After HRP was injected into the cervical, thoracic, lumbar and sacral segments of the spinal cord of the rat, the spinal projections of the locus coeruleus were studied by means of fluorescence histochemistry. The NAergic fibers arising from the locus coeruleus (LC) projected to the various levels of the spinal cord, and the topographical organization was observed, the neurons of the LC-spinal projections were located predominantly in the ventral part of the LC, but a few cells were also found in the dorsal part which projected to the cervical cord. The neurons projecting to the cervical cord from the LC were mainly located in the caudal part of the LC and the neurons projecting to the sacral cord were mainly located in the rostral part of the LC, but some overlapping existed.

Hematopoietic stem cell (HSC) transplantation is the only curative therapy for many diseases. HSCs from umbilical cord blood (UCB) source have many advantages over from bone marrow. However, limited HSC dose in a single CB unit restrict its widespread use. Over the past two decades, ex vivo HSC expansion with small molecules has been an effective approach for obtaining adequate HSCs. Till now, several small-molecule compounds have entered the phase I/II trials, showing safe and favorable pharmacological profiles. As HSC expansion has become a hot topic over recent years, many newly identified small molecules along with novel biological mechanisms for HSC expansion would help solve this challenging issue. Here, we will give an overview of HSC biology, discovery and medicinal chemistry development of small molecules, natural products targeting for HSC expansion, and their recent clinical progresses, as well as potential protein targets for HSC expansion.