Abstract
The bone marrow is an important site where all blood cells are formed from hematopoietic stem cells and where hematologic malignancies such as leukemia emerge. It is also a frequent site for metastasis of solid tumors such as breast cancer and prostate cancer. Intravital microscopy is a powerful tool for studying the bone marrow with single cell and sub-cellular resolution. To improve optical access to this rich biological environment, plasma-mediated laser ablation with sub-microjoule femtosecond pulses was used to thin cortical bone. By locally removing a superficial layer of bone (local laser osteotomy), significant improvements in multiphoton imaging were observed in individual bone marrow compartments in vivo. This work demonstrates the utility of scanning laser ablation of hard tissue with sub-microjoule pulses as a preparatory step to imaging.
Highlights
The concept of stem cell niches, where stem cells reside, implies that the position of cells in biological tissue regulates their function
Confocal and multiphoton scanning microscopy are commonly used to describe the microenvironment of hematopoietic stem/progenitor cells (HSPC) and cancer cells in the bone marrow (BM) [1,2,3]
Local laser osteotomy was successfully performed with 0.3 μJ pulses (10 J/cm2 fluence)
Summary
The concept of stem cell niches, where stem cells reside, implies that the position of cells in biological tissue regulates their function. Osteotomy has been performed for decades with mechanical tools and found many applications [6, 7]. Cranial osteotomy has served as a means to increase access to the central nervous system by removing most of the overlying bone, including the BM space [8,9]. Multiple protective layers of the central nervous system separate bone from the brain (dura mater, arachnoid membrane and pia mater), mechanical osteotomy can have deleterious effects on the brain [6,10,11]. For imaging the BM, which is located 50-75 μm below the bone surface in the skull, the precision required to remove less than 50 μm of hard cortical and spare the BM from damage by far exceeds the capability of mechanical tools
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