Secreted acid sphingomyelinase as a potential gene therapy for limb girdle muscular dystrophy 2B
Daniel C. Bittel, … , Jack H. Van der Meulen, Jyoti K. Jaiswal
Daniel C. Bittel, … , Jack H. Van der Meulen, Jyoti K. Jaiswal
Published January 4, 2022
Citation Information: J Clin Invest. 2022;132(1):e141295. https://doi.org/10.1172/JCI141295.
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Research Article Muscle biology

Secreted acid sphingomyelinase as a potential gene therapy for limb girdle muscular dystrophy 2B

Abstract

Efficient sarcolemmal repair is required for muscle cell survival, with deficits in this process leading to muscle degeneration. Lack of the sarcolemmal protein dysferlin impairs sarcolemmal repair by reducing secretion of the enzyme acid sphingomyelinase (ASM), and causes limb girdle muscular dystrophy 2B (LGMD2B). The large size of the dysferlin gene poses a challenge for LGMD2B gene therapy efforts aimed at restoring dysferlin expression in skeletal muscle fibers. Here, we present an alternative gene therapy approach targeting reduced ASM secretion, the consequence of dysferlin deficit. We showed that the bulk endocytic ability is compromised in LGMD2B patient cells, which was addressed by extracellularly treating cells with ASM. Expression of secreted human ASM (hASM) using a liver-specific adeno-associated virus (AAV) vector restored membrane repair capacity of patient cells to healthy levels. A single in vivo dose of hASM-AAV in the LGMD2B mouse model restored myofiber repair capacity, enabling efficient recovery of myofibers from focal or lengthening contraction–induced injury. hASM-AAV treatment was safe, attenuated fibro-fatty muscle degeneration, increased myofiber size, and restored muscle strength, similar to dysferlin gene therapy. These findings elucidate the role of ASM in dysferlin-mediated plasma membrane repair and to our knowledge offer the first non–muscle-targeted gene therapy for LGMD2B.

Authors

Daniel C. Bittel, Sen Chandra Sreetama, Goutam Chandra, Robin Ziegler, Kanneboyina Nagaraju, Jack H. Van der Meulen, Jyoti K. Jaiswal

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Figure 6

Single dose of liver-targeted hASM-AAV improves muscle histology and function in LGMD2B model.

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Single dose of liver-targeted hASM-AAV improves muscle histology and fun...
(A) H&E-stained image of quadriceps (rectus femoris) muscle cross sections of B6A/J mice after treatment with a single intravenous dose of control-AAV or hASM-AAV (arrowheads mark inflammatory foci). (B) Images showing rectus femoris muscle cross sections labeled using anti-laminin antibodies (green) and DAPI (blue) to visualize basement membrane and myonuclei, respectively. (C) Plot showing quantification of inflammatory foci in the quadriceps (rectus femoris) muscle cross section similar to those shown in panel A (n = 5 mice per group). (D) Plot showing quantification of centrally nucleated myofibers across the rectus femoris muscle as shown in panel A, expressed as percentage of total fibers. (E) Distribution of myofiber cross-sectional areas across the entire quadriceps (n = 3,000 fibers per group). (F) Images and (G) quantification of Masson’s trichrome staining of the rectus femoris muscle cross section (n = 5 per group). (H) Quantification of forelimb grip strength of mice treated as indicated, with the contractile force normalized to body weight (n = 5 mice per group, average of 5 repeat measures per mouse. (I) Images and (J) quantification of perilipin-positive area in the rectus femoris muscle cross section (red, perilipin; green, WGA). (K) Quantification of hindlimb grip strength of mice treated as in panel H. Data are presented as mean ± SEM. *P < 0.05 (hindlimb) vs. control-AAV (forelimb, P > 0.05). Scale bars: 100 μm (A and I) and 200 μm (B and F). Data were assessed via independent samples t test (C, D, and G–K) or Mann-Whitney U test (E), with α set at P < 0.05.