Biomedical subjects

R Rivkah Isseroff

Publications and source records attributed to R Rivkah Isseroff.

22 records · Page 2Linked to original sources

PubMed2002

Beta-adrenergic receptor activation inhibits keratinocyte migration via a cyclic adenosine monophosphate-independent mechanism.

There is increasing evidence that G-protein-coupled receptors cross-talk with growth factor receptor-mediated signal transduction in a variety of cell types. We have investigated mechanisms by which the activation of beta-adrenergic receptors, classically GTP-binding proteins coupled receptors, influence the migration of cultured human keratinocytes. We found that iso-proterenol, a beta-adrenergic receptor-selective agonist, inhibited cell migration stimulated by either epidermal growth factor, or extracellular Ca2+ in a concentration-dependent manner. This was prevented by pretreatment of the cells with the beta-adrenergic receptor-selective antagonist timolol. Interestingly, isoproterenol, at a concentration of 1 nm, did not measurably increase intracellular cyclic adenosine monophosphate concentrations yet inhibited cell migration by 50%. To test further if isoproterenol's actions were mediated via activation of adenylyl cyclase, two inhibitors of its activity, 2'5'-dideoxyadenosine and SQ22536, were used. Both compounds significantly diminished iso-proterenol-induced increases in intracellular cyclic adenosine monophosphate concentrations but did not attenuate isoproterenol-induced inhibition of cell migration. Also, forskolin (1 microm) markedly increased intracellular cyclic adenosine monophosphate concentrations but did not significantly inhibit cell migration. As mitogen-activated protein kinases are known to signal growth factor-stimulated cell migration, we examined whether beta-adrenergic receptor-mediated inhibition of keratinocyte migration might occur via inactivation of mitogen-activated protein kinases. We found that isoproterenol inhibited phosphorylation of extracellular signal-regulated kinase mitogen-activated protein kinase in a concentration-dependent manner but had no effect on the phosphorylation of the stress mitogen-activated protein kinases c-jun N-terminal kinase and stress-activated protein kinase-2. Neither forskolin nor a membrane permeable cyclic adenosine monophosphate analog inhibited phosphorylation of any of these mitogen-activated protein kinases. These findings suggest that beta-adrenergic receptor-induced inhibition of keratinocyte migration is mediated through inhibition of the extracellular signal-regulated kinase mitogen-activated protein kinase signaling in a cyclic adenosine monophosphate-independent manner.

Adrenergic beta-Agonists↗

PubMed2002

A fibrin-based bioengineered ocular surface with human corneal epithelial stem cells.

PURPOSE: The purpose of the investigation was to prepare a bioengineered ocular surface tissue replacement consisting of (presumed) human corneal epithelial stem cells in a cross-linked fibrin gel for potential transplant. METHODS: Presumed human epithelial stem cells were harvested, isolated, and cultivated as previously described from adult donor corneas obtained from a tissue and organ bank. The cultured corneal epithelial stem cells were suspended in a fibronectin/fibrin gel cross-linked by factor XIII. Plasma components were derived from a fibrinogen-rich cryoprecipitate of human plasma. Suspended cells proliferated in the fibrin gel, giving rise to colonies that eventually coalesced to near confluence over the 15 days of cultivation. The gels were sectioned and immunostained for keratin 3 (AE5) and keratin 19. RESULTS: The fibrin gel product with corneal stem cells was easily manageable and maneuverable. Addition of the protease inhibitor aprotinin to the incubation medium prevented gel degradation; once it was removed, gels disintegrated within 24 hours. All of the cells cultivated in the fibrin gel stained positively for keratin 3 (AE5), indicating differentiation along the corneal epithelium lineage. Cells located in the center of the colonies were keratin 19-positive, suggesting a more primitive cell type. Growth kinetics were documented. CONCLUSIONS: A bioengineered ocular surface with a combination of presumed corneal epithelial stem cells in a cross-linked fibrin gel represents a potential improvement in current attempts to create a transportable, pliable, and stable tissue replacement. Since both the cells and the plasma components of the fibrin gel are of human origin, this technique provides the potential for a totally autologous bioengineered replacement tissue.

Adult↗

PubMedDate not supplied

Melanocytes do not migrate directionally in physiological DC electric fields.

Wounding skin generates an endogenous electric field of 100-200 mV/mm in the immediate vicinity of the wound. When keratinocytes are exposed to direct current electric fields of this magnitude, they exhibit galvanotaxis, or directional migration toward the cathode, suggesting that wound-generated electric fields provide migrational cues that contribute to wound healing. Because melanocytes must also migrate into the healing wound to repigment it, their motility in response to electric fields of physiologic magnitude was examined. Human skin-derived melanocytes, either exposed to 100 mV/mm direct current electric fields or nonexposed controls, both exhibited motility rates of 9 micro m/hour, significantly (three- to five-fold) lower than the motility rates of keratinocytes under identical conditions. However, in sharp contrast to keratinocytes, melanocytes exhibited no directional migration in the electric field. Additionally, neither the number of primary dendrites per cell, nor the orientation of the dendrites with respect to the field vector, nor the average length of the dendrites was significantly different in melanocytes exposed to the electric field as compared to nonexposed controls. Thus, in marked contrast to keratinocytes, human skin-derived melanocytes do not respond to direct current electric fields of physiologic magnitude with either directional migration or reorientation of dendrites. This may account for the delay in repigmentation that often accompanies wound reepithelialization.

Cell Movement↗

PubMedDate not supplied

Beta 2-adrenergic receptor activation delays dermal fibroblast-mediated contraction of collagen gels via a cAMP-dependent mechanism.

Dermal fibroblasts actively contribute to wound healing by migrating to the wound, synthesizing extracellular matrices, and generating mechanical forces within the wound to initiate wound contraction. Fibroblast-seeded collagen gels provide an in vitro model to study wound contraction. The authors are evaluating the role of the adrenergic signaling system in cutaneous wound repair and recently found that beta2-adrenergic receptor (beta2-AR) activation markedly decreases keratinocyte migration, an essential step in wound reepithelialization. Because the beta2-ARs are also expressed on dermal fibroblasts, a study was initiated to determine the effects of beta-adrenergic agonists on dermal fibroblast-mediated collagen gel contraction. A beta-agonist (isoproterenol) delayed gel contraction in a dose-dependent manner. A beta2-AR specific antagonist (ICI 118,551) prevented the delay, indicating that the beta2-AR alone mediated the delay. The active cyclic adenosine monophosphate (cAMP) analog also delayed collagen gel contraction, whereas an inactive cAMP analog partially prevented the delay, suggesting that the mechanism for beta-AR agonist-mediated delay was partly cAMP-dependent. Identifying and characterizing agents that modulate wound contraction improves understanding of the wound healing process and could result in novel therapeutic strategies for preventing unwanted wound contraction in burn and trauma patients.

Collagen↗