1. Field of the Invention
This invention relates to the controlled application of therapeutic light energy. More particularly, this invention relates to the therapeutic irradiation of marrow-containing bone using infrared light and energy of other wavelengths.
2. Description of the Related Art
The meanings of certain acronyms and abbreviations used herein are given in Table 1.
TABLE 1Acronyms and AbbreviationsATPadenosine tri-phosphateBMbone marrowECHO echocardiographicICRimprinting control regionIRinfraredIRIIschemia reperfusion injuryLADanterior descending branch of left coronary arteryLEDlight-emitting diodeLLLTlow level laser therapyLVLeft ventricleMImyocardial infarctionMSCmesenchymal stem cellSEMstandard error of the mean
The bone marrow is a complex tissue featuring several different types of primitive cells: hematopoietic stem cells, mesenchymal stem cells (MSCs), endothelial progenitor cells, side population cells, and multipotent adult progenitor cells. Like other stem cells, mesenchymal stem cells are capable of multilineage differentiation from a single cell and in vivo functional reconstitution of injured tissues. One of the properties of stem cells is their capacity to migrate after infusion to one or more appropriate microenvironments. Certain stem cells are able to exit their production site, circulating in the blood before reseeding in their target tissues. For mesenchymal stem cells, the nature of homing sites and circulation into peripheral blood is still under debate. However, mesenchymal stem cells have been found after infusion in multiple tissues, leading to the hypothesis that they can home, and that they adjust their differentiation pathways to diverse tissue microenvironments.
In the last decade cellular therapy for cardiac repair has undergone rapid transition from basic science research to clinical reality. The approach to cardiac repair based on stem cells was first realized via early studies that induced in-vitro differentiation of stem cells into cardiomyocytes. Orlic et al. first reported that injection of bone marrow cells with specific markers (Lin−/c-kit+) to hearts following induction of myocardial infarction resulted in reconstitution of 68% of the infarcted myocardium, the formation of new blood vessels, improvement in left ventricle function and attenuation of remodeling (Orlic D, Kajstura J, Chimenti S, Jakoniuk I, Anderson S M, Li B, Pickel J, McKay R, Nadal-Ginard B, Bodine D M, Leri A, Anversa P. Bone Marrow Cells Regenerate Infarcted Myocardium. Nature. 2001; 410:701-5. In another study MSCs were injected intravenously into rat hearts (Bittira B, Shum-Tim D, Al-Khaldi A, Chiu R C. Mobilization and Homing of Bone Marrow Stromal Cells in Myocardial Infarction. Eur. J. Cardiothorac Surg. 2003; 24(3):393-8). It was found that labeled cells were seen in and near the infarct up to eight weeks post myocardial infarction, while none was seen in sham-operated hearts. It was concluded that following myocardial infarction, mesenchymal stem cells are signaled and recruited to the injured heart, where they undergo differentiation and may participate in the remodeling process.