Bone marrow harvesting from paediatric patients undergoing haematopoietic stem cell gene therapy

Abstract

Collection of an adequate amount of autologous hematopoietic stem progenitor cells (HSPC) is required for ex vivo manipulation and successful engraftment for certain inherited disorders. Fifty-seven paediatric patients (age 0.5-11.4 years) underwent a bone marrow harvest for the purpose of HSPC gene therapy (GT), including adenosine deaminase severe combined immunodeficiency (ADA-SCID), Wiskott Aldrich syndrome (WAS) and metachromatic leukodystrophy (MLD) patients. Total nucleated cells and percentage and absolute counts of CD34+ cells were calculated at defined steps of the procedure (harvest, CD34+ cell purification, transduction with the gene transfer vector and infusion of the medicinal product). Minimum CD34+ cell dose for infusion was 2x106/kg, with optimal target at 5-10x106/kg. Median volume of bone marrow harvested was 34.2 ml/kg (range 14.2-56.6). The number of CD34+ cells collected correlated inversely with weight and age in all patients and particularly in the MLD children group. All patients reached the minimum target dose for infusion: median dose of CD34+ cells/kg infused was 10.3 x106/kg (3.7-25.9), with no difference among the 3 groups. Bone marrow harvest of volumes >30 ml/kg in infants and children with ADA-SCID, WAS and MLD is well tolerated and allows obtaining an adequate dose of medicinal product for HSPC-GT.

Donor characteristics and intraoperative total nucleated cell count influence hematopoietic progenitor cell yield of healthy donor bone marrow grafts

“…However, in their cohort, donor weight positively correlated with marrow harvest TNC cell density, contrary to our findings. In a study evaluating marrow harvest characteristics from children undergoing autologous marrow collections in preparation for gene therapy, Tucci et al reported similar findings to our cohort, with final graft CD34+ cell count correlating inversely with weight and age, 13 the latter of which was also seen in a report of the effect of G‐CSF priming on marrow cell counts 11 …”

Pannexin-1 channel “fuels” by releasing ATP from bone marrow cells a state of sterile inflammation required for optimal mobilization and homing of hematopoietic stem cells

“…of harvested HSPCs after mobilization as well as to enhance their "seeding efficiency" after transplantation into hematopoietic BM niches [3].…”

“…In subsequent years, two other important sources of HSPCs emerged that are mobilized peripheral blood (PB) and umbilical cord blood (UCB). With all these sources of cells, very often, a number of HSPCs that are present in harvested BM, mobilized PB, or UCB unit are limited [ 1 – 3 ]. In humans, a successful transplantation requires a sufficient number of harvested HSPCs per kg body weight of the patient, and a fast, consistent, and long-term multilineage engraftment requires the intravenous infusion of a minimum of 2 × 10 6 CD34 + stem cells/kg recipient body weight; however, a higher dose of 5 × 10 6 CD34 + cells/kg is considered preferable.…”

“…In humans, a successful transplantation requires a sufficient number of harvested HSPCs per kg body weight of the patient, and a fast, consistent, and long-term multilineage engraftment requires the intravenous infusion of a minimum of 2 × 10 6 CD34 + stem cells/kg recipient body weight; however, a higher dose of 5 × 10 6 CD34 + cells/kg is considered preferable. Therefore, novel strategies are needed to increase a number of harvested HSPCs after mobilization as well as to enhance their “seeding efficiency” after transplantation into hematopoietic BM niches [ 3 ].…”

A Review of Infections After Hematopoietic Cell Transplantation Requiring PICU Care: Transplant Timeline Is Key

“…Donor stem cells are collected directly from the BM space in a procedure called a BM harvest ( 35 ). They may also be collected via peripheral blood after the donor is given a stem cell mobilizing agent to move stem cells into the periphery for collection ( 36 ).…”