Clarifying the present status of stem cell use in spinal surgery

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David A Wong

The use of stem cells in spinal surgery was a focus of discussion at both the Brussels International Spine Symposium (BISS; 20-21 November, Brussels, Belgium), and the Annual Meeting of the North American Spine Society (NASS; 14-17 October, Chicago, USA). David Wong explores the current status of stem cells in spinal surgery.

“Disappointment” and “promise” were the messages concerning stem cell use in the spine from BISS.

As always, co-chairmen Robert Gunzburg, Marek Szpalski and Jean-Charles Le Huec assembled an outstanding international faculty to address this year’s theme, “New Technologies in Spine Surgery”. Stem cells and biologics was a subtopic of emphasis with several interesting observations and conclusions coming from the presentations.

From my perspective, the area of “disappointment” was that of stem cell injections as a primary treatment to stimulate the formation of cells in an anatomic location having primarily a single cell type.

We now have the expertise to isolate and concentrate stem cells, as was outlined by Caroline Szspalski (Université Libre de Bruxelles, Brussels, Belgium). The initial experimental premise concerning largely single cell type pathology has been that the local tissue would have sufficient RNA messenger to turn on targeted DNA in the stem cells to produce the desired cell type. A recorded talk by Scott Blumenthal (Texas Back Institute, Dallas, USA) and a slideshow sent in by Alexander Vaccaro (Jefferson University Hospitals, Philadelphia, USA) commented on this issue.

Results of stem cells into the intervertebral disc have been sufficiently inconsistent for the US Food and Drug Administration (FDA) to essentially cease these injection trials. Some US stem cell injection centres have moved operations out of the USA. I only know of one FDA-sanctioned phase III investigational new drug study of stem cell injection into the disc space, sponsored by Mesoblast. There are still some trials ongoing in Europe.

 

Eric Muehlbauer, executive director, NASS, discussed “navigating the regulatory and reimbursement systems” for technology innovation generally, and not just for stem cells.

Spinal cord injury has been the other area where stem cell treatment alone has, regrettably, not made a significant impact. Nachshon Knoller (Chaim Sheba Medical Center, Tel-Hashomer, Israel)) also discussed the role of incubated autologous macrophages in modulating the immune response to spinal cord injury in order to facilitate neurologic recovery. The initial pilot study showed promise, but the randomised controlled trial that followed was, again, a disappointment.

The “promise” concerning stem cells in spinal surgery surrounds their use as an adjunct to fusion processes already set in motion.

Both the use of autologous stem cells and allograft cultured stem cells are in clinical trials. Embryonic as well as adult stem cells (usually from fat or bone marrow) are being studied. My research partner, Gary Ghiselli, is the Denver primary investigator for the Mesoblast study of allogenic adult mesenchymal precursor stem cells. The adult stem cells are cultured to increase their number before implantation. These are being investigated as an adjunct to primary fusion in both the lumbar and cervical spine. The preliminary Denver data was shown at BISS, as well as the national results presented at the NASS annual meeting.1 The national lumbar randomised control trial showed 75% fusion in the autograft alone control group, 85.7% fusion in the treatment group adding 25 million stem cells but only 62.5% fusion  when 75 million stem cells were used.

Though clearly “promising”, the data shows there are still multiple issues to be investigated in the use of stem cells in the spine. These include establishing a dose response curve, cell viability, nutrition, carrier/method of implantation and how to stimulate the desired outcome (e.g. stimulating osteoblast vs. chondrocyte formation).

Helena Brisby (University of Gothenburg, Sweden) posed the ultimate question in her talk, “Biological treatments for spinal disorders – is it going to happen?” Her answer—and the consensus of the audience discussion—was definitely “yes”. The remaining, and so far unanswerable, issue is “when?”

References

  1. G Ghiselli etal. Presented by HW Bae at the North American Spine Society 30th Annual Meeting (12–15 November 2014, San Francisco, USA).

David A Wong is director of the Advanced Center for Spinal Microsurgery, Presbyterian St. Luke’s Medical Center, Denver, USA. He is also a past president of NASS