Nociceptive phenotype alterations of dorsal root ganglia neurons innervating the subchondral bone in osteoarthritic rat knee joints.

OBJECTIVE: Subchondral bone plays a role in generating knee joint pain in osteoarthritis (OA). The objective of this study was to clarify nociceptive phenotype alterations of subchondral bone afferents of the distal femur in mono-iodoacetate (MIA)-induced OA rats. METHODS: OA was induced by intra-articular injection of MIA in rats. Two different retrograde tracers were separately injected into the knee joint cavity and the subchondral bone to identify joint and subchondral bone afferents. Immunohistochemistry was used at 2 weeks (early stage) and 6 weeks (advanced stage) after MIA injection to determine the expression of nociceptive markers (calcitonin gene-related peptide (CGRP) and tyrosine receptor kinase A (TrkA)) and the soma size distribution of CGRP-immunoreactive (IR) neurons. Histological subchondral bone and cartilage damage was scored according to the Osteoarthritis Research Society International grading system. Pain-related behavior was evaluated using weight distribution and mechanical sensitivity of the hind paw. RESULTS: OA caused an up-regulation of CGRP, TrkA and enlargement of soma size of CGRP-IR neurons in both joint and subchondral bone afferents. CGRP and TrkA expression in subchondral bone afferents gradually increased over 6 weeks. Furthermore, up-regulation of CGRP and TrkA in subchondral bone afferents displayed a strong correlation with the subchondral bone damage score. CONCLUSION: Up-regulation of nociceptive markers in subchondral bone afferents correlated with subchondral bone damage, suggesting that subchondral bone is a therapeutic target, especially in the case of advanced stage knee OA. In particular, CGRP and TrkA are potentially molecular therapeutic targets to treat joint pain associated with subchondral lesions.

Predictive performance of Shock Index for postpartum hemorrhage during cesarean delivery.

BACKGROUND: The Shock Index (SI), defined as heart rate divided by systolic blood pressure, is reportedly an early surrogate indicator for postpartum hemorrhage (PPH). However, most previous studies have used clinical data of women who delivered vaginally. Therefore, we aimed to evaluate the SI pattern during cesarean delivery and determine its usefulness in detecting PPH. METHODS: This was a single-center retrospective study using the clinical data of women (n = 331) who underwent cesarean delivery under spinal anesthesia at term between 2018 and 2021. We assessed the SI pattern stratified by total blood loss and evaluated the predictive performance of each vital sign in detecting PPH (total blood loss ≥1000 mL) based on the area under the receiver operating characteristic curve (AUROC). RESULTS: At 10-15 min after delivery, the mean SI peaked between 0.84 and 0.90 and then decreased to a level between 0.72 and 0.77, which was similar to that upon entering the operating room. Among 331 women, 91 (27.5%) were diagnosed with PPH. There was no correlation between SI and total blood loss (rs = 0.02). The SI had low ability to detect PPH (AUROC 0.54, 95% confidence interval 0.47 to 0.61), which was similar to other vital signs (AUROCs 0.53-0.56). CONCLUSION: We determined the pattern of SI during cesarean delivery. We found no correlation between SI and total blood loss. Unlike in vaginal delivery, the prognostic accuracy of SI for PPH detection in cesarean delivery was low.

Increased heart rate variability correlation between mother and child immediately pre-operation.

BACKGROUND: Maternal distress would correlate with the children's mental status, thereby influencing the activity of the autonomic nervous system (ANS) of the children and mothers. We hypothesized that pre-anesthetic maternal ANS activity, when approaching close to their children's operation time, would correlate with children's ANS activity, and that the values of heart rate variability (HRV) would correlate. METHODS: We calculated maternal and children's HRVs and analyzed the relationship between the two. A total of 24 pairs of mother and child were analyzed. Maternal and children's HRVs were recorded from the night before the child's surgery to the arrival to the operation room. RESULTS: The ratios of low-frequency components (LF) to high-frequency components (HF) (LF/HF ratio) of children's and maternal HRVs obtained during the immediate pre-operative period (06:00-08:00 hours) showed a significantly, positive correlation, but no correlation was found for the LF/HF ratios obtained during the pre-operative night. CONCLUSION: The LF/HF ratios of HRV immediately before surgery in children and mothers showed a significant positive correlation.

Epidural puncture can be confirmed by the Queckenstedt-test procedure in patients with cervical spinal canal stenosis.

BACKGROUND: The loss-of-resistance test is the most popular method for identifying the epidural space, but it cannot confirm epidural puncture. Therefore, we developed a new method to confirm epidural puncture by assessing indirect changes in epidural pressure using the Queckenstedt-test procedure, which increases subarachnoid pressure by compressing the internal jugular veins. Because this new method depends on the dynamics of cerebrospinal fluid, blockade of cerebrospinal fluid flow, as with severe spinal stenosis, is predicted to reduce changes in epidural pressure. Thus, in this study, we examined the effect of spinal stenosis on the Queckenstedt-test procedure. METHODS: Epidural puncture using the loss-of-resistance test was utilized to insert an electrode in patients undergoing cervical spine surgery. Epidural pressure was monitored during bilateral compression of the internal jugular veins to confirm epidural puncture. The insertion of the electrode into the epidural space was confirmed by observation of muscle twitch evoked by electric stimulation. RESULTS: In 60 patients, epidural puncture was performed with the loss-of-resistance test; a second trial was required in 13 patients. Increased epidural pressure was observed in 57/73 trials. When increased epidural pressure was observed, epidural puncture was always successful. The sensitivity and specificity of this method was 92.0% and 100%, respectively. The positive and negative predictive values were 100% and 66.7%, respectively. CONCLUSION: An increase in epidural pressure during bilateral compression of the internal jugular veins could offer a reliable method for confirming epidural puncture in combination with the loss-of-resistance test, even if patients have potential spinal canal narrowing.

Induction and emergence behavior of children undergoing general anesthesia correlates with maternal salivary amylase activity before the anesthesia.

BACKGROUND: The parents of the children who undergo surgery experience stress during the pre-anesthetic period. Such stress influences the mental status of their children, thereby inducing their pre-anesthetic anxiety and problematic behavior at emergence. Recently, measurement of salivary biomarkers was evaluated as stress biomarkers. Especially, alpha-amylase is utilized as an excellent index for psychological stress. In the present study, we tested whether salivary amylase activity of mothers before the surgery of their children correlates with the peri-operative children's behaviors. METHODS: A total of 22 pairs of mothers and children were analyzed. Maternal salivary amylase activity was evaluated at the entrance of the operation room. The children underwent minor plastic surgery under general anesthesia, and induction and emergence behaviors were assessed. RESULTS: The higher the maternal salivary amylase activity, the severer the children's induction anxiety (r(s)=-0.667, n=22, P<0.0001), and the higher the maternal amylase activity, the severer the children's emergence agitation (r(s)=0.705, n=22, P<0.0001). CONCLUSION: Induction and emergence behaviors of children undergoing general anesthesia significantly correlated with their respective maternal salivary amylase activity during the pre-anesthetic period.

The prevalence and impact of chronic neuropathic pain on daily and social life: A nationwide study in a Japanese population.

BACKGROUND: This study marks the first epidemiological evaluation of the prevalence and burden of chronic neuropathic pain (NeP) in an Asian population. The objective of this nationwide cross-sectional study was to identify the characteristics of individuals with NeP, detect the NeP features that affect their quality of life (QOL), and demonstrate the negative effects of NeP on social and daily living as well as comorbidities including depression, anxiety and sleep disorders. METHODS: We mailed a cross-sectional, population-based epidemiological survey to a random nationwide sample of 10,000 Japanese adults over 20 years old. RESULTS: The response rate was 54.4% (2445 men, 2992 women; mean age, 53.4 years). Prevalence of chronic pain was 16.6%, and prevalence of NeP was 3.2% as detected by the PainDETECT. Participants with NeP showed significantly lower quality of life according to scores on the EuroQol-5 Dimensions scale (p < 0.001), higher levels of psychological distress on the Kessler 6-item psychological distress scale (p < 0.001), poorer sleep quality (p < 0.001), and more workdays lost (p < 0.001) than did participants without NeP. Linear regression modelling showed that widespread pain, thermal hyperalgesia and pressure-induced pain had strong associations with lower QOL, with regression coefficients of -0.046 (p < 0.001), -0.038 (p < 0.001), and -0.040 (p < 0.001), respectively. CONCLUSIONS: This study is the first to report the prevalence of NeP in an Asian population using a validated questionnaire. This study provides compelling evidence that chronic NeP is more strongly associated with poorer QOL, mental health and social well-being than CP without a neuropathic component. SIGNIFICANCE: This population-based nationwide epidemiological study revealed the prevalence, characteristics, and negative effects of chronic pain with neuropathic components in Asian society. The prevalence of neuropathic pain was 3.2% with PainDETECT.

The microRNA-23a has limited roles in bone formation and homeostasis in vivo.

Recent studies have demonstrated that some microRNAs (miRNAs) inhibit bone formation by inhibiting the translation of specific genes. Several in vitro studies have suggested that miR-23a inhibits osteogenic differentiation by suppressing the translation of Runx2, a transcription factor essential for osteoblastogenesis, and of Satb2, a member of the special AT-rich binding protein family. In the present study, we used a gain-of-function approach to determine the roles of miR-23a in bone formation and homeostasis in vivo. The miR-23a transgenic (Tg) mice grew normally and their body size and weight were similar to those of wild-type (WT) littermates. Bone structure and morphology were similar in Tg and WT mice. Furthermore, the numbers of osteoblasts and osteoclasts, as well as their activities in bone were similar between Tg and WT mice. Our results indicate that miR-23 has limited roles in bone formation and maintenance in vivo in mice.

Repeated intra-articular injections of acidic saline produce long-lasting joint pain and widespread hyperalgesia.

BACKGROUND: Synovial fluid in inflamed joint shows a drop in pH, which activates proton-gated ion channels in nociceptors. No studies have ever tried to develop and characterize acid-induced joint pain. METHODS: Rats were injected intra-articularly with pH 4.0 acidic saline twice, 5 days apart. Pain-related behaviour tests including weight-bearing asymmetry, paw withdrawal threshold and knee compression threshold were conducted. To clarify the roles of proton-gated ion channels, rats were injected intra-articularly with selective antagonists for ASIC1a, ASIC3 and TRPV1 on day 5 (before the second injection) or on day 14. Underlying peripheral and central pain mechanisms were evaluated using joint histology, interleukin-1ß concentrations in the synovium, single-fibre recording of the knee afferent and expression of phosphorylated cyclic adenosine monophosphate-responsive element-binding protein (p-CREB) in the spinal dorsal horn. RESULTS: Repeated injections of acidic saline induced weight-bearing asymmetry, decrease in paw withdrawal threshold and knee compression threshold bilaterally, which lasted until day 28. Early administration of ASIC3 antagonist reduced the bilateral and long-lasting hyperalgesia. Neither articular degeneration nor synovial inflammation was observed. C-fibre of the knee afferent was activated by acidic saline, which was attenuated by pre-injection of ASIC3 antagonist. p-CREB expression was transiently up-regulated bilaterally on day 6, but not on day 14. CONCLUSION: We developed and characterized a model of acid-induced long-lasting bilateral joint pain. Peripheral ASIC3 and spinal p-CREB played important roles for the development of hyperalgesia. This animal model gives insights into the mechanisms of joint pain, which is helpful in developing better pain treatments.

Maternal molecular hydrogen treatment attenuates lipopolysaccharide-induced rat fetal lung injury.

Maternal inflammation is associated with spontaneous preterm birth and respiratory impairment among premature infants. Recently, molecular hydrogen (H2) has been reported to have a suppressive effect on oxidative stress and inflammation. The aim of this study was to evaluate the effects of H2 on fetal lung injury caused by maternal inflammation. Cell viability and the production of interleukin-6 (IL-6) and reactive oxygen species (ROS) were examined by treatment with lipopolysaccharide (LPS) contained in ordinal or H2-rich medium (HM) using a human lung epithelial cell line, A549. Pregnant Sprague Dawley rats were divided into three groups: Control, LPS, and HW + LPS groups. Rats were injected with phosphate-buffered saline (Control) or LPS intraperitoneally (LPS) on gestational day 19 and provided H2 water (HW) ad libitum for 24 h before LPS injection (HW + LPS). Fetal lung samples were collected on day 20, and the levels of apoptosis, oxidative damage, IL-6, and vascular endothelial growth factor (VEGF) were evaluated using immunohistochemistry. The number of apoptotic cells, and levels of ROS and IL-6 were significantly increased by LPS treatment, and repressed following cultured with HM in A549 cells. In the rat models, the population positive for cleaved caspase-3, 8-hydroxy-2'-deoxyguanosine, IL-6, and VEGF was significantly increased in the LPS group compared with that observed in the Control group and significantly decreased in the HW + LPS group. In this study, LPS administration induced apoptosis and oxidative damage in fetal lung cells that was ameliorated by maternal H2 intake. Antenatal H2 administration may decrease the pulmonary mobility associated with inflammation in premature infants.

Osteopontin involvement in integrin-mediated cell signaling and regulation of expression of alkaline phosphatase during early differentiation of UMR cells.

To clarify the function of osteopontin in osteoblast differentiation, we have examined the signal transduction pathway in an osteoblastic cell line (UMR106-6) bound to osteopontin, fibronectin, vitronectin and collagen type I surfaces. This was done by investigating the production and autophosphorylation of focal adhesion kinase (FAK) and the expression of alkaline phosphatase (ALP) at the transcription level. Results suggest that osteopontin was not only responsible for the autophosphorylation of FAK but regulated the expression of ALP, which was strongly correlated with FAK activity. These results suggest that osteopontin might act as a trigger in the early differentiation of osteoblasts.

Preparation of poly(L-lactic acid) and poly(DL-lactic-co-glycolic acid) foams by use of ice microparticulates.

Biodegradable foams of poly(L-lactic acid) (PLLA) and poly(DL-lactic-co-glycolic acid) (PLGA) for tissue engineering were fabricated by a porogen-leaching technique using ice microparticulates as the porogen material. PLLA or PLGA solution in chloroform was mixed with ice microparticulates. The mixtures were frozen by being placed in molds in liquid nitrogen and freeze-dried to form the foams. Scanning electron microscopic observation of the PLLA and PLGA foams showed that evenly distributed and interconnected pore structures were formed in these foams. The porosity and surface area of the foams increased with an increase in the weight fraction of the ice microparticulates, while the median pore size remained unchanged. The pore structures of the foams could be manipulated by controlling processing variables such as the size and weight fraction of the ice microparticulates and polymer concentration.

Fabrication of microstructures in photosensitive biodegradable polymers for tissue engineering applications.

Combining the MEMS technology and biology requirements for tissue engineering, the fabrication processes of microstructured chambers and microchannels made in biodegradable photosensitive polymers are presented. The fabrication processes, based on softlithography are very fast and flexible. Various single and multistepwise microstructures could be achieved using the biodegradable polymers. Microstructures down to 50microm, which are suitable for liver reconstructs, could be fabricated. As the pCLLA acrylate photosensitive polymer has interesting property for implantable bioreactors, that is, its softness, we examined the ability of various mammalian cells to grow and spread on it. With Hep G2 cells, human umbilical blood vessel endothelial cells (HUVEC), 3T3-L1 mouse fibroblasts, static cultures could be successfully performed on single stepwise microstructures. Then, by using this photosensitive biodegradable polymer, a microstructure with simple fluidic channels is fabricated and a perfusion experiment could be carried out. Both cell cultures and perfusion experiments suggested the possibility to use the present photosensitive polymer as microfluidic supports for biodegradable bioreactors for implantation applications.

Effects of hyperbaric oxygen on procollagen messenger RNA levels and collagen synthesis in the healing of rat tendon laceration.

In the present study, we examined the effect of intermittent exposure to hyperbaric oxygen (HBO) on experimentally induced tendon laceration in the right hind limb of 56 male Wistar rats. We compared animals treated by HBO (2 atmospheres absolute [ATA] 100% O(2) x 60 min x once per day) with control animals (without HBO) at 3, 7, 14, and 28 days after wound creation. Histology, and pro-alpha1 (I) mRNA by Northern hybridization, pro-alpha1 (III) mRNA, transforming growth factor-beta1 (TGF-beta1) mRNA by RT-PCR were studied. Our results indicate the use of HBO influences the pro-a1 (I) mRNA expression. The level of pro-alpha1 (I) mRNA was especially increased at 7 14 days after laceration by HBO. These results suggest that intermittent oxygen exposure may play a significant role in collagen synthesis and be beneficial for producing the extracellular matrices in tissue engineering.

In vitro organization of biohybrid rat liver tissue incorporating growth factor- and hormone-releasing biodegradable polymer microcapsules.

To enhance the liver-specific functions of rat hepatocyte aggregates without the addition of exogenous growth factors, polylactic acid-polyglycolic acid (PLGA)/gelatin microcapsules that release insulin, dexamethasone, epidermal growth factors, and glucagon were prepared and incorporated into the hepatocyte aggregates in suspension culture. Precoating the capsules with fibronectin enhanced the incorporation of the microcapsules into the hepatocyte aggregates. In a growth factor- and hormone-free culture medium, these microcapsule-containing aggregates showed a sustained cell number and an ammonium detoxification capacity compared with two types of control culture. One was the culture of microcapsule-free aggregates with albumin-containing control capsules and the other was the culture of capsule-free aggregates that were supplied with the same factors and hormones from the culture medium at concentration levels expected from the release kinetics of the microcapsules. Our new methodology demonstrates that the performance and duration of bioartificial liver systems can be enhanced due to a more efficient maintenance of cell number by using such growth factor- and hormone-releasing microcapsules.

Formation of human fibroblast aggregates (spheroids) by rotational culture.

In the current study, we attempted to form aggregates of fibroblasts by rotationally shaking, declining fibroblast-material interactions, and augmenting cell-cell interactions. In addition, to promote cell-cell interactions, the medium was supplemented with insulin, dexamethasone, and basic fibroblast growth. Under such improved culture conditions, normal neonatal human dermal fibroblasts formed spheroidal aggregates within 1 day of rotation on a rotational shaker. The aggregates that formed had irregular shapes and were composed from only several cells after 12 h. However, they became nearly spheroidal after 24 h of shaking. The aggregates were approximately 240 microm in diameter. After 36 h of shaking, their shape became more rounded and their surfaces became smoother. No evidence of necrosis in the center of the aggregates was observed, although a small number of dead cells was scattered throughout the aggregates. After 24-36 h, aggregates of normal human fibroblasts were collected and reinoculated onto a scaffold composed of polyglycolic acid. which is used commercially as a scaffold for artificial skin, coated with collagen. The aggregates were successfully trapped to the mesh of polyglycolic acid and became attached within 24 h. Therefore, the aggregates could provide an alternative method for seeding fibroblasts to scaffold for an artificial skin, such as a mesh of polyglycolic acid.

Sequential changes of orthodromic sensory nerve action potentials induced by experimental compression of the median nerve at the wrist.

OBJECTIVE: We studied sequential waveform changes associated with a progressive conduction block to elucidate the relative vulnerability of slow versus fast conducting fibers to a focal compression. METHODS: In 12 healthy men, orthodromic compound sensory nerve action potentials (SNAPs) of the median nerve were recorded unipolarly at 4 sites over the forearm during a 30 min period of constant, localized compression of the nerve at the wrist. RESULTS: Initial findings at the compression site consisted of nearly immediate reduction in size of the negative component accompanied by progressive enlargement of the initial-positive component. Recording at 2 cm proximal to the compression and at the elbow showed no change in onset latency initially, indicating at least partial preservation of the fast conducting fibers. Amplitude also remained unchanged for about 20 min, presumably because loss of negative and positive peaks compensated each other until conduction block began to involve a greater number of the fast conducting fibers. CONCLUSIONS: The analysis of waveform changes and their time course suggests that a focal compression initially affects the slow conducting small diameter fibers. Partial conduction block gives rise to complex waveform changes depending on recording sites. A reduction in one polarity of constituent nerve fiber action potentials may enhance the other polarity of the SNAP.

Peripheral administration of an N-methyl-D-aspartate receptor antagonist (MK-801) changes dorsal horn neuronal responses in rats.

Due to the discovery of peripheral N-methyl-D-aspartate (NMDA) receptors, the effects of peripherally administrated MK-801, a non-competitive NMDA receptor antagonist, and phosphate buffered saline were tested by using the response changes of wide-dynamic range cells in the lumbar enlargement of the spinal cord in Sprague-Dawley rats. MK-801 (1 microM, 50 microl) administered directly into the subcutaneous tissue of the receptive field (n = 7), produces a reversible reduction of responses to noxious and innocuous stimuli by a peripheral action. There was no change in the responses to cutaneous stimuli following injection of phosphate buffered saline (n = 7) or following administration of MK-801 into the contralateral foot (n = 7). The present study suggests that MK-801 produces a local anesthetic like effect in the peripheral tissue.

Waveform changes due to conduction block and their underlying mechanism in spinal somatosensory evoked potential: a computer simulation. Technical note.

Based on a square-wave solid-angle analysis, a simplified mathematical model was produced for computing a sequence of potential change in a volume conductor generated by an impulse traveling along a nerve fiber. A conduction block was simulated as a phenomenon in which a depolarization wavefront stops traveling when it reaches a certain point, although the following repolarization wavefront continues to travel until it reaches the same point. The spinal somatosensory evoked potential (SSEP) was produced as an algebraic sum of simulated nerve fiber action potentials (NFAPs). With a conduction block, an NFAP that was normally triphasic showed a positive-negative diphasic wave with reduced negativity at the point of the block, diphasic waves with enhanced negativity at points immediately preceding the block, and initial-positive waves alone or abolition of any wave at points beyond the block. The absence of their terminal-positive phases paradoxically enhanced the negative peak of the spinal SSEPs in a partial block that involved only the constituent fastest fibers, because phase cancellation of the phases between the terminal-positive phases of the fastest fibers and the negative phases of the slower fibers, which normally happens, failed to occur. At the points immediately preceding the block, the identical mechanism sustained the spinal SSEP enhancement even when every fiber was included in the block. The computer model predicted that localization of the precise site of conduction block can be achieved by demonstrating an abrupt reduction in the amplitude of the spinal SSEP, which is accompanied by an increased negative wave caudally and an enhanced monophasic positive wave rostrally.