ProtheraCytes® is a fresh preparation of stem cells that has the potential for regeneration of various damaged tissues, including cardiac tissue. ProtheraCytes® is derived from CD34+ cells harvested from the peripheral blood of the patient after mobilization from the bone marrow, and the propietary expansion, purification, and formulation in a fresh cell suspension for injection.


1 Krause, DS et al. (1996), CD34: structure, biology, and clinical utility. Blood 87:1–13

2 Wojakowski et al. (2004), Mobilization of CD34/CXCR4+ […] Circulation, 110, 3213–3220
3 Asahara, T et al. (1997), Isolation of putative progenitor endothelial cells for angiogenesis. Science 275:964–967

Characteristics and potential of CD34+ stem cells

CD34+ stem cells are mainly located in the bone marrow and can be easily mobilized into the peripheral blood2. It has been shown that within the first week after acute myocardial infarction (AMI), endogenous CD34+ cells are mobilized in increased numbers from the bone marrow into the peripheral blood. Animal studies have shown that these spontaneously mobilized CD34+ cells migrate to the damaged heart and are retained around the scar where they limit stiffness and enhance post-AMI remodelling3. But their number is not high enough to compensate the loss of billions of infarcted cardiomyocytes. Thus, to achieve such a goal, it is necessary to very consistently increase the number of potentially active cells.


CellProthera has developed a unique GMP-compliant cell expansion process as well as a proprietary automation technology for in vitro proliferation of CD34+ stem cells. The final cell product, labelled as ProtheraCytes®, has the potential for regeneration of various damaged tissues, including cardiac tissue. ProtheraCytes® is registered as an ATMP – Advanced Therapy Medicinal Product – within the classification of Tissue Engineered product by the European Medicine Agency (EMA).

The underlying cardiac-repair mechanisms of ProtheraCytes® are multifaceted, combining a cell differentiation process and a paracrine effect.


The post-AMI inflammatory scar first secretes cardioactive chemokines that

      1. chemoattract transplanted CD34+ stem cells to home in the ischemic zone and
      2. induce in-situ their proliferation and differentiation, promoting cardiac tissue repair, while
      3. activated CD34+ stem cells then release soluble paracrine factors and exosomes that can both enhance the proliferation of resident cardiomyocytes to reduce fibrosis and attenuate remodelling, and support angiogenesis, i.e. the revascularization of the repaired tissue.


StemXpand® V2 prototype with 5 incubators capable of manufacturing 5 patient therapies simultaneously.


CellProthera has chosen early on to invest in the development of an automation technology to guarantee a consistent level of quality across multiple production sites, for each patient and at an affordable price. Leading a consortium of five industrial partners and a research institute, together with the support of BPI France, CellProthera has developed a technology platform comprising of an automated device StemXpand® and a single-use kit StemPack®, compliant with GMP guidelines.