Cryopreserved human bone marrow stroma is fully functional in vitro

Human marrow long-term culture (LTC) enables maintenance of both stromal and haemopoietic elements of normal bone marrow (NBM) in vitro for 4-6 months. Stroma-based cultures are critical for quantitation of long-term culture initiating cells (LTC-IC), the most primitive human haemopoietic cells measurable in vitro. Supply of NBM can be sporadic, and up to 3-4 weeks in culture is required for stromal maturity. Stroma availability for experimental purposes can therefore be limited. Efforts to produce transformed human and transfected murine stromal cell lines comparable to NBM stroma have had some success. As an alternative, we investigated cryopreserved NBM and cryopreserved preformed stroma. Function of cryopreserved and control fresh NBM stroma was similar when evaluated for up to 12 weeks in LTC. We have also demonstrated that stroma derived from cryopreserved NBM or preformed cryopreserved NBM stroma can sustain third-party haemopoiesis as efficiently as fresh NBM stroma in LTC. Batched cryopreserved stroma is a convenient, rapidly available, source of functional stroma which avoids the logistic difficulties and lack of standardization associated with stroma from fresh NBM. This important advance will enhance the use of stroma-based LTC in studies of human haemopoiesis