Salud ósea en pacientes sometidos a trasplante de precursores hematopoyéticos: un nuevo problema a considerar

Insights Into the Role of Vitamin D as a Biomarker in Stem Cell Transplantation

Vitamin D was discovered 100 years ago and since then multiple studies have consistently proved its effect on bone health and mineral metabolism. Further research has also explored its so-called "non-classical" biological effects, encompassing immune regulation and control of cell proliferation and differentiation. Vitamin D downregulates pro-inflammatory immune cells and subsequently their cytokine production, while enhancing the anti-inflammatory subsets, thus mediating inflammation and fostering a more tolerogenic environment. Its biological action is exerted through the vitamin D receptor, a nuclear receptor that mediates gene transcription and is expressed in most cells from the innate and adaptive immunity. Owing to its immune-modulatory properties, its role in cancer pathophysiology, hematology disorders and stem cell transplantation has also been investigated. Vitamin D deficiency causes immune imbalance and cytokine dysregulation, contributing to some autoimmune diseases. In the hematopoietic stem cell transplant setting this could lead to complications such as acute and chronic graft-versus-host disease, ultimately impacting transplant outcomes. Other factors have also been linked to this, including specific polymorphisms of the vitamin D receptor in both stem cell donors and recipients. Nevertheless, studies thus far have shown conflicting results and the use of vitamin D or its receptor as biomarkers has not been validated yet, therefore there are no evidence-based consensus guidelines to guide clinicians in their day-to-day practice. To gain more insight in this topic, we have reviewed the existent literature and gathered the current evidence. This is an overview of the role of serum vitamin D and its receptor as biomarkers for clinical outcomes in patients undergoing hematopoietic stem cell transplantation. Further prospective studies with larger cohorts are warranted to validate the viability of using serum vitamin D, and its receptor, as biomarkers in potential stem cell donors and patients, to identify those at risk of post-transplant complications and enable early therapeutic interventions.

Vitamin D: is it important in haematopoietic stem cell transplantation? A review

Vitamin D has effects on several body systems, from well-established role in bone metabolism to emerging effects on the immune system. Increasing evidence supports an immunomodulatory effect including inhibition of the pro-inflammatory lymphocyte subsets while enhancing their anti-inflammatory counterpart, in favour of a more tolerogenic status. Vitamin D deficiency is increasingly recognised in association with autoimmune and inflammatory diseases, also with evidence from the field of asthma where vitamin D supplementation may overcome steroid resistance. In the HSCT setting, vitamin D deficiency has been variably associated with increased complications, including graft-versus-host disease (GvHD), with a potential impact on survival outcomes. In this review we provide an overview and critical appraisal of the current literature of the role of vitamin D (and its deficiency) in relation to immunity in both allogeneic and autologous HSCT settings. We conclude that the evidence base is mixed, but a greater understanding of the role of vitamin D in relation to immune reconstitution following HSCT is warranted. Given its potential benefits, its inexpensive cost and favourable side effect profile, consideration of vitamin D levels and its supplementation could be easily incorporated into prospective studies in GvHD, including clinical trials of novel therapeutics, supportive care and biomarkers.