Impact of Digestive Inflammatory Environment and Genipin Crosslinking on Immunomodulatory Capacity of Injectable Musculoskeletal Tissue Scaffold

The paracrine and autocrine processes of the host response play an integral role in the success of scaffold-based tissue regeneration. Recently, the immunomodulatory scaffolds have received huge attention for modulating inflammation around the host tissue through releasing anti-inflammatory cytokine. However, controlling the inflammation and providing a sustained release of anti-inflammatory cytokine from the scaffold in the digestive inflammatory environment are predicated upon a comprehensive understanding of three fundamental questions. (1) How does the release rate of cytokine from the scaffold change in the digestive inflammatory environment? (2) Can we prevent the premature scaffold degradation and burst release of the loaded cytokine in the digestive inflammatory environment? (3) How does the scaffold degradation prevention technique affect the immunomodulatory capacity of the scaffold? This study investigated the impacts of the digestive inflammatory environment on scaffold degradation and how pre-mature degradation can be prevented using genipin crosslinking and how genipin crosslinking affects the interleukin-4 (IL-4) release from the scaffold and differentiation of naïve macrophages (M0). Our results demonstrated that the digestive inflammatory environment (DIE) attenuates protein retention within the scaffold. Over 14 days, the encapsulated protein released 46% more in DIE than in phosphate buffer saline (PBS), which was improved through genipin crosslinking. We have identified the 0.5 (w/v) genipin concentration as an optimal concentration for improved IL-4 released from the scaffold, cell viability, mechanical strength, and scaffold porosity, and immunomodulation studies. The IL-4 released from the injectable scaffold could differentiate naïve macrophages to an anti-inflammatory (M2) lineage; however, upon genipin crosslinking, the immunomodulatory capacity of the scaffold diminished significantly, and pro-inflammatory markers were expressed dominantly.

[THE SYSTEMIC IMMUNITY CELLULAR LINK REACTION IN PATIENTS WITH TRAUMATIC ILLNESS]

The effect of trauma on parameters of cellular immunity changes is studied. The study includes 52 patients with various forms of traumatic illness, aged 18-69 years (37.91-4.28). The control group consisted of 16 patients who underwent routine surgery not related to the pathology of musculoskeletal system. All patients of the main group were divided into 3 groups according to severity of the condition. Analysis of parameters of cellular link of immune system was performed by defining subpopulations of T-lymphocytes in indirect immunofluorescence method using a panel of monoclonal antibodies for CD3, CD4, CD8, CD22 lymphocytes' receptors and calculation of integrated indicators. The highest expression (immune disorders of II-III grades) of changes of cellular immunity observed in patients with severe traumatic: illness (expand clinical picture). Surgical intervention, even without traumatic injury significantly impact cellular immunity, but in patients with traumatic illness immunity violation were significantly higher than in comparison groups patients except immunoregulatory index.

The immune response: the afferent arm

The key to understanding afferent immunity is the mechanism of activation of T lymphocytes by specialized antigen presenting cells, which bind antigenic peptide to Class II major histocompatibility molecules, and stimulate T cells via Signal 1 (antigen) and Signal 2 (costimulation). The best studied costimulatory pathway is the interaction of B7-1 or B7-2 ligand molecules on antigen presenting cells with CD28 or CTLA-4 receptors on T cells. T cell signaling occurs through the T cell receptor-CD3 complex and is augmented by cosignaling via CD4, CD8, and CD45. The activation of T cells to alloantigen occurs by either a direct pathway of recognition of allogenic major histocompatibility molecules (with or without an associated endogenous peptide), or by an indirect pathway of recognition of processed donor alloantigens via recipient antigen presenting cells. Afferent immunity on the musculoskeletal system is of special interest because of the absence of viable donor antigen presenting cells in processed grafts that makes them susceptible to the indirect pathway of alloantigen recognition.

An overview of neuroimmunomodulation and a possible correlation with musculoskeletal system function

There is an increasing body of evidence that the nervous system is capable of modulating the immune response. Receptors for neuromodulators and neurohormones have been found on human T lymphocytes. Activation of these receptors can be stimulatory or inhibitory depending on the neuroactive substance. The immune system may be able to communicate with the nervous system using neuromodulators and neurohormones secreted by lymphocytes. Sympathetic innervation of lymphoid tissues is not restricted to blood vessels and smooth muscle, but directly supplies lymphocytes and blood precursor cells. It is theorized that spinal fixations may adversely affect the immune response through somatosympathetic reflexes. Spinal manipulation can correct the spinal fixations and may eliminate the adverse affects of somatosympathetic reflexes.