AngII on the secretion of VPF/VEGF peptide in the culture medium of HMC were assessed using an enzyme-linked immunosorbent assay method. When different concentrations of AngII were tested in 3-h stimulation periods, the percentage of increase in the levels of released VPF/VEGF was significantly higher than control cells for AngII concentrations of 100 nM (62 +/- 11% mean +/- SD, P < 0.0001) and 1 microM (17.3 +/- 10.9%, P < 0.01). The pretreatment of HMC with losartan (1 microM) prevented the increase of VPF/VEGF secretion induced by AngII (100 nM) (AngII 54.7 +/- 3.9 pg/microg DNA versus AngII + losartan 37.8 +/- 3.6 pg/microg DNA, mean +/- SD, P < 0.005). VPF/VEGF protein was time dependently released in the culture medium under basal, steady-state conditions. Compared with control cells, AngII (100 nM) caused a significant increase in the levels of released VPF/VEGF after 3 and 6 h (control 33.8 +/- 1.7 pg/microg DNA at 3 h, 42.1 +/- 1.1 at 6 h, and 117.7 +/- 10 at 24 h; AngII 54.7 +/- 3.9 at 3 h, P < 0.0001, 61.6 +/- 8.7 at 6 h, P < 0.05, and 144.7 +/- 22.7 at 24 h, NS; mean +/- SD). According to the results obtained from enzyme-linked immunosorbent assay experiments, Western blot analysis showed that the intensity of the 19-kD band corresponding to VPF/VEGF was 1.5-fold higher in AngII (100 nM)-treated HMC than in control cells. Similarly, immunocytochemistry on HMC demonstrated an increase in intracellular VPF/VEGF immunostaining in response to AngII treatment (100 nM) compared with control cells. This study demonstrated that in HMC, AngII augmented the levels of VPF/VEGF gene expression and stimulated the synthesis and secretion of its peptide by activating AT1 receptors. Through these mechanisms, AngII may affect the functions of endothelial cells during the development of renal diseases involving the glomerulus.

High CD30 ligand expression by epithelial cells and Hassal's corpuscles in the medulla of human thymus.

CD30 is a member of tumor necrosis factor (TNF) receptor superfamily that is expressed by activated T cells in the presence of interleukin-4 (IL-4). Although CD30 can mediate a variety of signals, CD30-deficient mice have impaired negative selection of T cells, suggesting that at least in the context of murine thymus, CD30 is a cell death-mediating molecule. The ligand for CD30 (CD30L) is a membrane-associated glycoprotein related to TNF, which is known to be expressed mainly by activated T cells and other leukocytes. However, the nature of CD30L-expressing cells involved in the interaction with CD30+ thymocytes is unclear. We report here that in postnatal human thymus the great majority of CD30+ cells are double positive (CD4+CD8+), activated, IL-4 receptor-expressing T cells which selectively localize in the medullary areas. Moreover, many medullary epithelial cells and Hassal's corpuscles in the same thymus specimens showed unusually high expression of CD30L in comparison with other lymphoid or nonlymphoid tissues. These findings provide additional information on the nature and localization of CD30+ thymocytes and show that epithelial cells are the major holder of CD30L in the thymic medulla.

Role for interactions between IP-10/Mig and CXCR3 in proliferative glomerulonephritis.

The mechanisms responsible for mesangial cell proliferation in proliferative glomerulonephritis are only partially understood. This article reports the results of an immunohistochemical study showing high expression of the chemokine receptor CXCR3 by mesangial cells of patients with IgA nephropathy, membranoproliferative glomerulonephritis, or rapidly progressive glomerulonephritis. CXCR3 was also detectable by flow cytometry in cultured human mesangial cells, in which it appeared to be functionally active, as determined by the ability of its ligand, the (interferon-gamma)-inducible protein of 10 kD (IP-10) to induce intracellular Ca2+ influx. Both IP-10 and the monokine induced by interferon-gamma (Mig) were also effective in inducing proliferation of human mesangial cells. These data suggest that in patients with proliferative glomerulonephritis, the chemokines IP-10 and/or Mig not only may act as chemoattractants for infiltrating mononuclear cells in the inflamed tissue, but also may directly induce the proliferation of mesangial cells.

Signal transduction by the chemokine receptor CXCR3: activation of Ras/ERK, Src, and phosphatidylinositol 3-kinase/Akt controls cell migration and proliferation in human vascular pericytes.

Hepatic stellate cells (HSC) and glomerular mesangial cells (MC) are tissue-specific pericytes involved in tissue repair, a process that is regulated by members of the chemokine family. In this study, we explored the signal transduction pathways activated by the chemokine receptor CXCR3 in vascular pericytes. In HSC, interaction of CXCR3 with its ligands resulted in increased chemotaxis and activation of the Ras/ERK cascade. Activation of CXCR3 also stimulated Src phosphorylation and kinase activity and increased the activity of phosphatidylinositol 3-kinase and its downstream pathway, Akt. The increase in ERK activity was inhibited by genistein and PP1, but not by wortmannin, indicating that Src activation is necessary for the activation of the Ras/ERK pathway by CXCR3. Inhibition of ERK activation resulted in a decreased chemotactic and mitogenic effect of CXCR3 ligands. In MC, which respond to CXCR3 ligands with increased DNA synthesis, CXCR3 activation resulted in a biphasic stimulation of ERK activation, a pattern similar to the one observed in HSC exposed to platelet-derived growth factor, indicating that this type of response is related to the stimulation of cell proliferation. These data characterize CXCR3 signaling in pericytes and clarify the relevance of downstream pathways in the modulation of different biologic responses.

Interferon-inducible protein 10, monokine induced by interferon gamma, and interferon-inducible T-cell alpha chemoattractant are produced by thymic epithelial cells and attract T-cell receptor (TCR) alphabeta+ CD8+ single-positive T cells, TCRgammadelta+ T cells, and natural killer-type cells in human thymus.

Strong reactivity for interferon-inducible protein 10 (IP-10), monokine induced by interferon gamma (Mig), and interferon-inducible T-cell alpha chemoattractant (I-TAC) was found in epithelial cells mainly localized to the medulla of postnatal human thymus. The CXC chemokine receptor common to the 3 chemokines (CXCR3) was also preferentially expressed in medullary areas of the same thymuses and appeared to be a property of 4 distinct populations: CD3+ T-cell receptor (TCR) alphabeta+ CD8+ single-positive (SP) T cells, TCRgammadelta+ T cells, natural killer (NK)-type cells, and a small subset of CD3+(low) CD4+ CD8+ TCRalphabeta+ double-positive (DP) T cells. IP-10, Mig, and I-TAC showed chemoattractant activity for TCRalphabeta+ CD8+ SP T cells, TCRgammadelta+ T cells, and NK-type cells, suggesting their role in the migration of different subsets of mature thymocytes during human thymus lymphopoiesis.