Recombinant Human Neuregulin1-β1 Significantly Reduces Schwannoma Growth in Mice

Abstract

Objective: Schwannomas are benign tumors that arise from Schwann cells of the nerve sheath, and their management presents a significant clinical challenge, particularly in genetic conditions like NF2-related schwannomatosis (NF2-SWN). Although current treatments, including surgery, radiation, and repurposed pharmacological agents, can be effective, they are often limited by issues such as tumor recurrence and the risk of nerve function impairment. This study aims to evaluate the potential of recombinant human Neuregulin1 beta 1 (rhNRGβ1) to inhibit schwannoma growth and promote Schwann cell differentiation in preclinical models.

Methods: We investigated the therapeutic potential of rhNRGβ1, a recombinant human epidermal growth factor (EGF)-like domain of Neuregulin1 beta 1, as a growth-inhibitory agent for schwannomas. Two distinct mouse models were used to assess its efficacy, with both histological and functional endpoints analyzed.

Results: Both systemic and local administration of rhNRGβ1 resulted in a significant reduction in schwannoma tumor growth. Mechanistically, rhNRGβ1 not only inhibited tumor proliferation, but also promoted the differentiation of both proliferative and de-differentiated Schwann cells, suggesting a dual action of growth inhibition and cellular maturation.

Interpretation: These findings highlight the therapeutic potential of rhNRG1-β1 in managing schwannomas, not only by reducing tumor growth, but also by promoting the maturation and functional restoration of Schwann cells. This dual effect provides a promising avenue for novel therapeutic strategies aimed at addressing both the growth and cellular differentiation challenges associated with schwannomas in NF2-SWN and other related conditions. ANN NEUROL 2026;99:369-381.

FIGURE 1

Recombinant human Neuregulin1 beta 1 (rhNRGβ1) improves functional nerve regeneration and decreases schwannoma growth. (A) Study protocol assessing the effects of systemic rhNRGβ1 on schwannoma growth following unilateral sciatic nerve crush in Nf2flox;P0‐Cre;Nefh‐Cre mice. (B) Foot base angle (FBA) quantification in wildtype (WT) mice treated with rhNRGβ1 (WT rhNRGβ1) and Nf2flox;P0‐Cre;Nefh‐Cre mutant mice receiving saline (KO vehicle) or rhNRGβ1 (knockout [KO] rhNRGβ1). FBA baseline levels were measured before injury (week 0) and functional recovery was assessed over 8 weeks (*p < 0.05 between WT and KO vehicle; #p < 0.05 between KO vehicle and rhNRGβ1; n = 5–10 animals per genotype, mixed‐effects model [REML] for repeated measures with Tukey's multiple comparisons test; mean ± standard error of the mean). (C) Maximum sciatic nerve diameters were quantified 3 months post‐injury in the same animals. (p‐value *<0.05, **<0.01, ***<0.001, ****<0.0001). (D) Images of dissected sciatic nerves from 6‐month‐old mice show crushed nerves (top) and intact nerves (bottom). Proximal parts are on the right; distal parts on the left. SFMA = single‐frame motion analysis.

FIGURE 2

Neuropathological assessment of sciatic nerves from recombinant human Neuregulin1 beta 1 (rhNRGβ1)‐treated animals indicate Schwann cell differentiation. (A) Sciatic nerve cross sections of indicated genotypes and treatment groups 3 months after crush injury were either hematoxylin and eosin (H&E)‐stained or immunolabeled (brown color) for Schwann cell markers S100b, myelin protein zero (MPZ), the receptor tyrosine kinase ErbB2 and p75. Cell nuclei are visualized in blue. Scale bar represents 20μm. n = 2 per cohort (B) mean signal intensity (MSI) of n = 4 whole nerve sections per treatment (p‐value *<0.05, **<0.01, ***<0.001, ****<0.0001). (C,D) Immunoblot of sciatic nerve lysates. Pooled tissue from at least 5 different animals per indicated cohort was prepared from sciatic nerves 3 months after crush injury. (C) Immunoblot for myelin basic protein (MBP), c‐Jun, and GAPDH as loading control. (D) Immunoblot for receptor tyrosine kinase ErbB2 and GAPDH as loading control. [Color figure can be viewed at www.annalsofneurology.org]

FIGURE 3

Local recombinant human Neuregulin1 beta 1 (rhNRGβ1) application via absorbable collagen sponges (ACS) reduces schwannoma growth. (A) In vitro release of rhNRGβ1 from loaded sponges was measured over time by protein concentration in phosphate‐buffered saline (PBS) after 24 hours. (B) Study protocol assessed the efficacy of local rhNRGβ1 treatment on schwannoma growth post sciatic nerve crush in Nf2flox;P0‐Cre;Nefh‐Cre mice, using ACS soaked in saline (vehicle) or rhNRGβ1. (C) Foot base angle (FBA) quantification showed functional recovery in wildtype mice with saline‐loaded sponges versus Nf2flox;P0‐Cre;Nefh‐Cre mutants treated with saline or rhNRGβ1 sponges, measured over 8 weeks (*p < 0.05; 2‐way analysis of variance for repeated measures with Sidak's post hoc test; n = 6–9 per genotype; mean ± standard error of the mean). (D) Maximum sciatic nerve diameters were quantified 3 months post‐injury in the same animals. (E) Images of dissected sciatic nerves from 5‐month‐old mice show crushed (top) and intact (bottom) nerves, with proximal parts on the right. [Color figure can be viewed at www.annalsofneurology.org]

FIGURE 4

Systemic recombinant human Neuregulin1 beta 1 (rhNRGβ1) administration has no effect on dorsal root ganglion (DRG) schwannomas in Nf2flox;Postn‐Cre mutant mice. (A) Immunoblot of sciatic nerve lysates (pooled tissue from 5 different 8‐month‐old animals per indicated genotype). Immunostaining for ErbB2, Merlin (tumor suppressor protein encoded by the Nf2 gene), and GAPDH as loading control. (B) Study protocol assessing the efficacy of systemic rhNRGβ1 treatment on schwannoma growth in Nf2flox;Postn‐Cre animals. (C) DRG volume quantification of Nf2flox;Postn‐Cre mice after 3 months of rhNRGβ1 treatment. Nf2flox;Postn‐Cre mutant mice receiving intraperitoneal saline injections (vehicle ip; n = 12) were compared to mutant mice on rhNRGβ1 treatment (rhNRGβ1 ip; n = 9; mean ± standard error of the mean [SEM]; 4 DRGs analyzed per animal, 2‐tailed t test). (D) Representative image of a cross section (hematoxylin and eosin [H&E]‐stained) through a spinal ganglion of Nf2flox;Postn‐Cre animals displaying tumorous lesions (arrows) as well as DRG neurons (arrow heads). The lower image depicts a magnification of the selected area in the upper picture. Scale bars represent 50μm. (E) Fraction of tumor tissue within total tissue was quantified as area covered by tumor in relation to the total DRG area in investigated nerve sections. Nf2flox;Postn‐Cre mutant mice receiving intraperitoneal saline injections (vehicle ip; n = 6) were compared to mutants on rhNRGβ1 injections (rhNRGβ1; n = 5; mean ± SEM; 2‐tailed t test). [Color figure can be viewed at www.annalsofneurology.org]

FIGURE 5

Systemic recombinant human Neuregulin1 beta 1 (rhNRGβ1) administration reduces tumorlet burden in nerves of Nf2flox;Postn‐Cre mutant mice. (A) Tumorlet‐containing nerve sections of Nf2flox;Postn‐Cre mutant animals were either hematoxylin and eosin (H&E)‐stained or immunolabeled (brown color) for the receptor tyrosine kinase ErbB2 and myelin basic protein (MBP). Cell nuclei are visualized in blue. Arrow indicates area of neoplastic Schwann cell proliferation. Scale bar represents 20μm. (B) Tumorlet fraction in nerves was quantified as area covered by tumorlet area in relation to the total area in investigated spinal and peripheral nerve sections. Nf2flox;Postn‐Cre mutant mice receiving intraperitoneal saline injections (vehicle ip; n = 6) were compared to mutants on rhNRGβ1 injections (rhNRGβ1 ip; n = 5; mean ± SEM). (C,D) Immunoblot of pooled tissue from 8 different animals prepared from sciatic nerves, brachial nerves, trigeminal nerves, and dorsal root ganglion (DRG). Nf2flox;Postn‐Cre mutant animals received either vehicle control injections (knockout [KO] vehicle ip) or rhNRGβ1 treatment (KO rhNRGβ1 ip) over 3 months. Immunostaining for MBP, ErbB2, c‐Jun, and GAPDH as loading control. [Color figure can be viewed at www.annalsofneurology.org]