Among the possible cellular therapies to replace insulin secretion in diabetes, bone marrow-derived stem cells have aroused interest because of their plasticity and ease of procurement. Indeed, some experimental reports suggest that the bone marrow harbours cells capable of differentiation into beta cells [1–3], the transplantation of which can correct hyperglycaemia [1, 4]. However, these findings have not been corroborated in other studies . Nonetheless, the experimental data are not conclusive and point to three potential roles of bone marrow cells in the treatment of diabetes, namely as a source of stem cells for beta cells, as a facilitator of beta cell regeneration and as an immune modulator.
The infusion of autologous bone marrow was recently reported to restore insulin secretion in type 1 diabetes . To reproduce these results, we evaluated the effect of an intrapancreatic infusion of autologous bone marrow blood on insulin production in patients with type 1 diabetes.
The present pilot study was designed to include ten patients with type 1 diabetes of more than 5 years duration and the following characteristics: inadequate glycaemic control (HbA1c >8.5% or recurrent hypoglycaemia) with intensified insulin treatment; free C-peptide <0.033 nmol/l (basal and 6 min after administration of 1 mg glucagon, as measured with GlucaGen, Novo Nordisk, Gentofte, Denmark). Patients gave informed consent and the study protocol was approved by the Research Ethics Committee of the Hospital Clinic of Barcelona.
This study suggests that intrapancreatic autologous bone marrow infusion has no effect on insulin secretion in patients with type 1 diabetes. We decided to use total bone marrow cells rather than CD34+ purified cells in order to reproduce the previous report exactly  and because of the current lack of information on the efficiency of these two options.
Based on our experience and on the inconsistency of the previous information, we believe that intrapancreatic autologous bone marrow transplantation does not induce any relevant effect on beta cell function in type 1 diabetes patients with undetectable C-peptide levels. Our data, obviously, cannot rule out the possibility that bone marrow transplantation could be effective in preserving or even restoring beta cell function in recently diagnosed type 1 diabetes patients. However, a recent report, in which autologous umbilical cord blood infusion failed to preserve C-peptide levels in young newly diagnosed children 1 year after infusion, does not support this hypothesis .