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Progenitor cell therapy describes the use of multipotent cells of various cell lineages (autologous or allogeneic) for tissue repair and/or regeneration. Progenitor cell therapy is being investigated for the treatment of damaged myocardium resulting from acute or chronic cardiac ischemia.
Ischemia is the most common cause of cardiovascular disease and myocardial damage in the developed world. Despite impressive advances in treatment, ischemic heart disease is still associated with high morbidity and mortality. Current treatments for ischemic heart disease seek to revascularize occluded arteries, optimize pump function, and prevent future myocardial damage. However, current treatments are not able to reverse existing damage to heart muscle. Treatment with progenitor cells (i.e., stem cells) offers potential benefits beyond those of standard medical care, including the potential for repair and/or regeneration of damaged myocardium. Potential sources of embryonic and adult donor cells include skeletal myoblasts, bone marrow cells, circulating blood-derived progenitor cells, endometrial mesenchymal stem cells (MSCs), adult testis pluripotent stem cells, mesothelial cells, adipose-derived stromal cells, embryonic cells, induced pluripotent stem cells, and bone marrow MSCs, all of which are able to differentiate into cardiomyocytes and vascular endothelial cells.
The mechanism of benefit following treatment with progenitor cells is not entirely understood. Differentiation of progenitor cells into mature myocytes and engraftment of progenitor cells into areas of damaged myocardium has been suggested in animal studies using tagged progenitor cells. However, there is controversy concerning whether injected progenitor cells actually engraft and differentiate into mature myocytes in humans to a degree that might result in clinical benefit. It also has been proposed that progenitor cells may improve perfusion to areas of ischemic myocardium. Basic science research also suggests that injected stem cells secrete cytokines with antiapoptotic and pro-angiogenesis properties. Clinical benefit may result if these paracrine factors limit cell death from ischemia or stimulate recovery. For example, myocardial protection can occur through modulation of inflammatory and fibrogenic processes. Alternatively, paracrine factors may affect intrinsic repair mechanisms of the heart through neovascularization, cardiac metabolism and contractility, increase in cardiomyocyte proliferation, or activation of resident stem and progenitor cells. The relative importance of these proposed paracrine actions depends on the age of the infarct, eg, cytoprotective effects in acute ischemia and cell proliferation in chronic ischemia. Investigation of the specific factors induced by administration of progenitor cells is ongoing.
There also are a variety of potential delivery mechanisms for donor cells, encompassing a wide range of invasiveness. Donor cells can be delivered via thoracotomy and direct injection into areas of damaged myocardium. Injection of progenitor cells into the coronary circulation also is done using percutaneous, catheter-based techniques. Finally, progenitor cells may be delivered intravenously via a peripheral vein. With this approach, the cells must be able to target damaged myocardium and concentrate at the site of myocardial damage.
Adverse effects of progenitor cell treatment include the risks of the delivery procedure (e.g., thoracotomy, percutaneous catheter-based) and risks of the donor cells themselves. Donor progenitor cells can differentiate into fibroblasts rather than myocytes. This may create a substrate for malignant ventricular arrhythmias. There is also a theoretical risk that tumors, such as teratomas, can arise from progenitor cells, but the actual risk in humans is not known at present.
U.S. Food and Drug Administration (FDA) marketing clearance is not required when autologous cells are processed on site with existing laboratory procedures and injected with existing catheter devices. However, there are several products that require FDA approval. MyoCell® (BioHeart Inc., Sunrise, FL) comprises patient autologous skeletal myoblasts that are expanded ex vivo and supplied as a cell suspension in a buffered salt solution for injection into the area of damaged myocardium. MyoCell SDF-1 (BioHeart Inc.) is similar to MyoCell®, but before injection, myoblast cells are genetically modified to release excess stromal-derived factor (SDF)-1. Increased SDF-1 levels at the site of myocardial damage may accelerate recruitment of native stem cells to increase tissue repair and neovascularization. For both products, myoblast isolation and expansion occur at a single reference laboratory (BioHeart); both products are therefore subject to FDA approval. Currently, neither product is FDA-cleared. Implantation may require use of a unique catheter delivery system, MyoCath (BioHeart Inc.), that is FDA-cleared.
An allogeneic human mesenchymal stem cell (hMSC) product (Prochymal®) is being developed by Osiris Therapeutics, Inc. (Baltimore, MD) for treatment of acute myocardial infarction (AMI). Prochymal (also referred to as Provacel®) is a highly purified preparation of ex vivo cultured adult hMSCs isolated from the bone marrow of healthy young adult donors. Prochymal® has been granted “fast track” status by the FDA for Crohn disease and graft-versus-host disease (GVHD), and has orphan drug status for GVHD from FDA and the European Medicines Agency. Prochymal® is being studied in phase 2 trials for the treatment of AMI, pulmonary disease, and type 1 diabetes.
MultiStem® (Athersys) is an allogeneic bone marrow-derived adherent adult stem-cell product. MultiStem® has received orphan drug status from FDA for GVHD and has received authorization from FDA for a phase 2 trial for treatment of AMI with an adventitial delivery system.
POLICYProgenitor cell therapy, including but not limited to skeletal myoblasts or hematopoietic stem cells, is considered investigational as a treatment of damaged myocardium.
Infusion of growth factors (i.e., granulocyte colony stimulating factor [GCSF]) is considered investigational as a technique to increase the numbers of circulating hematopoietic stem cells as treatment of damaged myocardium.
POLICY GUIDELINESInvestigative service is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized by certifying boards and/or approving or licensing agencies or published peer review criteria as standard, effective medical practice for the treatment of the condition being treated and as such therefore is not considered medically necessary.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
POLICY HISTORY7/15/2004: Approved by Medical Policy Advisory Committee (MPAC)
10/5/2004: Code Reference section completed
3/15/2006: Policy reviewed, no changes
7/22/2008: Policy reviewed, no changes
8/10/2009: Policy Title revised to add "Progenitor" and "due to Ischemia", Policy Description Section updated to add research information on various types of autologous cell tranplantation and adverse effects of treatment with progenitor cells, Verbage, " Investigational for all uses", added to Non-Covered ICD-9 Diagnosis codes Section.
07/16/2010: Policy reviewed; no changes.
08/02/2011: Policy reviewed; no changes.
07/17/2012: Policy reviewed. Deleted "Autologous" from the policy title and statement. Deleted outdated references from the Sources section.
09/03/2013: Policy reviewed; no changes.
08/06/2014: Policy reviewed; description updated regarding products. Policy statement unchanged.
SOURCE(S)Blue Cross Blue Shield Association policy # 2.02.18
CODE REFERENCEThis may not be a comprehensive list of procedure codes applicable to this policy.
There are no specific codes for this procedure, either describing the laboratory component of processing the harvested autologous cells, or for the implantation procedure. The laboratory component may be reported with the stem cell procedure codes (38204, 38206, 38207, 38208, 38209, 38210, 38211, 38212, 38213, 38214, 38215, 38230, 38241). In some situations, the implantation may be an added component of a scheduled coronary artery bypass graft (CABG), in other situations the implantation may be performed as a unique indication for a cardiac catheterization procedure.