Biomedical subjects

Pamela Gehron Robey

Publications and source records attributed to Pamela Gehron Robey.

25 records · Page 2Linked to original sources

PubMed2002

Age-related changes in human bone proteoglycan structure. Impact of osteogenesis imperfecta.

Proteoglycans (PGs) are a family of molecules that undergo extensive post-translational modifications that include addition of glycosaminoglycan (GAG) chains as well as N- and O-linked oligosaccharides to the protein core. PG composition and structure have been reported to alter with age. To test whether the post-translational modifications to PGs can serve as in vitro surrogate end point markers for chronological age, the extent of GAG modifications was determined for PGs derived from normal human bone cells of 14 donors (age range, fetal to 60 years). Isolated cells were steady state radiolabeled with (35)SO(4)(2-) and [(3)H]GlcN. For biglycan and decorin, iduronate content was linearly correlated with age (increased 1.5x between fetal and age 60 years). For the syndecan-like heparan sulfate PG, the N-sulfation of post-natal cells increased over 3.5-fold until reaching a plateau during the 4th decade of life. The amount of O-linked oligosaccharides was also found to decrease as a function of increasing normal donor age, whereas the specific activity of the metabolic precursor pool remained constant regardless of donor age. These age-related changes in post-translational modifications were then used to demonstrate that osteoblasts derived from patients with osteogenesis imperfecta did not exhibit facets of a pre-mature aging, but rather were arrested in a fetal-like phenotypic state. A growth matrix rich in thrombospondin altered PG metabolism in osteoblastic cells, resulting in the production and secretion of the fetal-like (rich in O-linked oligosaccharides) forms of decorin and biglycan. This effect was qualitatively different from the effect of transforming growth factor-beta, which predominantly altered GAGs rather than O-linked oligosaccharides. No other Arg-Gly-Asp protein (fibronectin, vitronectin, type I collagen, osteopontin, and bone sialoprotein) showed any detectable effect on PG metabolism in bone cells. These results indicate that a proper matrix stoichiometry is critical for metabolism of PGs.

Adolescent↗

PubMed2002

Ribbing disease: radiographic and biochemical characterization, lack of response to pamidronate.

Ribbing disease is a rare form of sclerosing dysplasia characterized by benign endosteal and periosteal bone growth confined to the diaphyses of the long bones, usually the tibiae and femora. The onset is usually after puberty and the most common presentation is pain that is usually self-limited, but may progress. The etiology and optimal treatment for the disease are unknown. We present the case of a 39-year-old Hispanic man with clinical and radiological manifestations of Ribbing disease. Radiographs and CT imaging demonstrated typical cortical thickening in the mid-diaphyses of the tibiae bilaterally that correlated with intense tracer uptake on (99m)Tc-MDP bone scans. MRI demonstrated cortical thickening and abnormal marrow signal consistent with marrow edema. Bone marrow edema may explain the pain frequently associated with the disease. Multiple serum and urine markers of bone metabolism were within normal limits. In an effort to ameliorate pain, the patient was treated with the bisphosphonate, pamidronate. In spite of treatment, pain increased, requiring additional and larger doses of analgesics. Serial radiographs, CT, bone scans, and MRI all demonstrated disease progression with pamidronate treatment. In this report we present for the first time the finding of bone marrow edema with MRI as well as disease progression during intravenous pamidronate treatment.

Adult↗

PubMed2002

Gene expression profile of human bone marrow stromal cells: high-throughput expressed sequence tag sequencing analysis.

Human bone marrow stromal cells (HBMSC) are pluripotent cells with the potential to differentiate into osteoblasts, chondrocytes, myelosupportive stroma, and marrow adipocytes. We used high-throughput DNA sequencing analysis to generate 4258 single-pass sequencing reactions (known as expressed sequence tags, or ESTs) obtained from the 5' (97) and 3' (4161) ends of human cDNA clones from a HBMSC cDNA library. Our goal was to obtain tag sequences from the maximum number of possible genes and to deposit them in the publicly accessible database for ESTs (dbEST of the National Center for Biotechnology Information). Comparisons of our EST sequencing data with nonredundant human mRNA and protein databases showed that the ESTs represent 1860 gene clusters. The EST sequencing data analysis showed 60 novel genes found only in this cDNA library after BLAST analysis against 3.0 million ESTs in NCBI's dbEST database. The BLAST search also showed the identified ESTs that have close homology to known genes, which suggests that these may be newly recognized members of known gene families. The gene expression profile of this cell type is revealed by analyzing both the frequency with which a message is encountered and the functional categorization of expressed sequences. Comparing an EST sequence with the human genomic sequence database enables assignment of an EST to a specific chromosomal region (a process called digital gene localization) and often enables immediate partial determination of intron/exon boundaries within the genomic structure. It is expected that high-throughput EST sequencing and data mining analysis will greatly promote our understanding of gene expression in these cells and of growth and development of the skeleton.

Bone Marrow Cells↗

PubMed2002

Characterization of gsp-mediated growth hormone excess in the context of McCune-Albright syndrome.

McCune-Albright syndrome (MAS) is a disorder characterized by the triad of café-au-lait skin pigmentation, polyostotic fibrous dysplasia of bone, and hyperfunctioning endocrinopathies, including GH excess. The molecular etiology of the disease is postzygotic activating mutations of the GNAS1 gene product, G(s)alpha. The term gsp oncogene has been assigned to these mutations due to their association with certain neoplasms. The aim of this study was to estimate the prevalence of GH excess in MAS, characterize the clinical and endocrine manifestations, and describe the response to treatment. Fifty-eight patients with MAS were screened, and 22 with stigmata of acromegaly and/or elevated GH or IGF-I underwent oral glucose tolerance testing. Twelve patients (21%) had GH excess, based on failure to suppress serum GH on oral glucose tolerance test, and underwent a TRH test, serial GH sampling from 2000-0800 h, and magnetic resonance imaging of the sella. We found that vision and hearing deficits were more common in patients with GH excess (4 of 12, 33%) than those without (2 of 56, 4%). Of interest, patients with a history of precocious puberty and GH excess who had reached skeletal maturity achieved normal adult height despite a history of early epiphyseal fusion. All 9 patients tested had an increase in serum GH after TRH, 11 of 12 (92%) had hyperprolactinemia, and all 8 tested had detectable or elevated nighttime GH levels. Pituitary adenoma was detected in 4 of 12 (33%) patients. All patients with elevated IGF-I levels were treated with cabergoline (7 patients), long-acting octreotide (LAO; 8 patients), or a combination of cabergoline and LAO (4 patients). In six of the seven patients (86%) treated with cabergoline, serum IGF-I decreased, but not to the normal range. In the eight patients treated with LAO alone, IGF-I decreased, and, in four, returned to the normal range. The remaining 4 patients were treated with a combination of cabergoline and LAO. For them, symptoms of GH excess diminished, and IGF-I decreased further, but did not enter the normal range. GH excess is common in MAS and results in a distinct clinical phenotype characterized by inappropriately normal stature, TRH responsiveness, prolactin cosecretion, small or absent pituitary tumors, a consistent but inadequate response to treatment with cabergoline, and an intermediate response to LAO.

Adenoma↗

PubMed2002

Age-related osteoporosis in biglycan-deficient mice is related to defects in bone marrow stromal cells.

Biglycan (bgn) is an extracellular matrix proteoglycan that is enriched in bone and other skeletal connective tissues. Previously, we generated bgn-deficient mice and showed that they developed age-dependent osteopenia. To identify the cellular events that might contribute to this progressive osteoporosis, we measured the number of osteogenic precursors in the bone marrow of normal and mutant mice. The number of colonies, indicative of the colony-forming unit potential of fibroblasts (CFU-F), gradually decreased with age. By 24 weeks of age, colony formation in the bgn knockout (KO) mice was significantly more reduced than that in the wild type (wt) mice. This age-related reduction was consistent with the extensive osteopenia previously shown by X-ray analysis and histological examination of 24-week-old bgn KO mice. Because bgn has been shown previously to bind and regulate transforming growth factor beta (TGF-beta) activity, we also asked whether this growth factor would affect colony formation. TGF-beta treatment significantly increased the size of the wt colonies. In contrast, TGF-beta did not significantly influence the size of the bgn colonies. An increase in apoptosis in bgn-deficient bone marrow stromal cells (BMSCs) was observed also. The combination of decreased proliferation and increased apoptosis, if it occurred in vivo, would lead to a deficiency in the generation of mature osteoblasts and would be sufficient to account for the osteopenia developed in the bgn KO mice. The bgn KO mice also were defective in the synthesis of type I collagen messenger RNA (mRNA) and protein. This result supports the suggestion that the composition of the extracellular matrix may be regulated by specific matrix components including bgn.

Animals↗

PubMed2002

Dental and skeletal stem cells: potential cellular therapeutics for craniofacial regeneration.

The study of stem cells has received considerable attention since the discovery that adult stem cells have the capacity to form many different tissue types. Technical advances have helped identify potential stem cells, and their capacity for regenerating tissues is being studied in transplantation models. Further study of the isolation, nature, and differentiation potential of stem cells will likely have a positive impact on our understanding of human development and regenerative medicine. This review highlights the difference between embryonic and adult stem cells and discusses the potential use of these cells for cellular therapeutics for craniofacial regeneration.

Adult↗

PubMedDate not supplied

Investigation of multipotent postnatal stem cells from human periodontal ligament.

BACKGROUND: Periodontal diseases that lead to the destruction of periodontal tissues--including periodontal ligament (PDL), cementum, and bone--are a major cause of tooth loss in adults and are a substantial public-health burden worldwide. PDL is a specialised connective tissue that connects cementum and alveolar bone to maintain and support teeth in situ and preserve tissue homoeostasis. We investigated the notion that human PDL contains stem cells that could be used to regenerate periodontal tissue. METHODS: PDL tissue was obtained from 25 surgically extracted human third molars and used to isolate PDL stem cells (PDLSCs) by single-colony selection and magnetic activated cell sorting. Immunohistochemical staining, RT-PCR, and northern and western blot analyses were used to identify putative stem-cell markers. Human PDLSCs were transplanted into immunocompromised mice (n=12) and rats (n=6) to assess capacity for tissue regeneration and periodontal repair. Findings PDLSCs expressed the mesenchymal stem-cell markers STRO-1 and CD146/MUC18. Under defined culture conditions, PDLSCs differentiated into cementoblast-like cells, adipocytes, and collagen-forming cells. When transplanted into immunocompromised rodents, PDLSCs showed the capacity to generate a cementum/PDL-like structure and contribute to periodontal tissue repair. INTERPRETATION: Our findings suggest that PDL contains stem cells that have the potential to generate cementum/PDL-like tissue in vivo. Transplantation of these cells, which can be obtained from an easily accessible tissue resource and expanded ex vivo, might hold promise as a therapeutic approach for reconstruction of tissues destroyed by periodontal diseases.

Adult↗