Urine analysis of glucose tetrasaccharide by HPLC; a useful marker for the investigation of patients with Pompe and other glycogen storage diseases.

A high performance liquid chromatography method, adapted from an established urinary sugars method, has been developed for the analysis of a tetraglucose oligomer (Glc(4)) in urine. Pompe disease results from defects in the activity of lysosomal acid α-glucosidase (GAA) with patients typically excreting increased amounts of Glc(4). Rapid determination of GAA in dried blood spots is now possible. However, enzymatic analysis is unable to discriminate between patients with Pompe disease and those individuals harbouring pseudo deficiency mutations. This method was able to quantify Glc(4) levels in all patients analysed with an established diagnosis of Pompe disease, and all controls analysed had Glc(4) levels below the limit of detection for this method. Importantly the method was able to discriminate between an individual known to harbour a pseudo Pompe mutation and patients with Pompe disease, providing a useful supporting test to enzymatic analysis. Sequential measurement of urinary Glc(4) has been proposed to monitor the effects of enzyme replacement therapy (ERT). We observed a clear decrease in Glc(4) levels following commencement of treatment in three patients studied. Additionally, raised levels of Glc(4) were observed in patients with glycogen storage disease (GSD) type Ia and type III suggesting that this method may have applications in other GSDs.

Angiogenesis and nerve growth factor at the osteochondral junction in rheumatoid arthritis and osteoarthritis.

Objectives. The osteochondral junction can be a source of pain in both RA and OA. Growth of blood vessels and nerves from the subchondral bone into articular cartilage may mediate the association between joint pathology and symptoms. We have investigated associations between angiogenesis, inflammation and neurovascular growth factor expression at the osteochondral junction in human arthritis. Methods. Osteochondral junctions from medial tibial plateaux of patients undergoing arthroplasty for RA (n = 10) or OA (n = 11), or from non-arthritic post-mortem controls (n = 11) were characterized by immunohistochemistry for CD34 and smooth muscle α-actin (blood vessels), CD68 (macrophages), CD3 (lymphocytes), proliferating cell nuclear antigen, vascular endothelial, platelet-derived and nerve growth factor (NGF). Results. Osteochondral angiogenesis was demonstrated as increased endothelial cell proliferation and vascular density in non-calcified articular cartilage, both in RA and OA. Osteochondral angiogenesis was associated with subchondral bone marrow replacement by fibrovascular tissue expressing VEGF, and with increased NGF expression within vascular channels. RA was characterized by greater lymphocyte infiltration and PDGF expression than OA, whereas chondrocyte expression of VEGF was a particular feature of OA. NGF was observed in vascular channels that contained calcitonin gene-related peptide-immunoreactive sensory nerve fibres. Conclusions. Osteochondral angiogenesis in RA and OA is associated with growth factor expression by cells within subchondral spaces, vascular channels and by chondrocytes. NGF expression and sensory nerve growth may link osteochondral angiogenesis to pain in arthritis.