Do not index
By Karen Rea FNP-BC
If you have ever watched someone struggle to regain feeling in a hand, lift a foot that simply won't respond, or live with the burning ache of chronic nerve pain, you already understand why peripheral nerve injury is one of the more frustrating problems in medicine. Nerves don't heal the way skin or even bone does. The body has a stubbornly limited capacity to rebuild them, and when the damage is severe, the deficits can last a lifetime.
That is exactly why a systematic review I've been reading lately caught my attention. Published in the World Journal of Stem Cells by Bojanic and colleagues out of the University of Cambridge, the paper asks a deceptively simple question: can mesenchymal stem cells harvested from the human umbilical cord actually help damaged peripheral nerves regenerate? I want to walk you through what they found, because the answer is genuinely encouraging, and because I think it points toward where regenerative medicine is heading.
Why nerve injuries are so hard to fix
Peripheral nerve damage shows up after all kinds of trauma and disease, and it carries real morbidity, sensory loss, motor loss, and chronic pain that can be debilitating. The review notes that these injuries lead to lifelong disability in a meaningful fraction of trauma patients. The mechanisms behind poor recovery are layered: sluggish nerve regeneration, muscle wasting, and degeneration of the connection points between nerve and muscle.
The traditional toolbox is not great. Neurolysis, surgical suturing of the nerve ends, and nerve grafts taken from elsewhere in the patient's own body are the standard approaches, and even in the best surgical hands they tend to deliver partial recovery rather than full function. Autografts come with their own baggage: pain at the donor site, size mismatch between the graft and the nerve, and the risk of painful neuromas forming. Some injuries, like severe brachial plexus damage or long traction injuries, are essentially inoperable. So there is a clear, unmet need for something better.
Where stem cells enter the picture
This is where mesenchymal stem cells, or MSCs, come in. They are multipotent cells that can be drawn from bone marrow, fat, dental pulp, amniotic fluid, and the umbilical cord, and they have earned a reputation for their regenerative potential. The umbilical cord versions, called UCMSCs, are particularly appealing for a few reasons the authors lay out clearly.
For one, they are easy to obtain. Umbilical cords and cord blood are generally treated as medical waste, which means harvesting the cells raises very few ethical concerns and adds no risk to a donor. UCMSCs also expand readily in the lab, and they express low levels of the immune marker HLA-DR, which lowers the risk of rejection when transplanted between different people. On top of that, they appear to have stronger paracrine effects than bone marrow or fat-derived cells, meaning they secrete a rich mix of growth factors and signaling molecules that coax surrounding tissue into repairing itself. They can even be nudged into Schwann-like cells, the support cells that are central to nerve repair.
What the review actually found
The Cambridge team followed the rigorous PRISMA methodology and combed through the literature up to September 2019, ultimately including 14 studies covering 279 subjects, both animal and human. Here is the headline: every single one of those studies reported significant improvement in nerve regeneration in the UCMSC-treated groups compared with controls. No study reported significant complications, and none reported immune rejection.
Digging into the details, the researchers grouped the studies by injury type. In crush-injury models, direct injection of UCMSCs improved the sciatic function index, axon counts, and axon density, with one clever study showing that cells engineered to overexpress brain-derived neurotrophic factor (BDNF) did even better. In more severe transection injuries, teams delivered the cells using all sorts of scaffolds and conduits, silicone tubes, collagen conduits, chitosan, amniotic membrane, with consistently positive results across measures like myelin sheath thickness, nerve conduction, and motor and sensory recovery.
The piece that stands out most to me is a human study included in the review. Patients with radial nerve injuries from fractures received UCMSCs loaded onto an amniotic membrane after their scar tissue was cleared, and compared with patients who got the standard procedure alone, the cell-treated group showed better muscle strength, better touch and pain sensation, and improved electrical function in the nerve. Seeing the animal findings begin to echo in actual patients is what makes this field feel less like a promise and more like a trajectory.
The honest caveats
I appreciate that the authors didn't oversell their conclusions, and neither will I. Thirteen of the fourteen studies carried a moderate risk of bias, and one was rated high. There was significant variability in how cells were treated and delivered, which makes it impossible to declare one best method yet. Most studies used rodent sciatic nerves, and the critical gap a nerve can bridge on its own is larger in mice than in humans, so animal results may flatter the real therapeutic potential. We still don't fully understand the mechanism, whether the transplanted cells replace damaged tissue directly or, more likely, work through the signaling molecules and extracellular vesicles they release.
In other words, the evidence is genuinely promising, but the work of translating it into reliable, standardized human treatment is still ahead of us. What we need now are robust in vivo models, consistent ways to measure regeneration, and high-quality randomized controlled trials with long-term follow-up.
Why I find this exciting
Step back from the caveats for a moment and look at the shape of the thing. We have an abundant, ethically uncomplicated cell source that is easy to collect and expand, carries low immune risk, and produces a consistent regenerative signal across more than a dozen independent studies. That is a strong foundation. The questions that remain are the right kind of questions, refining delivery, scaling to humans, nailing down mechanism, rather than questions about whether the basic effect is real.
For those of us watching regenerative medicine mature, peripheral nerve repair is a beautiful test case. It's a problem the body genuinely cannot solve on its own, and here is a tool that keeps showing it can help tip the balance toward healing. I'll be following this closely, and I suspect the next few years of clinical research will be worth paying very close attention to.
Keep learning with us
If this kind of science excites you the way it excites me, come join the conversation where it's happening.
The Regen Summit brings together clinicians, researchers, and practitioners who are pushing regenerative medicine forward, the perfect place to dig deeper into topics like the one above. Learn more and register at RegenEvent.com.
And for hands-on, practical training, check out the MIT Skool Platform, our community for mastering injection technique and regenerative protocols. Join us at skool.com/myinjectiontraining.
I hope to see you there.
— Karen Rea
This blog summarizes findings from Bojanic C, To K, Zhang B, Mak C, Khan WS. "Human umbilical cord derived mesenchymal stem cells in peripheral nerve regeneration." World J Stem Cells. 2020;12(4):288-302. It is intended for educational purposes and is not medical advice.