Type IV collagen production by rat pulmonary alveolar epithelial cells

Maintenance and repair of the pulmonary alveolar basement membrane are critical processes for preserving normal alveolar structure and function. To elucidate the mechanisms that control type IV collagen production by pulmonary alveolar epithelial cells, type II pneumocytes from rat lungs were isolated and maintained in tissue culture as monolayers. Using Northern blot analysis and metabolic labeling, we found that the cultured epithelial cells express type IV collagen mRNA and incorporate [3H]proline into type IV collagen. To determine the effects of phenotype on control of type IV collagen synthesis, we took advantage of the well-described observation that isolated type II cells lose their distinctive type II features when cultured on plastic in serum-containing medium for 7 days and assume an appearance more like that of type I epithelial cells. We found that [3H]proline incorporation into type IV collagen increased from day 1 to day 2 and thereafter decreased gradually up to day 7. Despite this decrease in [3H]proline incorporation, type IV collagen mRNA increased over the same period. If the loss of type II cell characteristics was prevented by culturing the cells in EHS matrix, a basement membrane-like extracellular matrix, there was little increase in relative abundance of type IV collagen mRNA as compared with cells cultured on plastic. We therefore conclude that type IV collagen production by isolated pulmonary alveolar epithelial cells is controlled, at least in part, by translational or post-translational mechanisms. Furthermore, the full type II cell phenotype is not required for expression of type IV collagen genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of mineralocorticoid and glucocorticoid receptor mRNA along the nephron

In the present study, a competitive polymerase chain reaction (PCR) technique was used to quantitate the relative levels of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) mRNA in microdissected nephron segments from the rat kidney and of MR mRNA from isolated principal and intercalated collecting duct cells from rabbit. RNA was isolated from cells and isolated tubules, cDNA was synthesized, and receptor cDNA was coamplified by PCR with a competitive control template. beta-Actin PCR products were also obtained from each nephron segment studied, to assess variations in RNA extraction and cDNA synthesis. MR mRNA, as determined by this competitive PCR technique, was 10-fold more abundant in cortical collecting duct (CCD), outer medullary collecting duct, and inner medullary collecting duct segments than in the proximal tubule and thick ascending limb segments (P < 0.05). Both principal and beta-intercalated cells of the CCD contained detectable levels of MR mRNA, although the levels in the principal cells were threefold higher (P < 0.01). GR mRNA was twofold more abundant in glomeruli, proximal tubule, and thick ascending limb segments than in the collecting duct segments (P < 0.05). In general, the distribution pattern of MR and GR mRNA is consistent with the distribution of adrenal corticosteroid function along the nephron.

Vascular adventitial cell expression of collagen I messenger ribonucleic acid in anti-glomerular basement membrane antibody-induced crescentic nephritis in the rabbit. A cellular source for interstitial collagen synthesis in inflammatory renal disease

BACKGROUND

Scarring in the interstitial compartment of the renal cortex heralds a poor prognosis in many forms of renal injury, however, the mechanism through which glomerular inflammation leads to interstitial scarring is not understood. In a model of anti-GBM disease in the rabbit, development of crescentic glomerulonephritis is associated with marked interstitial fibrosis and decreased renal function. We previously demonstrated that collagen accumulation in the model was preceded by increases in collagen I and IV mRNA and that these changes were primarily extraglomerular at early time points when inflammation was predominantly intraglomerular. In order to identify the cellular origins of extraglomerular collagen synthesis in this model, in situ hybridization using an alpha 2(I) procollagen probe was performed.

EXPERIMENTAL DESIGN

A 602 bp rabbit alpha 2(I) procollagen cDNA was cloned using a PCR strategy and sequenced. The nucleotide sequence of the coding region was 94% identical with the human alpha 2(I) procollagen sequence. Northern blots were performed to define conditions of specific hybridization of the anti-sense riboprobe. Tissue sections from normal rabbit kidneys and from kidneys 4, 5, 7, 10 and 14 days after injection of anti-GBM antibody were hybridized with 35S-labeled sense and anti-sense riboprobes. Cells containing alpha 2(I) mRNA were identified by autoradiography and mRNA abundance was quantitated by grain density.

RESULTS

No specific hybridization was detected with the sense probe at any time. alpha 2(I) mRNA was undetectable with the anti-sense probe in normal kidney sections. In contrast, the anti-sense probe hybridized specifically at all time points after induction of anti-GBM disease. In agreement with previous filter hybridization studies, on day 4, when inflammation was predominantly intraglomerular, cells in the periarterial adventitial compartment of renal cortex hybridized strongly. At later time points, labeling was also present in the interstitial spaces, the periglomerular region, in Bowman's space and in the glomerular tuft itself.

CONCLUSIONS

We conclude that perivascular adventitial cells are among the first to respond to glomerular inflammation and represent a pool of cells that subsequently contribute to interstitial and glomerular scarring.

Time course of stimulation of renal renin messenger RNA by furosemide

Renin secretion responds rapidly to a variety of stimuli; however, reported changes in renal renin messenger RNA (mRNA) levels in vivo have been observed only after prolonged stimulation. Studies were designed to test whether rapid changes in renin mRNA levels can be produced in vivo. In the first series, Sprague-Dawley rats received furosemide (10 mg/kg) intraperitoneally and a low sodium diet (0.05% sodium); renin secretion was significantly stimulated at 8 or 16 hours after treatment, but renin mRNA levels did not change. In a second series, rats were pretreated with deoxycorticosterone acetate (200 mg/kg) and saline drinking water for 3 days and then killed 0, 2, 4, 8, or 48 hours after furosemide administration. The renin mRNA level was unchanged at 2 hours but was stimulated twofold at 4 and 8 hours and threefold at 48 hours. In additional animals, the response of renin mRNA 4 hours after furosemide was found not to be potentiated by the converting enzyme inhibitor quinapril (5 mg/kg). The results demonstrate that with acute stimulation, renin mRNA levels lag 2-4 hours behind the change in plasma renin levels.

Laminin expression in the mouse lung increases with development and stimulates spontaneous organotypic rearrangement of mixed lung cells

The recent establishment of a role for laminin in mouse lung organogenesis (Schuger et al. 1990a,b, 1991) prompted us to study its expression in the developing lung. Laminin A and B chains were detected in the murine lung from the first hours of development onward. In situ hybridization of mRNA as well as SDS-PAGE studies of lung cells in monoculture indicated that both epithelium and mesenchyme produce complete laminin molecules. Quantitative analysis of the in situ hybridization studies showed a gradual increase in laminin expression during development which was further supported by immunohistochemistry and ELISA. The overall pattern of expression suggested that the effects of laminin in morphogenesis were not restricted to a particular stage of development. Furthermore, the increase in expression during late development supported a role for the molecule in the fetal lung, which was not previously established. We next determined whether the increase in laminin production modulated the behavior of fetal lung cells as compared with their embryonic counterparts. We previously showed that organotypic pattern formation does not occur in cultures of mixed embryonic lung cells unless exogenous laminin is added (Schuger et al., 1990b). Organotypic pattern formation is the result of cell sorting into epithelial and mesenchymal compartments and further rearrangement in a pattern resembling the tissue of origin. In the present study, we demonstrated that organotypic pattern formation occurs spontaneously in cultures of mixed fetal lung cells, which express high laminin levels. Pattern formation was abolished by antibodies to laminin. These studies suggest a correlation between laminin expression and the ability of lung cells in culture to reproduce normal tissue patterns. We conclude that laminin is critical for epithelial-mesenchymal recognition and further morphogenic interaction during both the embryonic and fetal stages of lung development.

Application of polymerase chain reaction techniques to study of rabbit renin gene expression

Studies were performed to develop techniques to assess renin mRNA in a single microdissected juxtaglomerular apparatus (JGA) of rabbit using the polymerase chain reaction (PCR) method of amplification of cDNA sequences. In preliminary studies synthetic oligonucleotide primers corresponding to regions in the rat renin cDNA sequence, which are highly conserved between mouse, rat, and man, were found to yield good amplification efficiency with a rat renin cDNA template, but little product was observed with rabbit cDNA template. We therefore employed a nested primer PCR cloning technique to clone an 839 base pair portion of the rabbit renin cDNA to obtain species-specific sequence information for primer design. Here we report the nucleotide sequence of a partial rabbit renin cDNA clone and the use of species-specific primers that permit semiquantitative assessment of rabbit mRNA levels in the single JGA.

Intracellular signaling of transcription and secretion of type IV collagen after angiotensin II-induced cellular hypertrophy in cultured proximal tubular cells

Physiologic concentrations of angiotensin II (AII) can induce cellular hypertrophy in murine proximal tubular epithelium (MCT cells). This response is characterized by an increase in cell size, new protein synthesis, and by the secretion of new basement membrane type IV collagen in the absence of cellular proliferation. The present study was undertaken to evaluate the second messengers of these AII-induced cellular events with special reference to the increase in type IV collagen secretion. In initial experiments we observed that pretreatment of MCT cells with agents that increase concentrations of intracellular cAMP, like forskolin, dibutyryl cAMP, and isobutyl-methyl-xanthine abolish AII-induced amino acid incorporation, but have no effect on control cells or on their proliferation. In addition, 10(-8) M AII significantly decreased the concentration of intracellular cAMP. Phorbolesters were without significant effect on the hypertrophy or proliferation of AII-stimulated MCT cells or their rested controls. The transfection of MCT cells with reporter genes containing regulatory elements for type IV collagen revealed that the stimulatory effects of AII on collagen type IV depend, at least to some extent, on an increase in gene transcription. Agents increasing intracellular cAMP concentrations inhibited the AII-induced increase in transcription and secretion of collagen type IV, but had no effect on MCT cells grown in media without AII. Our findings provide evidence that AII-induced changes in tubular epithelium leading to the secretion of type IV collagen are mediated by a decrease in intracellular cAMP.

Cyclosporin A stimulates transcription and procollagen secretion in tubulointerstitial fibroblasts and proximal tubular cells

The brief study described in this report was undertaken to determine whether cyclosporin A had any direct effect on the expression of tubulointerstitial procollagens in cultured renal cells. Our findings indicate that murine tubulointerstitial fibroblasts secreted significantly more procollagen type I after the addition of cyclosporin A, whereas syngeneic proximal tubular cells expressed significantly more types I and IV procollagen after cyclosporin stimulation. These increases in procollagen gene product correlated concordantly with changes in the levels of cytoplasmic mRNA with procollagen-specific cDNA probes. Transfection of these fibroblasts and proximal tubular cells with chimeric gene constructs containing enhancer/promoter elements for alpha2(I) and alpha 1(IV) procollagen linked to a chloramphenicol acetyltransferase reporter gene indicates that the stimulatory effect of cyclosporin on procollagen expression depends, at least to some extent, on an increase in transcriptional activity.

Analysis of alpha 1 (I) procollagen alpha 1 (IV) collagen, and beta-actin mRNA in glomerulus and cortex of rabbits with experimental anti-glomerular basement membrane disease. Evidence for early extraglomerular collagen biosynthesis

Renal cortical and glomerular mRNA for alpha 1 (I) and alpha 1 (IV) collagen were measured by filter hybridization during experimental anti-glomerular basement membrane disease in the rabbit. The abundance of alpha 1 (IV) mRNA was 5 times greater in total RNA isolated from glomeruli as compared with whole renal cortex from normal rabbits. In contrast, there was no difference in the relative amounts of alpha 1 (I) procollagen mRNA in these two fractions. Four days after the administration of anti-glomerular basement membrane antisera, a time histologically characterized by glomerular inflammatory cell infiltration without crescent formation, beta-actin mRNA were increased 17-fold in glomeruli and 4-fold in whole renal cortex. Renal cortical mRNA for alpha 1 (I) and alpha 1 (IV) were increased 7-fold (p = 0.07) and 9-fold (p less than 0.05), respectively compared with normal rabbit kidney cortex. In contrast, there was no significant difference in the abundance of these mRNA in glomeruli at day 4. By day 7, cortical alpha 1 (I) and alpha 1 (IVP mRNA had increased 17- and 10-fold, respectively, and these transcripts had increased 13- and 7-fold in glomeruli. Cortical alpha 1 (I) mRNA remained elevated for 35 days. These data show that large changes in collagen mRNA levels occur early in this model of crescentic nephritis in the rabbit, and that extraglomerular collagen mRNA accumulates very rapidly when glomerular inflammation occurs. Extraglomerular collagen synthesis associated with intraglomerular inflammation may help to explain the common association of interstitial fibrosis with glomerulonephritis, particularly in the periglomerular area.

Rat intestinal basement membrane synthesis. Epithelial versus nonepithelial contributions

Mesenchymal-epithelial interactions play an important role during tissue differentiation and morphogenesis. The basement membrane, which separates these compartments, appears to be critical to these interactions by providing a substratum for cell adhesion, promoting cell polarity and the differentiated phenotype. Unlike other epithelia, gut enterocytes adhere to, and migrate along a thin basement membrane as they differentiate along the crypt-villus axis with a turnover rate of 48 to 72 hours (rat). The relative importance of the enterocytes or of the mesenchymal cells of the lamina propria to the maintenance of the basement membrane is unknown. As indirect indicators of basement membrane biosynthesis, we have measured, by filter hybridization with labeled cDNA probes, the relative abundance of mRNAs for laminin and collagen IV chains in enterocyte fractions representing the crypt-villus gradient of differentiation and in cells of the underlying lamina propria. In confirmation of a gradient, mRNA for histone H2B was present as a decreasing gradient from crypt to villus, the crypt fraction containing the mitotically active enterocytes being most enriched for this transcript and, in contrast, the mRNA for beta-actin was present as an increasing gradient from crypt to villus, paralleling the abundance of microvillus core structures. The mRNAs for alpha 1(IV) and alpha 2(IV) collagen and laminin B1 and B2 chains were most abundant in the lamina propria. Little, if any, collagen IV mRNA was detectable in the enterocyte fractions. In contrast, laminin B1 and B2 mRNAs were enriched in crypt enterocytes but the steady-state level of these transcripts decreased in the superficial villus enterocyte fractions. These data suggest that the components of the intestinal basement membrane are synthesized by both mesenchymal and entodermal-derived cells. Alterations in the intestinal basement membrane structure and in cell adhesion during enterocyte differentiation may be partly mediated by changes in laminin synthesis by the enterocyte.

In situ hybridization reveals temporal and spatial changes in cellular expression of mRNA for a laminin receptor, laminin, and basement membrane (type IV) collagen in the developing kidney

The appearance of extracellular matrix molecules and their receptors represent key events in the differentiation of cells of the kidney. Steady-state mRNA levels for a laminin receptor, the laminin B1, B2, and A chains, and the alpha 1-chain of collagen IV (alpha 1[IV]), were examined in mouse kidneys at 16 d gestation and birth, when cell differentiation is active, and 1-3 wk after birth when this activity has subsided. Northern analysis revealed that mRNA expression of laminin receptor precedes the alpha 1(IV) and laminin B chains whereas laminin A chain mRNA expression was very low. In situ hybridization reflected this pattern and revealed the cells responsible for expression. At 16 d gestation, laminin receptor mRNA was elevated in cells of newly forming glomeruli and proximal and distal tubules of the nephrogenic zone located in the kidney cortex. These cells also expressed mRNA for alpha 1(IV) and laminin chains. At birth, mRNA expression of receptor and all chains remained high in glomeruli but was reduced in proximal and distal tubules. At 1 wk after birth, expression was located in the medulla over collecting ducts and loops of Henle. Little expression was detectable by 3 wk. These results suggest that cellular expression of steady-state mRNA for laminin receptor, laminin, and collagen IV is temporally linked, with laminin receptor expression proceeding first and thereafter subsiding.

Increased deposition of basement membrane macromolecules in specific vessels of the spontaneously hypertensive rat

The genetically determined chronic hypertension manifested in the Spontaneously Hypertensive Rat (SHR) serves as a useful animal model for the study of human essential hypertension. One of the earliest morphologic changes observed in the vasculature of the SHR is the development of a thickened subendothelial space (SES). Neither the biochemical composition nor the anatomic distribution of this early subendothelial deposit has been definitively determined. By combining morphologic, immunologic, and molecular biological approaches, it was demonstrated that by 15 weeks the acellular subendothelial thickening in the vasculature of the SHR results at least in part from the increased synthesis and deposition of basement membrane macromolecules. Moreover, rather than being manifest systemically, this early connective tissue lesion appears to be localized primarily to the aorta and major branches off the aortic arch.

Macrorestriction mapping of COL4A1 and COL4A2 collagen genes on human chromosome 13q34

The genes for the alpha-1 and alpha-2 chains of type IV collagen (COL4A1 and COL4A2) map to the same chromosomal band (13q34) and have a high degree of nucleotide homology. We have used pulsed field gel electrophoresis and cloned COL4A1 and COL4A2 DNA fragments as molecular probes to construct a 1200-kb macrorestriction map which encompasses both genes. The two genes are located within a 340-kb region with the 3' end of COL4A2 and the 5' region of COL4A1 separated by at least 100 kb but not more than 160 kb. These genes, therefore, are two members of a gene cluster on chromosome 13q34.

Characterization of the promoter for the alpha 1 (IV) collagen gene. DNA sequences within the first intron enhance transcription

Two overlapping clones spanning 19 kilobase pairs (kb) of the 5' end of the alpha 1 (IV) collagen gene were isolated and found to contain a single exon which encoded the 5'-untranslated sequence and 84 base pairs of the signal peptide. The 5' end of this exon was determined to be the 5' end of the transcript by S1 nuclease protection and primer extension. The nucleotide sequence of 1 kb of the 5'-flanking DNA was extremely G + C-rich (greater than 70%) and contained two GC boxes and a putative cAMP regulatory sequence. The transcriptional regulation of the alpha 1 (IV) gene was studied with chimeric gene constructs utilizing 2.5 kb of the 5'-flanking sequence coupled to the gene for chloramphenicol acetyltransferase. Transfection of this construct into differentiating F9 cells resulted in low chloramphenicol acetyltransferase activity compared to beta-actin or Rous sarcoma virus long terminal repeat promoters, although these cells produce large amounts of collagen IV. Inclusion of a 2.7-kb sequence 2.3 kb downstream from the first exon in either orientation increased the transcription of the chloramphenicol acetyltransferase construct approximately 10-fold in F9 cells, but was not active in NIH 3T3 cells, which synthesize little collagen IV. These results indicate the presence of an enhancer within the first intron, which increases the expression of this gene.

Structure of the amino-terminal portion of the murine alpha 1(IV) collagen chain and the corresponding region of the gene

Collagen IV, the major structural component of basement membranes, is composed of two genetically distinct polypeptide chains, alpha 1(IV) and alpha 2(IV). We have isolated a 522-base-pair (bp) cDNA to the 5' portion of the murine alpha 1(IV) chain mRNA from a library constructed by specific primer extension of poly(A)+ RNA from differentiated F9 cells. This cDNA includes 141 bp of 5' untranslated sequence and encodes a signal peptide plus a portion of the amino-terminal cross-linking (7 S) domain. This cDNA clone was used to obtain the 5' portion of the murine alpha 1(IV) gene from which the nucleotide sequence of exons 1-6 was determined. Exon 1 (234 bp) codes for the 5' untranslated sequence, and the first 28 residues of the protein. The 5' untranslated sequence is highly conserved between the mouse and human species and has the potential to form three mutually exclusive stem-loop structures which may play a role in post-transcriptional regulation. Exons 2-6, which code for the 7 S domain, were found to be 60, 90, 45, and 63 bp in size. The exon structure for the helical portion of the 7 S domain is different from that of the major helical domain, suggesting that they evolved differently.

Altered mRNA expression of basement membrane components in a murine model of polycystic kidney disease

Basement membranes surround the renal tubules and have been shown to limit their distension in vitro. Therefore, it has been postulated that a defect in a basement membrane component(s) underlies the pathogenesis of polycystic kidney disease. Here we have studied a murine model of congenital polycystic kidney disease and found by immunohistology, that the components of the peri-cyst basement membrane appeared to diminish with time. We also measured mRNA levels for collagen IV and laminin, and found a different pattern than in the normal mouse kidney. In normal kidneys, mRNA levels for the B1 and B2 chains of laminin were maximal at birth, and at 1 week for the alpha 1(IV) chain of collagen IV. With all three chains, the levels then rapidly declined. In contrast, mRNA for the alpha 1(IV) chain in congenital polycystic kidneys was half normal 1 week after birth and then increased. Laminin B1 and B2 chain mRNA's were 80% of normal at 1 week but were maintained at that level. As a control, beta-actin mRNA was examined and found to remain constant in both normal and diseased kidneys. In situ hybridization of cRNA probes for the alpha 1(IV) chain confirmed that cells associated with cysts were the principal source of expression of these basement membrane mRNAs. Thus, there exists an abnormal regulation of basement membrane gene expression in congenital polycystic kidney disease. The first stage is characterized by reduced levels of expression. In the second stage, the levels are abnormally high, perhaps representing a compensatory synthesis of basement membrane as cysts enlarge.

The glomerular distribution of type IV collagen and laminin in human membranous glomerulonephritis

The glomerular distribution of type IV collagen and laminin, the major collagenous and noncollagenous components of the glomerular basement membrane, was studied by immunofluorescence microscopy in idiopathic and lupus membranous glomerulonephritis. Affinity-purified antibodies against type IV collagen reacted preferentially with the inner aspect and irregularly with the adjacent outer area of the thickened basement membrane. In contrast, laminin was detected along the inner aspect of the glomerular basement membrane, in subepithelial basement membrane protrusions ("spikes"), and in the newly formed basement membrane layer above the immune deposits. We conclude that type IV collagen and laminin do not codistribute in the newly formed matrix. This aberrant antigenic distribution may reflect a loss of coordinate biosynthesis or degradation of these matrix components by visceral epithelial cells.

Partial structure of the human alpha 2(IV) collagen chain and chromosomal localization of the gene (COL4A2)

We have isolated a 2.1-kb cDNA clone from a human placental library encoding part of the alpha 2 chain of collagen IV, a major structural protein of basement membranes. The DNA sequence encodes 446 amino acids in the triple-helical domain plus the 227 amino acids of the carboxy-terminal globular domain. The latter structure is composed of two homologous subdomains and is highly conserved between the alpha 1 and alpha 2 chains. The triple-helical domain contained seven interruptions of the Gly-X-Y repeat and these interruptions were in general larger than their counterparts in the alpha 1 chain. DNA from human rodent hybrid cell lines was analyzed under conditions in which there was no cross-hybridization of the alpha 2(IV) cDNA probe with the gene for the alpha 1(IV) collagen chain. An EcoRI fragment characteristic of the alpha 2 chain had a concordance of 0.97 with chromosome 13. This result was confirmed and extended with in situ localization of the gene at 13q34. Since the alpha 1(IV) gene has previously been localized to 13q34, the two type IV collagen genes reside in the same chromosome region (13q34), possibly in a gene cluster. The presence of the genes for type IV collagen chains on chromosome 13 excludes a primary role for these genes in adult polycystic kidney disease and X-linked forms of hereditary nephritis.

Studies on the formation of glomerular immune deposits in brown Norway rats injected with mercuric chloride

Brown Norway rats injected with mercuric chloride (HgCl2) develop autoantibodies which immunolocalize along the glomerular basement membrane at first in a linear pattern and then in a granular pattern. The aim of this study was to characterize the specificity of these antibodies and to investigate the mechanisms responsible for the formation of granular immune deposits in the subepithelial zone of the glomerular basement membrane. The rats were found to develop circulating anti-laminin, anti-type IV collagen, anti-heparan sulfate proteoglycan, and anti-entactin antibodies. Antibodies against laminin and type IV collagen were found in relatively high titers in the sera and were specifically concentrated in the nephritic kidneys. Antibodies eluted from the nephritic kidneys with either linear or granular deposits reacted with basement membrane antigens synthesized and secreted by cultured rat glomerular visceral epithelial cells. Thus, in this model, the interaction of anti-laminin and type IV collagen antibodies with antigens secreted by glomerular visceral epithelial cells might, together with other mechanisms, contribute to the formation of granular immune deposits in the subepithelial part of the glomerular basement membrane.

Genes for basement membrane proteins are coordinately expressed in differentiating F9 cells but not in normal adult murine tissues

We have obtained cDNA clones coding for the A, B1, and B2 chains of laminin by screening a cDNA library prepared from mouse EHS tumor poly(A)RNA in the lambda gt11 expression vector with polyclonal antibody against denatured laminin. These cDNA clones were used in combination with a cDNA clone coding for the alpha 1 type IV collagen chain to study the regulation of genes for these basement membrane proteins in retinoic acid-induced differentiating mouse F9 teratocarcinoma cells and in various adult murine tissues. The levels of mRNA for the laminin A, B1, and B2 chains and for the alpha 1 type IV collagen chain were increased simultaneously and reached a maximum at almost the same time during the differentiation of F9 cells, suggesting coordinate expression in these cells. The tissue levels of mRNA encoding for the basement membrane components, however, varied considerably. The highest level of the B1 chain mRNA was observed in kidney, whereas, the levels of mRNA for A and B2 chains were highest in heart. Almost the same levels of expression of the alpha 1(IV) collagen mRNA were found in kidney, lung, and heart. The results indicate that the expression of genes for the basement membrane proteins is not coordinately regulated in these tissues. It is thus possible that different subunit structures of the laminin molecule may exist in tissues.

The role of neutrophil membrane glycoprotein GP-150 in neutrophil adherence to endothelium in vitro

We have previously described two patients with a congenital defect in neutrophil function characterized by an inability to form pus. The patients' neutrophils lack a membrane glycoprotein of mol wt 150,000 daltons (GP-150) on analysis by SDS-PAGE. This glycoprotein is part of a membrane antigen complex recognized by the murine monoclonal antibody (MoAb) 60.3. Addition of MoAb 60.3 to normal neutrophils produces defects in chemotaxis and phagocytosis in vitro similar to those observed in the patients. Since neutrophil adherence to vascular endothelium is prerequisite to neutrophil emigration in vivo, we examined the interaction of the patients' neutrophils and normal neutrophils treated with MoAb 60.3 with cultured endothelium. Adherence was determined as the percentage of 51Cr-labeled purified peripheral blood neutrophils which remained adherent to plastic wells or endothelial monolayers after a 45-minute incubation at 37 degrees C. The percentage of neutrophils from patient 1 remaining adherent to uncoated, fibronectin-coated, or laminin-coated plastic was similar to that observed in normal neutrophils (55% to 84% adherence with normal neutrophils v 73% to 78% adherence with the patient's neutrophils and 63% to 82% adherence with MoAb 60.3-treated normal neutrophils). The adherence of the neutrophils from patient 1 and MoAb 60.3-treated normal neutrophils to human or bovine endothelium in serum-free medium was also not significantly different from that observed in normal neutrophils (less than 10% adherence with normal, MoAb 60.3-treated, and patient neutrophils). In medium containing 10% autologous or heterologous human plasma, however, the adherence of neutrophils from patient 1 or MoAb 60.3-treated normal neutrophils to endothelial monolayers was significantly reduced (35% +/- 7% of normal neutrophils in seven experiments). Although phorbol myristate acetate (PMA) (10 ng/mL) and calcium ionophore A23187 (10(-5) mol/L) markedly increased the adherence of normal neutrophils to endothelial monolayers in serum-free medium (40% to 85% adherence), neither agent increased the adherence of the neutrophils from patient 1 or normal neutrophils treated with MoAb 60.3 (less than 5% adherence). The adherence of PMA-activated neutrophils from patient 2 to endothelial monolayers was also markedly decreased when compared with that of normal neutrophils. Postsecretory cell-free supernatants from PMA-activated normal neutrophils failed to augment adherence of neutrophils from patient 1 (less than 5% adherence).(ABSTRACT TRUNCATED AT 400 WORDS)

The composition of glomerulosclerosis. I. Studies in focal sclerosis, crescentic glomerulonephritis, and membranoproliferative glomerulonephritis

The composition of glomerulosclerosis was examined in focal sclerosis, membranoproliferative glomerulonephritis, and crescentic glomerulonephritis, using antisera specific for laminin and collagen types III and IV. Mesangial sclerosis consisted exclusively of extracellular matrix found in normal glomeruli, as did small synechiae in focal sclerosis and all synechiae in membranoproliferative glomerulonephritis. The large synechiae in focal sclerosis and all stages of the developing crescents associated with vasculitis contained mainly interstitial collagen, type III, a component not found in normal glomeruli. In the latter there were also disruptions of Bowman's capsule and an increase in the number of periglomerular interstitial cells. These observations suggested that glomerulosclerosis varied in composition and distribution, and some types of crescentic glomerulonephritis may have arisen from either cells resident in the glomerulus or cells coming from the interstitial space.

Evidence for a stem cell common to hematopoiesis and its in vitro microenvironment: studies of patients with clonal hematopoietic neoplasia

The origin and nature of cells forming the in vitro microenvironment in long-term cultures of human marrow were studied in five patients with clonal myeloproliferative disorders who were heterozygous for glucose-6-phosphatase dehydrogenase (G6PD). The results showed that cells in the adherent stromal layer forming the in vitro microenvironment were derived from the same clonal progenitors involved by the neoplasm in the four patients whose diseases originated in multipotent stem cells. In contrast, stromal cells were derived from normal progenitors in a patient with acute non-lymphocytic leukemia whose clone showed differentiative expression confined to cells in the granulocytic lineage. Mixing experiments demonstrated that the G6PD type displayed by the adherent marrow stromal cells was not obscured by contaminating non-adherent hematopoietic cells or marrow fibroblasts. The data suggest the existence of a pluripotent cell in normal hematopoiesis that gives rise to hematopoietic cells and to their micro-environment.