Galectin-1 is involved in the potentiation of neuropathic pain in the dorsal horn

Anandamide Modulates Thermal Avoidance in Caenorhabditis elegans Through Vanilloid and Cannabinoid Receptor Interplay

Understanding the endocannabinoid system in C. elegans may offer insights into basic biological processes and potential therapeutic targets for managing pain and inflammation in human. It is well established that anandamide modulates pain perception by binding to cannabinoid and vanilloid receptors, regulating neurotransmitter release and neuronal activity. One objective of this study was to demonstrate the suitability of C. elegans as a model organism for assessing the antinociceptive properties of bioactive compounds and learning about the role of endocannabinoid system in C. elegans. The evaluation of the compound anandamide (AEA) revealed antinociceptive activity by impeding C. elegans nocifensive response to noxious heat. Proteomic and bioinformatic investigations uncovered several pathways activated by AEA. Enrichment analysis unveiled significant involvement of ion homeostasis pathways, which are crucial for maintaining neuronal function and synaptic transmission, suggesting AEA's impact on neurotransmitter release and synaptic plasticity. Additionally, pathways related to translation, protein synthesis, and mTORC1 signaling were enriched, highlighting potential mechanisms underlying AEA's antinociceptive effects. Thermal proteome profiling identified NPR-32 and NPR-19 as primary targets of AEA, along with OCR-2, Cathepsin B, Progranulin, Transthyretin, and ribosomal proteins. These findings suggest a complex interplay between AEA and various cellular processes implicated in nociceptive pathways and inflammation modulation. Further investigation into these interactions could provide valuable insights into the therapeutic potential of AEA and its targets for the management of pain-related conditions.

Long Acellular Nerve Allografts Cap Transected Nerve to Arrest Axon Regeneration and Alter Upstream Gene Expression in a Rat Neuroma Model

BACKGROUND

Treatments to manage painful neuroma are needed. An operative strategy that isolates and controls chaotic axonal growth could prevent neuroma. Using long acellular nerve allograft to "cap" damaged nerve could control axonal regeneration and, in turn, regulate upstream gene expression patterns.

METHODS

Rat sciatic nerve was transected, and the distal nerve end was reversed and ligated to generate a model end-neuroma. Three groups were used to assess their effects immediately following this nerve injury: no treatment (control), traction neurectomy, or 5-cm acellular nerve allograft cap attached to the proximal nerve. Regeneration of axons from the injured nerve was assessed over 5 months and paired with concurrent measurements of gene expression from upstream affected dorsal root ganglia.

RESULTS

Both control and traction neurectomy groups demonstrated uncontrolled axon regeneration revealed using Thy1-GFP rat axon imaging and histomorphometric measures of regenerated axons within the most terminal region of regenerated tissue. The acellular nerve allograft group arrested axons within the acellular nerve allograft, where no axons reached the most terminal region even after 5 months. At 5 months, gene expression associated with regeneration and pain sensitization, including Bdnf, cfos, and Gal, was decreased within dorsal root ganglia obtained from the acellular nerve allograft group compared to control or traction neurectomy group dorsal root ganglia.

CONCLUSIONS

Long acellular nerve allografts to cap a severed nerve arrested axon regeneration within the acellular nerve allograft. This growth arrest corresponded with changes in regenerative and pain-related genes upstream. Acellular nerve allografts may be useful for surgical intervention of neuroma.

Region-Resolved Quantitative Proteome Profiling Reveals Molecular Dynamics Associated With Chronic Pain in the PNS and Spinal Cord

To obtain a thorough understanding of chronic pain, large-scale molecular mapping of the pain axis at the protein level is necessary, but has not yet been achieved. We applied quantitative proteome profiling to build a comprehensive protein compendium of three regions of the pain neuraxis in mice: the sciatic nerve (SN), the dorsal root ganglia (DRG), and the spinal cord (SC). Furthermore, extensive bioinformatics analysis enabled us to reveal unique protein subsets which are specifically enriched in the peripheral nervous system (PNS) and SC. The immense value of these datasets for the scientific community is highlighted by validation experiments, where we monitored protein network dynamics during neuropathic pain. Here, we resolved profound region-specific differences and distinct changes of PNS-enriched proteins under pathological conditions. Overall, we provide a unique and validated systems biology proteome resource (summarized in our online database painproteome.em.mpg.de), which facilitates mechanistic insights into somatosensory biology and chronic pain—a prerequisite for the identification of novel therapeutic targets.

Tissue- and cell-specific localization of galectins, β-galactose-binding animal lectins, and their potential functions in health and disease

Fifteen galectins, β-galactose-binding animal lectins, are known to be distributed throughout the body. We herein summarize current knowledge on the tissue- and cell-specific localization of galectins and their potential functions in health and disease. Galectin-3 is widely distributed in epithelia, including the simple columnar epithelium in the gut, stratified squamous epithelium in the gut and skin, and transitional epithelium and several regions in nephrons in the urinary tract. Galectin-2 and galectin-4/6 are gut-specific, while galectin-7 is found in the stratified squamous epithelium in the gut and skin. The reproductive tract mainly contains galectin-1 and galectin-3, and their expression markedly changes during the estrous/menstrual cycle. The galectin subtype expressed in the corpus luteum (CL) changes in association with luteal function. The CL of women and cows displays a "galectin switch" with coordinated changes in the major galectin subtype and its ligand glycoconjugate structure. Macrophages express galectin-3, which may be involved in phagocytotic activity. Lymphoid tissues contain galectin-3-positive macrophages, which are not always stained with the macrophage marker, F4/80. Subsets of neurons in the brain and dorsal root ganglion express galectin-1 and galectin-3, which may contribute to the regeneration of damaged axons, stem cell differentiation, and pain control. The subtype-specific contribution of galectins to implantation, fibrosis, and diabetes are also discussed. The function of galectins may differ depending on the tissues or cells in which they act. The ligand glycoconjugate structures mediated by glycosyltransferases including MGAT5, ST6GAL1, and C2GnT are important for revealing the functions of galectins in healthy and disease states.

Repeated forced swim stress prior to complete Freund's adjuvant injection enhances mechanical hyperalgesia and attenuates the expression of pCREB and ΔFosB and the acetylation of histone H3 in the insular cortex of rat

Exposure to stressors causes substantial effects on the perception and response to pain. In several animal models, chronic stress produces hyperalgesia. The insular (IC) and anterior cingulate cortices (ACC) are the regions exhibiting most reliable pain-related activity. And the IC and ACC play an important role in pain modulation via descending pain modulatory system. In the present study we examined the expression of phospho-cAMP response element-binding protein (pCREB) and ΔFosB and the acetylation of histone H3 in the IC and ACC after forced swim stress (FS) and complete Freund's adjuvant (CFA) injection to clarify changes in the cerebral cortices that affect the activity of the descending pain modulatory system in rats with stress-induced hyperalgesia. CFA injection into the hindpaw or FS (day 1, 10min; days 2-3, 20min) induced a significant increase in the expression of pCREB and ΔFosB and the acetylation of histone H3 in the IC. Quantitative image analysis showed that the numbers of ΔFosB-immunoreactivity (IR) cells in the bilateral anterior and posterior IC (AIC and PIC) were significantly higher in the CFA group (AIC R, 548.0±98.6; AIC L, 433.5±89.4; PIC R, 546.1±72.8; PIC L, 415.5±53.5) than those in the naive group (AIC R, 86.6±14.8; AIC L, 85.5±24.7; PIC R, 124.5±29.9; PIC L, 107.0±19.8, p<0.01). However the FS prior to the CFA injection enhanced the mechanical hyperalgesia and attenuated the expression of pCREB and ΔFosB and the acetylation of histone H3 in the IC. There was no significant difference in the numbers of ΔFosB-IR cells in the bilateral PIC between the FS+CFA and naive groups. These findings suggest neuroplasticity in the IC after the FS, which may be involved in the enhancement of CFA-induced mechanical hyperalgesia through dysfunction of the descending pain modulatory system.

Chronic restraint stress decreases glial fibrillary acidic protein and glutamate transporter in the periaqueductal gray matter

Stress affects brain activity and promotes long-term changes in multiple neural systems. Exposure to stressors causes substantial effects on the perception and response to pain. In several animal models, chronic stress produces lasting hyperalgesia. Postmortem studies of stress-related psychiatric disorders have demonstrated a decrease in the number of astrocytes and the level of glial fibrillary acidic protein (GFAP), a marker for astrocyte, in the cerebral cortex. Since astrocytes play vital roles in maintaining neuroplasticity via synapse maintenance and secretion of neurotrophins, impairment of astrocytes is thought to be involved in the neuropathology. In the present study we examined GFAP and excitatory amino acid transporter 2 (EAAT2) protein levels in the periaqueductal gray matter (PAG) after subacute and chronic restraint stresses to clarify changes in descending pain modulatory system in the rat with stress-induced hyperalgesia. Chronic restraint stress (6h/day for 3 weeks), but not subacute restraint stress (6h/day for 3 days), caused a marked mechanical hypersensitivity and aggressive behavior. The chronic restraint stress induced a significant decrease of GFAP protein level in the PAG (32.0 ± 8.9% vs. control group, p<0.05). In immunohistochemical analysis the remarkable decrease of GFAP was observed in the ventrolateral PAG. The EAAT2 protein level in the 3 weeks stress group (79.6 ± 6.8%) was significantly lower compared to that in the control group (100.0 ± 6.1%, p<0.05). In contrast there was no significant difference in the GFAP and EAAT2 protein levels between the control and 3 days stress groups These findings suggest a dysfunction of the PAG that plays pivotal roles in the organization of strategies for coping with stressors and in pain modulation after chronic restraint stress.

The rat intervertebral disk degeneration pain model: relationships between biological and structural alterations and pain

INTRODUCTION

Degeneration of the interverterbral disk is as a cause of low-back pain is increasing. To gain insight into relationships between biological processes, structural alterations and behavioral pain, we created an animal model in rats.

METHODS

Disk degeneration was induced by removal of the nucleus pulposus (NP) from the lumbar disks (L4/L5 and L5/L6) of Sprague Dawley rats using a 0.5-mm-diameter microsurgical drill. The degree of primary hyperalgesia was assessed by using an algometer to measure pain upon external pressure on injured lumbar disks. Biochemical and histological assessments and radiographs of injured disks were used for evaluation. We investigated therapeutic modulation of chronic pain by administering pharmaceutical drugs in this animal model.

RESULTS

After removal of the NP, pressure hyperalgesia developed over the lower back. Nine weeks after surgery we observed damaged or degenerated disks with proteoglycan loss and narrowing of disk height. These biological and structural changes in disks were closely related to the sustained pain hyperalgesia. A high dose of morphine (6.7 mg/kg) resulted in effective pain relief. However, high doses of pregabalin (20 mg/kg), a drug that has been used for treatment of chronic neuropathic pain, as well as the anti-inflammatory drugs celecoxib (50 mg/kg; a selective inhibitor of cyclooxygenase 2 (COX-2)) and ketorolac (20 mg/kg; an inhibitor of COX-1 and COX-2), did not have significant antihyperalgesic effects in our disk injury animal model.

CONCLUSIONS

Although similarities in gene expression profiles suggest potential overlap in chronic pain pathways linked to disk injury or neuropathy, drug-testing results suggest that pain pathways linked to these two chronic pain conditions are mechanistically distinct. Our findings provide a foundation for future research on new therapeutic interventions that can lead to improvements in the treatment of patients with back pain due to disk degeneration.

Involvement of descending facilitation from the rostral ventromedial medulla in the enhancement of formalin-evoked nocifensive behavior following repeated forced swim stress

In the present study we examined whether the descending facilitation from the rostral ventromedial medulla (RVM) is required for the enhancement of formalin-evoked nocifensive behavior following repeated forced swim stress. Rats were subjected to forced or sham swim stress for 3days. Withdrawal latency to noxious thermal stimuli and mechanical withdrawal threshold to von Frey filaments did not change significantly in both groups at 24h after the last stress session. The forced swim stress showed significantly enhanced nocifensive behavior to the subcutaneous administration of formalin at 2days after the last stress session (1330.1+/-62.8s), compared to the sham swim (1076+/-102.4s, p<0.05) and naive groups (825.9+/-83.2s, p<0.01). The destruction of the RVM with ibotenic acid led to prevent the enhancement of formalin-evoked nocifensive behavior in the forced swim group. These findings suggest that the descending facilitation from the RVM may be involved in the enhancement of formalin-evoked nocifensive behavior following the forced swim stress.

A role for galectin-1 in the immune response to peripheral nerve injury

Galectin-1 (Gal1) is a multi-functional protein that has key roles in organismal growth and survival. In the adult nervous system, Gal1 promotes axonal regeneration following peripheral nerve injury. Although the mechanism by which Gal1 promotes regeneration is unclear, previous reports suggested that Gal1 acts indirectly by activating macrophages. An appropriate response of macrophages is crucial for repair of injured nerves: these immune cells remove obstructive axon and myelin debris in the distal nerve. Here we establish a role for Gal1 in the accumulation of immune cells following peripheral axotomy. We used immunohistochemistry to visualize macrophages (F4/80) in wild-type (Lgals1(+/+)) and knockout (Lgals1(-/-)) mouse sciatic nerves following injury and/or manipulation of Gal1 levels. Density of F4/80 immunoreactivity, which peaks around 3 days post-injury, was decreased in Lgals1(+/+) nerves injected with Gal1 antibody. The typical injury-induced peak of macrophage/microglial density was delayed in the sciatic nerves and fifth lumbar dorsal root ganglia of Lgals1(-/-) mice relative to control mice. Injection of oxidized Gal1 into uninjured sciatic nerve promoted the accumulation of macrophages in Lgals1(+/+) nerves. Finally, we used transplants of sciatic nerve to uncover a compensatory mechanism in Lgals1(-/-) mice that allows for macrophage accumulation (albeit delayed and diminished) following axotomy. We conclude that Gal1 is necessary to direct the typical accumulation of macrophages in the injured peripheral nerve, and that Gal1 is sufficient to promote macrophage accumulation in the uninjured nerve of wild-type mice.

Physicochemical properties and oxidative inactivation of soluble lectin from water buffalo (Bubalus bubalis) brain

Lectins are carbohydrate-binding proteins present in a wide variety of plants and animals, which serve various important physiological functions. A soluble beta-galactoside binding lectin has been isolated and purified to homogeneity from buffalo brain using ammonium sulphate precipitation (40-70%) and gel permeation chromatography on Sephadex G50-80 column. The molecular weight of buffalo brain lectin (BBL) as determined by SDS-PAGE under reducing and non-reducing conditions was 14.2 kDa, however, with gel filtration it was 28.5 kDa, revealing the dimeric form of protein. The neutral sugar content of the soluble lectin was estimated to be 3.3%. The BBL showed highest affinity for lactose and other sugar moieties in glycosidic form, suggesting it to be a beta-galactoside binding lectin. The association constant for lactose binding as evidenced by Scatchard analysis was 6.6 x 10(3) M(-1) showing two carbohydrate binding sites per lectin molecule. A total inhibition of lectin activity was observed by denaturants like guanidine HCl, thiourea and urea at 6 M concentration. The treatment of BBL with oxidizing agent destroyed its agglutination activity, abolished its fluorescence, and shifted its UV absorption maxima from 282 to 250 nm. The effect of H2O2 was greatly prevented by lactose indicating that BBL is more stable in the presence of its specific ligand. The purified lectin was investigated for its brain cell aggregation properties by testing its ability to agglutinate cells isolated from buffalo and goat brains. Rate of aggregation of buffalo brain cells by purified protein was more than the goat brain cells. The data from above study suggests that the isolated lectin may belong to the galectin-1 family but is glycosylated unlike those purified till date.

Persistent monoarthritis of the temporomandibular joint region enhances nocifensive behavior and lumbar spinal Fos expression after noxious stimulation to the hindpaw in rats

Effects of persistent temporomandibular joint (TMJ) inflammation on nociceptive responses of remote bodily areas of the rat were investigated. Monoarthritis of the TMJ region was evoked by the injection of complete Freund's adjuvant (CFA) into the left TMJ region. Rats without injection of CFA into the TMJ region served as controls (non-CFA group). Time spent on licking behavior evoked by the injection of formalin into the left hindpaw and withdrawal thresholds of mechanical stimulation to both sides of the hindpaw were measured during TMJ inflammation for 3 weeks. Furthermore, expression of Fos protein in the lumbar dorsal horn was immunohistochemically investigated following the injection of formalin into the hindpaw during TMJ inflammation. Formalin-evoked nocifensive behavioral activities were significantly enhanced at 10 and 14 days after CFA injection in the late phase, while the withdrawal threshold to mechanical stimulation was significantly decreased bilaterally at 8, 10 and 14 days after CFA injection. Both formalin-evoked licking behavior and mechanical withdrawal thresholds to bilateral hindpaw at 21 days after CFA injection were similar to those in the non-CFA group. The number of Fos-positive neurons in the lumbar dorsal horn ipsilateral to the formalin injection at 1 and 7 days after CFA injection into the TMJ were similar to those in the non-CFA group; however, those were significantly increased in the laminae I-II and V-VI of the lumbar dorsal horn at 14 days after CFA injection. TMJ inflammation for 7 and 14 days alone produced a small number of Fos-expressing neurons in the lumbar dorsal horn. These results provide evidence that persistent unilateral inflammation of the TMJ region causes an increase in behavioral hyperalgesia of the hindpaw, which is attributed to the modulation of neural activities, in part, in the lumbar dorsal horn, likely mediated by supraspinal neural mechanisms.

Investigation of early protein changes in the urinary bladder following partial bladder outlet obstruction by proteomic approach

We investigated the pathophysiological mechanism by proteomic approach as a possible tool to detect the marker proteins to develop lower urinary tract symptoms following bladder outlet obstruction (BOO). Rats were randomized into 3 groups; control, sham operation and BOO groups. BOO group was divided into 1, 3, and 5 day-group. Conventional proteomics was performed with high resolution 2-D gel electrophoresis followed by computational image analysis and protein identification using mass spectrometry using rat urinary bladders. A comparison of bladder of BOO group with control bladder showed that three proteins of optineurin, thioredoxin and preprohaptoglobin were over-expressed in the bladder of BOO group. In addition, four proteins, such as peroxiredoxin 2, transgelin, hippocampal cholinergic neurostimulating peptide (HCNP) and beta-galactoside-binding lectin, were under-expressed in the bladder of BOO group. These data supported that downregulation of HCNP might make detrusor muscle be supersensitive to acetylcholine, up-regulation of optineurin means the protection of nerve injury, and down-regulation of transgelin means the decreased contractility of detrusor muscle. Beside these proteins, other proteins are related to oxidative stress or have a nonspecific function in this study. However more information is needed in human bladder tissue for clinical usage.

Regulation of neuronal and glial galectin-1 expression by peripheral and central axotomy of rat primary afferent neurons

Galectin-1 (Gal1) is an endogenously-expressed protein important for the embryonic development of the full complement of primary sensory neurons and their synaptic connections in the spinal cord. Gal1 also promotes axonal regeneration following peripheral nerve injury, but the regulation of Gal1 by axotomy in primary afferent neurons has not yet been examined. Here, we show by immunohistochemistry and in situ hybridization that Gal1 expression is differentially regulated by peripheral nerve injury and by dorsal rhizotomy. Following peripheral nerve injury, the proportion of Gal1-positive DRG neurons was increased. An increase in the proportion of large-diameter DRG neurons immunopositive for Gal1 was paralleled by an increase in the depth of immunoreactivity in the dorsal horn, where Gal1-positive terminals are normally restricted to laminae I and II. Dorsal rhizotomy did not affect the proportions of neurons containing Gal1 mRNA or protein, but did deplete the ipsilateral dorsal horn of Gal1 immunoreactivity, indicating that it is transported centrally by dorsal root axons. Dorsal rhizotomy also resulted in an increase in Gal1 mRNA the nerve peripheral to the PNS-CNS interface (likely within Schwann cells and/or macrophages), and to a lesser extent within deafferented spinal cord regions undergoing Wallerian degeneration. This latter increase was notable in the dorsal columns and along the prior trajectories of myelinated afferents into the deeper dorsal horn. These results show that neuronal and glial expressions of Gal1 are tightly correlated with regenerative success. Thus, the differential expression pattern of Gal1 following peripheral axotomy and dorsal rhizotomy suggests that endogenous Gal1 may be a factor important to the regenerative response of injured axons.

Altered primary afferent anatomy and reduced thermal sensitivity in mice lacking galectin-1

The transmission of nociceptive information occurs along non-myelinated, or thinly myelinated, primary afferent axons. These axons are generally classified as peptidergic (CGRP-expressing) or non-peptidergic (IB4-binding), although there is a sub-population that is both CGRP-positive and IB4-binding. During neuronal development and following injury, trophic factors and their respective receptors regulate their survival and repair. Recent reports also show that the carbohydrate-binding protein galectin-1 (Gal1), which is expressed by nociceptive primary afferent neurons during development and into adulthood, is involved in axonal pathfinding and regeneration. Here we characterize anatomical differences in dorsal root ganglia (DRG) of Gal1 homozygous null mutant mice (Gal1(-/-)), as well as behavioural differences in tests of nociception. Gal1(-/-) mice have a significantly reduced proportion of IB4-binding DRG neurons, an increased proportion of NF200-immunoreactive DRG neurons, increased depth of central terminals of IB4-binding and CGRP-immunoreactive axons in the dorsal horn, and a reduced number of Fos-positive second order neurons following thermal (cold or hot) stimulation. While there is no difference in the total number of axons in the dorsal root of Gal1(-/-) mice, there are an increased number of myelinated axons, suggesting that in the absence of Gal1, neurons that are normally destined to become IB4-binding instead become NF200-expressing. In addition, mice lacking Gal1 have a decreased sensitivity to noxious thermal stimuli. We conclude that Gal1 is involved in nociceptive neuronal development and that the lack of this protein results in anatomical and functional deficits in adulthood.

Increase of galanin-like immunoreactivity in rat hypothalamic arcuate neurons after peripheral nerve injury

Galanin and galanin receptors are widely distributed within the central nervous system, and may play important roles in pain signaling and modulation. In the present study, we examined the galanin immunoreactivity (IR) in the hypothalamus and the amygdala following peripheral nerve injury. Four weeks after the operation, the ipsilateral mechanical threshold in the spared nerve injury (SNI) group (0.87 +/- 0.33 g) was significantly lower than that in the sham group (12.53 +/- 3.41 g; P < 0.05). In the SNI group, the number of galanin-IR neurons per section in the arcuate nucleus (Arc) of the hypothalamus was 10.2 +/- 1.7, significantly higher than that in the sham group (5.6 +/- 1.0; P < 0.05). These data suggest that the galanin-ergic neurons in the Arc may be involved in the functional modulation of descending pain modulation system following peripheral nerve injury.

Galectin-1β, a natural monomeric form of galectin-1 lacking its six amino-terminal residues promotes axonal regeneration but not cell death

We previously identified a novel N-terminally processed form of galectin-1, galectin-1beta (Gal-1beta) whose expression was induced by DeltaFosB. In the present study, the biochemical properties and biological functions of Gal-1beta were compared with the full-length form of galectin-1 (Gal-1alpha). We first purified recombinant mouse Gal-1alpha and beta (rmGal-1alpha, beta) to near homogeneity. The rmGal-1alpha exists as a monomer under oxidized conditions and forms a dimer under reduced conditions, while the rmGal-1beta exists as a monomer regardless of redox conditions. The affinity of rmGal-1beta to beta-lactose was approximately two-fold lower than that of rmGal-1alpha under reduced conditions. The viability of Jurkat cells efficiently decreased when they were exposed to rmGal-1alpha, however, rmGal-1beta barely induced such a reduction. In contrast, both rmGal-1alpha and rmGal-1beta exhibited an equivalent capacity to promote axonal regeneration from the dorsal root ganglion explants. Our results suggest that the biochemical properties of rmGal-1beta determine its biological functions.

Galectin-1 expression correlates with the regenerative potential of rubrospinal and spinal motoneurons

Axotomized spinal motoneurons are able to regenerate to their peripheral targets, whereas injured rubrospinal neurons that lie completely within the CNS fail to regenerate. The differing cell body reactions to axotomy of these two neuronal populations have been implicated in their disparate regenerative ability. Recently, the lectin galectin-1 has been shown to be involved in both spinal motoneurons and primary afferent regeneration. Using in situ hybridization, we compared the endogenous galectin-1 mRNA expression in spinal motoneurons and rubrospinal neurons after axotomy. We found that 7 and 14 days after axotomy, galectin-1 mRNA increased in spinal motoneurons but decreased in rubrospinal neurons. Infusion of the brain-derived neurotrophic factor into the vicinity of the injured rubrospinal nucleus, which we have previously shown to increase the regenerative capacity of rubrospinal neurons, significantly increased galectin-1 mRNA compared with uninjured control levels. Thus, the expression of galectin-1 in neurons correlates with the regenerative propensity.