Bone Marrow Transplantation Procedures in Mice to Study Clonal Hematopoiesis

Summary

We describe three methods of bone marrow transplantation (BMT): BMT with total-body irradiation, BMT with shielded irradiation, and BMT method with no pre-conditioning (adoptive BMT) for the study of clonal hematopoiesis in mouse models.

Abstract

Clonal hematopoiesis is a prevalent age-associated condition that results from the accumulation of somatic mutations in hematopoietic stem and progenitor cells (HSPCs). Mutations in driver genes, that confer cellular fitness, can lead to the development of expanding HSPC clones that increasingly give rise to progeny leukocytes harboring the somatic mutation. Because clonal hematopoiesis has been associated with heart disease, stroke, and mortality, the development of experimental systems that model these processes is key to understanding the mechanisms that underly this new risk factor. Bone marrow transplantation procedures involving myeloablative conditioning in mice, such as total-body irradiation (TBI), are commonly employed to study the role of immune cells in cardiovascular diseases. However, simultaneous damage to the bone marrow niche and other sites of interest, such as the heart and brain, is unavoidable with these procedures. Thus, our lab has developed two alternative methods to minimize or avoid possible side effects caused by TBI: 1) bone marrow transplantation with irradiation shielding and 2) adoptive BMT to non-conditioned mice. In shielded organs, the local environment is preserved allowing for the analysis of clonal hematopoiesis while the function of resident immune cells is unperturbed. In contrast, the adoptive BMT to non-conditioned mice has the additional advantage that both the local environments of the organs and the hematopoietic niche are preserved. Here, we compare three different hematopoietic cell reconstitution approaches and discuss their strengths and limitations for studies of clonal hematopoiesis in cardiovascular disease.

Introduction

Clonal hematopoiesis (CH) is a condition which is frequently observed in elderly individuals and occurs as a result of an expanded hematopoietic stem and progenitor cell (HSPC) clone carrying a genetic mutation¹. It has been suggested that by the age of 50, most individuals will have acquired an average of five exonic mutations in each HSPC², but most of these mutations will result in little or no phenotypic consequences to the individual. However, if by chance one of these mutations confers a competitive advantage to the HSPC—such as by promoting it’s proliferation, self-renewal, survival, or some combinatio....

Protocol

All procedures involving animal subjects have been approved by the Institutional Animal Care and Use Committee (IACUC) at the University of Virginia.

1. Prior to preconditioning

1. Place the recipient mice on antibiotic-supplemented water (5 mM sulfamethoxazole, 0.86 mM trimethoprim) ~24 h prior to irradiation. This is necessary to prevent infection, as the immune system will be suppressed following irradiation, and maintained for 2 weeks following irradiation. At this point, supplement mice with a nutritional/hydration gel to encourage feeding and to prevent weight loss and dehydration after irradiation.

Results

To compare the effect of three BMT/pre-conditioning methods on donor cell engraftment, the fractions of donor cells in peripheral blood and heart tissue were analyzed by flow cytometry at 1-month post-BMT. Isolated cells were stained for specific leukocyte markers to identify the different subsets of leukocytes. In these experiments, wild-type (WT) C57BL/6 (CD45.2) donor bone marrow cells were delivered to WT B6.SJL-Ptprc^aPrpc^b/BoyJ (CD45.1) reci.......

Discussion

For studies of clonal hematopoiesis, we described three methods of BMT: BMT with total-body irradiation, BMT with irradiation with partial shielding, and a less commonly used BMT method that involves no pre-conditioning (adoptive BMT). These methods have been used to assess the impact of clonal hematopoiesis on cardiovascular disease. Researchers can modify these methods accordingly to suit the specific purpose of their study.

Clonal hematopoiesis models
Clonal hematopoi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.5ml microcentrifuge	Fisher Scientific	05-408-121	general supply
1.5ml microcentrifuge	Fisher Scientific	05-408-129	general supply
1/2 cc LO-DOSE INSULIN SYRINGE	EXELINT	26028	general supply
Absolute Ethanol (200 prfof)	Fisher chemical	200559	general supply
BD 1mL Tuberculin Syringes 25G 5/8 Inch Needle	Becton Dickinson	309626	general supply
BD PrecisionGlide Needle 18G (1.22mm X 25mm)	Becton Dickinson	395195	general supply
Cesium-137 Irradiator	J. L. Shepherd	Mark IV	equipment
DietGel 76A	Clear H2O	70-01-5022	general supply
Falcon 100 mm TC-Treated Cell Culture Dish	Life Sciences	353003	general supply
Falcon 50 mL Conical Centrifuge Tubes	Fisher Scientific	352098	general supply
Fisherbrand sterile cell strainers, 70 μm	Fisher Scientific	22363548	general supply
Graefe Forceps	Fine Science Tools	11051-10	general supply
Hardened Fine Scissors	Fine Science Tools	14090-09	general supply
Isothesia (Isoflurane) solution	Henry Schein	29404	Solution
Ketamine	Zoetis	043-304	injection
Kimwipes Delicate Task Wipers	Kimtech Science	KCC34155	general supply
PBS pH7.4 (1X)	Gibco	10010023	Solution
RadDisk – Rodent Irradiator Disk	Braintree Scientific	IRD-P M	general supply
RPMI Medium 1640 (1X)	Gibco	11875-093	Medium
Sulfamethoxazole and Trimethoprim	TEVA	0703-9526-01	injection
Xylazine	Akorn	139-236	injection
X-ray irradiator	Rad source	RS-2000	equipment