Microencapsulation of parathyroid tissue with photosensitive poly(L-lysine) and short chain alginate-co-MPEG

Hypoparathyroidism: State of the Art on Cell and Tissue Therapies

Hypoparathyroidism is an endocrine disorder characterized by low serum calcium levels, high serum phosphorus levels, and by inappropriate or absent secretion of the parathyroid hormone (PTH). The most common therapeutic strategy to treat this condition is hormone replacement therapy with calcium and vitamin D but, unfortunately, in the long term this treatment may not be sufficient to compensate for the loss of endocrine function. Glandular autotransplantation is considered the most effective technique in place of replacement therapy. Although it leads to excellent results in most cases, autotransplantation is not always possible. Allograft is a good way to treat patients who have not been able to undergo autograft, but this technique has limited success due to side effects related to tissue rejection. This therapy is supported by systemic immunosuppression, which leads to the onset of serious side effects in patients, with a risk of endocrine toxicity. Today, research on endocrine disorders is focused on discovering alternative graft therapies that can allow optimal results with the fewest possible side effects. In this review, we will make an update on the current state of the art about the cell and tissue therapy as treatment for hypoparathyroidism, to identify which type of therapeutic strategy could be valid for a future clinical use.

Tissue-engineered parathyroid gland and its regulatory secretion of parathyroid hormone

Parathyroid glands (PTGs) are important endocrine organs being mainly responsible for the secretion of parathyroid hormone (PTH) to regulate the balance of calcium (Ca) /phosphorus (P) ions in the body. Once PTGs get injured or removed, their resulting defect or loss of PTH secretion should disturb the level of Ca/P in blood, thus damaging other related organs (bone, kidney, etc.) and even causing death. Recently, tissue-engineered PTGs (TE-PTGs) have attracted lots of attention as a potential treatment for the related diseases of PTGs caused by hypoparathyroidism and hyperparathyroidism, including tetany, muscle cramp, nephrolithiasis, nephrocalcinosis, and osteoporosis. Although great progress has been made in the establishment of TE-PTGs with an effective strategy to integrate the key factors of cells and biomaterials, its regulatory secretion of PTH to mimic its natural rhythms in the body remains a huge challenge. This review comprehensively describes an overview of PTGs from physiology and pathology to cytobiology and tissue engineering. The state of the arts in TE-PTGs and the feasible strategies to regulate PTH secretion behaviors are highlighted to provide an important foundation for further investigation.

Impact of Orally Administered Microcapsules on Gastrointestinal Microbial Flora: In-Vitro Investigation Using Computer Controlled Dynamic Human Gastrointestinal Model

Oral administration of artificial cell microcapsules has been proposed for various therapy procedures using biologically active materials. Recently we have designed novel APPPA microcapsules using alginate, poly-L-lysine, pectin, poly-L-lysine and alginate that have shown superior oral delivery features. This article investigates, in-vitro using a computer controlled dynamic gastrointestinal (GI) model, effects of APPPA microcapsules on health of gastrointestinal (GI) microbial flora. The impact of APPPA microcapsules on GI bacterial population, total anaerobes, total aerobes, Escherichia coli, Lactobacillus sp. and Staphylococcus sp. has been analyzed. In addition, the effects of microcapsules on GI microbial extracellular enzymatic activities have been investigated. Result shows the altered activities of microbial flora and enzymes due to the use of APPPA microcapsule. The most disparity is observed in the colon ascendans microbial activities. This study would have significant impact on future microcapsule design. However, further in-vivo studies are required.

Influence of alginate on type II collagen fibrillogenesis

Collagen II is the majority of extracellular matrix components in articular cartilage, which with the major functions of preventing expansion of the tissue and distributing the load of body weight. To obtain man-made ECM, the reconstitution of collagen could be conducted in the presence of negatively charged polysaccharide, such as alginate. Alginate is an anionic polysaccharide capable of eversible gelated in calcium ion solution to prepare different shapes of biomaterials. Its well-known biocompatibility makes it an ideal material in biomedical applications. Thus, the aim of this study was to evaluate the effects of alginate on the fibrillogenesis of type II collagen. The preliminary results revealed that inclusion of alginate into soluble type II collagen solution could inhibit the development of turbidity of collagen solution, and the apparent rate constants in lag and growth phases decreased during collagen formation period, both rate constants decreased to about one-third of the original constants, respectively. From TEM observations, the collagen fibrils were significantly thicker in 0.05% and 0.1% alginate as compared with pure collagen solution. Furthermore, the D-periods of collagen fibers kept unchanged significantly under all reconstituted conditions, which meant the packing of collagen monomer was probably not affected by adding these amounts of alginate.