Biomedical subjects

Gregory C Saggers

Publications and source records attributed to Gregory C Saggers.

7 recordsLinked to original sources

PubMed2007

Rat mast cells communicate with fibroblasts via gap junction intercellular communications.

Usually mast cells (MCs) modulate other cellular activities through the release of their cytoplasmic granules. Recently, gap junctional intercellular communication (GJIC) between an established human MC cell line (HMC-1) co-cultured with human dermal fibroblasts in fibroblast populated collagen lattices (FPCLs), enhanced the rate and degree of FPCL contraction. However, HMC-1 cells were unable to generate GJIC with human neonatal fibroblasts in monolayer culture. Here freshly isolated rat peritoneal MCs are co-cultured with fibroblasts in collagen lattices and in monolayer culture in vitro and introduced into rat polyvinyl alcohol (PVA) sponge implants in vivo. Co-cultured MC-FPCL contracted faster and to a greater degree. Loading Calcein AM green fluorescent dye into red fluorescent Dil tagged MC generates MC-paratroopers. When MC-paratroopers form GJIC with fibroblasts, some green dye is passed into the fibroblast, while the MC-paratrooper retains both its red and green fluorescence. MC-paratroopers passed green fluorescent dye into both human and rat dermal fibroblasts in monolayer culture. In rats 7-day-old subcutaneous PVA sponge implants, which received an injection of MC-paratroopers, exhibited auto-fluorescent green fibroblasts, when harvested 24 h later. MC-paratroopers pretreated with a long-acting GJIC inhibitor prior to their introduction into PVA sponge implants, failed to pass dye into fibroblasts. It is proposed that GJIC between granulation tissue fibroblasts and MCs can modulate some aspects of wound repair and fibrosis.

Animals↗

PubMed2006

Gap junction communications influence upon fibroblast synthesis of Type I collagen and fibronectin.

In rats polyvinyl alcohol sponge subcutaneous implants treated with gap junctional intercellular communications (GJIC) uncouplers showed reduced deposition of connective tissue. Do uncouplers inhibit the synthesis and deposition of a new connective tissue by fibroblasts? Confluent human dermal fibroblasts in serum-free medium received either endosulfan or oleamide, GJIC uncouplers. Collected media were subjected to Dot Blot analysis for native Type I collagen and fibronectin. Uncoupler-treated fibroblasts released less Type I collagen, while there was no change in fibronectin release. Collagen synthesis was restored to normal, when the uncouplers were removed, showing that these uncouplers were reversible and not toxic to cells. Northern blot analysis revealed procollagen alpha1 (I) mRNA was minimally affected by endosulfan. Oleamide-treated 17-day chick embryo calvaria explants were incubated with Type I collagen antibody, frozen, cryosectioned, and then subjected to rhodamine (Rh) tagged anti-mouse-IgG antibody, to detect newly deposited Type I collagen. Fluorescent antibody-collagen complexes were localized on the periphery of cells in control calvaria, but absent around cells in oleamide-treated calvaria. GJIC optimize collagen synthesis but not fibronectin synthesis. The lack of connective tissue deposited in granulation tissues treated with uncouplers appears related to the inhibition of collagen synthesis. These findings suggest that altering GJIC might control collagen deposition in scarring.

Animals↗

PubMed2005

Dynamic changes appearing in collagen fibers during intrinsic tendon repair.

Intrinsic healing of severed tendons shows a delay in a gain in breaking strength and the tendon becomes translucent. The cause of tendon translucence was investigated in suture-repaired rat Achilles tendon. The repair site with adjacent translucent tendon were evaluated histologically on day 10 by immunofluorescence and transmission electron microscopy. The healing tendon translucent region by hematoxylin-eosin staining had few inflammatory cells, polarized light birefringence showed thinner collagen fibers, immunofluorescence showed few myofibroblasts, and transmission electron microscopy revealed frayed, irregular thin collagen fibers. During embryogenesis, tendon fibers grow by the addition of discreet collagen fibril segment structures. The speculation is that collagen fibril segment structures are released from collagen fibers within the translucent tendon region for reuse during the regeneration of tendon collagen fibers during intrinsic tendon repair. Healing tendon translucence is related to a decrease in the diameter of collagen fibers by the release of collagen fibril segments within tendon bundles/fascicles.

Achilles Tendon↗

PubMed2004

Pulp nonfiction: microscopic anatomy of the digital pulp space.

The volar pad of the fingertip provides a very stable yet sensitive surface that gives the hand the ability to pinch and grasp. The focus of this study was to advance understanding of the anatomical features of the digital pulp space. The unusual features of the fingertip pulp space include prominent collagen fiber cords and a branching continuous fine vasculature. Prominent collagen fiber cords radiating out from beneath the epidermal basement membrane are like the cords of a parachute, which directly attach to the periosteum of the distal phalanx. Those collagen fiber cords are responsible for the firm attachment of the fingertip to the distal phalanx. There is a fine patent vasculature within the pulp space. Also contained in the capsule are numerous lobules of fat, which contribute to some elasticity of the fingertip. Principles of treatment for injuries or infections of the digital pulp should attempt to preserve this anatomical construct so that the firmness and vascular supply of the fingertip are maintained and not disrupted.

Collagen↗

PubMedDate not supplied

Topical vanadate optimizes collagen organization within granulation tissue.

Systemic ingestion of vanadate, a nonspecific inhibitor of tyrosine phosphatases, doubles wound breaking strength, enhances the packing of collagen fibers, and prevents the appearance of myofibroblasts in granulation tissue. Will the local application of vanadate mimic the systemic effects? Pairs of polyvinyl alcohol sponges, each with a central reservoir and attached injection port, were subcutaneously implanted in rats. Daily, one implant received 0.2 ml of saline and the other received 0.2 ml of 0.03 mM vanadate in saline. On day 7, harvested sponges had equivalent wet weights. The vanadate-treated sponges had fibroblasts separated by connective tissue, with a more intense birefringence of the collagen fibers. Transmission electron microscopy showed collagen more uniformly packed in the vanadate treated sponges where collagen fibers were equally spaced and had equal diameters. By immunohistology, myofibroblasts, defined by the expression of alpha-smooth muscle actin within stress fibers, were absent in vanadate-treated granulation tissue. The expression of alpha-smooth muscle actin was restricted to smooth muscle cells of blood vessels. Controls had densely packed alpha-smooth muscle actin staining myofibroblasts, weak birefringence, and randomly spaced collagen fibers with irregular diameters. We conclude that the local application of vanadate prevents the appearance of myofibroblasts and optimizes the organization of collagen fibers in developing granulation tissue.

Administration, Topical↗

PubMedDate not supplied

Mast cells promote fibroblast populated collagen lattice contraction through gap junction intercellular communication.

The release of mast cell granules is commonly associated with inflammation and fibrosis. However, does direct communication between mast cells and fibroblasts through gap junction intercellular communication (GJIC) occur? Fibroblast populated collagen lattice (FPCL) cast with mast cells show enhanced lattice contraction. Do released granules or GJIC between mast cells and fibroblasts promote enhanced lattice contraction? Mast cells preloaded with a fluorescent dye that readily passes through gap junctions were cast in FPCL. Dye passed from mast cells into fibroblasts within these cocultured mast cell-FPCLs. Fatty acid amide hydrolase inhibitor blocks the breakdown of oleamide, which is a potent endogenous inhibitor of GJIC. GJIC was blocked for 3 days when mast cells were pulsed for 3 hours with fatty acid amide hydrolase inhibitor. Mast cells pretreated with fatty acid amide hydrolase inhibitor cast in cocultured mast cell-FPCLs failed to enhance cocultured lattice contraction. Mast cell-FPCLs made with mouse fibroblasts unable to generate GJIC failed to show enhanced lattice contraction. Degranulated mast cells were equal to intact mast cells at enhancing cocultured mast cell-FPCL contraction. The supernatant from degranulated mast cells had no effect upon FPCL contraction. Therefore, enhanced mast cell-FPCL contraction appears to be independent of mast cell granules, but dependent upon GJIC between fibroblasts and mast cells. We speculate that mast cell-fibroblast GJIC may play a role in fibrosis.

Animals↗

PubMedDate not supplied

Calmodulin-myosin light chain kinase inhibition changes fibroblast-populated collagen lattice contraction, cell migration, focal adhesion formation, and wound contraction.

Wound healing requires fibroblast migration, synthesis of new extracellular matrix, and organization of that matrix, all of which depend upon myosin ATPase activation and subsequent cytoplasmic actin-myosin contraction. Myosin ATPase activity is optimized by phosphorylation of myosin light chain at serine 19. Several different signaling pathways can perform that phosphorylation, the focus here is calcium saturated calmodulin dependent -myosin light chain kinase (CaM-MLCK). It is proposed that CaM-MLCK phosphorylation of myosin light chain and subsequent myosin ATPase activation affects granulation tissue fibroblast behavior and contributes to wound contraction. Myosin ATPase activity generates actin-myosin contraction within fibroblasts. Myosin ATPase activity is involved in ATP-induced cell contraction, the generation of focal adhesions, fibroblast migration, fibroblast populated collagen lattice (FPCL) contraction, and wound contraction. The MLCK inhibitors ML-9 and ML-7 inhibited ATP-induced cell contraction, fibroblast migration, FA formation, and FPCL contraction. The calmodulin inhibitors W7 and fluphenazine blocked rat open wound contraction. In addition, fluphenazine delayed re-epithelialization. These findings support the idea that fibroblast CaM-MLCK activity is essential for tissue repair. We speculate that inhibition of CaM-MLCK may reduce or prevent detrimental fibrotic contracture.

Animals↗