Mono- and biallelic germline variants of DNA glycosylase genes in colon adenomatous polyposis families from two continents

Recently, biallelic germline variants of the DNA glycosylase genes MUTYH and NTHL1 were linked to polyposis susceptibility. Significant fractions remain without a molecular explanation, warranting searches for underlying causes. We used exome sequencing to investigate clinically well-defined adenomatous polyposis cases and families from Finland (N=34), Chile (N=21), and Argentina (N=12), all with known susceptibility genes excluded. Nine index cases (13%) revealed germline variants with proven or possible pathogenicity in the DNA glycosylase genes, involving NEIL1 (mono- or biallelic) in 3 cases, MUTYH (monoallelic) in 3 cases, NTHL1 (biallelic) in 1 case, and OGG1 (monoallelic) in 2 cases. NTHL1 was affected with the well-established, pathogenic c.268C>T, p.(Gln90Ter) variant. A recurrent heterozygous NEIL1 c.506G>A, p.(Gly169Asp) variant was observed in two families. In a Finnish family, the variant occurred in trans with a truncating NEIL1 variant (c.821delT). In an Argentine family, the variant co-occurred with a genomic deletion of exons 2 – 11 of PMS2. Mutational signatures in tumor tissues complied with biological functions reported for NEIL1. Our results suggest that germline variants in DNA glycosylase genes may occur in a non-negligible proportion of unexplained colon polyposis cases and may predispose to tumor development.

Colorectal cancer incidences in Lynch syndrome: a comparison of results from the prospective lynch syndrome database and the international mismatch repair consortium

OBJECTIVE

To compare colorectal cancer (CRC) incidences in carriers of pathogenic variants of the MMR genes in the PLSD and IMRC cohorts, of which only the former included mandatory colonoscopy surveillance for all participants.

METHODS

CRC incidences were calculated in an intervention group comprising a cohort of confirmed carriers of pathogenic or likely pathogenic variants in mismatch repair genes (path_MMR) followed prospectively by the Prospective Lynch Syndrome Database (PLSD). All had colonoscopy surveillance, with polypectomy when polyps were identified. Comparison was made with a retrospective cohort reported by the International Mismatch Repair Consortium (IMRC). This comprised confirmed and inferred path_MMR carriers who were first- or second-degree relatives of Lynch syndrome probands.

RESULTS

In the PLSD, 8,153 subjects had follow-up colonoscopy surveillance for a total of 67,604 years and 578 carriers had CRC diagnosed. Average cumulative incidences of CRC in path_MLH1 carriers at 70 years of age were 52% in males and 41% in females; for path_MSH2 50% and 39%; for path_MSH6 13% and 17% and for path_PMS2 11% and 8%. In contrast, in the IMRC cohort, corresponding cumulative incidences were 40% and 27%; 34% and 23%; 16% and 8% and 7% and 6%. Comparing just the European carriers in the two series gave similar findings. Numbers in the PLSD series did not allow comparisons of carriers from other continents separately. Cumulative incidences at 25 years were < 1% in all retrospective groups.

CONCLUSIONS

Prospectively observed CRC incidences (PLSD) in path_MLH1 and path_MSH2 carriers undergoing colonoscopy surveillance and polypectomy were higher than in the retrospective (IMRC) series, and were not reduced in path_MSH6 carriers. These findings were the opposite to those expected. CRC point incidence before 50 years of age was reduced in path_PMS2 carriers subjected to colonoscopy, but not significantly so.

Maternal ancestry and hematological cancer risk: case-control study in an Argentinean population

Aim: We investigated the role of maternal ancestry in neoplastic hematological malignancies (HMs) risk in a population from Central Argentina. Materials & methods: We analyzed 125 cases with HMs and 310 controls from a public hospital, and a set of 202 colorectal, breast, lung, and hematologic cancer patients from a private hospital. Results: A decreased risk for HMs was associated with the Native American haplogroup B2 (odds ratio = 0.49; 95% CI: 0.25-0.92; p = 0.02). The sub-Saharan African parahaplogroup L was associated with higher susceptibility for disease (odds ratio = 3.10; 95% CI: 1.04-9.31; p = 0.043). Although the mean ancestral proportions in the total studied population was as published (61.7% Native American, 34.6% European and 3.7% African), an unequal distribution was observed between hospitals. Conclusion: We confirmed the tri-hybrid nature of the Argentinean population, with proportions varying within the country. Our finding supports the notion that associated haplogroup is population and cancer specific.

The consensus Immunoscore adapted to biopsies in patients with locally advanced rectal cancer: Potential clinical significance for a “Watch and Wait” strategy

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Background: We investigated whether an adaptation to rectal biopsies of the recently validated consensus Immunoscore, could predict the response to neoadjuvant treatment and delineate clinical responders that could benefit from a “Watch and Wait” (W&W) strategy with acceptable outcomes. Methods: Initial biopsies from 273 patients with locally advanced rectal cancer (LARC) treated by neoadjuvant chemoradiotherapy (nCRT) followed by Total Mesorectal Excision (TME), were immunostained for CD3+ and cytotoxic CD8+ T cells and quantified by digital pathology to determine the Immunoscore within pre-treatment Biopsy (ISB). Expression level of 44 immune related genes post-neoadjuvant treatment was investigated by Nanostring technology (n = 64 patients). Results were correlated with response to neoadjuvant treatment, disease free survival (DFS) and time to recurrence (TTR). Prognostic performance of ISB was finally assessed in 73 LARC treated by W&W strategy. Results: ISB Low, Intermediate and High were respectively observed in 23.3, 50.4 and 26.3 % of the cohort. ISB was positively and significantly correlated with the response to nCRT, as evaluated by Dworak classification (P = .0034), ypTNM (P = .0003), down-staging (P = .0014), and neoadjuvant rectal (NAR) score, (P < .0001). ISB status was also positively associated with the degree of local immune activation post-neoadjuvant treatment. ISB High patients were at low risk of relapse, with 5-year DFS rates of 81.1 % (CI, 71.3-92.1 %) as compared to 57.8 % (CI, 45.9-72.9 %) in ISB low patients. In multivariate analysis, ISB was the only significant parameter at presentation associated with DFS (High vs Low: P = .001). Among W&W patients, significant difference was observed for TTR according to ISB status (High vs Low: P = .025). Conclusions: ISB could provide a reliable estimate of the response to nCRT and risk of recurrence in LARC patients' treated by TME or W&W strategy.

From colorectal cancer pattern to the characterization of individuals at risk: Picture for genetic research in Latin America

Colorectal cancer (CRC) is one of the most common cancers in Latin America and the Caribbean, with the highest rates reported for Uruguay, Brazil and Argentina. We provide a global snapshot of the CRC patterns, how screening is performed, and compared/contrasted to the genetic profile of Lynch syndrome (LS) in the region. From the literature, we find that only nine (20%) of the Latin America and the Caribbean countries have developed guidelines for early detection of CRC, and also with a low adherence. We describe a genetic profile of LS, including a total of 2,685 suspected families, where confirmed LS ranged from 8% in Uruguay and Argentina to 60% in Peru. Among confirmed LS, path_MLH1 variants were most commonly identified in Peru (82%), Mexico (80%), Chile (60%), and path_MSH2/EPCAM variants were most frequently identified in Colombia (80%) and Argentina (47%). Path_MSH6 and path_PMS2 variants were less common, but they showed important presence in Brazil (15%) and Chile (10%), respectively. Important differences exist at identifying LS families in Latin American countries, where the spectrum of path_MLH1 and path_MSH2 variants are those most frequently identified. Our findings have an impact on the evaluation of the patients and their relatives at risk for LS, derived from the gene affected. Although the awareness of hereditary cancer and genetic testing has improved in the last decade, it is remains deficient, with 39%–80% of the families not being identified for LS among those who actually met both the clinical criteria for LS and showed MMR deficiency.

Evaluation of MLH1 variants of unclear significance

Inactivating mutations in the MLH1 gene cause the cancer predisposition Lynch syndrome, but for small coding genetic variants it is mostly unclear if they are inactivating or not. Nine such MLH1 variants have been identified in South American colorectal cancer (CRC) patients (p.Tyr97Asp, p.His112Gln, p.Pro141Ala, p.Arg265Pro, p.Asn338Ser, p.Ile501del, p.Arg575Lys, p.Lys618del, p.Leu676Pro), and evidence of pathogenicity or neutrality was not available for the majority of these variants. We therefore performed biochemical laboratory testing of the variant proteins and compared the results to protein in silico predictions on structure and conservation. Additionally, we collected all available clinical information of the families to come to a conclusion concerning their pathogenic potential and facilitate clinical diagnosis in the affected families. We provide evidence that four of the alterations are causative for Lynch syndrome, four are likely neutral and one shows compromised activity which can currently not be classified with respect to its pathogenic potential. The work demonstrates that biochemical testing, corroborated by congruent evolutionary and structural information, can serve to reliably classify uncertain variants when other data are insufficient.

A survey of the clinicopathological and molecular characteristics of patients with suspected Lynch syndrome in Latin America

BACKGROUND

Genetic counselling and testing for Lynch syndrome (LS) have recently been introduced in several Latin America countries. We aimed to characterize the clinical, molecular and mismatch repair (MMR) variants spectrum of patients with suspected LS in Latin America.

METHODS

Eleven LS hereditary cancer registries and 34 published LS databases were used to identify unrelated families that fulfilled the Amsterdam II (AMSII) criteria and/or the Bethesda guidelines or suggestive of a dominant colorectal (CRC) inheritance syndrome.

RESULTS

We performed a thorough investigation of 15 countries and identified 6 countries where germline genetic testing for LS is available and 3 countries where tumor testing is used in the LS diagnosis. The spectrum of pathogenic MMR variants included MLH1 up to 54%, MSH2 up to 43%, MSH6 up to 10%, PMS2 up to 3% and EPCAM up to 0.8%. The Latin America MMR spectrum is broad with a total of 220 different variants which 80% were private and 20% were recurrent. Frequent regions included exons 11 of MLH1 (15%), exon 3 and 7 of MSH2 (17 and 15%, respectively), exon 4 of MSH6 (65%), exons 11 and 13 of PMS2 (31% and 23%, respectively). Sixteen international founder variants in MLH1, MSH2 and MSH6 were identified and 41 (19%) variants have not previously been reported, thus representing novel genetic variants in the MMR genes. The AMSII criteria was the most used clinical criteria to identify pathogenic MMR carriers although microsatellite instability, immunohistochemistry and family history are still the primary methods in several countries where no genetic testing for LS is available yet.

CONCLUSION

The Latin America LS pathogenic MMR variants spectrum included new variants, frequently altered genetic regions and potential founder effects, emphasizing the relevance implementing Lynch syndrome genetic testing and counseling in all of Latin America countries.

Locally advanced rectal cancer: Preliminary results of rectal preservation after neoadjuvant chemoradiotherapy

INTRODUCTION

The standard treatment for locally advanced rectal cancer is total mesorectal excision. However, organ preservation has been proposed for tumors with good response to neoadjuvant treatment. The aim of this study was to evaluate the oncologic results of this strategy.

METHODS

This is a retrospective cohort study (2005-2014) including a consecutive series of patients with rectal adenocarcinoma with complete or almost complete clinical response after preoperative chemo-radiotherapy, that were treated according to a strategy of preservation of the rectum.

RESULTS

A total of 204 patients with rectal cancer received neoadjuvant therapy. Thirty (14.7%) had a good response and were treated with rectal preservation (23 «Watch and Wait» and 7 local resections). Median follow-up was 46 months (interquartile range: 30-68). In the group of «Watch & Wait», 4 patients had local recurrence before 12 months (actuarial local recurrence rate=18.5%). All of them underwent salvage surgery (2 with radical surgery and 2 local resections) without any further recurrence. Disease-free survival actuarial rate at 3 years follow-up was 94.1% (95% CI 82.9-100). None of the 7 patients that were treated by local excision had local recurrence. The organ preservation rate for the whole group was 93%.

CONCLUSION

The strategy of organ preservation in locally advanced rectal cancer is feasible in cases with good response to neoadjuvant therapy. When implemented in a highly selected group of patients this strategy is associated with satisfactory oncologic results.

The prevalence of MADH4 and BMPR1A mutations in juvenile polyposis and absence of BMPR2, BMPR1B, and ACVR1 mutations

BACKGROUND

Juvenile polyposis (JP) is an autosomal dominant syndrome predisposing to colorectal and gastric cancer. We have identified mutations in two genes causing JP, MADH4 and bone morphogenetic protein receptor 1A (BMPR1A): both are involved in bone morphogenetic protein (BMP) mediated signalling and are members of the TGF-beta superfamily. This study determined the prevalence of mutations in MADH4 and BMPR1A, as well as three other BMP/activin pathway candidate genes in a large number of JP patients.

METHODS

DNA was extracted from the blood of JP patients and used for PCR amplification of each exon of these five genes, using primers flanking each intron-exon boundary. Mutations were determined by comparison to wild type sequences using sequence analysis software. A total of 77 JP cases were sequenced for mutations in the MADH4, BMPR1A, BMPR1B, BMPR2, and/or ACVR1 (activin A receptor) genes. The latter three genes were analysed when MADH4 and BMPR1A sequencing found no mutations.

RESULTS

Germline MADH4 mutations were found in 14 cases (18.2%) and BMPR1A mutations in 16 cases (20.8%). No mutations were found in BMPR1B, BMPR2, or ACVR1 in 32 MADH4 and BMPR1A mutation negative cases.

DISCUSSION

In the largest series of JP patients reported to date, the prevalence of germline MADH4 and BMPR1A mutations is approximately 20% for each gene. Since mutations were not found in more than half the JP patients, either additional genes predisposing to JP remain to be discovered, or alternate means of inactivation of the two known genes are responsible for these JP cases.

Rectal cancer: local recurrence after surgery without radiotherapy

PURPOSE

This study was designed to assess the local recurrence rate and prognostic factors for local recurrence in patients undergoing curative anterior or abdominoperineal resections without radiotherapy.

METHODS

From January 1980 to December 1996, 514 consecutive patients underwent curative resections for rectal cancer. We excluded those with preoperative radiotherapy (n = 23), postoperative radiotherapy (n = 27), local resection (n = 36), and 11 (2.1 percent) patients who died postoperatively. The remaining 417 patients (249 males) with a median age of 64 (range, 21-90) years were analyzed. For upper third lesions, mesorectal tissue was excised down to at least 5 cm below the tumor. Total mesorectal excision was performed for lower and middle tumors. Postoperative chemotherapy was limited to patients with Stage III lesions. Median follow-up (and 95 percent confidence interval) was (5.2 4.3-5.9) years, with 87.7 percent of patients followed up longer than 24 months. Local recurrence was defined as any recurrence within the field of resection, regardless of the presence or absence of distant metastasis.

RESULTS

Five-year local recurrence rate(and 95 percent confidence interval) was 9.7 (6.4-13) percent, with a median time to diagnosis of 15 (10-23) months. Local recurrence rates in Stages I, II, and III were: 3.1, 4.1, and 24.1 percent, respectively (P < 0.0001). In relation to node status, local recurrence rates were N0, 4.1 (1.7-6.5) percent; N1, 12.6 (4.6-20.6) percent; N2, 32.1 (12.1-52.1) percent; and N3, 59.3 (22.5-96.1) percent; (P < 0.00001). Lower third tumors had a higher local recurrence rate than middle and upper third tumors: 17.9, 7.1, and 5.1 percent, respectively (P = 0.002). Adjusted by stage, this difference was maintained only in Stage III tumors. Among lower tumors, those at 6 and 7 cm from the anal verge had a lower local recurrence rate than those below 6 cm (6.7 vs. 26.2 percent, respectively; P = 0.02). Accidental rectal perforation at or near the tumor site occurred in 12 cases (2.9 percent), showing a strong correlation with local recurrence (P < 0.0001). Multivariate analysis showed significant higher risk for lower third tumors (hazard ratio, 2.98) and positive nodes (hazard ratio, 4.78).

CONCLUSIONS

Appropriate surgery without irradiation achieves excellent local control in N0 rectal cancers. Node metastasis, lower third localization (especially below 6 cm), and accidental rectal perforation at or near the tumor site are significantly associated with a higher local recurrence rate.

Removal of necrotic tissue with an ananain-based enzyme-debriding preparation

An enzymatic debriding preparation was formulated with purified enzyme derived from a crude pineapple stem extract. The primary component of this preparation was the sulfhydryl protease ananain which represented >/=85% of the proteolytic activity. The remaining proteolytic activity in the preparation was contributed by a co-purifying homologous cysteine protease comosain. Taken together these two proteases provided a protein purity of greater than 95% as judged by sodium dodecyl sulfate polyacrylamide gel electrophoresis. This ananain-based enzyme preparation exhibited both gelatinolytic and fibrinolytic activity in vitro. Ananain-based enzyme preparation was formulated in a hydrophilic cream vehicle at concentrations ranging from 115 to 260 U/gm vehicle. Ananain-based enzyme preparation formulated in this fashion is referred to as Vianain debriding agent. Vianain was applied to partial-thickness cutaneous burn wounds produced in the skin of domestic pigs. A maximum of two 4-hour applications of Vianain provided complete debridement of eschar from the partial-thickness burn wounds as judged by light and electron microscopic analyses of biopsy specimens harvested before and after debridement. Wounds debrided with Vianain exhibited more rapid reepithelialization as compared with wounds that were not debrided. Wounds on pigs that were hyperimmunized to ananain-based enzyme preparation before burning and debridement with Vianain exhibited a similar enhancement in reepithelialization as compared with wounds treated with vehicle alone. The capacity of Vianain to debride necrotic tissue was also evaluated in a guinea pig ischemic ulcer model. Full-thickness ischemic lesions were created on the back of guinea pigs. Vianain was applied to the hardened necrotic tissue for 6 hours per day for up to a maximum of 5 days. Complete debridement of these wounds was accomplished within 4 to 5 days. Treatment of ischemic cutaneous ulcerations in this animal model with two commercially available enzyme-debriding agents provided little or no debridement of the necrotic tissue. In vitro, Vianain treatment of surgically debrided human tissue samples, obtained from patients with burn injury or cutaneous ulcers, showed that the protease preparation was effective in rapidly digesting these necrotic tissues.

Electrodiagnostic evaluation of fecal incontinence

The aim of this study was to assess the utility of electrodiagnostic testing (EDT) for the evaluation of fecal incontinence (FI). Over a 5-year period, 225 patients (174 females) with FI were prospectively studied with anal manometry, anal ultrasonography, anal electromyography (AEMG), and pudendal nerve terminal motor latency (PNTML) assessment. The mean age was 60 (range 12-94) years. Causes of FI identified by clinical evaluation were obstetric injuries (45), rectal prolapse (43), iatrogenic or other trauma (42), neurologic disease (23), and idiopathic (72). EDT revealed abnormalities in 76% of patients. The incidence of pudendal neuropathy (PN) was 36% (bilateral 21%, unilateral 15%). Patients with PN were older than were those with normal PNTML (mean 71 vs. 63 years; P < 0.002). No relationship between squeeze pressure and PN could be demonstrated (P = 0.9). Reduced motor unit potential (MUP) recruitment on AEMG was present in 60% and was associated with decreased squeeze pressure (P < 0.001) and increased MUP polyphasia (P < 0.001). Concurrence of AEMG and anal ultrasonographic findings was observed in 35 of 41 patients (84%). Defects were overlooked in one study but identified by the other on three occasions, each. Moreover, 8 of 22 patients with demonstrated sphincter defects had unsuspected PN or extensive sphincter injury on AEMG that precluded sphincter repair. In conclusion, EDT proved to be a valuable tool in the evaluation and subsequent treatment of patients with FI.

Pudendal neuropathy is not related to physiologic pelvic outlet obstruction

Chronic straining because of pelvic outlet obstruction is hypothesized to cause pudendal neuropathy (PN) by stretch injury.

PURPOSE

The aim of this study was to determine any association between PN and pelvic outlet obstruction.

METHODS

One hundred forty-seven constipated patients were evaluated by cinedefecography and pudendal nerve terminal motor latency assessment. PN was defined as a latency longer than 2.2 ms. Pelvic outlet obstructive patterns of evacuation included paradoxic contraction, nonrelaxation of the puborectalis muscle, or failure of opening of the anal canal.

RESULTS

Median length of constipation including straining during evacuation was eight (range, 1-47) years. Ninety-one (62 percent) subjects had a normal pattern of evacuation, and 56 (38 percent) had an obstructed pattern. Both groups had a similar median age (68 vs. 69 years, respectively; P > 0.05) and same median length of symptoms. Overall incidence of PN was 23.8 percent (10.9 percent unilateral and 12.9 percent bilateral). There was no difference in the incidence of PN between patients with normal evacuation and patients with obstructed evacuation (24.2 percent vs. 23.2 percent, respectively; P > 0.05). Patients with PN had a similar incidence of physiologic pelvic outlet obstruction as did patients without PN. However, median age of patients with PN was higher than those without PN (73 vs. 66 years, respectively; P > 0.05).

CONCLUSION

There was a difference in the incidence of PN between normal and obstructed patterns of evacuation. Therefore, the espoused theory that obstructed defecation causes PN appears flawed.

Pudendal neuropathy in evacuatory disorders

PURPOSE

Aims of the present study were to assess frequency of pudendal neuropathy in patients with constipation and fecal incontinence, to determine its correlation with clinical variables, anal electromyographic assessment, and anal manometric pressures, and to determine usefulness of the pudendal nerve terminal motor latency assessment in evaluation of these evacuatory disorders.

METHODS

From 1988 to 1993, 395 patients (constipated, 172; incontinent, 223) underwent pudendal nerve terminal motor latency, electromyography, and anal manometry. Pudendal neuropathy was defined as a pudendal nerve terminal motor latency greater than 2.2 ms.

RESULTS

Patients were a mean age of 60.7 (range, 17-88) years. Overall incidence of pudendal neuropathy was 31.4 percent (constipated, 23.8 percent; incontinent, 37.2 percent; P < 0.05). Incidence of pudendal neuropathy dramatically increased after 70 years of age in both groups (22 percent vs. 44 percent; P < 0.05). Moreover, subjects with pudendal neuropathy were older than those without pudendal neuropathy (mean age, 67 vs. 57 years; P < 0.05). The presence of pudendal neuropathy was associated with decreased motor unit potentials recruitment in patients with incontinence (P < 0.01). Patients with and without pudendal neuropathy had a similar mean squeezing pressure in both groups.

CONCLUSION

Pudendal neuropathy is an age-related phenomenon. Although pudendal neuropathy is associated with abnormal anal electromyographic findings in patients with incontinence, no association with anal manometric pressures was found. Pudendal nerve terminal motor latency assessment is a useful tool in the evaluation of patients with fecal incontinence, but its role in the assessment of constipated patients remains unknown.

Role of pudendal nerve terminal motor latency assessment in constipated patients

The importance of pudendal nerve terminal motor latency assessment for the evaluation of incontinence is well established. However, its role in constipated patients remains unclear.

PURPOSE

The purpose of the present study was to assess the incidence of pudendal neuropathy in constipated patients and its correlation with others variables including age, sex, anal pressures, and anal electromyography.

RESULTS

From 1988 to 1993, 161 patients with chronic constipation underwent pudendal nerve terminal motor latency assessment, anal electromyography, and anal manometry. The overall incidence of pudendal neuropathy was 23.6 percent; females and males had a similar incidence (24 percent vs. 23 percent, respectively; P > 0.05). Patients over 70 years old had a significantly higher incidence of pudendal neuropathy than did patients under 70 years (37 percent vs. 12 percent, respectively; P < 0.01). Patients with paradoxical puborectalis contraction on anal electromyographic assessment had a higher incidence of bilateral neuropathy, paradoxical puborectalis contraction (+)23 percent vs. paradoxical puborectalis contraction (-)8 percent, P < 0.05. Patients with pudendal neuropathy also had a higher incidence of decreased motor units potential recruitment than did patients without pudendal neuropathy (31.5 percent vs. 17 percent, respectively; P > 0.05).

CONCLUSIONS

Pudendal nerve terminal motor latency assessment was able to detect unsuspected pudendal neuropathy in 24 percent of patients. This finding correlated with age and with the presence of paradoxical puborectalis contraction but not with manometric anal pressures, motor unit potentials recruitment, or the presence of polyphasia. However, the often espoused relationship between pudendal latency and external sphincter function could not be demonstrated.

Human pulmonary alveolar type 2 cells contain an apical membrane glycoprotein common to malignant cells

A monoclonal antibody, Ca1, raised against a detergent extract of Hep 2 cells derived from a human laryngeal carcinoma, was shown in these studies to bind to the apical surface of normal alveolar type 2 cells but not type 1 cells in the human lung. In lung specimens from patients with alveolitis, the antibody also bound to hyperplastic type 2 cells and to transition cells which were in the process of becoming alveolar type 1 cells. Ca1 binds to the apical plasma membrane and to internal membranes of cytoplasmic vesicles thought to be involved in the packaging of pulmonary surfactant. A surfactant-enriched fraction of human lung lavage did not bind the Ca1 antibody suggesting that the antigen was not an integral component of secreted surfactant. In normal human lung parenchyma, Ca1 binds only to type 2 cells, however it also binds to the apical surface of Clara cells in areas of cellular hyperplasia. Solubilized homogenates of whole lung, of a cell membrane fraction and of Hep 2 cells, immunoprecipitated with Ca2, separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and probed with iodinated lectins, revealed that terminal glycosylation of the type 2 cell antigen differed from that of Hep 2 cells. Ca1 and a 330 kilodalton type 2 cell glycoprotein bind the lectin Maclura pomifera agglutinin. These two glycoproteins represent the first defined membrane markers of the apical surface of the human type 2 cell.

The binding of cationic probes to apical and basal surfaces of rat lung capillary endothelium and of endothelial cells in tissue culture

The reasons for greater lung vascular permeability to anionic macromolecules are not understood. In order to determine whether the luminal or abluminal surfaces of lung capillary endothelial cells differ with respect to surface charge, we compared the binding of cationic ferritin, an electron dense probe, with these cell surfaces in lung capillaries. Because lung capillaries are not normally permeable to cationic ferritin, lungs were examined from rats with increased permeability edema caused by pretreatment with alpha-naphthylthiourea (ANTU). We found that more cationic ferritin particles bound to the luminal than to the abluminal surfaces of lung capillary endothelium. In order to determine whether this was due to inaccessibility of cationic ferritin to the lung interstitium, we also compared cationic ferritin binding to the apical and basal surfaces of bovine calf aortic and main pulmonary arterial endothelial cells in tissue culture. We found that more cationic ferritin bound to the apical than to the basal surface of the cultured cells. The binding of cationic ferritin to cultured endothelial cells was due to charge since native, anionic ferritin did not bind to either surface and binding was decreased by neuraminidase pretreatment of cultures. Cultures incubated with thiourea, another thiocarbamide that causes increased permeability edema in vivo, also showed greater binding of cationic ferritin to the apical cell surface, suggesting that the differences seen in vivo were not due to thiocarbamide injury. However, another cationic probe, ruthenium red, bound to both the apical and basal surfaces of cultured endothelial cells. These results suggest that the basal endothelial cell surface does not lack anionic sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural immunolocalization of lysyl oxidase in vascular connective tissue

The localization of lysyl oxidase was examined in calf and rat aortic connective tissue at the ultrastructural level using polyclonal chicken anti-lysyl oxidase and gold conjugated rabbit anti-chicken immunoglobulin G to identify immunoreactive sites. Electron microscopy of calf aortic specimens revealed discrete gold deposits at the interface between extracellular bundles of amorphous elastin and the microfibrils circumferentially surrounding these bundles. The antibody did not react with microfibrils which were distant from the interface with elastin. There was negligible deposition of gold within the bundles of amorphous elastin and those few deposits seen at these sites appeared to be associated with strands of microfibrils. Lysyl oxidase was similarly localized in newborn rat aorta at the interface between microfibrils and nascent elastin fibers. Gold deposits were not seen in association with extracellular collagen fibers even after collagen-associated proteoglycans had been degraded by chondroitinase ABC. However, the antibody did recognize collagen-bound lysyl oxidase in collagen fibers prepared from purified collagen to which the enzyme had been added in vitro. No reaction product was seen if the anti-lysyl oxidase was preadsorbed with purified lysyl oxidase illustrating the specificity of the antibody probe. The present results are consistent with a model of elastogenesis predicting the radial growth of the elastin fiber by the deposition and crosslinking of tropoelastin units at the fiber-microfibril interface.

Alveolar wall basement membranes in bleomycin-induced pulmonary fibrosis

The ultrastructural characteristics of alveolar wall basement membranes (BM) were defined in an experimental model of pulmonary fibrosis. Lungs of adult hamsters were examined 2 to 60 days after a single intratracheal instillation of 0.5 units of bleomycin sulfate. Sections of lung fixed with tannic acid and glutaraldehyde were analyzed for epithelial basement membrane (EPI-BM) thickness and duplication, and tissue incubated in ruthenium red prior to fixation was evaluated for distribution of EPI-BM anionic sites. There were no major alterations in capillary EPI-BM. Six days after bleomycin, during acute inflammation, there was focal injury to alveolar epithelial cells and resultant denudation of EPI-BM. Denuded EPI-BM was folded with the lamina densa 60% thicker than in control animals, suggesting its active or passive retraction. Despite type 2 cell hyperplasia and repopulation of the epithelium, there was no duplication of EPI-BM. Thirty and 60 days after bleomycin, the epithelium was intact, inflammation had subsided, and widespread but focal fibrosis was present. This stage was characterized by thickening and duplication of the EPI-BM; 10% of EPI-BM on the thin side of the alveolar wall were duplicated at 30 days and 30% at 60 days. Duplication and thickening, although worse in fibrotic areas, also occurred in normal-appearing areas of lung, showing that EPI-BM changes may be the only residuum of previous damage. Duplication of EPI-BM in this model of pulmonary fibrosis is a late rather than an early feature of disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of a rat lung fraction enriched in alveolar wall basement membranes

Separation of lung alveolar basement membranes from interstitial connective tissue protein has proved difficult, and a pure preparation of alveolar wall basement membranes (AWBM) is not available. We have modified a technique employing the detergent Triton X-100 for isolating AWBM from rat lungs by adding a step utilizing human skin collagenase (HSC), a highly purified enzyme obtained from skin fibroblasts that specifically cleaves non-basement membrane collagens. Triton extraction of both lungs yields 15-20 mg of basement membrane-enriched material referred to as crude fraction (CF). Ultrastructural studies show that CF includes both epithelial and endothelial basement membranes that appear similar to their in vivo counterparts and contain heparan sulfate proteoglycans. Extraction of type IV collagen is documented by the appearance of highly glycosylated hydroxylysine. This CF contains minimal amounts of contaminating elastin but significant amounts of interstitial collagens. CF was further purified for biochemical studies by incubation with HSC. HSC solubilized 20% of CF hydroxyproline resulting in a final fraction highly enriched in AWBM. Lung minces incubated in tritiated lysine produced a CF extract rich in newly formed type IV collagen, showing that lung tissue synthesizes AWBM collagen in vitro.

Binding of charged ferritin to alveolar wall components and charge selectivity of macromolecular transport in permeability pulmonary edema in rats

Rat lungs were inflated and incubated in either anionic or cationic ferritin, and alveolar and capillary basement membranes were examined by electron microscopy. Cationic ferritin bound to heparan sulfate proteoglycans on the external surface of the alveolar basement membrane, whereas cationic ferritin bound to the lamina densa of the capillary basement membranes. Anionic and cationic ferritin was also perfused through the pulmonary circulation of lungs isolated from control rats and rats previously injected with alpha-naphthylthiourea, which produces permeability pulmonary edema. Neither anionic nor cationic ferritin leaked from the pulmonary capillaries in perfused controls; cationic, but not anionic, ferritin adhered to endothelial cell surfaces. In lungs with alpha-naphthylthiourea pulmonary edema, perfused for 2-15 minutes, anionic ferritin leaked from pulmonary capillaries into the alveolar interstitium and alveolar space, while cationic ferritin remained within the capillary lumen. Five times as much anionic ferritin appeared in the capillary basement membranes on the thick side of the alveolar wall, as in the alveolar basement membranes on the thin side of the alveolar wall. In alpha-naphthylthiourea lungs perfused for 45-60 minutes, cationic ferritin also leaked through the injured endothelium and bound twice as much to the alveolar as the capillary basement membranes. The negatively charged pulmonary capillary endothelium, the positively charged capillary basement membranes, and the negatively charged alveolar basement membranes may influence the transport of macromolecules from the pulmonary circulation in permeability pulmonary edema.

Alterations in alveolar basement membranes during postnatal lung growth

We studied the ultrastructural characteristics of alveolar basement membranes (ABM) and capillary basement membranes (CBM) in rat lungs at birth, at 8-10 d of age, during alveolar formation, and at 6-10 wk of age, after most alveoli have formed. We also measured in vitro lung proteoglycan and heparan sulfate synthesis at each age. We noted three major age-related changes in pulmonary basement membranes. (a) Discontinuities in the ABM through which basilar cytoplasmic foot processes extend are present beneath alveolar type-2 cells but not alveolar type-1 cells. These discontinuities are most prevalent at birth but also exist in the adult. (b) Discontinuities are also present in CBM at the two earliest time points but are maximal at 8 d of age rather than at birth. Fusions between ABM and CBM are often absent at 8 d of age, but CBM and CBM/ABM fusions were complete in the adult. (c) Heparan sulfate proteoglycans identified with ruthenium red and selective enzyme degradation are distributed equally on epithelial and interstitial sides of the ABM lamina densa at birth, but decrease on the interstitial side with age. In vitro proteoglycan and heparan sulfate accumulation at birth was two times that at 8 d and five times that in the adult. Discontinuities in ABM allow epithelial-mesenchymal interactions that may influence type-2 cells cytodifferentiation. Discontinuities in CBM suggest that capillary proliferation and neovascularization are associated with alveolar formation at 8 d. When CBM becomes complete and forms junctions with ABM, lung neovascularization likely ends as does the ability to form new alveoli.

Structural features of alveolar wall basement membrane in the adult rat lung

The ultrastructural characteristics of alveolar (ABM) and capillary (CBM) basement membranes in the adult rat lung have been defined using tannic acid fixation, ruthenium red staining, or incubation in guanidine HCl. ABM is dense and amorphous, has 3- to 5-nm filaments in the lamina rara externa (facing the alveolus) that run between the lamina densa and the basal cell surface of the epithelium, has an orderly array of ruthenium red-positive anionic sites that appear predominantly (79%) on the lamina rara externa, and has discontinuities beneath alveolar type II cells but not type I cells that allow penetration of type II cytoplasmic processes into the interstitium of the alveolar wall. The CBM is fibrillar and less compact than ABM, has no lamina rara filaments, and has one fifth the number of ruthenium red-positive anionic sites of ABM that appear predominantly (64%) overlying the lamina densa. Incubation of lung tissue with Flavobacterium heparinum enzyme or with chondroitinase has shown that ABM anionic sites represent heparan sulfate proteoglycans, whereas CBM anionic sites contain this and other sulfated proteoglycans. The CBM fuses in a local fashion with ABM, compartmentalizing the alveolar wall into a thick and thin side and establishing a thin, single, basement-membrane gas-exchange surface between alveolar air, and capillary blood. The potential implications of ABM and CBM ultrastructure for permeability, cell differentiation, and repair and morphogenesis of the lung are discussed.

Ultrastructural localization and characterization of proteoglycans in the pulmonary alveolus

The ultrastructural identification and characterization of lung proteoglycans was studied using the polycationic dye, ruthenium red. Treating lung parenchyma with the detergent Triton X-100 increased epithelial permeability and allowed the dye to penetrate alveolar walls and stain the alveolar basement membrane and lung collagen. Ruthenium red stained numerous 10- to 40-nm granules concentrated at the lamina surface of basement membrane and attached to the major doublet collagen band. The granules attached to collagen were digested by chondroitinase ABC and papain, indicating that they represent proteoglycan aggregates containing chondroitin or dermatan sulfate. Granules observed on the alveolar basement membrane were resistant to digestion by collagenase and by all glycosidases, suggesting that heparin or heparan sulfate is the predominant glycosaminoglycan in epithelial basement membrane. Ruthenium red in association with tannic acid also stained a fine network of 3- to 10-nm filaments in which collagen was enmeshed, forming the interfibrillar matrix. This network was resistant to collagenase and glycosidase digestion but was removed after papain digestion, suggesting that it was a protein or glycoprotein that did not contain glycosaminoglycans. These methods have allowed visualization of lung proteoglycans and have identified a structure that does not contain glycosaminoglycan that is intimately associated with collagen. This technique can now be applied to explore the potential role of proteoglycans in lung development and in restructuring the lung in various disease states.