Effect of osteoporosis on bone mineral density and fracture repair in a rat femoral fracture model

Osteoporosis (OP) is one of the most prevalent bone diseases worldwide with bone fracture the major clinical consequence. The effect of OP on fracture repair is disputed and although it might be expected for fracture repair to be delayed in osteoporotic individuals, a definitive answer to this question still eludes us. The aim of this study was to clarify the effect of osteoporosis in a rodent fracture model. OP was induced in 3-month-old rats (n = 53) by ovariectomy (OVX) followed by an externally fixated, mid-diaphyseal femoral osteotomy at 6 months (OVX group). A further 40 animals underwent a fracture at 6 months (control group). Animals were sacrificed at 1, 2, 4, 6, and 8 weeks postfracture with outcome measures of histology, biomechanical strength testing, pQCT, relative BMD, and motion detection. OVX animals had significantly lower BMD, slower fracture repair (histologically), reduced stiffness in the fractured femora (8 weeks) and strength in the contralateral femora (6 and 8 weeks), increased body weight, and decreased motion. This study has demonstrated that OVX is associated with decrease in BMD (particularly in trabecular bone) and a reduction in the mechanical properties of intact bone and healing fractures. The histological, biomechanical, and radiological measures of union suggest that OVX delayed fracture healing. (C) 2007 Orthopaedic Research Society. Published by Wiley Periodicals.

Advanced glycation end products accumulate in the reproductive tract of men with diabetes

Light microscopic studies comparing sperm parameters show little association between diabetes and male fertility. However, with the introduction of new analytical techniques, evidence is now emerging of previously undetectable effects of diabetes on sperm function. Specifically, a recent study has found a significantly higher sperm nuclear DNA fragmentation in diabetic men. As advanced glycation end products (AGEs) are important instigators of oxidative stress and cell dysfunction in numerous diabetic complications, we hypothesized that these compounds could also be present in the male reproductive tract. The presence and localization of the most prominent AGE, carboxymethyl-lysine (CML), in the human testis, epididymis and sperm was determined by immunohistochemistry. Parallel ELISA and Western blot analyses were performed to ascertain the amount of CML in seminal plasma and sperm from 13 diabetic and nine non-diabetic subjects. CML immunoreactivity was found throughout the seminiferous epithelium, the nuclei of spermatogonia and spermatocytes, in the basal and principle cells cytoplasm and nuclei of the caput epididymis and on most sperm tails, mid pieces and all cytoplasmic droplets. The acrosomal cap, especially the equatorial band, was prominently stained in diabetic samples only. The amount of CML was significantly higher (p = 0.004) in sperm from non-diabetic men. Considering the known detrimental actions of AGEs in other organs, the presence, location and quantity of CML, particularly the increased expression found in diabetic men, suggest that these compounds may play a hitherto unrecognized role in male infertility.

Advanced glycation of fibronectin impairs vascular repair by endothelial progenitor cells: Implications for vasodegeneration in diabetic retinopathy

PURPOSE. Vascular repair by marrow-derived endothelial progenitor cells (EPCs) is impaired during diabetes, although the precise mechanism of this dysfunction remains unknown. The hypothesis for the study was that progressive basement membrane (BM) modification by advanced glycation end products (AGEs) contributes to impairment of EPC reparative function after diabetes-related endothelial injury.

METHODS. EPCs isolated from peripheral blood were characterized by immunocytochemistry and flow cytometry. EPC interactions on native or AGE-modified fibronectin (AGE-FN) were studied for attachment and spreading, whereas chemotaxis to SDF-1 was assessed with the Dunn chamber assay. In addition, photoreactive agent-treated monolayers of retinal microvascular endothelial cells (RMECs) produced circumscribed areas of apoptosis and the ability of EPCs to “endothelialize” these wounds was evaluated.

RESULTS. EPC attachment and spreading on AGE-FN was reduced compared with control cells (P < 0.05–0.01) but was significantly restored by pretreatment with Arg-Gly-Asp (RGD). Chemotaxis of EPCs was abolished on AGE-FN but was reversed by treatment with exogenous RGD. On wounded RMEC monolayers, EPCs showed clustering at the wound site, compared with untreated regions (P < 0.001); AGE-FN significantly reduced this targeting response (P < 0.05). RGD supplementation enhanced EPC incorporation in the monolayer, as determined by EPC participation in tight junction formation and restoration of transendothelial electric resistance (TEER).

CONCLUSIONS. AGE-modification of vascular substrates impairs EPC adhesion, spreading, and migration; and alteration of the RGD integrin recognition motif plays a key role in these responses. The presence of AGE adducts on BM compromises repair by EPC with implications for vasodegeneration during diabetic microvasculopathy.

Development of composite tissue scaffolds containing naturally sourced mircoporous hydroxyapatite

The aims of this work were to investigate the conversion of a marine alga into hydroxyapatite (HA), and furthermore to design a composite bone tissue engineering scaffold comprising the synthesised HA within a porous bioresorbable polymer. The marine alga Phymatolithon calcareum, which exhibits a calcium carbonate honeycomb structure, with a natural architecture of interconnecting permeable pores (microporosity 4-11 mu m), provided the initial raw material for this study. The objective was to convert the alga into hydroxyapatite while maintaining its porous morphology using a sequential pyrolysis and chemical synthesis processes. Semi-quantitative XRD analysis of the post-hydrothermal material (pyrolised at 700-750 degrees C), indicated that the calcium phosphate (CaP) ceramic most likely consisted of a calcium carbonate macroporous lattice, with hydroxyapatite crystals on the surface of the macropores. Cell visibility (cytotoxicity) investigations of osteogenic cells were conducted on the CaP ceramic (i.e., the material post-hydrothermal analysis) which was found to be non-cytotoxic and displayed good biocompatibility when seeded with MG63 cells. Furthermore, a hot press scaffold fabrication technique was developed to produce a composite scaffold of CaP (derived from the marine alga) in a polycaprolactone (PCL) matrix. A salt leaching technique was further explored to introduce macroporosity to the structure (50-200 mu m). Analysis indicated that the scaffold contained both micro/macroporosity and mechanical strength, considered necessary for bone tissue engineering applications. (C) 2008 Published by Elsevier B.V.