Enhancement of cell-based therapeutic angiogenesis using a novel type of injectable scaffolds of hydroxyapatite-polymer nanocomposite microspheres

BACKGROUND

Clinical trials demonstrate the effectiveness of cell-based therapeutic angiogenesis in patients with severe ischemic diseases; however, their success remains limited. Maintaining transplanted cells in place are expected to augment the cell-based therapeutic angiogenesis. We have reported that nano-hydroxyapatite (HAp) coating on medical devices shows marked cell adhesiveness. Using this nanotechnology, HAp-coated poly(l-lactic acid) (PLLA) microspheres, named nano-scaffold (NS), were generated as a non-biological, biodegradable and injectable cell scaffold. We investigate the effectiveness of NS on cell-based therapeutic angiogenesis.

METHODS AND RESULTS

Bone marrow mononuclear cells (BMNC) and NS or control PLLA microspheres (LA) were intramuscularly co-implanted into mice ischemic hindlimbs. When BMNC derived from enhanced green fluorescent protein (EGFP)-transgenic mice were injected into ischemic muscle, the muscle GFP level in NS+BMNC group was approximate fivefold higher than that in BMNC or LA+BMNC groups seven days after operation. Kaplan-Meier analysis demonstrated that NS+BMNC markedly prevented hindlimb necrosis (P<0.05 vs. BMNC or LA+BMNC). NS+BMNC revealed much higher induction of angiogenesis in ischemic tissues and collateral blood flow confirmed by three-dimensional computed tomography angiography than those of BMNC or LA+BMNC groups. NS-enhanced therapeutic angiogenesis and arteriogenesis showed good correlations with increased intramuscular levels of vascular endothelial growth factor and fibroblast growth factor-2. NS co-implantation also prevented apoptotic cell death of transplanted cells, resulting in prolonged cell retention.

CONCLUSION

A novel and feasible injectable cell scaffold potentiates cell-based therapeutic angiogenesis, which could be extremely useful for the treatment of severe ischemic disorders.

Fetuin-A: a multifunctional protein

Sixty-six years have elapsed since the discovery of fetuin in 1944, but its importance in mammalian physiology has only recently been appreciated. Fetuin, first isolated from fetal bovine serum and now most commonly known as either fetuin-A, alpha-2-HS-glycoprotein (recommended name by UniprotKB and PIR), or α2-Heremans-Schmid glycoprotein, functions as an important component of diverse normal and pathological processes, including vascular calcification and bone metabolism regulation, insulin resistance, protease activity control, keratinocytes migration, and breast tumor cell proliferative signaling. Fetuin-A has also been identified as a biomarker for neurodegenerative disease. Here, we summarize recent publications focusing on the structural and functional properties of fetuin-A. The emerging importance of fetuin-A for both diagnosis and therapeutics has come to the attention of the pharmaceutical industry. Therefore, we will discuss the status of patents based on fetuin-A.

Fetuin-A and the cardiovascular system

Fetuin was first isolated from bovine serum in 1944. It is now most commonly known as either fetuin-A or alpha-2-HS-glycoprotein (AHSG), the protein product of Ahsg gene. A prominent feature of this protein is the functional diversity exerted in human physiology and pathophysiology. Fetuin-A plays a role in bone metabolism, metabolic disorders such as insulin resistance and diabetes mellitus (DM), and central nervous system (CNS) disorders such as ischemic stroke (IS) and neurodegenerative diseases. In addition, emerging evidence suggests involvement of fetuin-A in the cardiovascular system. However, there are many discordant findings on the associations between fetuin-A and vascular diseases. In other words, it is unknown whether fetuin-A is an exacerbating or a protective factor in the cardiovascular system. One reason for the seemingly inconsistent behavior is the dual functionality of fetuin-A in vascular diseases where it can act as an atherogenic factor or as a vascular calcification inhibitor. In addition, the existence of confounding factors such as DM and renal dysfunction can veil the primary association between fetuin-A and clinical parameters. Considering these issues, we discuss the role of fetuin-A for atherosclerosis and vascular calcification in this review.

Association of endothelial and vascular smooth muscle dysfunction with cardiovascular risk factors, vascular complications, and subclinical carotid atherosclerosis in type 2 diabetic patients

AIM

Atherosclerosis and arteriosclerosis are mainly caused by the dysfunction of arterial components, namely, vascular endothelial cells, smooth muscle cells, and the extracellular matrix. Endothelial dysfunction is well established as a predictive surrogate marker of cardiovascular events; however, little is known regarding the clinical implications of vascular smooth muscle dysfunction for cardiovascular disease and microangiopathy. In the present study, we aimed to clarify the association of arterial dysfunction with micro-/macroangiopathy and conventional cardiovascular risk factors in 181 type 2 diabetic patients (T2DM; age ± SD, 64 ± 10 years; duration of diabetes, 12 ± 10 years).

METHODS

Flow-mediated dilatation (FMD) and nitroglycerin-mediated dilatation (NMD) were assessed to evaluate endothelial dysfunction and vascular smooth muscle dysfunction, respectively, by using a novel ultrasound device, UNEXEF18G (Unex Co. Ltd., Japan).

RESULTS

The FMD and NMD were 6.4 ± 3.9% and 13.4 ± 6.6%, respectively. No significant differences in FMD were noted between T2DM with and without micro- or macroangiopathy; however, NMD in T2DM patients with micro- and macroangiopathy was significantly lower than that in T2DM patients without angiopathy. NMD decreased with the progression of chronic kidney disease (CKD) stage (p = 0.005), but not FMD (p = 0.071). On multiple regression analysis, significant independent contributors to FMD were age, smoking, systolic blood pressure, glycosylated hemoglobin, and serum total cholesterol, while those for NMD were age, systolic blood pressure, and waist circumference.

CONCLUSION

The relationship of vascular complications and cardiovascular risk factors with NMD is different from that with FMD in type 2 diabetic patients.

Evaluation of bone markers in hypophosphatemic rickets/osteomalacia

N-terminal propeptide of type I procollagen (PINP) is a marker of newly formed type I collagen. However, its role in hypophosphatemic rickets/osteomalacia has not yet been established. Metabolic bone markers were examined in patients with oncogenic osteomalacia (OOM) and X-linked hypophosphatemic rickets (XLH), and in healthy controls. OOM and XLH patients were found to have hypophosphatemia secondary to elevated levels of serum fibroblast growth factor 23 (FGF-23). OOM patients had reduced levels of 1,25-dihydroxy vitamin D (1,25D) compared with XLH patients and healthy controls, despite attenuation of the reduction in these levels in the XLH patients secondary to active vitamin D supplementation. In contrast to patients with XLH, OOM patients showed a significant increase in serum PINP, which is suggestive of accelerated bone matrix formation. Bone alkaline phosphatase (BAP) and the BAP/PINP ratio were also increased in OOM but not in XLH patients, suggesting the presence of a disturbance in bone mineralization in OOM. Long-term supplementation of active form vitamin D and inorganic phosphate (IP) may have attenuated the defect in bone mineralization in the XLH patients, resulting in the normalization of PINP, BAP, and the BAP/PINP ratio. The present results suggest that, as with BAP, PINP is an appropriate metabolic bone marker in the assessment of hypophosphatemic rickets/osteomalacia.

Active vitamin D and acute respiratory infections in dialysis patients

BACKGROUND AND OBJECTIVES

Vitamin D has gained attention for its pleiotropic effects in areas other than bone metabolism, and the effects of vitamin D in preventing respiratory infections have been reported as one of its immunomodulating properties. This study assessed the preventive effect of vitamin D receptor activator (VDRA) on respiratory infections in dialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Maintained Japanese hemodialysis patients (n = 508) were observed for 5 years, and the incidence of hospitalization during this period because of acute respiratory infection (ARI) was recorded.

RESULTS

Of the 508 patients, 212 had taken oral VDRA at the start of the study, whereas 296 patients had not received it. During the 5-year follow-up period, 57 patients were hospitalized because of ARIs. Kaplan-Meier analysis revealed that the incidence of hospitalization because of respiratory infection was significantly lower in patients who had been treated with VDRA compared with patients who had not (log rank test; P = 0.02). The multivariate Cox proportional hazards model demonstrated that the patients who had taken oral VDRA were at a significantly lower risk of hospitalization because of respiratory disease (hazard ratio 0.47, 95% confidence interval 0.25 to 0.90).

CONCLUSIONS

The findings of this study suggest that the administration of oral VDRA has a preventive effect on the incidence of ARIs in dialysis patients.

Advanced glycation end products, carotid atherosclerosis, and circulating endothelial progenitor cells in patients with end-stage renal disease

Numbers of endothelial progenitor cells (EPCs) have been shown to be decreased in subjects with end-stage renal disease (ESRD), the mechanism of which remained poorly understood. In this study, mutual association among circulating EPC levels, carotid atherosclerosis, serum pentosidine, and skin autofluorescence, a recently established noninvasive measure of advanced glycation end products accumulation, was examined in 212 ESRD subjects undergoing hemodialysis. Numbers of circulating EPCs were measured as CD34+ CD133+ CD45(low) VEGFR2+ cells and progenitor cells as CD34+ CD133+ CD45(low) fraction by flow cytometry. Skin autofluorescence was assessed by the autofluorescence reader; and serum pentosidine, by enzyme-linked immunosorbent assay. Carotid atherosclerosis was determined as intimal-medial thickness (IMT) measured by ultrasound. Circulating EPCs were significantly and inversely correlated with skin autofluorescence in ESRD subjects (R = -0.216, P = .002), but not with serum pentosidine (R = -0.079, P = .25). Circulating EPCs tended to be inversely associated with IMT (R = -0.125, P = .069). Intimal-medial thickness was also tended to be correlated positively with skin autofluorescence (R = 0.133, P = .054) and significantly with serum pentosidine (R = 0.159, P = .019). Stepwise multiple regression analyses reveal that skin autofluorescence, but not serum pentosidine and IMT, was independently associated with low circulating EPCs. Of note, skin autofluorescence was also inversely and independently associated with circulating progenitor cells. Thus, tissue accumulated, but not circulating, advanced glycation end products may be a determinant of a decrease in circulating EPCs in ESRD subjects.

Association of serum TRAIL levels with atherosclerosis in patients with type 2 diabetes mellitus

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) was originally isolated as an inducer of apoptosis. Recent cross-sectional and prospective studies suggest an inverse association of serum TRAIL levels with the severity of coronary artery disease (CAD) and with an adverse outcome in patients with CAD or heart failure. However, it is unknown whether TRAIL can inversely reflect the progression of atherosclerosis from its early stage. We therefore examined the association between TRAIL measured by ELISA and intima-media thickness (IMT) in carotid and femoral arteries evaluated by ultrasonography as a surrogate marker of atherosclerosis in 416 type 2 diabetic patients without any symptoms of CAD and heart failure. Concurrently, the existence of calcified plaque (CP) was examined. There was no significant association between TRAIL and carotid IMT (ρ=-0.096, p=0.052) or femoral IMT (ρ=-0.025, p=0.610), although TRAIL was associated with carotid IMT in a subset of patients with macrovascular diseases (ρ=-0.174, p=0.034). No difference in TRAIL levels was found between two groups with or without CP. TRAIL may not be a good candidate as a biomarker to evaluate early-stage atherosclerotic lesions.

Different effects of diabetic autonomic neuropathy on regional transcutaneous oxygen tension in patients with peripheral arterial disease

BACKGROUND

Diabetic autonomic neuropathy (DAN) is thought to reduce skin nutritive perfusion through increase of arteriovenous shunting flow, resulting in foot ulceration. However, the correlation between skin tissue oxygenation and DAN has not been fully elucidated. Transcutaneous oxygen tension (TcPO2) is a reliable indicator of skin nutritional microcirculation. The aim of this study was to evaluate the influence of DAN on skin microcirculation by using TcPO2 measurements.

METHODS

The resting TcPO2 (REST-TcPO2) and post-exercise TcPO2 (Ex-TcPO2) of the calf and dorsalis pedis regions were measured simultaneously in 52 patients (104 limbs), including 41 diabetes patients. All patients underwent angiography, and the presence of arterial stenosis was evaluated.

RESULTS

TcPO2 levels were compared among the groups of patients with no neuropathy, sensory neuropathy alone, and DAN. In both the calf and dorsalis pedis regions, Ex-TcPO2 levels in diabetes patients with DAN were significantly lower than those in diabetes patients without any neuropathy. However, there was no difference in REST-TcPO2 levels among these groups. We then performed multiple regression analysis to evaluate the influence of DAN on each TcPO2 after adjustment for multiple clinical factors. DAN was a significant determinant of REST- and Ex-TcPO2 in the calf region, and it was independent of arterial stenosis and sensory neuropathy. In contrast, DAN was not an independent determinant of REST- and Ex-TcPO2 in the dorsalis pedis region.

CONCLUSIONS

We, for the first time, showed that DAN has significant effects on skin microcirculation of the calf region but not of the dorsalis pedis region.

Fetuin-A and atherosclerotic calcified plaque in patients with type 2 diabetes mellitus

Fetuin-A is a multifunctional circulating glycoprotein. Among its roles, inhibition of ectopic calcification is a prominent feature. Low fetuin-A levels in dialysis patients are associated with cardiovascular mortality, possibly via accelerating vascular calcification. However, except for dialyzed conditions, a correlation between fetuin-A levels and vascular calcification remains controversial. Furthermore, any inhibitory effect of fetuin-A on atherosclerotic calcified plaques (CPs) remains unclear compared with its effect on medial artery calcification that is often found in dialyzed patients. Therefore, we examined the association between fetuin-A levels and atherosclerotic CPs. For this study, 416 consecutive patients with type 2 diabetes mellitus and without renal dysfunction were examined. We measured serum fetuin-A levels and investigated for the presence of CP in the common carotid and femoral arteries using ultrasonography. Fetuin-A levels were significantly lower in patients with CP than those without CP (262.6 +/- 56.7 and 281.5 +/- 64.6 microg/mL, respectively; P = .001). Multivariate logistic regression analysis showed that fetuin-A levels were inversely associated with the presence of CP (odds ratio = 0.753; 95% confidence interval, 0.608-0.933; P = .010). These results suggest that fetuin-A may inhibit the calcification of atherosclerotic plaques independently of the dialyzed condition.

Brachial-ankle pulse wave velocity as an index of central arterial stiffness

AIM

Stiffness of the central arteries plays an important role in the pathophysiology of cardiovascular disease, and pulse wave velocity (PWV) of the aorta has been used as the standard measure of central arterial stiffness. An automated device for brachial-ankle (ba) PWV is available, although information is limited whether baPWV reflects the stiffness of central or peripheral arteries. We therefore addressed this question in the present study.

METHODS

The subjects were 2,806 consecutive participants in our non-invasive vascular laboratory, excluding those with an ankle-brachial index (ABI) lower than 0.95. PWV measurements were simultaneously performed using an automated device for the ba, heart-femoral (hf, aorta), heart-carotid (hc), heart-brachial (hb), and femoral-ankle (fa) segments. Correlational analyses were performed (1) among these PWV values, (2) between PWV and individual risk factors, and (3) between PWV and the Framingham risk score (FRS), a surrogate index for integrated cardiovascular risk.

RESULTS

The correlation of baPWV was the highest with hfPWV (r=0.796) and the lowest with hcPWV (r=0.541). Among the known factors preferentially affecting central arterial stiffness, higher age, diabetes mellitus, and chronic kidney disease (CKD) were also closely associated with increased baPWV. Finally, FRS was more closely correlated with hfPWV (r=0.613) and baPWV (r=0.609) than with hbPWV (r=0.523), hcPWV (r=0.509), and faPWV (r=0.393).

CONCLUSION

These results indicate that baPWV is an index of arterial stiffness showing similar characteristics to those of aortic PWV.

Serum C-reactive protein and thioredoxin levels in subjects with mildly reduced glomerular filtration rate

Background

Chronic kidney disease (CKD) is a newly recognized high-risk condition for cardiovascular disease (CVD), and previous studies reported the changes in inflammation and oxidative stress in advanced stages of CKD. We compared the levels of serum biomarkers for inflammation and oxidative stress between subjects with normal and mildly reduced glomerular filtration rate (GFR).

Methods

The subjects were 182 participants of a health check-up program including those with normal (≥ 90 mL/min/1.73 m², N = 79) and mildly reduced eGFR (60-89 mL/min/1.73 m², N = 103) which was calculated based on serum creatinine, age and sex. We excluded those with reduced eGFR < 60 mL/min/1.73 m². No one had proteinuria. We measured serum levels of C-reactive protein (CRP) and thioredoxin (TRX) as the markers of inflammation and oxidative stress, respectively.

Results

As compared with subjects with normal eGFR, those with mildly reduced eGFR had increased levels of both CRP and TRX. Also, eGFR was inversely correlated with these biomarkers. The associations of eGFR with these biomarkers remained significant after adjustment for age and sex. When adjustment was done for eight possible confounders, CRP showed significant association with systolic blood pressure, high density lipoprotein cholesterol (HDL-C) and non-HDL-C, whereas TRX was associated with sex significantly, and with eGFR and systolic blood pressure at borderline significance.

Conclusions

We showed the increased levels of CRP and TRX in subjects with mildly reduced eGFR. The eGFR-CRP link and the eGFR-TRX link appeared to be mediated, at least partly, by the alterations in blood pressure and plasma lipids in these subjects.

Association of glycated albumin, but not glycated hemoglobin, with calcaneus quantitative ultrasound in male hemodialysis patients with type 2 diabetes mellitus

Sustained high glucose impairs bone metabolism in patients with type 2 diabetes mellitus (T2DM). In this study, the relationship between glycemic control and bone metabolism was examined in male hemodialysis (HD) patients with T2DM. To avoid the effect of menstruation and the menstrual cycle, obesity, and glycosuria-induced hypercalciuria on bone metabolism, male anuric nonobese HD patients with T2DM (n = 42) were enrolled. Calcaneus stiffness index (SI) was determined using ultrasound after HD session. Casual plasma glucose (PG), glycated hemoglobin (HbA(1c)), and glycated albumin (GA) were measured before the HD session. In simple regression analysis, log PG (r = -0.333, P < .05) and log GA (r = -0.350, P < .05), but not log HbA(1c) (r = -0.134, P = .3985), exhibited significant and negative correlations with calcaneus SI. In multiple regression analysis including log BMI, log cCa x Pi product, and log PG, log PG was associated significantly in a negative manner with calcaneus SI, in addition to log cCa x Pi product. When log PG was replaced with log GA or log HbA(1c), log GA, but not log HbA(1c), emerged as a significant factor associated. The mechanism as to why HbA(1c) failed to associate could be explained by its false reduction by erythropoietin injection. The present study supported the notion of GA as an appropriate indicator for glycemic control in HD patients with T2DM. Furthermore, it is suggested that poor glycemic control might be a significant factor toward decreasing calcaneus SI in T2DM HD patients.

Neuropsychological status of elderly patients with diabetes mellitus

AIM

Diabetes mellitus (DM) is an important risk factor for Alzheimer's disease (AD) but the relationship between DM and amnestic mild cognitive impairment (aMCI), characterized by isolated memory loss, is unclear. We studied the prevalence of MCI in DM patients.

METHODS

Neuropsychological status was evaluated using the Rivermead Behavioral Memory Test (RBMT) and the Mini Mental State Examination (MMSE). Subjects consisted of 103 consecutive diabetic patients hospitalized for diabetic education. Patients with severe diabetic complications or cerebrovascular accidents were excluded.

RESULTS

Neuropsychological evaluation of DM patients showed that 71% were normal (MMSE score > or =24 and RBMT score > or =15), 5% had amnestic MCI (aMCI) (MMSE score > or =24 and RBMT score <15) and the remaining 23% had dementia (MMSE score <24). The percentage of patients with dementia was significantly higher in the DM group than in the control group (p<0.04). RBMT score and HbA1c were mildly correlated in diabetic patients.

CONCLUSION

High blood sugar may cause deterioration in not only memory function but also other cognitive domains in elderly patients with DM. Monitoring the neuropsychological status of this patient population is important.

Association of serum TRAIL level with coronary artery disease

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF ligand family, and is able to induce apoptosis in tumor cells. Emerging experimental findings suggest the involvement of TRAIL in vascular biology and atherosclerosis. However, little is known concerning the role of TRAIL in atherosclerosis in humans. We therefore examined whether serum TRAIL levels are associated with coronary artery disease (CAD). Serum TRAIL levels were measured by ELISA in 285 patients who underwent coronary angiography. Serum TRAIL level was significantly lower in patients with CAD (659.2+/-176.6 pg/ml) than in those without CAD (732.3+/-187.9 pg/ml, p=0.0016). Next, the number of diseased vessels was used to represent the severity of CAD. Serum TRAIL levels were inversely associated with the severity of CAD (p for trend=0.0005). In particular, TRAIL levels in patients with severe 3-vessel disease were significantly lower than those in subjects without CAD (602.9+/-150.0, 732.3+/-187.9 pg/ml, respectively; p<0.05). Multivariable logistic regression analysis revealed that serum TRAIL levels were significantly associated with the presence of CAD (odds ratio, 0.68; 95% confidence interval 0.51-0.90; p=0.006). Serum TRAIL levels were inversely associated with the advanced CAD, suggesting that TRAIL may be useful as a biomarker of CAD severity.