Assessment of microchimerism in rat liver transplantation by polymerase chain reaction

Polytherapy with a combination of three repurposed drugs (PXT3003) down-regulates Pmp22 over-expression and improves myelination, axonal and functional parameters in models of CMT1A neuropathy

Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common inherited sensory and motor peripheral neuropathy. It is caused by PMP22 overexpression which leads to defects of peripheral myelination, loss of long axons, and progressive impairment then disability. There is no treatment available despite observations that monotherapeutic interventions slow progression in rodent models. We thus hypothesized that a polytherapeutic approach using several drugs, previously approved for other diseases, could be beneficial by simultaneously targeting PMP22 and pathways important for myelination and axonal integrity. A combination of drugs for CMT1A polytherapy was chosen from a group of authorised drugs for unrelated diseases using a systems biology approach, followed by pharmacological safety considerations. Testing and proof of synergism of these drugs were performed in a co-culture model of DRG neurons and Schwann cells derived from a Pmp22 transgenic rat model of CMT1A. Their ability to lower Pmp22 mRNA in Schwann cells relative to house-keeping genes or to a second myelin transcript (Mpz) was assessed in a clonal cell line expressing these genes. Finally in vivo efficacy of the combination was tested in two models: CMT1A transgenic rats, and mice that recover from a nerve crush injury, a model to assess neuroprotection and regeneration. Combination of (RS)-baclofen, naltrexone hydrochloride and D-sorbitol, termed PXT3003, improved myelination in the Pmp22 transgenic co-culture cellular model, and moderately down-regulated Pmp22 mRNA expression in Schwannoma cells. In both in vitro systems, the combination of drugs was revealed to possess synergistic effects, which provided the rationale for in vivo clinical testing of rodent models. In Pmp22 transgenic CMT1A rats, PXT3003 down-regulated the Pmp22 to Mpz mRNA ratio, improved myelination of small fibres, increased nerve conduction and ameliorated the clinical phenotype. PXT3003 also improved axonal regeneration and remyelination in the murine nerve crush model. Based on these observations in preclinical models, a clinical trial of PTX3003 in CMT1A, a neglected orphan disease, is warranted. If the efficacy of PTX3003 is confirmed, rational polytherapy based on novel combinations of existing non-toxic drugs with pleiotropic effects may represent a promising approach for rapid drug development.

A highly sensitive and accurate method to quantify absolute numbers of c-kit+ cardiac stem cells following transplantation in mice

Although transplantation of c-kit+ cardiac stem cells (CSCs) alleviates post-myocardial infarction left ventricular dysfunction, there are no reliable methods that enable measurement of the absolute number of CSCs that persist in the recipient heart. To overcome this limitation, we developed a highly sensitive and accurate method to quantify the absolute number of murine CSCs after transplantation. This method has two unique features: (1) real-time PCR-based detection of a novel male-specific, multiple-copy gene, Rbmy, which significantly increases the sensitivity of detection of male donor cells in a female recipient, and (2) an internal standard, which permits quantification of the absolute number of CSCs as well as the total number of cells in the recipient organ. Female C57BL/6 mice underwent coronary occlusion and reperfusion; 2 days later, 10(5) male mouse CSCs were injected intramyocardially. Tissues were analyzed by real-time PCR at serial time points. In the risk region, >75 % of CSCs present at 5 min were lost in the ensuing 24 h; only 7.6 ± 2.1 % of the CSCs present at 5 min could still be found at 7 days after transplantation and only 2.8 ± 0.5 % (i.e., 1,224 ± 230 cells/heart) at 35 days. Thus, even after direct intramyocardial injection, the total number of CSCs that remain in the murine heart is minimal (at 24 h, ~10 % of the cells injected; at 35 days, ~1 %). This new quantitative method of stem cell detection, which enables measurement of absolute cell number, should be useful to optimize cell-based therapies, not only for CSCs but also for other stem cells and other organs.