Near-infrared Laser Doppler Flowmetry Research Articles

A novel bioscaffold with naturally-occurring extracellular matrix promotes hepatocyte survival and vessel patency in mouse models of heterologous transplantation

BackgroundNaïve decellularized liver scaffold (nDLS)-based tissue engineering has been impaired by the lack of a suitable extracellular matrix (ECM) to provide “active micro-environmental” support. AimThe present study aimed to examine whether a novel, regenerative DLS (rDLS) with an active ECM improves primary hepatocyte survival and prevents thrombosis.Methods: rDLS was obtained from a 30–55% partial hepatectomy that was maintained in vivo for 3–5 days and then perfused with detergent in vitro. Compared to nDLS generated from normal livers, rDLS possesses bioactive molecules due to the regenerative period in vivo. Primary mouse hepatocyte survival was evaluated by staining for Ki-67 and Trypan blue exclusion. Thrombosis was assessed by immunohistochemistry and ex vivo diluted whole-blood perfusion. Hemocompatibility was determined by near-infrared laser-Doppler flowmetry and heterotopic transplantation. ResultsAfter recellularization, rDLS contained more Ki-67-positive primary hepatocytes than nDLS. rDLS had a higher oxygen saturation and blood flow velocity and a lower expression of integrin αIIb and α4 than nDLS. Tumor necrosis factor-α, hepatocyte growth factor, interleukin-10, interleukin-6 and interleukin-1β were highly expressed throughout the rDLS, whereas expression of collagen-I, collagen-IV and thrombopoietin were lower in rDLS than in nDLS. Improved blood vessel patency was observed in rDLS both in vitro and in vivo. The results in mice were confirmed in large animals (pigs).Conclusion: rDLS is an effective DLS with an “active microenvironment” that supports primary hepatocyte survival and promotes blood vessel patency. This is the first study to demonstrate a rDLS with a blood microvessel network that promotes hepatocyte survival and resists thrombosis.

Temporal dynamics and magnitude of the blood flow response at the optic disk in normal subjects during functional retinal flicker-stimulation

Near-infrared laser Doppler flowmetry was applied in 15 normal volunteers to record the time course and magnitude of changes in the velocity (Vel), volume (Vol) and flow ( F) of blood and tissue reflectance ( R) at the optic disk in response to 40 and 50 s of increased retinal neural activity. This activity was evoked by diffuse luminance flicker of the retinal posterior pole. After 20 s of flicker, the group averages of Vel, Vol, and F were significantly higher than at baseline (pre-flicker) by 12, 24 and 38%. Time constants of the increases in Vel, Vol, and F were 3.4, 12.7 and 9.1 s, respectively. The group average change in R of 1% was not significant. However, in one subject, 15 recordings from the same site of the optic disk showed a significant increase in R of 8%, with a time course similar to that of Vol. Our findings show that, in the human optic nerve, a white matter tissue, the temporal dynamics and magnitude of the response of blood flow to an increase in retinal neural activity are similar to those reported for brain gray matter. Furthermore, although the R-response could be due, in part, to changes in blood volume, other factors, such as activity-evoked tissue scattering changes, may also affect this response.

Simultaneous measurement of local cortical blood flow and tissue oxygen saturation by Near infra-red Laser Doppler flowmetry and remission spectroscopy in the pig brain.

In the current study we evaluated the combined use of Near-infrared Laser-Doppler flowmetry (NiLDF) and Remission Spectroscopy (RS) for measurement of regional perfusion and oxygen saturation of the cerebral cortex. An epidural probe for combined measurements of NiLDF and RS was placed above the parietal or frontal cortex of nine anesthetized juvenile pigs. Cerebral perfusion pressure (CPP) was stepwise decreased by intracisternal infusion of artificial CSF at clamped arterial blood pressure (baseline, CPP50, CPP40, CPP30 mmHg, ischemia). Subsequent reperfusion was followed for 3 h. Regional cerebral blood flow (rCBF) was measured with colored microspheres (CMS) and compared with corresponding NiLDF values during CMS injection. Cerebral venous oxygen saturation was measured in blood samples withdrawn from the sagittal sinus and compared with simultaneous recordings of tissue oxygenation during blood withdrawal. Linear regression analysis resulted in a significant correlation (p < 0.001) for changes in regional perfusion during CPP decrease and reperfusion, as measured with CMS and NiLDF (r = 0.92, n = 39). A significant correlation was also found for tissue oxygen saturation--as measured with RS--and cerebral venous oxygen saturation (r = 0.85, n = 67). Although the problem of spatial variability remains to be solved, the combined use of NiLDF and RS allows continuous and non-invasive monitoring of changes of key parameters of oxygen metabolism within the cerebral cortex.