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. 2022 May;11(5):595-606.
doi: 10.21037/tau-22-30.

Microenergy acoustic pulse therapy restores function and structure of pelvic floor muscles after simulated birth injury

Guiting Lin  1 , Michelle Van Kuiken  1 , Guifang Wang  1 , Lia Banie  1 , Yan Tan  1 , Feng Zhou  1 , Zhao Wang  1 , Yinwei Chen  1 , Yingchun Zhang  2 , Tom F Lue  1
Affiliations

Microenergy acoustic pulse therapy restores function and structure of pelvic floor muscles after simulated birth injury

Guiting Lin et al. Transl Androl Urol. 2022 May.

Abstract

Background: The mechanisms of the microenergy acoustic pulse (MAP) therapy on restoring structure and function of pelvic floor muscles (PFM) after simulated birth injury are not well understood.

Methods: A total 24 female Sprague-Dawley rats were randomly grouped into sham control (sham), vaginal balloon dilation and ovariectomy (VBDO), VBDO + β-aminopropionitrile (BAPN, an irreversible LOX inhibitor), and VBDO + BAPN and treated with MAP (n=6 in each group). The MAP therapy was administered 2 times per week for 4 weeks with 1-week washout, the functional and histological studies were conducted in all 24 rats. The viscoelastic behavior of the PFM, including iliococcygeus (IC) and pubococcygeus (PC), was examined with a biomechanical assay. The structure of the PFM was assessed by immunofluorescence and Masson's trichrome staining.

Results: The leak point pressure (LPP) assay demonstrated that the MAP therapy group had higher LPPs compared to that of VBDO and BAPN groups. In the sham group, the muscular stiffness (K) of IC muscle was significantly higher than that of PC muscle while the pelvic floor muscle rebound activity (MRA) of PC muscle was stronger than that of IC muscle (291.26±45.33 and 241.18±14.23 N/cm2, respectively). Both VBDO and BAPN decreased the MRA and increased the K in both IC and PC. Histologic examination revealed increased fibrous tissue (collagen) and degeneration of muscle fibers in both VBDO and BAPN groups. MAP therapy significantly reduced the collagen content and improved the architecture of muscle fibers.

Conclusions: MAP appears to restore the structure and function of PFM by regenerating muscular fibers and improving biomechanical properties in an animal model of simulated birth injury.

Keywords: Microenergy acoustic pulses (MAP); pelvic floor muscles (PFM); stress urinary incontinence (SUI); vaginal balloon dilation and ovariectomy (VBDO); β-aminopropionitrile (BAPN).

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-22-30/coif). TFL serves as an unpaid Editor-in-Chief for Translational Andrology and Urology. GL serves as an unpaid Editorial Board Member from August 2020 to July 2022 for Translational Andrology and Urology. YZ is the founder and CEO of HillMed Inc. and BrainHealth Tech Inc. TFL is a consultant, co-founder and investor of Acoustic Wave Cell Therapy, Inc. The other authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Difference of muscle stiffness between PC and IC. (A) The diagram depicts the muscle fibers, endomysium, perimysium, epimysium and sarcolemma. (B) IC muscle fibers have thicker endomysium and perimysium than the PC muscle fibers (Laminin: green; Phalloidin: red; DAPI: blue). Magnification: ×100, ×200, ×400. (C) Muscle stress-relaxation curve of PC and IC in 4 groups: sham, VBDO, BAPN and MAP. Muscle stiffness of in 4 groups: sham, VBDO, BAPN and MAP. The bar chart represented the average muscle stiffness coefficient of PC and IC muscle in four groups (n=6; *, P<0.05, compared with PC; **, P<0.01). PC, pubococcygeus; IC, iliococcygeus; DAPI, 4',6-diamidino-2-phenylindole; VBDO, vaginal balloon dilation and ovariectomy; BAPN, β-aminopropionitrile; MAP, microenergy acoustic pulse.
Figure 2
Figure 2
MRA affected by MAP in rats. Average MRA of the 4 groups: sham, VBDO, BAPN and MAP in both PC and IC (n=6; *, P<0.05, compared with the sham group; **, P<0.01, compared with the VBDO and BAPN group). VBDO, vaginal balloon dilation and ovariectomy; BAPN, β-aminopropionitrile; MAP, microenergy acoustic pulse; MRA, muscle rebound activity; PC, pubococcygeus; IC, iliococcygeus.
Figure 3
Figure 3
PC muscle stiffness affected by MAP in rats. (A) The stress-relaxation curve of each PC trips in 4 groups: sham, VBDO, BAPN and MAP. (B) Merged stress-relaxation curve of each PC trips from all four groups. (C) Average PC muscle stiffness coefficient in four groups (n=6; *, P<0.05, compared with the sham group). VBDO, vaginal balloon dilation and ovariectomy; BAPN, β-aminopropionitrile; MAP, microenergy acoustic pulse; PC, pubococcygeus.
Figure 4
Figure 4
IC muscle stiffness affected by MAP in rats. (A) The stress-relaxation curve of each PC trips in 4 groups: sham, VBDO, BAPN and MAP. (B) Merged stress-relaxation curve of each PC trips from all four groups. (C) Average PC muscle stiffness coefficient in four groups (n=6; *, P<0.05, compared with the sham group; **, P<0.01). VBDO, vaginal balloon dilation and ovariectomy; BAPN, β-aminopropionitrile; MAP, microenergy acoustic pulse; IC, iliococcygeus; PC, pubococcygeus.
Figure 5
Figure 5
Effect of MAP on extracellular matrix within pelvic floor muscle. (A) Representative cross sections of PFM stained by Trichrome staining in four groups: sham, VBDO, BAPN and MAP. Magnification: ×100, ×200, ×400. (B) Representative longitude section of PFM stained by Trichrome staining in four groups. Magnification: ×100, ×200, ×400. There are more interstitial collagen fibers in both VBDO and BAPN groups. VBDO, vaginal balloon dilation and ovariectomy; BAPN, β-aminopropionitrile; MAP, microenergy acoustic pulse; PFM, pelvic floor muscles.
Figure 6
Figure 6
MAP partially restored the integrity of PFM damaged by VBDO and BAPN. Female adult rats VBDO and BAPN injections (VBDO + BAPN), with or without MAP therapy. Sham surgery was performed in the control group (sham) (n=6 in each group). The PC muscle was harvested for histology. Antibodies/chemicals used: Phalloidin for muscle (Pha, green), Laminin (Lam, red) for sarcolemma, DAPI for cell nuclei (blue). (A) Longitudinal sections of striated muscle fiber (×100). (B,C) Cross sections (×200). Deficiency of endomysium and perimysium with disorganized muscle fibers were noted in both VBDO and BAPN group while MAP partially restored the muscle integrity. DAPI, 4',6-diamidino-2-phenylindole; VBDO, vaginal balloon dilation and ovariectomy; BAPN, β-aminopropionitrile; MAP, microenergy acoustic pulse; PFM, pelvic floor muscles; PC, pubococcygeus.
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