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Friday, July 25, 2008

What is regenerative medicine by any other name?

Whether you say potāto or potäto we all know what you mean. But when someone says they're in regenerative medicine is that somehow different than cell therapy? And how does that differ from tissue engineering? And where does the stem cell industry and gene therapy fit into the mix? We do need to settle into a nomenclature paradigm for this industry. It won't just help us in the industry, its bound to help those trying to understand it - perhaps even an investor or two!

In the concluding paragraph of her 2004 book, The Proteus Effect, Ann B. Parson states:

“Some biologists believe that the greatest legacy of stem cells will lie in their therapeutic value. Others say their best gift will be what they can tell us about the miracle of Life, and how a tiny cell has the wherewithal to grow into a thriving form, of whatever nature. Other biologists instead look at a stem cell as the immortal cell that will extend human life indefinitely and reveal aging to be a mere aberration.’

The cell therapy or regenerative medicine industry indeed embraces at least all those views of cell-based research. The industry is a wide-ranging collective of research using a wide variety of technologies to repair, restore, replace, and/or regenerate human biological systems. The wide scope of the field has recently motivated a few forward-thinking individuals in the industry to attempt to define the industry and encourage a consensus of nomenclature.

After reviewing the history of the sector and several approaches to its definition, Mason & Dunhill recently proposed to define the sector simply as follows:

“Regenerative medicine replaces or regenerates human cells, tissue, or organs, to restore or establish normal functions.” [ii]

This definition, and their “regen” abbreviation for the industry, has been adopted by the BSI (British Standards) in its Publicly Available Specification (PAS) 84:2008.[iii]

This kind of formal adoption of definitions and how the primary terms interrelate and overlap will help this incipient industry.

The regen industry has spawned from and is increasingly about the convergence of three distinct technologies: stem cell transplant, tissue engineering, and biomaterials.

There is, of course, entrenched intransigence among the leading orgs representing the field in that ISSCR really sees the world through a stem cells lens, ISCT sees the field as cell therapy, TERMIS sees the world of tissue engineering as more encompassing than most, AABB believe its all very closely related to blood banking, and BIO hasn't really figured how to properly engage or represent the field given its relative unimportance as yet to their overarching mandate.

This does raise the need for an overarching industry org but that will be the subject for an upcoming blog.

While the term ‘regen’ appears to have spawned more directly from the tissue engineering sector which was one of the early names for the sector (see cover of TIME magazine 22 May 2000), "tissue engeering" now seems to be falling into place as a subset of regen – one that focuses on the engineering of tissues often by or in conjunction with physical devices or matrices. Having said that, tissue engineering was recently broadly defined by a multi-agency task force of the US government as “the use of physical, chemical, biological, and engineering processes to control and direct the aggregate behavior of cells”.[iv]

Notwithstanding such efforts to define tissue engineering broadly, the two terms that appear to be emerging as the overarching title for the industry are “cell therapy” and “regenerative medicine” (or its abbreviation “regen”). The former appears to have arisen primarily from the cell transplant community and the latter out the tissue and biomaterials sectors. Some, like Proteus Venture Partners, define cell therapy as a subset of the regenerative medicine industry.101 Others (like myself) have tended – perhaps sloppily – to use the two terms rather synonymously and interchangeably.

If we define regen as Mason & Dunhill do above, cell therapy is clearly a subset of regenerative medicine. Cell therapy is always about the ‘replacement or regeneration of human cells, tissue, or organs, to restore or establish normal function’. Regenerative medicine, however, may or may not use cells as the vehicle for doing so[v]. Regenerative medicine may use small molecule activators, non-cell-based gene therapy, and/or non-cellularized biomaterials.

Notwithstanding the utility of such definitions, distinctions are increasingly blurring because of the interdisciplinary mechanisms now being employed in many advanced regenerative medicines like cellularized matrices, cell-based gene therapies, cell therapies accompanying small-molecule activator therapies, small-molecule regimens supporting accompanying cell therapies, etc.

All the more need for an overarching nomenclature. Let me know your thoughts...

[i] Parson AB: The Proteus effect: stem cells and their promise for medicine. Joseph Henry Press (2004).

[ii] Mason C, Dunnhill P: A brief definition of regenerative medicine. Regen. Med. 3, 1-5 (2008).

[iii] Publicly Available Specification (PAS) 84:2008: Regenerative medicine – Glossary. British Standards (BSi) (April 2008).

[iv] Advancing Tissue Science and Engineering: A Muliti-Agency Strategic Plan. Mulit-Agency Tissue Engineering Sciences (MATES) Interagency Working Group (IWG) under the National Science and Technology Council of the Committee on Science of the Subcommitee on Biotechnology. June 2007.

[v] BSi’s PAS 84:2008 defines “cell therapy” as ‘administration of cells to the body to the benefit of the recipient” and defines “cell based medicinal product (CBMP)” as a “medicinal product containing cells” noting that “these products may be combined with non-cellular components and may include genetically modified human cells” which it states is “derived from the European Medicines Agency’s Guideline on Human Cell-Based Medicinal Products [EUROPEAN MEDICINES AGENCY (EMEA). Committee for medicinal products for human use (CHMP). Guideline on Human Cell-Based Medicinal Products. Consultation draft issued 25 January 2007. London: EMEA, January 2007.]