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Biomedical subjects

Stan Gronthos

Publications and source records attributed to Stan Gronthos.

At least 19 recordsLinked to original sources
PubMed2007

EphB/ephrin-B interaction mediates adult stem cell attachment, spreading, and migration: implications for dental tissue repair.

Human adult dental pulp stem cells (DPSCs) reside predominantly within the perivascular niche of dental pulp and are thought to originate from migrating neural crest cells during development. The Eph family of receptor tyrosine kinases and their ligands, the ephrin molecules, play an essential role in the migration of neural crest cells during development and stem cell niche maintenance. The present study examined the expression and function of the B-subclass Eph/ephrin molecules on DPSCs. Multiple receptors were primarily identified on DPSCs within the perivascular niche, whereas ephrin-B1 and ephrin-B3 were expressed by the surrounding pulp tissue. EphB/ephrin-B bidirectional signaling inhibited cell attachment and spreading, predominately via the mitogen-activated protein kinase (MAPK) pathway for forward signaling and phosphorylation of Src family tyrosine kinases via reverse ephrin-B signaling. DPSC migration was restricted through unidirectional ephrin-B1-activated EphB forward signaling, primarily signaling through the MAPK pathway. Furthermore, we observed that ephrin-B1 was downregulated in diseased adult teeth compared with paired uninjured controls. Collectively, these studies suggest that EphB/ephrin-B molecules play a role in restricting DPSC attachment and migration to maintain DPSCs within their stem cell niche under steady-state conditions. These results may have implications for dental pulp development and regeneration.

Adult↗
PubMed2006

Mesenchymal stem cell-mediated functional tooth regeneration in swine.

Mesenchymal stem cell-mediated tissue regeneration is a promising approach for regenerative medicine for a wide range of applications. Here we report a new population of stem cells isolated from the root apical papilla of human teeth (SCAP, stem cells from apical papilla). Using a minipig model, we transplanted both human SCAP and periodontal ligament stem cells (PDLSCs) to generate a root/periodontal complex capable of supporting a porcelain crown, resulting in normal tooth function. This work integrates a stem cell-mediated tissue regeneration strategy, engineered materials for structure, and current dental crown technologies. This hybridized tissue engineering approach led to recovery of tooth strength and appearance.

Animals↗
PubMed2006

Tumor angiogenesis is associated with plasma levels of stromal-derived factor-1alpha in patients with multiple myeloma.

PURPOSE: Multiple myeloma is an incurable hematologic malignancy characterized by increased bone marrow angiogenesis and extensive lytic bone disease. We have previously shown that elevated levels of stromal-derived factor-1alpha (SDF-1alpha) in peripheral blood plasma are associated with osteolysis in multiple myeloma patients. We have now examined whether SDF-1alpha levels also correlate with angiogenesis. EXPERIMENTAL DESIGN: We examined the contribution of multiple myeloma plasma cell-derived SDF-1alpha in the stimulation of in vitro angiogenesis using a tube formation assay. We also collected trephine and peripheral blood plasma samples from patients with multiple myeloma to analyze microvessel density and SDF-1alpha levels, respectively. RESULTS: We show that multiple myeloma plasma cell line-derived conditioned medium containing SDF-1alpha stimulates in vitro angiogenesis. In addition, in a large cohort of patients with multiple myeloma and its precursor condition monoclonal gammopathy of undetermined significance, we confirm previous findings that plasma cell burden correlates with both angiogenesis and plasma levels of SDF-1alpha. We now extend these observations and show the novel finding that peripheral blood plasma levels of SDF-1alpha positively correlate with the degree of bone marrow angiogenesis in multiple myeloma and monoclonal gammopathy of undetermined significance patients. CONCLUSIONS: High levels of SDF-1alpha produced by multiple myeloma plasma cells promote osteolysis and bone marrow angiogenesis. Therefore, we propose that inhibition of SDF-1alpha may be an effective mechanism by which angiogenesis and osteolysis can be reduced in multiple myeloma patients.

Adult↗
PubMed2006

Dental pulp stem cells.

Postnatal stem cells have been isolated from a variety of tissues. These stem cells are thought to possess great therapeutic potential for repairing damaged and/or defective tissues. Clinically, hematopoietic stem cells have been successfully used for decades in the treatment of various diseases and disorders. However, the therapeutic potential of other postnatal stem cell populations has yet to be realized, because of the lack of detailed understanding of their stem cell characteristics at the cellular and molecular levels. Furthermore, there is limited knowledge of their therapeutic value at the preclinical level. Therefore, it is necessary to develop optimal strategies and approaches to overcome the substantial challenges currently faced by researchers examining the clinical efficacy of different postnatal stem cell populations. In this review, we introduce methodologies for isolating postnatal stem cells from human dental pulp and discuss their potential role in tissue regeneration.

Animals↗
PubMed2006

Mesenchymal lineage precursor cells induce vascular network formation in ischemic myocardium.

Mesenchymal lineage precursors can be reproducibly isolated from adult mammalian bone marrow and grown in culture. Immunoselection with monoclonal antibodies against STRO-1 and vascular-cell-adhesion molecule 1 (VCAM1/CD106) prior to expansion results in a 1,000-fold enrichment of mesenchymal precursors compared to standard isolation techniques. Intramyocardial injection of human STRO-1-selected precursors in an athymic rat model of acute myocardial infarction results in induction of vascular network formation and arteriogenesis coupled with global functional cardiac recovery.

ADP-ribosyl Cyclase↗
PubMed2006

Mesenchymal stem cell-organized bone marrow elements: an alternative hematopoietic progenitor resource.

Bone marrow-derived mesenchymal stem cells (BMMSCs) are multipotent postnatal stem cells that have been used for the treatment of bone defects and graft-versus-host diseases in clinics. In this study, we found that subcutaneously transplanted human BMMSCs are capable of organizing hematopoietic progenitors of recipient origin. These hematopoietic cells expressed multiple lineages of hematopoietic cell associated markers and were able to rescue lethally irradiated mice, with successful engraftment in the recipient, suggesting a potential bone marrow (BM) resource for stem cell therapies. Furthermore, we found that platelet-derived growth factor (PDGF) promotes the formation of BMMSC-generated BM niches through upregulation of beta-catenin, implying that the PDGF pathway contributes to the formation of ectopic BM. These results indicate that the BMMSC-organized BM niche system represents a unique hematopoietic progenitor resource possessing potential clinical value.

Animals↗
PubMed2005

Defective osteogenesis of the stromal stem cells predisposes CD18-null mice to osteoporosis.

Osteogenesis by the bone marrow stromal stem cells (BMSSCs) supports continuous bone formation and the homeostasis of the bone marrow microenvironment. The mechanism that controls the proliferation and differentiation of BMSSCs is not fully understood. Here, we report that CD18, a surface protein present primarily on hematopoietic cells, but not on differentiated mesenchymal cells, is expressed by the stromal stem cells and plays a critical role in the osteogenic process. Constitutive expression of CD18 on BMSSCs using a retroviral promoter significantly enhances bone formation in vivo, whereas genetic inactivation of CD18 in mice leads to defective osteogenesis due to decreased expression of the osteogenic master regulator Runx2/Cbfa1. The defective osteogenesis of the CD18-null BMSSCs can be restored by expressing full-length, but not cytoplasmic domain-truncated, CD18. Radiographic analyses with dual-energy x-ray absorptiometry and 3D microcomputed tomography show that mice lacking CD18 have decreased bone mineral density and exhibit certain features of osteoporosis. Altogether, this work demonstrates that CD18 functions critically in the osteogenesis of BMSSCs, and thus lack of CD18 expression in the leukocyte adhesion deficiency patients may predispose them to osteoporosis.

Animals↗
PubMed2005

Elevated serum levels of stromal-derived factor-1alpha are associated with increased osteoclast activity and osteolytic bone disease in multiple myeloma patients.

Multiple myeloma (MM) is an incurable plasma cell (PC) malignancy able to mediate massive destruction of the axial and craniofacial skeleton. The aim of this study was to investigate the role of the potent chemokine, stromal-derived factor-1alpha (SDF-1alpha) in the recruitment of osteoclast precursors to the bone marrow. Our studies show that MM PC produce significant levels of SDF-1alpha protein and exhibit elevated plasma levels of SDF-1alpha when compared with normal, age-matched subjects. The level of SDF-1alpha positively correlated with the presence of multiple radiological bone lesions in individuals with MM, suggesting a potential role for SDF-1alpha in osteoclast precursor recruitment and activation. To examine this further, peripheral blood-derived CD14+ osteoclast precursors were cultured in an in vitro osteoclast-potentiating culture system in the presence of recombinant human SDF-1alpha. Although failing to stimulate an increase in TRAP+, multinucleated osteoclast formation, our studies show that SDF-1alpha mediated a dramatic increase in both the number and the size of the resorption lacunae formed. The increased osteoclast motility and activation in response to SDF-1alpha was associated with an increase in the expression of a number of osteoclast activation-related genes, including RANKL, RANK, TRAP, MMP-9, CA-II, and Cathepsin K. Importantly, the small-molecule CXCR4-specific inhibitor, 4F-Benzoyl-TE14011 (T140), effectively blocked osteoclast formation stimulated by the myeloma cell line, RPMI-8226. Based on these findings, we believe that the synthesis of high levels of SDF-1alpha by MM PC may serve to recruit osteoclast precursors to local sites within the bone marrow and enhance their motility and bone-resorbing activity. Therefore, we propose that inhibition of the CXCR4-SDF-1alpha axis may provide an effective means of treatment for MM-induced osteolysis.

Adult↗
PubMed2005

Stromal-derived factor-1 promotes the growth, survival, and development of human bone marrow stromal stem cells.

The maintenance of bone marrow stromal stem cells (BMSSCs) is tightly controlled by the local microenvironment and by autocrine regulatory factors secreted by BMSSCs. To identify such factors, a cDNA subtraction library was generated from purified BMSSCs, based on their high expression of the STRO-1 antigen. Stromal-derived factor-1 (SDF-1) was one differentially expressed gene highly expressed by purified BMSSCs prior to culture. In vitro, immature preosteogenic cells expressed greater levels of SDF-1 when compared with mature cell types representative of osteoblasts and osteocytes/bone lining cells. Furthermore, SDF-1 expression was rapidly down-regulated when BMSSCs were cultured under osteoinductive conditions. BMSSCs were also shown to express functional cell surface SDF-1 receptors (CXCR4). Transduced BMSSC lines, secreting high SDF-1 levels, displayed an enhanced ability to form ectopic bone in vivo, in comparison with control BMSSC lines. Moreover, high SDF-1-expressing BMSSCs displayed an increased capacity for cellular growth and protection against interleukin-4-induced apoptosis. Similarly, fibroblast colony-forming units (CFU-Fs) also displayed increased growth and resistance to alpha-interferon-2a-induced apoptosis, in synergy with platelet-derived growth factor BB (PDGF-BB) and SDF-1 in vitro. These studies indicate that the chemokine, SDF-1, may play a role in the maintenance, survival, and osteogenic capacity of immature BMSSC populations.

Adult↗
PubMed2005

Skeletal stem cells in regenerative medicine.

Postnatal stem cells have been isolated from a variety of tissues and they are highly expected to have potentiality to be utilized for cell-based clinical therapies. Bone marrow stromal stem cells (BMSSCs) derived from bone marrow stromal tissue have been identified as a population of multipotent mesenchymal stem cells that are capable of differentiating into osteoblasts, adipocytes, chondrocytes, muscle cells, and neural cells. The most significant tissue regeneration trait of BMSSCs is their in vivo bone regeneration capability, which has been widely studied for understanding molecular and cellular mechanisms of osteogenesis, and, more importantly, developing into a stem-cell-based therapy. Recent studies further demonstrated that BMSSC-mediated bone regeneration is a promising approach for regenerative medicine in clinical trials. However, there are some fundamental questions that remain to be answered prior to successful utilization of BMSSCs in clinical therapy. For instance, how to maintain stemness of BMSSCs will be a critical issue for developing methodologies to propagate multi-potential stem cells in vitro, in order to allow the development of effective clinical therapies.

Animals↗
PubMed2004

The nitrogen-containing bisphosphonate, zoledronic acid, increases mineralisation of human bone-derived cells in vitro.

Previous studies have attributed the increase in bone mass observed following bisphophonate (BP) therapy to their effects on bone-resorbing osteoclasts (OCs). However, recent evidence suggests that BPs can also act directly on bone forming osteoblasts (OBs) to increase their anabolic activity. Using an established model of in vitro OB differentiation, we found that the potent nitrogen-containing BP, zoledronic acid (ZOL), may enhance the bone forming potential of human adult OB-like cells in vitro by inducing their differentiation. ZOL dose dependently induced both cytostasis and cell death in OB-like cells at concentrations of 0.5 microM or greater. Cells expressing high levels of the osteoprogenitor antigen, STRO-1, exhibited a greater proliferative potential than STRO-1negative/dim cells, and were more susceptible to the cytostatic and apoptotic effects of ZOL. ZOL was also found to promote bone cell differentiation, as evidenced by an increase in the number of cells exhibiting a more differentiated (STRO-1(-)/AP+ and STRO-1(-)/AP-) phenotype. Analysis of gene expression, using semi-quantitative RT-PCR, demonstrated that ZOL treatment resulted in a significant upregulation of osteocalcin (OCN) and bone morphogenetic protein-2 (BMP-2) gene expression. Furthermore, in vitro mineralisation studies revealed that ZOL enhanced mineralised matrix formation at concentrations between 5 and 25 microM. These results show that, in addition to its direct effects on OCs, ZOL also directly affects the proliferation and differentiation of human OB-like cells in vitro and may enhance bone formation in vivo.

Calcification, Physiologic↗
PubMed2004

A crucial role of caspase-3 in osteogenic differentiation of bone marrow stromal stem cells.

Caspase-3 is a critical enzyme for apoptosis and cell survival. Here we report delayed ossification and decreased bone mineral density in caspase-3-deficient (Casp3(-/-) and Casp3(+/-)) mice due to an attenuated osteogenic differentiation of bone marrow stromal stem cells (BMSSCs). The mechanism involved in the impaired differentiation of BMSSCs is due, at least partially, to the overactivated TGF-beta/Smad2 signaling pathway and the upregulated expressions of p53 and p21 along with the downregulated expressions of Cdk2 and Cdc2, and ultimately increased replicative senescence. In addition, the overactivated TGF-beta/Smad2 signaling may result in the compromised Runx2/Cbfa1 expression in preosteoblasts. Furthermore, we demonstrate that caspase-3 inhibitor, a potential agent for clinical treatment of human diseases, caused accelerated bone loss in ovariectomized mice, which is also associated with the overactivated TGF-beta/Smad2 signaling in BMSSCs. This study demonstrates that caspase-3 is crucial for the differentiation of BMSSCs by influencing TGF-beta/Smad2 pathway and cell cycle progression.

Adult↗
PubMed2003

Molecular and cellular characterisation of highly purified stromal stem cells derived from human bone marrow.

Previous studies have provided evidence for the existence of adult human bone marrow stromal stem cells (BMSSCs) or mesenchymal stem cells. Using a combination of cell separation techniques, we have isolated an almost homogeneous population of BMSSCs from adult human bone marrow. Lacking phenotypic characteristics of leukocytes and mature stromal elements, BMSSCs are non-cycling and constitutively express telomerase activity in vivo. This mesenchymal stem cell population demonstrates extensive proliferation and retains the capacity for differentiation into bone, cartilage and adipose tissue in vitro. In addition, clonal analysis demonstrated that individual BMSSC colonies exhibit a differential capacity to form new bone in vivo. These data are consistent with the existence of a second population of bone marrow stem cells in addition to those for the hematopoietic system. Our novel selection protocol provides a means to generate purified populations of BMSSCs for use in a range of different tissue engineering and gene therapy strategies.

Adipocytes↗
PubMed2003

SHED: stem cells from human exfoliated deciduous teeth.

To isolate high-quality human postnatal stem cells from accessible resources is an important goal for stem-cell research. In this study we found that exfoliated human deciduous tooth contains multipotent stem cells [stem cells from human exfoliated deciduous teeth (SHED)]. SHED were identified to be a population of highly proliferative, clonogenic cells capable of differentiating into a variety of cell types including neural cells, adipocytes, and odontoblasts. After in vivo transplantation, SHED were found to be able to induce bone formation, generate dentin, and survive in mouse brain along with expression of neural markers. Here we show that a naturally exfoliated human organ contains a population of stem cells that are completely different from previously identified stem cells. SHED are not only derived from a very accessible tissue resource but are also capable of providing enough cells for potential clinical application. Thus, exfoliated teeth may be an unexpected unique resource for stem-cell therapies including autologous stem-cell transplantation and tissue engineering.

Animals↗
PubMed2003

Perivascular niche of postnatal mesenchymal stem cells in human bone marrow and dental pulp.

Mesenchymal stem cell populations have previously been identified in adult bone marrow and dental pulp that are capable of regenerating the bone marrow and dental pulp microenvironments, respectively. Here we show that these stem cell populations reside in the microvasculature of their tissue of origin. Human bone marrow stromal stem cells (BMSSCs) and dental pulp stem cells (DPSCs) were isolated by immunoselection using the antibody, STRO-1, which recognizes an antigen on perivascular cells in bone marrow and dental pulp tissue. Freshly isolated STRO-1 positive BMSSCs and DPSCs were tested for expression of vascular antigens known to be expressed by endothelial cells (von Willebrand factor, CD146), smooth muscle cells, and pericytes (alpha-smooth muscle actin, CD146), and a pericyte-associated antigen (3G5), by immunohistochemistry, fluorescence-activated cell sorting (FACS), and/or immunomagnetic bead selection. Both BMSSCs and DPSCs lacked expression of von Willebrand factor but were found to be positive for alpha-smooth muscle actin and CD146. Furthermore, the majority of DPSCs expressed the pericyte marker, 3G5, while only a minor population of BMSSCs were found to be positive for 3G5. The finding that BMSSCs and DPSCs both display phenotypes consistent with different perivascular cell populations, regardless of their diverse ontogeny and developmental potentials, may have further implications in understanding the factors that regulate the formation of mineralized matrices and other associated connective tissues.

Adult↗
PubMed2003

Telomerase accelerates osteogenesis of bone marrow stromal stem cells by upregulation of CBFA1, osterix, and osteocalcin.

Telomerase activity can prevent telomere shortening and replicative senescence in human somatic cells. We and others have previously demonstrated that forced expression of telomerase in human bone marrow stromal stem cells (BMSSCs) was able to extend their life-span and enhance their bone-forming capability, without inducing malignant transformation. In this study, we determined that telomerase was able to accelerate calcium accumulation of human BMSSCs under osteogenic inductive conditions. Similarly, xenogeneic transplantation of telomerase-expressing BMSSCs (BMSSC-Ts) yielded ectopic bone formation at 2 weeks post-transplantation, 2-4 weeks earlier than typically seen with BMSSCs transfected with empty vector (BMSSC-Cs). Low-density DNA array analysis revealed that telomerase activity increases the expression of G1 regulating genes including cyclin D3, cyclin E1, E2F-4, and DP2, associated with hyperphosphorylation of retinoblastoma (pRb), leading to the extended proliferative capacity of BMSSC-Ts. Importantly, BMSSC-T transplants showed a higher number of human osteogenic cells at 8 weeks post transplantation compared with the BMSSC-C transplants, coupled with a significantly increased osteogenic capacity. One possible mechanism leading to accelerated osteogenesis by BMSSC-Ts may be attributed, at least in part, to the upregulation of the important osteogenic genes such as CBFA1, osterix, and osteocalcin in vitro. Taken together, these findings show that telomerase can accelerate cell cycle progression from G1-to-S phase and enhance osteogenic differentiation of BMSSCs, because of the upregulation of CBFA1, osterix, and osteocalcin.

Alu Elements↗