Capillary Basement Membrane Thickness Research Articles

Cytomegalovirus infection-enhanced chronic kidney allograft rejection is linked with intercellular adhesion molecule-1 expression

In human kidney allografts, association of acute rejection and glomerulopathy with cytomegalovirus (CMV) infection has been demonstrated. To investigate the effect of CMV infection on the development of experimental chronic kidney allograft rejection, heterotopic kidney allografts from DA (Ag-B4, RT1a1) rat donors to WF (Ag-B2, RT1u) rat recipients were used. The animals received cyclosporine A (CsA) 5 mg/kg/day s.c. either for 1 or 12 weeks. Two groups of recipients were infected with 10(5) plaque-forming units of rat CMV (RCMV) and two other groups were left noninfected and used as controls. The grafts were removed 12 weeks after transplantation for histology and immunohistochemistry. RCMV infection significantly enhanced the development of chronic kidney allograft rejection in rats on continuous CsA the intensity of interstitial inflammation (P < 0.025), particularly the degree of pyroninophilic cells in the inflammatory infiltrate (P < 0.025), the glomerular mesangial matrix increase (P < 0.05) and capillary basement membrane thickening (P < 0.01), the extent of endothelial cell swelling (P < 0.025) and intimal proliferation (P < 0.025) in the graft vasculature, and the extent of tubular epithelial atrophy (P < 0.025). Chronic allograft damage index (CADI) was significantly increased to 4.3 +/- 0.8 in RCMV-infected allografts, compared to 0.8 +/- 0.4 in noninfected (P < 0.02). In addition, RCMV infection significantly increased the number of acute rejection episodes (serum creatinine > 200 mumol/liter, P < 0.05) and almost doubled the end-stage serum creatinine. RCMV infection significantly increased ICAM-1 expression on the vascular endothelium (P < 0.05) and tubular epithelial cells (P < 0.01), and was linked with enhanced interstitial, glomerular, and tubular inflammation. In 80% of allografts on continuous CsA, RCMV antigens could be observed in sporadic inflammatory cells one week after infection and in tubular epithelial cells at 12 weeks. In heavily inflamed allografts where the CsA treatment was discontinued at one week, enhancement of RCMV infection on the histological changes attributable to chronic kidney allograft rejection could not be demonstrated. Our results show that during CsA immunosuppression, RCMV infection enhances chronic kidney allograft rejection associated with increased interstitial inflammation as well as vascular endothelial and tubular epithelial ICAM-1 expression.

Endurance exercise training decreases capillary basement membrane width in older nondiabetic and diabetic adults.

The objectives of these studies were to 1) evaluate the relationships among age, glucose intolerance, and skeletal muscle capillary basement membrane (CBM) width (CBMW) and 2) determine the effects of exercise training on CBMW by comparing values of young (28 +/- 4 yr) and older (63 +/- 7 yr) athletes with those of age-matched sedentary control subjects and by measuring CBMW in older men and women before and after a 9-mo endurance-exercise training program. CBMW was measured in tissue samples obtained from the gastrocnemius muscle. CBMW in sedentary 64 +/- 3-yr-old subjects was 25% thicker than in sedentary 24 +/- 3-yr-old subjects. CBMW was similar in young and older athletes and was thinner than the CBMW of age-matched sedentary control subjects. There were no differences in CBMW among older sedentary individuals with normal or impaired glucose tolerance or mild non-insulin-dependent diabetes mellitus. Nine months of endurance exercise training reduced CBMW in older men and women by 30-40%, to widths that were not different from those of the young subjects; this response was independent of glucose tolerance status. These findings suggest that habitual exercise prevents the thickening of the skeletal muscle CBM that is characteristic of advancing age. Moreover, the thickening of the CBM appears to be readily reversed as a result of exercise training, even in older individuals.

Rat cytomegalovirus infection and chronic kidney allograft rejection.

To investigate the effect of cytomegalovirus (CMV) infection on the development of experimental chronic kidney allograft rejection, orthotopic kidney allografts from DA donors (Ag-B4, RT1a1) to WF (Ag-B2, RT1u) recipients were used. The rats received cyclosporine A (CsA) for 12 weeks. A group of recipients was infected with 10(5) plaque-forming units of rat CMV (RCMV), and another group was left non-infected and used as controls. The grafts were removed 12 weeks after transplantation. RCMV infection significantly enhanced the development of chronic kidney allograft rejection as follows: the intensity of interstitial inflammation (P < 0.025), particularly the degree of pyroninophilic cells in the inflammatory infiltrate (P < 0.025); the glomeruli mesangial matrix increase (P < 0.05) and capillary basement membrane thickening (P < 0.01); the extent of endothelial cell swelling (P < 0.025) and intimal proliferation (P < 0.025) in the graft vasculature; and the extent of tubular epithelial atrophy (P < 0.025). The chronic allograft damage index (CADI) was significantly increased to 4.2 +/- 0.9 in RCMV-infected allografts, compared with 0.8 +/- 0.4 in non-infected (P < 0.02). At the molecular level, RCMV infection significantly increased vascular endothelial (P < 0.05) and tubular epithelial (P < 0.01) ICAM-1 expression. Viral antigens were detected in tubular epithelial cells and in some inflammatory cells.

Microvascular Response to Tissue Injury and Capillary Ultrastructure in the Foot Skin of Type I Diabetic Patients

1. Microvascular blood flow responses to injury and capillary ultrastructure were assessed by laser Doppler flowmetry and detailed light and electron microscopy respectively in skin biopsied from 28 patients with insulin-dependent diabetes and 17 control subjects. 2. The hyperaemic response induced by biopsy (P < 0.001) and heating to 44 degrees C (P < 0.001) was significantly lower in the diabetic patients and showed progressive impairment with the severity of complications (P < 0.001). 3. Skin capillary basement membrane thickness was significantly increased in the diabetic patients (P < 0.001) and also increased with the severity of complications (P < 0.002). Both the luminal area (P < 0.001) and the endothelial cell outer perimeter (P < 0.002), measures of luminal and capillary size, respectively, were significantly reduced in all diabetic patients. 4. Basement membrane thickness was related significantly to the impaired hyperaemic response to both biopsy (P < 0.01) and thermal injury (P < 0.01). 5. Our findings support the hypothesis that structural abnormalities, which are characterized by an early reduction in capillary size and later thickening of basement membrane, form an important mechanism for the impaired hyperaemic response in diabetic patients.

A histological and immunohistological study of malarial placentas.

Sections of 18 malaria-infected placentas were stained with haematoxylin and eosin, periodic acid and methenamine silver, and immunohistochemically with monoclonal antibodies against human common leukocyte antigen, CLA (CD 45), B cells (CD 20, L 26), T cells (CD 45RO, UCHL-1) and collagen IV. Parasitized erythrocytes accumulated in the maternal villous spaces, with none in the foetal circulation. These were found in association with inflammatory leukocytes and pigments. Fibrinoid necrosis was more prevalent in the heavily infected placentas. Thickening and reduplication of foetal capillary basement membranes, and a decrease in leukocytes, including B and T cells, were seen in the heavily infected placentas. These findings are in keeping with previously reported depression of cellular and humoral immunity in patients with heavy parasitaemia.

Hyperglycemia and non-enzymatic glycation of serum and tissue proteins in chickens

The objectives of these studies were to determine whether elevated plasma glucose concentrations in broiler breeder chickens (200–250 mg/dl) can result in the non-enzymatic attachment of glucose to serum proteins (fructosamine) and eventual cross-linking of tissue proteins (basement membrane thickness), and to investigate the effects of a factor that may influence this cross-linking process. In response to feeding the satiety factor calcium propionate (CaP, 1.7%), plasma glucose and fructosamine concentrations were increased ( P < 0.05) from 1 to 9 weeks of age, whereas concentrations of plasma glucose and fructosamine in feed-restricted chicks were reduced for the first 7 weeks after hatch. In a second study, the age-related increase in kidney capillary basement membrane thickness was prevented ( P < 0.05) by feeding the cross-linking inhibitor aminoguanidine (AG, 800 ppm) to 30-week-old broiler breeder hens for 34 weeks. The results from these studies suggest that concentrations of plasma glucose in chickens may, in fact, be exerting long-term detrimental effects on tissue proteins, which can be ameliorated by factors that limit the cross-linking reaction.

An electron microscopic study of muscle capillary wall thickening in systemic lupus erythematosus.

Capillary vessel wall thickening may contribute to the muscle fibre atrophy and impaired pulmonary gas transfer notable in SLE/MCTD. Using electron microscopy we measured the thickness of unilaminar capillary basement membranes (CBM) and quantified basement membrane laminae and pericyte layers in the skeletal muscle biopsies of 31 patients with SLE, including 14 with MCTD, and 11 controls. Capillary basement membrane thickness was significantly increased in SLE compared with controls (P < 0.01) and was significantly associated with the level of C3dg (P < 0.01). Patients with MCTD had significantly greater layering of pericytes and laminae compared with patients with SLE alone (P < 0.0001 for both variables). Multiple stepwise regression analysis indicated that ANA titre was a good predictor of pericyte layering (R = 0.63, P = 0.003) and of basement membrane lamination (P < 0.0001), with steroid therapy having a significant negative association with the number of laminae (P < 0.02). A negative association between KCO and the number of layers of basement membrane (R = 0.51, P = 0.01) was documented. However, multiple regression analysis revealed no association between parameters of thickened vessel walls and the presence of muscle fibre atrophy.

Alterations in Viscosity and Filterability of Whole Blood and Blood Cell Subpopulations in Diabetic Cats

Capillary closure and venous dilatation occur early in diabetic retinopathy, and altered blood rheology may play a role. For example previous studies have shown leukocytes are less deformable, are more activated, and occlude retinal capillaries more often in diabetic subjects. The purpose of this study was to determine if rheologic changes developed in diabetic eats, a model in which we have documented retinal capillary basement membrane thickening, microaneurysms, and intraretinal hemorrhage characteristic of early diabetic retinopathy. Viscosity of blood, plasma and purified erythrocyte suspensions was measured by rotational viscometry and plasma fibrinogen content was deterarmed by heat precipitation. Filterability of blood and purified erythrocyte, mononuclear leukocyte, and granulocyte suspensions was determined at constant flow, measuring the increase in pressure over 2 min relative to the pressure generated by buffer alone. Viscosity of whole blood and plasma, but not erythrocytes, was significantly elevated ( P < 0·005) in the diabetic cats over normals at all shear rates studied (450, 225 and 90 sec -1). Furthermore, fibrinogen levels were significantly elevated in diabetic cats compared to normals ( P < 0·004), and were positively correlated with the viscosity of whole blood and plasma. The filterability of mononuclear leukocytes and whole blood in diabetic cats was decreased 56% and 74% when compared to normals, P > 0·0006 and P < 0·025, respectively. In contrast, the filterability of granulocytes and erythrocytes was not significantly different between the two groups. These results suggest that the rheologic alterations in diabetes are numerous, and involve both cellular and plasma protein changes. The changes in the fibrinogen levels, plasma and whole blood viscosity, and mononuclear cell filterability may play important roles in the genesis of diabetic microangiopathy.

Origin of the microangiopathic changes in diabetes.

The mechanism of development of microangiopathy is incompletely understood, but relates to a number of ultrastructural, biochemical and haemostatic processes. These include capillary basement membrane thickening, non-enzymatic glycosylation, possibly increased free radical activity, increased flux through the polyol pathway and haemostatic abnormalities. The central feature appears to be hyperglycaemia, which is causally related to the above processes and culminates in tissue ischaemia. This article will briefly describe these processes and will discuss possible pathogenic interactions which may lead to the development of the pathological lesion.

Correlation between erythrocyte aldose reductase activity and the width of skeletal-muscle capillary basement membrane in insulin-dependent diabetes mellitus

Thickening of capillary basement membrane has been demonstrated in diabetic subjects, and it is considered to be the characteristic pathological lesion of diabetic microvascular disease. There are studies reporting the effects of inhibitors of aldose reductase, the first enzyme of the polyol pathway, on the thickening of the capillary basement membrane. These observations indicate a significant role of the polyol pathway in the development of microvascular disease. However, it is unknown whether or not there is any correlation between the thickness of the capillary basement membrane and the activity of aldose reductase in diabetic patients. To clarify this issue, we measured the width of skeletal-muscle basement membrane and erythrocyte aldose reductase activity in 27 insulin-dependent diabetic and 8 nondiabetic individuals. The results showed that both the aldose reductase activity and the width of capillary basement membrane were increased in diabetic patients as compared to nondiabetic individuals (6.89 ± 0.38 versus 5.15 ± 0.60 mL/mU erythrocytes, p < 0.05 and 2257 ± 166 versus 1136 ± 69 Å, p < 0.0001, respectively) (means ± SE), but marked variability was observed in both the enzyme activity and the basement membrane thickness among the diabetic patients. There was a significant correlation between the capillary basement membrane thickness and the activity of erythrocyte aldose reductase ( r = 0.51, p < 0.01) in diabetic patients. Our data suggest that the polyol pathway plays an important role in thickening of capillary basement membrane in diabetic individuals, and the variability in aldose reductase activity seen among diabetic patients may result in the varying susceptibility to the development of diabetic microvascular disease.

Glycemic control and diabetic complications.

The relationship between glycemic control and diabetic complications remains unclear. Epidemiological studies reveal that approximately 25% of diabetic individuals do not develop complications, irrespective of degree of glycemic control. Studies of genetic factors, including HLA type, capillary basement membrane thickness, genetic predisposition to hypertension, and familial clustering of diabetic complications, suggest that there is a genetic component to developing the complications of diabetes. On the other hand, clinical trials have demonstrated that the progression of early, mild background retinopathy, microalbuminuria, and parameters of nervous system function are stabilized with improved glycemic control. Other metabolic parameters, such as serum lipoprotein levels, are significantly improved with near normoglycemia. No studies to date have evaluated the effect of blood glucose control on the prevention of diabetic complications. The degree of glycemic control required to impact on diabetic complications is unknown. In addition, achieving near normoglycemia carries increased risk for severe hypoglycemia and weight gain. Further study is needed to determine the long-term benefits of blood glucose control and to weigh that against the risks of improving glycemic control. Further investigation also is needed to address the probable interrelationship of genetic factors and glycemic control on the development of diabetic complications.

The influence of diabetes on free flap transfer: I. Flap survival and microvascular healing.

Although recent clinical case presentations suggest that diabetes does not predispose free tissue transfers to increased risk of failure, this remains an open question. The present study used a syngeneic rat strain (Lewis) for free groin flap transplantations between normal rats and streptozotocin-induced diabetic rats (2 months' duration of symptoms), to investigate the influence of diabetes on flap transfer. Flap survival at 1 week, vascular patency, flap histology and ultrastructure, and scanning electron microscopy of anastomotic sites and of corrosion casts of flap vasculature were used as bases for comparison. No differences were found in comparisons of flap survival between any groups of transfer combinations (normal flap onto normal recipient, diabetic flap onto normal recipient, normal flap onto diabetic recipient, and diabetic flap onto diabetic recipient); 100% success was achieved in each group. No differences were found in histology or corrosion casts. Transmission electron microscopy revealed a thickening of the capillary basement membrane in rat diabetic skin after only 8 weeks of symptoms. This ultrastructural finding is consistent with similar capillary basement membrane thickening seen in many other tissues of short- and long-term diabetic animals and humans. Re-endothelialization across the arterial anastomosis at 2 weeks postoperatively was significantly faster in normal versus diabetic animals (p less than 0.05). The predominantly negative findings of this study support the application of free flap transfers in diabetic patients. It is concluded that reconstructive efforts involving free tissue transfer may not be contraindicated in diabetic patients.

Skin flow the venoarteriolar response and capillary filtration in diabetics. A 3-year follow-up.

Resting skin blood flow (RF) and the venoarteriolar response (VAR = the vasoconstrictor response on standing) have been studied in 100 patients with diabetic neuropathy, in 100 diabetics without neuropathy, and in 100 normal subjects by laser Doppler flowmetry. Capillary filtration was also studied with strain gauge plethysmography. The authors followed up these patients by evaluating their microcirculation again after three years. At the beginning of the study in patients with neuropathy, RF and capillary filtration were increased. The VAR and the microangiopathy index (MI = VAR/RF) were reduced in all diabetics, to a greater extent to those with neuropathy. After three years the authors observed an increase in capillary filtration associated with a further impairment in VAR and MI, suggesting progression of microangiopathy in both groups of diabetics. These results suggest that the postural control of blood flow in the skin of the foot is impaired in diabetic microangiopathy, particularly in neuropathics. Increased skin blood flow and capillary filtration and the impaired venoarteriolar response cause edema and may contribute to the thickening of capillary basement membranes and the progressive evolution of diabetic microangiopathy.

Relationships between Haemostatic Factors and Capillary Morphology in Human Diabetic Neuropathy

We have examined haemostatic factors in 15 diabetic patients with peripheral neuropathy and 10 diabetic patients without clinical complications. Plasma and blood viscosity, fibrinogen, factor VIIIc, von Willebrand factor activity, spontaneous platelet aggregation and fibrinolytic activity were not significantly different between diabetic patients without clinical complications and diabetic patients with peripheral neuropathy. Platelet aggregation was enhanced in diabetic patients with neuropathy compared with those without complications. In the 15 patients with neuropathy and 3 without complications, who underwent biopsy of sural nerve, skin and muscle, associations were found between haemostatic variables and measures of nerve capillary pathology, notably: plasma fibrinogen and nerve capillary basement membrane thickness (r = 0.70, p < 0.001); thromboxane B2 production and nerve capillary basement membrane thickness (r = -0.61, p < 0.01); plasma fibrinolytic activity and endoneurial capillary lumen size (r = 0.60, p < 0.01) and endothelial cell outer perimeter (r = 0.65, p < 0.01). The main associations of skin and muscle capillary abnormalities were with measures of in vitro platelet aggregation, and the correlations found with nerve capillary measurements were not echoed in the overlying muscle and skin. The results are supportive of the involvement of haemostatic abnormalities in the pathogenesis of diabetic neuropathy.

The Venoarteriolar Response in Diabetics

Resting skin blood flow and the venoarteriolar response (VAR) were studied in 40 patients with diabetic microangiopathy and neuropathy, in 40 diabetics with microangiopathy, and in 30 normal subjects by means of laser-Doppler flowmetry. In patients with microangiopathy and neuropathy, resting flow (RF) was increased and the VAR was impaired to a greater extent than in patients without neuropathy. There was also a significant delay in the VAR in diabetics, particularly in patients with neuropathy. The microangiopathy index (VAR/RF) was on the average 71.3 in normal subjects, significantly lower (p less than 0.05) in diabetics without neuropathy (34.8), and even lower in those with neuropathy (13.6). The VAR was evaluated with different postural changes; The authors observed that in the passage from supine to standing the VAR is more evident. In conclusion these results confirm that the postural control of blood flow in the skin of the foot is impaired in diabetic microangiopathy, particularly in patients with neuropathy. The increased skin blood flow and the impaired VAR are causes of edema and may contribute to the thickening of capillary basement membranes observed in diabetes.

The effect of aldose reductase inhibition with ponalrestat on the width of the capillarly basement membrane in diabetes mellitus

There is evidence to suggest that hyperglycemia is required for the development of the microvascular complications of diabetes. However, the precise mechanism by which hyperglycemia might cause diabetic complications is not completely clear. One possibility is the increased activity of the polyol pathway. Capillary basement membrane thickness is a hallmark histological finding in diabetic microangiopathy. Previous studies in experimental models of diabetes have related the polyol pathway with the thickness of basement membrane in retinal capillaries. To study the effect of aldose reductase inhibition with ponalrestat on the width of the skeletal muscle capillary basement membrane in subjects with diabetes, we measured the capillary basement membrane width in 55 subjects with diabetes in a double masked, placebo controlled randomized trial over a period of 18 months. Twenty-nine patients received ponalrestat (two 300 mg tablets daily) and twenty-six received placebo tablets. The age, sex distribution, type and duration of diabetes were similar in both groups. The glycosylated hemoglobin remained at a constant level throughout the study in both groups. The baseline capillary basement membrane width of the ponalrestat group was 3134 ± 146 Å, it was 3074 ± 226 Å at month 12 and 2548 ± 182 Å at month 18 ( P < 0.001 vs baseline value). The placebo group also had a significant reduction in the width of the capillary basement membrane, from a baseline value of 3026 ± 147 Å to 2818 ± 144 Å at month 12 and 2618 ± 156 Å at month 18 ( P < 0.001 vs baseline value). There was no statistical difference in the capillary basement membrane width between the two groups at any time point. In conclusion, our study showed no effect on skeletal muscle basement membrane width following 18 months of treatment with the aldose reductase inhibitor, ponalrestat, as compared to placebo. It is possible that in the skeletal muscle capillaries the thickening of the capillary basement membrane width induced by diabetes is mediated by mechanisms other than the polyol pathway.

Vagus Nerve Morphology in Diabetic Gastropathy

Two patients were treated with gastroenterostomy and vagotomy for intractable vomiting due to diabetic gastropathy. A morphometric examination of nerve fibres and capillaries in their resected abdominal vagi was performed and the results were compared with findings from two diabetic and two non-diabetic patients undergoing gastroenterostomy and vagotomy for duodenal ulceration. All four diabetic patients had pathological changes of a similar character: reduced myelinated fibre density, degeneration and regeneration of unmyelinated fibres, and capillary basement membrane thickening. Abnormalities were more pronounced in the two diabetic patients with gastropathy but intact and regenerating nerve fibres were still present. The findings support the view that vagal neuropathy could be a causal factor in diabetic gastropathy but imply that severe gastropathy with vomiting is not simply a consequence of autovagotomy. The morphological observations indicated that structural changes can occur in the autonomic nerves of diabetic patients who do not develop autonomic symptoms or have easily detectable abnormal autonomic physiology.

Relationship of Endoneurial Capillary Abnormalities to Type and Severity of Diabetic Polyneuropathy

Endoneurial capillary abnormalities have been assessed quantitatively in sural nerve biopsies from diabetic patients with different syndromes of sensory polyneuropathy: chronic painful neuropathy, newly presenting painful neuropathy, and painless neuropathy associated with neurotrophic foot ulceration. Comparisons were made with age-matched nondiabetic control subjects. The diabetic groups showed no abnormality in capillary density or mean endoneurial area per fascicle. Compared with control subjects, all diabetic patients had an increase in mean capillary diameter, capillary wall thickness, and outer tunic (basement membrane and pericytes) thickness. The increase in wall thickness was most pronounced in patients with painless neuropathy (200%) and less marked in similar patients with painful neuropathy (100%). The pericyte volume fraction of the outer tunic was reduced in all diabetic patients, implying that basement membrane hypertrophy and reduplication were responsible for outer tunic thickening. There was evidence of endothelial cell hyperplasia rather than hypertrophy. There was a correlation between the degree of basement membrane thickening and the severity of myelinated fiber abnormality assessed neurophysiologically and morphologically. This study shows a link between the degree of endoneurial capillary basement membrane thickening, the type of neuropathology, and the clinical expression of neuropathy in diabetes mellitus.

Increases in collagen type IV and laminin in galactose-induced retinal capillary basement membrane thickening—Prevention by an aldose reductase inhibitor

Biochemical alterations in the composition of retinal capillary basement membrane components were investigated in galactosemic rats, an animal model that develops basement membrane lesions comparable to those of diabetic retinopathy. Normotensive Wistar-Kyoto rats fed a 30% galactose diet for 9 months developed significant thickening of retinal capillary basement membranes by comparison with animals fed a control test diet ( P < 0·001), or animals on a diet containing 30% galactose and 250 mg kg −1 of the aldose reductase inhibitor sorbinil ( P < 0·001). A quantitative electron microscopic immunogold technique applied on ultrathin sections of the retinas of these animals showed that the labeling densities of collagen type IV and laminin per unit cross-sectional area (which is presumably proportional to the concentrations of these molecules) were significantly increased in the retinal capillary basement membranes of galactose-fed rats, compared with animals on the control test diet. Increases in these two components of basement membranes were prevented by addition of sorbinil to the diet. However, there was no significant change in the labeling density of heparan sulfate proteoglycan (HSPG) core protein in the basement membranes of galactose-fed rats in comparison to animals on either the control diet or galactose-sorbinil diet. Two types of striated fibrillar materials were frequently found in areas of focal thickening of basement membranes of galactose-fed rats only. Thinner fibrils reacted strongly with collagen type III antibody, whereas thicker fibrils reacted weakly with collagen type I antibody. Our results indicate that there is an increase in labeling densities of collagen type IV and laminin in thickened basement membranes of retinal capillaries of galactosemic rats along with the expression of interstitial collagens like collagen type III and an abnormal collagen that weakly cross-reacts with antibody to collagen type I, and these effects of galactosemia on the basement membranes are preventable by an aldose reductase inhibitor.

Changes in Steady-State Levels of Mrnas Coding for Type IV Collagen, Laminin and Fibronectin Following Capillary Basement Membrane Thickening in Human Adult Onset Diabetes

The development of capillary basement membrane thickening has been linked to microvascular changes known to occur in tissues of patients with type II diabetes. Previous evidence has suggested that capillary basement membrane thickening is due to increased basement membrane synthesis. In this study, skin samples from 8 diabetic patients with confirmed capillary basement membrane thickening and 7 non-diabetic controls were used to assess steady state levels of mRNAs coding for several basement components including pro alpha 1(IV) collagen, laminin and fibronectin. Total RNA was extracted from abdominal skin samples and levels of mRNAs coding for the basement membrane components laminin, fibronectin and pro alpha 1(IV) collagen, a fibrillar collagenous protein, pro alpha 1(I) collagen and an intracellular polypeptide, gamma-actin, were determined by dot blot hybridization analysis. While there were no changes of steady state levels of pro alpha 1(I) collagen mRNA and laminin mRNA, a significant reduction was noted in the quantitative recovery of mRNA levels for pro alpha 1(IV) collagen, gamma-actin and fibronectin in total RNA isolated from the skin of diabetic patients. This reduction in levels of mRNAs coding for basement membrane components contrasts with pathological confirmation of an accumulation of endothelial capillary basement membrane in skin from diabetic patients and suggests that basement membrane thickening arises more as a consequence of reduced basement membrane degradation than elevated synthesis of basement membrane components.