The effect of human cord blood on SJL/J mice after chemoablation and irradiation and its possible clinical significance

Human umbilical-cord-blood mononucleated cells enhance the survival of lethally irradiated mice: dosage and the window of time

The purpose of this study was to evaluate the window of time and dose of human umbilical-cord-blood (HUCB) mononucleated cells necessary for successful treatment of radiation injury in mice. Female A/J mice (27-30 weeks old) were exposed to an absorbed dose of 9-10 Gy of (137)Cs γ-rays delivered acutely to the whole body. They were treated either with 1 × 10(8) or 2 × 10(8) HUCB mononucleated cells at 24-52 h after the irradiation. The antibiotic Levaquin was applied 4 h postirradiation. The increased dose of cord-blood cells resulted in enhanced survival. The enhancement of survival in animals that received 2 × 10(8) HUCB mononucleated cells relative to irradiated but untreated animals was highly significant (P < 0.01). Compared with earlier studies, the increased dose of HUCB mononucleated cells, coupled with early use of an antibiotic, extended the window of time for effective treatment of severe radiation injury from 4 to 24-52 h after exposure.

Endogenous hematopoietic reconstitution induced by human umbilical cord blood cells in immunocompromised mice: implications for adoptive therapy

Human umbilical cord blood (HUCB) cells show promising advantages over bone marrow (BM) cells for a variety of diseases that require transplantation. We observed that lethally irradiated SJL/J mice given a single injection of HUCB cells survive, whereas vehicle-injected mice do not. Because survival is not due to long-term engraftment of HUCB cells, we used this HUCB/mouse model to investigate additional therapeutic benefits of HUCB cells. We investigated the mechanism by which HUCB cells accelerated endogenous hematopoiesis in mice that received either lethal (9.5 Gy) or lower-dose (8.0 Gy) radiation and then were given a single injection of HUCB mononuclear cells. Compared to irradiated control mice, the lethally irradiated, HUCB-injected group showed significant increases in peripheral white blood cell counts, red blood cell indices, and granulocyte-macrophage colony-forming units (CFU-GM) by 3 weeks. In contrast, no significant differences in these parameters were observed between control and HUCB-injected mice that received the lower dose of irradiation. Moreover, regardless of the radiation dose, only HUCB-injected mice exhibited immune responses comparable to those of age-matched normal mice. The clinical relevance of these observations was determined in long-term, culture-initiating cell assays with human BM stem cells and irradiated (gamma-) HUCB cells. CFU-GM colonies were detectable in cultures containing gamma-HUCB cells by day 15, but were undetectable in cultures without gamma-HUCB cells until day 40, suggesting a hematopoietic stimulatory role for HUCB cells. Overall, the results indicate that in addition to their use for transplantation, HUCB cells also may be used as an adjuvant therapy to enhance hematopoietic reconstitution and immunocompetence of the host. This hematopoiesis-enhancing effect represents a heretofore unrecognized function of HUCB cells.

Potential for clinical use of viable pluripotent progenitor cells in blood bank stored human umbilical cord blood

There are indications that a close HLA match may not be necessary when human umbilical cord blood (HUCB) is used to effect a hematopoietic transplant. This was first suggested in 1972 and was further supported by the ability of HUCB to produce mouse survival following lethal irradiation. In China multiple units of HLA unmatched HUCB was utilized successfully in children to effect transplants. A recent publication indicated that newborn rodent blood cells can engraft in adult mice across the non-H-2 [corrected] antigens. Furthermore, there recently have been successful transplants with 3 antigens mismatched HUCB. In this study HUCB was stored in polyolefin blood bank bags at 4 degrees C. The storage was similar to that used in routine blood banking. Clonogenic assays were performed at Day 1 and 21 utilizing various growth factors. Replating efficiency was determined on colonies obtained from cord blood that was stored (non-frozen) for 21 days. The functional ability of day 21 old HUCB was determined by its ability to produce survival of lethally irradiated mice. It was found that approximately two-thirds (62.5%) of single primary blast cell colonies in day 21 stored HUCB could generate various types of secondary colonies. In some instances the secondary colonies were counted as high as 42 total mean colonies per single primary colony. These blast cell colonies (CFU-BL) were able to form single and multi lineage colonies composed of virtually every hematopoietic cell types. Animal survival studies were utilized in an effort to determine possible functional ability and were successful in producing fifty-day survival in 54% of lethally irradiated SJL/J mice and 100% ALB/C mice. This study holds the potential of making HUCB available for purposes of marrow transplantation to all who need it. It could further remove most of the moral and ethical issues related to HUCB, reduce to a fraction the cost in providing stem cells for marrow transplantation and potentially allow HUCB to be handled by existing blood banks.

Potential effectiveness of stored cord blood (non-frozen) for emergency use

Bone marrow has been used for a number of years to assist patients who have accidentally received potentially lethal levels of irradiation. The intent of the transplant is to replace the victim's own bone marrow that has been injured from the irradiation or to act as temporary support to allow the patient's own marrow to recover. Following the Chernobyl disaster, some victims received bone marrow that was HLA matched or partially matched. However, donor marrows were difficult to obtain in adequate numbers; as a substitute for bone marrow, frozen fetal liver cells were used as a source of hematopoietic stem cells. The use of fetal livers, however, was unsuccessful. Human umbilical cord blood, currently considered an excellent source of hematopoietic stem cells, was not used at Chernobyl. For several years, we have been able experimentally to keep SJL/J mice alive with the use of human umbilical cord blood after the animals received lethal levels of irradiation. This finding suggests that under certain conditions human cord blood does not have to be HLA matched to facilitate rescue from irradiation. In addition, there are reports of unmatched HLA cord blood being used successfully for marrow transplantation. If human cord blood does not have to be matched for HLA, there may be emergency cataclysmic circumstances where the availability of umbilical cord blood may be of considerable value. To simulate a clinical situation such as a nuclear accident, in which human cord blood might serve as a source of stem cells for marrow transplantation, we attempted to rescue immunocompetent mice after 900 cGY of irradiation with the use of (nonfrozen) human cord blood stored in a blood bank. The blood was stored under routine conditions (3-6 degrees C) for 5 and 7 days in special bags that allow transmission of oxygen. Following lethal levels of irradiation, the cord blood was administered to the animals and a significant survival rate was obtained.