Why Touch Can Change the Body──Cells Sense Force

Introduction

This series has followed four faces of fascia. It is alive. It senses. It springs back. And it changes.

But one question remains unanswered about that last face: why does it change?

Touching with the hands, moving the body — pressed to the point, these are nothing more than physical events in which force is applied. Pushing, pulling, lengthening, shearing.

How can such a mechanical event alter the structure of living tissue, the behavior of cells, even the working of genes? Where, and by what route, does force become information that a cell can read?

What answers this question is a mechanism called mechanotransduction. It is a core concept in cell biology, and — from where I stand as someone offering hands-on sessions — it is also the firmest footing available for re-describing what happens beneath the palms in the language of molecules.

This post takes up the mechanism by which force reaches the interior of the cell, arrives at the nucleus, and eventually remakes structure. It also sets out how wide the gap remains between these molecular findings and actual hands-on work.

Force Converted into a Chemical Signal

Mechanotransduction is the process by which physical (mechanical) force or deformation is converted into chemical (biochemical) signals. For a cell, force is not merely something that pushes against it. It is also information to be read.

Cells can read having been pushed, having been pulled, and whether their surroundings are stiff or soft. According to that reading, they change shape, switch gene expression on and off, and at times alter even their own fate — what kind of cell they will become. This process is usually understood in three stages:

  • sensing force (mechanosensing)
  • transmitting the force (mechanotransmission)
  • responding (mechanoresponse)

First, then, where in the cell is force received?

Why Adhesion Is Necessary — Cells Forming a Society

Let me start with a more basic question: why do cells gather to form a multicellular body at all?

The reason is division of labor.

A single cell no longer has to take in nutrients, move, and defend itself all on its own. Cells that specialize in contracting, cells that specialize in conveying signals, cells that specialize in absorbing nutrients. Divide the roles, and each can carry its work deeper and further. Our bodies are a society formed by cells that came about this way.

The most visible form of that division of labor is the organ. The stomach and intestines, which receive what is eaten and set about digestion. The liver, which metabolizes nutrients and breaks down toxins. The kidneys, which filter blood and hold the volume of water and the concentration of salt constant. Each takes on specialized work and leaves other work to others. The liver does not eat for itself. The gut does not make its own blood. Only by depending on one another does the whole keep turning.

But division of labor comes at a cost.

To specialize is to leave the rest to others. So none of them can leave its post. If the liver drifted about the abdomen, if the kidneys wandered, if the stomach lost its position connecting to the intestine — the division of labor would immediately fail. The same holds at the level of cells. A muscle cell cannot feed itself. The moment its positional relationship breaks down — near the blood vessels that carry nutrients, near the nerves that give it instructions — that cell can no longer do its work.

For a society to hold, in other words, each member must stay in its appointed place. And that means something is needed to hold them there.

Organs are not, in fact, simply thrown in. They are wrapped in membranes, suspended, and held in position relative to their neighbors. The heart has the pericardium, the lungs the pleura; the abdominal organs are supported by the peritoneum and mesentery while still being able to glide and move. All of these belong to the same family of connective tissue as fascia.

There is one more important point here. For a society to hold, connecting is not enough. Separating is needed just as much.

The contents of the stomach must not leak into the abdomen. Blood must not seep out everywhere. Liver cells and pancreatic cells must not mix together. Division of labor means each keeping to its own domain, and keeping a domain requires a boundary. Without something to divide them, specialization cannot hold, and everything dissolves together into one murky soup.

And what creates that boundary is, again, connective tissue. Epithelial cells line up on a thin matrix membrane called the basement membrane, and by adhering to it they form the wall dividing inside from outside. The membranes wrapping the organs mentioned above, and the membranes wrapping muscle, likewise separate this side from that.

This tissue, then, connects and separates at the same time. It is continuous and yet partitioned. Continuity and division are not a contradiction: because they are separated, each can concentrate on its own work, and because they are connected, the whole can move as one.

At the level of the cell, the situation is no different. What fills the space around cells is a network of collagen and elastin fibers and a watery gel containing hyaluronan. Cell biology calls this the extracellular matrix (ECM).

And here is the crucial point: fascia is that extracellular matrix.

Look through a microscope and a mesh of collagen appears around a single cell. Lower the magnification and the same mesh wraps clusters of cells, wraps muscle, wraps organs, continues into tendon, and eventually becomes a membrane visible to the naked eye — that is fascia. The cell biologist calls it the extracellular matrix; the anatomist calls it fascia. The names differ because the magnification differs, not because they refer to different material.

Fascia is not packing. It is what holds those who divide the labor — from cells to organs — each at its post, and separates each domain from the next. It was the very condition on which the society depends.

When the Information Stops, the Cell Dies — the Integrin as Anchor

What does it mean to belong to a society?

A cell that leaves its post usually cannot go on living. Detached from the matrix, a cell kills itself. This is anoikis (from the Greek for “homelessness”), a cell death brought about by loss of adhesion.

When I first learned this, I was startled. The cell does not die from lack of nutrients. It does not die from being physically destroyed. It dies simply because the connection has been cut. Put another way, a cell continues to receive, through adhesion, the information that it may be here — and when that information stops, it stops living.

This changes how one sees what a cell is. A cell is not a small, self-sufficient living thing. It is a being that stays alive only barely, by continuously receiving information from outside. And that very exchange of information is what makes the society hold.

(There is, admittedly, a loophole in this rule. If a cell breaks the boundary, leaves its post, survives nonetheless, and goes on proliferating — that is the collapse of the society’s order, and it is precisely the behavior known as cancer invasion.)

If that is so, then a cell must be constantly checking whether it is properly connected.

What performs that check is the integrin. It is a protein that spans the cell membrane, physically linking the matrix outside to the cytoskeleton (actin filaments) inside.

Reaching outward to grip collagen and connecting inward to the cell’s framework, it links cell and outside world in a form through which force passes — like a bolt fastening a wall to a post. Integrins do not act singly; many gather to form a structure called a focal adhesion. This becomes the assembly of fasteners where outside and inside are mechanically joined.

And here something follows necessarily. A device that judges whether a cell is connected cannot help but also be a device that reads what the outside world is like. The path along which information about survival travels is also the path that conveys the properties of the outside.

Cells do not, in fact, wait passively. They generate contractile force of their own, pull on the matrix, and measure the resistance that comes back. A stiff matrix resists strongly; a soft matrix does not. That difference becomes a difference in how focal adhesions assemble, and a difference in signal strength. A cell learns the stiffness of its surroundings by pulling on them.

The capacity to read force, in other words, arose as a byproduct of the condition of belonging to a society. Without connection there is no life. And given connection, external force must pass through that junction. So the passage itself becomes a sensor.

One thing comes into view here. Adhesion was, from the start, a channel for information. The news that one may live, and the news of how stiff the surroundings are, travel the same road. If so — the force a hand applies to tissue may also be information reaching the cell along that same road.

The Same Thing Happens at a Different Scale

Let me step back for a moment.

Just as the society of cells depends on the network of the matrix, and just as organs are wrapped, suspended, and held in position by membranes, the largest society — the body — is likewise held together by the continuous network of fascia. Wrapping muscle, continuing into tendon, periosteum, and bone, binding parts into a whole. That was fascia. And these were different names for the same thing.

The same logic operates in each. A device that binds together and separates necessarily becomes a device that transmits force. A device that transmits force can necessarily become a device that reads force. What integrins and the matrix accomplish around a cell, the continuum of fascia accomplishes at the scale of the whole body.

And this is not a metaphor. It is literally continuous. The force a hand applies to fascia reaches, by way of that matrix, the integrins of the cells living there. The network that binds the body hands force over to the fasteners that bind the cell. Only the scale differs; the principle of what happens is unchanged.

Body as an Operating System — the view of the body not as an assemblage of parts but as one system that moves as a whole runs all the way down to the molecular level.

Force Reaches the Nucleus — the View from Tensegrity

That force travels through adhesion into the interior of the cell was shown decisively in one experiment.

Wang, Butler, and Ingber used a device that twists microscopic beads magnetically to apply force directly to receptors on the cell surface. Only when force was applied to integrin β1, the matrix receptor, did focal adhesions form and the cytoskeleton respond by stiffening in proportion to the force.

With receptors not involved in adhesion, this did not occur. The response also required both microtubules and intermediate filaments. Integrins were working not merely as adhesion devices but as receptors for force (mechanoreceptors), conveying that signal to the cytoskeleton.

Maniotis and colleagues went further, showing that mechanical linkage extends from the integrins through the cytoskeleton into the interior of the nucleus. Pull on the cell surface and the shape of the nucleus changes. Force does not stop at the membrane. It reaches deep into the cell, and as far as the place where the genes are held.

Ingber proposed cellular tensegrity — integration through tension — as a framework for explaining this behavior. A cell is a structure integrated by tension, in which elements that bear compression (microtubules) and elements that carry tension (actin filaments) are held in balance. This is why force applied at one point travels through the whole and reorganizes the entire structure.

One caveat is worth stating. This cellular tensegrity is a finding confirmed in the small world of the cell. The discussion of biotensegrity, which extends the same term to the whole body, is a separate matter, established to a different degree. Not treating the two as casually continuous matters a great deal in this field.

Molecules That Carry Force to the Genes — YAP/TAZ and Piezo

How, then, does force that has reached the interior of a cell change the working of genes? In recent years a number of molecules have been found to mediate this.

One is the transcriptional coactivators known as YAP/TAZ. When a cell sits on a stiff matrix, focal adhesions and stress fibers assemble firmly, and YAP/TAZ move into the nucleus. There they alter gene expression and set the direction of the cell’s proliferation and differentiation. Cells read how stiff their surroundings are and determine their own behavior and fate accordingly. Stiffness is a physical property of the environment and, at the same time, information for the cell.

Another is Piezo, an ion channel that opens under force. When the membrane comes under tension, the channel physically opens, ions flow in, and intracellular signaling begins. Piezo2 is the principal channel for proprioception, and Piezo1 responds to stretch and shear stress and has been shown to be involved in fibrosis. This discovery was recognized by the 2021 Nobel Prize in Physiology or Medicine (Ardem Patapoutian).

Here two faces from this series draw close together. Sensory receptors distributed through fascia register having been touched — the sensing face. And cells read force and remake structure — the changing face. Do the two join somewhere into one?

And It Releases Within Minutes — Langevin’s Fibroblasts

Up to here has been general cell biology. From here it becomes a matter of fascia.

Something often happens during a hands-on session. A hand is placed and held, and within a few minutes the tissue releases. This phenomenon has long been considered difficult to explain, since it is hard to imagine collagen fibers physically lengthening in such a short time under that degree of force. Robert Schleip has likewise pointed out that mechanical deformation alone cannot account for a release within minutes.

The research of Helene Langevin and colleagues offers one answer.

Fibroblasts in loose connective tissue, when the tissue is stretched, reorganize their cytoskeleton within minutes, spread out substantially, and extend new lamellipodia. This was observed both in excised tissue (ex vivo) and in living animals (in vivo). The cells sensed having been stretched and actively changed shape.

What follows is more important still. This cytoskeletal reorganization was shown to contribute actively to reducing the tension of the tissue itself. The viscoelasticity of connective tissue had until then been attributed largely to the properties of the matrix as material. But that was not the whole story. The tension of the tissue was also determined by the living behavior of the cells residing in it. When tissue is stretched, fibroblasts spread, and that spreading leads the tissue toward a state of lower tension.

Stretch changes even the shape of the nucleus. Force reaches the innermost part of the cell.

So when tissue releases beneath the hands, collagen may not be being physically lengthened. Cells may be reading the applied force and responding. The release is not a deformation of material but a living response.

And here the earlier question finds its answer. Sensing and changing were not separate events. A hand touches. Receptors register it, and that same force reaches the cells and is read. The sensing tissue and the changing tissue are one and the same tissue, answering to one and the same force.

Touching and Moving — the Circuit in Principle

A line can now be drawn through the question this series has taken for granted.

What a hand applies is force. That force reaches the cell by way of the matrix, is received at integrins and focal adhesions, and travels along the cytoskeleton to the nucleus. The cell reads it, changes shape within minutes, and then, over time — over several months to two years — remakes the alignment of fibers and the molecules it produces.

Why being touched and moving can change tissue: the circuit, in principle, is indeed here. That Rolfing values not only hands-on work but the re-education of movement makes sense on this map. Both are force reaching cells.

But — and this is the crucial part — what is possible in principle and what has been confirmed clinically are entirely different things.

Being Honest About the Limits

Let me draw the line clearly.

First, mechanotransduction itself is established cell biology. But how much force applied by hands-on work reaches which cells within a living body, and what it brings about there, has barely been quantified. A wide gap remains between force being able to reach cells and a practitioner’s hands producing an intended change in those cells.

Second, the core of Langevin’s findings concerns loose connective tissue in rodents, and much of it consists of observations in excised tissue (ex vivo). The same thing does not necessarily occur in the same way in deep human fascia.

Third, much of the work on YAP/TAZ and Piezo comes from cultured cells and disease models. It has not been tested directly in the context of manual therapy or exercise. Borrowing molecular findings as an explanation of the efficacy of hands-on work calls for caution.

Fourth, cellular tensegrity (at the scale of the cell) and biotensegrity (at the scale of the whole body) are established to different degrees. Arguing for the latter on the grounds of the former is a leap. The same applies to the resemblance across scales described in this post — that a mechanism for binding becomes a mechanism for reading force. That points out a logic common to two levels; it does not mean that what has been confirmed in cells holds as such for the whole body. Resembling and being identical are not the same.

In short, what is sketched here is a circuit of possibility for why change can occur, not a proof that “therefore Rolfing works.” That a circuit exists and that the circuit can be operated intentionally are not the same thing.

Conclusion

Even so, these findings change how the tissue beneath the palms is seen.

What is there is not passive material that dents when pressed and returns when released. It is tissue that receives force, reads it, responds, and remakes its own structure. And the cell stays alive only barely, by continuously receiving information from outside. What hands-on work applies might be thought of less as deformation itself than as information traveling that channel.

The structure is nested. There is fascia binding the body, membranes wrapping the organs, and the matrix and integrins binding the cell. The mechanism for binding is, as it stands, the mechanism for transmitting force and for reading it — the same logic repeated across changes of scale.

Cells sense force. That fascia changes amounts, in the end, to this.

References

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  • Wang N, Butler JP, Ingber DE. Mechanotransduction across the cell surface and through the cytoskeleton. Science. 1993;260(5111):1124–1127. doi:10.1126/science.7684161
  • Maniotis AJ, Chen CS, Ingber DE. Demonstration of mechanical connections between integrins, cytoskeletal filaments, and nucleoplasm that stabilize nuclear structure. Proc Natl Acad Sci USA. 1997;94(3):849–854. doi:10.1073/pnas.94.3.849
  • Ingber DE. Tensegrity: the architectural basis of cellular mechanotransduction. Annu Rev Physiol. 1997;59:575–599. doi:10.1146/annurev.physiol.59.1.575
  • Dupont S, Morsut L, Aragona M, et al. Role of YAP/TAZ in mechanotransduction. Nature. 2011;474(7350):179–183. doi:10.1038/nature10137
  • Langevin HM, Bouffard NA, Badger GJ, Iatridis JC, Howe AK. Dynamic fibroblast cytoskeletal response to subcutaneous tissue stretch ex vivo and in vivo. Am J Physiol Cell Physiol. 2005;288(3):C747–C756. doi:10.1152/ajpcell.00420.2004
  • Langevin HM, Storch KN, Snapp RR, et al. Tissue stretch induces nuclear remodeling in connective tissue fibroblasts. Histochem Cell Biol. 2010;133(4):405–415. doi:10.1007/s00418-010-0680-3
  • Langevin HM, Bouffard NA, Fox JR, et al. Fibroblast cytoskeletal remodeling contributes to connective tissue tension. J Cell Physiol. 2011;226(5):1166–1175. doi:10.1002/jcp.22442
  • European Rolfing Association: Fascia Expertise & Scientific Research
  • Fascia Research Society

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Hidefumi Otsuka, Ph.D. | Certified Advanced Rolfer™ / Rolf Movement Practitioner

Completed his doctorate at the University of Tokyo Graduate School of Medicine. After working in medical marketing at an international pharmaceutical company, he has offered Rolfing® sessions in Shibuya since 2015. His work centers on the integration of science and practice.

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Hidefumi Otsuka

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