Regenerative medicine is a highly anticipated field with hopes to provide cures for previously uncurable diseases such as spinal cord injuries and retinal blindness. Most regenerative medical products use either autologous or allogeneic stem cells, which may or may not be genetically modified. The introduction of induced-pluripotent stem cells (iPSCs) has fueled research in the field, and several iPSC-derived cells/tissues are currently undergoing clinical trials. The cornea is one of the pioneering areas of regenerative medicine, and already four cell therapy products are approved for clinical use in Japan. There is one other government-approved cell therapy product approved in Europe, but none are approved in the USA at present. The cornea is transparent and avascular, making it unique as a target for stem cell therapy. This review discusses the unique properties of the cornea and ongoing research in the field.

Eosinophilic gastroenteritis (EGE) can occur throughout the gastrointestinal tract, from the stomach to the colon. Typical known symptoms are abdominal pain, nausea, vomiting, and diarrhea. In addition, lesions in the intestinal mucosa may cause weight loss, protein-losing enteropathy (PLE), and other problems. A 6-month-old girl with no previous medical history was brought to our hospital after an afebrile 1-min clonic seizure. Blood tests showed low concentrations of serum calcium and albumin. After the correction of hypocalcemia with gluconic acid, there was no recurrence of seizure. Technetium-99m scintigraphy showed slight leakage of protein from the intestinal tract, which led us to conclude that the hypocalcemia and hypoalbuminemia were caused by PLE. Gastrointestinal endoscopy and biopsy performed to detect the cause of PLE revealed the presence of EGE. After starting administration of an amino acid-based formula, gastrointestinal symptoms of diarrhea or vomiting did not reappear. The serum albumin concentration normalized, and her weight gain improved. We report the first case of EGE in an infant who was diagnosed based on seizure. This case shows that infants with EGE may present with seizure resulting from hypocalcemia caused by PLE.

Angiogenesis, the development of new blood vessels, is a fundamental physiological process. In addition, angiogenesis plays a key role in the pathogenesis of several disorders, including cancer and eye disorders such as diabetic retinopathy and age-related macular degeneration (AMD). However, identifying the regulators of angiogenesis proved challenging. Numerous factors that stimulated angiogenesis in various bioassays were identified, but their pathophysiological role remained unclear. In 1989, we reported the isolation and cloning of vascular endothelial growth factor (VEGF, VEGF-A) as an endothelial cell-specific mitogen and angiogenic factor. The tyrosine kinases Flt-1 (VEGFR-1) and KDR (VEGFR-2) were subsequently identified as VEGF receptors. Loss of a single vegfa allele results in defective vascularization and embryonic lethality in mice, emphasizing the essential role of VEGF in the development of blood vessels. Subsequently, we reported that anti-VEGF monoclonal antibodies block growth and neovascularization in tumor models. These findings paved the way for the clinical development of a humanized anti-VEGF antibody and other VEGF inhibitors for cancer therapy. To date, several VEGF inhibitors represent standard of care for colorectal cancer and other difficult to treat malignancies. VEGF is also implicated in intraocular neovascularization associated with retinal disorders as well as neovascular AMD. Our group developed a humanized anti–VEGF-A antibody fragment (ranibizumab) for the treatment of wet AMD. Ranibizumab not only maintained but also improved visual acuity and has been approved worldwide for the treatment of wet AMD and other neovascular disorders. Other VEGF inhibitors, including bevacizumab and aflibercept, have also resulted in significant clinical benefits. Today anti-VEGF drugs represent the most effective therapy for intraocular neovascularization. Current research addresses the need to reduce the frequency of intravitreal injections as well the identification of additional pro-angiogenic pathways that could result in improving therapeutic outcomes.

The endoplasmic reticulum (ER), where newly synthesized secretory and transmembrane proteins are folded and assembled, has the ability to discriminate folded proteins from unfolded proteins and controls the quality of synthesized proteins. Only correctly folded molecules are allowed to move along the secretory pathway, whereas unfolded proteins are retained in the ER.

The ER contains a number of molecular chaperones and folding enzymes (ER chaperones hereafter), which assist productive folding of proteins, and therefore newly synthesized proteins usually gain correct tertiary and quaternary structures quite efficiently. Yet unfolded or misfolded proteins even after assistance of ER chaperones are retrotranslocated back to the cytosol, ubiquitinated and degraded by the proteasome. This disposal system is called ER-associated degradation (ERAD). Thus, the quality of proteins in the ER is ensured by two distinct mechanisms, productive folding and ERAD, which have opposite directions.

Under a variety of conditions collectively termed ER stress, however, unfolded or misfolded proteins accumulate in the ER, which in turn activates ER stress response or Unfolded Protein Response (UPR). The UPR is mediated by transmembrane proteins in the ER, and three ER stress sensors/transducers, namely IRE1, PERK and ATF6, operates ubiquitously in mammals. Thanks to these signaling pathways, translation is generally attenuated to decrease the burden on the folding machinery; transcription of ER chaperones is induced to augment folding capacity; and transcription of components of ERAD machinery is induced to enhance degradation capacity, leading to maintenance of the homeostasis of the ER. If ER stress sustains, cells undergo to apoptosis.

I will talk on the mechanism, evolution, and physiological importance of the UPR and ERAD as well as its involvement in development and progression of various diseases.