Search

Paneth cells were first described by Paneth in 1888. (1) They are normally found in the small intestine, right colon, and appendix. They are usually located at the base of [...], * Context.--Changes in Paneth cell numbers can be associated with chronic inflammatory diseases of the gastrointestinal tract. So far, no consensus has been achieved on the number of Paneth cells and their relevance to celiac disease (CD). Objectives.--To compare crypt and Paneth cell granule areas between patients with CD and those without CD (non-CD) using an artificial intelligence-based solution. Design.--Hematoxylin-eosin-stained sections of duodenal biopsies from 349 patients at the McGill University Health Centre were analyzed. Of these, 185 had a history of CD and 164 were controls. Slides were digitized, and NoCodeSeg, a code-free workflow using open-source software (QuPath, DeepMIB), was implemented to train deep learning models to segment crypts and Paneth cell granules. The total area of the entire analyzed tissue, epithelium, crypts, and Paneth cell granules was documented for all slides, and comparisons were performed. Results.--A mean intersection-over-union score of 88.76% and 91.30% was achieved for crypt areas and Paneth cell granule segmentations, respectively. On normalization to total tissue area, the crypt to total tissue area in CD was increased and the Paneth cell granule area to total tissue area decreased when compared to non-CD controls. Conclusions.--Crypt hyperplasia was confirmed in CD compared to non-CD controls. The area of Paneth cell granules, an indirect measure of Paneth cell function, decreased with increasing severity of CD. More importantly, our study analyzed complete hematoxylin-eosin slide sections using an efficient and easy to use coding-free artificial intelligence workflow. doi: 10.5858/arpa.2023-0074-OA)

This study aimed to investigate the simultaneous response of the cerebral and skeletal muscle microvasculature to the same phenylephrine (PE) boluses. A hybrid optical system that combines hyperspectral near‐infrared spectroscopy (hs‐NIRS) and diffuse correlation spectroscopy (DCS) was used to monitor changes in tissue oxygenation and perfusion. Data were collected from the head and hind limb of seven male Sprague–Dawley rats while administering intravenous (IV) injections of PE or saline to all animals. The response to saline was used as a control. Skeletal muscle oxygenation decreased significantly after PE injection, while a statistically underpowered decrease in perfusion was observed, followed by an increase beyond baseline. Vascular conductance also decreased in the muscle reflecting the drug's vasoconstrictive effects. Tissue oxygenation and perfusion increased in the brain in response to PE. Initially, there was a sharp increase in cerebral perfusion but no changes in cerebral vascular conductance. Subsequently, cerebral flow and vascular conductance decreased significantly below baseline, likely reflecting autoregulatory mechanisms to manage the excess flow. Further, fitting an exponential function to the secondary decrease in cerebral perfusion and increase in muscular blood flow revealed a quicker kinetic response in the brain to adjust blood flow. In the skeletal muscle, PE caused a transient decrease in blood volume due to vasoconstriction, which resulted in an overall decrease in hemoglobin content and tissue oxygen saturation. Since PE does not directly affect cerebral vessels, this peripheral vasoconstriction shunted blood into the brain, resulting in an initial increase in oxygenated hemoglobin and oxygen saturation. [ABSTRACT FROM AUTHOR]

Placental histopathology provides insights, or "snapshots", into relevant antenatal factors that could elevate the risk of perinatal brain injury. We present a systematic review and meta-analysis comparing frequencies of adverse neurological outcomes in infants born to women with placental abruption versus without abruption. Records were sourced from MEDLINE, Embase, and the CENTRAL Trials Registry from 1946 to December 2019. Studies followed the PRISMA guidelines and compared frequencies of neurodevelopmental morbidities in infants born to pregnant women with placental abruption (exposure) versus women without placental abruption (comparator). The primary endpoint was cerebral palsy. Periventricular and intraventricular (both severe and any grades of IVH) and any histopathological neuronal damage were the secondary endpoints. Study methodologic quality was assessed by the Ottawa–Newcastle scale. Estimated odds ratios (OR) and hazards ratio (HR) were derived according to study design. Data were meta-analyzed using a random effects model expressed as pooled effect sizes and 95% confidence intervals. We included eight observational studies in the review, including 1245 infants born to women with placental abruption. Results of the random effects meta-analysis show that the odds of infants born to pregnant women with placental abruption who experience cerebral palsy is higher than in infants born to pregnant women without placental abruption (OR 5.71 95% CI (1.17, 27.91); I2 = 84.0%). There is no statistical difference in the odds of infants born to pregnant women with placental abruption who experience severe IVH (grade 3+) (OR 1.20 95% CI (0.46, 3.11); I2 = 35.8%) and any grade of IVH (OR 1.20 95% CI (0.62, 2.32); I2 = 32.3%) vs. women without placental abruption. There is no statistically significant difference in the odds of infants born to pregnant women with placental abruption who experience PVL vs. pregnant women without placental abruption (OR 6.51 95% CI (0.94, 45.16); I2 = 0.0%). Despite our meta-analysis suggesting increased odds of cerebral palsy in infants born to pregnant women with placental abruption versus without abruption, this finding should be interpreted cautiously, given high heterogeneity and overall poor quality of the included studies. [ABSTRACT FROM AUTHOR]

Purpose: There is a need for bedside methods to monitor oxygen delivery in the microcirculation. Near-infrared spectroscopy commonly measures tissue oxygen saturation, but does not reflect the time-dependent variability of microvascular hemoglobin content (MHC) that attempts to match oxygen supply with demand. The objective of this study is to determine the feasibility of MHC monitoring in critically ill patients using high-resolution near-infrared spectroscopy to assess perfusion in the peripheral microcirculation. Methods: Prospective observational cohort of 36 patients admitted within 48 h at a tertiary intensive care unit. Perfusion was measured on the quadriceps, biceps, and/or deltoid, using the temporal change in optical density at the isosbestic wavelength of hemoglobin (798 nm). Continuous wavelet transform was applied to the hemoglobin signal to delineate frequency ranges corresponding to physiological oscillations in the cardiovascular system. Results: 31/36 patients had adequate signal quality for analysis, most commonly affected by motion artifacts. MHC signal demonstrates inter-subject heterogeneity in the cohort, indicated by different patterns of variability and frequency composition. Signal characteristics were concordant between muscle groups in the same patient, and correlated with systemic hemoglobin levels and oxygen saturation. Signal power was lower for patients receiving vasopressors, but not correlated with mean arterial pressure. Mechanical ventilation directly impacts MHC in peripheral tissue. Conclusion: MHC can be measured continuously in the ICU with high-resolution near-infrared spectroscopy, and reflects the dynamic variability of hemoglobin distribution in the microcirculation. Results suggest this novel hemodynamic metric should be further evaluated for diagnosing microvascular dysfunction and monitoring peripheral perfusion. [ABSTRACT FROM AUTHOR]

Recently alginate-based tissue repair scaffolds fabricated using 3D printing techniques have been extensively examined for use in tissue engineering applications. However, their physical and mechanical properties are unfavorable for many tissue engineering applications because these properties are poorly controlled during the fabrication process. Some improvement of alginate gel properties can be realized by addition of hyaluronic acid (HA), and this may also improve the ability of cells to interact with the gel. Here, we report improvement of the physical properties of alginate–HA gel scaffolds by the addition of the polycation polyethyleneimine (PEI) during the fabrication process in order to stabilize alginate molecular structure through the formation of a polyelectrolyte complex. We find that PEI has a significant beneficial influence on alginate–HA scaffold physical properties, including a reduction in the degree of gel swelling, a reduction in scaffold degradation rate, and an increase in the Young’s modulus of the gel. Further study shows that fabrication of alginate–HA gels with PEI increases the encapsulation efficiency of bovine serum albumin, a model protein, and reduces the subsequent initial protein release rate. However, it was also found that survival of Schwann cells or ATDC-5 chondrogenic cells encapsulated during the scaffold fabrication process was modestly reduced with increasing PEI concentration. This study illustrates that the use of PEI during scaffold fabrication by plotting can provide an effective means to control alginate-based scaffold properties for tissue engineering applications, but that the many effects of PEI must be balanced for optimal outcomes in different situations. [ABSTRACT FROM PUBLISHER]

Infant hydrocephalus poses a severe global health burden; 80% of cases occur in the developing world where patients have limited access to neurosurgical care. Surgical treatment combining endoscopic third ventriculostomy and choroid plexus cauterization (ETV/CPC), first practiced at CURE Children's Hospital of Uganda (CCHU), is as effective as standard ventriculoperitoneal shunt (VPS) placement while requiring fewer resources and less post-operative care. Although treatment focuses on controlling ventricle size, this has little association with treatment failure or long-term outcome. This study aims to monitor the progression of hydrocephalus and treatment response, and investigate the association between cerebral physiology, brain growth, and neurodevelopmental outcomes following surgery. We will enroll 300 infants admitted to CCHU for treatment. All patients will receive pre/post-operative measurements of cerebral tissue oxygenation (SO2), cerebral blood flow (CBF), and cerebral metabolic rate of oxygen consumption (CMRO2) using frequency-domain near-infrared combined with diffuse correlation spectroscopies (FDNIRS-DCS). Infants will also receive brain imaging, to monitor tissue/ventricle volume, and neurodevelopmental assessments until two years of age. This study will provide a foundation for implementing cerebral physiological monitoring to establish evidence-based guidelines for hydrocephalus treatment. This paper outlines the protocol, clinical workflow, data management, and analysis plan of this international, multi-center trial. [ABSTRACT FROM AUTHOR]

R289 --> Introduction: Phenylephrine is a vasoconstrictor commonly used in cardiac surgery to increase mean arterial pressure without affecting cardiac output; however, its effects on the microcirculation of the brain and in skeletal muscle are unclear. In the current study, the timing and effects of a phenylephrine bolus on brain and skeletal muscle microvasculature were investigated using hyperspectral near infrared spectroscopy (h‐NIRS) and intravital video microscopy (IVVM. The objective of this study is to compare the effects of a timed phenylephrine bolus in the brain microvasculature, to the effects of the same bolus on the skeletal muscle microvasculature using both invasive (IVVM) and non‐invasive (h‐NIRS) methods. Methods: The IVVM system uses an inverted Olympus microscope and two Rolera XR cameras to record 20X videos of individual capillaries in the Sprague Dawley rat (n=8, 158±10g) extensor digitorum longus muscle. The h‐NIRS system uses two Ocean Insight spectrometers (MayaPro and QE65000) and an Ocean Insight HL‐2000 halogen light source. 3‐D printed probe‐holders were positioned on the left hind limb and the top of the skull, with a source‐detector distance of 10mm. Seven microvascular challenges were monitored with the h‐NIRS system by recording a two‐minute baseline, then injecting 0.1mL of phenylephrine (0.1ug/mL) or 0.1mL of saline intravenously, then collecting data for 8 minutes. The same challenges were also monitored using IVVM simultaneously, by recording 1 minute at baseline and 2 minutes post‐IV injection. One representative phenylephrine bolus was chosen for this abstract. Results: The h‐NIRS system measured a 3.75% decrease in deoxygenated hemoglobin (Hb) and a 0.87% increase in oxygenated hemoglobin (HbO) in the brain microcirculation (Fig.1A), as well as a 2.78% decrease in Hb and a 1.13% decrease in HbO the skeletal muscle microcirculation (Fig.1B) in the seconds following the phenylephrine bolus. Total hemoglobin (tHb) decreased by 2.88% in the brain and 3.91% in the skeletal muscle. Results obtained from IVVM show an increase in optical density for frequencies reflecting microvascular activity immediately following the phenylephrine bolus (Fig. 2), followed by a gradual return to baseline activity. Discussion: This is the first report of the use of h‐NIRS and IVVM to monitor the effects of phenylephrine on multiple microvascular beds in a healthy animal. Phenylephrine caused a decrease in Hb and tHb in both the brain and skeletal muscle microvasculature, but did not cause a prolonged decrease as both microvascular beds returned to baseline levels by the end of the 10‐minute collection. The same pattern was measured in the optical density (Fig. 2). Unlike Hb, HbO levels increase in the brain after the phenylephrine bolus but decrease in skeletal muscle. This may be due to the oxygen requirements of the brain. Future work includes incorporating diffuse correlation spectroscopy into the methodology to provide insight into blood flow during the vascular challenge. [ABSTRACT FROM AUTHOR]

Significance: Despite its advantages in terms of safety, low cost, and portability, functional near-infrared spectroscopy applications can be challenging due to substantial signal contamination from hemodynamics in the extracerebral layer (ECL). Time-resolved near-infrared spectroscopy (tr NIRS) can improve sensitivity to brain activity but contamination from the ECL remains an issue. This study demonstrates how brain signal isolation can be further improved by applying regression analysis to tr data acquired at a single source–detector distance. Aim: To investigate if regression analysis can be applied to single-channel trNIRS data to further isolate the brain and reduce signal contamination from the ECL. Approach: Appropriate regressors for trNIRS were selected based on simulations, and performance was evaluated by applying the regression technique to oxygenation responses recording during hypercapnia and functional activation. Results: Compared to current methods of enhancing depth sensitivity for trNIRS (i.e., higher statistical moments and late gates), incorporating regression analysis using a signal sensitive to the ECL significantly improved the extraction of cerebral oxygenation signals. In addition, this study demonstrated that regression could be applied to trNIRS data from a single detector using the early arriving photons to capture hemodynamic changes in the ECL. Conclusion: Applying regression analysis to trNIRS metrics with different depth sensitivities improves the characterization of cerebral oxygenation signals. [ABSTRACT FROM AUTHOR]

Post-hemorrhagic ventricular dilatation (PHVD) is characterized by a build-up of cerebral spinal fluid (CSF) in the ventricles, which increases intracranial pressure and compresses brain tissue. Clinical interventions (i.e., ventricular taps, VT) work to mitigate these complications through CSF drainage; however, the timing of these procedures remains imprecise. This study presents Neonatal NeuroMonitor (NNeMo), a portable optical device that combines broadband near-infrared spectroscopy (B-NIRS) and diffuse correlation spectroscopy (DCS) to provide simultaneous assessments of cerebral blood flow (CBF), tissue saturation (StO2), and the oxidation state of cytochrome c oxidase (oxCCO). In this study, NNeMo was used to monitor cerebral hemodynamics and metabolism in PHVD patients selected for a VT. Across multiple VTs in four patients, no significant changes were found in any of the three parameters: CBF increased by 14.6 ± 37.6% (p = 0.09), StO2 by 1.9 ± 4.9% (p = 0.2), and oxCCO by 0.4 ± 0.6 µM (p = 0.09). However, removing outliers resulted in significant, but small, increases in CBF (6.0 ± 7.7%) and oxCCO (0.1 ± 0.1 µM). The results of this study demonstrate NNeMo's ability to provide safe, non-invasive measurements of cerebral perfusion and metabolism for neuromonitoring applications in the neonatal intensive care unit. [ABSTRACT FROM AUTHOR]

Significance: Hyperspectral near-infrared spectroscopy (hsNIRS) combined with diffuse correlation spectroscopy (DCS) provides a noninvasive approach for monitoring cerebral blood flow (CBF), the cerebral metabolic rate of oxygen ( CMRO 2 ) and the oxidation state of cytochrome-c-oxidase (oxCCO). CMRO 2 is calculated by combining tissue oxygen saturation ( S t O 2 ) with CBF, whereas oxCCO can be measured directly by hsNIRS. Although both reflect oxygen metabolism, a direct comparison has yet to be studied. Aim: We aim to investigate the relationship between CMRO 2 and oxCCO during periods of restricted oxygen delivery and lower metabolic demand. Approach: A hybrid hsNIRS/DCS system was used to measure hemodynamic and metabolic responses in piglets exposed to cerebral ischemia and anesthetic-induced reductions in brain activity. Results: Although a linear relationship was observed between CMRO 2 and oxCCO during ischemia, both exhibited a nonlinear relationship with respect to CBF. In contrast, linear correlation was sufficient to characterize the relationships between CMRO 2 and CBF and between the two metabolic markers during reduced metabolic demand. Conclusions: The observed relationship between CMRO 2 and oxCCO during periods of restricted oxygen delivery and lower metabolic demand indicates that the two metabolic markers are strongly correlated., (© 2022 The Authors.)

This is the first multimodal study of cerebral tissue metabolism and perfusion post-hypoxic-ischaemic (HI) brain injury using broadband near-infrared spectroscopy (bNIRS), diffuse correlation spectroscopy (DCS), positron emission tomography (PET) and magnetic resonance spectroscopy (MRS). In seven piglet preclinical models of neonatal HI, we measured cerebral tissue saturation (StO 2 ), cerebral blood flow (CBF), cerebral oxygen metabolism (CMRO 2 ), changes in the mitochondrial oxidation state of cytochrome c oxidase (oxCCO), cerebral glucose metabolism (CMRglc) and tissue biochemistry (Lac+Thr/tNAA). At baseline, the parameters measured in the piglets that experience HI (not controls) were 64 ± 6% StO 2 , 35 ± 11 ml/100 g/min CBF and 2.0 ± 0.4 μmol/100 g/min CMRO2. After HI, the parameters measured were 68 ± 6% StO 2 , 35 ± 6 ml/100 g/min CBF, 1.3 ± 0.1 μmol/100 g/min CMRO 2 , 0.4 ± 0.2 Lac+Thr/tNAA and 9.5 ± 2.0 CMRglc. This study demonstrates the capacity of a multimodal set-up to interrogate the pathophysiology of HIE using a combination of optical methods, MRS, and PET.

During cardiac surgery with cardiopulmonary bypass (CPB), adequate maintenance of cerebral blood flow (CBF) is vital in preventing postoperative neurological injury - i.e. stroke, delirium, cognitive impairment. Reductions in CBF large enough to impact cerebral energy metabolism can lead to tissue damage and subsequent brain injury. Current methods for neuromonitoring during surgery are limited. This study presents the clinical translation of a hybrid optical neuromonitor for continuous intraoperative monitoring of cerebral perfusion and metabolism in ten patients undergoing non-emergent cardiac surgery with non-pulsatile CPB. The optical system combines broadband near-infrared spectroscopy (B-NIRS) to measure changes in the oxidation state of cytochrome c oxidase (oxCCO) - a direct marker of cellular energy metabolism - and diffuse correlation spectroscopy (DCS) to provide an index of cerebral blood flow (CBFi). As the heart was arrested and the CPB-pump started, increases in CBFi (88.5 ± 125.7%) and significant decreases in oxCCO (-0.5 ± 0.2 µM) were observed; no changes were noted during transitions off CPB. Fifteen hypoperfusion events, defined as large and sustained reductions in CPB-pump flow rate, were identified across all patients and resulted in significant decreases in perfusion and metabolism when mean arterial pressure dropped to 30 mmHg or below. The maximum reduction in cerebral blood flow preceded the corresponding metabolic reduction by 18.2 ± 15.0 s. Optical neuromonitoring provides a safe and non-invasive approach for assessing intraoperative perfusion and metabolism and has potential in guiding patient management to prevent adverse clinical outcomes., Competing Interests: The authors declare no conflicts of interest., (© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.)

This study presents the characterization of dynamic cerebrovascular reactivity (CVR) in healthy adults by a hybrid optical system combining time-resolved (TR) near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS). Blood flow and oxygenation (oxy- and deoxy-hemoglobin) responses to a step hypercapnic challenge were recorded to characterize dynamic and static components of CVR. Data were acquired at short and long source-detector separations ( r SD ) to assess the impact of scalp hemodynamics, and moment analysis applied to the TR-NIRS to further enhance the sensitivity to the brain. Comparing blood flow and oxygenation responses acquired at short and long r SD demonstrated that scalp contamination distorted the CVR time courses, particularly for oxyhemoglobin. This effect was significantly diminished by the greater depth sensitivity of TR NIRS and less evident in the DCS data due to the higher blood flow in the brain compared to the scalp. The reactivity speed was similar for blood flow and oxygenation in the healthy brain. Given the ease-of-use, portability, and non-invasiveness of this hybrid approach, it is well suited to investigate if the temporal relationship between CBF and oxygenation is altered by factors such as age and cerebrovascular disease., Competing Interests: The authors declare that they have no conflict of interest., (© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.)

Near-infrared spectroscopy (NIRS) is considered ideal for brain monitoring during preterm infancy because it is non-invasive and provides a continuous measure of tissue oxygen saturation (StO 2 ). Hyperspectral NIRS (HS NIRS) is an inexpensive, quantitative modality that can measure tissue optical properties and oxygen saturation (StO 2 ) by differential spectroscopy. In this study, experiments were conducted using newborn piglets to measure StO 2 across a range of oxygenation levels from hyperoxia to hypoxia by HS and time-resolved (TR) NIRS for validation. A strong correlation between StO 2 measurements from the two techniques was observed (R 2  = 0.98, average slope of 1.02 ± 0.28); however, the HS-NIRS estimates were significantly higher than the corresponding TR-NIRS values. These regression results indicate that HS NIRS could become a clinically feasible method for monitoring StO 2 in preterm infants., Competing Interests: The authors declare that there are no conflicts of interest related to this article., (© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.)

Diffuse correlation spectroscopy (DCS) is a noninvasive optical technique for monitoring cerebral blood flow (CBF). This work presents a stand-alone DCS system capable of monitoring absolute CBF by incorporating a quantitative dynamic contrast-enhanced (DCE) technique. Multi-distance data were acquired to measure the tissue optical properties and to perform DCE experiments. Feasibility of the technique was assessed in piglets in which the optical properties were measured independently by time-resolved near-infrared spectroscopy. A strong linear correlation was observed between CBF values derived using the two sets of optical properties, demonstrating that this hybrid DCS approach can provide real-time monitoring of absolute CBF., Competing Interests: The authors declare that there are no conflicts of interest related to this article., (© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.)

Preterm infants born with very low birth weights are at a high risk of brain injury, in part because the premature brain is believed to be prone to periods of low cerebral blood flow (CBF). Tissue damage is likely to occur if reduction in CBF is sufficient to impair cerebral energy metabolism for extended periods. Therefore, a neuromonitoring method that can detect reductions in CBF, large enough to affect metabolism, could alert the neonatal intensive care team before injury occurs. In this report, we present the development of an optical system that combines diffuse correlation spectroscopy (DCS) for monitoring CBF and broadband near-infrared spectroscopy (B-NIRS) for monitoring the oxidation state of cytochrome c oxidase (oxCCO) - a key biomarker of oxidative metabolism. The hybrid instrument includes a multiplexing system to enable concomitant DCS and B-NIRS measurements while avoiding crosstalk between the two subsystems. The ability of the instrument to monitor dynamic changes in CBF and oxCCO was demonstrated in a piglet model of neonatal hypoxia-ischemia (HI). Experiments conducted in eight animals, including two controls, showed that oxCCO exhibited a delayed response to ischemia while CBF and tissue oxygenation (S t O 2 ) responses were instantaneous. These findings suggest that simultaneous neuromonitoring of perfusion and metabolism could provide critical information regarding clinically significant hemodynamic events prior to the onset of brain injury., Competing Interests: The authors declare that there are no conflicts of interest related to this article.

Perinatal hypoxic ischaemic (HI) encephalopathy is associated with severe neurodevelopment problems and mortality. This study uses broadband continuous-wave near-infrared spectroscopy (NIRS) to assess the early changes in cerebral oxygenation and metabolism after HI injury in an animal model using controlled anoxia events. Anoxia was induced before and 1 h after various levels of HI injury to assess the metabolic response via the changes in the oxidation state of cytochrome-c-oxidase (oxCCO), a marker of oxidative metabolism. The oxCCO responses to anoxia were classified into five categories: increase, no change, decrease, biphasic and triphasic responses. The most common response (54%) was a biphasic decrease in oxCCO. A change in the classification of the metabolic response to anoxia after HI injury indicated a severe injury, as determined by proton magnetic resonance spectroscopy, with 86% sensitivity. This shows that broadband NIRS can identify disturbances to cerebral metabolism in the first hours after severe HI injury.

Joint hypoxia plays a central role in the progression and perpetuation of rheumatoid arthritis (RA). Thus, optical techniques that can measure surrogate markers of hypoxia such as blood flow, oxyhemoglobin, deoxyhemoglobin, and oxygen saturation are being developed to monitor RA. The purpose of the current study was to compare the sensitivity of these physiological parameters to arthritis. Experiments were conducted in a rabbit model of RA and the results revealed that joint blood flow was the most sensitive to arthritis and could detect a statistically significant difference (p<0.05, power = 0.8) between inflamed and healthy joints with a sample size of only four subjects. Considering that this a quantitative technique, the high sensitivity to arthritis suggests that joint perfusion has the potential to become a potent tool for monitoring disease progression and treatment response in RA.

Bioengineered tissue scaffolds are a potential tool for improving regenerative repair of damaged peripheral nerves. Novel modes of fabrication coupled with scaffold design strategies that are based on an understanding of the biology of nerve injury offer the prospect of intervention at a more sophisticated level. We review the etiology and incidence of peripheral nerve injury and the biological events that unfold during nerve regeneration after an injury. Newly available tissue scaffold fabrication technologies using bioplotting and laser-based techniques are described. Scaffold design strategies are also discussed, including the incorporation of living cells during scaffold fabrication, inclusion of neurotrophic gradients, use of electric stimulation, inclusion of antioxidant compounds to counteract neural apotosis, and promotion of angiogenesis. Use of these advanced fabrication techniques and incorporation of one or more of these active biological strategies may eventually lead to a greater success in peripheral nerve tissue engineering.