Monocytes are the target in the stroke since they are main cells of innate immunity which can also influence adaptive immunity (9). Monocytes can be differentiated to macrophages and dendritic cells, and they are critical when the immune response to pathogens and a number of endogenous molecules, such as heat-shock-protein, RNA, fibronectin, or fibrin, is initiated (10). In the current study, It is reported that ischemic stroke patient revealed an apparent decrease of adipose cells and hypercellularity with increased vascularity in bone marrow sections stained with Hx&E stain. Similar picture was detected by some investigators ( 11,12 &13). Yang et al. presumed that mononuclear cells within the bone marrow fraction may change in quantity and quality compared to the mononuclear nuclear bone marrow cells of healthy animals following a brain injury such as stroke. They investigated this problem by comparing mononuclear cells produced before and after a stroke from the same animals (13).
This is a key question, since a recent study showed that the stroke in leukocyte response fluencies is known to regulate the autonomic regulation of bone marrow by the central nervous system (12). Courties et al. stated that myeloid cells, particularly neutrophils and monocytes, increase in circulation after stroke. The ischemic brain is also recruited to these cells. Encouraged by observed the increase of the proliferation image signal. The hematopoietic progenitor cell activity of the animals with the stroke contributed to an increase in the colony numbers after 7days (14 &15).
Monocytes are characterized by the expression of several clusters of differentiation, such as CD115, CD11c, CD14 and CD16 in human or CD115, CD11b and Ly6C in rodent (16). Interestingly, the current study displayed an apparent increase of CD14 immunostained positive cells in ischemic stroke patients as compared to the control participants. In human, monocytes are regrouped in three main subsets based on their CD14 and CD16 expression levels, which are the classical subset (CD14++CD16−), the intermediate subset (CD14++CD16+) and the non-classical subset (CD14+CD16++) ( 17 ).
CD68 is a microglia/macrophage marker related to lysosomal glycoproteins that shuttles in vesicles between lysosomes, endosomes, and the plasma membrane (18). For this reason, various studies (19 & 20), in addition to our results, detected increase in CD68 positive staining in the cytosol oamongf the bone marrow cells. Previous studies have shown that 3–7 days after middle cerebral artery occlusion, blood-derived macrophages were expressed abundantly, even though they were hardly distinguishable from CD68 positive cells ( 21).
The present findings demonstrate that monocytes increased within two days in the patients with ischemic stroke. Also, the percentages of intermediate monocyte are increased, but non-classical monocyte was decreased, and classical monocyte were unchanged compared to the control. Our results agree with those reported by Urra et al., (2009) (22) and ( 23 ), except that for the Kaito et al., study finding that the CD14highCD16- classical Monocyte subtype was increased, which could be attributed to the used monoclonal antibodies in that phenotyping study.
The present study found that the non-classical, CD14lowCD16 + monocyte subpopulation decrease in ischemic stroke patients where they exhibit lower expression levels of Tie2 than other monocyte subsets. Non-classical monocyte elevated in other diseases such as atherosclerosis rheumatoid arthritis, sepsis patients, HIV infection and Patients with active SLE ( 24; 25 ; 26, 27, 28 & 29). As such, expansion of non-classical monocytes may be a general phenomenon of inflammatory and infectious diseases. However, their role in the manifestations or propagation of these diseases is unclear (30, 31).
The main finding of the current study is that the expression levels of Tie2 dysregulated on different monocytes subpopulations from ischemic stroke cases as compared to normal subjects (32, 33). The monocytes subsets skewed in stroke patients with expressing higher proportions of angiogenic subset (TEMs) than inflammatory subset (34). TEMs are a subgroup of circulating and tumor-infiltrating myeloid cells with potent proangiogenic activity (35, 36). The examination indicates that the Tie2 expressing monocytes are believed to be integral when it comes to the development of tumor blood vessel as well as emphasize on the possible target to manage tumor angiogenesis and growth ( 35, 36 ). The study demonstrates that although TEMs numbers are more than 10-fold higher in the patients that have CLI compared to those in matched controls, with the variance in muscle while significant is less established. Instances of poor limb perfusion occasioned by the consent of critical ischemia could indeed result in curtailing of the TEMs recruitment to the ischemic limb in the CLI patients. Poor limb perfusion is additionally considered accountable for the lack of muscle revascularization despite the instances of increased levels of circulating angiogenic (37).
In addition, it is possible that the TEMs recruited do not survive in the unreceptive environment of the ischemic muscle following the recruitment. It is essential to acknowledge that the increase in circulation of TEMs members could only be linked to the presence of vital ischemia instead of the severity. It was further established that there were no prevalent clinical manifestations correlated with a circulation of TEM (37, 38, 39).
Data from the prevailing study indicates that TEMs decline into both the CD16 + monocyte subset that was established depending on the intensity of expression of CD14 + + CD16 + along with the intermediate CD14 + + CD16 + cells. It follows that the intermediate monocyte subset has demonstrated to differentially indicate the high levels of TIE2 and other proangiogenic genes that include endoglin as well as VEGFR2 (40, 41).
For future studies, it is recommended to design functional studies via in vitro angiogenesis assay using tube formation assay. Those studied will evaluate the effect of monocytes from stroke patients on angiogenesis of the brain endothelial cells; and if this will be mediated by Tie2.