Cord blood banking and mesenchymal stem cell banking: А complementary approach in regenerative medecine

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The use of cord blood as a stem cell source is widespread known for the treatment of pediatric and haematological malignancies. Banking of cord blood is the logical consequence. Since 2000 the autologous use of cord blood is also documented in some clinical cases as there are stroke, limb ischemia, myocard regeneration. Regenerative cells in cord blood such as haematopoetic stem cells, endothelial progenitors are abundant and autologous cell therapy may result in effective off the shelf products for therapeutic applications.

The strong haematopoetic capacity of cord blood derived CD34 cells is due to the fact that cord blood is a much more immature source of stem cells compared to adult sources (bone marrow).

Mesenchymal cells (MSC) in cord blood are less frequent, but this type of cells can differentiate into various non haematopoetic tissues. A fetal source of non haematopoetic stem cells can be find in umbilical cord and placenta formation: it is a possible explanantion that these cells are from fetal origin; it comes from the fetal circulation. The human UC is embryologically derived at day 26 of gestation, and it grows to form a 30- to 50-cm-long helical organ at birth. During the 40 weeks of gestation, there must be a mesenchymal precursor cell population within the UC that gives rise to the WJ connective tissue. This Wharton's jelly of the umbilical cord contains mucoid connective tissue and fibroblast-like cells. Using flow cytometric analysis, it is found that mesenchymal cells isolated from the umbilical cord express matrix receptors (CD44, CD105) and integrin markers (CD29, CD51) but not haematopoietic lineage markers (CD34, CD45). Interestingly, these cells also express significant amounts of mesenchymal stem cell markers (SH2, SH3). Many researchers also showed that these cells have multilineage potential and that, under suitable culture conditions, are able to differentiate into cells of the adipogenic and osteogenic lineages.

Other sources for MSC than bone marrow are adipose tissue, synovium, muscles, lung, peridonts and umbilical cord (perivasular) cells from the Wharton Jelly. The kinetics of these last has been studied.

Long-term growth kinetics

Primary culture from Wharton Jelly were plated: the total cell count of harvested cells from primary culture after different passages was calculated. The mean number of harvested MSC are counted the average number of cells that proliferate during each passage and the average confluency time in the various passages are different. To examine long-term growth kinetics of MSC culture isolated from fresh cords, we measured (cumulative) population doublings (PDs), with respect to the passage number and time in multiple donors of umbilical cords (Fig. 1).

Post cryopreservation MSC culturing of umbilical cord tissue

When cord tissue is preserved and thawed later, the results give a similar picture as fresh material but with a delay in the growth curve due to cryopreservation (Figure 2). The characterisation of the cells after cryopreservation based on most MSC markers (flow cytometrie) was the same as before. This confirms that the cryopreservation protocol can be used for temporary storage of MSC.

Conclusions

Mesenchymal and haematopoetic cells play an important role in new developments in cellular therapeutics. Banking of both types of stem cells should still be optimized to increased

the number of viable well characterisezed cells. The EU project from the 6th Framework focuses on optimal cryopreservation protocols for different stem cells. An adapted protocol for each celline will be provided by the consortium.

About the authors

G. Wouters

Author for correspondence.
Email: redaktor@celltranspl.ru
Belgium

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