Chun-Hung Chen

Novel nanoparticles for oral insulin delivery via the paracellular pathway

Novel nanoparticles (NPs) coated with chitosan which allow insulin to be administered orally were developed. The NPs could transiently and reversibly open the tight junctions in Caco-2 cell monolayers, thus increasing their paracellular permeability. After oral administration of the FITC-labelled NPs, fluorescence signals, co-localized with ZO-1 proteins, were observed at cell–cell contact sites in the small intestine of rats. The intensity of fluorescence signals observed at the duodenum was stronger and appeared at a deeper level than at the jejunum and the ileum. The insulin-loaded NPs suspended in water were stable in typical storage conditions. Release of the loaded insulin depended greatly on the stability of the NPs at distinct pH environments. Oral administration of insulin in the form of NPs in diabetic rats demonstrated a sustained effect of decreasing the blood glucose level over at least 10xa0h, indicating the effect of the prepared NPs in enhancing the absorption of fully functional insulin.

Spherically Symmetric Mesenchymal Stromal Cell Bodies Inherent with Endogenous Extracellular Matrices for Cellular Cardiomyoplasty

Cell transplantation via direct intramyocardial injection is a promising therapy for patients with myocardial infarction; however, retention of the transplanted cells at the injection sites remains a central issue following injection of dissociated cells. Using a thermoresponsive hydrogel system with a multiwell structure, we successfully developed an efficient technique to generate spherically symmetric bodies of mesenchymal stromal cells (MSCs) inherent with endogenous extracellular matrices (ECMs) for direct intramyocardial injection. After injection through a needle and upon transferring to another growth surface, the time required to attach, migrate, and proliferate was significantly shorter for the MSC bodies than the dissociated MSCs. Employing a syngeneic rat model with experimental myocardial infarction, an intramyocardial injection was conducted with a needle directly into the peri‐infarct areas. There were four treatment groups (n = 10): sham, phosphate‐buffered saline, dissociated MSCs, and MSC bodies. The results obtained in the echocardiography and catheterization measurements demonstrated that the MSC body group had a superior heart function to the dissociated MSC group. Histologically, it was found that MSC bodies could provide an adequate physical size to entrap into the interstices of muscular tissues and offer a favorable ECM environment to retain the transplanted cells intramuscularly. Additionally, transplantation of MSC bodies stimulated a significant increase in vascular density, thus improving the cardiac function. These results indicated that the spherically symmetric bodies of MSCs developed in the study may serve as a cell‐delivery vehicle and improve the efficacy of therapeutic cell transplantation. STEM CELLS 2009;27:724–732

Porous tissue grafts sandwiched with multilayered mesenchymal stromal cell sheets induce tissue regeneration for cardiac repair.

AIMSnTo provide the basis for uniform cardiac tissue regeneration, a spatially uniform distribution of adhered cells within a scaffold is a prerequisite. To achieve this goal, a bioengineered tissue graft consisting of a porous tissue scaffold sandwiched with multilayered sheets of mesenchymal stromal cells was developed.nnnMETHODS AND RESULTSnThis tissue graft (sandwiched patch) was used to replace the infarcted wall in a syngeneic Lewis rat model with an experimentally chronic myocardial infarction (MI). There were four treatment groups (n >/= 10): sham, MI, empty patch, and sandwiched patch. After a 7 day culture of the sandwiched patch, a tissue graft with relatively uniform cell concentrations was obtained. The cells were viable and tightly adhered to the tissue scaffold, as the endogenous extracellular matrix inherent with multilayered cell sheets can act as an adhesive agent for cell attachment and retention. At retrieval, the area of the empty patch was relatively enlarged, suggesting reduced structural support, while that of the sandwiched patch remained about the same (P = 0.56). In the immunofluorescent staining, host cells together with neo-microvessels were clearly observed in the empty patch; however, there were still a large number of unfilled pores within the patch. In the sandwiched patch, besides host cells, originally seeded cells were populated within the entire patch. No apparent evidence of apoptotic cell death was found in both studied patches. Thus, the sandwiched-patch-treated hearts demonstrated a better heart function to the empty-patch-treated hearts (P < 0.05).nnnCONCLUSIONnThe results demonstrated that this novel bioengineered tissue graft can serve as a useful cardiac patch to restore the dilated left ventricle and stabilize heart functions after MI.