Biomedical subjects

Charles W Archer

Publications and source records attributed to Charles W Archer.

8 recordsLinked to original sources

PubMed2006

Mesenchymal multipotency of adult human periosteal cells demonstrated by single-cell lineage analysis.

OBJECTIVE: To investigate whether periosteal cells from adult humans have features of multipotent mesenchymal stem cells (MSCs) at the single-cell level. METHODS: Cell populations were enzymatically released from the periosteum of the proximal tibia obtained from adult human donors and then expanded in monolayer. Single-cell-derived clonal populations were obtained by limiting dilution. Culture-expanded periosteal cell populations were tested for their growth potential and for expression of conventional markers of MSCs and were subjected to in vitro assays to investigate their multilineage potential. To assess their multipotency in vivo, periosteal cells were injected into a regenerating mouse tibialis anterior muscle for skeletal myogenesis or were either seeded into an osteoinductive matrix and implanted subcutaneously into nude mice for osteogenesis or implanted in a joint surface defect under a periosteal flap into goats for chondrogenesis. Cell phenotypes were analyzed by histochemistry and immunohistochemistry and by reverse transcription-polymerase chain reaction for the expression of lineage-related marker genes. RESULTS: Regardless of donor age, periosteal cells were clonogenic and could be expanded extensively in monolayer, maintaining linear growth curves over at least 30 population doublings. They displayed long telomeres and expressed markers of MSCs. Under specific conditions, both parental and single-cell-derived clonal cell populations differentiated to the chondrocyte, osteoblast, adipocyte, and skeletal myocyte lineages in vitro and in vivo. CONCLUSION: Our study demonstrates that, regardless of donor age, the adult human periosteum contains cells that, upon enzymatic release and culture expansion, are multipotent MSCs at the single-cell level.

Adult↗

PubMed2006

Enhancing tissue integration in cartilage repair procedures.

Arguably, the gold standard of biological repair of articular cartilage lesions is autologous chondrocyte transplantation. Although the clinical outcomes appear to range between good and excellent in most cases, there are, nevertheless, both clinical and biological challenges that remain to improve rehabilitation and clinical outcome. One of the major biological problems relates to tissue integration of the reparative tissue into the host tissue at a predictable level. Often within a single lesion, varying degrees of integration can be observed from total integration through to non-integration as one passes through the defect. Here we briefly review some of the literature relating to this problem and include some of our own data drawn from questions we have posed about the biological nature of cartilage/cartilage integration. The nature and status of the tissue that comprises the wound lesion edge is central to tissue integration, and controlling aspects of trauma and free-radical-induced cell death together with matrix synthesis are identified as two components that require further investigation. Interestingly, there appears to be a limited ability of chondrocytes to be able to infiltrate existing cartilage matrices and even to occupy empty chondrocyte lacunae. Proliferation as a result of blunt and sharp trauma shows differential responses. As expected, blunt trauma induces a greater proliferative burst than sharp trauma and is more widespread from the lesion edge. However, in the case of sharp trauma, the basal cells enter proliferation before surface zone chondrocytes, which is not the case in blunt wounds. Regulation of these and associated processes will be necessary in order to devise strategies that can predict successful integration in biological repair procedures.

Cartilage, Articular↗

PubMed2004

The surface of articular cartilage contains a progenitor cell population.

It is becoming increasingly apparent that articular cartilage growth is achieved by apposition from the articular surface. For such a mechanism to occur, a population of stem/progenitor cells must reside within the articular cartilage to provide transit amplifying progeny for growth. Here, we report on the isolation of an articular cartilage progenitor cell from the surface zone of articular cartilage using differential adhesion to fibronectin. This population of cells exhibits high affinity for fibronectin, possesses a high colony-forming efficiency and expresses the cell fate selector gene Notch 1. Inhibition of Notch signalling abolishes colony forming ability whilst activated Notch rescues this inhibition. The progenitor population also exhibits phenotypic plasticity in its differentiation pathway in an embryonic chick tracking system, such that chondroprogenitors can engraft into a variety of connective tissue types including bone, tendon and perimysium. The identification of a chondrocyte subpopulation with progenitor-like characteristics will allow for advances in our understanding of both cartilage growth and maintenance as well as provide novel solutions to articular cartilage repair.

Amyloid Precursor Protein Secretases↗

PubMed2003

Development of synovial joints.

Synovial joints arise through two main processes. In long bone elements, cartilaginous differentiation occurs across the locations of the prospective joints that then segment secondarily. This process occurs through the development of a noncartilaginous region known as the interzone. The interzone becomes an important signaling center to the opposing elements, which can regulate growth through such factors as GDF-5. The interzone also expresses bone morphogenetic proteins (BMPs) and their antagonists, such as noggin. Overexpression of BMPs, or the loss of noggin leads to joint fusions. The interzone also expresses Wnt-14, which appears to be specific for this region in the developing anlagen, and regulates its nonchondrogenic nature. Cavitation of the joint follows, driven by selective high-level synthesis of hyaluronan by interzone cells and presumptive synovial cells. In addition, as the interzone disperses during cavity enlargement, data are now accruing that suggest that both the synovium and articular cartilage develop from this population. Finally, the development of articular cartilage progresses through appositional growth driven by a progenitor/stem cell subpopulation that resides in the articular surface. The individual elements of the skeleton are connected together at regions termed joints or articulations. Classically, there are three broad categories of joints: immovable joints (syntharthroses); mixed articulations, in which the range of movement is limited (amphiarthroses); and the movable, or synovial, joints (diarthroses). This review concentrates on the development of the synovial joints.

Animals↗

PubMed2003

The chondrocyte.

The chondrocyte is the resident cell of cartilage that is a prominent tissue in the embryo acting as a template for the development of skeletal elements. In the adult, the distribution of permanent cartilage is much more restricted and is necessary for mechanical support, growth and movement. The cell is isolated within a voluminous extracellular matrix (ECM) that is neither vascularised nor innervated. As a result, nutrient/waste exchange occurs through diffusion and, consequently, under normal and pathological conditions, the cell is unique in its ability to exist in a low oxygen tension environment. Partly as a result of these properties, the tissue has a low reparative potential that, in the case of articular cartilage, predisposes the tissue to degenerative conditions such as arthritis that is a significant clinical problem. Cellfacts. Cytoplasmically isolated. High matrix/cell volume ratio. Do not divide after skeletal maturity unless during pathology. Major contributor to growth of the body. Most energy requirements obtained through glycolysis.

Animals↗

PubMed2003

Secondary chondrocyte-derived Ihh stimulates proliferation of periosteal cells during chick development.

The development of the skull is characterised by its dependence upon epigenetic influences. One of the most important of these is secondary chondrogenesis, which occurs following ossification within certain membrane bone periostea, as a result of biomechanical articulation. We have studied the genesis, character and function of the secondary chondrocytes of the quadratojugal of the chick between embryonic days 11 and 14. Analysis of gene expression revealed that secondary chondrocytes formed coincident with Sox9 upregulation from a precursor population expressing Cbfa1/Runx2: a reversal of the normal sequence. Such secondary chondrocytes rapidly acquired a phenotype that is a compound of prehypertrophic and hypertrophic chondrocytes, exited from the cell cycle and upregulated Ihh. Pulse and pulse/chase experiments with BrdU confirmed the germinal region as the highly proliferative source of the secondary chondrocytes, which formed by division of chondrocyte-committed precursors. By blocking Hh signalling in explant cultures we show that the enhanced proliferation of the germinal region surrounding the secondary chondrocytes derives from this Ihh source. Additionally, in vitro studies on membrane bone periosteal cells (non-germinal region) demonstrated that these cells can also respond to Ihh, and do so both by enhanced proliferation and precocious osteogenesis. Despite the pro-osteogenic effects of Ihh on periosteal cell differentiation, mechanical articulation of the quadratojugal/quadrate joint in explant culture revealed a negative role for articulation in the regulation of osteocalcin by germinal region descendants. Thus, the mechanical stimulus that is the spur to secondary chondrocyte formation appears able to override the osteogenic influence of Ihh on the periosteum, but does not interfere with the cell cycle-promoting component of Hh signalling.

Animals↗

PubMedDate not supplied

Gap junctional intercellular communication and cytoskeletal organization in chondrocytes in suspension in an ultrasound trap.

Particles or cells suspended in an appropriately designed ultrasound standing wave field can be aggregated at a node to form a single monolayer in a plane that can be interrogated microscopically. The approach is applied here to investigate the temporal development of F-actin and Cx43 distribution and of gap junctional intercellular communication in 2-D chondrocyte aggregates (monolayers) rapidly and synchronously formed and held in suspension in an ultrasound trap. Development of the F-actin cytoskeleton in the confluent single layer of 'cuboidal' cells forming the aggregate was completed within 1 h. Chondrocytes levitated in the trap synchronously formed functional gap junctions (as assessed by CMFDA dye transfer assays) in less than 1 h of initiation of cell-cell contact in the trap. It was shown that Cx43 gene expression was retained in isolated chondrocytes in suspension. Preincubation of cells with the protein synthesis inhibitor cycloheximide caused a six-fold decrease in Cx43 accumulation (as assessed by immunofluorescence) at the interfaces of chondrocytes in the aggregate. It is shown that the ultrasound trap provides an approach to studying the early stages of cytoskeletal and gap junction development as cells progress from physical aggregation, through molecular adhesion, to display the intracellular consequences of receptor interactions.

Actins↗

PubMedDate not supplied

Mechanical regulation of secondary chondrogenesis.

The development of the skull is characterised by its dependence upon epigenetic influences. One of the most important of these is secondary chondrogenesis, which occurs following ossification within certain membrane bone periostea, as a result of biomechanical articulation. We have studied the genesis, character and function of the secondary chondrocytes of the quadratojugal of the chick between embryonic days 11 and 14. Analysis of gene expression revealed that secondary chondrocytes formed coincident with Sox9 upregulation from a precursor population expressing Cbfa1/Runx2: a reversal of the normal sequence. Such secondary chondrocytes rapidly acquired a phenotype that is a compound of prehypertrophic and hypertrophic chondrocytes, exited from the cell cycle and upregulated Ihh. Pulse and pulse/chase experiments with BrdU confirmed the germinal region as the highly proliferative source of the secondary chondrocytes, which formed by division of chondrocyte-committed precursors. By blocking Hh signalling in explant cultures we show that the enhanced proliferation of the germinal region surrounding the secondary chondrocytes derives from this Ihh source. Additionally, in vitro studies on membrane bone periosteal cells (nongerminal region) demonstrated that these cells can also respond to Ihh, and do so both by enhanced proliferation and precocious osteogenesis. Despite the pro-osteogenic effects of Ihh on periosteal cell differentiation, mechanical articulation of the quadratojugal/quadrate joint in explant culture revealed a negative role for articulation in the regulation of osteocalcin by germinal region descendants. Thus, the mechanical stimulus that is the spur to secondary chondrocyte formation appears able to override the osteogenic influence of Ihh on the periosteum, but does not interfere with the cell cycle-promoting component of Hh signalling.

Animals↗