BMP-4 affects the differentiation of metanephric mesenchyme and reveals an early anterior-posterior axis of the embryonic kidney

Bone morphogenetic protein-4 (BMP4), a member of the transforming growth factor-beta (TGF-beta) family, regulates several developmental processes during animal development. We have now studied the effects of BMP-4 in the metanephric kidney differentiation by using organ culture technique. Human recombinant BMP-4 diminishes the number of ureteric branches and changes the branching pattern. Our data suggest that BMP-4 affects the ureteric branching indirectly via interfering with the differentiation of the nephrogenic mesenchyme. The clear positional preference of the defects to posterior mesenchyme might reflect an early anterior-posterior patterning of the metanephric mesenchyme. The smooth muscle alpha-actin expressing cell population around the ureteric stalk, highly expressing Bmp-4 mRNA, is also expanded in kidneys treated with BMP-4. Thus, BMP-4 may be a physiological regulator of the development of the periureteric smooth muscle layer and ureteric elongation.

GDNF and its receptors in the regulation of the ureteric branching

Recent transgenic and organ culture experiments have inevitably shown that glial cell line-derived neurotrophic factor (GDNF) is a mesenchyme-derived signal for ureteric budding and branching. The signalling receptor complex for GDNF includes a dimer of Ret receptor tyrosine kinase and two molecules of GDNF family receptor alpha1. Alpha-receptors are not only needed for the ligand binding and Ret activation, but they might mediate signals without Ret. While GDNF is clearly required for ureteric branching, tissue recombination studies have shown that it is not sufficient for the completion of ureteric morphogenesis, and other signalling molecules are needed. Different experimental models have resulted in somewhat contradictory results on their molecular identity, but transforming growth factor-beta1, -beta2, fibroblast growth factor-7 and hepatocyte growth factor form, obviously among others, a redundant set of growth factors in ureteric differentiation. Three other members of the GDNF family, neurturin, artemin and persephin, are also expressed in the developing kidney, and at least neurturin and persephin promote ureteric branching in vitro, but their true in vivo roles are still unclear.

Cell lineages in the embryonic kidney: their inductive interactions and signalling molecules

The first signalling genes acting in the inductive interactions in the kidney have now been identified. Differentiation of the permanent kidney or the metanephros is critically dependent on inductive signalling between the nephrogenic mesenchyme and ureteric bud epithelium. Further inductive interactions occur between developing nephrons, interstitial stroma, endothelial cells and neurones. Glial-cell-line-derived neurotrophic factor is a signal for the ureteric bud initiation and branching, and Wnt4 is an autocrine epithelializing signal at the pretubular stage of nephron formation. The signals for renal angiogenesis and innervation are less well defined, but seem to include vascular endothelial growth factor and neurotrophins, at least. The ureteric-bud-derived signal for induction of the nephrogenic mesenchyme (to bring the cells to the condensate stage) is not yet known, but fibroblast growth factor 2 is a good candidate. None of the signalling genes identified from the embryonic kidney is specific to the organ, which raises some general questions. How do the organs develop from similar rudiments to various patterns with different cell types and functions? Does the information for organ-specific differentiation pathways retain in the epithelial or mesenchymal compartment? The present, rather fragmentary molecular data would favour the view that similar molecules acting in different combinations and developmental sequences, rather than few organ-specific master genes, could be responsible for the divergence of patterning.

Other neurotrophic factors: glial cell line-derived neurotrophic factor (GDNF)

Glial cell line-derived neurotrophic factor (GDNF) was first discovered as a potent survival factor for midbrain dopaminergic neurons and was then shown to rescue these neurons in animal models of Parkinson's disease. GDNF is a more potent survival factor for dopaminergic neurons and the noradrenergic neurons of the locus coeruleus than other neurotrophic factors, and an almost 100 times more efficient survival factor for spinal motor neurons than the neurotrophins. The members of the GDNF family, GDNF, neurturin (NTN), persephin (PSP), and artemin (ART), have seven conserved cysteine residues with similar spacing, making them distant members of the transforming growth factor-beta (TGF-beta) superfamily. Like the members of the neurotrophin family, the GDNF-like growth factors belong structurally to the cysteine knot proteins. Like neurotrophins, GDNF family proteins are responsible for the development and maintenance of various sets of sensory and sympathetic neurons but, in addition, GDNF and NTN are also responsible for the development and survival of the enteric neurons, and NTN for parasympathetic neurons. All neurotrophins bind to the p75 low-affinity receptor, but their ligand specificity is determined by trk receptor tyrosine kinases. GDNF, NTN, PSP, and ART mediate their signals via a common receptor tyrosine kinase, Ret, but their ligand specificity is determined by a novel class of glycosylphosphatidylinositol (GPI)-anchored proteins called the GDNF family receptor alpha (GFR alpha). GDNF binds preferentially to GFR alpha1, NTN GFR alpha2, ART GRF alpha3, and PSP GFR alpha4 as a co-receptor to activate Ret. GFR alpha4 has until now been described only from chicken. Although the GDNF family members signal mainly via Ret receptor tyrosine kinase, there is recent evidence that they can also mediate their signals via GFR alpha receptors independently of Ret. The GDNF family of growth factors, unlike neurotrophins, has a well-defined function outside the nervous system. Recent transgenic and organ culture experiments have clearly demonstrated that GDNF is a mesenchyme-derived signaling molecule for the promotion of ureteric branching in kidney development. NTN, ART, and PSP are also expressed in the developing kidney, and NTN and PSP induce ureteric branching in vitro, but their true in vivo role in kidney morphogenesis is still unclear.

Bioabsorbable self-reinforced poly-L-lactide, metallic, and silicone stents in the management of experimental tracheal stenosis

The aim of the present study was to compare, in rabbits, the biocompatibility and suitability of a bioabsorbable spiral stent made of self-reinforced poly-L-lactide (SR-PLLA) in the management of experimental tracheal stenosis with stents made of metal and silicone. Tracheobronchial stenosis, and its management, is still problematic because stenoses are not always amenable to surgical resection and reconstruction, especially concerning anastomotic problems and stenosis after lung transplantation. Stenosis can be handled with stenting, although the ideal stent has yet to be developed; all the stents available have their disadvantages. Because stenting of the airways can be only temporary, stents made of bioabsorbable materials, theoretically, offer benefits. Tracheal stenosis was created in rabbits by the extramucosal resection of cartilaginous arches of the cervical trachea. After a few weeks, the animals were operated on again, and those stenoses that had developed were dilated with a balloon. Stents then were implanted in the area of stenosis to keep the dilated trachea open. All the animals in the group with silicone stents had to be killed because of respiratory difficulties: their stents had a tendency to occlude because of internal encrustation, and they developed a hyperplastic polyp at the ends of the stents. The SR-PLLA and metallic stents were tolerated well, and after follow-up ended the animals were put to death. This experimental study showed that silicone stents had a tendency to occlude and that stents made of metal and of SR-PLLA were well tolerated and can be used in the management of airway stenosis.

Cell lineages in the embryonic kidney: their inductive interactions and signalling molecules

The first signalling genes acting in the inductive interactions in the kidney have now been identified. Differentiation of the permanent kidney or the metanephros is critically dependent on inductive signalling between the nephrogenic mesenchyme and ureteric bud epithelium. Further inductive interactions occur between developing nephrons, interstitial stroma, endothelial cells and neurones. Glial-cell-line-derived neurotrophic factor is a signal for the ureteric bud initiation and branching, and Wnt4 is an autocrine epithelializing signal at the pretubular stage of nephron formation. The signals for renal angiogenesis and innervation are less well defined, but seem to include vascular endothelial growth factor and neurotrophins, at least. The ureteric-bud-derived signal for induction of the nephrogenic mesenchyme (to bring the cells to the condensate stage) is not yet known, but fibroblast growth factor 2 is a good candidate. None of the signalling genes identified from the embryonic kidney is specific to the organ, which raises some general questions. How do the organs develop from similar rudiments to various patterns with different cell types and functions? Does the information for organ-specific differentiation pathways retain in the epithelial or mesenchymal compartment? The present, rather fragmentary molecular data would favour the view that similar molecules acting in different combinations and developmental sequences, rather than few organ-specific master genes, could be responsible for the divergence of patterning.Key words: inductive tissue interaction, metanephros, apoptosis, signalling molecule, cell lineage, morphogenesis.

Comparison of tissue reactions in the tracheal mucosa surrounding a bioabsorbable and silicone airway stents

BACKGROUND

Treatment of tracheobronchial stenosis is problematic. Conservative methods include stenting the stenotic area, but an ideal stent has not yet been developed. Bioabsorbable airway stents offer benefits; the extraction of the device is unnecessary, and the airway preserves its normal function after stent resorption. The aim of this study was to examine the suitability of self-reinforced poly-L-lactide as a material for an airway stent.

METHODS

A spiral airway stent made of 0.7-mm wire of self-reinforced poly-L-lactide was implanted operatively in 9 rabbits intratracheally; silicone stents served as controls.

RESULTS

Silicone stents had a tendency to become stenosed with encrustation material and to develop a hyperplastic polyp at both ends. Self-reinforced poly-L-lactide stents were well tolerated and caused no foreign body reaction, and they had a tendency to penetrate into the tracheal wall. They had disappeared at the end of the follow-up of 10 months.

CONCLUSIONS

This experimental study showed that bioabsorbable self-reinforced poly-L-lactide is a promising material for an airway stent for treatment of airway stenosis.

Distribution of glial cell line-derived neurotrophic factor mRNA in human colon suggests roles for muscularis mucosae in innervation

BACKGROUND/PURPOSE

Glial cell line-derived neurotrophic factor (GDNF) is a ligand for the receptor complex of GDNF family receptor alphas (GFRalphas) and Ret receptor tyrosine kinase, the product of a known Hirschsprung's disease gene. The aim of this study was to analyze the mRNA distribution of these genes in the developing human intestine to understand their roles in enteric innervation.

METHODS

Cryosections of fetal and newborn stomach, ileum, and colon were hybridized in situ with S35-labeled cRNA probes to GDNF, Ret, GFRalpha-1 or GFRalpha-2. GDNF mRNA levels in fetal ileum and colon were compared by reverse transcription-polymerase chain reaction (PCR).

RESULTS

GDNF mRNA expression was abundant in the muscularis mucosae of both fetal and newborn colon but was found neither in the neural plexuses nor in other regions of the intestine. Accordingly, by reverse transcription-PCR, GDNF mRNA level was many times higher in colon than ileum. Ret, GFRalpha-1 and GFRalpha-2 mRNA were expressed in the ganglionic cells of both myenteric and submucosal plexuses throughout the intestine.

CONCLUSIONS

The highly restricted distribution of GNDF mRNA suggests an important role for muscularis mucosae in the development of human enteric nervous system. Ret, GFRalpha-1, and GFRalpha-2 most likely act as GDNF receptors in colon but may have alternative ligands in other enteric segments.

Mutation analysis of the glial cell line-derived neurotrophic factor gene in Parkinson's disease

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for nigrostriatal dopaminergic, central cholinergic, and motoneurons. GDNF also prevents the neuronal loss in experimental animal models for Parkinson's disease (PD). We have now investigated the GDNF gene for possible mutations in a group of nonfamilial PD and other patients. By cleavase fragment length polymorphism (CFLP) analysis and direct sequencing of the full coding region of GDNF gene we found a novel GDNF sequence variant in 1 of 30 PD patients. The alteration does not change the predicted amino acid sequence and it was also found in 1 of 20 patients without PD, suggesting that it represents a polymorphism in the gene. No other sequence variations were found. We conclude therefore that mutations in the GDNF coding region are not commonly contributing to the pathogenesis of PD.

Autopsy in children with cancer who die while in terminal care

BACKGROUND

The purpose of this study was to find out whether autopsy of children with cancer should be recommended after terminal care, or whether in those circumstances it could be abandoned.

PATIENTS AND METHODS

One hundred pediatric patients with cancer treated at the Children's Hospital, University of Helsinki, Finland, died during 1987-92. Seventy children died while in organized terminal care. The underlying diagnoses were brain tumors (21), other solid tumors (24), and leukemias (25). The method was a retrospective analysis of patients' records and autopsy reports, in addition to a structured interview of the two parents separately.

RESULTS

Autopsy was performed in 40 (57%) of these 70 cases. It was more often performed on children dying in hospital (69%) than in those dying at home (39%). The autopsy rate also varied with the underlying disease: 68% of patients with leukemia, 50% of those with solid tumors, and 52% of those with brain tumors were autopsied. Autopsy afforded totally new medical information in 20% of cases, and important additional information in 55%. Nothing unexpected was found in 25%. Almost all the parents (94%) who agreed to autopsy felt that it was appropriate. Of both mothers and fathers, 50% felt that knowing the findings at autopsy was helpful for them, and all the parents except one mother thought that the autopsy of their child would at least be helpful to other patients.

CONCLUSIONS

Autopsy often provides important and even unexpected information in those dying after terminal care. The majority of our parents felt that autopsy was an acceptable and appropriate practice. We recommend that autopsies should be performed, with the parents' consent, even after terminal care.

Structure of the human macrophage MARCO receptor and characterization of its bacteria-binding region

The primary structure of human macrophage receptor with collagenous structure (MARCO) was determined from cDNA clones and shown to be highly similar to that of mouse (Elomaa, O., Kangas, M., Sahlberg, C. , Tuukkanen, J., Sormunen, R., Liakka, A., Thesleff, I., Kraal, G., and Tryggvason, K. (1995) Cell 80, 603-609). Features such as potential carbohydrate attachment sites in the extracellular spacer domain III and the interruption of Gly-Xaa-Yaa repeats in the collagenous domain IV were conserved between the two species. However, the human MARCO polypeptide chain lacked the intracellular cysteine present in mouse, as well as two extracellular cysteines that form interchain disulfide bonds in the murine protein. In situ hybridization showed MARCO to be strongly expressed in macrophages of several tissues of human individuals with sepsis. No expression was observed in other cell types. The bacteria-binding region of MARCO was determined in binding studies with full-length and truncated variants of MARCO, and localized to a region proximal to the cysteine-rich part of the COOH-terminal domain V. The intrachain disulfide bond pattern of domain V was established showing that these bonds are between cysteine pairs C1-C5, C2-C6, and C3-C4.

Hirschsprung's disease genes and the development of the enteric nervous system

Hirschsprung's disease or aganglionic megacolon causes chronic, congenital obstipation at an incidence of 1 per 5000 live births. Two approaches have been vital to the present understanding of the pathogenesis and genetic background of the disease: disease linkage analyses and mouse models of aganglionic megacolon. Because the increasing number of transgenic or natural mouse strains with congenital megacolon has led to mutation screening in Hirschsprung's disease patients, almost every second patient could now receive a genetic explanation for his/her disease. The known disease genes include tyrosine kinase receptor Ret, endothelin receptor B and its ligand endothelin 3. In addition, mutations have been found in the gene encoding the glial cell line-derived neurotrophic factor, the ligand for Ret, but these may only have a modifier effect. The mouse models have also provided insight into the developmental mechanisms of the normal intestinal innervation. We combine here the present clinical data on the gene mutations in Hirschsprung's disease with the experimental molecular biology data, and formulate a hypothesis on the pathogenesis of this multigenic-multifactorial disease.

The tip-top branching ureter

Organ rudiments with their epithelial bud and adjacent mesenchyme look much the same at their initial stage of differentiation. The subsequent branching of the epithelial anlagen determines the final pattern of the organs, but the mesenchyme provides essential signals for epithelial differentiation. Glial cell line derived neurotrophic factor (GDNF) has recently been shown to regulate ureteric branching morphogenesis and is thereby the first defined signalling molecule in the embryonic metanephric kidney. GDNF is expressed by the mesenchyme, binds to the tip of the ureteric bud and functions in both bud induction and bud orientation. The active receptor complex for GDNF includes the receptor tyrosine kinase Ret and a novel class of glycosylphosphatidylinositol-linked receptors, called GDNF family receptor alpha s.

Glial-cell-line-derived neurotrophic factor is required for bud initiation from ureteric epithelium

The shapes of different organs can be explained largely by two fundamental characteristics of their epithelial rudiments - the pattern of branching and the rate of proliferation. Glial-cell-line-derived neurotrophic factor (GDNF) has recently been implicated in the development of metanephric ureteric epithelium (Pichel, J. G., Shen, L., Sheng, H. Z., Granholm, A.-C., Drago, J., Grinberg, A., Lee, E. J., Huang, S. P., Saarma, M., Hoffer, B.J., Sariola, H. and Westphal, H. (1996). Nature 382, 73–76; Sanchez, M.P., Silos-Santiago, I., Frisen, J., He, B., Lira, S.A. and Barbacid, M. (1996). Nature 382, 70–73; Vega, Q.C., Worby, C.A., Lechner, M.S., Dixon, J.E. and Dressler, G.R. (1996). Proc. Nat. Acad. Sci. USA 93, 10657–10661). We have analysed the target cells of GDNF and the manner in which it controls ureteric development, and have compared it with other growth factors that have been associated with the regulation of branching morphogenesis, namely hepatocyte growth factor (HGF) and transforming growth factor-beta1 (TGFbeta1). We show that GDNF binds directly to the tips of ureteric bud branches, and that it has the ability to promote primary ureteric buds from various segments of Wolffian duct and to attract ureteric branches towards the source of GDNF. It increases cell adhesion, but is not obviously mitogenic for ureteric cells. The data indicate that GDNF is required primarily for bud initiation. Comparison of GDNF, HGF and TGFbeta1 suggests that the latter act later than GDNF, and may represent a partially redundant set of mesenchyme-derived growth factors that control ureteric development. Thus, GDNF is the first defined inducer in the embryonic metanephric kidney.

Neurotrophin mRNA expression in the developing tooth suggests multiple roles in innervation and organogenesis

To analyze the roles of neurotrophins during early development of rat teeth, we studied the expression of neurotrophin mRNAs from the initiation of first molar formation to the completion of crown morphogenesis. With RNAase protection assay all neurotrophin mRNAs were detected in embryonic teeth. In situ hybridization analysis revealed developmentally changing, distinct expression patterns for nerve growth factor (NGF) and neurotrophin-3 (NT-3), which were shown not to be regulated by or dependent on peripheral innervation. NGF mRNAs appeared in the mesenchymal target field of the tooth at the time of the trigeminal axon ingrowth (embryonic days 14-15: E14-E15), and they were also present along the pathway taken by growing trigeminal axons. NT-4/5 mRNAs were uniformly expressed in all epithelial cells, but brain-derived neurotrophic factor (BDNF) transcripts were not detected. All neurotrophins induced neurite outgrowth from E13-E16 trigeminal ganglion explants. These results suggest that NGF is involved in the guidance of trigeminal axons to embryonic teeth. In postnatal teeth, expression of NGF mRNAs, but not other neurotrophins, correlated with trigeminal axon ingrowth, proposing that NGF is involved in local sprouting and establishment of the final innervation pattern of the dental papilla and dentin. These results suggest that NGF is required for tooth innervation and that other neurotrophins may also have regulatory roles. In addition, the expression patterns of NGF, NT-3, and NT-4/5 as well as of neurotrophin receptors suggest that the neurotrophin system may also serve non-neuronal functions during tooth development.

Cloning, mRNA distribution and chromosomal localisation of the gene for glial cell line-derived neurotrophic factor receptor beta, a homologue to GDNFR-alpha

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for central dopaminergic neurons, motor neurons and several other populations of neurons in the central and peripheral nervous system. GDNF and its receptor complex of c-RET tyrosine kinase and a glycosyl-phosphatidylinositol linked protein GDNFR-alpha are of great interest due to their potential use in the therapy of Parkinson's and motoneuron diseases. We have cloned the human and rat cDNA sequences of GDNFR-beta, a new gene encoding for a 464 amino acid long homologue of GDNFR-alpha, and assign the locus of this new gene to human chromosome 8p21-22 and mouse chromosome 14D3-E1. Similarly to GDNFR-alpha, GDNFR-beta mediates GDNF-induced Ret autophosphorylation in transfected cells. By northern hybridisation we show that the transcript level of human GDNFR-beta mRNA is high in the adult brain, intestine and placenta and in fetal brain, lung and kidney. Studied by in situ hybridisation, GDNFR-beta mRNA shows in E17 rat embryo different distribution to that of GDNFR-alpha mRNA, especially, in adrenal gland, kidney and gut. In the developing nervous system, GDNFR-beta mRNA expression is restricted to certain neuronal populations, while GDNFR-alpha mRNA is widely expressed also in non-neuronal cells. The distinct tissue distribution of GDNFR-beta mRNA and its ability to mediate GDNF signal in transfected cells suggest a role in signal transduction of GDNF and, possibly, related neurotrophic factors in vivo.

TGFbeta2 knockout mice have multiple developmental defects that are non-overlapping with other TGFbeta knockout phenotypes

The growth and differentiation factor transforming growth factor-beta2 (TGFbeta2) is thought to play important roles in multiple developmental processes. Targeted disruption of the TGFbeta2 gene was undertaken to determine its essential role in vivo. TGFbeta2-null mice exhibit perinatal mortality and a wide range of developmental defects for a single gene disruption. These include cardiac, lung, craniofacial, limb, spinal column, eye, inner ear and urogenital defects. The developmental processes most commonly involved in the affected tissues include epithelial-mesenchymal interactions, cell growth, extracellular matrix production and tissue remodeling. In addition, many affected tissues have neural crest-derived components and simulate neural crest deficiencies. There is no phenotypic overlap with TGFbeta1- and TGFbeta3-null mice indicating numerous non-compensated functions between the TGFbeta isoforms.

Exclusion of the p75 neurotrophin receptor gene as a candidate gene for Meckel syndrome

Nerve growth factor receptor p75 (NGFR) gene was investigated as a potential candidate gene in Meckel syndrome (MKS) because of its important role in embryonic development, chromosomal localization adjacent to the MKS locus and Meckel syndrome-resembling findings in knock-out mice phenotype. The sequence analysis of the coding region of the gene revealed one polymorphism but no potential disease mutation. Physical mapping of the critical chromosomal region finally showed that the NGFR gene lies outside the MKS locus.

Localization of nerve cells in the developing rat tooth

Earlier studies have shown that mammalian tooth formation can take place in the absence of peripheral nerve fibers. This has been taken to indicate that neurons are not needed for mammalian tooth development. However, our recent localization of peripherin, which is a neuronal cell marker, has suggested that neuronal cell bodies may be associated with developing teeth. In this study, we have analyzed in vivo and in vitro the presence of neuronal cells in developing rat tooth germs. When E14 and E16 rat first molars (thickening of presumptive dental epithelium and bud-stage tooth germ, respectively) were cultured in vitro, peripheral trigeminal axons degenerated. However, with antibodies against peripherin and L1 neural cell adhesion protein, we detected neuronal cell bodies and their axons in the explants. Next, the expression of neurofilament light-chain (NF-L) mRNAs was studied by in situ hybridization of embryonic E12 first branchial arches and tooth germs from initiation to completion of crown morphogenesis (E13, five-day post-natal teeth). NF-L transcripts were first seen at the bud stage (E15) next to the dental epithelium at the buccal side of the tooth germ. At the cap stage (E18), NF-L mRNAs were located under the oral epithelium at some distance from dental epithelium. These expression patterns correlate to the previous localization of peripherin-positive cells and suggest that NF-L expression also revealed neuronal cells. Taken together, these results demonstrate that, in addition to projections of peripheral neurons, neuronal cells are associated with the developing teeth. Hence, it is possible that neuronal cells may participate in the regulation of mammalian tooth formation.

Differential regulation of two sets of mesonephric tubules by WT-1

Mammalian renal development undergoes two transient stages, the pronephros and the mesonephros. While the regulation of metanephric differentiation has received considerable attention, very little is known about the mode of differentiation of the mesonephros and its regulation. We have followed mesonephric differentiation to unravel the developmental mechanisms and fates of mesonephric tubules by whole-mount immunohistology using antibodies to laminin, brush border epitopes, cytokeratin-8/18, p75 neurotrophin receptor and some other renal antigens as markers. In rat and mouse embryos, two distinct sets of tubules were observed throughout mesonephric development. Four to six pairs of cranial mesonephric tubules developed as outgrowths from the Wolffian duct. The majority of tubules were caudal tubules which never fused with the Wolffian and differentiated similarly to metanephric nephrons. The murine mesonephric tubules degenerate by apoptosis, except in males where the cranial tubules become the epididymal ducts. These developmental differences between the cranial and caudal sets of tubules suggested different regulatory systems for each. Targeted disruption of the Wilms' tumour gene product, WT-1, results in renal aplasia, and a reduction in the number of mesonephric tubules (Kreidberg, J. A., Sariola, H., Loring, J., Maeda, M., Pelletier, J., Housman, D. and Jaenisch, R. (1993). Cell 74, 679–691). We therefore analysed more closely mesonephric differentiation in WT-1-deficient mice, and showed that they only develop the cranial mesonephric tubules but not the caudal ones. Thus, WT-1 appears to regulate only the development of the caudal mesonephric tubules that conceivably are formed from mesenchymal cells like the metanephric tubules. WT-1 therefore seems to be necessary for the mesenchyme to epithelium transitions at different stages of nephrogenesis.

In vivo purging of bone marrow in children with poor-risk neuroblastoma for marrow collection and autologous bone marrow transplantation

PURPOSE

To evaluate the following prospectively in poor-risk neuroblastoma (NBL) patients: (1) the feasibility and efficacy of in vivo purging of bone marrow; and (2) the outcome after autologous bone marrow transplantation (ABMT) when immunologically tumor-free, unpurged autografts were used.

PATIENTS AND METHODS

Twenty-three children with poor-risk NBL were evaluated during induction chemotherapy by repeat bone marrow examinations, including aspirate, biopsy, and an immunofluorescence method using the anti-GD2 monoclonal antibody 3A7. Nineteen patients completed the program with surgery with or without local irradiation followed by ABMT.

RESULTS

Autologous bone marrow grafts, both immunologically and cytologically clean, were obtained and used in 19 of 23 children. The overall 4-year disease-free survival of the 19 grafted children was 53%, with a toxic death rate of 16% and a posttransplant relapse rate of 37%. According to the in vivo purging efficacy of the 18 children with initial marrow disease, the following three groups were formed: patients with (1) perfect in vivo purging (n = 5); (2) eventually successful in vivo purging (n = 8); and (3) unsuccesful in vivo purging (n = 5). The 4-year DFS was 100%, 67%, and 0%, respectively (P < 0.001). The five patients with unsuccessful in vivo purging failed because of resistant/progressive bulky disease.

CONCLUSION

In patients with poor-risk NBL, in vivo purging of bone marrow by conventional chemotherapy is feasible, can be monitored, and the purging efficacy during the first 3 months after diagnosis is a strong prognostic factor reflecting tumor responsiveness to therapy. Autografting with immunologically clean, unpurged marrows gives a DFS well comparable to previous studies using ex vivo purging.