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Isolation and characterisation of a hyaluronan binding protein, hyaluronectin, from human placenta and its colocalisation with hyaluronan.Ponting, Julie M; Kumar, Shant; Department of Clinical Research, Christie Hospital, Manchester, UK. (1995-02)Hyaluronan (HA) is a major component of the extracellular matrix and is known to influence cell behaviour and to play a role in angiogenesis, morphogenesis and tissue remodelling, although little is known concerning the regulation of these effects. Until now its detection in the placenta has been by indirect methods, which has led to conflicting conclusions as to its distribution and hence its role. Hyaluronectin (HN) is one of a group of proteins with HA binding ability which may regulate the effects of HA. Although nervous tissue HN has been partly characterised with regard to its distribution, structure and biochemistry, little is known about the mesenchymal isoform and its distribution in placenta has not previously been reported. Using specific probes we have characterised the distribution of HA and HN in human placental tissue. At all stages of development studied (8, 10, 12, 30 and 38 wk gestation) HA and HN were unequivocally colocalised, being distributed in the extracellular matrix of stromal tissue of placental villi, chorioallantoic membranes and umbilical cord. Particularly strong immunoreactivity was observed in the villous stroma immediately adjacent to fibrinoid depositions at sites of denudation of the trophoblast layer. Extraction and characterisation of the HN from placental villi have revealed 4 major glycoproteins of 47, 52, 57 and 67 kDa, this being a different pattern and smaller molecular range than observed for the nervous tissue form. This is the first direct demonstration of the presence of HA and HN in the placenta and identifies an abundant new source of mesenchymal HN. The functions of mesenchymal HN are unknown but may include ion exchange, immunosuppression and regulation of the effects of HA in such roles as maintenance of tissue architecture, cell migration and angiogenesis.
Localisation and cellular origin of hyaluronectin.Ponting, Julie M; Kumar, Shant; Department of Clinical Research, Christie Hospital, Manchester, UK. (1995-10)Hyaluronectin is an extracellular matrix glycoprotein which specifically binds to hyaluronan. Isoforms of hyaluronectin are present in nervous and mesenchymal tissues but, while the nervous tissue isoform has been characterised in some detail, less is known about the mesenchymal isoform. Although its tissue localisation suggests a role in tumour development, neither its cellular origin nor its exact function are known. In this study we demonstrate hyaluronectin synthesis in fibroblasts and smooth muscle cells in vitro. The pattern of immunolocalisation of hyaluronectin in fibroblasts depended on the cell type, length of time spent by the cells in culture and cell density. Immunoreactivity in sparsely plated migratory cells was seen mainly in a patchy distribution at the attached cell surface and in the migration tracks left by the cells on the subtratum. In stationary cells a more uniform distribution associated with the attached cell surface was observed, while in confluent cultures hyaluronectin immunoreactivity was mainly seen as a network of fibrillar material above the cell. The pattern of staining was distinct from that of other hyaluronan-binding proteins. Immunoprecipitation, using antihyaluronectin antibodies, of the substratum-attached material deposited by human fetal fibroblasts revealed a family of proteins ranging from 22 to 90 kDa, the major protein being of approximately 60 kDa. These results lead us to propose that hyaluronectin plays an important role in cell migration, probably by regulation of hyaluronan distribution and binding.
Sera of children with renal tumours contain low-molecular-mass hyaluronic acid.Kumar, Shant; West, David C; Ponting, Julie M; Gattamaneni, Rao; Christie Hospital, Manchester, UK. (1989-09-15)The molecular mass of hyaluronic acid (HA) rather than its serum concentration alone may be a hallmark of certain types of malignancy. A radiometric assay was used to measure HA levels in 35 children with renal tumours [33 Wilms' tumours and 2 bone metastasizing renal tumours of childhood (BMRTC)] and 20 normal siblings of children with cancer. The HA level in the sera of normal children was barely detectable and had a molecular mass of 1-5 x 10(5). In both Wilms' and BMRTC patients, very high levels of HA were found in preoperative serum samples; these fell dramatically following surgical excision of the tumours. A novel finding of our study was the presence of low-molecular-mass HA (similar to the angiogenic fragments of HA) in the sera of BMRTC patients. In contrast, high-molecular-mass HA (which is not angiogenic) was found in the sera of Wilms' patients (2 x 10(6) kDa). Following surgery in BMRTC patients, not only did serum HA levels fall to a value within normal ranges, but also the HA which remained was of high molecular mass.