Knowledge of mechanobiology is essential for management of breastfeeding and lactation-related problems

The frontier science of mechanobiology offers vital insights into how breastfeeding works

The powerful effects of the physical forces which act upon our body and our baby's body have been largely overlooked in the science of human lactation, but are fundamental to breastfeeding and lactation domain of Neuroprotective Developmental Care (NDC or the Possums programs).

On the macroscopic scale, it's not surprising that the effects of embodied physical forces have been overlooked, since our society's relationship with the bodies of cis-women (and even more for so for the bodies of non-binary or transgendered people, or people with differences in sex development) remains problematic.

Yet the physicality of milk flow involves mechanical forces. The physicality of two human bodies interacting involves the mechanical forces of touch - pressure on the skin, whether light or firm. Baby's mouth suckling on the breast applies mechanical forces of touch and of vacuum - affected by the way your baby fits into your body.

Microscopically, cells are constantly exposed to mechanical pressures. This is even more the case with the oscillating hydrostatic pressures within the lactiferous ducts and alveoli, as milk volumes rise and fall in response to external milk removal.

You can find out about the frontier science of mechanobiology here.

The mechanobiology of lactation is foundational to the NDC Clinical Guidelines for lactation-related problems

The NDC Clinical Guidelines are clinical translations of the innovative NDC mechanobiological models of human lactation, which have been peer reviewed and published in the international research literature. NDC uniquely proposes that understanding mechanobiology is fundamental to holistic clinical assessment and management of the following lactation-related problems

• Maternal nipple pain and damage (starting here)

• Maternal breast inflammation (starting here)

• Maternal musculoskeletal pain associated with breastfeeding (here)

• Other clinical presentations which result from positional instability and mechanical breast tissue drag as baby suckles, such as

  • Fussiness at the breast (starting here)

  • Conditioned dialling up at the breast (here)

• Production mismatch (either higher or lower than infant need).

The role of mechanosensing in breastfeeding and lactation

Mechanical signals are a constant feature of the natural world, resulting in finely tuned coordination among signalling networks and genes. You can find out about this here.

But the critical role of mechanical factors in the signalling networks of lactation is only beginning to be elucidated.1

Cell signalling and function during lactation are affected by mechanical stressors from

1. Cell-intrinsic forces, for example, contractile forces exerted by the actin-myosin skeleton of myoepithelial cells. Contraction of myoepithelial cells of milk glands creates pressure. This pressure causes the alveolar gland to contract and take on a random scrunched up shape. This in turn places pressure or mechanical stress upon any milk that is inside the alveolar lumen, so that the milk flows out into the duct, where any milk present is resting at a lower pressure.

2. Cell-extrinsic forces, for example, lactocyte stretching, loss of apical extensions, and inter-lactocyte tight junction strain or rupture arising from elevated intraluminal pressure, also known as hydrostatic pressure;1, 2

3. Stromal substrate mechanics, that is, stromal tissue density and tension or pressure, including interstitial fluid tension or pressure, which act upon the easily compressed lactiferous ducts;

4. Environmental force on stroma and ducts, for example

   • Intra-oral mechanical forces during suckling,3-5

   • Direct external pressure on an area of the breast resulting in micro-vascular trauma and elevated stromal tension,6 or

   • Direct external pressure on an area of the breast resulting in prolonged ductal compression.

5. Effects of mechanical forces on the nipple of the lactating breast, either

   • Stretching of nipple epidermis, or

   • Deformational force applied to nipple stroma.

You can find out more about the frontier science of mechanobiology here.

Selected references

Douglas P. Re-thinking benign inflammation of the lactating breast: a mechanobiological model. Women's Health. 2022;18:17455065221075907.

Douglas PS. Re-thinking benign inflammation of the lactating breast: classification, prevention, and management. Women's Health. 2022;18:17455057221091349.

Douglas PS. Re-thinking lactation-related nipple pain and damage. Women's Health. 2022;18:17455057221087865.

Kim T-J. Mechanobiology: a new frontier in biology. Biology. 2021;10(570):https://doi.org/10.3390/biology10070570.

Kobayashi K, Han L, Lu S-N, Ninomiya K, Isobe N, Nishimura T. Effects of hydrostatic ompression on milk production-related signaling pathways in mouse mammary epithelial cells. Experimental Cell Research. 2023;432:113762.

Noam Zuela-Sopilniak, Lammerding J. Can’t handle the stress? Mechanobiology and disease. Trends in Molecular Medicine. 2022;28(9):710-725.

Stewart TA, Hughes K, Stevenson AJ, Marino N, Ju AL, Morehead M, et al. Mammary mechanobiology - investigating roles for mechanically activated ion channels in lactation and involution. Journal of Cell Science. 2021;134:doi:10.124/jcs.248849.