Autophagic Mediators in Bone Marrow Niche Homeostasis

P62/SQSTM1 enhances osteogenesis and attenuates inflammatory signals in bone marrow microenvironment

Bone marrow-derived mesenchymal/stromal stem cells (MSCs) became a major focus of research since the anti-inflammatory features and the osteogenic commitment of these cells can prevent the inflamm-aging and various form of osteopenia in humans and animals. We previously showed that p62/SQSTM1 plasmid can prompt release of anti-inflammatory cytokines/chemokines by MSC when injected in adult mice. Furthermore, it can enhance osteoblastogenesis at the expense of adipogenesis and ameliorate bone density and bone remodeling. On the other hand, absence of p62 partially exhausted MSC pool caused expansion of fat cells within bone marrow and pro-inflammatory mediator's accumulation. Given the critical function of p62 as molecular hub of MSC dynamics, here, using MSCs from p62 knockout adult mice, we investigated the effect of this protein on MSC survival and bone-forming molecule cascades. We found that the main osteogenic routes are impaired in absence of p62. In particular, lack of p62 can suppress Smads activation, and Osterix and CREBs expression, thus significantly modifying the schedule of MSCs differentiation. MSCs obtained from p62-/- mice have also demonstrate an amplified NFκB/ Smad1/5/8 colocalization along with NFκB activation in the nucleus, which precludes Smads binding to target promoters. Considering the "teamwork" of TGFβ, PTH and BMP2 on MSC homeostatic behavior, we consider that p62 exerts an essential role as a hub protein. Lastly, ex vivo pulsing p62-deficient MSCs, which then will be administered to a patient as a cell therapy, may be considered as a treatment for bone and bone marrow disorders.

P62/SQSTM1 beyond Autophagy: Physiological Role and Therapeutic Applications in Laboratory and Domestic Animals

Inflammation is the preceding condition for the development of mild and severe pathological conditions, including various forms of osteopenia, cancer, metabolic syndromes, neurological disorders, atherosclerosis, cardiovascular, lung diseases, etc., in human and animals. The inflammatory status is induced by multifarious intracellular signaling cascades, where cytokines, chemokines, arachidonic acid metabolites, adhesion molecules, immune cells and other components foster a “slow burn” at a local or systemic level. Assuming that countering inflammation limits the development of inflammation-based diseases, a series of new side-effects-free therapies was assessed in experimental and domestic animals. Within the targets of the drug candidates for quenching inflammation, an archetypal autophagic gear, the p62/sqstm1 protein, has currently earned attention from researchers. Intracellular p62 has been recently coined as a multi-task tool associated with autophagy, bone remodeling, bone marrow integrity, cancer progression, and the maintenance of systemic homeostasis. Accordingly, p62 can act as an effective suppressor of inflamm-aging, reducing oxidative stress and proinflammatory signals. Such an operational schedule renders this protein an effective watchdog for degenerative diseases and cancer development in laboratory and pet animals. This review summarizes the current findings concerning p62 activities as a molecular hub for cell and tissues metabolism and in a variety of inflammatory diseases and other pathological conditions. It also specifically addresses the applications of exogenous p62 (DNA plasmid) as an anti-inflammatory and homeostatic regulator in the treatment of osteoporosis, metabolic syndrome, age-related macular degeneration and cancer in animals, and the possible application of p62 plasmid in other inflammation-associated diseases.

Steering the multipotent mesenchymal cells towards an anti-inflammatory and osteogenic bias via photobiomodulation therapy: How to kill two birds with one stone

The bone marrow-derived multipotent mesenchymal cells (MSCs) have captured scientific interest due to their multi-purpose features and clinical applications. The operational dimension of MSCs is not limited to the bone marrow reservoir, which exerts bone-building and niche anabolic tasks; they also meet the needs of quenching inflammation and restoring inflamed tissues. Thus, the range of MSC activities extends to conditions such as neurodegenerative diseases, immune disorders and various forms of osteopenia. Steering these cells towards becoming an effective therapeutic tool has become mandatory. Many laboratories have employed distinct strategies to improve the plasticity and secretome of MSCs. We aimed to present how photobiomodulation therapy (PBM-t) can manipulate MSCs to render them an extraordinary anti-inflammatory and osteogenic instrument. Moreover, we discuss the outcomes of different PBM-t protocols on MSCs, concluding with some perplexities and complexities of PBM-t in vivo but encouraging and feasible in vitro solutions.