Engineering macrophages to control the inflammatory response and angiogenesis

Abstract

Macrophage (MΦ) dysregulation is increasingly becoming recognized as a risk factor for a number of inflammatory complications including atherosclerosis, cancer, and the host response elicited by biomedical devices. It is still unclear what roles the pro-inflammatory (M1) MΦ and pro-healing (M2) MΦ phenotypes play during the healing process. However, it has been shown that a local overabundance of M1 MΦs can potentially lead to a chronically inflamed state of the tissue; while a local over-exuberant M2 MΦ response can lead to tissue fibrosis and even promote tumorigenesis. These notions strengthen the argument that the tight temporal regulation of this phenotype balance is necessary to promote inflammatory resolution that leads to tissue homeostasis. In this study, we have engineered pro-inflammatory MΦ, MΦ-cTLR4 cells, which can be activated to a M1-like MΦ phenotype with a small molecule, the chemical inducer of dimerization (CID) drug. The MΦ-cTLR4 cells when activated with the CID drug, express increased levels of TNFα, IL-6, and iNOS. Activated MΦ-cTLR4 cells stay stimulated for at least 48 hours; once the CID drug is withdrawn, the MΦ-cTLR4 cells return to baseline state within 18 hours. Further, in vitro CID-activated MΦ-cTLR4 cells induce upregulation of VCAM-1 and ICAM-1 on endothelial cells (EC) in a TNFα-dependent manner. With the ability to specifically modulate the MΦ-cTLR4 cells with the presence or absence of a small molecule, we now have the tool necessary to observe a primarily M1 MΦ response during inflammation. By isolating this phase of the wound healing response, it may be possible to determine conditions for ideal healing.

In vivo structural and cellular remodeling of engineered bone–ligament–bone constructs used for anterior cruciate ligament reconstruction in sheep

“…While the overall macrophage percentage remained similar between the 7 and 14-day time points, there was a decline in M2 macrophages from 6.69 ± 3.99% to 3.00 ± 1.65%, suggesting tissue regeneration had begun. While M2 macrophages are known for matrix deposition and tissue healing, an overabundance of M2 macrophages can lead to excessive fibrosis 16,17 , with the balance between M1 and M2 macrophages critical to equilibrium. Therefore, a shift in macrophage type away from a high M2 macrophage population at this time point could indicate a return to an equilibrium between pro and anti-inflammatory macrophages and less fibrosis throughout construct remodeling.…”

“…Neutrophils and macrophages likely contribute to removal of graft-derived cells, removal of cellular debris and instigate the repopulation of these constructs by host-derived cells. Foreign tissue can induce inflammation with varied response by macrophage type; pro-inflammatory macrophages (M1) and anti-inflammatory macrophages (M2) are integral components of these inflammation-related regenerative processes 13–17 . M1 macrophages secrete inflammatory cytokines and nitric oxide, promoting pathogen destruction, while M2 macrophages promote matrix deposition for tissue remodeling.…”

“…M1 macrophages secrete inflammatory cytokines and nitric oxide, promoting pathogen destruction, while M2 macrophages promote matrix deposition for tissue remodeling. 13–17 Therefore, characterizing the timing of immune cells presence within our BLB constructs in vivo helps identify the host immune system’s role in the maturation of the graft tissue. A more complete understanding of the graft-host response is critical for bringing this BLB technology toward clinical application.…”

Role of liver ICAM-1 in metastasis

“…Moreover, ICAM-1 can cooperate with other adhesion molecules, such as VCAM-1, in the adhesion of malignant cells. ICAM-1 and VCAM-1 are both upregulated in a TNF-α-dependent manner (TNF-α being predominantly produced by macrophages) (57). Notably, LSECs lack the ability to express selectins, which are basally expressed and inducible in the endothelium of the portal tract and central vein (58).…”

In Vivo and in Vitro Studies of the Effect of Chitosan on the Bone Defect Repair Process

“…Сильный противовоспалительный эффект, который наблюдался при использовании барье-ров из ХТЗ, по всей видимости, был обусловлен способностью молекул гетерополисахарида индуцировать альтернативную активацию тка-невых макрофагов (М2), которые, как известно, нивелируют воспаление, стимулируют процессы репарации и регенерации поврежденных тканей через продукцию ряда хемокинов, ангиогенных факторов (VEGF), аргиназы-1, но не ФНОα и ИЛ-1β [9][10][11]. Поэтому в пользу ранней инициации репаративно-регенерационных процессов у кро-ликов из группы №2 свидетельствует не только крайне низкий уровень провоспалительных ци-токинов в крови на 3-и сутки, но и рост концен-трации VEGF.…”