Osteopetrosis in the Grüneberg (mi) mouse can be cured by cultured allogeneic bone marrow

Early treatment of osteopetrosis: Paradigm shift to marrow cell transplantation

The osteopetroses reflect alterations of a special cell type, the osteoclast, belonging to the myeloid lineage. We have known this since the 1970s, confirmed by a myriad of reports featuring details that guided subsequent molecular diagnosis and treatment. This review is a tribute to two pioneers in the field: Donald G. Walker PhD (1925-1979) and Sandy C. Marks Jr. PhD (1937-2002), who explored osteopetrosis pathophysiology and treatment. Using spontaneous mutant models of osteopetrosis in mice, rats, and rabbits, they demonstrated the cellular basis of osteopetrosis while also advancing understanding of the hematological origin of osteoclasts. This became the foundation for life-saving treatment by hematopoietic stem cell transplantation. Their prose was uncomplicated, experiments were straightforward, and conclusions were based on facts explaining why their teaching became influential worldwide. I never met Dr. Walker but spoke with Dr. Marks on several occasions. Both inspired my work and, now appreciating how they shaped the osteoclast/osteopetrosis scientist community, we must thank these eminent scientists for being mentors of all of us.

Evidence for osteoclast production in mixed bone cell culture

Osteoclastlike cells (OLCs) were recognized by their morphological, histochemical, and behavioral characteristics. These characteristics were initially observed in freshly isolated osteoclasts when neonatal rat bone cells were introduced into culture. Epithelioid cells proliferated during the first week to form a confluent layer. The cells' alkaline phosphatase content and ability to produce elevated levels of cyclic adenosine monophosphate in response to parathyroid hormone (PTH) led us to tentatively describe them as osteoblastlike cells. When a second addition of neonatal bone cells was made onto this confluent layer, OLCs were produced, their numbers increasing to a maximum 7 days later and dying out 3 weeks later. Mononuclear cells with similar characteristics to these multinuclear OLCs were observed and their production and disappearance closely paralleled that of the OLCs. Fusion of OLCs was observed. The conditions under which OLCs were produced are described.