Differentiating neural crest stem cells induce proliferation of cultured rodent islet beta cells

AIMS/HYPOTHESIS

Efficient stimulation of cycling activity in cultured beta cells would allow the design of new strategies for cell therapy in diabetes. Neural crest stem cells (NCSCs) play a role in beta cell development and maturation and increase the beta cell number in co-transplants. The mechanism behind NCSC-induced beta cell proliferation and the functional capacity of the new beta cells is not known.

METHODS

We developed a new in vitro co-culture system that enables the dissection of the elements that control the cellular interactions that lead to NCSC-dependent increase in islet beta cells.

RESULTS

Mouse NCSCs were cultured in vitro, first in medium that stimulated their proliferation, then under conditions that supported their differentiation. When mouse islet cells were cultured together with the NCSCs, more than 35% of the beta cells showed cycle activity. This labelling index is more than tenfold higher than control islets cultured without NCSCs. Beta cells that proliferated under these culture conditions were fully glucose responsive in terms of insulin secretion. NCSCs also induced beta cell proliferation in islets isolated from 1-year-old mice, but not in dissociated islet cells isolated from human donor pancreas tissue. To stimulate beta cell proliferation, NCSCs need to be in intimate contact with the beta cells.

CONCLUSIONS/INTERPRETATION

Culture of islet cells in contact with NCSCs induces highly efficient beta cell proliferation. The reported culture system is an excellent platform for further dissection of the minimal set of factors needed to drive this process and explore its potential for translation to diabetes therapy.

Angiotensin converting enzyme inhibition blocks interstitial hyaluronan dissipation in the neonatal rat kidney via hyaluronan synthase 2 and hyaluronidase 1

A functional renin-angiotensin system (RAS) is required for normal kidney development. Neonatal inhibition of the RAS in rats results in long-term pathological renal phenotype and causes hyaluronan (HA), which is involved in morphogenesis and inflammation, to accumulate. To elucidate the mechanisms, intrarenal HA content was followed during neonatal completion of nephrogenesis with or without angiotensin converting enzyme inhibition (ACEI) together with mRNA expression of hyaluronan synthases (HAS), hyaluronidases (Hyal), urinary hyaluronidase activity and cortical lymphatic vessels, which facilitate the drainage of HA from the tissue. In 6-8days old control rats cortical HA content was high and reduced by 93% on days 10-21, reaching adult low levels. Medullary HA content was high on days 6-8 and then reduced by 85% to 12-fold above cortical levels at day 21. In neonatally ACEI-treated rats the reduction in HA was abolished. Temporal expression of HAS2 corresponded with the reduction in HA content in the normal kidney. In ACEI-treated animals cortical HAS2 remained twice the expression of controls. Medullary Hyal1 increased in controls but decreased in ACEI-treated animals. Urine hyaluronidase activity decreased with time in control animals while in ACEI-treated animals it was initially 50% lower and did not change over time. Cells expressing the lymphatic endothelial mucoprotein podoplanin in ACEI-treated animals were increased 18-fold compared to controls suggesting compensation. In conclusion, the high renal HA content is rapidly reduced due to reduced HAS2 and increased Hyal1 mRNA expressions. Normal angiotensin II function is crucial for inducing these changes. Due to the extreme water-attracting and pro-inflammatory properties of HA, accumulation in the neonatally ACEI-treated kidneys may partly explain the pathological renal phenotype of the adult kidney, which include reduced urinary concentration ability and tubulointerstitial inflammation.

Neural crest stem cells increase beta cell proliferation and improve islet function in co-transplanted murine pancreatic islets

AIMS/HYPOTHESIS

Long-term graft survival after islet transplantation to patients with type 1 diabetes is insufficient, necessitating the development of new strategies to enhance transplant viability. Here we investigated whether co-transplantation of neural crest stem cells (NCSCs) with islets improves islet survival and function in normoglycaemic and diabetic mice.

METHODS

Islets alone or together with NCSCs were transplanted under the kidney capsule to normoglycaemic or alloxan-induced diabetic mice. Grafts were analysed for size, proliferation, apoptosis and insulin release. In diabetic recipients blood glucose levels were examined before and after graft removal.

RESULTS

In mixed transplants NCSCs actively migrated and extensively associated with co-transplanted pancreatic islets. Proliferation of beta cells was markedly increased and transplants displayed improved insulin release in normoglycaemic mice compared with those receiving islet-alone transplants. Mixed grafts survived successfully and partially restored normoglycaemia in alloxan-induced diabetic mice.

CONCLUSIONS/INTERPRETATION

Co-grafting of NCSCs with pancreatic islets improved insulin release in mixed transplants and enhanced beta cell proliferation, resulting in increased beta cell mass. This co-transplantation model offers an opportunity to restore neural-islet interactions and improve islet functions after transplantation.

Cellular interaction of integrin alpha3beta1 with laminin 5 promotes gap junctional communication

Wounding of skin activates epidermal cell migration over exposed dermal collagen and fibronectin and over laminin 5 secreted into the provisional basement membrane. Gap junctional intercellular communication (GJIC) has been proposed to integrate the individual motile cells into a synchronized colony. We found that outgrowths of human keratinocytes in wounds or epibole cultures display parallel changes in the expression of laminin 5, integrin alpha3beta1, E-cadherin, and the gap junctional protein connexin 43. Adhesion of keratinocytes on laminin 5, collagen, and fibronectin was found to differentially regulate GJIC. When keratinocytes were adhered on laminin 5, both structural (assembly of connexin 43 in gap junctions) and functional (dye transfer) assays showed a two- to threefold increase compared with collagen and five- to eightfold over fibronectin. Based on studies with immobilized integrin antibody and integrin-transfected Chinese hamster ovary cells, the interaction of integrin alpha3beta1 with laminin 5 was sufficient to promote GJIC. Mapping of intermediate steps in the pathway linking alpha3beta1-laminin 5 interactions to GJIC indicated that protein trafficking and Rho signaling were both required. We suggest that adhesion of epithelial cells to laminin 5 in the basement membrane via alpha3beta1 promotes GJIC that integrates individual cells into synchronized epiboles.

Mechanisms attenuating cellular responses to neuropeptides: extracellular degradation of ligands and desensitization of receptors

Neuropeptides make up one of the largest and functionally most diverse groups of signaling molecules. They exert their effects by interacting with members of the large family of G-protein-coupled receptors, which transmit information about the extracellular environment to the interior of the cell by interacting with the heterotrimeric G-proteins. Cellular responses to neuropeptides are usually rapidly attenuated. Mechanisms of signal attenuation include removal of peptides from the extracellular fluid and receptor desensitization. Peptides are removed from the extracellular fluid principally by enzymatic degradation by cell surface enzymes, exemplified by neutral endopeptidase. Receptor desensitization is mediated by receptor phosphorylation by G-protein receptor kinases and second messenger kinases, interaction of receptors with arrestins, and consequent receptor uncoupling from G-proteins. Peptides also induce endocytosis of their receptors, which may contribute to desensitization by depleting the cell surface of high-affinity receptors. Recycling and processing of internalized receptors, which include dissociation of receptors from their ligands and receptor dephosphorylation, contribute to resensitization of cellular responses. These regulatory mechanisms are important for they determine the ability of cells to respond to agonists, and defects may result in uncontrolled stimulation of cells, which could cause disease. A greater understanding of the processes that modulate signaling by neuropeptides may lead to the development of novel receptor antagonists and agonists and help to explain the mechanism of drug tolerance.

Keratinocytes in human wounds express alpha v beta 6 integrin

Cell adhesion receptors of the integrin family play a major role during re-epithelialization of human wounds. We have previously documented that the expression of alpha v family integrins is induced in keratinocytes of mucosal wounds [1]. In the present investigation, we extended these studies to determine whether alpha v beta 6 integrin is expressed during wound healing in humans. Mucosal and epidermal wound sections from 1- to 7-day-old wounds were used for immunolocalization of integrins and their putative ligands. In addition, freshly isolated epidermal keratinocytes were used to study integrin expression in vitro. Expression of alpha v beta 6 integrin appeared relatively late during mucosal and dermal wound healing. Maximal expression was seen in 7-day-old wounds in which epithelial sheets had fused and granulation tissue was present. Fibronectin and tenascin, both possible ligands for alpha v beta 6 integrin, were found concentrated underneath the basal epithelial cells expressing this receptor, and the maximal expression of tenascin coincided with that of alpha v beta 6 integrin. Freshly isolated epidermal keratinocytes did not stain for alpha v beta 6 integrin but began to express this integrin after subculturing. Our results suggest that the expression of alpha v beta 6 integrin, a putative binding integrin for fibronectin and tenascin, is induced in keratinocytes when epithelial sheets fuse during wound healing.

The hamster flank organ model: is it relevant to man?

The critical role that androgens play in the etiology of acne has led to a search for topically active antiandrogens and the frequent use of the flank organ of the golden Syrian hamster as an animal model. 17-alpha-propyltestosterone (17-PT) has been identified as having potent antiandrogenic activity in the hamster model, and this report describes its clinical evaluation. Two double-blind placebo controlled studies comparing 4% 17-PT in 80% alcohol versus vehicle alone were conducted. One study examined 17-PT sebosuppressive activity in 20 subjects. The second study examined its efficacy in 44 subjects having mild to moderate acne. A third study measured in vitro percutaneous absorption of 17-PT through hamster flank and monkey skin, and human face skin in-vivo, using radioactive drug. 17-PT was found to be ineffective in reducing either the sebum excretion rate or the number of inflammatory acne lesions. Failure of 17-PT to show clinical activity was not a result of poor percutaneous absorption. Total absorption in man was 7.7% of the dose and only 1.0% in the hamster. The sebaceous gland of hamster flank organ is apparently more sensitive to antiandrogens than the human sebaceous gland.

Immunopathology of cutaneous T-cell lymphomas

In this study the authors attempted to establish immunopathologic criteria for the distinction of various T-cell lymphomas affecting the skin. We studied skin specimens from 27 patients with mycosis fungoides (MF) (n = 12), the Sézary syndrome (SS) (n = 6), adult T-cell leukemia (ATL) (n = 4), and nonepidermotropic T-cell lymphoma of large cell (n = 4) and lymphoblastic (n = 1) types. Identification of tumor cells in mixed cell populations and detection of weak expression of surface antigens by tumor cells was facilitated by immunoelectron microscopy. The mature helper T-cell phenotype (T11+ T3+ T4+) was found in 14 of 18 cases of MF/SS. One case of MF had a cytotoxic/suppressor (T4- T8+ 3A1+) phenotype; one with frequent blastic cells showed only weak expression of T4 antigen; 2 cases of SS were T11-. Tumor cells infiltrating the skin expressed 3Al antigen in 44% and cellular activation antigens Ia and/or Tac in 78% of patients with MF/SS. No consistent phenotypic differences were found between ATL cells from ATLV (HTLV) antibody-positive patients and tumor cells of patients with MF/SS who lacked this antibody. In contrast, a group of nonepidermotropic T-cell lymphomas showed phenotypic differences from MF/SS and ATL in all but 1 case. These cases were distinguished by the frequent absence of T3, T4, and Leu 1 antigens in 3 large-cell lymphomas; frequent expression of Ki-1 antigen, a Hodgkin's disease-associated antigen, in 2 cases with RS-like cells; and an immature thymocyte phenotype in lymphoblastic lymphoma. These findings demonstrate that tumor-cell phenotypes can be useful in distinguishing different histologic types of cutaneous T-cell lymphoma.

Quantitative acoustical assessment of wound maturation with acoustic microscopy

Preliminary results of the ultrasonic characterization of cutaneous wound tissue and surrounding margin, obtained with the scanning laser acoustic microscope, show an increase in the speed of sound and in the acoustic heterogeneity as function of wound age. As the wound age increased, the following results were noted: (1) The wound area, initially quite homogeneous in acoustic appearance, became more heterogeneous; (2) the acoustic appearance of the wound tended to become similar to that of the adjacent tissue; and (3) the ultrasonic velocity of the wound area increased from a range of 1540--1575 m/s at 7 days to a range of 1700--2000 m/s at 35 days.