Passive muscle stiffness may be influenced by active contractility of intramuscular connective tissue

[문형철]

선자세로 있을때 인체의 근육은 어떻게 resting length를 유지하며 passive muscle stiffness를 유지하는가?

바로 connective tissue덕분이다.

어제 김송준 소장님이 알려줘 바로 찾았다. ㅎㅎㅎ 

참고) tonic muscle은 soleus와 같은 자세유지근을 말함. 

tonic muscle = slow twitch, type 1 muscle, 산소를 에너지로 이용, 

phasic muscle = fast twitch, type 2 muscle

The article introduces the hypothesis that intramuscular connective tissue, in particular the fascial layer known as the perimysium, may be capable of active contraction and consequently influence passive muscle stiffness, especially in tonic muscles. Passive muscle stiffness is also referred to as passive elasticity, passive muscular compliance, passive extensibility, resting tension, or passive muscle tone. 

이 논문의 가설

- perimysium(fascial layer) 근육내 결합조직은 active contraction을 할 수 있을 수 있고, passive muscle stiffness에 영향을 줄 수 있을 수 있음. 특히 tonic muscle에서

- passive muscle stiffness는 passive elasticity, passive muscular compliance, passive extensibility, resting tension, passive muscle tone와 연관되어 있음.

Evidence for the hypothesis will be given from five considerations:

1. Tonic muscles contain more perimysium than phasic muscles.

2. The perimysium is designed to serve a load bearing function.

3. The perimysium may be characterized by a high density of myofibroblasts.

4. Myofibroblasts enable fascia to actively contract.

5. The perimysium exhibits a high stiffness adaptability response to mechanical stimulation.

- tonic muscle는 phasic muscle보다 perimysium을 많이 포함하고 있음

- perimysium은 load bearing 기능을 돕기 위해 설계됨

- perimysium은 높은 농도의 myofibroblast로 특징지워짐

- myofibroblast는 fascia가 능동적으로 수축할 수 있게 함

- perimysium은 기계적 자극에 반응하여 높은 stiffness adaptability를 가짐. 

결론적으로 perimysium은 myofibroblast가 촉진한 능동적 수축과 함께하는 기계적자극에 반응하여, 특히 tonic muscle에서 증가된 긴장요구에 수동적 muscle stiffness에 적응함

perimysium is designed to serve a load-bearing function 

The morphology and arrangement of collagen fibers in the perimysium is different from the epi- or endomysium in several ways. It consists mainly of collagen fibers with a fairly large diameter [6]. In the perimysium these fibers exhibit a pronounced crimp formation, and they are arranged in a lattice-like criss-cross orientation with parallel fibers going in two different directions. Muscle contraction or stretch changes the angles of this lattice with respect to the muscle fiber direction, ranging from 80
at short sarcomere length to approximately 20
at high extension. 

- perimysium에서 collagen fiber의 형태과 배열은 endomysium 또는 epimysium이 서로 다름. perimysium은 large diameter의 콜라겐 섬유로 구성됨. perimysium에서 콜라겐 섬유는 곱슬한 형태(crimp formation)을 보여주고, 두방향과 함께 주행하는 parallel fiber과 함께 lattice-like criss-cross orientation(격자모양의 십자로 교차하는 방향)으로 배열됨. 

- 근육 수축 또는 스트레치는  muscle fiber 방향과 함께 이 격자모양의 각도를 변화시키는데, 그 범위는  80
at short sarcomere length to approximately 20
at high extension??

Passive muscle stiffness may be influenced by active contra.pdf

Summary 

The article introduces the hypothesis that intramuscular connective tissue, in particular the fascial layer known as the perimysium, may be capable of active contraction and consequently influence passive muscle stiffness, especially in tonic muscles. Passive muscle stiffness is also referred to as passive elasticity, passive muscular compliance, passive extensibility, resting tension, or passive muscle tone. 

Evidence for the hypothesis is based on five indications: 

(1) tonic muscles contain more perimysium and are therefore stiffer than phasic muscles;

(2) the specific collagen arrangement of the perimysium is designed to fit a load-bearing function; 

(3) morphological considerations as well as histological observations in our laboratory suggest that the perimysium is characterized by a high density of myofibroblasts, a class of fibroblasts with smooth muscle-like contractile kinetics; 

(4) in vitro contraction tests with fascia have demonstrated that fascia, due to the presence of myofibroblasts, is able to

actively contract, and that the resulting contraction forces may be strong enough to influence musculoskeletal dynamics; (5) the pronounced increase of the perimysium in muscle immobilization and in the surgical treatment of distraction osteogenesis indicates that perimysial stiffness adapts to mechanical stimulation and hence influences passive muscle stiffness. 

- tonic muscle은 perimysium을 좀더 많이 가지고 있어서 phasic muscle보다 좀더 단단함

- perimysium의 특별한 collagen arrangement는 load-bearing function에 적합하도록 설계되어 있음.

- 조직학적 관찰뿐 아니라 형태학적 관점으로 볼때, perimysium은 high density of myofibroblast가 특징이고, smooth muslce과 같은 수축구조물같은 fibroblast의 분류가 특징임.

- in vitro 실험에서 fascia와 함께 수축 테스트는 설명함. fascia는 myofibroblast의 존재때문에 actively 수축할 수 있음. 그리고 이어지는 수축력은 강해서 근골격계 동적 움직임에 충분한 영향을 줄만큼 강함

In conclusion, the perimysium seems capable of response to mechanostimulation with a myofibroblast facilitated active tissue contraction, thereby adapting passive muscle stiffness to increased tensional demands, especially in tonic musculature. If verified, this new concept may lead to novel pharmaceutical or mechanical approaches to complement existing treatments of pathologies which are accompanied by an increase or decrease of passive muscle stiffness (e.g., muscle fibroses such as torticollis, peri-partum pelvic pain due to pelvic instability, and many others). Methods for testing this new concept are suggested, including histological examinations and specific in vitro contraction tests.

- 결론적으로 perimysium은 myofibroblast가 촉진한 능동적 수축과 함께하는 기계적자극에 반응하여, 특히 tonic muscle에서 증가된 긴장요구에 수동적 muscle stiffness에 적응함. 

- 만약 이 이론이 확실하다면, 이 새로운 개념은 passive muscle stiffness의 증가 또는 감소에 의해 수반되는 pathology의 보완적 치료에 새로운 약물치료 또는 mechanical 접근방법을 제공함.  예를들어 muscle fibrosis such as torticollis, peri-partum pelvic pain due to pelvic instability

Introduction

When skeletal muscles are passively stretched they exhibit measurable resistance even when their motor neurons are quiescent and their myofibers are not actively contracting. This behaviour is called passive muscle stiffness and

is also referred to as passive elasticity, passive muscular compliance, passive extensibility, resting tension, or passive muscle tone.

- 근골격계 근육이 수동적으로 스트레치될때, 근육은 측정가능한 저항성을 보여줌. motor neuron이 quiescent할때에도, 그리고 myofiber는 능동적으로 수축하지 않음. 

- 이러한 현상을 passive muscle stiffness라고 부르고, 이는 passive elasticity, passive muscular compliance, passive extensibility, resting tension, passive muscle tone로 언급됨. 

Since the discovery of the titin filaments and their highly elastic properties, it has been commonly assumed that passive muscle stiffness depends primarily on these tertiary intramuscular filaments [1]. Yet recent research suggests that passive muscle stiffness is also influenced by muscular connective tissues [2]. This new perspective is supported by conclusions drawn from work involving tenotomy, fasciotomy and aponeurotomy [3] as well as studies on the passive extensibility of skeletal muscle [4].

- 티틴이 높은 탄성특성이 있음을 발견한 후로 passive muscle stiffness는 티틴의 3번째 intramuscular filament에 의존한다고 여겨져 왔음. 하지만 최근의 연구에 의하면 passive muscle stiffness는 muscular connective tissue에 의해 영향을 받는다고 제안됨. 이러한 새로운 전망은 tenotomy, fasciotomy and aponeurotomy와 skeletal muscle의 passive extensibility 관련된 연구에 의한 결론으로 지지되고 있음. 

Based on this previous research, the authors propose the hypothesis that intramuscular connective tissues, and in particular the fascial layer called the perimysium, may be able to actively contract and thereby adapt myofascial tissue stiffness to increased tensional demands, especially in tonic muscles. 

- 이러한 연구에 기초하여 저자의 가정은 다음과 같음. intramuscular connective tissue와 특히 perimysium이라고 불리는 fascial layer가 능동적으로 수축할 수 있다고 함. 그래서 특히 tonic muscle에서 증가된 tensional demands에 myofascial tissue stiffenss에 적응함. 

Evidence for the hypothesis will be given from five considerations:

1. Tonic muscles contain more perimysium than phasic muscles.

2. The perimysium is designed to serve a load bearing function.

3. The perimysium may be characterized by a high density of myofibroblasts.

4. Myofibroblasts enable fascia to actively contract.

5. The perimysium exhibits a high stiffness adaptability response to mechanical stimulation.

- tonic muscle는 phasic muscle보다 perimysium을 많이 포함하고 있음

- perimysium은 lad bearing 기능을 돕기 위해 설계됨

- perimysium은 높은 농도의 myofibroblast로 특징지워짐

- myofibroblast는 fascia가 능동적으로 수축할 수 있게 함

- perimysium은 기계적 자극에 반응하여 높은 stiffness adaptability를 가짐. 

Implications for pathologies with increased or decreased passive muscle stiffness will be elucidated, and concrete steps towards testing the hypothesis will be suggested.

- increased or decreased passive muscle stiffness 병리는 명백해질 수 있고, 이 가설은 좀더 지지됨. 

Evidence

Tonic muscles contain more perimysium than phasic muscles Intramuscular connective tissue is generally divided

into three hierarchical and interconnected layers: the endomysium, surrounding individual myofibers; the perimysium, separating and enveloping myofiber bundles; the epimysium, the fascial wrapping for the whole muscle. It is of interest that tonic muscles like the soleus, which are more involved in posture, tend to contain significantly more perimysium than phasic muscles [5,6]. 

- tonic muscle은 phasic muscle보다 많은 perimysium을 포함하고 있다는 것은 세가지로 분류..

1) endomysium, surrounding individual myofibers

2) perimysium, separating and enveloping myofiber bundles

3)  epimysium, the fascial wrapping for the whole muscle

- soleus와 같은 tonic muscle은 posture 에 관여하고, phasic muscle보다 좀더 많은 perimysium을 포함하는 경향이 있음. 

This may be related to the increased oxygen demand and vascularization of tonic muscles, since the perimysium in muscular fasciae contains the highest proliferation of blood vessels and the increased thickness of the perimysium may provide a useful cushioning effect during muscular contraction. On the other hand, the increase in perimysial thickness

has also been shown to correlate with a higher passive stiffness [7]. In food science perimysial thickness correlates with raw meat toughness [8,9].

- 이것은 tonic muscle의 vascularization과 증가된 산소요구와 연관되어 있음. muscular fasciae내에 perimysium이 blood vessel의 높은 proliferation을 포함하고, perimysium의 thickness증가때문에 근육수축동안 유용한 cushioning effect를 제공할 수 있음. 

- 다른 한편으로 perimysial thickness 증가는 높은 passive muscle stiffness와 연관성을 보여줌. 

- In food science perimysial thickness correlates with raw meat toughness [8,9]. ????

The perimysium is designed to serve a load-bearing function 

The morphology and arrangement of collagen fibers in the perimysium is different from the epi- or endomysium in several ways. It consists mainly of collagen fibers with a fairly large diameter [6]. In the perimysium these fibers exhibit a pronounced crimp formation, and they are arranged in a lattice-like criss-cross orientation with parallel fibers going in two different directions. Muscle contraction or stretch changes the angles of this lattice with respect to the muscle fiber direction, ranging from 80
at short sarcomere length to approximately 20
at high extension. 

- perimysium에서 collagen fiber의 형태과 배열은 endomysium 또는 epimysium이 서로 다름. perimysium은 large diameter의 콜라겐 섬유로 구성됨. perimysium에서 콜라겐 섬유는 crimp formation을 보여주고, 두방향과 함께 주행하는 parallel fiber과 함게 lattice-like criss-cross orientation(격자모양의 십자로 교차하는 방향)으로 배열됨. 

- 근육 수축 또는 스트레치는  muscle fiber 방향과 함께 이 격자모양의 각도를 변화시키는데, 그 범위는  80
at short sarcomere length to approximately 20
at high extension??

skeletal muscle에서 결합조직의 morphology.pdf

Interestingly, at high extension the collagen crimp formation also straightens out, and it increases again when the muscle tissue is relaxed [10,9]. As outlined in detail by Rowe [9] and Purslow [10], the particular combination of these features

supports the assumption, that the perimysium is designed to increase passive muscle stiffness and to serve a load-bearing function by preventing overstretching of the muscle fiber bundles.

- 흥미롭게도, collagen crimp formation을 크게 신전시킴은 바르게 정열하고, muscle tissue가 이완될때 다시 증가함. 

- Rowe 와 Purslow의 연구에 의하면 perimysium은 passive muscle stiffness 증가를 위해 설계되고, muscle fiber bundle의 과스트레칭 방지에 의해 load bearing 기능을 제공하기 위해 설계됨. 

The perimysium may be characterized by a high density of myofibroblasts 

The most common type of connective tissue cells are fibroblasts. Fibroblasts as well as having other functions are responsible for the production of collagen fibers and other elements of the extracellular matrix. Several phenotypes of fibroblasts exist. Among these, the myofibroblast group is of special interest in tissue contraction. These cells can be identified by their a-smooth muscle actin stress fibers. Their smooth muscle-like contractile kinetics make myofibroblasts well suited for long lasting isometric contractions, and their contraction plays a major role in wound healing as well as in pathological fascial contractures such as Dupuytren disease, plantar fibromatosis, or frozen shoulder [11].

-  connective tissue cells의 대부분은 fibroblast임. fibroblast는 collagen fiber와 extracellular matrix element 생성을 담당.

- 몇가지 fibroblast의 phenotype이 존재함. 이들 중 myofibroblast 그룹은 tissue contraction역할. 

- 이 세포들은 smooth muscle actin stress fibers에 의해 확인됨. 그들의 smooth muscle-like contractile kinetic은 myofibroblast를 만들어 long lasting 등척성 수축에 잘 어울리게 함. 그들의 수축은 상처회복에 중요한 역할을 할 뿐아니라 Dupuytren disease, plantar fibromatosis, or frozen shoulder와 같은 병리적인 fascial contracture에 중요한 역할을 함. 

Disorders of the Plantar Aponeurosis. 족저근막염 그.pdf

The presence of myofibroblasts in normal (nonpathological) fascia has already been demonstrated [12–14]. Unfortunately, no quantitative histological examination has yet been published examining possible differences in myofibroblast density between the epi-, peri- and endomysial fascial layers. Nevertheless the following observations can be made. The density of myofibroblasts in connective tissues has been reported to be greater in both the more crimped areas as well as in the more vascularized regions [15,16]. The correlation to vascularization may be related to a stimulatory effect of the mast cell product heparin on myofibroblast development [17,18]. 

- 정상 결합조직에서 myofibroblasts 이미 연구되어 있음. 불행하게 정량적 조직학적 검사는 아직  epi-, peri- and endomysial fascial layers에서  myofibroblast 농도에 관한 차이가 연구되어 있지 않음. 

-  density of myofibroblasts in connective tissues는 혈관이 많은 곳뿐 아니라 crimped area에서 많다고 보고됨. myofibroblast development에서 vascularization은 mast cell이 분비하는 해파린의 자극과 연관됨. 

It is of interest that the perimysium is not only the intramuscular layer which exhibits the most crimp formation, but it also contains the most blood vessels [19,20]. It can therefore be postulated, that the density of myofibroblasts is probably higher in the perimysium than in either the endo- or epimysial fascial layers. Preliminary results from histological examinations of rat soleus muscle in our laboratory support this assumption. They show a striking increase in the density of myofibroblasts in the perimysium. No other fascial layer that we have observed to this date (in non-pathological conditions) seems to have such a high density of contractile cells [21]. 

- perimysium이 crimp formation에서 많이 관찰되는 것 뿐만 아니라 blood vessel에서 많이 포함하고 있다는 것은 흥미로운 일.

- 그래서 다음과 같이 가정할 수 있음. density of myofibroblasts는 endo- or epimysial fascial layers보다 perimysium에 많이 존재한다고..

- 쥐 soleus muscle의 조직학적 연구는 이 가설을 지지함. 

Myofibroblasts enable fascia to actively contract

As has originally been suggested in this journal [22], several lines of reasoning and experimental findings support the notion, that fascia is able to actively contract and consequently influence musculoskeletal dynamics. While this new concept was originally only offered as a justified hypothesis, it has now been repeatedly confirmed by several 

laboratories. Masood and Naylor [18,23,24] reported that superficial and deep lumbar fascia from rats as well as from guinea pigs contracted in response to in vitro application of the myofibroblast stimulant mepyramine as well as to the

smooth muscle agonists adenosine and angiotensine II. Contractions started within several minutes and were in a dose dependent, reproducible and reversible manner. 

- fascia는 능동적으로 수축하고 이어서 musculoskeletal dynamics에 영향을 준다는 많은 논문이 있음. 

- 쥐, 돼지의  superficial and deep lumbar fascia는 smooth muscle agonist 아데노신과 안지오텐신뿐 아니라  myofibroblast 자극제 메피라민에 반응하여 수축함. 수축은 몇분내에 일어나고 dose dependent, 반복적이고 가역적으로 일어남. 

The smooth muscle relaxing substances nifedipine and EDTA as well as the microtubule disrupting substance  cytochalasin-D exhibited a relaxing effect . A relaxing response in porcine lumbar fascia to the substance glyceryltrinitrate

(a NO donor and smooth muscle relaxant) has been reported by Schleip et al. [12]. Malata found that mepyramine-induced contractions in rat subcutaneous fascia were enhanced by previous incubation with heparin [25]. Using an immunohistochemical analysis of 39 tissue samples from the thoracolumbar fascia of 11 human donors (ages

19–76 years), Schleip et al. [12] demonstrated the widespread presence of myofibroblasts in all samples, with an average density of 79 cells/mm2 in his longitudinal sections.

- smooth muscle 이완제인  nifedipine and EDTA 뿐 아니라 microtubule disrupting substance  cytochalasin-D는 이완 반응을 보임. 메피라민으로 유도된 쥐의  subcutaneous fascia 수축은 헤파린 투여에 의해 증가됨. 사람의 흉요근막의 연구에서...

Taken together, these findings confirm‎ that fascial tissues can actively contract, and that their contractility appears to be driven by myofibroblasts. The question as to whether or not these active fascial contractions could be strong enough to

exert any significant impact on musculoskeletal dynamics has previously been addressed in this journal [22] the following way: taking the greatest measured force of in vitro fascial contractions and extrapolating that to an average size of the superficial layer of the thoracolumbar fascia in humans, the resulting contraction force can amount to 38 N, which may be a force strong enough to influence biomechanical behaviour, such as in a contribution to paraspinal compartment syndrome or in the prevention of spinal segmental instability [26].

- 이러한 연구들은 다음과 같은 사실을 증명함. 근막은 능동적으로 수축하고, 그들의 수축은 myofibroblast에 의해서 유도됨. 

- 의문은 다음과 같다.  active fascial contractions이 근골격계의 역동적 움직임에 충분한 힘을 가지고 있는가?

- in vitro 실험에서 인체의 흉요근막 superficial layer는 38N을 담당할 수 있고, 척추분절 불안정성을 방지하기에 충분한 biomechanical behaviour를 감당할 만큼 충분함. 

Connective tissue changes in immobilised muscle.pdf

The perimysium exhibits a high stiffness adaptability response to mechanical stimulation

Several examples demonstrate that the perimysium adapts more readily to changes in mechanical tension than other intramuscular connective tissues. Skeletal deformities are sometimes treated by a surgical reconstruction process known

as distraction osteogenesis. Unfortunately, the treatment is frequently accompanied by increased muscle stiffness. It has been shown that this effect correlates with a significant increase in perimysial thickness happening in response to the

increased tissue stretch. A faster lengthening rate (1.4 mm/day in the tibialis anterior of skeletally immature rabbits) leads to more severe tissue stiffness than a slower rate (0.7 mm/day); even though no major cellular pathologic abnormalities

were detected [27].

- perimysium은 다른 intramuscular connective tissues보다 mechanical tension에서 변화보다 쉽게 적응.

- 근골격계의 변형은 때로 distraction osteogenesis로 알려진 surgical reconstruction process로 치료함. 불행히도 이러한 치료는 흔히  increased muscle stiffness를 동반함. 이는 증가된 tissue stretch에 반응하여 perimysial thickness가 의미심장하게 증가함과 연관되는 효과가 나타남. 

Another example is the effect of immobilization.

When a muscle is immobilized in a shortened position it becomes stiffer. This correlates with an increase in intramuscular fascia, which can already be documented within two days of immobilization. While the endomysium remains unaffected during this time, a significant thickening of the perimysium can be seen in the first few days; and it is this change in perimysial thickness (and therefore also in absolute perimysial stiffness) which is considered to be responsible for the rapid muscular stiffening during the first week [28].

- 근육이 짧아진 상태에서 고정될때 좀더 경직되기 쉬움. 이는 이틀간의 고정이내에 발생할 수 있는 현상으로 intramuscular fascia내에서 증가와 연관성을 가짐. 

- 이틀이내의 고정에서 endomysium은 영향을 받지 않기 때문에,  significant thickening of the perimysium은 처음 며칠이내에 나타남. perimysial thickness (absolute perimysial stiffness)는 고정 첫주동안 빠른 muscular stiffening에 담당하는 것으로 고려됨.

 It is of interest that the process of myofibroblast-induced stiffening of fascia seems to have a U-shaped responsiveness to mechanostimulation, since both an absence, as well as an unusually high amount of mechanical tension can lead to increased tissue stiffening. The existence of similar windows of responsiveness to mechanostimulation is nevertheless not unusual among connective tissue cells [29,30].

- 근막의 myofibroblast-induced stiffening 과정이 mechanostimulation에 U-shaped 반응을 가지는 것은 흥미로운 일. 그래서 높은 mechanical tension 뿐 아니라 absence(기계적 긴장이 없음)도 tissue stiffening 증가를 야기함. 

It can be assumed that these perimysial adaptations involve the functioning of fibroblasts, since these cells regulate both collagen density and matrix constitution, as well as having the capacity to contract. Among the different types of fibroblasts, it is most likely the myofibroblast group which is responsible for the rapid increase in tissue thickness

(within two days in the last example above). Although regular turn-over times for collagen by normal fibroblasts would take much longer; myofibroblast- facilitated tissue contractions such as in wound healing or pathological scaring often demonstrate similar rapid changes in tissue density as have been observed here. Due to their complexity and relatively recent discovery, many aspects of myofibroblast are still not yet understood. Similar to the group of smooth muscle cells, it seems that many different phenotypes of myofibroblasts exist, with significant differences in both receptor expression‎ and contractile behaviour [17]. 

In spite of this, it seems clear that in vivo myofibroblastfacilitated tissue contractions, sometimes also called ‘contractures’ (to indicate a more long lasting tissue change), usually involve aspects of smooth muscle-like cellular contraction as well as an increased and altered connective tissue remodeling [11].

Conclusions

Tonic muscles contain more perimysium than phasic muscles. Their increased passive muscle stiffness makes them nutritionally the tougher meat. The specific collagen arrangement of the perimysium supports a load bearing function, i.e., an increase in perimysial stiffness is expected to increase muscular stiffness. It can be assumed that the perimysium is characterized by a high density of myofibroblasts, a group of fibroblasts responsible for rapid tissue contractions. Perimysial fibroblasts respond readily to changes in mechanical stimulation and their response leads to significant

changes in passive muscle stiffness. It is suggested that active contractility of perimysial myofibroblasts – similar to the tissue contractions in wound healing and pathological fascial contractures – enables the perimysium to respond to significant changes in mechanical stimulation with an increase in its stiffness. It is our hypothesis, that intramuscular

connective tissues, particularly the perimysium and especially in tonic muscles, may be able to actively contract and thereby adapt muscle stiffness to altered tensional demands. As a secondary and a slower reacting adaptation system,

this may assist the primary and more rapid adjustments of the neuromuscular system.

Implications

A multitude of pathologies are accompanied and complicated by increased passive muscle stiffness.

Examples range from torticollis and other muscle fibroses, to Parkinson’s rigor, ankylosing spondylitis, neck or back pain associated with chronic muscular tightness, to muscle shortness in rehabilitation. While the primary cause of the pathology is clearly outside the field of this paper, daily motor performance is frequently impeded by secondary changes in passive muscle stiffness, particularly in tonic muscles. Our hypothesis suggests, that  aside from myogenic changes – an increase in the perimysial stiffness may be a results of myofibroblast facilitated contraction of this fascial layer.

If verified, this could open new avenues for novel mechanical or pharmaceutical approaches that would complement existing treatments. In spastic muscular dystrophy, for example, the soleus is often chronically shortened, which makes walking difficult. This is usually treated either surgically or with various mechanical stretching approaches.

We suggest that treatment with super-slow manual deep tissue techniques which are geared towards sensing and influencing cellular contractility, may be helpful in this and similar conditions. Such techniques are commonly practiced by osteopaths and by practitioners of the Rolfing method of deep tissue manipulation [31]. Treatment could be further

assisted nutritionally with substances like L-arginine that tend to increase the presence of nitrous oxide [32] and, therefore, may increase myofibroblast relaxation. Pharmaceutical treatment with relaxin could be explored for its related antifibrotic effect [33]. 

New approaches may also be possible for pathologies with a decreased myofascial stiffness, such as peri-partum pelvic pain due to pelvic instability, fibromyalgia, or back pain due to spinal segmental instability. It is therefore suggested, that this hypothesis be tested via histological examination and via in vitro contraction tests. For the histological examination,

we recommend taking muscular tissue sections which include the endo-, peri- and epimysium, treating these sections with immunohistochemistry for a-smooth muscle actin, and then performing a quantitative analysis. Our prediction is that a much higher quantity of contractile cells will be found in the perimysium than in the epi- or endomysium, especially in the tonic muscles. 

For the in vitro contraction tests the isometric superfusion bath protocol of Pipelzadeh and Naylor [14] is suggested, as this method has the advantage of continually washing the tissue and seems more sensitive for measuring slow tissue responses than the classical organ bath method [34]. Using mepyramine or other myofibroblast stimulants, perimysial

tissues from tonic and phasic muscles could be tested for a contractile response to these agents.]

It would also be of interest to apply this protocol to strips of tonic muscle tissue which include myofibers as well as the connected endo-, peri- and epimysium. Given a contractile response, further discriminative tests could then be performed, for example the application of nifedipine or other smooth muscle relaxants, or treating enzymatically

skinned myocells with the same myofibroblast contraction stimulants for comparison. If it could then be shown, that tonic muscles can be stimulated by myofibroblast agents to contract and relax in a reproducible and reversible manner without active changes in their myofibers, our hypothesis should prove to be a fertile ground for both new therapeutic directions and further research.

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[박건용]

고정자세에도 perimysium의 active contraction으로 근수축이 안 일어남. phasic muscle보다 tonic muscle은 perimysium을 많이 포함하고 있고 perimysium은 높은 농도의 myofibroblast로 지니고 있다. myofibroblast는 fascia가 능동적으로 수축할 수 있게 하여 perimysium의 active contraction을 일으키고, 이는 근골격계의 역동적 움직임에 충분한 힘을 가지고 있다. wound healing, pathological fascial contractures, 사경, 파킨슨병의 강직, 강직성척수염 등에도 myofibroblast facilitated contraction of this fascial layer 영향을 준다. 정골의학이나 롤핑의 deep tissue 테크닉이 perimysial stiffness의 병리적 상태에 도움된다.

[문형철]

myofibroblast에 대한 연구 진행중!!!