A bone graft has been the gold standard treatment for repairing bone defects. However, due to bone grafts associated donor site morbidity several alternative bone substitutes options have been made available but with their added expense and limited osteoinductive properties they are not ideal. Therefore, research has begun in tissue engineering to investigate stem cells, which are one of the body’s own mechanisms used to repair bone. Stem cells are clonogenic undifferentiated cells capable of self-renewal. Readily available from numerous of sources stem cells have the potential to differentiate in osteoblasts and chrondrocytes showing capability to repair both bone and cartilage. The known immunologic properties of stem cells further enhance their therapeutic appeal. Stem cells have shown to be excellent carriers for gene transfer having the capability to be transduced. Gene transfer could enable growth factors and bone morphogentic proteins to enhance bone repair. Stem cells are implanted onto scaffolds, which are structures capable of supporting tissue formation by allowing cell migration, proliferation and differentiation. Research aims to produce scaffolds that deliver and retain cells, allow for cell attachment has adequate biodegradability, biocompatibility and non-immunogenicity. However, having tried and testing numerous materials including synthetic and natural products research into the perfect scaffold product continues. This review aims to explain how stem cells were discovered, the techniques used to isolate stem cells, identify and manipulate them down different cell lineages and discuss the research into using stem cells to reconstruct bone using genetic modification and scaffolds.

The applications of 3D bioprinting are becoming more commonplace. Since the advent of tissue engineering, bone has received much attention for the ability to engineer normal bone for tissue engraftment or replacement. While there are still debates on what materials comprise the most durable and natural replacement of normal tissue, little attention is given to recreating diseased states within the bone. With a better understanding of the cellular pathophysiology associated with the more common bone diseases, these diseases can be scaled down to a more throughput way to test therapies that can reverse the cellular pathophysiology. In this review, we will discuss the potential of 3D bioprinting of bone tissue in the following disease states: osteoporosis, Paget’s disease, heterotopic ossification, osteosarcoma, osteogenesis imperfecta, and rickets disease. The development of these 3D bioprinted models will allow for the advancement of novel therapy testing resulting in possible relief to these chronic diseases.

Background Pharmacological approaches that boost neuroprotective regulatory T cell (Treg) number and function lead to neuroprotective activities in neurodegenerative disorders. Objectives We investigated whether low-dose interleukin 2 (IL-2) expands Treg populations and protects nigrostriatal dopaminergic neurons in a model of Parkinson’s disease (PD). Methods IL-2 at 2.5 × 104 IU/dose/mouse was administered for 5 days. Lymphocytes were isolated and phenotype determined by flow cytometric analyses. To 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxicated mice, 0.5 × 106 of enriched IL-2-induced Tregs were adoptively transferred to assess the effects on nigrostriatal neuron survival. Results IL-2 increased frequencies of CD4+CD25+CD127lowFoxP3+ Tregs that express ICOS and CD39 in blood and spleen. Adoptive transfer of IL-2-induced Tregs to MPTP-treated recipients increased tyrosine hydroxylase (TH)+ nigral dopaminergic neuronal bodies by 51% and TH+ striatal termini by 52% compared to control MPTP-treated animal controls. Conclusions IL-2 expands numbers of neuroprotective Tregs providing a vehicle for neuroprotection of nigrostriatal dopaminergic neurons in a pre-clinical PD model.

Dysregulation of innate and adaptive immunity can lead to alpha-synuclein (α-syn) misfolding, aggregation, and post-translational modifications in Parkinson’s disease (PD). This process is driven by neuroinflammation and oxidative stress, which can contribute to the release of neurotoxic oligomers that facilitate dopaminergic neurodegeneration. Strategies that promote vaccines and antibodies target the clearance of misfolded, modified α-syn, while gene therapy approaches propose to deliver intracellular single chain nanobodies to mitigate α-syn misfolding, or to deliver neurotrophic factors that support neuronal viability in an otherwise neurotoxic environment. Additionally, transformative immune responses provide potential targets for PD therapeutics. Anti-inflammatory drugs represent one strategy that principally affects innate immunity. Considerable research efforts have focused on transforming the balance of pro-inflammatory effector T cells (Teffs) to favor regulatory T cell (Treg) activity, which aims to attenuate neuroinflammation and support reparative and neurotrophic homeostasis. This approach serves to control innate microglial neurotoxic activities and may facilitate clearance of α-syn aggregates accordingly. More recently, changes in the intestinal microbiome have been shown to alter the gut-immune-brain axis leading to suppressed leakage of bacterial products that can promote peripheral inflammation and α-syn misfolding. Together, each of the approaches serves to interdict chronic inflammation associated with disordered immunity and neurodegeneration. Herein, we examine research strategies aimed at improving clinical outcomes in PD.

Prodrugs are bioreversible drug derivatives which are metabolized into a pharmacologically active drug following chemical or enzymatic modification. This approach is designed to overcome several obstacles that are faced by the parent drug in physiological conditions that include rapid drug metabolism, poor solubility, permeability, and suboptimal pharmacokinetic and pharmacodynamic profiles. These suboptimal physicochemical features can lead to rapid drug elimination, systemic toxicities, and limited drug-targeting to disease-affected tissue. Improving upon these properties can be accomplished by a prodrug design that includes the careful choosing of the promoiety, the linker, the prodrug synthesis, and targeting decorations. We now provide an overview of recent developments and applications of prodrugs for treating neurodegenerative, inflammatory, and infectious diseases. Disease interplay reflects that microbial infections and consequent inflammation affects neurodegenerative diseases and vice versa, independent of aging. Given the high prevalence, personal, social, and economic burden of both infectious and neurodegenerative disorders, therapeutic improvements are immediately needed. Prodrugs are an important, and might be said a critical tool, in providing an avenue for effective drug therapy.