Biology subjects

Alperin, M.

Publications and source records attributed to Alperin, M..

6 recordsLinked to original sources

bioRxiv2022

Immunomodulatory Extracellular Matrix Hydrogel Mitigates Scar Formation in a Model of Tongue Fibrosis.

BackgroundWhile head and neck cancer treatment regimens, including surgical resection, irradiation, and chemotherapy, are effective at removing tumors, they lead to muscle atrophy, denervation, and fibrosis, contributing to the pathogenesis of tongue dysphagia - difficulty swallowing. Current standard of care is ineffective; we propose an alternative approach utilizing an acellular and minimally invasive biomaterial to preserve muscle content and reduce fibrosis of the tongue after injury. Here, we investigate a decellularized extracellular matrix hydrogel for the treatment of tongue fibrosis in a partial glossectomy injury model. MethodsSkeletal muscle extracellular matrix (SKM) hydrogel was fabricated by decellularizing porcine skeletal muscle tissue through established protocols. A partial glossectomy injury in the rat was used as a model of tongue fibrois, and SKM hydrogels along with saline controls were injected to the site of scarring two weeks after injury. Tissues were harvested at 3 and 7 days post-injection for gene expression analysis of immune and myogenic pathways, and at 4 weeks post-injection to evaluate histomorphological changes in skeletal muscle and scar formation. ResultsSKM hydrogel reduced scar formation and improved muscle fiber cross-sectional area in the region of injury compared to saline controls. SKM upregulated pro-regenerative immune response while downregulating pro-inflammatory response and further promoted angiogenic gene expression. ConclusionThis study demonstrates the immunomodulatory and tissue-regenerative capacity of an acellular and minimally invasive biomaterial in a rodent model of tongue fibrosis.

bioengineering↗

bioRxiv2022

Repeated birth injuries lead to pelvic floor muscle dysfunction and impairment in regeneration

ObjectivesChildbirth is a key risk factor for pelvic floor muscle (PFM) injury and dysfunction, and subsequent pelvic floor disorders (PFDs). Multiparity further exacerbates these risks. Using the pre-clinical rat model of simulated birth injury (SBI), we previously identified that an SBI leads to PFM atrophy and fibrosis. We hypothesized that multiple SBIs further overwhelm PFM regenerative capacity, leading to functionally relevant pathological alterations long-term. Study DesignRats underwent SBI and were allowed to recover for 8 weeks to undergo another SBI. Animals were sacrificed at acute, subacute, and long-term time points post-second injury (N=3-6/time point), and pubocaudalis (PCa) was harvested to assess ex vivo muscle function, histomorphological properties and gene expression. ResultsAcutely following the 1st SBI, PCa force was decreased relative to controls. At 4 weeks, PCa force was recovered and remained unchanged at 8 weeks. Similarly, lower PCa force was observed immediately after repeated SBI. In contrast to functional recovery after 1st SBI, PCa force remained lower at 4 weeks post-2nd SBI and continued to be decreased even after 12 weeks after repeated injury. Fiber size was smaller at the long-term time points after 2nd SBI compared to controls and single SBI groups. As opposed to the resolution of centralized nuclei at 8 weeks post-1st SBI, regenerating myofibers persisted even at 12 weeks post-2nd SBI. In contrast to the peak of collagen content at 4 weeks post-1st SBI, this parameter raised progressively over 12 weeks after repeated SBIs. Prolonged inflammatory response, impairment in muscle anabolism, and sustained expression of ECM remodeling genes were observed after repeated SBIs. ConclusionsRepeated birth injuries delay PFM regeneration and impair function in the pre-clinical rat model.

physiology↗

bioRxiv2021

Mechanisms governing protective pregnancy-induced adaptions of the pelvic floor muscles in the rat pre-clinical model

BackgroundThe intrinsic properties of pelvic soft tissues in women who do and do not sustain birth injuries are likely divergent, however little is known about this. Rat pelvic floor muscles undergo protective pregnancy-induced structural adaptations, sarcomerogenesis and increase in intramuscular collagen content, that protect against birth injury. ObjectivesWe aimed to test the following hypotheses: 1) increased mechanical load of gravid uterus drives antepartum adaptations; 2) load-induced changes are sufficient to protect pelvic muscles from birth injury. Study DesignIndependent effects of load uncoupled from hormonal milieu of pregnancy were tested in 3- to 4-month-old Sprague-Dawley rats randomly divided into four groups, N=5- 10/group: (1) load-/pregnancy hormones- (controls); (2) load+/pregnancy hormones-; (3) reduced load/pregnancy hormones+; (4) load+/pregnancy hormones+. Mechanical load simulating a gravid uterus was simulated by weighing uterine horns with beads similar to fetal rat size and weight. Reduced load was achieved by unilateral pregnancy after unilateral uterine horn ligation. To assess acute and chronic phases required for sarcomerogenesis, rats were sacrificed at 4 hours or 21 days post bead loading. Coccygeus, iliocaudalis, pubocaudalis and non-pelvic tibialis anterior were harvested for myofiber and sarcomere length measurements. Intramuscular collagen content was assessed using hydroxyproline assay. Additional 20 load+/pregnancy hormones- rats underwent vaginal distention to determine whether load-induced changes are sufficient to protect from mechanical muscle injury in response to parturition-associated strains of various magnitude. Data, compared using two-way repeated measures analysis of variance/pairwise comparisons, are presented as mean {+/-} standard error of mean. ResultsAcute increase in load resulted in significant pelvic floor muscle stretch, accompanied by acute increase in sarcomere length compared to non-loaded control muscles (coccygeus: 2.69{+/-}0.03 vs 2.30{+/-}0.06 {micro}m, P<0.001; pubocaudalis: 2.71{+/-}0.04 vs 2.25{+/-}0.03 {micro}m, P<0.0001; iliocaudalis: 2.80{+/-}0.06 vs 2.35{+/-}0.04 {micro}m, P<0.0001). After 21 days of sustained load, sarcomeres returned to operational length in all pelvic muscles (P>0.05). However, the myofibers remained significantly longer in load+/pregnancy hormones- compared to load- /pregnancy hormones- in coccygeus (13.33{+/-}0.94 vs 9.97{+/-}0.26 mm, P<0.0001) and pubocaudalis (21.20{+/-}0.52 vs 19.52{+/-}0.34 mm, P<0.04) and not different from load+/pregnancy hormones+ (12.82{+/-}0.30 and 22.53{+/-}0.32mm, respectively, P>0.1), indicating that sustained load induced sarcomerogenesis in these muscles. Intramuscular collagen content in load+/pregnancy hormones- group was significantly greater relative to controls in coccygeus (6.55{+/-}0.85 vs 3.11{+/-}0.47{micro}g/mg, P<0.001) and pubocaudalis (5.93{+/-}0.79 vs 3.46{+/-}0.52 {micro}g/mg, P<0.05) and not different from load+/pregnancy hormones+ (7.45{+/-}0.65 and 6.05{+/-}0.62 {micro}g/mg, respectively, P>0.5). Iliocaudalis required both mechanical and endocrine cues for sarcomerogenesis. Tibialis anterior was not affected by mechanical or endocrine alterations. Despite equivalent extent of adaptations, load-induced changes were only partially protective against sarcomere hyperelongation. ConclusionsLoad induces plasticity of the intrinsic pelvic floor muscle components that renders protection against mechanical birth injury. The protective effect, which varies between individual muscles and strain magnitudes, is further augmented by the presence of pregnancy hormones. Maximizing impact of mechanical load on pelvic floor muscles during pregnancy, such as with specialized pelvic floor muscle stretching regimens, is a potentially actionable target for augmenting pregnancy-induced adaptations to decrease birth injury in women who may otherwise have incomplete antepartum muscle adaptations. AJOG at a GlanceO_LIWhy was the study conducted? O_LITo determine the role of mechanical load, uncoupled from the hormonal milieu of pregnancy, in driving protective pregnancy-induced adaptations previously discovered in the rat pelvic floor muscles. C_LI C_LIO_LIWhat are the key findings? O_LIMechanical load, in the absence of pregnancy hormones, induces sarcomerogenesis and extracellular matrix remodeling in rat pelvic floor muscles. C_LIO_LILoad-induced adaptations are partially protective against mechanical pelvic floor muscle injury consequent to parturition-associated strains. C_LI C_LIO_LIWhat does this study add to what is already known? O_LIThe effect of sustained increased mechanical load, uncoupled from the hormonal milieu of pregnancy, on pelvic floor muscle plasticity has not been previously studied. C_LIO_LIModulating pelvic floor muscles stretch antepartum, such as with specialized pelvic floor physical therapy regimens, could be a promising approach for augmentation of protective muscle adaptations in women. C_LI C_LI

physiology↗

bioRxiv2021

The role of muscle stem cells and fibro-adipogenic progenitors in female pelvic floor muscle regeneration following birth injury

Pelvic floor muscle (PFM) injury during childbirth is a key risk factor for subsequent pelvic floor disorders that affect millions of women worldwide. Muscle stem cells (MuSCs) play a central role in the regeneration of injured skeletal muscles, where they activate, proliferate, and differentiate to assure myogenesis needed for muscle recovery. For robust regenerative function, MuSCs require the support of fibro-adipogenic progenitors (FAPs) and immune cells. To elucidate the role of MuSCs, FAPs, and immune infiltrate in female PFM regeneration, we used radiation to perturb the system and followed PFM recovery in a simulated birth injury (SBI) rat model. Non-irradiated and irradiated rats were euthanized at 3,7, 10, and 28 days after SBI; PFMs were harvested and prepared for immunohistochemistry. Cross sectional area (CSA) of all PFM myofibers 28 days after injury in irradiated animals was significantly lower relative to non-irradiated injured controls, indicating impairment of PFM recovery. Following SBI in non-irradiated animals, the number of MuSCs and FAPs expanded significantly at 7 and 3 days after injury, respectively; this expansion did not occur in irradiated animals at the same time points. CSA of embryonic myosin heavy chain (eMyHC, marker of newly regenerated myofibers) positive fibers was also significantly smaller following SBI in irradiated muscles compared to PFMs from non-irradiated injured controls at 7 days. Our results demonstrate that loss of function and decreased expansion of MuSCs and FAPs associated with irradiation results in impaired PFM recovery, signifying essential roles for MuSCs and FAPs in the regenerative process of female PFMs after birth injury. These findings can inform the identification of novel preventative and therapeutic targets and the development of new treatments for PFM dysfunction and associated pelvic floor disorders.

cell biology↗

bioRxiv2021

Pro-regenerative Extracellular Matrix Hydrogel Prevents and Mitigates Pathological Alterations of Pelvic Muscles Following Birth Injury

Pelvic floor disorders, which include pelvic organ prolapse, and urinary and fecal incontinence, affect millions of women globally and represent a major public health concern. Pelvic floor muscle (PFM) dysfunction has been identified as one of the leading risk factors for the development of these morbid conditions. Even though childbirth, specifically vaginal delivery, has been long recognized as the most important potentially modifiable risk factor for PFM injury, the precise mechanisms of PFM dysfunction following childbirth remain elusive. In this study we demonstrate that PFMs undergo atrophy and severe fibrosis in parous women with symptomatic pelvic organ prolapse compared to age-matched nulliparous cadaveric donors without history of pelvic floor disorders. These pathological alterations are recapitulated in the pre-clinical rat model of simulated birth injury. The transcriptional signature of PFMs post-injury demonstrates a sustained inflammatory response, impairment in muscle anabolism, and persistent expression of extracellular matrix (ECM) remodeling genes. Next, we evaluated the administration of acellular injectable skeletal muscle extracellular matrix hydrogel for the prevention and mitigation of these pathological alterations. Treatment of PFMs with the biomaterial either at the time of birth injury or 4 weeks post-injury reduced muscle atrophy and mitigated fibrotic degeneration. By evaluating gene expression, we demonstrate that these changes are mainly driven by the hydrogel-induced modulation of the immune response and intramuscular fibrosis, as well as enhancement of the endogenous myogenesis. This work furthers our understanding of PFM birth injury and demonstrates proof-of-concept for a new pragmatic pro-regenerative biomaterial approach for treating injured PFMs.

bioengineering↗

bioRxiv2019

Isolation of muscle stem cells from rat skeletal muscles

BackgroundMuscle stem cells (MuSCs) are involved in homeostatic maintenance of skeletal muscles and play a central role in muscle regeneration in response to injury. Thus, understanding MuSC autonomous properties is of fundamental importance for studies of muscle degenerative diseases and muscle plasticity. Rat, as an animal model, has been widely used in the skeletal muscle field, however an efficient approach for MuSC isolation through fluorescence-activated cell sorting from rat muscles has never been described. This work aims to develop and validate an effective protocol for MuSC isolation from rat skeletal muscles.\n\nMethodsTibialis anterior, gastrocnemius, diaphragm, and the individual components of the pelvic floor muscle complex (coccygeus, iliocaudalis, and pubocaudalis) were harvested from female rats and digested for isolation of MuSCs. Three protocols, employing different cell surface markers (CD106, CD56, and CD29), were compared for their ability to isolate a pure MuSC population.\n\nResultsCells obtained using the protocol that relies only on VCAM-1 (CD106) as a positive marker showed high expression of Pax7 upon isolation, ability to progress through myogenic lineage while in culture, and complete differentiation in serum deprived conditions. The protocol was further validated in other skeletal muscles proving to be reproducible.\n\nConclusionsCD106 is an efficient marker for reliable isolation of MuSCs from a variety of rat skeletal muscles.

cell biology↗