京都大学 / 0048 / 新制・課程博士 / 博士(人間健康科学) / 甲第17981号 / 人健博第10号 / 新制||人健||1(附属図書館) / 80825 / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 坪山 直生, 教授 椎名 毅, 教授 松田 秀一 / 学位規則第4条第1項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

No description available.

Ribosomes are the essential machinery for cellular protein synthesis. Ribosome content is hypothesized to support muscle growth and is suggested that those with more ribosomes may better respond to resistance training. Aerobic training also elicits distinct physiological adaptations; however, no direct measures of ribosome content following aerobic training have been measured. Ribosomes interact with mitochondria for mitochondrial protein synthesis and import. Mitochondria may also provide cellular energy to ribosomes. We hypothesized that aerobic and resistance training would increase ribosome content and that ribosome content following aerobic training would correspond to changes in mitochondrial-related protein content and gene expression. Fourteen young men and women performed 6 weeks of single-legged aerobic followed by 10 weeks of bilateral resistance training. Muscle biopsies were taken following aerobic (Pre RT) and resistance training (Post RT) in the aerobically trained (EX) and control (CTL) legs. Pre RT, EX had greater COXIV staining intensity in Type 1 (1.17-fold; p=0.020) and Type 2 (1.22-fold; p=0.015) fibres compared to CTL; however, no differences in whole-muscle mitochondrial-related protein content or gene expression were observed (p>0.05). No differences in regulatory (UBF, Cyclin D1, TIF-1A, POLR-1B), cytosolic (45S, 5.8S, 18S, 28S rRNAs) or mitochondrial (12S rRNA) ribosome-related gene expression were observed (p>0.05), except for c-Myc (CTL>EX; p=0.034) and 5S rRNA (Pre RT CTL<Pre RT EX; p=0.076). When stratified for leg-lean soft tissue mass (LLSTM), legs with greater LLSTM had lower expression in 3/13 ribosome-related genes (p<0.10). When stratified for ΔLLSTM following resistance training, legs with the greatest ΔLLSTM had lower expression in 11/13 ribosome-related genes prior to (p<0.10) and less change or decrease in expression in 9/13 genes following resistance training (p<0.05). These results indicate that baseline ribosome content was sufficient to support aerobic adaptations (capillarization, VO2 peak) that were previously observed and that ribosome’s efficiency, rather than content, is likely more important to support increases in muscle hypertrophy following resistance training. / Thesis / Master of Science in Kinesiology / Ribosomes are essential in making proteins within the cell, and their content has been hypothesized to support the adaptive responses observed with exercise training. Ribosome content has previously been shown to increase following resistance training likely to support skeletal muscle growth. However as aerobic training also influences cellular adaptations, it is plausible that ribosome content also supports these training adaptations. We hypothesized that both aerobic and resistance training would increase ribosome content. Contrary to our hypotheses, no changes in ribosome content were observed following aerobic or resistance training despite previously observing adaptations characteristic of each respective training stimulus. However, those with the greatest increases in muscle mass had lower baseline ribosome content and less change in content following resistance training. These results suggest that baseline ribosome content is sufficient for aerobic adaptations and that ribosome’s efficiency is likely more important than content to elicit resistance training adaptations.

No description available.

Airway remodeling in asthma includes alterations in extracellular matrix and airway smooth muscle (ASM) mass. For this study, ASM cells were obtained from rats that were challenged with ovalbumin (OVA) or saline (SAL) as control. OVA and SAL cells were seeded on plastic control (PC) or on plates coated with decorin or biglycan. OVA cell number was significantly increased versus SAL cells, for cells seeded on PC (48 h). A significant decrease in cell number was observed for both OVA and SAL cells seeded on decorin compared to PC cells (48 h). OVA cells, however, showed a more modest reduction in cell number. Furthermore, biglycan decreased SAL cell number only. Compared to no strain (NS), mechanical strain (S) reduced cell number for OVA and SAL cells on all matrices. In addition, S up-regulated expression of beta 1-integrin relative to NS controls. Results suggest an ability of ASM cells to be modulated by matrix and mechanical stimulation.

No description available.

隨著全球人口老化、普遍的久坐生活方式及外太空技術的迅速發展，肌肉廢用已成為日益嚴峻及影響廣泛的公共健康問題。 肌肉廢用可引起肌肉萎縮及肌肉收縮功能衰退，最終影響患者的日常活動能力及生活的獨立性。 此外，重新使用廢用肌肉可引起肌纖維破壞及肌肉功能進一步損失，使得肌肉萎縮問題更加惡化。 低幅高頻振動治療屬於非入侵性的生物物理治療方法，通過給予溫和的全身性機械刺激達到治療目的，被証實可有效強化肌肉功能及刺激肌纖維肥大，為進行有關低幅高頻振動應用於廢用性肌肉萎縮治療的復康研究提供了充足證據。 本研究科研假說為低幅高頻振動治療能通過調節肌纖維形態及激活具生肌能力的肌衛星細胞，以改善廢用性萎縮肌肉收縮功能及促進其康復。 本研究共分為三個部分第1部分是對大鼠懸尾模型引發後肢廢用性肌肉萎縮進行驗證（TS模型）第2部分是研究低幅高頻振動治療對肌肉收縮功能的作用第3部分是振動治療對肌纖維型態及肌肉衛星細胞的影響。 / 第1部分的研究中，十二隻6月齡雄性SD大鼠被隨機分成懸尾組 (TS, n=6)及對照組 (Nor, n=6)。 在懸尾二十八天後，大鼠的比目魚肌被收取並進行體外肌肉功能檢測。 結果顯示懸尾組的肌肉質量及肌纖維橫切面積均顯著下降 (p<0.001)，證明懸尾模型能導致廢用性肌肉萎縮。 功能檢測顯示肌肉收縮功能下降，包括抽搐峰力及最大強直力下降（p=0.011及 p<0.001）。 因此，大鼠懸尾模型可用於研究低幅高頻振動治療對肌肉重用康復過程的作用，即本研究的第2及第3部分。 / 為了驗證本研究的科研假說，七十二隻雄性SD大鼠懸尾28天誘導比目魚肌萎縮後被隨機分為振動治療組 (Vib, n=36) 及重用對照組 (Ctrl, n=36)，並於懸尾後的第7、14 及21天取比目魚肌作進一步實驗 (n=6/組/時間點)。 治療組的大鼠於懸尾後接受每星期5天、每天20分鐘的低幅高頻振動治療 (振幅: 0.6g、頻率: 35Hz)直至對應的實驗時間點，而對照組大鼠則如常在籠中活動，其餘條件均相同。 / 第2部分實驗是通過體外肌肉功能檢測系統，分析低幅高頻振動治療對廢用萎縮後重用肌肉收縮功能的作用。 實驗結果顯示，相對於在第7天時的最大強直力，對照組重用肌肉在21天的康復期間肌力增長32% 。 振動治療組中，相對於振動治療7天時的最大強直力，振動治療14天已能夠使重用肌肉得到相近 (34.6%) 力量增長（p=0.033）。 由於兩組在第七天時的最大強直力量並沒有明顯差別，故結果可證明振動治療能提高肌強直力的恢復速度。具體肌肉強直力量(以肌纖維橫切面積常化的肌肉強直力量) 亦能夠證明有關發現。 振動治療組比目魚肌的具體強直力在振動治療14天後大於同期對照組力量 (p=0.001)。 振動治療組的具體強直力在14天時已達到最高並相近於21天時的水平，但對照組於14天至21天時仍有著明顯的上升趨勢，顯示振動治療組的肌肉完全康復速度比對照組的快。 / 第3部分實驗是探討低幅高頻振動治療，對廢用性萎縮肌肉重用過程中的肌纖維肥大及肌衛星細胞激活的作用。 為標記重用過程中激活的肌衛星細胞，本部分的每一隻大鼠處死前14天在皮下植入一顆5-溴氧尿嘧啶核苷 (BrdU) 的緩釋顆粒 (0.22亳克BrdU/ 千克/ 天)。 大鼠比目魚肌在相應實驗時間點離體迅速冷凍後進行低溫橫截切片(厚度: 7微米)。 以肌球蛋白三磷酸腺苷酶染色方法把肌肉切片染色後，即可進行肌纖維的種類及形態學分析。 第21天時，振動治療組的快肌IIB 型纖維橫切面積大於對照組，表明振動治療能刺激快肌IIB 型纖維肥大 (p=0.031)。 此外，快肌IIB 型肌纖維橫切面積與肌強直力是呈正相關的，說明低幅高頻振動治療所加快的肌強直力量康復可能是通過刺激快肌IIB 型肌纖維肥大所致。 振動治療引發的慢肌纖維轉型至快肌纖維的潛能可能被重用所致的快至慢轉型所掩蓋。 從另一角度說明，肌肉重用所導致的快肌纖維轉型至慢肌纖維過程，不受振動治療的影響。 激活的肌衛星細胞則通過5-溴氧尿嘧啶核苷標記方法，以免疫熒光技術進行顯微檢測及分析。 振動治療組肌衛星細胞普遍多於對照組，刺激效果在快肌IIA 型肌纖維中表現更為明顯。 對照組廢用肌肉重用過程中，快肌IIA 型肌纖維中激活的肌衛星細胞數量呈下降趨勢，治療組的卻比對照組高並呈持續上升趨勢。 肌衛星細胞的數量亦發現與肌纖維橫切面積呈正相關。 肌衛星細胞的其中一項主要功能為肌肉修補及康復，有關實驗結果表明，振動治療可能通過激活更多衛星細胞以提高肌肉功能及刺激肌纖維肥大。 / 綜上所述，本研究探討了低震高頻振動治療對廢用性萎縮肌肉的收縮功能、康復過程及其機理的影響。 較佳的肌肉力量產生能力及較大面積的快肌IIB 型纖維，表明了振動治療可促進廢用性萎縮肌肉康復。根據快肌IIA型纖維衛星細胞數量以及活化的衛星細胞同肌纖維橫切面積之間的相關性研究結果，可以推測震動治療促進肌肉修復的可能機理是促進肌衛星細胞的活化。 本研究為低幅高頻振動治療的進一步臨床實驗及未來在快肌纖維相關的肌肉老化問題研究，提供了可靠及充分的依據。 / Muscle disuse becomes a public health issue due to increasing aged population, prevalent sedentary lifestyles and rapidly growing outer space development. It results in muscle atrophy, contractile function loss and ultimately affects the daily life activities. The pathological conditions are even worse off during reloading because of the resulting muscle fiber damages and further functional deterioration. Low-magnitude high-frequency vibration (LMHFV), a biophysical modality providing a mild, non-invasive and systemic mechanical stimulation, has been reported to improve muscle functions and stimulate muscle hypertrophy. In this study, we hypothesized that LMHFV improved the functional outcomes and recovery of disuse-induced atrophied muscle through modulating muscle fiber morphology and activating myogenic satellite cells. The study was divided into three parts: Part 1 for validation of the tail suspension hindlimbs unloading animal model (TS model); Part 2 for testifying the LMHFV effect on functional outcomes; Part 3 for the effects on fiber morphology and satellite cells. / In Part 1 study, twelve 6-month-old male Sprague Dawley (SD) rats were randomly assigned to tail suspension control group (TS, n=6) and normal control group (Nor, n=6). Rats in TS group were tail-suspended for 28 days and of the harvested soleus muscle (Sol) was subjected to the in vitro muscle functional assessment. Muscle atrophy in TS group was confirmed by the significant decrease of Sol muscle mass (Mm) and fiber cross-sectional area (FCSA) (both p<0.001). Functionally, weakening of contractile forces including peak of twitch force (Pt) and maximum tetanic force (Po) were observed in TS (p=0.011 and p<0.001 respectively). The established animal model was used to study the effects of LMHFV on muscle reloading recovery in Part 2 and 3. / To testify the hypothesis, a total of 72 male SD rats with Sol atrophy induced by 28-day TS were used for Part two (n=36) and Part three studies (n=36). In each part of the studies, the rats were randomized into LMHFV treatment group (Vib) and reloading control group (Ctrl), from which Sol were harvested at Day 7, 14 and 21 post-TS (n=6/group/timepoint). The LMHFV treatment (0.6g, 35Hz) was applied to Vib group 20min per day and 5 days per week until the endpoint while Ctrl rats were allowed free-cage movement. / In Part 2 study, the effects of LMHFV on contractile functional outcomes of reloading muscle following TS were evaluated by in vitro muscle functional test. In Ctrl group, 32% increase of Po was found at day 21 when compared with that at day 7. A similar recovery level was already achieved in Vib group by 14 days of treatment; when compared with Vib-Day7, a 34.6% increase of Po was found at day 14 (p=0.033). Specific Po (Po normalized by FCSA) in Vib was significantly larger than Ctrl at day 14 (p=0.001). Plateau of specific Po was observed at day 14 in Vib group while significant increase was observed in Ctrl group from day 14 to day 21. These findings suggested the facilitated recovery of force generating capacity in Sol by LMHFV treatment. / In Part 3 study, the effects of LMHFV on muscle fiber hypertrophy and fiber type transition during reloading as well as on muscle satellite cells (SC) activation were assessed. In order to label activated SC, a bromodeoxyuridine (BrdU) time release pellet (0.22mg BrdU/ kg body mass/ day) was subcutaneously implanted to every rat 14 days before execution. In order to evaluate the fiber morphology and fiber type transition, Sol were harvested at corresponding endpoints and cryosectioned (cross-sections at 7μm) for ATPase staining. The bromodeoxyuridine (BrdU)-labeled activated SCs were revealed on the cryosections by immunofluorescence method. Results showed that fast-twitch type IIB muscle fiber hypertrophy was stimulated by LMHFV with type IIB fiber cross-sectional area (FCSA) in Vib group significantly larger than Ctrl at day 21 (p= 0.031). Interestingly, the type IIB FCSA was positively correlated with the Po measured, which suggested the possible contribution of stimulated type IIB muscle fiber hypertrophy for improving contractile force in Vib. The potential slow-to-fast fiber type transition induced by LMHFV might be masked by reloading-induced fast-to-slow transition in Sol. In other words, the normal fiber type transition in Sol during reloading was not affected by LMHFV. In SC activation assessment, more BrdU-labeled SCs were observed in Vib group. Particularly in fast twitch type IIA muscle fibers, the SC counts were increasing throughout the treatment period. It suggested the specific stimulatory effect of LMHFV on activation of fast twitch fiber SCs. Since SC activation is important for muscle recovery, the current finding suggested the possible contribution of increased SC activation to muscle fiber hypertrophy in response to LMHFV treatment. It was in fact evident from the positive association between SC counts and muscle FCSA found in this study. / In conclusion, LMHFV was beneficial to muscle disuse recovery, as indicated from higher force generating capacity and larger fast twitch type IIB fiber FCSA. The possible mechanism was to stimulate myogenic SC activation for muscle repair, as evident from the elevated fast twitch type IIA fiber SC counts and the association of activated SC counts to fiber FCSA. This study suggests the beneficial effects of LMHFV on muscle disuse rehabilitation and also justifies the future clinical trials on rehabilitation of bed-rest patients. The profound effects of LMHFV specifically on fast-twitch fibers provided solid basis for further study on treating the loss of fast-twitch type II fibers in muscle aging (i.e. sarcopenia). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Sun, Keng Ting. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 113-130). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Thesis/Assessment Committee --- p.ii / Abstract --- p.iii / 論文摘要 --- p.vii / Publications --- p.x / Acknowledgement --- p.xi / List of Abbreviations --- p.xiii / Figure Index --- p.xvi / Table Index --- p.xvii / Chapter Chapter 1 --- Introduction and Literature Review --- p.1 / Chapter 1.1 --- Skeletal Muscle --- p.1 / Chapter 1.1.1 --- Muscle Structure and Organization --- p.1 / Chapter 1.1.2 --- Muscle Diversity --- p.5 / Chapter 1.1.3 --- Muscle Contraction and Relaxation --- p.7 / Chapter 1.1.4 --- Muscle Plasticity --- p.10 / Chapter 1.1.5 --- Muscle Mechanosensitivity and Mechanotransduction --- p.13 / Chapter 1.1.6 --- Muscle Satellite Cells --- p.16 / Chapter 1.2 --- Muscle Disuse and Rehabilitation --- p.17 / Chapter 1.2.1 --- Epidemiology and Impact of Muscle Disuse --- p.17 / Chapter 1.2.2 --- Effects of Disuse on Muscle Structure and Contractile Function --- p.18 / Chapter 1.2.3 --- Rehabilitation of Disused Muscle --- p.21 / Chapter 1.2.4 --- Countermeasures for Muscle Disuse --- p.22 / Chapter 1.2.5 --- Muscle Disuse Animal Models - Tail Suspension Hindlimbs Unloading Model --- p.23 / Chapter 1.3 --- Low-Magnitude High-Frequency Vibration Intervention --- p.24 / Chapter 1.3.1 --- Stimulatory Effects of Vibration on Muscle --- p.25 / Chapter 1.4 --- Hypothesis and Objectives --- p.27 / Chapter Chapter 2 --- Materials and Methods --- p.30 / Chapter 2.1 --- Study Design --- p.30 / Chapter 2.1.1 --- Part 1: Validation of Tail-Suspension Model --- p.32 / Chapter 2.1.2 --- Part 2: Effect of LMHFV on Functional Recovery after Tail Suspension --- p.32 / Chapter 2.1.3 --- Part 3: Effect of LMHFV on Muscle Recovery in Cellular and Histological Aspects --- p.33 / Chapter 2.2 --- Tail Suspension- Hind Limbs Unloading Model and Reloading --- p.33 / Chapter 2.3 --- Low-Magnitude High-Frequency Vibration (LMHFV) Treatment --- p.36 / Chapter 2.4 --- Part 1 and Part 2 Studies --- p.39 / Chapter 2.4.1 --- Isolation of Soleus Muscle for Functional Assessment --- p.39 / Chapter 2.4.2 --- In vitro Muscle Functional Test --- p.42 / Chapter 2.5 --- Part 3 Study --- p.50 / Chapter 2.5.1 --- Implantation of Bromodeoxyuridine (BrdU) Pellet for Satellite Cell Labeling --- p.50 / Chapter 2.5.2 --- Preparation of Soleus Muscle (Sol) for Histological and Cellular Studies --- p.51 / Chapter 2.5.3 --- Preparation of Muscle Cryosections --- p.51 / Chapter 2.5.4 --- Muscle Fiber Typing - ATPase Staining Assay --- p.54 / Chapter 2.5.5 --- Activated Satellite Cell Profiling - Immunofluorescence Imaging --- p.55 / Chapter 2.6 --- Statistical Analysis --- p.57 / Chapter Chapter 3 --- Results --- p.58 / Chapter 3.1 --- Part 1: Validation of Tail Suspension Model --- p.58 / Chapter 3.1.1 --- Morphological Assessment --- p.58 / Chapter 3.1.2 --- Functional Assessment --- p.58 / Chapter 3.2 --- Part 2: Effects of LMHFV on Functional Recovery from Tail Suspension --- p.61 / Chapter 3.2.1 --- Morphological Assessment --- p.61 / Chapter 3.2.2 --- Functional Assessment --- p.63 / Chapter 3.3 --- Part 3: Effects of LMHFV on Muscle Recovery in Cellular and Histological Aspects --- p.72 / Chapter 3.3.1 --- Muscle Fiber Typing - ATPase Staining --- p.72 / Chapter 3.3.2 --- Satellite Cells Proliferation --- p.78 / Chapter 3.4 --- Correlation of outcomes from part II and part III studies --- p.83 / Chapter Chapter 4 --- Discussion --- p.90 / Chapter 4.1 --- Beneficial Effects of LMHFV in Disuse-induced Atrophied Soleus Muscle Recovery --- p.92 / Chapter 4.2 --- Facilitated Recovery of Force Generating Capacity by LMHFV Treatment --- p.93 / Chapter 4.3 --- Biphasic Effects of LMHFV in Muscle Contraction and Relaxation Time --- p.95 / Chapter 4.4 --- Specific Hypertrophy on Type IIB Muscle Fiber Stimulated by LMHFV --- p.96 / Chapter 4.5 --- Physiological Fiber Type Adaptation Maintained in LMHFV Treatment --- p.98 / Chapter 4.6 --- Promoted SC Activation by LMHFV and its Possible Roles in Histological Improvement --- p.99 / Chapter 4.6.1 --- Possible Regulatory Mechanisms of LMHFV in Promoting SC Activation --- p.100 / Chapter 4.7 --- Disuse-induced Muscle Atrophy Successfully Developed by Tail Suspension Model --- p.102 / Chapter 4.8 --- Limitations --- p.103 / Chapter 4.8.1 --- In vitro measurement of isolated muscle contractile functions --- p.103 / Chapter 4.8.2 --- Overestimation of satellite cell (SC) counts --- p.104 / Chapter 4.9 --- Future studies --- p.105 / Chapter 4.9.1 --- Effects of LMHFV on Fast muscle --- p.106 / Chapter 4.9.2 --- Parameters of LMHFV treatment --- p.107 / Chapter 4.9.3 --- Clinical Trials --- p.107 / Chapter Chapter 5 --- Conclusions --- p.110 / Bibliography --- p.113

Indiana University-Purdue University Indianapolis (IUPUI) / Coronary artery disease (CAD) is a leading cause of death among Americans and is fueled by underlying metabolic syndrome (MetS). The prevalence and lethality of CAD necessitates rigorous investigations into its underlying mechanisms and to facilitate the development of effective treatment options. Coronary smooth muscle (CSM) phenotypic modulation from quiescent to synthetic, proliferative, and osteogenic phenotypes is a key area of investigation, with underlying mechanisms that remain poorly understood. Using a well-established pre-clinical model of CAD and MetS, the Ossabaw miniature swine, we established for the first time the time course of Ca2+ dysregulation during MetS-induced CAD progression. In particular, we used the fluorescent Ca2+ dye, fura-2, to examine alterations in CSM intracellular Ca2+ regulation during CAD progression, as perturbations in intracellular Ca2+ regulation are implicated in several cellular processes associated with CAD pathology, including CSM contractile responses and proliferative pathways. These studies revealed that the function of several CSM Ca2+ handling proteins is elevated in early CAD, followed by loss of function in severe atherosclerotic plaques. Decreased intracellular Ca2+ regulation occurred concurrently with reductions in CSM proliferation, measured with Ki-67 staining. In particular, alterations in sarcoplasmic reticulum (SR) Ca2+ store together with altered function of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) were associated with induction of proliferation. Organ culture of coronary arterial segments revealed that culture-induced medial thickening was prevented by SERCA inhibition with cyclopiazonic acid (CPA). Activation of SERCA with the small molecule activator, CDN1163, increased CSM proliferation, which was attenuated by treatment with CPA, thus establishing upregulated SERCA function as a proximal inducer of CSM proliferation. Further, we demonstrated that in vitro treatment of CSM from lean Ossabaw swine with the glucagon-like peptide-1 (GLP-1) receptor agonist, exenatide, increased SERCA function. However, in vivo treatment of Ossabaw swine with MetS with the GLP-1 receptor agonist, AC3174, had no effect on CAD progression and in vitro examination revealed resistance of SERCA to GLP-1 receptor agonism in MetS. These findings further implicate SERCA in CAD progression. Collectively, these are the first data directly linking SERCA dysfunction to CSM proliferation and CAD progression, providing a key mechanistic step in CAD progression.

Indiana University-Purdue University Indianapolis (IUPUI) / Several common diseases such as atherosclerosis, post-angioplasty restenosis, and graft vasculopathies, are associated with the changes in the structure and function of smooth muscle cells. During the pathogenesis of these diseases, smooth muscle cells have a marked alteration in the expression of many smooth muscle-specific genes and smooth muscle cells undergo a phenotypic switch from the contractile/differentiated status to the proliferative/dedifferentiated one. Serum response factor (SRF) is the major transcription factor that plays an essential role in coordinating a variety of transcriptional events during this phenotypic change. The first goal of my thesis studies is to determine how SRF regulates the expression of smooth muscle myosin light chain kinase (smMLCK) to mediate changes in contractility. Using a combination of transgenic reporter mouse and knockout mouse models I demonstrated that a CArG element in intron 15 of the mylk1 gene is necessary for maximal transcription of smMLCK. SRF binding to this CArG element modulates the expression of smMLCK to control smooth muscle contractility. A second goal of my thesis work is to determine how SRF coordinates the activity of chromatin remodeling enzymes to control expression of microRNAs that regulate the phenotypes of smooth muscle cells. Using both mouse knockout models and in vitro studies in cultured smooth muscle cells I showed how SRF acts together with Brg1-containing chromatin remodeling complexes to regulate expression of microRNAs-143, 145, 133a and 133b. Moreover, I found that SRF transcription cofactor myocardin acts together with SRF to regulate expression of microRNAs-143 and 145 but not microRNAs-133a and 133b. SRF can, thus, further modulate gene expression through post-transcriptional mechanisms via changes in microRNA levels. Overall my research demonstrates that through direct interaction with a CArG box in the mylk1 gene, SRF is important for regulating expression of smMLCK to control smooth muscle contractility. Additionally, SRF is able to harness epigenetic mechanisms to modulate expression of smooth muscle contractile protein genes directly and indirectly via changes in microRNA expression. Together these mechanisms permit SRF to coordinate the complex phenotypic changes that occur in smooth muscle cells.

Abstract not available