Biology subjects

Zepeda, J. L.

Publications and source records attributed to Zepeda, J. L..

2 recordsLinked to original sources

bioRxiv2025

Rat Hindlimb Amputation Model Shows Analgesia and Sexually Dimorphic Cold Hypersensitivity with Immediate Targeted Muscle Reinnervation

IntroductionTargeted muscle reinnervation (TMR) has been used clinically to reduce pain in amputees but the mechanisms producing analgesia are unknown. Here we employ rat hindlimb amputation as an appropriate model to evaluate algogenic processes affected by TMR, performed at the time of amputation in subjects of both sex. MethodsAdult male and female Sprague-Dawley rats were assigned to amputation-only or amputation + immediate TMR (iTMR). Reflexive pain behaviors (von Frey, pin, and cold hypersensitivity testing) and spontaneous pain behaviors (guarding, flinching, anhedonia from loss of sucrose preference) were assessed. Retrograde labeling distinguished sensory and motor neurons and identified nerve coaptation sites. ResultsiTMR reduced hyperalgesia and anhedonia that followed amputation. By 4 weeks, pin testing showed reduced pain responses in iTMR rats (25%) versus amputation-only (51%, p=0.01). Sucrose preference testing revealed reduced anhedonia in iTMR rats (76% vs. 43%, p=0.01). Response to cold diminished in male iTMR rats (49% vs. 100% in amputation-only males, p<0.001), but not in females. Histology showed neuroma formation in controls but not after iTMR. Both sensory and motor fibers entered the motor branch after iTMR. ConclusionsThese findings show iTMR prevents neuroma formation and provides analgesia after amputation and, while its effect on cold hypersensitivity is sexually dimorphic. This supports further investigation into TMR analgesic mechanisms, the utility of the hindlimb amputation model, and the need for sex-specific evaluations. PerspectiveUsing a rat hindlimb amputation model to evaluate iTMR, we demonstrate its potential to mitigate neuropathic pain and neuroma formation and reveal sex-specific responses to cold hypersensitivity. These findings indicate the potential clinical utility of iTMR in improving pain outcomes, potentially providing more tailored approaches to pain management in amputees.

animal behavior and cognition↗

bioRxiv2022

Follow that cell: leukocyte migration in L-plastin mutant zebrafish.

Actin assemblies are important in motile cells such as leukocytes which form dynamic plasma membrane extensions or podia. L-plastin (LCP1) is a leukocyte-specific calcium-dependent actin-bundling protein that, in mammals, is known to affect immune cell migration. Previously, we generated CRISPR/Cas9 engineered zebrafish lacking L-plastin (lcp1-/-) and reported that they had reduced survival to adulthood, suggesting that lack of L-plastin might negatively affect the immune system. To test this hypothesis, we examined the distribution and migration of neutrophils and macrophages in the transparent tail of early zebrafish larvae using cell-specific markers and an established wound-migration assay. Knockout larvae were similar to their heterozygous siblings in having equal body sizes and comparable numbers of neutrophils in caudal hematopoietic tissue at two days post-fertilization, indicating no gross defect in neutrophil production or developmental migration. When stimulated by a tail wound, all genotypes of neutrophils were equally migratory in a two-hour window. However for macrophages we observed both migration defects and morphological differences. L-plastin knockout macrophages still homed to wounds but were slower, less directional and had a star-like morphology with many leading and trailing projections. In contrast, wild type macrophages were faster, more directional, and had a more streamlined, slug-like morphology. Overall, these findings show that in larval zebrafish L-plastin knockout primarily affects the macrophage response with possible consequences for organismal immunity. Consistent with our observations, we propose a model in which cytoplasmic L-plastin negatively regulates macrophage integrin adhesion by holding these transmembrane heterodimers in a clasped, inactive form and is a necessary part of establishing macrophage polarity during chemokine-induced motility.

developmental biology↗