A retrospective study of people with familial hypercholesterolaemia in a Belgian lipid clinic.

BACKGROUND: Familial hypercholesterolaemia (FH) is a genetic disease characterised by hypercholesterolaemia and premature cardiovascular events. Early diagnosis and treatment can reduce the cardiovascular burden. We describe the characteristics of patients with heterozygous FH followed in a tertiary hospital in Belgium. METHODS: We retrospectively studied a population of 321 patients with definite heterozygous FH who visited the UZ Leuven lipid clinic at least once between 1 January 2016 and 31 December 2020. Data are represented as mean ± SD. RESULTS: The age at time of diagnosis of FH was 39 ± 18 years. Patients with atherosclerotic disease (secondary prevention) were older (p < .001), more often male (p < .001), had a higher body mass index (p < .001), prevalence of (pre)diabetes (p < .001) and hypertension (p < .001) and had lower levels of low-density lipoprotein-cholesterol (LDL-C) (p < .001) than individuals without atherosclerotic disease (primary prevention). The average LDL-C in both primary (109 ± 53 mg/dL) and secondary (81 ± 63 mg/dL) prevention did not meet the targets of LDL-C as proposed by the 2019 ESC/EAS guidelines for the management of dyslipidaemias. However, LDL-C levels in the subgroup of patients treated with PCSK9 inhibition therapy, and especially in the triple therapy group (combination of statin, ezetimibe and PCSK9 inhibitor), were markedly lower (p < .001). CONCLUSIONS: In this Belgian population, people with heterozygous FH remain undertreated. Reaching treatment targets in FH seems possible, although this requires combination treatment (with PCSK9-targeted therapy) in most patients. Earlier diagnosis of FH, more extensive lipid-lowering treatment and reimbursement options and a more holistic approach are needed to lower LDL-C and cardiovascular risk in patients with FH.

Effect of obesity on gastrointestinal transit, pressure and pH using a wireless motility capsule.

BACKGROUND: Despite the increasing prevalence and medical burden of obesity, the understanding of gastrointestinal physiology in obesity is scarce, which hampers drug development. AIM: To investigate the effect of obesity and food intake on gastrointestinal transit, pressure and pH. MATERIAL AND METHODS: An exploratory cross-sectional study using a wireless motility capsule (SmartPill©) was performed in 11 participants with obesity and 11 age- and gender-matched participants with normal weight (group) in fasted and fed state (visit). During the first visit, the capsule was ingested after an overnight fast. During a second visit, the capsule was ingested after a nutritional drink to simulate fed state. Linear mixed models were constructed to compare segmental gastrointestinal transit, pressure and pH between groups (obesity or control) and within every group (fasted or fed). RESULTS: Food intake slowed gastric emptying in both groups (both P < 0.0001), though food-induced gastric contractility was higher in participants with obesity compared to controls (P = 0.02). In the small intestine, a higher contractility (P = 0.001), shorter transit (P = 0.04) and lower median pH (P = 0.002) was observed in participants with obesity compared to controls. No differences were observed for colonic measurements. CONCLUSION: Obesity has a profound impact on gastrointestinal physiology, which should be taken into account for drug development.

Changes in bone macro- and microstructure in diabetic obese mice revealed by high resolution microfocus X-ray computed tomography.

High resolution microfocus X-ray computed tomography (HR-microCT) was employed to characterize the structural alterations of the cortical and trabecular bone in a mouse model of obesity-driven type 2 diabetes (T2DM). C57Bl/6J mice were randomly assigned for 14 weeks to either a control diet-fed (CTRL) or a high fat diet (HFD)-fed group developing obesity, hyperglycaemia and insulin resistance. The HFD group showed an increased trabecular thickness and a decreased trabecular number compared to CTRL animals. Midshaft tibia intracortical porosity was assessed at two spatial image resolutions. At 2 µm scale, no change was observed in the intracortical structure. At 1 µm scale, a decrease in the cortical vascular porosity of the HFD bone was evidenced. The study of a group of 8 week old animals corresponding to animals at the start of the diet challenge revealed that the decreased vascular porosity was T2DM-dependant and not related to the ageing process. Our results offer an unprecedented ultra-characterization of the T2DM compromised skeletal micro-architecture and highlight an unrevealed T2DM-related decrease in the cortical vascular porosity, potentially affecting the bone health and fragility. Additionally, it provides some insights into the technical challenge facing the assessment of the rodent bone structure using HR-microCT imaging.

Higher plasma motilin levels in obese patients decrease after Roux-en-Y gastric bypass surgery and regulate hunger.

OBJECTIVE: Motilin-induced phase III contractions of the migrating motor complex (MMC) signal hunger in healthy volunteers. The current aim was to study the role of motilin as a hunger-inducing factor in obese patients and to evaluate the effect of Roux-en-Y gastric bypass (RYGB) surgery on plasma motilin levels and hunger scores. DESIGN: Motilin and ghrelin plasma levels were determined during a complete MMC cycle in controls and obese patients selected for RYGB before, 6 months and 1 year after surgery. 20 min after the end of the second phase III, obese patients received an intravenous infusion of 40 mg erythromycin. Hunger was scored every 5 min. Hedonic hunger was assessed in obese patients with the Power of Food Scale questionnaire. RESULTS: Obesity caused a switch in the origin of phase III from antrum to duodenum. Obese patients had significantly higher motilin levels compared with controls during the MMC but tended to lack the motilin peak prior to phase III necessary to trigger hunger. Hunger scores during phase III were significantly lower in obese patients, but could be restored to control levels through the administration of a low dose of the motilin agonist, erythromycin. After RYGB surgery motilin, but not ghrelin, levels decreased in parallel with hedonic hunger scores. CONCLUSIONS: Motilin may be an important regulator involved in the pathogenesis of obesity.

Low cytochrome oxidase 4I1 links mitochondrial dysfunction to obesity and type 2 diabetes in humans and mice.

OBJECTIVES: Cytochrome oxidase (COX) dysfunction is associated with mitochondrial oxidative stress. We determined the association between COX expression, obesity and type 2 diabetes. SUBJECTS/METHODS: COX4I1 and COX10 genes were measured in monocytes of 24 lean controls, 31 glucose-tolerant and 67 diabetic obese patients, and 17 morbidly obese patients before and after bariatric surgery. We investigated the effect of caloric restriction and peroxisome proliferator-activated receptor (PPAR) agonist treatment on Cox in obese diabetic mice, and that of diet-induced insulin resistance in Streptozotocin-treated mice. RESULTS: Low COX4I1 was associated with type 2 diabetes in obese patients, adjusting for age, gender, smoking, interleukin-6 and high-sensitivity C-reactive protein, all related to metabolic syndrome (MetS; odds ratio: 6.1, 95% confidence interval: 2.3-16). In contrast, COX10 was low in glucose-tolerant and diabetic obese patients. In morbidly obese patients, COX4I1 was lower in visceral adipose tissue collected at bariatric surgery. In their monocytes, COX4I1 decreased after bariatric surgery, and low COX4I1 at 4 months was associated with MetS at 7 years. In leptin-deficient obese diabetic mice, Cox4i1 was low in white visceral adipose tissue (n=13; P<0.001) compared with age-matched lean mice (n=10). PPARγ-agonist treatment (n=13), but not caloric restriction (n=11), increased Cox4i1 (P<0.001). Increase in Cox4i1 depended on the increase in glucose transporter 4 (Glut4) expression and insulin sensitivity, independent of the increase in blood adiponectin. In streptozotocin-treated mice (three groups of seven mice, diet-induced insulin resistance decreased Cox4i1 and Glut4 (P<0.001 for both). CONCLUSION: COX4I1 depression is related to insulin resistance and type 2 diabetes in obesity. In peripheral blood monocytes, it may be a diagnostically useful biomarker.

BMI is an important driver of ß-cell loss in type 1 diabetes upon diagnosis in 10 to 18-year-old children.

OBJECTIVE: Body weight-related insulin resistance probably plays a role in progression to type 1 diabetes, but has an uncertain impact following diagnosis. In this study, we investigated whether BMI measured at diagnosis was an independent predictor of C-peptide decline 1-year post-diagnosis. DESIGN: Multicentre longitudinal study carried out at diagnosis and up to 1-year follow-up. METHODS: Data on C-peptide were collected from seven diabetes centres in Europe. Patients were grouped according to age at diagnosis (<5 years, n=126; >5 years <10 years, n=295; >10 years <18 years, n=421; >18 years, n=410). Linear regression was used to investigate whether BMI was an independent predictor of change in fasting C-peptide over 1 year. Models were additionally adjusted for baseline insulin dose and HbA1c. RESULTS: In individuals diagnosed between 0 and 5 years, 5 and 10 years and those diagnosed >18 years, we found no association between BMI and C-peptide decline. In patients aged 10-18 years, higher BMI at baseline was associated with a greater decline in fasting C-peptide over 1 year with a decrease (ß 95% CI; P value) of 0.025 (0.010, 0.041) nM/kg per m(2) higher baseline BMI (P=0.001). This association remained significant after adjusting for gender and differences in HbA1c and insulin dose (ß=0.026, 95% CI=0.0097, 0.042; P=0.002). CONCLUSIONS: These observations indicate that increased body weight and increased insulin demand are associated with more rapid disease progression after diagnosis of type 1 diabetes in an age group 10-18 years. This should be considered in studies of ß-cell function in type 1 diabetes.

Age-dependent decline of ß-cell function in type 1 diabetes after diagnosis: a multi-centre longitudinal study.

AIMS: C-peptide secretion is currently the only available clinical biomarker to measure residual ß-cell function in type 1 diabetes. However, the natural history of C-peptide decline after diagnosis can vary considerably dependent upon several variables. We investigated the shape of C-peptide decline over time from type 1 diabetes onset in relation to age at diagnosis, haemoglobin A1c (HbA1c) levels and insulin dose. METHODS: We analysed data from 3929 type 1 diabetes patients recruited from seven European centres representing all age groups at disease onset (childhood, adolescence and adulthood). The influence of the age at onset on ß-cell function was investigated in a longitudinal analysis at diagnosis and up to 5-years follow-up. RESULTS: Fasting C-peptide (FCP) data at diagnosis were available in 3668 patients stratified according to age at diagnosis in four groups (<5 years, n = 344; >5 years < 10 years, n = 668; >10 years < 18 years, n = 991; >18 years, n = 1655). FCP levels were positively correlated with age (p < 0.001); the subsequent decline in FCP over time was log-linear with a greater decline rate in younger age groups (p < 0.0001). CONCLUSIONS: This study reveals a positive correlation between age at diagnosis of type 1 diabetes and FCP with a more rapid decline of ß-cell function in the very young patients. These data can inform the design of clinical trials using C-peptide values as an end-point for the effect of a given treatment.

Prevalence of persistent lipid abnormalities in statin-treated patients: Belgian results of the Dyslipidaemia International Study (DYSIS).

AIM: A substantial number of cardiovascular events are not prevented by statin therapy, which is still regarded as the first-line therapy for hyperlipidaemia. Insights into the prevalence of lipid abnormalities of statin-treated patients in Belgium are lacking and may shed light on an unmet medical need for optimal use of current lipid-lowering therapies. This study aims to assess the prevalence and types of persistent lipid abnormalities in patients receiving statin therapy in a real-life primary care setting in Belgium. METHODS: This cross-sectional cohort study was designed to estimate the prevalence of specific lipid abnormalities in statin-treated patients in Belgium. Total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides were recorded from the patients' medical record. Patient's total cardiovascular risk and corresponding lipid treatment goals were defined based on the recent European Society of Cardiology/European Atherosclerosis Society recommendations. RESULTS: Overall, 56.2% of the statin-treated patients were not at goal for LDL-C. Low HDL-C (< 40 mg dl(-1) in men, < 45 mg dl(-1) in women) and elevated triglycerides (> 150 mg dl(-1) ) were seen in 16.3% and 29.0% of patients, respectively. Very high-risk patients were more likely to have LDL-C not at goal (71.4% of them), while 60.0% of high-risk patients and 34.1% of moderate-risk patients were not at goal for LDL-C. Use of ezetimibe (10 mg) was strongly associated with meeting LDL-C goals (OR 16.9, p < 0.0001). CONCLUSION: In Belgium, lipid abnormalities remained highly prevalent despite statin treatment, with more than half of all patients not reaching their LDL-C treatment goal. This finding clearly indicates that more aggressive lipid-lowering treatment is required in clinical daily practice to achieve the goals of the current guidelines.

Gastric bypass surgery, but not caloric restriction, decreases dipeptidyl peptidase-4 activity in obese patients with type 2 diabetes.

The mechanism by which incretins and their effect on insulin secretion increase markedly following gastric bypass (GBP) surgery is not fully elucidated. We hypothesized that a decrease in the activity of dipeptidyl peptidase-4 (DPP-4), the enzyme which inactivates incretins, may explain the rise in incretin levels post-GBP. Fasting plasma DPP-4 activity was measured after 10-kg equivalent weight loss by GBP (n = 16) or by caloric restriction (CR,n = 14) in obese patients with type 2 diabetes. DPP-4 activity decreased after GBP by 11.6% (p = 0.01), but not after CR. The increased peak glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) response to oral glucose after GBP did not correlate with DPP-4 activity. The decrease in fasting plasma DPP-4 activity after GBP occurred by a mechanism independent of weight loss and did not relate to change in incretin concentrations. Whether the change in DPP-4 activity contributes to improved diabetes control after GBP remains therefore to be determined.

Does the unfavorable pharmacokinetic and pharmacodynamic profile of the iNOS inhibitor GW273629 lead to inefficacy in acute migraine?

The objective of this study was to investigate the pharmacodynamics and pharmacokinetics of a single dose of GW273629, a selective iNOS inhibitor, given during and outside a migraine attack. GW273629 1500 mg was administered to 15 migraine patients both ictally and interictally. Nasal and exhaled nitric oxide (NO), plasma 3-nitrotyrosine, and nitrates were measured to assess systemic NO production. In addition, pharmacokinetics and treatment response were assessed. Data are mean (95% confidence interval [CI]). Plasma 3-nitrotyrosine was higher ictally: 11.96 (8.22, 15.71) ictally versus 2.74 (2.24, 3.24) ng/10 mg interictally (P < .0001). Exhaled and nasal NO showed a similar trend: 12.5 (6.5, 18.6) and 62.2 (41.5, 82.8) ppb ictally versus 9.9 (6.3, 13.4) ppb and 52.5 (38.5, 66.0) ppb interictally, respectively. Early absorption of GW273629 (AUC(0-2) [90% CI]) was reduced by 41 (22, 55)% during an attack. There was no improvement of headache or associated symptoms. Migraine headache is associated with reduced early absorption of GW273629 and excess NO production. In this open-label study, GW273629 was ineffective in the treatment of acute migraine.

Calcitonin gene-related peptide8-37 antagonizes capsaicin-induced vasodilation in the skin: evaluation of a human in vivo pharmacodynamic model.

The purpose of this study was to identify the mediators involved in capsaicin-induced vasodilation in the human skin and to evaluate a pharmacodynamic model for the early clinical evaluation of calcitonin gene-related peptide (CGRP) receptor antagonists. Dermal blood flow (DBF) response of the forearm skin to topically applied capsaicin was measured using laser Doppler perfusion imaging in 22 subjects. The effect of intra-arterially administered CGRP(8-37) (1200 ng . min(-1) . dl(-1) forearm), indomethacin (5 mug . min(-1) . dl(-1) forearm), and N(G)-monomethyl-l-arginine (l-NMMA; 0.2 mg . min(-1) dl(-1) forearm), and orally administered aprepitant (375 mg) on capsaicin-induced dermal vasodilation was assessed. Furthermore, the diurnal variation of the DBF response to capsaicin was studied. CGRP(8-37) inhibited the capsaicin-induced DBF increase: 217(145, 290)% in infused versus 370 (254, 486)% in the noninfused arm [mean (95% CI); p = 0.004]. In contrast, indomethacin, l-NMMA, aprepitant, and the time of assessment did not affect the DBF response to capsaicin. Thus, capsaicin-induced vasodilation in the human forearm skin is largely mediated by CGRP, but not by vasodilating prostaglandins, nitric oxide, or substance P. The response to capsaicin does not display a circadian rhythm. A pharmacodynamic model is proposed to evaluate CGRP receptor antagonists in humans in vivo.

Reproducibility of the capsaicin-induced dermal blood flow response as assessed by laser Doppler perfusion imaging.

AIMS: Part I: to establish the dose and appropriate application site of capsaicin on the human forearm in order to produce a robust and reproducible dermal blood flow (DBF) response. Part II: to evaluate the within-subject arm-to-arm and period-to-period reproducibility. METHODS: Both parts consisted of two study visits. In part I, placebo and 100, 300 and 1000 microg capsaicin were applied at four predefined sites on the volar surface of both forearms. Placebo and capsaicin doses were randomized and balanced by site between subjects. Changes in DBF were assessed by laser Doppler perfusion imaging up to 60 min after capsaicin application. In part II, only 1000 microg capsaicin was applied on the proximal forearm and changes in DBF assessed up to 30 min (t(30)). DBF response was expressed as percent change from baseline +/- SD and the corresponding AUC(0-30). Reproducibility assessment included calculation of the concordance correlation coefficient (CCC). RESULTS: Part I (n = 12 subjects): compared with placebo, 300 and 1000 microg capsaicin increased DBF (P < 0.05) at all time points except at 10 min. This increase was reproducible at the two most proximal sites from the 30-min time point onwards when compared between arms (CCC >or= 0.8, i.e. substantial to almost perfect reproducibility). In part II (n = 11), t(30) averaged 390 +/- 120% and arm-to-arm reproducibility was almost perfect (CCC = 0.91) for AUC(0-30). CONCLUSIONS: Capsaicin induces a reproducible within-subject arm-to-arm increase in DBF. We provide a non-invasive pharmacodynamic model in humans to test antagonists of mediators involved in capsaicin-induced dermal vasodilation, including calcitonin gene-related peptide antagonists.

Cough as the presenting symptom of large vessel vasculitis.

We report the case of a 57-year-old woman presenting with persistent cough, weight loss, and fever. An extensive work-up revealed laboratory signs of inflammation and a mild thickening of the aortic wall on computed tomographic scan of the thorax. These findings raised the suspicion of large vessel vasculitis that was elegantly confirmed by fluorodeoxyglucose positron emission tomography. Persistent cough as the inaugural symptom and involvement of large vessels in Horton's disease are also discussed.

Dynein arms and spokes after ciliogenesis in cultured respiratory epithelial cells from non-PCD individuals.

Dynein arms and spokes are crucial components of cilia. Reference values for the dynein arms and spokes were calculated based on biopsies from non-PCD patients as well as after ciliogenesis in culture. The mean values in the biopsies (n = 251) were 8.4 +/- 0.5, 2.9 +/- 0.7 and 4.7 +/- 1.0 for the outer dynein arms, inner dynein arms and spokes respectively. After ciliogenesis in culture (n = 462) identical values were found: 8.7 +/- 0.4, 3.0 +/- 0.4 and 5.5 +/- 0.6. The lower limits of normality can be set at 7.0 and 1.2 for the outer and inner dynein arms respectively. The dynein arms and spokes were not influenced by the percentage of secondary abnormalities. In conclusion, dynein arms and spokes are readily identified after ciliogenesis in culture. These parameters are independent of secondary ciliary dyskinesia.

Secondary ciliary dyskinesia is absent after ciliogenesis in culture.

Ultrastructural secondary ciliary dyskinesia (SCD) was measured using transmission electron microscopy in 301 biopsies and 439 samples after ciliogenesis in the sequential monolayer-suspension culture. Biopsies were taken in the context of exclusion of primary ciliary dyskinesia. SCD was frequently found in the biopsies: only 30% of the samples were normal (SCD < 5%), the mean percentage of SCD abnormalities was 11.9 +/- 12.9%. In 1/8 of the samples severe SCD (> 25%) was present. The most frequently encountered SCD abnormality was the membrane bleb, followed by the various peripheral microtubular abnormalities. With increasing total SCD the absence of the central pair became more important. After ciliogenesis in culture SCD was virtually absent: 1.0 +/- 1.8% for all 439 samples, 96% of the samples were within limits of normality (SCD < 5%). Moderate (15-25%) and severe SCD (> 25%) were never found. In more than 50% of the samples not one abnormality was found. There was no relation between the SCD in the biopsy and that after ciliogenesis. The absence of SCD after ciliogenesis is a major advantage for the diagnosis of PCD, specifically in cases with central pair abnormalities, peripheral microtubular pair abnormalities and those without a primary ultrastructural abnormality.

Ultrastructural expression of primary ciliary dyskinesia after ciliogenesis in culture.

During the period 1990-1999 84 PCD patients were identified and characterized. The expression of inherited abnormalities in primary ciliary dyskinesia after ciliogenesis was investigated in 41 patients with dynein deficiency, 6 patients with absence of the central pair of microtubules and 24 PCD patients with normal ultrastructure. In patients with dynein deficiency, the outer dynein arms counts were 1.9 +/- 1.0 in the biopsies and 1.6 +/- 0.7 after ciliogenesis. Secondary abnormalities were found in 15.8 +/- 20.4% of the transverse sections of cilia and only in 1.0 +/- 1.3% after ciliogenesis. Ciliary orientation was 28 +/- 11 degrees and 24 +/- 10 degrees respectively in biopsies and cultures. In patients with absence of the central pair this was found in 15 +/- 16% in biopsies and 21 +/- 19% after ciliogenesis. The values for the outer dynein arm were 8.4 +/- 0.3 and 8.7 +/- 0.2 and for the secondary abnormalities were 11.7 +/- 7.3% and 0.5 +/- 1.3% in the biopsies, respectively after ciliogenesis. In patients with normal ultrastructure the scores for the dynein arms were similar. Secondary abnormalities were found in 12.2 +/- 11.7% in the biopsies and 0.6 +/- 0.9% after ciliogenesis while ciliary orientation was respectively 21 +/- 7 degrees and 25 +/- 8 degrees. In conclusion, inherited abnormalities in primary ciliary dyskinesia are expressed after ciliogenesis, while secondary abnormalities are virtually absent, thereby facilitating the ultrastructural diagnosis.

Use of thymidine analogues to indicate vascular perfusion in tumours.

Temporary reduction in blood-flow within tumour blood vessels can reduce oxygen supply leading to transient perfusion-limited hypoxia. Consequent selection of cells with mutations and reduced radiosensitivity can lead to disease progression and treatment-resistance. In the present study, we investigated whether heterogeneity of labelling after thymidine analogue administration is related to perfusion variations, and if so, could it be quantified and used as a perfusion indicator. Perfusion in murine RIF1 tumours was reduced by hydralazine or increased by nicotinamide and the mice subsequently injected with IdUrd. Tumours were halved for analysis by both flow cytometry and immunohistochemistry. Tumour sections were stained for vasculature and IdUrd. Each blood vessel was scored for the density of IdUrd-labelled cells surrounding it, using a semi-quantitative scoring system. Flow cytometry showed that the IdUrd labelling index and intensity decreased by approximately 50% after hydralazine. In tumour sections of control animals, 2.9% of vessels showed no IdUrd label. In contrast, after hydralazine almost 50% of vessels had no surrounding IdUrd labelling, whereas after nicotinamide there were fewer vessels with low labelling and a higher median score. In conclusion, changes of tumour perfusion by pharmacological agents is reflected in changes in tumour-cell labelling by the thymidine analogue IdUrd, suggesting that IdUrd labelling could be used to indicate perfusion in individual vessels in human tumours.

Acquisition of androgen-mediated expression of mouse vas deferens protein (MVDP) gene in cultured epithelial cells and in vas deferens during postnatal development.

We used cultured vas deferens epithelial cells (VDECs) as a model system to determine the conditions that allow mouse vas deferens protein (MVDP) gene expression and acquisition of androgen responsiveness. On the basis of Northern blot analysis, the mvdp gene is constitutively expressed at very low levels in prepubertal VDECs grown on collagen-coated plastic or on microporous membrane inserts. In the presence of dihydrotestosterone (DHT), mvdp messenger RNA levels dramatically increased in cells cultured on microporous membrane inserts and stayed unchanged in cells grown on matrix-coated plastic. Epithelial cells derived from fetal vas deferens were able to synthesize MVDP in response to DHT, and the presence of fetal mesenchymal cells did not influence MVDP production. Providing the cells with a culture procedure that permits access to the basolateral membranes and caters to the polarity requirements of the cell is a prerequisite for androgen induction of MVDP gene expression. The results also point to a role for epidermal growth factor, insulin, and tyrosine kinase activity in mediating the action of androgen on mvdp gene expression. In vivo studies show that the first expression of the mvdp gene between 5 and 7 days postpartum is not associated with major structural changes in the epithelium. The acquisition of a mature phenotype by epithelial and peritubular contractile cells, between 10 and 20 days, correlates with androgen dependency of the mvdp gene. We propose that cell differentiation and polarization on a matrix-coated microporous membrane reproduces some of the events that are necessary for acquisition of androgenic responsiveness of the mvdp gene during postnatal development.