ABSTRACT
Islet transplantation for type 1 diabetes is limited by a shortage of donor islets and requirement for immunosuppression. We approached this problem by inducing in vivo islet neogenesis in non-obese diabetic (NOD) diabetic mice, a model of autoimmune diabetes. We demonstrate that gene therapy with helper-dependent adenovirus carrying neurogenin3 (Ngn3), an islet lineage-defining transcription factor, and betacellulin (Btc), an islet growth factor, leads to the induction of periportal insulin-positive cell clusters in the liver, which are rapidly destroyed. To specifically accord protection to these 'neo-islets' from cytokine-mediated destruction, we overexpressed suppressor of cytokine signaling 1 (SOCS1) gene, using a rat insulin promoter in combination with Ngn3 and Btc. With this approach, about half of diabetic mice attained euglycemia sustained for over 4 months, regain glucose tolerance and appropriate glucose-stimulated insulin secretion. Histological analysis revealed periportal islet hormone-expressing 'neo-islets' in treated mouse livers. Despite evidence of persistent 'insulitis' with activated T cells, these 'neo-islets' persist to maintain euglycemia. This therapy does not affect diabetogenicity of splenocytes, as they retain the ability to transfer diabetes. This study thus provides a proof-of-concept for engineering in vivo islet neogenesis with targeted resistance to cytokine-mediated destruction to provide a long-term reversal of diabetes in NOD mice.
Subject(s)
Basic Helix-Loop-Helix Transcription Factors/genetics , Betacellulin/genetics , Diabetes Mellitus, Experimental/therapy , Genetic Therapy/methods , Nerve Tissue Proteins/genetics , Suppressor of Cytokine Signaling Proteins/genetics , Adenoviridae/genetics , Animals , Basic Helix-Loop-Helix Transcription Factors/biosynthesis , Betacellulin/biosynthesis , Diabetes Mellitus, Experimental/genetics , Diabetes Mellitus, Experimental/metabolism , Female , Immunosuppression Therapy , Insulin/biosynthesis , Insulin/genetics , Islets of Langerhans/physiology , Islets of Langerhans Transplantation/methods , Liver/metabolism , Mice , Mice, Inbred NOD , Nerve Tissue Proteins/biosynthesis , Suppressor of Cytokine Signaling 1 Protein , Suppressor of Cytokine Signaling Proteins/biosynthesisABSTRACT
A technique to measure the dynamic mechanical properties of human skin in vivo is described. The technique measures the propagation and attenuation of shear waves in skin tissue over a range of frequencies (8-1016 Hz). Results show that both the propagation velocity and attenuation of shear waves in skin are highly dependent upon the water content of the stratum corneum. The technique was used to measure the dynamic mechanical properties of the skin on the back of the left hand for a group of 16 men ranging in age from 24-63 years. The results suggest that aged skin has a lower water content than the skin of younger men.
Subject(s)
Aging , Body Water/metabolism , Skin/metabolism , Adult , Biomechanical Phenomena , Humans , Male , Middle Aged , TransducersABSTRACT
The propagation and attenuation of shear waves in human skin is investigated over a frequency range of near zero to 1000 Hz. The results show that at frequencies below a few hundred Hz, shear waves propagate along the skin surface and thus provide information on the dynamic mechanical properties of the stratum corneum. The surface waves, however, are rapidly attenuated with increasing frequency so that at frequencies above about 500 Hz the energy is propagated only as bulk shear waves. Thus, at high frequencies the properties measured are those of the dermis.